 |
Alessandro BIGI
Professore Associato
Dipartimento di Ingegneria "Enzo Ferrari"
|
Home |
Curriculum(pdf) |
Didattica |
Pubblicazioni
2024
- A new software toolkit for optical apportionment of carbonaceous aerosol
[Articolo su rivista]
Isolabella, Tommaso; Bernardoni, Vera; Bigi, Alessandro; Brunoldi, Marco; Mazzei, Federico; Parodi, Franco; Prati, Paolo; Vernocchi, Virginia; Massabò, Dario
abstract
Instruments measuring aerosol light absorption, such as the Aethalometer and the Multi-Wavelength Absorbance Analyzer (MWAA), have been extensively used to characterize optical absorption of atmospheric particulate matter. Data retrieved with such instruments can be analysed with mathematical models to apportion different aerosol sources (Aethalometer model) and components (MWAA model). In this work we present an upgrade to the MWAA optical apportionment model. In addition to the apportionment of the absorption coefficient b abs in its components (black carbon and brown carbon) and sources (fossil fuels and wood burning), the extended model allows for the retrieval of the absorption Ångström exponent of each component and source, thereby avoiding initial assumptions regarding these parameters. We also present a new open-source software toolkit, the MWAA model toolkit (MWAA_MT), written in both Python and R, that performs the entire apportionment procedure.
2024
- Measurement report: Source attribution and estimation of black carbon levels in an urban hotspot of the central Po Valley: An integrated approach combining high-resolution dispersion modelling and micro-aethalometers
[Articolo su rivista]
Veratti, Giorgio; Bigi, Alessandro; Stortini, Michele; Teggi, Sergio; Ghermandi, Grazia
abstract
Understanding black carbon (BC) levels and their sources in urban environments is of paramount importance due to their far-reaching health, climate and air quality implications. While several recent studies have assessed BC concentrations at specific fixed urban locations, there is a notable lack of knowledge in the existing literature on spatially resolved data alongside source estimation methods. This study aims to fill this gap by conducting a comprehensive investigation of BC levels and sources in Modena (Po Valley, Italy), which serves as a representative example of a medium-sized urban area in Europe. Using a combination of multi-wavelength micro-aethalometer measurements and a hybrid Eulerian-Lagrangian modelling system, we studied two consecutive winter seasons (February–March 2020 and December 2020–January 2021). Leveraging the multi-wavelength absorption analyser (MWAA) model, we differentiate sources (fossil fuel combustion, FF, and biomass burning, BB) and components (BC vs. brown carbon, BrC) from micro-aethalometer measurements. The analysis reveals consistent, minimal diurnal variability in BrC absorption, in contrast to FF-related sources, which exhibit distinctive diurnal peaks during rush hours, while BB sources show less diurnal variation. The city itself contributes significantly to BC concentrations (52 % ± 10 %), with BB and FF playing a prominent role (35 % ± 15 % and 9 % ± 4 %, respectively). Long-distance transport also influences BC concentrations, especially in the case of BB and FF emissions, with 28 % ± 1 % and 15 % ± 2 %, respectively. When analysing the traffic related concentrations, Euro 4 diesel passenger cars considerably contribute to the exhaust emissions. These results provide valuable insights for policy makers and urban planners to manage BC levels in medium-sized urban areas, taking into account local and long-distance sources.
2023
- A PM10 chemically characterised nation-wide dataset for Italy. Geographical influence on urban air pollution and source apportionment
[Articolo su rivista]
Pietrodangelo, Adriana; Bove, Maria Chiara; Forello, Alice Corina; Crova, Federica; Bigi, Alessandro; Brattich, Erika; Riccio, Angelo; Becagli, Silvia; Bertinetti, Stefano; Calzolai, Giulia; Canepari, Silvia; Cappelletti, David; Catrambone, Maria; Cesari, Daniela; Colombi, Cristina; Contini, Daniele; Cuccia, Eleonora; De Gennaro, Gianluigi; Genga, Alessandra; Ielpo, Pierina; Lucarelli, Franco; Malandrino, Mery; Masiol, Mauro; Massabò, Dario; Perrino, Cinzia; Prati, Paolo; Siciliano, Tiziana; Tositti, Laura; Venturini, Elisa; Vecchi, Roberta
abstract
: Urban textures of the Italian cities are peculiarly shaped by the local geography generating similarities among cities placed in different regions but comparable topographical districts. This suggested the following scientific question: can such different topographies generate significant differences on the PM10 chemical composition at Italian urban sites that share similar geography despite being in different regions? To investigate whether such communalities can be found and are applicable at Country-scale, we propose here a novel methodological approach. A dataset comprising season-averages of PM10 mass concentration and chemical composition data was built, covering the decade 2005-2016 and referring to urban sites only (21 cities). Statistical analyses, estimation of missing data, identification of latent clusters and source apportionment modelling by Positive Matrix Factorization (PMF) were performed on this unique dataset. The first original result is the demonstration that a dataset with atypical time resolution can be successfully exploited as an input matrix for PMF obtaining Country-scale representative chemical profiles, whose physical consistency has been assessed by different tests of modelling performance. Secondly, this dataset can be considered a reference repository of season averages of chemical species over the Italian territory and the chemical profiles obtained by PMF for urban Italian agglomerations could contribute to emission repositories. These findings indicate that our approach is powerful, and it could be further employed with datasets typically available in the air pollution monitoring networks.
2023
- Aerosol absorption using in situ filter-based photometers and ground-based sun photometry in the Po Valley urban atmosphere
[Articolo su rivista]
Bigi, Alessandro; Veratti, Giorgio; Andrews, Elisabeth; Collaud Coen, Martine; Guerrieri, Lorenzo; Bernardoni, Vera; Massabò, Dario; Ferrero, Luca; Teggi, Sergio; Ghermandi, Grazia
abstract
Light-absorbing aerosols (LAAs) are short-lived climate forcers with a significant impact on Earth’s radiative balance. LAAs include dust aerosols, black carbon (BC) and organic light-absorbing carbonaceous aerosol (collectively termed brown carbon, BrC), which have also been proven to be highly toxic. In this study, aerosol absorption at five wavelengths (ranging from ultraviolet to infrared) was monitored continuously using filter-based photometers during two winter seasons in 2020 and 2021 in the city of Modena (southern central Po Valley, northern Italy), at two regulatory air quality monitoring sites, along with other pollutants (coarse partic- ulate matter, PM 10; fine particulate matter, PM 2.5 ; O 3 ; NO; NO 2 ; and C 6 H 6 ) and the vehicular traffic rate. The aerosol optical depth (AOD) and other column aerosol optical properties were concurrently monitored at four wavelengths by an AErosol RObotic NETwork (AERONET) sun photometer under urban background conditions within Modena. In situ absorption levels were apportioned to both sources (fossil fuel and biomass burning) and species (BC and BrC), while columnar absorption was apportioned to BC, BrC and mineral dust. The combined analysis of the atmospheric aerosol and gas measurements and of the meteorological conditions (in situ and from the ERA5 reanalysis) identified the location of potential urban sources of BC and BrC, most likely related to traf- fic and biomass burning. In situ data show different diurnal/weekly patterns for BrC from biomass burning and BC from traffic, with minor differences between the background and the urban traffic conditions. AERONET version 3 absorption aerosol optical depth (AAOD) retrievals at four wavelengths allowed the estimation of the absorptive direct radiative effect due to LAAs over the same period under the reasonable assumption that the AOD signal is concentrated within the mixing layer. AERONET retrievals showed a modest correlation of columnar absorption with planetary boundary layer (PBL)-scaled in situ observations, although the correlation improved significantly during a desert dust transport event that affected both in situ aerosol and columnar ab- sorption, particularly in the blue spectrum range. A low correlation occurred between the contribution of BrC to aerosol absorption for the in situ and the columnar observations, with the BrC contribution being generally larger for in situ observations. Finally, evidence of a highly layered atmosphere during the study period, featur- ing significant spatial mixing and modest vertical mixing, was shown by ERA5-based atmospheric temperature profiles and by the large correlation of concurrent AERONET AOD retrievals in Modena and in Ispra (on the northwestern side of the Po Valley, ca. 225 km from Modena).
2023
- Evaluation of low-cost gas sensors to quantify intra-urban variability of atmospheric pollutants
[Articolo su rivista]
Baruah, Arunik; Zivan, Ohad; Bigi, Alessandro; Ghermandi, Grazia
abstract
Low-cost air quality monitoring units were tested within the context of the European research project TRAFAIR. This study aims to quantify the intra-urban variability of atmospheric pollutants by means of a low-cost sensor network, which was deployed across the urban area of Modena, in the Po Valley (Italy) for the assessment of air quality in the city. Each sensor unit featured a set of electrochemical cells responding to NO, NO 2 and O 3 delivering a current/voltage proportional to the mixing ratio of the target atmospheric pollutant. Each unit was calibrated using field colocation next to an urban regulatory air quality monitoring station in the city. A machine learning Random Forest algorithm was used as a calibration model and different configurations of the model were applied. The results from these configurations were compared in terms of their prediction performance and consistency of the explanatory variable role within the model. A significant variability in all pollutants across town was revealed by the units, highlighting areas impacted by local sources.
2023
- Photocatalytic-treated asphalt road in Copenhagen for urban NOx removal
[Articolo su rivista]
Dahl, Lilja; Jensen, Henrik; Bigi, Alessandro; Ghermandi, Grazia
abstract
2023
- Rapid growth and high cloud-forming potential of anthropogenic sulfate aerosol in a thermal power plant plume during COVID lockdown in India
[Articolo su rivista]
Singh, Aishwarya; Raj, Subha S.; Panda, Upasana; Kommula, Snehitha M.; Jose, Christi; Liu, Tianjia; Huang, Shan; Swain, Basudev; Pöhlker, Mira L.; Reyes-Villegas, Ernesto; Ojha, Narendra; Vaishya, Aditya; Bigi, Alessandro; Ravikrishna, R.; Zhu, Qiao; Shi, Liuhua; Allen, James; Martin, Scot T.; Mcfiggans, Gordon; Andreae, Meinrat O.; Pöschl, Ulrich; Coe, Hugh; Bianchi, F.; Su, Hang; Kanawade, Vijay P.; Liu, Pengfei; Gunthe, Sachin S.
abstract
The COVID lockdown presented an interesting opportunity to study the anthropogenic emissions from different sectors under relatively cleaner conditions in India. The complex interplays of power production, industry, and transport could be dissected due to the significantly reduced influence of the latter two emission sources. Here, based on measurements of cloud condensation nuclei (CCN) activity and chemical composition of atmospheric aerosols during the lockdown, we report an episodic event resulting from distinct meteorological conditions. This event was marked by rapid growth and high hygroscopicity of new aerosol particles formed in the SO2 plume from a large coal-fired power plant in Southern India. These sulfate-rich particles had high CCN activity and number concentration, indicating high cloud-forming potential. Examining the sensitivity of CCN properties under relatively clean conditions provides important new clues to delineate the contributions of different anthropogenic emission sectors and further to understand their perturbations of past and future climate forcing.
2023
- Tracing Airborne Microplastics in Modena: results from the MicroTRACES project
[Abstract in Atti di Convegno]
Veratti, Giorgio; Bigi, Alessandro; Teggi, Sergio; Ferrari, Valentina; Scaramelli, Marco; Righi, Sara; Simonini, Roberto; Prevedelli, Daniela; Bergami, Elisa; Ghermandi, Grazia
abstract
2022
- Air quality (PM10) scenarios resulting from the expansion of hydrogen fuel cell electric vehicle in Emilia-Romagna (Northern Italy)
[Relazione in Atti di Convegno]
Fabbi, Sara; Veratti, Giorgio; Bigi, Alessandro; Ghermandi, Grazia
abstract
2022
- IMPATTO DELLA DIFFUSIONE DI VEICOLI ELETTRICI E A IDROGENO SULLE CONCENTRAZIONI DI PM10 IN EMILIA-ROMAGNA
[Articolo su rivista]
Fabbi, Sara; Veratti, Giorgio; Bigi, Alessandro; Ghermandi, Grazia
abstract
PM10 is a critical pollutant for the air quality in Emilia Romagna, a Northern Italy region that includes a large part of the Po Valley. The atmospheric levels of PM10 are strongly affected by vehicular traffic emissions, due to fuel exhaust and also to tires, brake and road surface wear, and to road dust resuspension (non-exhaust emissions). This study presents atmospheric PM10 scenarios deriving from vehicular traffic emissions in Emilia Romagna as resulting in 2030 from the growth of the Fuel Cell Electric Vehicle (FCEV) and battery electric vehicles (BEV) fleet in the region. Both exhaust and non-exhaust vehicular emissions are considered, evaluated according to the most up-to-date regional bottom-up emission inventory, which attributes about 60% of total primary PM10 traffic emissions to wear processes. PM10 concentration maps for actual (2019) and 2030 scenarios are obtained by a Lagrangian dispersion model (PMSS). Preliminary results highlight the future impact on atmospheric PM10 from tires, brake and road surface wear produced by battery electric vehicles, due to their larger mass compared to FCEVs, which have smaller batteries and mass. These emissions will partially offset the lack of PM10 exhaust emissions for electric vehicles. Finally, the daily primary PM10 levels by traffic emissions simulated by PMSS and CHIMERE models were compared at specific sites relevant for the studied domain, i.e. the regulatory air quality monitoring stations, only for actual (2019) scenario.
2022
- Mitigating Indoor Risk of Airborne Infections: the MIRAI project
[Abstract in Atti di Convegno]
Filippini, Tommaso; Vinceti, Marco; Ghermandi, Grazia; Bigi, Alessandro
abstract
2021
- Association between outdoor traffic air pollutants and spread of SARS-CoV-2 pandemic in Modena, Northern Italy
[Abstract in Rivista]
Filippini, Tommaso; Bigi, Alessandro; Teggi, Sergio; Bargellini, Annalisa; Vinceti, Marco
abstract
BACKGROUND AND AIM: Italy was the first European country severely affected by the SARS-CoV-2 pandemic, especially during the first wave in the North of the country. In particular, Modena is a city of Emilia-Romagna which is a region entirely included in the Po valley, one of European areas characterized by the heaviest air pollution levels due also to its orography. Previous studies yielded at a regional level suggested that higher air pollutant levels may increase both SARS-CoV-2 infection and mortality. METHODS: In this study, we further investigated the association between air pollutant exposure and spread of the SARS-CoV-2 using data collected from Modena municipality in the period February 2020-April 2021. We used traffic pollutant levels collected from an urban air quality monitoring station in the period January 2020-January 2021, including particulate matter (PM10), nitrogen oxides (NO2 and NOx), benzene, and black carbon (BC). We used a random-effects linear regression model within panel data analysis over the study period and we computed beta correlation coefficients (beta) with 95% confidence interval-CI between mean daily pollutant concentrations and SARS-CoV-2 daily positive cases diagnosed in Modena. RESULTS:We found a positive correlation between all traffic pollutants and SARS-CoV-2 cases, namely for PM10 beta was 1.23 (95%CI 1.00-1.46), lower for NOx (beta=0.66, 95%CI 0.56-0.75), and higher for NO2 (beta=1.95, 95%CI 1.59-2.31), benzene (beta=41.41, 95%CI 36.23-46.59), and BC (beta=5.95, 95%CI 1.19-10.72). CONCLUSIONS:Notwithstanding the limitations of use of aggregated data and potential the residual confounding, these findings seem to support the hypothesis that high levels of air pollution may favor the spread of SARS-CoV-2 infection, or alternatively that they reflect a higher mobility and number of social contacts that favor the spread of the infection. KEYWORDS: Air pollution, Traffic-related, Infectious diseases, Environmental epidemiology, Exposure assessment
2021
- Biogenic particles formed in the Himalaya as an important source of free tropospheric aerosols
[Articolo su rivista]
Bianchi, F.; Junninen, H.; Bigi, A.; Sinclair, V. A.; Dada, L.; Hoyle, C. R.; Zha, Q.; Yao, L.; Ahonen, L. R.; Bonasoni, P.; Buenrostro Mazon, S.; Hutterli, M.; Laj, P.; Lehtipalo, K.; Kangasluoma, J.; Kerminen, V. -M.; Kontkanen, J.; Marinoni, A.; Mirme, S.; Molteni, U.; Petaja, T.; Riva, M.; Rose, C.; Sellegri, K.; Yan, C.; Worsnop, D. R.; Kulmala, M.; Baltensperger, U.; Dommen, J.
abstract
Aerosols of biogenic and anthropogenic origin affect the total radiative forcing of global climate. Poor knowledge of the pre-industrial aerosol concentration and composition, in particular of particles formed directly in the atmosphere from gaseous precursors, constitutes a large uncertainty in the anthropogenic radiative forcing. Investigations of new particle formation at pre-industrial-like conditions can contribute to the reduction of this uncertainty. Here we present observations taken at the remote Nepal Climate Observatory Pyramid station at 5,079 m above sea level, a few kilometres from the summit of Everest. We show that up-valley winds funnel gaseous aerosol precursors to higher altitudes. During this transport, these are oxidized into compounds of very low volatility, which rapidly form a large number of aerosol particles. These are then transported into the free troposphere, which suggests that the whole Himalayan region may act as an ‘aerosol factory’ and contribute substantially to the free tropospheric aerosol population. Aerosol production in this region occurs mainly via organic precursors of biogenic origin with little evidence of the involvement of anthropogenic pollutants. This process is therefore likely to be essentially unchanged since the pre-industrial period, and may have been one of the major sources that contributes to the upper tropospheric aerosol population during that time.
