Temporal characteristic and source analysis of PM2.5 in the most polluted city agglomeration of China

Abstract

The most seriously PM2.5 polluted city agglomeration has been identified by using the spatial autocorrelation model and the clustering analysis methods. The results indicated that cities which had heaviest pollution of PM2.5 were mainly located in the North China Plain (NCP) including Beijing, Tianjin, Shandong province, Henan province and Hebei province. Monthly means of PM2.5 in the most seriously polluted city agglomeration presented a U-sharp pattern, with a downward trend from January to March, basically stable but a slightly decreasing trend from April to September, and a sharply increasing trend from October to December. Serious pollution of PM2.5 in the heating season, mostly during the wintertime, might be caused by the direct emissions and secondary formation of PM2.5 accompanied by the combustion of biomass and fossil fuels for residential heating. According to the results of potential source contribution function (PSCF) calculations, the northern cities of the NCP (Beijing, Tianjing and cities of Hebei Privince) tended to be more influenced by the air masses originated locally during the heating season, while the southern cities of the NCP (cities of Shandong Province and northern Henan Province) were influenced not only by air masses originated locally, but also by air masses originated from adjacent Anhui Province and Jiangsu Province. Extraneous polluted air masses might be the main cause of the high levels of PM2.5 found in northern Henan.