Alessandro Bigi

Long-term trend and variability of atmospheric PM 10 concentration in the Po Valley

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.

Tri-generation power plant and conventional boilers: pollutant flow rate and atmospheric impact of stack emissions

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, is studied and compared with 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.

Micro-scale simulation of atmospheric emissions from power-plant stacks in the Po Valley

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.

Model comparison in simulating the atmospheric dispersion of a pollutant plume in low wind conditions

This study investigates the performance of different air pollution dispersion models in low wind conditions. The models have been applied to two sites frequently characterised by weak winds: the cities of Modena and Reggio Emilia, in the Po River Valley (Northern Italy). The emission sources are the municipal waste incinerator (Modena) and a turbogas plant (Reggio Emilia). Total Suspended Particulate (TSP) concentration levels are estimated by the gaussian Industrial Source Complex (ISC3) and WinDimula 3.0 models, and the Langrangian model SPRAY. WinDimula 3.0 and SPRAY simulations perform significantly better than ISC3, SPRAY shows the highest reliability close to the source.

Remote sensing and GIS for the modeling of persistent organic pollutant in the marine environment

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.

Performance of NO, NO 2 low cost sensors and three calibrationapproaches within a real world application

approaches within a real world application Alessandro Bigi1, Michael Mueller2, Stuart K. Grange3, Grazia Ghermandi1, and Christoph Hueglin2 1‘Enzo Ferrari’ Department of Engineering, University of Modena and Reggio Emilia, Modena, Italy 2Empa, Swiss Federal Institute for Materials Science and Technology, Duebendorf, Switzerland 3Wolfson Atmospheric Chemistry Laboratory, University of York, York, United Kingdom Correspondence to: Alessandro Bigi (alessandro.bigi@unimore.it)