2021
- Emerging Investigator Series: COVID-19 lockdown effects on aerosol particle size distributions in northern Italy
[Articolo su rivista]
Shen, Jiali; Bigi, Alessandro; Marinoni, Angela; Lampilahti, Janne; Kontkanen, Jenni; Ciarelli, Giancarlo; Putaud, Jean P; Nieminen, Tuomo; Kulmala, Markku; Lehtipalo, Katrianne; Bianchi, Federico
abstract
The lockdown measures implemented to curb the COVID-19 epidemic in Italy reduced human mobility dramatically, which resulted in a marked decline in traffic intensity. In this study, we present the effect of lockdown measures on several air pollutants, particle number size distribution as well as on regional new particle formation (NPF) frequency in the Po Valley (northern Italy). The results show that during the lockdown period, concentrations of nitrogen dioxide (NO2), nitric oxide (NO), benzene (C6H6), and toluene (C7H8) decreased, while ozone (O3) concentrations mildly increased as compared to the corresponding period in 2016-2019. Unlike gaseous pollutants, particulate matter mass concentrations (PM2.5 and PM10) showed no significant changes. The impact of lockdown measures on particle number size distributions were also quite limited. During the lockdown period, the number concentrations of 10-25 and 25-50 nm primary particles were reduced by 66% and 34%, respectively, at the regional background site (Ispra) but surprisingly there was no difference during and after lockdown at the urban background site (Modena). Conversely, the NPF frequency was exceptionally high, 70%, in Modena during the lockdown as compared to values (22-26%) observed for the same period in 2006 and 2009, while NPF frequency in Ispra only slightly increased compared to the same period in 2016-2019. The particle growth rates, however, were slightly lower during the lockdown at both sites compared to other periods. The study shows that a drastic decrease in traffic had little influence on particulate pollution levels in the Po Valley, suggesting that other sources and processes also have a prominent impact on particle number and particulate matter mass concentration in this region.
2021
- Modeling the effect of reduced traffic due to COVID-19 measures on air quality using a chemical transport model: impacts on the Po Valley and the Swiss Plateau regions
[Articolo su rivista]
Ciarelli, Giancarlo; Jiang, Jianhui; El Haddad, Imad; Bigi, Alessandro; Aksoyoglu, Sebnem; Prévôt, André S H; Marinoni, Angela; Shen, Jiali; Yan, Chao; Bianchi, Federico
abstract
The spread of COVID-19 has posed serious challenges for the global communities. To reduce the circulation of the infection, governmental bodies have imposed different lockdown measures at various levels of complexity and duration. As a result, a substantial reduction in mobility might have important, yet unknown, implications for air quality. In this study, we applied the Comprehensive Air quality Model with eXtensions (CAMx) to investigate potential changes in air quality and its chemical composition over northern Italy and Switzerland during periods when lockdown measures were enforced. Our results indicated that lockdown measures reduced nitrogen dioxide (NO2) air concentrations by up to 46% and 25% in the Po Valley and Swiss Plateau regions, respectively, whereas fine particulate matter (PM2.5) air concentrations were reduced only by up to 10% and 6%. This highlights the importance of other emission categories other than traffic for the total PM2.5 levels. The analysis of the PM2.5 components indicated that elemental carbon (EC) and particulate nitrate (NO3 -) were the species most affected by the lockdown measures, whereas a mild increase in the secondary organic aerosol (SOA) concentrations occurred in the Po Valley, and specifically over the metropolitan area of Milan. Our results indicated that an increase in the oxidation capacity of the atmosphere, i.e. in the ˙OH and ˙NO3 radicals, was mainly responsible for the mild increase in SOA concentrations.
2021
- PMSS and gral inter-comparison: Strengths and weaknesses of the two models in reproducing Urban NOx levels in a real case application
[Relazione in Atti di Convegno]
Veratti, G.; Bigi, A.; Fabbi, S.; Ghermandi, G.
abstract
Air dispersion models are useful tools for quantifying pollutant concentrations in urban environment however many issues related to the dispersion estimation within urban canopy still persist. Most of them concern the emissions estimation, the flow field reconstruction between obstacles (buildings, bridges, tunnels, etc.) and the pollutant dispersion driven by the estimated flow field. This study presents results of a model inter-comparison conducted in a real case study, focusing on a 6 km x 6 km square domain covering the city of Modena (Italy), between two Lagrangian dispersion models set-up with the aim of estimating the NOx concentrations produced by traffic flow within the urban area of the city. Comparisons are made between the Graz Lagrangian Model (a.k.a. GRAL) and the Parallel Micro SWIFT and SPRAY (a.k.a. PMSS) modelling suite, in terms of dispersion concentrations and computing cost. The horizontal resolution for both the models is set to 4 meters and the traffic emissions estimation is based on a bottom-up approach: the PTV VISUM traffic model is used to estimate traffic flows on the Modena urban road network and the EMEP/EEA cold and hot emission factors are employed to estimate related emissions. All the other urban emission sources were considered to contribute to the regional background concentrations and estimated with the WRF-Chem model, which estimates also initial and boundary meteorological conditions (multi-scale approach). The general objective of the inter-comparison is to use equivalent input data for both the models keeping the emissions and the meteorological initial and boundary/condition consistent so that any discrepancies in output would be the results of differences in the micro-scale dispersion models. Since different turbulence parametrisation and dispersion scheme are implemented in the two models, the goal of this study is to identify the strengths and the weaknesses of both the models in reproducing urban NOx concentrations, in a real case application, at urban traffic and urban background sites.
2021
- Urban population exposure forecast system to predict NO2 impact by a building-resolving multi-scale model approach
[Articolo su rivista]
Veratti, G.; Bigi, A.; Lupascu, A.; Butler, T. M.; Ghermandi, G.
abstract
Operational forecasting systems based on chemical transport models (CTMs) nowadays generally produce concentration maps with a resolution in the order of 2–5 km, very rarely exceeding the sub-kilometre scale. The main reason for this restriction is the prohibitive computing cost that a simulation covering an entire country would have if set-up with a resolution in the order of meters. In this paper a hybrid forecast system, relying on the WRF-Chem model coupled with the PMSS Lagrangian modelling suite, has been developed and applied for each day of February 2019, to predict hourly NO2 and NOx concentrations with a spatial resolution of 4 m, for the urban area of Modena (a city located in the central Po Valley). Simulated meteorological fields (temperature, wind speed and direction) were assessed at three urban stations, compliant with WMO standards, and modelled concentrations were compared with measurements at two urban air quality stations located at background and traffic sites. Results show that meteorological variables are well captured by the hybrid system and statistical performances are in line with the benchmark values suggested by the European Environmental Agency and with similar case studies focusing on the same area. Modelled NO2 and NOx concentrations, notwithstanding a slight underestimation mainly evident at urban traffic stations for NOx, present a large agreement with related observations. The NO2 Model Quality Objective, as defined by Fairmode guidelines, was met for both the urban stations and the other statistical indexes considered in the evaluation fulfilled the acceptance criteria for dispersion modelling in urban environment, for both NO2 and NOx concentrations. In the second section of the study, the population exposure to forecasted NO2 concentrations has been evaluated adopting a generic model of dynamic population activity. The population was distributed at hourly time steps in specific urban micro-environments at the same resolution of the concentration maps (4 m) and the short-term exposure has been computed as the product between the population density in each model cell and related surface NO2 concentrations. An infiltration factor was also applied to estimate indoor concentrations. The hybrid system was shown to be particularly suited for assessing short-term peak exposure in areas influenced by traffic emissions. On the other hand, due to the limited time spent by the population within traffic related environments, the long-term population exposure calculated by the hybrid system tends to be similar to the WRF-Chem stand-alone estimate.
2020
- A global analysis of climate-relevant aerosol properties retrieved from the network of Global Atmosphere Watch (GAW) near-surface observatories
[Articolo su rivista]
Laj, Paolo; Bigi, Alessandro; Rose, Clémence; Andrews, Elisabeth; Lund Myhre, Cathrine; Collaud Coen, Martine; Lin, Yong; Wiedensohler, Alfred; Schulz, Michael; Ogren, John A.; Fiebig, Markus; Gliß, Jonas; Mortier, Augustin; Pandolfi, Marco; Petäja, Tuukka; Kim, Sang-Woo; Aas, Wenche; Putaud, Jean-Philippe; Mayol-Bracero, Olga; Keywood, Melita; Labrador, Lorenzo; Aalto, Pasi; Ahlberg, Erik; Alados Arboledas, Lucas; Alastuey, Andrés; Andrade, Marcos; Artíñano, Begoña; Ausmeel, Stina; Arsov, Todor; Asmi, Eija; Backman, John; Baltensperger, Urs; Bastian, Susanne; Bath, Olaf; Beukes, Johan Paul; Brem, Benjamin T.; Bukowiecki, Nicolas; Conil, Sébastien; Couret, Cedric; Day, Derek; Dayantolis, Wan; Degorska, Anna; Eleftheriadis, Konstantinos; Fetfatzis, Prodromos; Favez, Olivier; Flentje, Harald; Gini, Maria I.; Gregorič, Asta; Gysel-Beer, Martin; Hallar, A. Gannet; Hand, Jenny; Hoffer, Andras; Hueglin, Christoph; Hooda, Rakesh K.; Hyvärinen, Antti; Kalapov, Ivo; Kalivitis, Nikos; Kasper-Giebl, Anne; Kim, Jeong Eun; Kouvarakis, Giorgos; Kranjc, Irena; Krejci, Radovan; Kulmala, Markku; Labuschagne, Casper; Lee, Hae-Jung; Lihavainen, Heikki; Lin, Neng-Huei; Löschau, Gunter; Luoma, Krista; Marinoni, Angela; Martins Dos Santos, Sebastiao; Meinhardt, Frank; Merkel, Maik; Metzger, Jean-Marc; Mihalopoulos, Nikolaos; Nguyen, Nhat Anh; Ondracek, Jakub; Pérez, Noemi; Perrone, Maria Rita; Petit, Jean-Eudes; Picard, David; Pichon, Jean-Marc; Pont, Veronique; Prats, Natalia; Prenni, Anthony; Reisen, Fabienne; Romano, Salvatore; Sellegri, Karine; Sharma, Sangeeta; Schauer, Gerhard; Sheridan, Patrick; Sherman, James Patrick; Schütze, Maik; Schwerin, Andreas; Sohmer, Ralf; Sorribas, Mar; Steinbacher, Martin; Sun, Junying; Titos, Gloria; Toczko, Barbara; Tuch, Thomas; Tulet, Pierre; Tunved, Peter; Vakkari, Ville; Velarde, Fernando; Velasquez, Patricio; Villani, Paolo; Vratolis, Sterios; Wang, Sheng-Hsiang; Weinhold, Kay; Weller, Rolf; Yela, Margarita; Yus-Diez, Jesus; Zdimal, Vladimir; Zieger, Paul; Zikova, Nadezda
abstract
2020
- Effects of the prewhitening method, the time granularity and the time segmentation on the Mann-Kendall trend detection and the associated Sen's slope
[Articolo su rivista]
Collaud Coen, Martine; Andrews, Elisabeth; Bigi, Alessandro; Romanens, Gonzague; Martucci, Giovanni; Vuilleumier, Laurent
abstract
The most widely used non-parametric method for trend analysis is the Mann-Kendall test associated with the Sen's slope. The Mann-Kendall test requires serially uncorrelated time series, whereas most of the atmospheric processes exhibit positive autocorrelation. Several prewhitening methods have been designed to overcome the presence of lag-1 autocorrelation. These include a prewhitening, a detrending and/or a correction for the detrended slope and the original variance of the time series. The choice of which prewhitening method and temporal segmentation to apply has consequences for the statistical significance, the value of the slope and of the confidence limits. Here, the effects of various prewhitening methods are analyzed for seven time series comprising in-situ aerosol measurements (scattering coefficient, absorption coefficient, number concentration and aerosol optical depth), Raman Lidar water vapor mixing ratio and the tropopause and zero degree levels measured by radio-sounding. These time series are characterized by a broad variety of distributions, ranges and lag-1 autocorrelation values and vary in length between 10 and 60 years. A common way to work around the autocorrelation problem is to decrease it by averaging the data over longer time intervals than in the original time series. Thus, the second focus of this study is evaluation of the effect of time granularity on long-term trend analysis. Finally, a new algorithm involving three prewhitening methods is proposed in order to maximize the power of the test, to minimize the amount of erroneous detected trends in the absence of a real trend and to ensure the best slope estimate for the considered length of the time series.
2020
- Environmental impact estimation of ceramic lightweight aggregates production starting from residues
[Articolo su rivista]
Barbieri, Luisa; Bigi, Alessandro; Andreola, Nora Maria; Lancelotti, Isabella; Ghermandi, Grazia; Teresa Cotes Palomino, Maria; Martínez García, Carmen
abstract
Within a circular economy approach, this study investigates the environmental impact of lightweight aggregates (LWAs) produced starting from different mixes of different clays with brewery sludge and cattle bone flour ash, used as poring and fertilizing agents, respectively. The environmental impact was evaluated by means of release tests, insulation capacity, carbon footprint and particulate matter emission during pellets firing. Release tests representative of LWAs realistic application showed very high release of phosphate and satisfactory release of potassium. The thermal insulation of the LWAs was tested by thermal imaging camera and resulted highly variable depending on the composition, with the mix containing cattle bone flour ash performing best. This latter composition leads also to the smallest CO2 equivalent emission, due to the calorific power of cattle bone flour ash, allowing lower consumption of fossil fuels during the LWA production. Finally, total particulate emissions during the thermal treatment resulted similar in terms of mass for all mixes, while differences in terms of particle morphology and composition occurred. Samples containing residues resulted with a quite good release behavior, carbon footprint and insulation properties, but higher emission of particles, particularly when glass is added.
