Analysis of 20-year air quality trends in the city of Florence (Italy)

Today, about 80% of people in developed countries live in cities, while urbanization is rapidly growing in the developing countries. Due to high spatial density of human activities, cities exhibit high air pollutant concentrations, that impact human health risk across a wide range of socioeconomic and/or climatic features. In EU, and particularly in Italy, a significant percentage of urban population is exposed to pollutant concentrations above the reference levels. In this paper we report a 20-year (1993–2012) air quality analysis in the city of Florence (Italy). Concentrations of main atmospheric pollutants have been addressed: CO, NO2, NOx, SO2, PM10, and O3. Hourly (daily for PM10) observations collected by all the stations of Florence air quality monitoring network since the beginning of its activity (i.e., 1993) have been processed. Monitoring stations falling into each area category (urban, suburban and rural) and source category (traffic, industry and background) have been considered. Trends of annual mean concentrations of all pollutants observed at both central and periferic stations have been analysed, along with occurrences of concentrations exceeding legal thresholds. Meteorological parameters as wind speed and prevailing direction, air temperature, solar radiation, and stability class measured at a station located in the city centre (i.e., the Ximeniano Observatory) have been considered to depict a full description of Florence meteorological conditions. Trends of annual pollutant inventorial emission data in the province of Florence, disaggregated by SNAP category, have been also analysed and related to pollutant concentrations by means of a linear multi-regressive framework to assess the significance of their contribution to annual concentration trends.