Characteristics, Secondary Formation and Regional Contributions of PM_2.5 Pollution in Jinan during Winter

Air pollution is an increasing threat to human health in China. In this study, daily PM10 and PM2.5 samples were collected simultaneously at the Jinan Environmental Monitoring Station (EMS)in Jinan, China from 15 November 2016 to 15 March 2017. The aim of this work was to improve the understanding of the characteristics and sources of air particles and determine different levels of PM2.5 pollution and its constituent elements, water-soluble ions and carbonaceous species. Nitrate (NO3-), organic materials (OM) and sulfate (SO42-) were identified as the three main components of PM2.5 pollution. With increasing pollution level, the contributions of SO42-, NO3- and NH4+ increased at greater rates, unlike that of OM. The proportion of SO42- exceeded that of NO3- and became predominant in severe PM2.5 pollution (SP; 250 mu g m(-3) <= PM2.5 <= 500 mu g m(-3)). This work demonstrates that SO42- has a dominant role in SP level and, consequently, requires greater research attention. It is demonstrated that relative humidity (RH) enhances the rate of sulfate formation more than that of nitrate. Therefore, under the current Chinese emergency response measures, it is necessary to further reduce emissions of SO2 and NO2. Four clusters of backward trajectories identified dominant pollution vectors originating from highly industrialized areas that exacerbate the poor air quality in Jinan. It is, therefore, necessary to undertake regional control measures to reduce pollutant emissions.