2020
- Estimate of Secondary NO2 Levels at Two Urban Traffic Sites Using Observations and Modelling
[Articolo su rivista]
Ghermandi, Grazia; Fabbi, Sara; Veratti, Giorgio; Bigi, Alessandro; Teggi, Sergio
abstract
2020
- The development of a building-resolved air quality forecast system by a multi-scale model approach and its application to Modena Urban area, Italy
[Relazione in Atti di Convegno]
Veratti, G.; Bigi, A.; Fabbi, S.; Lupascu, A.; Tinarelli, G.; Teggi, S.; Brusasca, G.; Butler, T. M.; Ghermandi, G.
abstract
One of the main critical air pollutants in terms of health effects is nitrogen dioxide (NO2), whose levels in the last years exceeded national and WHO (World Health Organization) standards in many urban areas across the Po Valley (Northern Italy), exposing urban population to the risk of pollution-related diseases and health conditions. The main goal of this study was to develop a multi-scale modelling system able to forecast hourly NO2 and NOx concentration fields at a building-resolving scale in the urban area of Modena, a city in the middle of the Po Valley, in order to support environmental policies and to take timely protective actions given a forecast of impeding poor air quality. The modelling system relied on two different tools: the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem), which is able to compute concentration fields over regional domain by considering specific emission scenarios and the Parallel Micro SWIFT and SPRAY (PMSS) modelling suite accounting for dispersion phenomena within the urban area. PMSS was used to simulate at building-scale resolution the dispersion of NO and primary NO2 produced by urban sources. Conversely, the WRF-Chem model was selected to reproduce the meteorological input for PMSS and to estimate the formation of secondary NO2. Modelled NO2 and NOx concentrations were compared with measurements at two urban stations, one at traffic site and at background location. Notwithstanding a slight underestimation, mainly evident at urban traffic stations for NOx, simulated concentrations present a large agreement with related observations. The NO2 Model Quality Objective, as defined by Fairmode guidelines, was met for both the urban stations and the other statistical indexes considered in the evaluation fulfilled the acceptance criteria for dispersion modelling in urban environment, for both NO2 and NOx concentrations. In the second section of the study, the population exposure to forecasted NO2 concentrations has been evaluated adopting a generic model of dynamic population activity. Indoor house micro-environments contributed up to 67 % of the total exposure, whilts other outdoor spaces contributed with 24%, divided between traffic environments (8 %) and other outdoor spaces (16 %). Work related buildings contributed for the ramaining share (9 %).
2020
- Towards the coupling of a chemical transport model with a micro-scale Lagrangian modelling system for evaluation of urban NOx levels in a European hotspot
[Articolo su rivista]
Veratti, Giorgio; Fabbi, Sara; Bigi, Alessandro; Lupascu, Aurelia; Tinarelli, Gianni; Teggi, Sergio; Brusasca, Giuseppe; Butler, Tim M.; Ghermandi, Grazia
abstract
2019
- A multiscale modelling approach for evaluation of urban air quality in Modena (Italy)
[Relazione in Atti di Convegno]
Veratti, G.; Fabbi, S.; Bigi, A.; Lupascu, A.; Tinarelli, G.; Teggi, S.; Brusasca, G.; Butler, T. M.; Ghermandi, G.
abstract
A multi-scale modelling system was developed to provide hourly NOx concentrations field at building resolving scale in the urban area of Modena. The WRF-Chem model was employed with aim of reproducing local background concentrations taking into account meteorological and chemical transformation at regional scale, conversely the PMSS modelling system was applied to simulate 3D air pollutant dispersion with a very high-resolution (4 m) on a 6 km x 6 km domain. Modelled NOx concentrations reproduced by this modelling system show a good agreement with observation at both traffic and background urban stations.
2019
- Compression ratios comparison between engines operating with producer gas
[Relazione in Atti di Convegno]
Mason, J.; Kaufmann, B.; Tartarini, P.; Puglia, M.; Morselli, N.; Veratti, G.; Bigi, A.
abstract
2019
- Estimate of secondary NO2 levels at an urban traffic site by microscale simulation of traffic emissions
[Relazione in Atti di Convegno]
Ghermandi, G.; Fabbi, S.; Veratti, G.; Asaro, S.; Bigi, A.; Teggi, S.
abstract
2019
- Forecast of the impact by local emissions at an urban micro scale by the combination of Lagrangian modelling and low cost sensing technology: The TRAFAIR project
[Relazione in Atti di Convegno]
Bigi, A.; Veratti, G.; Fabbi, S.; Po, L.; Ghermandi, G.
abstract
2019
- Impact assessment of vehicular exhaust emissions by microscale simulation using automatic traffic flow measurements
[Articolo su rivista]
Ghermandi, Grazia; Fabbi, Sara; Bigi, Alessandro; Veratti, Giorgio; Despini, Francesca; Teggi, Sergio; Barbieri, Carla; Torreggiani, Luca
abstract
In order to assess the impact of traffic on local air quality a microscale simulation of pollutant concentration fields was produced for two busy intersections, in Reggio Emilia and in Modena, Italy. The simulation was performed by the model suite Micro-Swift-Spray, a Lagrangian particle dispersion model accounting for buildings. Direct measurements of traffic flow were continuously collected in Reggio Emilia over the period January 13–24, 2014 by a two channel radar traffic counter and in Modena from October 28 to November 8, 2016 by four single channel radar traffic counters and used for the hourly modulation of vehicular emissions. Combining radar counts with vehicular fleet composition for each municipality, specific emission factors were obtained. For both cities, simulated concentration fields were compared to local air quality measurements at the nearest urban traffic and urban background sites. The simulated NOx showed large correlation with the observations, notwithstanding some underestimation. The results proved the reliability of the procedure and provided a fair estimate of the NO2 mass fraction of total NOx (primary NO2) due to vehicular emissions in the investigated traffic sites.
2019
- Impact of vehicular emissions in an urban area of the Po valley by microscale simulation with the GRAL dispersion model
[Relazione in Atti di Convegno]
Fabbi, S.; Asaro, S.; Bigi, A.; Teggi, S.; Ghermandi, G.
abstract
This work sets out the test of the GRAL model (Graz Lagrangian Model, vs.18.1) in the urban area of Modena (Po valley, Northern Italy). The simulation domain sizes 2 000 x 3 000 m2 and it features 'microscale' cells of 4 x 4 m2. The simulation focuses on an intersection featured by large traffic flows next to a school and a regulatory air quality monitoring station classified as an urban traffic site. The model is a lagrangian particle dispersion model and it takes into account the presence of buildings as obstacles and generating microscale wind fields accordingly, making this class of model suitable for investigating spatial pattern of atmospheric pollution in urban areas where local accumulation might occur. The simulation investigates traffic emissions of nitrogen oxides (NOx) over the period October 29 to November 10, 2016, when direct measurements of traffic flow were collected by four one-channel doppler radar traffic counters. These counters provided continuous estimate of vehicle length, speed and number. These latter data were combined with available traffic flows at rush hour by PTV VISUM mobility software and the fleet composition of the municipality to estimate the total NOx emissions by vehicular traffic over the roads included in the simulation domain. NOx simulated concentrations showed a moderate correlation with the NOx observations at the nearby monitoring site. To have a better insight on the potential and the limitations of the GRAL model, its results will be compared with the output of the lagrangian particle dispersion model PMSS over the same area.
2019
- Study of copper content distribution through the thermochemical conversion chain of vine pruning biomass
[Relazione in Atti di Convegno]
Santunione, Giulia; Bigi, Alessandro; Puglia, Marco; Morselli, Nicolò; Sebastianelli, Lorenzo; Tartarini, Paolo
abstract
Viticulture is mostly affected by a continuous use of copper-based fungicides to contrast fungal diseases. This treatment, used in both traditional and organic cultures, results in a considerable accumulation of Cu in the top soil, then into plants and soil biota. Furthermore, Copper tends to migrate into air, water and soil ecosystem, posing serious threats to the environment and human health because of its toxicity. At the same time, vineyard pruning represent a valiant woody biomass source for renewable energy production through gasification, the thermochemical process where carbonaceous material is converted into a gaseous flammable fuel called syngas. Currently, one of the important challenges for bioenergy production through gasification is the management of heavy metal-contaminated biomasses used as fuel. This study is aimed to investigate the distribution of copper through thermochemical conversion chain of wood grape, from biomass to electrical and thermal energy production. Starting to the amount of Cu based fertilizers applied to traditional and organic viticulture, the heavy metal residues have been checked and analyzed into ashes biomass derived, into gas emissions coming out from PP20 gasifier and into biochar as gasification process by-product. Inductively coupled plasma mass spectrometry (ICP-MS), and X-ray Fluorescence spectroscopy (XRF) methods have been performed in order to quantify the amount of residual Copper into the different tested arrays. The assessment of Cu persistence along the thermochemical treatment chain of grape biomass is provided. © 2019 ETA-Florence Renewable Energies.
2019
- TRAFAIR: Understanding Traffic Flow to Improve Air Quality
[Relazione in Atti di Convegno]
Po, Laura; Rollo, Federica; Ramòn Rìos Viqueira, Josè; Trillo Lado, Raquel; Bigi, Alessandro; Cacheiro Lòpez, Javier; Paolucci, Michela; Nesi, Paolo
abstract
Environmental impacts of traffic are of major concern throughout many European metropolitan areas. Air pollution causes 400 000 deaths per year, making it first environmental cause of premature death in Europe. Among the main sources of air pollution in Europe, there are road traffic, domestic heating, and industrial combustion. The TRAFAIR project brings together 9 partners from two European countries (Italy and Spain) to develop innovative and sustainable services combining air quality, weather conditions, and traffic flows data to produce new information for the benefit of citizens and government decision-makers. The project is started in November 2018 and lasts two years. It is motivated by the huge amount of deaths caused by the air pollution. Nowadays, the situation is particularly critical in some member states of Europe. In February 2017, the European Commission warned five countries, among which Spain and Italy, of continued air pollution breaches. In this context, public administrations and citizens suffer from the lack of comprehensive and fast tools to estimate the level of pollution on an urban scale resulting from varying traffic flow conditions that would allow optimizing control strategies and increase air quality awareness. The goals of the project are twofold: monitoring urban air quality by using sensors in 6 European cities and making urban air quality predictions thanks to simulation models. The project is co-financed by the European Commission under the CEF TELECOM call on Open Data.
2018
- Atmospheric Dispersion Modelling and Spatial Analysis to Evaluate Population Exposure to Pesticides from Farming Processes
[Articolo su rivista]
Costanzini, Sofia; Teggi, Sergio; Bigi, Alessandro; Ghermandi, Grazia; Filippini, Tommaso; Malagoli, Carlotta; Nannini, Roberta; Vinceti, Marco
abstract
This work originates from an epidemiological study aimed to assess the correlation between population exposure to pesticides used in agriculture and adverse health effects. In support of the population exposure evaluation two models implemented by the authors were applied: a GIS-based proximity model and the CAREA atmospheric dispersion model. In this work, the results of the two models are presented and compared. Despite the proximity analysis is widely used for these kinds of studies, it was investigated how meteorology could affect the exposure assessment. Both models were applied to pesticides emitted by 1519 agricultural fields and considering 2584 receptors distributed over an area of 8430 km2. CAREA output shows a considerable enhancement in the percentage of exposed receptors, from the 4% of the proximity model to the 54% of the CAREA model. Moreover, the spatial analysis of the results on a specific test site showed that the effects of meteorology considered by CAREA led to an anisotropic exposure distribution that differs considerably from the symmetric distribution resulting by the proximity model. In addition, the results of a field campaign for the definition and planning of ground measurement of concentration for the validation of CAREA are presented. The preliminary results showed how, during treatments, pesticide concentrations distant from the fields are significantly higher than background values.
2018
- Performance of NO, NO<sub>2</sub> low cost sensors and three calibration
approaches within a real world application
[Articolo su rivista]
Bigi, Alessandro; Mueller, Michael; Grange, Stuart K.; Ghermandi, Grazia; Hueglin, Christoph
abstract
Low cost sensors for measuring atmospheric pollutants are experiencing an increase in popularity worldwide among practitioners, academia and environmental agencies, and a large amount of data by these devices is being delivered to the public notwithstanding their behaviour, performance and reliability are not yet fully investigated and understood. In the present study we investigate the medium term performance of a set of NO and NO2 electrochemical sensors in Switzerland using 3 different regression algorithms within a field calibration approach. In order to mimic a realistic application of these devices, the sensors were initially co-located at a rural regulatory monitoring site for a 4–month calibration period, and subsequently deployed for 4 months at two distant regulatory urban sites in traffic and urban background conditions, where the performance of the calibration algorithms was explored. The applied algorithms were Multivariate Linear Regression, Support Vector Regression and Random Forest; these were tested, along with the sensors, in terms of generalisability, selectivity, drift, uncertainty, bias, precision and suitability for spatial mapping intra-urban pollution gradients with hourly resolution. Results from the deployment at the urban sites show a better performance of the non-linear algorithms (Support Vector Regression and Random Forest) achieving RMSE < 5 ppb, R2 between 0.74–0.95 and MAE between 2–4 ppb. The combined use of both NO and NO2 sensor output in the estimate of each pollutant showed some contribution by NO sensor to NO2 estimate and vice-versa. All algorithms exhibited a drift ranging between 5–10 ppb for Random Forest and 15 ppb for Multivariate Linear regression at the end of the deployment. The lowest concentration correctly estimated, with a 25 % relative expanded uncertainty, resulted in ca. 15–20 ppb and it was provided by the non-linear algorithms. As an assessment for the suitability of the tested sensors for a targeted application, the probability of resolving hourly concentration difference in cities was investigated. It was found that NO concentration differences of 5–10 ppb (8–10 for NO2) can reliably be detected (90 % confidence), depending on the air pollution level. The findings of this study, although derived from a specific sensor type and sensor model, base on a flexible methodology and have a large potential to explore the performance of other low cost sensors, different in target pollutant and sensing technology.
2018
- Performance of NO, NO2 low cost sensors and three calibration approaches within a real world application
[Articolo su rivista]
Bigi, Alessandro; Mueller, Michael; Grange, Stuart K.; Ghermandi, Grazia; Hueglin, Christoph
abstract
Low cost sensors for measuring atmospheric pollutants are experiencing an increase in popularity worldwide among practitioners, academia and environmental agencies, and a large amount of data by these devices are being delivered to the public. Notwithstanding their behaviour, performance and reliability are not yet fully investigated and understood. In the present study we investigate the medium term performance of a set of NO and NO2 electrochemical sensors in Switzerland using three different regression algorithms within a field calibration approach. In order to mimic a realistic application of these devices, the sensors were initially co-located at a rural regulatory monitoring site for a 4-month calibration period, and subsequently deployed for 4 months at two distant regulatory urban sites in traffic and urban background conditions, where the performance of the calibration algorithms was explored. The applied algorithms were Multivariate Linear Regression, Support Vector Regression and Random Forest; these were tested, along with the sensors, in terms of generalisability, selectivity, drift, uncertainty, bias, noise and suitability for spatial mapping intra-urban pollution gradients with hourly resolution. Results from the deployment at the urban sites show a better performance of the non-linear algorithms (Support Vector Regression and Random Forest) achieving RMSE < ĝ€5ĝ€ppb, <i>R</i>2 between 0.74 and 0.95 and MAE between 2 and 4ĝ€ppb. The combined use of both NO and NO2 sensor output in the estimate of each pollutant showed some contribution by NO sensor to NO2 estimate and vice-versa. All algorithms exhibited a drift ranging between 5 and 10ĝ€ppb for Random Forest and 15ĝ€ppb for Multivariate Linear Regression at the end of the deployment. The lowest concentration correctly estimated, with a 25ĝ€% relative expanded uncertainty, resulted in ca. 15–20ĝ€ppb and was provided by the non-linear algorithms. As an assessment for the suitability of the tested sensors for a targeted application, the probability of resolving hourly concentration difference in cities was investigated. It was found that NO concentration differences of 5–10ĝ€ppb (8–10 for NO2) can reliably be detected (90ĝ€% confidence), depending on the air pollution level. The findings of this study, although derived from a specific sensor type and sensor model, are based on a flexible methodology and have extensive potential for exploring the performance of other low cost sensors, that are different in their target pollutant and sensing technology.
