Long term trends and patterns of atmospheric pollutants in Modena, Po valley, Italy

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.