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Pagina personale di Alessandro BIGI

Dipartimento di Ingegneria "Enzo Ferrari"

B. Arvani, R.B. Pierce, S. Teggi, A. Bigi, G. Ghermandi ( 2013 ) - Implementation of IMAPP/IDEA-I over the Po Valley region, northern Italy, for air quality monitoring and forecasting (T.D. Lekkas - Proceedings of the 13th International Conference on Environmental Science and Technology - Global-NEST Athens GRC) - n. volume CEST2013_0572 [Contributo in Atti di convegno - Relazione in Volume di Atti di Convegno]
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.

A. Bigi,G. Ghermandi,R. M. Harrison ( 2012 ) - Analysis of the air pollution climate at a background site in the Po valley - JOURNAL OF ENVIRONMENTAL MONITORING - n. volume 14 - pp. da 552 a 563 ISSN: 1464-0325 [Articolo su rivista - Articolo su rivista]
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.

S. Teggi, G. Ghermandi, S. Fabbi, A. Bigi, M. Vinceti, C. Malagoli ( 2012 ) - GIS methods for health and environmental monitoring and assessment - Sustainable Techonolgy for Environmental Protection - ANDIS Milano ITA) - pp. da 1 a 4 ISBN: 9788890355721 [Contributo in Atti di convegno - Relazione in Volume di Atti di Convegno]
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.

A. Bigi, G. Ghermandi, R. Cecchi ( 2012 ) - Long term trends and patterns of atmospheric pollutants in Modena, Po valley, Italy - Sustainable Techonolgy for Environmental Protection - ANDIS Milano ITA) - pp. da 1 a 8 ISBN: 9788890355721 [Contributo in Atti di convegno - Relazione in Volume di Atti di Convegno]
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.

G. Ghermandi, S. Teggi, S. Fabbi, A. Bigi, R. Cecchi ( 2012 ) - Model comparison in simulating the atmospheric dispersion of a pollutant plume in low wind conditions. - INTERNATIONAL JOURNAL OF ENVIRONMENT AND POLLUTION - n. volume 48 Nos. 1/2/3/4 - pp. da 69 a 77 ISSN: 1741-5101 [Articolo su rivista - Articolo su rivista]
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.

A. Bigi, G. Ghermandi ( 2012 ) - Statistical analysis of surface atmospheric pollutant measurement series for various sites across the Po valley - Sustainable Techonolgy for Environmental Protection - ANDIS Milano ITA) - pp. da 1 a 4 ISBN: 9788890355721 [Contributo in Atti di convegno - Relazione in Volume di Atti di Convegno]
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.

G. Ghermandi, S. Teggi, S.Fabbi, A. Bigi, M. M. Zaccanti ( 2012 ) - Tri-generation power plant and conventional boilers: pollutant flow rate and atmospheric impact of stack emissions - Sustainable Techonolgy for Environmental Protection - ANDIS Milano ITA) - pp. da 1 a 8 ISBN: 9788890355721 [Contributo in Atti di convegno - Relazione in Volume di Atti di Convegno]
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.

G. Ghermandi, S. Teggi, S. Fabbi, A. Bigi, M. M. Zaccanti ( 2011 ) - Atmospheric impact of power plant stack emissions - HARMO14 - Environmental Technology Laboratory, Department of Mechanical Engineering, University of West Macedonia Kozani GRC) - pp. da 240 a 244 ISBN: 9789608965065 [Contributo in Atti di convegno - Relazione in Volume di Atti di Convegno]
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.

A. Bigi,G. Ghermandi ( 2011 ) - Particle number size distribution and weight concentration of background urban aerosol in a Po valley site - WATER AIR AND SOIL POLLUTION - n. volume 220 - pp. da 265 a 278 ISSN: 0049-6979 [Articolo su rivista - Articolo su rivista]
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.

A. Bigi,R. M. Harrison ( 2010 ) - Analysis of the air pollution climate at a central urban background site - ATMOSPHERIC ENVIRONMENT - n. volume 44 - pp. da 2004 a 2012 ISSN: 1352-2310 [Articolo su rivista - Articolo su rivista]
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.

S. Teggi, M.P. Bogliolo, G. Ghermandi, R. Cecchi, A. Bigi ( 2010 ) - Improving of the thermal mapping of coastal and river waters obtained from satellite remote sensing ( - X Simpósio Ítalo-Brasileiro de Engenharia Sanitária e Ambiental Waste Management: Opportunities and Challenges - ABES – Associação Brasileira de Engenharia Sanitária e Ambiental BRASILE BRA) - n. volume [Abstract in Atti di convegno - Abstract in Volume di Atti di Convegno ]
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.

S. Teggi, M. Bogliolo, G. Ghermandi, R. Cecchi, A. Bigi ( 2010 ) - Improving of the thermal mapping of coastal and river waters obtained from satellite remote sensing - X Sibesa - Simposio Italo-Brasileiro de Engenharia Sanitaria e Ambiental - ABES – Associação Brasileira de Engenharia Sanitária e Ambiental. Rio de Janeiro, Brasil BRA) - pp. da 1 a 8 ISBN: 9788570221674 [Contributo in Atti di convegno - Relazione in Volume di Atti di Convegno]
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.

G. Ghermandi, S. Teggi, S. Fabbi, A. Bigi, R. Cecchi ( 2010 ) - Performance of Different Models to Evaluate Atmospheric Dispersion in Calm Wind Conditions - HARMO13 - ARIA Technologies Boulogne Billancourt FRA) - pp. da 105 a 109 ISBN: 9782868150622 [Contributo in Atti di convegno - Relazione in Volume di Atti di Convegno]
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.