2017
- Air dispersion modelling for the evaluation of population exposure to pollutants emitted by complex areal sources.
[Abstract in Atti di Convegno]
Costanzini, Sofia; Teggi, Sergio; Bigi, Alessandro; Ghermandi, Grazia; Filippini, Tommaso; Malagoli, Carlotta; Vinceti, Marco; Nannini, R.
abstract
.
2017
- Hourly composition of gas and particle phase pollutants at a central urban background site in Milan, Italy
[Articolo su rivista]
Bigi, Alessandro; Bianchi, F.; De Gennaro, G.; Di Gilio, A.; Fermo, P.; Ghermandi, Grazia; Prévôt, A. S. H.; Urbani, M.; Valli, G.; Vecchi, R.; Piazzalunga, A.
abstract
A comprehensive range of gas and particle phase pollutants were sampled at 1-hour time resolution in urban background Milan during summer 2012. Measurements include several soluble inorganic aerosols (Cl−,NO2−,NO3−,SO42−,Ca2+,K+,Mg2+,Na+,NH4+) and gases (HCl, HNO2,HNO3, NH3, NO, NO2,O3, SO2), organic, elemental and black carbon and meteorological parameters. Analysis methods used include mean diurnal pattern on weekdays and Sundays, pollution roses, bivariate polar plots and statistical models using backtrajectories. Results show how nitrous acid (HONO) was mainly formed heterogeneously at nighttime, with a dependence of its formation rate on NO2 consistent with observations during the last HONO campaign in Milan in summer 1998, although since 1998 a drop in HONO levels occurred following to the decrease of its precursors. Nitrate showed two main formation mechanisms: one occurring through N2O5 at nighttime and leading to nitrate formation onto existing particles; another occurring both daytime and nighttime following the homogeneous reaction of ammonia gas with nitric acid gas. Air masses reaching Milan influenced nitrate formation depending on their content in ammonia and the timing of arrival. Notwithstanding the low level of SO2 in Milan, its peaks were associated to point source emissions in the Po valley or shipping and power plant emissions SW of Milan, beyond the Apennines. A distinctive pattern for HCl was observed, featured by an afternoon peak and a morning minimum, and best correlated to atmospheric temperature, although it was not possible to identify any specific source. The ratio of primary-dominated organic carbon and elemental carbon on hourly PM2.5 resulted 1.7. Black carbon was highly correlated to elemental carbon and the average mass absorption coefficient resulted MAC = 13.8 ± 0.2 m2 g−1. It is noteworthy how air quality for a large metropolitan area, in a confined valley and under enduring atmospheric stability, is nonetheless influenced by sources within and outside the valley.
2017
- Impact assessment of pollutant emissions in the atmosphere from a power plant over a complex terrain
[Relazione in Atti di Convegno]
Ghermandi, G.; Fabbi, S.; Arvani, B.; Veratti, G.; Bigi, A.; Teggi, S.
abstract
2017
- Impact Assessment of Pollutant Emissions in the Atmosphere from a Power Plant over a Complex Terrain and under Unsteady Winds
[Articolo su rivista]
Ghermandi, Grazia; Fabbi, Sara; Arvani, Barbara; Veratti, Giorgio; Bigi, Alessandro; Teggi, Sergio
abstract
The development of a natural gas-fired tri-generation power plant (520 MW Combined Cycle Gas Turbines + 58 MW Tri-generation) in the Republic of San Marino, a small independent country in Northern Italy, is under assessment. This work investigates the impact of atmospheric emissions of NO x by the plant, under the Italian and European regulatory framework. The impact assessment was performed by the means of the Aria Industry package, including the 3D Lagrangian stochastic particle dispersion model SPRAY, the diagnostic meteorological model SWIFT, and the turbulence model SURFPRO (Aria Technologies, France, and Arianet, Italy). The Republic of San Marino is almost completely mountainous, 10 km west of the Adriatic Sea and affected by land-sea breeze circulation. SPRAY is suitable for simulations under non-homogenous and non-stationary conditions, over a complex topography. The emission scenario included both a worst-case meteorological condition and three 10-day periods representative of typical atmospheric conditions for 2014. The simulated NO x concentrations were compared with the regulatory air quality limits. Notwithstanding the high emission rate, the simulation showed a spatially confined environmental impact, with only a single NO x peak at ground where the plume hits the hillside of the Mount Titano (749 m a.s.l.), 5 km west of the future power plant.
2017
- µ-MO assessing the contribution of NOXtraffic emission to atmospheric pollution in modena by microscale dispersion modelling
[Relazione in Atti di Convegno]
Veratti, Giorgio; Fabbi, Sara; Tinarelli, Gianni; Bigi, Alessandro; Teggi, Sergio; Brusasca, Giuseppe; Ghermandi, Grazia
abstract
Based on the air pollutant emission inventory data (INEMAR – Arpa Emilia-Romagna 2010) road traffic in Modena, a city in the central Po valley (Northern Italy), contributes up to the 60% of the total emission in terms of NOx, followed by Domestic Heating (15%) and Industrial Combustion (14%). Goal of the -MO project is to assess the road traffic impact on air quality in the urban area of Modena by a combined experimental and modelling approach. Dispersion of vehicular NOxwas simulated by Parallel Micro Swift Spray (PMSS, Arianet srl, Italy and Aria Technologies, France) over a domain of 6 km x 6 km, including most of the urban areas of Modena, with a horizontal resolution of 4 m. The atmospheric emission sources were estimated by merging local fleet composition data, traffic flux at rush hours simulated by PTV VISUM mobility software and direct measurements collected by radar traffic counters, provided by the Municipality of Modena. The modelling system, implemented on a 16 cores cluster (64 GB of total memory), includes PSWIFT, a parallelized mass-consistent diagnostic wind field model, and PSPRAY, a three-dimensional parallel lagrangian particle dispersion model, both able to take into account obstacles (buildings). A run of the system on an entire day has been performed and is presented. In the next step of the work, NOxatmospheric concentration measurements will be provided by the two urban air quality monitoring sites and by a set of 10 monitoring boxes distributed over the domain and featured by small sensors for NO, NO2and particulates. Among the final goals of the -MO project there is the tentative source-apportionment of urban atmospheric NOxbetween traffic emissions, domestic heating and regional background, to support epidemiological studies and finally future urban development strategies.
2017
- Size-segregated aerosol in a hot-spot pollution urban area: Chemical composition and three-way source apportionment
[Articolo su rivista]
Bernardoni, V.; Elser, M.; Valli, G.; Valentini, S.; Bigi, Alessandro; Fermo, P.; Piazzalunga, A.; Vecchi, R.
abstract
In this work, a comprehensive characterisation and source apportionment of size-segregated aerosol collected using a multistage cascade impactor was performed. The samples were collected during wintertime in Milan (Italy), which is located in the Po Valley, one of the main pollution hot-spot areas in Europe. For every sampling, size-segregated mass concentration, elemental and ionic composition, and levoglucosan concentration were determined. Size-segregated data were inverted using the program MICRON to identify and quantify modal contributions of all the measured components. The detailed chemical characterisation allowed the application of a three-way (3-D) receptor model (implemented using Multilinear Engine) for size-segregated source apportionment and chemical profiles identification. It is noteworthy that - as far as we know - this is the first time that three-way source apportionment is attempted using data of aerosol collected by traditional cascade impactors. Seven factors were identified: wood burning, industry, resuspended dust, regional aerosol, construction works, traffic 1, and traffic 2. Further insights into size-segregated factor profiles suggested that the traffic 1 factor can be associated to diesel vehicles and traffic 2 to gasoline vehicles. The regional aerosol factor resulted to be the main contributor (nearly 50%) to the droplet mode (accumulation sub-mode with modal diameter in the range 0.5â1 μm), whereas the overall contribution from the two factors related to traffic was the most important one in the other size modes (34â41%). The results showed that applying a 3-D receptor model to size-segregated samples allows identifying factors of local and regional origin while receptor modelling on integrated PM fractions usually singles out factors characterised by primary (e.g. industry, traffic, soil dust) and secondary (e.g. ammonium sulphate and nitrate) origin. Furthermore, the results suggested that the information on size-segregated chemical composition in different size classes was exploited by the model to relate primary emissions to rapidly-formed secondary compounds.
2017
- Vehicular exhaust impact simulated at microscale from traffic flow automatic surveys and emission factor evaluation
[Relazione in Atti di Convegno]
Ghermandi, Grazia; Fabbi, Sara; Baranzoni, Giulia; Veratti, Giorgio; Bigi, Alessandro; Teggi, Sergio; Barbieri, Carla; Torreggiani, Luca
abstract
Vehicular emissions are a large NOx and CO source in Italian urban areas. In order to assess the impact of heavy traffic roads on local air quality a micro-scale simulation of pollutant concentration fields was produced. The investigated areas are in downtown of Reggio Emilia and Modena, two cities in central Po valley, Italy, and focused on high traffic intersections. An urban traffic station of the regional air quality monitoring network is present in both investigated areas, where traffic is expected to be the main local source of atmospheric pollutants. The simulation has been performed by the micro-scale model suite Micro-Swift-Spray (Aria Technologies, France and ARIANET, Italy) a Lagrangian particle dispersion model directly derived from the SPRAY code, able to account for buildings and obstacles. Simulated pollutants are NOx and CO, as main tracers of combustion emissions. Direct measurements of traffic flow have been continuously collected for 12 day survey periods (in Reggio Emilia from January 13 to 24, 2014 by a two channel doppler radar traffic counter and in Modena from October 28 to November 8, 2016 by four one channel doppler radar traffic counters) and used for the hourly modulation of vehicular emissions. Specific emission factors were obtained by the combination of radar counts with vehicular fleet composition for each municipality: these depend on vehicle type, fuel type, speed and EURO category and were calculated according to the EMEP/EEA guidelines for air pollutant emission inventory. Simulated concentration fields were evaluated over the period with direct traffic counts for the two studied areas: for both areas the results were compared to local air quality measurements collected at the traffic urban monitoring stations and also at the respective urban background stations. The simulated NOx hourly concentrations show a very large agreement with the observations, even if they result underestimated compared to the observed atmospheric concentrations at the traffic site. Simulated and observed concentrations show a fair agreement for CO. The results outline the representativeness of air quality stations in characterizing the sites for pollution level and for dominant pollutant sources.
2016
- A new analytical platform based on field-flow fractionation and olfactory sensor to improve the detection of viable and non-viable bacteria in food
[Articolo su rivista]
Roda, Barbara; Mirasoli, Mara; Zattoni, Andrea; Casale, Monica; Oliveri, Paolo; Bigi, Alessandro; Reschiglian, Pierluigi; Simoni, Patrizia; Roda, Aldo
abstract
An integrated sensing system is presented for the first time, where a metal oxide semiconductor sensor-based electronic olfactory system (MOS array), employed for pathogen bacteria identification based on their volatile organic compound (VOC) characterisation, is assisted by a preliminary separative technique based on gravitational field-flow fractionation (GrFFF). In the integrated system, a preliminary step using GrFFF fractionation of a complex sample provided bacteria-enriched fractions readily available for subsequent MOS array analysis. The MOS array signals were then analysed employing a chemometric approach using principal components analysis (PCA) for a first-data exploration, followed by linear discriminant analysis (LDA) as a classification tool, using the PCA scores as input variables. The ability of the GrFFF-MOS system to distinguish between viable and non-viable cells of the same strain was demonstrated for the first time, yielding 100 % ability of correct prediction. The integrated system was also applied as a proof of concept for multianalyte purposes, for the detection of two bacterial strains (Escherichia coli O157:H7 and Yersinia enterocolitica) simultaneously present in artificially contaminated milk samples, obtaining a 100 % ability of correct prediction. Acquired results show that GrFFF band slicing before MOS array analysis can significantly increase reliability and reproducibility of pathogen bacteria identification based on their VOC production, simplifying the analytical procedure and largely eliminating sample matrix effects. The developed GrFFF-MOS integrated system can be considered a simple straightforward approach for pathogen bacteria identification directly from their food matrix. [Figure not available: see fulltext.]
2016
- Contribution of methane to aerosol carbon mass
[Articolo su rivista]
Bianchi, F.; Barmet, P; Stirnweis, L.; El Haddad, I.; Platt, S. M. .; Saurer, M; Lötscher, C.; Siegwolf, R.; Bigi, Alessandro; Hoyle, C. R.; Decarlo, P. F.; Slowik, J. G. .; Prévôt, A. S. H.; Baltensperger, U.; Dommen, J.
abstract
Small volatile organic compounds (VOC) such as methane (CH4) have long been considered non-relevant to aerosol formation due to the high volatility of their oxidation products. However, even low aerosol yields from CH4 , the most abundant VOC in the atmosphere, would contribute significantly to the total particulate carbon budget. In this study, organic aerosol (OA) mass yields from CH 4 oxidation were evaluated at the Paul Scherrer Institute (PSI) smog chamber in the presence of inorganic and organic seed aerosols. Using labeled 13C methane, we could detect its oxidation products in the aerosol phase, with yields up to 0.09(+0.26 / -0.09) %. Overall, we estimate a maximum contribution of CH4 oxidation of 0.13% to the total global organic aerosol budget. We present evidence that oxidation of formaldehyde, a product of methane oxidation, contributes only a minor fraction to the observed aerosol yields. Therefore, other mechanisms appear to be more important for OA production from CH4 oxidation. A thorough elucidation of such mechanisms is still required. However, our results imply that many other small, volatile, and abundant hydrocarbons thus far considered irrelevant for OA production may contribute to the atmospheric OA budget.
2016
- Correlation between remote sensing data and ground based measurements for solar reflectance retrieving
[Articolo su rivista]
Despini, Francesca; Ferrari, Chiara; Bigi, Alessandro; Libbra, Antonio; Teggi, Sergio; Muscio, Alberto; Ghermandi, Grazia
abstract
Surface and atmospheric modifications due to urbanization generally lead to the urban heat island effect (UHI). This phenomenon is an issue of growing interest and has long been studied by ground based observation. With the advent of remote sensing technologies, observation of UHIs became possible with airborne and spaceborne sensors. Remote sensing data allow urban surfaces characterization to study UHI mitigation methodologies such as the application of cool roofs and cool colors.
In this study remote sensing data have been used first to identify urban surfaces and then to retrieve the solar reflectance value of these surfaces.
The first area of interest is the city of Modena in the Emilia Romagna region (Italy). On this area orthorectified images by an airborne sensor are used. Available images do not allow to directly obtain the solar reflectance value. Therefore it has been investigated a correlation between satellite remote sensing data and ground based measurements.
The solar reflectance was obtained for all urban surfaces of interest such as roofs and pavements. In this way it was possible to assess the real situation and to hypothesize achievable improvements in the solar reflectance of several urban surfaces aimed at improving thermal comfort and energy efficiency of buildings.
