Chemical composition of PM2.5 and meteorological impact among three years in urban Shanghai, China

Air pollution is a major environmental concern in Yangtze River Delta (YRD) region in East China. Here we presented 3-year on-line measurements of PM2.5 chemical components from January 2011 to December 2013 at an urban site in Shanghai of YRD region. The 3-year average of PM2.5 mass concentration was 47 μg/m3, 34% higher than the second grade of China National Ambient Air Quality Standards for PM2.5 annual concentration. Monthly patterns of PM2.5 mass concentration and chemical components were observed, which were mainly influenced by the meteorological conditions through long-range transport and ventilation, and by the secondary species transformation. Significant year-to-year differences of PM2.5 characterization were observed during 2011–2013, and it can be attributed to the differences of regional transport as well as the wet deposition by precipitation. Generally, air mass from the western YRD region caused the most polluted air in Shanghai, while, air masses from the East China Sea had the lowest particle pollution because of marine time background air, and those from the surrounding region of Bo Hai in the north of China caused the moderate PM2.5 pollution in Shanghai. A large decrease of PM2.5 mass concentration, ∼44%, was observed for the fifteen years. In terms of chemical components, persistent decrease was observed for element carbon with a decrease of 70% but not for organic carbon, and the significant decrease of secondary inorganic ions was observed before year of 2008 but the persistent increase started after that.