G. Ghermandi,A. Bigi,S. Fabbi,S. Teggi,R. Cecchi ( 2010 ) - Seasonal and weekly pattern of atmospheric particles in a urban background site in the Po valley, Italy - X Sibesa - Simposio Italo-Brasileiro de Engenharia Sanitaria e Ambiental - ABES – Associação Brasileira de Engenharia Sanitária e Ambiental Rio de Janeiro, Brasil BRA) - pp. da 1 a 7 ISBN: 9788570221674 [Contributo in Atti di convegno - Relazione in Volume di Atti di Convegno]
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.

G. Ghermandi,A. Bigi,R. Cecchi,S. Teggi,S. Fabbi ( 2008 ) - PM2.5 monitoring in urban site (Modena, Italy) by TEOM - International Symposium on Sanitary and Environmental Engineering - ANDIS Florence, Italy ITA) - pp. da 1 a 6 ISBN: 9788890355707 [Contributo in Atti di convegno - Relazione in Volume di Atti di Convegno]
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%.

G. Ghermandi,A. Bigi,R. Cecchi,S. Teggi,S. Fabbi ( 2008 ) - Size distribution of sub micron atmospheric particles by DMA - International Symposium on Sanitary and Environmental Engineering - ANDIS Florence, Italy ITA) - pp. da 1 a 5 ISBN: 9788890355707 [Contributo in Atti di convegno - Relazione in Volume di Atti di Convegno]
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.

A. Bigi, L. E. Hasbargen, A. Montanari, C. Paola ( 2006 ) - Knickpoints and hillslope failures: Interactions in a steady state experimental landscape (Willett, S.D., Hovius, N., Brandon, M.T., Fisher, D.M. - Tectonics, climate, and landscape evolution - Geological Society of America Boulder, CO USA) - n. volume Special Paper 398 - pp. da 295 a 307 ISBN: 9780813723983 [Contributo in volume (Capitolo o Saggio) - Capitolo/Saggio con ISBN]
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.

D. Pavanelli, C. Cavazza, A. Bigi, M. Rigotti ( 2006 ) - Uso del suolo e sistemazioni idraulico-forestali nell'alta valle del Reno: cento anni di trasformazioni ed interventi (D'Agostino, V., Fattorelli, S. - Quaderni di Idronomia Montana - Nuova Bios Cosenza ITA) - n. volume 26 - pp. da 489 a 502 ISBN: 9788860930095 [Contributo in Atti di convegno - Relazione in Volume di Atti di Convegno]
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.

D. Pavanelli, A. Bigi ( 2005 ) - A new indirect method to estimate suspended sediment concentration in a river monitoring programme - BIOSYSTEMS ENGINEERING - n. volume 92 - pp. da 513 a 520 ISSN: 1537-5110 [Articolo su rivista - Articolo su rivista]
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.

D. Pavanelli,A. Bigi ( 2005 ) - Indirect analysis methods to estimate suspended sediment concentration: reliability and relationship of turbidity and settleable solids - BIOSYSTEMS ENGINEERING - n. volume 90 - pp. da 75 a 83 ISSN: 1537-5110 [Articolo su rivista - Articolo su rivista]
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.

D. Pavanelli,A. Bigi ( 2005 ) - Suspended sediment transport monitoring: relationship between hydrological parameters and discharges - AIIA2005: VII convegno nazionale Associazione Italiana Ingegneria Agraria - GeoGrafica Catania, Italy ITA) - pp. da 1 a 12 ISBN: 9788890186004 [Contributo in Atti di convegno - Relazione in Volume di Atti di Convegno]
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..

A. Bigi,L. Hasbargen,A. Montanari,C. Paola ( 2004 ) - Analisi su modello fisico di possibili interazioni tra processi di evoluzione morfologica della rete drenante e frane sui versanti - XXIX convegno di idraulica e costruzioni idrauliche - BIOS Trento, Italy ITA) - n. volume 1 - pp. da 373 a 380 ISBN: 9788877403827 [Contributo in Atti di convegno - Relazione in Volume di Atti di Convegno]
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.

L. Rubbi,L. Billi,D. Pavanelli,A. Bigi ( 2004 ) - L'azoto totale nelle torbide e relazioni con i parametri idrologici: primi dati - ARPA RIVISTA - n. volume 6 - pp. da 24 a 27 ISSN: 1129-4922 [Articolo su rivista - Articolo su rivista]
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.

D. Pavanelli,A. Pagliarani,A. Bigi ( 2004 ) - Monitoraggio idrotorbidimetrico per la stima dell'erosione nel bacino montano del Reno - ARPA RIVISTA - n. volume 6 - pp. da 3 a 7 ISSN: 1129-4922 [Articolo su rivista - Articolo su rivista]
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.

G. Vianello, S. Lorito, D. Pavanelli, A. Bigi ( 2004 ) - Stima dell'erosione e bilancio dei solidi del Sillaro: applicazione del modello RUSLE e confronto con il monitoraggio del trasporto in sospensione - ARPA RIVISTA - n. volume 6 - pp. da 21 a 23 ISSN: 1129-4922 [Articolo su rivista - Articolo su rivista]
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).

P. Mattarelli,D. Bottau,A. Pagliarani,A. Bigi ( 2004 ) - Studio delle portate alla foce del Reno dal 1995 e validazione del modello di calcolo con misure di campo - ARPA RIVISTA - n. volume 6 - pp. da 28 a 32 ISSN: 1129-4922 [Articolo su rivista - Articolo su rivista]
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.