2016
- Dispersione atmosferica a microscala di emissioni veicolari da flussi di traffico rilevati automaticamente e confronto con misure di qualità dell’aria
[Articolo su rivista]
Ghermandi, Grazia; Fabbi, Sara; Bigi, Alessandro; Teggi, Sergio; Torreggiani, Luca
abstract
La stima del contributo del traffico veicolare all’inquinamento atmosferico urbano è una informazione fondamentale per la popolazione e le amministrazioni. A questo scopo è stata condotta una simulazione microscala della dispersione delle emissioni da traffico veicolare presso un incrocio trafficato lungo la circolare interna a Reggio Emilia, una città di medie dimensioni nella parte centrale della pianura Padana (Italia settentrionale). L’area studiata include una stazione della rete regionale di monitoraggio della qualità dell’aria: la stazione è classificata come sito urbano di traffico, ovvero ci si attende che la stazione sia principalmente influenzata dalle emissioni da traffico veicolare. I modelli di simulazione a microscala sono maggiormente adatti alla modellizzazione della dispersione in aree urbane, dove la concentrazione in gran parte dipende anche dalla stagnazione di aria dovuta ad edifici ed ostacoli. Micro-Swift-Spray (Aria Technologies, Francia), un modello di dispersione lagrangiano a particelle derivato direttamente dal modello Spray a scala locale, è stato utilizzato per simulare al dispersione delle emissioni da traffico veicolare (in particolare NOx e CO), tenendo conto anche della volumetria degli edifici e degli ostacoli. Un radar conta traffico installato localmente ha fornito velocità e lunghezza dei veicoli in continuo per un periodo di 12 giorni (13 – 24 gennaio 2014). Questi dati, assieme ai dettagli della composizione della flotta, sono stati usati per calcolare fattori di emissioni su misura in base alla tipologia, alimentazione, velocità e classe EURO di emissione. Sono stati prodotti dei campi 3D di concentrazione e i risultati sono stati confrontati con le misure locali di qualità dell’aria: la correlazione tra le concentrazioni orarie di NO x simulate ed osservate è risultata estremamente soddisfacente (r = 0.86). Il confronto con le misure di qualità dell’aria in condizioni di fondo urbano ha permesso di stimare meglio la performance del modello e la quantità di NO x primario e secondario al sito di studio.
2016
- Microscale simulation of road traffic emissions from vehicular flow automatic surveys and comparison with measured concentration data
[Relazione in Atti di Convegno]
Ghermandi, G.; Fabbi, S.; Bigi, A.; Teggi, S.; Torreggiani, L.
abstract
2016
- Trends and variability of atmospheric PM2.5 and PM10-2.5 concentration in the Po Valley, Italy
[Articolo su rivista]
Bigi, Alessandro; Ghermandi, Grazia
abstract
The Po Valley is one of the largest European regions with a remarkably high concentration level of atmospheric pollutants, both for particulate and gaseous compounds. In the last decade stringent regulations on air quality standards and on anthropogenic emissions have been set by the European Commission, including also for PM2.5 and its main components since 2008. These regulations have led to an overall improvement in air quality across Europe, including the Po Valley and specifically PM10, as shown in a previous study by Bigi and Ghermandi (2014). In order to assess the trend and variability in PM2.5 in the Po Valley and its role in the decrease in PM10, we analysed daily gravimetric equivalent concentration of PM2.5 and of PM10-2.5 at 44 and 15 sites respectively across the Po Valley. The duration of the times series investigated in this work ranges from 7 to 10 years. For both PM sizes, the trend in deseasonalized monthly means, annual quantiles and in monthly frequency distribution was estimated: this showed a significant decreasing trend at several sites for both size fractions and mostly occurring in winter. All series were tested for a significant weekly periodicity (a proxy to estimate the impact of primary anthropogenic emissions), yielding positive results for summer PM2.5 and for summer and winter PM10-2.5. Hierarchical cluster analysis showed moderate variability in PM2.5 across the valley, with two to three main clusters, dividing the area in western, eastern and southern/Apennines foothill sectors. The trend in atmospheric concentration was compared with the time series of local emissions, vehicular fleet details and fuel sales, suggesting that the decrease in PM2.5 and in PM10 originates from a drop both in primary and in precursors of secondary inorganic aerosol emissions, largely ascribed to vehicular traffic. Potentially, the increase in biomass burning emissions in winter and the modest decrease in NH3 weaken an otherwise even larger drop in atmospheric concentrations.
2015
- Micro–scale simulation of atmospheric emissions from power–plant stacks in the Po Valley
[Articolo su rivista]
Ghermandi, Grazia; Fabbi, Sara; Zaccanti, MARCO MICHELE; Bigi, Alessandro; Teggi, Sergio
abstract
The atmospheric dispersion of the NOX plume that will be emitted from a new power–plant, at present under installation, was simulated at micro–scale with Micro–Swift–Spray (MSS) Model. The plant will be constructed in a residential urban area in the town of Modena (Po Valley, Northern Italy), where low wind speeds and thermal inversions are quite frequent. Simulation results point out a different behavior of urban canopy in influencing the 3D dispersion patterns among urban obstacles, according to atmospheric mixing conditions: in case of moderate wind events, urban canyon phenomena may occur with a consequent increasing of NOX concentration gradients among buildings, while with low winds the near–field influence of the buildings emphasizes pollutant accumulation. The MSS simulated NOX concentrations result always much lower than the regulatory limits for air quality. The comparison of simulation results with measured concentration data for NOX shows the importance of micro–scale dispersion modeling to perform an accurate and reliable assessment of meteorological condition effects on pollutant distribution, and the ability of MSS in providing reliable simulations of atmospheric dispersion.
2015
- The Ice Selective Inlet: A novel technique for exclusive extraction of pristine ice crystals in mixed-phase clouds
[Articolo su rivista]
Kupiszewski, P; Weingartner, E.; Vochezer, P.; Schnaiter, M.; Bigi, Alessandro; Gysel, M.; Rosati, B.; Toprak, E.; Mertes, S.; Baltensperger, U.
abstract
Climate predictions are affected by high uncertainties partially due to an insufficient knowledge of aerosol–cloud interactions. One of the poorly understood processes is formation of mixed-phase clouds (MPCs) via heterogeneous ice nucleation. Field measurements of the atmospheric ice phase in MPCs are challenging due to the presence of much more numerous liquid droplets. The Ice Selective Inlet (ISI), presented in this paper, is a novel inlet designed to selectively sample pristine ice crystals in mixed-phase clouds and extract the ice residual particles contained within the crystals for physical and chemical characterization. Using a modular setup composed of a cyclone impactor, droplet evaporation unit and pumped counterflow virtual impactor (PCVI), the ISI segregates particles based on their inertia and phase, exclusively extracting small ice particles between 5 and 20 μm in diameter. The setup also includes optical particle spectrometers for analysis of the number size distribution and shape of the sampled hydrometeors. The novelty of the ISI is a droplet evaporation unit, which separates liquid droplets and ice crystals in the airborne state, thus avoiding physical impaction of the hydrometeors and limiting potential artefacts. The design and validation of the droplet evaporation unit is based on modelling studies of droplet evaporation rates and computational fluid dynamics simulations of gas and particle flows through the unit. Prior to deployment in the field, an inter-comparison of the optical particle size spectrometers and a characterization of the transmission efficiency of the PCVI was conducted in the laboratory. The ISI was subsequently deployed during the Cloud and Aerosol Characterization Experiment (CLACE) 2013 and 2014 – two extensive international field campaigns encompassing comprehensive measurements of cloud microphysics, as well as bulk aerosol, ice residual and ice nuclei properties. The campaigns provided an important opportunity for a proof of concept of the inlet design. In this work we present the setup of the ISI, including the modelling and laboratory characterization of its components, as well as field measurements demonstrating the ISI performance and validating the working principle of the inlet. Finally, measurements of biological aerosol during a Saharan dust event (SDE) are presented, showing a first indication of enrichment of bio-material in sub-2 μm ice residuals.
2014
- Air pollution assessment over Po valley (Italy) using satellite data and ground station measurements
[Relazione in Atti di Convegno]
Arvani, Barbara; Teggi, Sergio; Ghermandi, Grazia; Bigi, Alessandro; Pierce, R. Bradley
abstract
Due to their effect on human health, the study of atmospheric pollutants is an important concern in the Po valley – northern Italy – one of the main industrialized and populated areas of the country. Our work focuses on the applicability of satellite Aerosol Optical Depth (AOD) retrievals in support of air quality monitoring and assessment in urban environments within the Po valley. This has been accomplished by using the implementation of the International MODIS/AIRS Processing Package (IMAPP) Air Quality Applications software, IDEA-I (Infusing satellite Data into Environmental Applications-International) over the Po valley study area. IDEA-I is a globally configurable software package that uses either Terra or Aqua MODerate resolution Imaging Spectro-radiometer (MODIS) AOD product retrievals to identify local domains of high values of aerosol. For our specific analyses, IDEA-I has been used over the large European domain, centred over the Po Valley. One year (2012) of MODIS AOD product retrievals from MODIS on board NASA’s Terra (MOD04) or Aqua (MYD04) satellite has been considered using IDEA-I in a retrospective study. These retrieved data have been also compared with the Particulate Matter (PM 10 ) measurements from the Italian Agency for Environmental Protection (ARPA) ground-based network stations. The acceptable results obtained by the correlation PM 10 – AOD suggest the satellite AOD as a good substitute for monitoring air quality over the Po valley domain. Yet the 10 km resolution of MODIS – AOD product is considered too large for air quality studies at urban scale. Recently, a new Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm has been developed for MODIS which provides AOD data at 1 km of spatial resolution. We have evaluated ability of MODIS product MOD04 and MAIAC products to characterize the spatial distribution of aerosols in the urban area through comparison with surface PM 10 measurements. Using MAIAC data at 1 km, we have examined the relationship between PM 10 concentrations, AOD, and AOD normalized by Planetary Boundary Layer (PBL) depths obtained from NOAA National Center for Environmental Prediction (NCEP) Global Data Assimilation System (GDAS), for the same period of analysis. Results show that the MAIAC retrieval provides a high resolution depiction of the AOD within the Po Valley and performs nearly as well in a statistical sense as the standard MODIS retrieval during the time period considered. Results also highlight that normalization by the analyzed PBL depth to obtain an estimate of the mean boundary layer extinction is needed to capture the seasonal cycle of the observed PM 10 over the Po Valley.
2014
- Atmospheric impact of power plant stack emissions using air pollutant dispersion model at micro-scale
[Relazione in Atti di Convegno]
Zaccanti, MARCO MICHELE; Ghermandi, Grazia; Fabbi, Sara; Bigi, Alessandro; Teggi, Sergio
abstract
This study deals with a case of local air quality impact arising from a power plant (tri-generator and conventional boilers) designed to meet the energy demand of the General Hospital of Modena, central Po Valley, Northern Italy. Stack emissions are expected to fall over the densely populated urban area nearby the General Hospital, where main impacting sources currently are vehicular traffic and household heating system. Pollutant accumulation phenomena often occur in Modena, especially during winter season, even because calm wind events and strong atmospheric stability are very frequent and tend to prevent pollution removal. Hence high concentration levels for atmospheric pollutants, such as NO x , CO and PM10, are recurrently expected. The atmospheric impact of the power plant can be assessed using dispersion modeling, in order to simulate pollutant distribution, i.e. concentration fields, in the surrounding of the source. Since the plant is placed within the urban area the dispersion phenomena are not only driven by meteorology, but depend also on airflow perturbations by turbulence due to the urban canopy. In such complex conditions, the simulation of pollutant dispersion has been performed by a micro-scale dispersion model, which is able to take into account building shape and arrangement, as well as non-homogeneous and non-stationary conditions. Micro-scale simulations were carried out for power plant NO x emissions according to different daily meteorological scenarios; all simulations span over a period of 24 hours, and a hourly modulation of emission pattern and meteorological data is considered. Simulation results are presented through concentration maps and compared with hourly concentration data measured at the air quality monitoring sites by the Local Environmental Agency in Modena. Aim of the study is to compare the contribution of power plant emissions on air quality with the other NO x emission sources impacting on the receptors. Future analyses will focus on more detailed investigation of source contribution apportionment, by the simulation of both power plant and vehicular traffic emissions. All simulations were performed using ARIA INDUSTRY software package, developed by Arianet s.r.l.
2014
- Climatology of atmospheric PM10 concentration in the Po Valley
[Articolo su rivista]
Bigi, Alessandro; Ghermandi, Grazia
abstract
The limits to atmospheric pollutant concentration set by the European Commission provide a challenging target for the municipalities in the Po Valley, because of the characteristic climatic conditions and high population density of this region. In order to assess climatology and trends in the concentration of atmospheric particles in the Po Valley, a dataset of PM10 data from 41 sites across the Po Valley have been analysed, including both traffic and background sites (either urban, suburban or rural). Of these 41 sites, 18 with 10 yr or longer record have been analysed for long term trend in de-seasonalized monthly means, in annual quantiles and in monthly frequency distribution. A widespread significant decreasing trend has been observed at most sites, up to few percent per year, by Generalised Least Square and Theil-Sen method. All 41 sites have been tested for significant weekly periodicity by Kruskal–Wallis test for mean anomalies and by Wilcoxon test for weekend effect magnitude. A significant weekly periodicity has been observed for most PM10 series, particularly in summer and ascribed mainly to anthropic particulate emissions. A cluster analysis has been applied in order to highlight stations sharing similar pollution conditions over the reference period. Five clusters have been found, two gathering the metropolitan areas of Torino and Milano and their respective nearby sites and the other three clusters gathering north-east, north-west and central Po Valley sites respectively. Finally the observed trends in atmospheric PM10 have been compared to trends in provincial emissions of particulates and PM precursors, and analysed along with data on vehicular fleet age, composition and fuel sales. Significant basin-wide drop in emissions occurred for gaseous pollutants, contrarily to emissions of PM10 and PM2.5, whose drop resulted low and restricted to few provinces. It is not clear whether the decrease for only gaseous emissions is sufficient to explain the observed drop in atmospheric PM10, or if the low drop in particulate emissions is indeed due to the uncertainty in the emission inventory data for this species.
2014
- Long-term trend and variability of atmospheric PM10 concentration in the Po Valley
[Articolo su rivista]
Bigi, Alessandro; Ghermandi, Grazia
abstract
The limits to atmospheric pollutant concentration set by the European Commission provide a challenging target for the municipalities in the Po Valley, because of the characteristic climatic conditions and high population density of this region. In order to assess climatology and trends in the concentration of atmospheric particles in the Po Valley, a data set of PM10 data from 41 sites across the Po Valley have been analysed, including both traffic and background sites (either urban, suburban or rural). Of these 41 sites, 18 with 10 yr or longer record have been analysed for long-term trend in deseasonalized monthly means, in annual quantiles and in monthly frequency distribution. A widespread significant decreasing trend has been observed at most sites, up to a few percent per year, by a generalized least squares and Theil–Sen method. All 41 sites have been tested for significant weekly periodicity by Kruskal–Wallis test for mean anomalies and by Wilcoxon test for weekend effect magnitude. A significant weekly periodicity has been observed for most PM10 series, particularly in summer and ascribed mainly to anthropic particulate emissions. A cluster analysis has been applied in order to highlight stations sharing similar pollution conditions over the reference period. Five clusters have been found, two encompassing the metropolitan areas of Turin and Milan and their respective nearby sites and the other three clusters gathering northeast, northwest and central Po Valley sites respectively. Finally, the observed trends in atmospheric PM10 have been compared to trends in provincial emissions of particulates and PM precursors, and analysed along with data on vehicular fleet age, composition and fuel sales. A significant basin-wide drop in emissions occurred for gaseous pollutants, contrarily to emissions of PM10 and PM2.5, whose drop was low and restricted to a few provinces. It is not clear whether the decrease for only gaseous emissions is sufficient to explain the observed drop in atmospheric PM10, or if the low drop in particulate emissions is indeed due to the uncertainty in the emission inventory data for this species.
