Gianni Formenton

Thirteen years of air pollution hourly monitoring in a large city: Potential sources, trends, cycles and effects of car-free days

Thirteen air pollutant concentrations were measured hourly for 13 years (2000-2013) at an urban background site of a large city in the eastern Po Valley (Italy) and results were chemometrically analysed. The pollutant list includes CO, NO, NO2, NOx, O3, SO2, benzene, toluene, ethylbenzene, o-, m- and p-xylenes and PM10, all known or suspected of having adverse effects on human health. The hourly data were statistically processed to detect the long-term trends in relation to the changes in the emission scenarios occurred in the last decade. The most probable emission sources and atmospheric photochemical processes were investigated by analyzing the seasonal, weekly, diurnal cycles of pollutants and the lagged correlations amongst pollutants. The role of micro-meteorological factors upon the air quality was assessed by analyzing the relationships with key weather parameters, while the location of the potential sources was studied by matching atmospheric circulation and pollution data through bivariate polar plots and conditional probability functions. In addition, a new statistical procedure is presented and tested to analyze the periods when common mitigation measures were adopted in the city (e.g., the total stop of traffic and car-free days) and to evaluate their real effect upon the air quality. By providing direct information on the levels and trends of key pollutants, this study finally enables some general considerations about air pollution in an important hotspot of Southern Europe, the eastern Po Valley, where the levels of some key pollutants are still far from meeting the EC limit and target values. It may help policy-makers to take successful mitigation measures.

Carbonaceous PM2.5 and secondary organic aerosol across the Veneto region (NE Italy)

Organic and elemental carbon (OC-EC) were measured in 360 PM2.5 samples collected from April 2012 to February 2013 at six provinces in the Veneto region, to determine the factors affecting the carbonaceous aerosol variations. The 60 daily samples have been collected simultaneously in all sites during 10 consecutive days for 6 months (April, June, August, October, December and February). OC ranged from 0.98 to 22.34 μg/m(3), while the mean value was 5.5 μg/m(3), contributing 79% of total carbon. EC concentrations fluctuated from 0.19 to 11.90 μg/m(3) with an annual mean value of 1.31 μg/m(3) (19% of the total carbon). The monthly OC concentration gradually increased from April to December. The EC did not vary in accordance with OC. However the highest values for both parameters were recorded in the cold period. The mean OC/EC ratio is 4.54, which is higher than the values observed in most of the other European cities. The secondary organic carbon (SOC) contributed for 69% of the total OC and this was confirmed by both the approaches OC/EC minimum ratio and regression. The results show that OC, EC and SOC exhibited higher concentration during winter months in all measurement sites, suggesting that the stable atmosphere and lower mixing play important role for the accumulation of air pollutant and hasten the condensation or adsorption of volatile organic compounds over the Veneto region. Significant meteorological factors controlling OC and EC were investigated by fitting linear models and using a robust procedure based on weighted likelihood, suggesting that low wind speed and temperature favour accumulation of emissions from local sources. Conditional probability function and conditional bivariate probability function plots indicate that both biomass burning and vehicular traffic are probably the main local sources for carbonaceous particulate matter emissions in two selected cities.

Air quality across a European hotspot: Spatial gradients, seasonality, diurnal cycles and trends in the Veneto region, NE Italy.

The Veneto region (NE Italy) lies in the eastern part of the Po Valley, a European hotspot for air pollution. Data for key air pollutants (CO, NO, NO2, O3, SO2, PM10 and PM2.5) measured over 7years (2008/2014) across 43 sites in Veneto were processed to characterise their spatial and temporal patterns and assess the air quality. Nitrogen oxides, PM and ozone are critical pollutants frequently breaching the EC limit and target values. Intersite analysis demonstrates a widespread pollution across the region and shows that primary pollutants (nitrogen oxides, CO, PM) are significantly higher in cities and over the flat lands due to higher anthropogenic pressures. The spatial variation of air pollutants at rural sites was then mapped to depict the gradient of background pollution: nitrogen oxides are higher in the plain area due to the presence of strong diffuse anthropogenic sources, while ozone increases toward the mountains probably due to the higher levels of biogenic ozone-precursors and low NO emissions which are not sufficient to titrate out the photochemical O3. Data-depth classification analysis revealed a poor categorization among urban, traffic and industrial sites: weather and urban planning factors may cause a general homogeneity of air pollution within cities driving this poor classification. Seasonal and diurnal cycles were investigated: the effect of primary sources in populated areas is evident throughout the region and drives similar patterns for most pollutants: road traffic appears the predominant potential source shaping the daily cycles. Trend analysis of experimental data reveals a general decrease of air pollution across the region, which agrees well with changes assessed by emission inventories. This study provides key information on air quality across NE Italy and highlights future research needs and possible developments of the regional monitoring network.

The dark side of the tradition: the polluting effect of Epiphany folk fires in the eastern Po Valley (Italy).

In the Veneto Region (Po Valley, Northeastern Italy) on the eve of Epiphany, an important religious celebration, during the night between January 5th and 6th thousands of folk fires traditionally burn wooden material. The object of this study is to characterize the 2013 episode, by monitoring the effects on the air quality in the regions lowlands. The daily concentrations of PM2.5 and PM10 exceeded 250 and 300 μg m(-3), respectively and the PM10 hourly values were above 600 μg m(-3) in many sites. The levels of total carbon, major inorganic ions, polycyclic aromatic hydrocarbons and biomass burning tracers (levoglucosan and K(+)) were measured in 84 samples of PM10 and 38 of PM2.5 collected at 32 sites between January 4th and 7th. Total carbon ranged from 11 μg m(-3) before the pollution episode to 131 μg m(-3) a day afterwards, K(+) from 0.6 to 5.1μg m(-3), benzo(a)pyrene from 2 to 23 ng m(-3), and levoglucosan from 0.5 to 8.3 μg m(-3). The dispersion of the particulate matter was traced by analyzing the levels of PM10 and PM2.5 in 133 and 51 sites, respectively, in the Veneto and neighboring regions. In addition to biomass burning the formation of secondary inorganic aerosol was revealed to be a key factor on a multivariate statistical data processing. By providing direct information on the effects of an intense and widespread biomass burning episode in the Po Valley, this study also enables some general considerations on biomass burning practices.

Source apportionment of PAHs and n-alkanes bound to PM1 collected near the Venice highway

n-Alkanes and polycyclic aromatic hydrocarbons (PAHs) bound to atmospheric particulate matter (PM1) were investigated in a traffic site located in an urban area of Venice Province (Eastern Po Valley, Italy) during the cold season. Considering the critical situation affecting the Veneto Region concerning the atmospheric pollution and the general lack of information on PM1 composition and emission in this area, this experimental study aims at determining the source profile, their relative contributions and the dispersion of finer particles. Four sources were identified and quantified using the Positive Matrix Factorization receptor model: (1) mixed combustions related to the residential activities, (2) agricultural biomass burning in addition to the resuspension of anthropogenic and natural debris carried by the wind, (3) gasoline and (4) diesel traffic-related combustions. The role of local atmospheric circulation was also investigated to identify the pollutant sources.