2014
- PM2.5 in the Po valley: patterns, long term trends and their influence on air quality
[Relazione in Atti di Convegno]
Bigi, Alessandro; Ghermandi, Grazia; Cecchi, Rodolfo; Teggi, Sergio
abstract
Po Valley is one the largest European region with remarkably high concentration level of atmospheric pollutants, both for particulate and gaseous compounds. In the last decade stringent regulations on air quality standards and on anthropogenic emissions have been set by the European Commission, leading to the latest 2008/50/CE, which requires a monitoring plan also for PM2.5, used as an indicator of population exposure to atmospheric particulates. These regulations lead to an overall improvement on air quality across Europe, including PM10 in the Po valley (Bigi and Ghermandi, 2014). Due to the different nature of PM2.5 and its large fraction of secondary aerosols, patterns and trends of PM2.5 exhibit large difference to PM10 features, therefore the latest air quality regulations may represent a hard challenge for municipalities and environmental agencies. Daily gravimetric equivalent PM2.5 concentration at 44 sites over the Po valley (either in urban or rural background conditions) has been analysed. Long term trends on deseasonalized monthly means have been estimated by Generalised Least Squares. These results have been compared with trends on annual quantiles. Changes, over the sampling period, in frequency distribution of PM2.5 in each month have also been estimated. For each site, impact of primary anthropogenic particulate emissions has been qualitatively estimated by testing PM2.5 series for a significant weekly periodicity using three different metrics. The former compares the median among time series of PM2.5 anomalies of weekdays, the second consists in the weekend effect magnitude. The latter used frequency domain analysis in order to test whether estimated spectral density at 1/7 day-1 frequency is significantly higher than the spectral density of a red noise series. Finally a cluster analysis on the dataset has been performed, showing a geographical pattern for PM2.5 concentration across the valley. This study provides a reliable tool to asses the impact of the current and previous emission control policies across the Po valley.
2014
- Remote sensing and GIS for the modeling of persistent organic pollutant in the marine environment
[Relazione in Atti di Convegno]
Costanzini, Sofia; Teggi, Sergio; Bigi, Alessandro; Ghermandi, Grazia
abstract
The characterization of the marine environment plays an important role in the understanding of the dynamics affecting the transport, fate and persistence (TFP) of Persistent Organic Pollutants (POPs). This work is part of a project funded by the Ministero dell’Istruzione, dell’Università e della Ricerca. The aim of the project is the assessment of the TFP of POPs in the Mediterranean sea. The analysis will be carried out at regionalmesoscale (central Mediterranean), and at local spatial scale considering different Italian test sites (the Delta of the Po River, the Venice Lagoon and the estuary of the Rio Nocella). The first step of this work involves the implementation of GIS geodatabases for the definition of the input dataset. The geodatabases were populated with MERIS and MODIS level 2 and level 3 products of Chlorophyll-a (CHL-a), Chromophoric Dissolved Organic Matter (CDOM), Aerosol Optical Thickness (AOT), Diffuse Attenuation Coefficient (DAC), Particulate Inorganic Carbon (PIC), Particulate Organic Carbon (POC) and Sea Surface Temperature (SST). The spatial scale (central Mediterranean sea) and the reference system (Plate Carrée projection) have been imposed as a constraint for the geodatabases. Four geodatabases have been implemented, two for MODIS and two for MERIS products with a monthly, seasonal and climatological temporal scale (2002 -2013). Here, we present a first application of a methodology aimed to identify vulnerable areas to POPs accumulation and persistence. The methodology allowed to assess the spatial distribution of the CHL-a in the central Mediterranean sea. The chlorophyll concentration is related to the amount of nutrients in the water and therefore provides an indicator of the potential presence of POPs. A pilot area of 300 x 200 km located in the North Adriatic sea has been initially considered. The seasonal and climatological MODIS and MERIS CHL-a variability were retrieved and compared with in-situ forcing parameters, i.e. Po River discharge rates and wind data. Study outlooks include a better accuracy of the distribution of the vulnerable areas achieved through the use of additional parameters (CDOM, SST, POC), and an assessment of the contribution of the contaminants by atmospheric dry deposition to the marine environment. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
2014
- The Ice Selective Inlet: a novel technique for exclusive extraction of pristine ice crystals in mixed-phase clouds
[Articolo su rivista]
Kupiszewski, P.; Weingartner, E.; Vochezer, P.; Bigi, Alessandro; Rosati, B.; Gysel, M.; Schnaiter, M.; Baltensperger, U.
abstract
Climate predictions are affected by high uncertainties partially due to an insufficient knowledge of aerosol-cloud interactions. One of the poorly understood processes is formation of mixed-phase clouds (MPCs) via heterogeneous ice nucleation. Field measurements of the atmospheric ice phase in MPCs are challenging due to the presence of supercooled liquid droplets. The Ice Selective Inlet (ISI), presented in this paper, is a novel inlet designed to selectively sample pristine ice crystals in mixed-phase clouds and extract the ice residual particles contained within the crystals for physical and chemical characterisation. Using a modular setup composed of a cyclone impactor, droplet evaporation unit and pumped counterflow virtual impactor (PCVI), the ISI segregates particles based on their inertia and phase, exclusively extracting small ice particles between 5 and 20 μm in diameter. The setup also includes optical particle spectrometers for analysis of the number size distribution and shape of the sampled hydrometeors. The novelty of the ISI is a droplet evaporation unit, which separates liquid droplets and ice crystals in the airborne state, thus avoiding physical impaction of the hydrometeors and limiting potential artifacts. The design and validation of the droplet evaporation unit is based on modelling studies of droplet evaporation rates and computational fluid dynamics simulations of gas and particle flows through the unit. Prior to deployment in the field, an inter-comparison of the WELAS optical particle size spectrometers and a characterisation of the transmission efficiency of the PCVI was conducted in the laboratory. The ISI was subsequently deployed during the Cloud and Aerosol Characterisation Experiment (CLACE) 2013 – an extensive international field campaign encompassing comprehensive measurements of cloud microphysics, as well as bulk aerosol, ice residual and ice nuclei properties. The campaign provided an important opportunity for a proof of concept of the inlet design. In this work we present the setup of the ISI, including the modelling and laboratory characterisation of its components, as well as a case study demonstrating the ISI performance in the field during CLACE 2013.
2014
- Tri-generation power plant and conventional boilers: pollutant flow rate and atmospheric impact of stack emissions
[Articolo su rivista]
Ghermandi, Grazia; Teggi, Sergio; Fabbi, Sara; Bigi, Alessandro; Zaccanti, MARCO MICHELE
abstract
The atmospheric impact of stack emissions from a power plant (tri-generator and boilers) that will be installed in an urban area in the central Po valley (Northern Italy), characterized by calm wind events, are studied and compared to the impact of the existing plant (conventional boilers). Both the plants are supplied by methane gas. The atmospheric dispersion of NOx emitted is simulated, both in the current and future scenario, by the software package ARIA INDUSTRY. The NOx emission rates are set equal to the regulatory emission limits for existing and future boilers, while the tri-generation system emission rates are set equal to the emission limits certified by the system manufacturer. The simulation periods focus over the 2010 winter season. The simulation estimates the impact of NOx emissions on air quality (vertical concentration profiles and concentration maps at the ground) in the urban area close to the plant. The future power plant impact on air quality results lower than the impact of the existing plant, even if the yearly total mass of pollutants emitted in atmosphere from the new power plant is higher than from the existing plant. The emissions of conventional boilers result the main responsible of the air pollution at the ground in the future scenario.
2014
- Urban micro-scale investigation of nox and co emissions from vehicular traffic and comParison with air quality data
[Relazione in Atti di Convegno]
Ghermandi, G.; Fabbi, S.; Zaccanti, M.; Bigi, A.; Teggi, S.
abstract
2013
- H15-123: From local-scale to micro-scale assessment of the atmospheric impact of the pollutant plume emitted from a power-plant stack
[Relazione in Atti di Convegno]
Ghermandi, G.; Teggi, S.; Fabbi, S.; Bigi, A.; Zaccanti, M. M.
abstract
2013
- Implementation of IMAPP/IDEA-I over the Po Valley region, northern Italy, for air quality monitoring and forecasting
[Relazione in Atti di Convegno]
Arvani, Barbara; R. B., Pierce; Teggi, Sergio; Bigi, Alessandro; Ghermandi, Grazia
abstract
Satellite Earth Observations (EO) represent a powerful tool for environmental applications
such as air quality monitoring and forecasting; new sensors and image processing
methodologies allow for better spatial resolution. Air pollution is an important concern in
the Po valley (northern Italy), one of the main industrialized and populated areas of the
country, and, for this reason, intensely studied. In this work we focus on the applicability
of satellite Aerosol Optical Depth (AOD) retrievals in support of air quality monitoring and
assessment in urban environments within the Po valley by using the implementation of
the International MODIS/AIRS Processing Package (IMAPP) Air Quality Applications
software, IDEA-I (Infusing satellite Data into Environmental Applications-International)
over the area. For our specific analyses, IDEA-I was installed at University of Modena
and Reggio Emilia, (Italy) using a large European domain, and a smaller domain over the
Po valley. One year (2012) of MOD04 AOD retrievals from MODIS on board NASA’s
Terra satellite was considered using IDEA-I in a retrospective study. We needed to
develop tools to adapt IDEA-I using MODIS AOD data archived at the NASA Level 1 and
Atmosphere Archive and Distribution System (LAADS). This was required because IDEA-
I is setup for near-real time use of MODIS Direct Broadcast retrievals by default. The
Level 2 Aerosol Products, collection 5.1 have been used, which returns AOD data at 0.55
µm with a spatial resolution of 10X10 km 2 retrieved from MODIS (MOD04). These
retrieved data were compared with PM 10 mass concentration measurements from the
Italian Agency for Environmental Protection (ARPA) network. Correspondence between
AOD and PM 10 data suggests that satellite AOD values could be a good substitute for
monitoring air quality over the Po valley domain. Moreover, the integration of the use of
IDEA-I over the Po valley could give the opportunity to monitor and forecast air pollution
and understand particular polluted situations in the past with a retrospective use of IDEA-
I. Because of the limited domain of analyses, it is useful to refine the spatial resolution of
MODIS AOD maps. This will be accomplished by introducing the use of a recently
developed AOD algorithm, MAIAC (Multi-angle Implementation of Atmospheric
Correction), which provides MODIS AOD maps at a high spatial resolution of 1 km. This
new application will permit us to obtain high resolution AOD maps for the year 2012 over
the Po valley domain.
2012
- Analysis of the air pollution climate at a background site in the Po valley
[Articolo su rivista]
Bigi, Alessandro; Ghermandi, Grazia; R. M., Harrison
abstract
The Po valley in northern Italy is renowned for its high air pollutant concentrations. Measurements of air pollutants from a background site in Modena, a town of 200 thousand inhabitants within the Po valley, are analysed. These comprise hourly data for CO, NO, NO2, NOx, and O3, and daily gravimetric equivalent data for PM10 from 1998–2010. The data are analysed in terms of long-term trends, annual, weekly and diurnal cycles, and auto-correlation and cross-correlation functions. CO, NO and NO2 exhibit a strongly traffic-related pattern, with daily peaks at morning and evening rush hour and lower concentrations over the weekend. Ozone shows an annual cycle with a peak in July due to local production; notwithstanding the diurnal cycle dominated by titration by nitrogen oxide, the decreasing long term trend in NO concentration did not affect the long term trend in O3, whose mean concentration remained steady over the sampling period. PM10 shows a strong seasonality with higher concentration in winter and lower concentration in summer and spring. Both PM10 and ozone show a marked weekly cycle in summer and winter respectively. Regressions of PM10 upon NOx show a consistently greater intercept in winter, representing higher secondary PM10 in the cooler months of the year. There is a seasonal pattern in primary PM10 to NOx ratios, with lower values in winter and higher values in summer, but the reasons are unclear.
2012
- GIS methods for health and environmental monitoring and assessment
[Relazione in Atti di Convegno]
Teggi, Sergio; Ghermandi, Grazia; Fabbi, Sara; Bigi, Alessandro; Vinceti, Marco; Malagoli, Carlotta
abstract
Very often, health and environmental studies are based on the identification of correlations between population exposure to environmental agents and their effects on population health. Time and space are among the principal variables for this kind of analysis. The latter generates a significant increase in complexity of the study. Spatial analysis requires very different methods and skills, such as those on Geographic Information Systems (GIS) and on geostatistics. In this work we describe the models of geographic data (GIS data models) implemented in the framework of several health studies done recently. As an example, we describe the GIS data model generated for the city of Modena. We highlight the potentiality of GIS for health and environmental monitoring and assessment, by describing the GIS data models contents, the elaboration levels and the principal studies for which it has been used so far.
2012
- Long term trends and patterns of atmospheric pollutants in Modena, Po valley, Italy
[Relazione in Atti di Convegno]
Bigi, Alessandro; Ghermandi, Grazia; Cecchi, Rodolfo
abstract
The concentration of atmospheric pollutants in the Po Valley is renowned for its remarkably high levels, both for particulate and gaseous compounds. This analysis focussed on measurements of air pollutants from a background site in Modena, Po valley, Italy. These comprise hourly data for CO, NO, NO2, NOx, O3 and daily gravimetric equivalent data for PM10 from 1998 – 2010. The data are analysed in terms of long-term trends, and of annual, weekly and diurnal patterns. Auto-correlation and cross-correlation functions are also investigated. Influence of anthropogenic sources on pollutant concentration has been studied by checking the presence of weekly cycles on pollutants. Gaseous pollutant characteristic of vehicular traffic emissions (i.e. CO, NO and NO2) exhibit a daily pattern featured by peaks at morning and evening rush-hour and lower concentrations over the weekend. Ozone, whose annual pattern is typified by summer peak due to local production, did not show a significant variation in long term trend notwithstanding the significant decrease in NO over the decade. Regression models of PM10 upon NOx show a greater intercept in winter, representing higher secondary PM10 in the cooler months of the year, and a seasonal pattern in the PM10 to NOx ratio, with lower values in winter and higher in summer.
2012
- Model comparison in simulating the atmospheric dispersion of a pollutant plume in low wind conditions
[Articolo su rivista]
Ghermandi, Grazia; Teggi, Sergio; Fabbi, Sara; Bigi, Alessandro; Cecchi, Rodolfo
abstract
Simulations of emitted plume dispersion in atmosphere performed by means of different models are compared: the study evaluates the capabilities of gaussian and lagrangian models in simulating pollutant plume dispersion in low wind conditions.
2012
- Statistical analysis of surface atmospheric pollutant measurement series for various sites across the Po valley
[Relazione in Atti di Convegno]
Bigi, Alessandro; Ghermandi, Grazia
abstract
In order to assess recent changes in the concentration of pollutants in the Po valley, ten-year or longer time series of atmospheric pollutants have been analyzed, including both traffic and background sites (either urban, suburban or rural) at main towns and cities in the Po valley. The dataset comprise pollution data from Regional Environmental Agency monitoring networks; all data are referred to actual sampling condition, as by 2008/50/EC. Weekly pattern at each site has been estimated, in order to assess pollution condition and anthropogenic sources influence at each station. Time series have been checked for significant change in de-seasonalized mean monthly concentration and in annual median concentration. Mean daily concentration data have been tested for significant weekly (i.e. anthropogenic) cycles. Long term trend of atmospheric pollutants has been estimated via parametric and non-parametric methods. Finally, cluster analysis has been applied in order to highlight stations sharing similar pollution conditions over the reference period.
2012
- Tri-generation power plant and conventional boilers: pollutant flow rate and atmospheric impact of stack emissions
[Relazione in Atti di Convegno]
Ghermandi, Grazia; Teggi, Sergio; Fabbi, Sara; Bigi, Alessandro; Zaccanti, MARCO MICHELE
abstract
The atmospheric impact of stack emissions from a power plant (tri-generator and boilers) that will be installed in an urban area in the central Po valley, characterized by calm wind events, are studied and compared to the impact of the existing plant (conventional boilers). Both the plants are supplied by methane gas. The atmospheric dispersion of NOx emitted is simulated, both in the current and future scenario, by the software package ARIA INDUSTRY. The emission rates are set equal to the regulatory emission limits for existing and future boilers, while the tri-generation system emission rates are set equal to the emission limits certified by the system manufacturer. Local datasets have been used. The simulation periods span over the 2010 winter season. The simulation estimates the impact of emissions on air quality (vertical concentration profiles and concentration maps at the ground) in the urban area close to the plant. The future power plant impact on air quality (i.e. respect to the regulatory pollutant concentration limits) results lower than the impact of the existing plant, even if the yearly total mass of pollutants emitted in atmosphere from the new power plant is higher than from the existing plant.
2011
- Atmospheric impact of power plant stack emissions
[Relazione in Atti di Convegno]
Ghermandi, Grazia; Teggi, Sergio; Fabbi, Sara; Bigi, Alessandro; M. M., Zaccanti
abstract
The atmospheric impact of stack emissions from a tri-generation power plant that will be installed in a urban area in the central Po valley are studied and compared to the impact of the existing plant (conventional boilers). Both the plants are supplied by methane gas. The atmospheric dispersion of the emissions is simulated both in the current and the future scenario, i.e. before and after tri-generation plant activation respectively. The plant is assumed as a continuous emission point source. The emission rates are set equal to the regulatory emission limits for the existing plant and to the emission limits certified by the tri-generation system maker company for the future plant. The local meteorological, topographical and surface land cover datasets have been used. The simulation periods span over each one of the four seasons, using 2010 meteorological data, to test conditions both favourable and unfavourable to pollutant accumulation in the atmosphere; simulation period spanning over the whole 2010 year are also performed (long-term) . The dispersion of different air pollutants (NOx mainly) is presented; the concentration fields obtained for the same period in the two different scenarios are compared. The aim of the simulation is to estimate the impact of emissions on air quality in the urban area close to the plant, in different weather conditions, in a region characterized by calm wind events. The tri-generation power plant impact on air quality (i.e. respect to the regulatory concentration limits for pollutants in atmosphere) results lower than the impact of the existing plant, even if the yearly total mass of pollutants emitted in atmosphere from the tri-generation power plant is higher than from the existing plant. The simulation is performed by the software package ARIA INDUSTRY, that is made up of the 3D lagrangian stochastic particle dispersion model SPRAY, the diagnostic meteorological model MINERVE and the turbulence model SURFPRO.
2011
- Particle number size distribution and weight concentration of background urban aerosol in a Po valley site
[Articolo su rivista]
Bigi, Alessandro; Ghermandi, Grazia
abstract
Abstract Measurements of particle size distributions and PM2.5 from an urban background site in the Central Po Valley are analysed; the site is one of the medium–small-size cities in the central valley, without the direct influence of the metropolitan and industrial area of Milan and of the Adriatic Sea. The data comprise number concentration of particle with diameters ranging between 10 and 700 nm, PM2.5 and main meteorological variables from February to August 2008. Daily cycles of the observed pollutants are analysed, along with auto-correlation function for particle number concentration and principal component analysis (PCA) of all the available variables; finally, the diurnal pattern of PM2.5 low-, medium- and high-pollution events has been investigated. Total particle number concentration showed a daily pattern both in winter and summer, although different between weekdays and Sundays and with wider variations during the cold season. A daily cycle is present for the geometric mean diameter of nucleation mode particles in winter and of nucleation and Aitken mode particles in summer. PM2.5 showed a slight daily pattern for weekdays and Sundays, similar, but lagged, to total particle count cycle. Mixing layer depth resulted the main process controlling PM2.5, although also human activities contribute to PM2.5 concentration and allow some deposition and (re-) mobilisation at the first hours of the day and morning rush hour, respectively, while particle number concentration responds immediately to anthropogenic sources. PCA confirmed the dependence of particle number concentration also on meteorological variables, e.g. mixing layer height, wind speed or atmospheric pressure, showing the important influence of regional meteorology on local pollution conditions. Modena can be considered a representative test area of the effect of the meteorological regime for the Central Po Valley on atmospheric particle concentration patterns, characterised by steady high-background concentration.
2010
- Analysis of the air pollution climate at a central urban background site
[Articolo su rivista]
Bigi, Alessandro; R. M., Harrison
abstract
Measurements of air pollutants from a background site in central London are analysed. These comprise hourly data for CO, NO, NO2, O3, SO2 and PM10 from 1996 to 2008 and particle number count from 2001 to 2008. The data are analysed in terms of long-term trends, annual, weekly and diurnal cycles, and autocorrelation and cross-correlation functions. CO, NO and NO2 show a typical traffic-associated pattern with two daily peaks and lesser concentrations at the weekend. Particle number count and PM10 show a similar cycle, but with smaller amplitude. Ozone has an annual cycle with a maximum in May, influ- enced by the spring maximum in background ozone, but the diurnal and weekly cycles are dominated by losses through reaction with nitric oxide. Particle number count shows a minimum corresponding with maximum air temperatures in August, whereas the CO, NO NO2 and SO2 show a minimum in June/July. There is a lower particle count to NOx ratio at the background site compared to a central London kerbside site (Marylebone Road) and a seasonal pattern in particle count to NOx and PM10 ratios consistent with loss of nanoparticles by evaporation during atmospheric transport. Sulphur dioxide peaks in the morning in summer, but at midday in winter consistent with emissions from elevated sources mixing down from aloft as the diurnal mixed layer deepens. Implications for epidemiological studies of air quality and health are discussed. Sulphur dioxide, carbon monoxide, nitric oxide and nitrogen dioxide show clear downward trends over the measurement period, PM10 declines initially before levels stabilised, and ozone concentrations increased.
2010
- Improving of the thermal mapping of coastal and river waters obtained from satellite remote sensing
[Relazione in Atti di Convegno]
Teggi, Sergio; M. P., Bogliolo; Ghermandi, Grazia; Cecchi, Rodolfo; Bigi, Alessandro
abstract
The temperature of coastal and river water is very important in various areas of environmental concern. Very often, the heat released by human activities in water bodies is classified as a pollutant and it is subjected to regulatory. Remote sensing images acquired by the satellite sensor ASTER could be a very valuable tool in this area. Nevertheless, the spatial resolution (90 m) of this sensor in the thermal infrared is very important limiting factor for the compute of temperature of narrow watercourses or of coastal waters. In this work, an algorithm for the improvement of ASTER images acquired in the TIR based on information on the type of coverage of the area extracted from ASTER images acquired in the VIS-NIR and with spatial resolution varying between 15 m and 30 m. The algorithm produces a downscaling of the ASTER TIR images, from 90 m to 30 m, more complete than those obtainable by usual interpolation techniques. In this paper it is given a summary description of the structure of the algorithm followed by two applications on the coastal areas of the lagoon of Venice and the Po River delta.
2010
- Performance of Different Models to Evaluate Atmospheric Dispersion in Calm Wind Conditions
[Relazione in Atti di Convegno]
Ghermandi, Grazia; Teggi, Sergio; Fabbi, Sara; Bigi, Alessandro; Cecchi, Rodolfo
abstract
The study investigates the performance of different air pollution dispersion models in wind calm conditions. The models have been applied to two case studies: the cities of Modena and Reggio Emilia, both placed in the Po river valley (Northern Italy), an area characterized by prevailing weak winds conditions. The emission sources are the municipal waste incinerator of Modena and the Turbo Gas plant of Reggio Emilia. Total suspended particulate (TSP) concentration levels are estimated by three models: the gaussian Industrial Source Complex (ISC3) and WinDimula 3.0 models, and the langrangian particle model SPRAY. The performances of the models have been compared: ISC3 provides less reliable results, while SPRAY and WinDimula 3.0 have shown a good capability to describe a domain characterized by wind calm conditions and SPRAY simulation performs significantly better in the vicinity of the source.
2010
- Seasonal and weekly pattern of atmospheric particles in a urban background site in the Po valley, Italy
[Relazione in Atti di Convegno]
Ghermandi, Grazia; Bigi, Alessandro; Fabbi, Sara; Teggi, Sergio; Cecchi, Rodolfo
abstract
Combined measurements of number and weight particle concentration have been performed in an urban background site in the Po valley, Italy. Particle count measurements have been performed by Scanning Mobility Particle Sizer: number concentration for particles with diameter ranging between 10 to 700 nm are acquired each 120 seconds in the grounds of the University campus. PM2.5 is measured by TEOM-FDMS: the instrument estimates hourly particle weight concentration performing a correction for losses of semi-volatile particles collected on the sampling filter, whose temperature is kept at 30°C. The data analyzed in this study have been collected from February to August 2008. Daily and weekly pattern of total particle count, particle number size distribution and weight concentration have been investigated, along with meteorological data. Number concentration peaks resulted mostly related to morning and evening rush-hour traffic, particularly in winter; weight concentration resulted influenced both by anthropic activities and atmospheric dispersion conditions and shows a different diurnal pattern. Coagulation of finer particles occurs after evening rush-hour, mostly during wintertime. An analysis of the most and less polluted days of the investigated period has been performed, and the daily patterns of pollutants have been compared for both seasons.
2008
- PM2.5 monitoring in urban site (Modena, Italy) by TEOM
[Relazione in Atti di Convegno]
Ghermandi, Grazia; Bigi, Alessandro; Cecchi, Rodolfo; Teggi, Sergio; Fabbi, Sara
abstract
A Tapered Element Oscillating Microbalance (TEOM, Rupprecht & Patashnick Co.) has been installed at the Department of Mechanical and Civil Engineering at the University of Modena and Reggio-Emilia. The instrument allows automated and continuous measurement of weight concentration of airborne particulate matter; the inlet is provided with an EPA-standard PM10 head impactor and a PM2.5 sharp cut cyclone. The weighting microbalance is kept at 50°C in order to measure particulate matter in conditions of constant and low humidity and to avoid sampling artefacts from particle-bound water. Underestimation of PM concentration from TEOM measurements have been documented in the literature, due to particulate volatilisation caused by sensor heating. The instrumental equipment has been set up at a height of 9 m above the ground in the Faculty of Engineering building, with the inlet stretched 1 m outside the window and connected to the sensor unit by a 5 cm long conductive Tygon tube. From June 2007 continuous monitoring of PM2.5 has been ran, and since December 2007 the TEOM has been enhanced with a FDMS (Filter Dynamic Measurement System) device to correct PM underestimation of conventional TEOM. The University site can be considered representative of air quality of the residential background for the municipality of Modena: summer and autumn PM2.5 average hourly concentration resulted in 15.0 μg/m3 and 20.7 μg/m3 respectively. From recent FDMS measurements, underestimation of autumn PM can be roughly assessed in 33%.
2008
- Size distribution of sub micron atmospheric particles by DMA
[Relazione in Atti di Convegno]
Ghermandi, Grazia; Bigi, Alessandro; Cecchi, Rodolfo; Teggi, Sergio; Fabbi, Sara
abstract
A Differential Mobility Analyzer (DMA) has been installed at the Department of Mechanical and Civil Engineering at the University of Modena and Reggio-Emilia. The instrument allows automated and continuous measurement of number concentration of air suspended particulate matter within an electrical mobility diameter range of 10 to 800 nm. The DMA has been assembled at the Université Blaise Pascal in Clermont-Ferrand, France. The instrument is capable of operating in a scanning mode as a Scanning Mobility Particle Sizer (SMPS) and in stepwise mode as a Differential Mobility Particle Sizer (DMPS). In the SMPS mode measurements are completed in 2 minutes, whereas in DMPS mode, it takes about 10-12 minutes to complete a measurement over the complete diameter range. For this first testing period (March to May 2007) the DMA have been set up at a height of ~9m above the ground in the Faculty of Engineering building; the inlet have been equipped with a PM1 cyclone, stretched 1 m outside the window and shared with a TEOM instrument. Total particle number concentration and number size distribution spectra observed from March 19th to March 21st 2007 and from April 22nd to April 23rd 2007 are analysed in detail. Hourly variation of total particle concentration for the complete sampling period has been studied. Generally, concentration peaks resulted associated with rush hour during morning and with local meteorological conditions during evenings.
2006
- Knickpoints and hillslope failures: Interactions in a steady state experimental landscape
[Capitolo/Saggio]
Bigi, Alessandro; L. E., Hasbargen; A., Montanari; C., Paola
abstract
Hillslope stability depends strongly on local conditions, such as lithology and rock strength, degree of saturation, and critical slope angle. Common triggers for slope failure include severe storms, earthquakes, and removal of material from the toe of the hillslope. In this paper, we focus on the latter, in a model in which streams incise the toe and destabilize the hillslope. We investigate possible interactions between migrating knickpoints and hillslope failures in a small-scale, steadily eroding experimental landscape that experiences steady rainfall and base-level fall conditions. We monitored knickpoint propagation and hillslope failure activity with time lapse photography over a time period in which numerous knickpoints migrated through the drainage basin. We then investigated temporal and spatial relationships between hillslope failures and knickpoints and compared these results to Monte Carlo simulations of hillslope failure distributions. When focusing along a single channel, we found that, statistically (significant at the 98% confidence level), a greater number of failures occur downstream from a migrating knickpoint. These results highlight both the organized and random nature of hillslope and knickpoint interactions.
2006
- Uso del suolo e sistemazioni idraulico-forestali nell'alta valle del Reno: cento anni di trasformazioni ed interventi
[Relazione in Atti di Convegno]
D., Pavanelli; C., Cavazza; Bigi, Alessandro; M., Rigotti
abstract
Due fenomeni contrastanti e concomitanti si sono verificati nell’Appennino dagli anni ’50 ad oggi: da un lato l’esodo degli abitanti verso le città e la pianura, dall’altra la diffusione della meccanizzazione agricola. Le conseguenze sono evidenti soprattutto a livello di uso del suolo: l’abbandono dei terreni meno produttivi e più impervi è accompagnato all’estensivazione, introdotta dalla meccanizzazione. L’agricoltura, fino agli anni ’50, era praticata con mezzi che interessavano il suolo “in superficie”, inoltre erano eseguite sistematicamente le opere di regimazione delle acque. Tuttavia, l’apparente sostenibilità dell’uso del suolo risulta spesso in contrasto con la documentazione dell’epoca, che testimonia un grave dissesto idrogeologico, in aree intrinsecamente fragili. Questa situazione critica è confermata anche dalla realizzazione, a partire dai primi anni del 1900, di importanti e diffusi interventi di regimazione idraulica negli alvei torrentizi e di sistemazioni idraulico forestali sui versanti, oltre che da iniziative di tipo “politico-legislativo”. Nel presente lavoro si riporta il caso emblematico di studio: il Rio Maggiore nel bacino montano del fiume Reno, dove, a partire dall’inizio del 1900, sono state realizzate, in un periodo di circa 50 anni, intense opere di sistemazione idraulico-forestale sia negli alvei che sui versanti. Le immagini aeree attuali ci mostrano la copertura vegetale costituita in gran parte da prati stabili, arbusteti in evoluzione, formazioni boschive e seminativi, sebbene i versanti siano tuttora interessati da movimenti di massa, conseguenza della fragilità intrinseca del territorio, più che da un insufficiente regimazione idraulico forestale. L’erosione del suolo è limitata alle pendici del basso Appennino, dove l’agricoltura trova ancora riscontro economico. Gli alvei torrentizi sono sostanzialmente in equilibrio, dimostrando quindi il successo degli interventi effettuati, sennonché gran parte delle opere realizzate, richiedono interventi manutentori più o meno urgenti ed estesi.
2005
- A new indirect method to estimate suspended sediment concentration in a river monitoring programme
[Articolo su rivista]
D., Pavanelli; Bigi, Alessandro
abstract
In order to obtain realistic values of suspended sediment concentration (SSC), an ultrasonic flow meter and an automatic water sampler were installed at the basin outlet for three Reno tributaries (Bologna Apennine, Italy). The basins have a similar geological setting: in the Sillaro basin, however, clays represent the dominant feature; in the Lavino basin, sandstone and clay marl are widely present; and the main part of the Savena watershed is characterised by sandrock, pebbly sandstone and clay marls. These differences are recognisable in the particle size distribution of the suspended sediment samples collected in these basins. The aim of this work is to estimate the SSCs of river water samples with two indirect methods, turbidity measurement and free settleable solids in Imhoff cones, and the relations with suspended sediment concentration and particle size distribution. Alongside these investigations, laboratory analyses were performed in order to validate these methods under controlled conditions. The turbidity measurements were highly significant, but their reliability was influenced by the concentration and the particle size distribution. In order to estimate the SSCs, it was necessary to establish specific regression curves for each stream. The estimate of the SSC obtained through a free settleable solids analysis was not only reliable but also less sensitive to sample characteristics. The measure of the settleable solids after 1 and 24 h presented a constant relationship in all the samples from the three streams, due to the compaction of the sediment. The measure of the settleable solids after 24 h gave a better estimate of the SSC. This last method was shown to be inexpensive, fast, reliable and applicable to all the situations studied.
2005
- Indirect analysis methods to estimate suspended sediment concentration: reliability and relationship of turbidity and settleable solids
[Articolo su rivista]
D., Pavanelli; Bigi, Alessandro
abstract
A key element in a stream-monitoring programme for sediment transport is the choice of the measuring technique for suspended sediment concentration: this can highly affect both project costs and data reliability. The gravimetric method represents the standard analysis to directly measure suspended sediment concentration in a water sample. Indirect techniques are often employed for their inexpensiveness, although they need to be calibrated on gravimetric analysis results. In this study, the reliability of settleable solids in Imhoff cones was addressed as an alternative indirect method to estimate suspended sediment concentration (SSC), verifying the results with the turbidity measures of a laboratory nephelometer. The results show a high correlation of settled solids with suspended sediment concentration. Also, the results from the turbidimetric analysis showed a good correlation with SSC, but limited to water samples that did not need dilution. Measurements were repeated after storing the samples for 1 month: results exhibit an increase in turbidity and settleable solids, probably due to algae growth and anaerobic processes with the production of gases, causing an increase in matter. From our study, the Imhoff cone was shown to be a useful instrument to estimate suspended sediment concentration for the simplicity, the reliability and the low cost of their results. Our results prove how Imhoff cones are preferable to turbidimetric analysis to estimate SSC, specifically for highly turbid samples.
2005
- Suspended sediment transport monitoring: relationship between hydrological parameters and discharges
[Relazione in Atti di Convegno]
D., Pavanelli; Bigi, Alessandro
abstract
At the outlet of three different mountain basins (Sillaro, Lavino, Savena) we set up a flow meter in order to measure river stage and command a water sampler. Suspended sediment concentration (S.S.C) and turbidity are measured on the water samples collected. Precipitation height is calculated using data from rain gauges scattered across the basins. Hydraulic level and rainfall height are recorded every 30 minutes. The Sillaro Torrent has been monitored since April 1997, the Lavino Torrent since September 1998 and the Savena Torrent since October 2000. The parameters used in the analysis, calculated on a storm event basis, are as follows: rainfall height (P), maximum rainfall intensity (Imax), mean rainfall intensity (Iave), the product PImax, and the USLE rainfall erosion index (EI), average and maximum water flow (Qave and Qmax), the runoff coefficient, rainfall and discharge duration, and maximum and average suspended sediment yield. Initially, a multiregression analysis has been performed to compare the “sediment-based” with the other variables. For all the three basins, S.S.C and “sediment-based” variables better correlate to rainfall erosion index E.I. and other “rainfall-based” variables, whereas discharge is scarcely correlated to average S.S.C..
2004
- Analisi su modello fisico di possibili interazioni tra processi di evoluzione morfologica della rete drenante e frane sui versanti
[Relazione in Atti di Convegno]
Bigi, Alessandro; L., Hasbargen; A., Montanari; C., Paola
abstract
Il presente studio si propone di indagare, mediante esperimenti su modello fisico, alcuni dei legami che possono sussistere fra movimenti di frana sui versanti e processi di evoluzione morfologica della rete fluviale. In particolare si sono indagate le possibili interazioni tra le dinamiche di knickpoint e movimenti franosi, in un modello fisico costituito da un bacino sperimentale a scala ridotta, sottoposto ad erosione superficiale stazionaria. I knickpoint sono variazioni localizzate di pendenza o livello di fondo della rete idrografica superficiale, che tendono a risalire verso monte ad opera dell’erosione esercitata dalla corrente fluviale in corrispondenza della discontinuità topografica che ivi si verifica. Inducendo fenomeni di erosione localizzata, i knickpoint possono influire significativamente sulla evoluzione della morfologia dei versanti. Durante gli esperimenti eseguiti su modello fisico, si sono rilevate in dettaglio le modalità di propagazione dei knickpoint e di formazione dei movimenti di frana sui versanti, tramite fotografie scattate ad intervalli regolari, per un periodo sufficientemente lungo durante il quale si è osservata la risalita di numerosi knickpoint lungo la rete drenante. Si sono quindi investigate possibili interrelazioni fra la distribuzione spaziale di frane e knickpoint, verificandone la significatività mediante confronto fra le configurazioni osservate e quelle prospettate da distribuzioni casuali di movimenti franosi. I risultati ottenuti sembrano indicare la plausibilità di una relazione significativa tra le posizioni di knickpoint e movimenti di frana, relazione che si esplica in pratica con una maggiore instabilità dei versanti situati a valle di knickpoint in movimento.
2004
- L'azoto totale nelle torbide e relazioni con i parametri idrologici: primi dati
[Articolo su rivista]
L., Rubbi; L., Billi; D., Pavanelli; Bigi, Alessandro
abstract
Il trasporto torbido dei corsi d’acqua può essere considerato un indicatore dei fenomeni d’erosione del suolo che si manifestano sui versanti, nell’ambito del bacino. Il trasporto torbido è costituito da solidi in sospensione di granulometria variabile, dalle argille alle sabbie, in funzione dei parametri idraulici, litopedologici, vegetazionali del bacino. Numerose sono le indagini sui processi di trasporto che concordano nell’attribuire ai solidi sospesi il ruolo di veicolo per la migrazione degli agenti inquinanti e dei nutrienti . La concentrazione di tali sostanze, nei solidi in sospensione, può arrivare a diversi ordini di grandezza maggiori rispetto alla loro concentrazione nella frazione liquida, in fase disciolta. In particolare è stato provato il ruolo di vettore preferenziale degli aggregati di particelle fini come argilla e limo . Inoltre numerosi studi hanno provato come il tasso di azoto sia tendenzialmente in crescita negli acquiferi e nelle acque superficiali e come il ciclo naturale dell’azoto sia ormai modificato, a causa dei fertilizzanti e degli scarichi zootecnici e fognari . La necessità di dati sperimentali rende il monitoraggio fluviale un basilare tassello nell’ambito della gestione e della protezione dell’ambiente e, nel caso specifico, per il controllo dell’erosione del suolo, dell’inquinamento e dell’eutrofizzazione delle acque di superficie. Nel presente lavoro si riportano i primi risultati conseguiti, nell’ambito di un più ampio progetto, relativamente alle relazioni, in campioni di torbida fluviale, tra la concentrazione dell’azoto totale rilevato nei solidi sospesi, la concentrazione e la granulometria dei solidi sospesi. Si propone inoltre un primo tentativo di stima dell’azoto perso a livello di bacino, attraverso il vettore dei solidi sospesi fluviali.Lo studio si avvale di una rete di monitoraggio fluviale avviata nell’aprile del 1997 dal DEIAgra della Facoltà di Agraria col supporto dell’Autorità di Bacino del Reno, che vede operative le seguenti stazioni di rilevamento idrologico-torbidimetrico in continuo:T. Sillaro, con un bacino di 137,6 km2, avviata nell'aprile 1997, T. Lavino (82,6 km2), operativa dal settembre 1998,T. Savena (168,9 km2 ) dall’ottobre 2000.
2004
- Monitoraggio idrotorbidimetrico per la stima dell'erosione nel bacino montano del Reno
[Articolo su rivista]
D., Pavanelli; A., Pagliarani; Bigi, Alessandro
abstract
Il trasporto solido in sospensione dei corsi d’acqua, detto anche trasporto torbido, può essere considerato un valido indicatore dei fenomeni di erosione del suolo che avvengono ad opera delle acque dilavanti, sui versanti del bacino. L’erosione del suolo è inevitabilmente collegata all’uso agricolo di territori intrinsecamente fragili a causa, principalmente, dei fattori geolitologici e climatici: esemplare è il nostro Appennino ne è un caso esemplare. L’erosione provoca, da un lato, la degradazione del suolo, dall’altro è stata identificata come una delle maggiori cause di deterioramento della qualità delle acque superficiali e di perdita della diversità biologica. Inoltre, tra i più noti effetti del trasporto solido in sospensione si ricordano: i fenomeni legati alle dinamiche costiere, in particolare il ripascimento delle coste basse o l’erosione delle stesse, a seconda che il bilancio dei solidi a mare sia positivo o meno,l’inquinamento e l’eutrofizzazione dei corpi d’acqua superficiali: numerosi studi sui processi di trasporto concordano nell’attribuire ai solidi sospesi il ruolo di veicolo preferenziale per la migrazione di agenti inquinanti e nutrienti,la perdita di efficienza delle opere di approvvigionamento idrico,l’interrimento dei bacini artificiali e degli alvei, con la formazione dei fiumi ad alveo pensile, in pianura.La gravità potenziale di questi effetti ha portato alla promulgazione della legge quadro 183/89 “Norme per il riassetto organizzativo e funzionale della difesa del suolo” dove è stato fatto il primo tentativo di dare una sistemazione organica alla gestione delle acque sia in relazione alla difesa delle acque dall’inquinamento che al loro uso, che alla difesa del suolo, nell’ambito dell’unità del bacino idrografico considerato nel suo insieme di ecosistema naturale . Il controllo e contenimento di tali effetti rientrano nell’ambito della gestione e della protezione dell’ambiente.: Ppoiché una corretta regolamentazione dell’uso delle acque e del suolo passa necessariamente attraverso la conoscenza dei fenomeni fisici, la necessità di dati sperimentali rende il monitoraggio fluviale un basilare tassello nella gestione di unità territoriali complesse quali i bacini idrografici. Un programma di monitoraggio idrologico prevede necessariamente un numero consistente di anni di dati per poterne estrapolare delle considerazioni statisticamente affidabili, a causa sia della variabilità delle precipitazioni, e quindi dei deflussi liquidi e solidi, sia della specificità delle condizioni caratterizzanti ciascun bacino fluviale. Sulla base di tali presupposti si è avviato il monitoraggio del fiume Reno e di alcuni suoi affluenti principali.
2004
- Stima dell'erosione e bilancio dei solidi del Sillaro: applicazione del modello RUSLE e confronto con il monitoraggio del trasporto in sospensione
[Articolo su rivista]
G., Vianello; S., Lorito; D., Pavanelli; Bigi, Alessandro
abstract
L'erosione è un fenomeno complesso influenzato da fattori rilevanti quali il clima, il suolo, la morfologia, l'idrologia, la vegetazione e l'eccessiva antropizzazione del territorio da parte dell'uomo. Si stima che, allo stato attuale nella regione Mediterranea, l’erosione idrica possa provocare la perdita di 20-40 tonnellate/ettaro di suolo in un singolo nubifragio e oltre 100 tonnellate/ettaro in casi estremi (Morgan, 1992).Il seguente studio è volto a stimare la perdita di suolo del bacino montano del torrente Sillaro, nell’Appennino bolognese, attraverso due procedimenti:l’applicazione dell’equazione di perdita universale di suolo ( modello RUSLE) al bacino,il trasporto torbido rilevato nel periodo 1997-2004 alla chiusura del bacino montano.Come noto, il trasporto solido in sospensione dei corsi d’acqua, detto anche trasporto torbido, può essere considerato un valido indicatore dei fenomeni d’erosione che avvengono, ad opera delle acque dilavanti, sui versanti del bacino, quali i movimenti di massa, i calanchi e l’ erosione diffusa.La stima dell’erosione del suolo è stata ottenuta applicando la RUSLE implementata in un idoneo Sistema Informativo Geografico (GIS), che consente una gestione efficace della notevole mole di dati richiesti dal modello: piovosità, uso del suolo, caratteristiche pedologiche, e morfologia dei versanti. I risultati di stima della perdita di suolo a scala di bacino ottenuti attraverso le due procedure, modellistica e sperimentale, sono stati messi a confronto e hanno permesso di stimare il bilancio dei solidi a livello di bacino (sediment delivery).
2004
- Studio delle portate alla foce del Reno dal 1995 e validazione del modello di calcolo con misure di campo
[Articolo su rivista]
P., Mattarelli; D., Bottau; A., Pagliarani; Bigi, Alessandro
abstract
Il presente studio si inserisce nell’ambito di un più ampio progetto di ricerca che ha come oggetto lo studio idrologico e dei processi erosivi di alcuni degli affluenti principali del fiume Reno attraverso il monitoraggio in continuo degli afflussi, deflussi e trasporto torbido. A partire dal febbraio del 2003 si è aggiunto, il monitoraggio del fiume Reno a breve distanza dalla foce in Adriatico, nei pressi di Mandriole di Sant’Alberto (RA). Obiettivo specificatamente per la stazione alla foce del Reno, è lo studio del bilancio dei solidi trasportati a mare, in sospensione e sul fondo, in funzione del ripascimento delle coste. A tale fine si è posta l’esigenza di arrivare ad una stima quanto più affidabile della portata del Reno nella sezione monitorata, stima necessaria per arrivare al calcolo del deflusso torbido, vale a dire delle quantità di sedimenti in sospensione che arrivano mediamente ogni anno al mare.La stazione di misura è collocata sopra uno sbarramento costituito da cinque grandi luci regolate da paratoie, azionate in funzione della portata del fiume in modo da assicurare una quota idrometrica pressoché costante a monte della chiusa. Il calcolo della portata è complesso e mai affrontato organicamente, anche in conseguenza della geometria degli organi di regolazione, atta a consentire tanto il deflusso a battente quanto quello a stramazzo. Nel presente lavoro, si propone la metodologia di calcolo che, attraverso un programma realizzato appositamente, consente l’elaborazione automatica dei dati per la stima della portata.