Similarities and differences in PM10 and PM2.5 concentrations, chemical compositions and sources in Hefei City, China.

Atmospheric particulates were sampled in Hefei City, China from October 2016 to January 2017 to compare chemical compositions and sources of PM2.5 (particle size smaller than 2.5 μm) and PM10 (particle size smaller than 10 μm). The mean levels of PM2.5 and PM10 were 81 and 109 μg/m3, which are higher than the health threshold levels regulated by national and international standards. During the sampling period, AQI (Air Quality Index) was strongly correlated with PM2.5 (Pearson's coefficient r = 0.94) rather than PM10 concentrations. The PM2.5/PM10 ratios were approximately 0.7, revealing the characteristics of fine particle pollution. Pollution elements (S, Zn, Cu and Pb) took up a large proportion of the composition and had high enrichment factors of 437, 385, 20 and 53, respectively, in PM10. Coal combustion and high-tech manufacture industry discharges were suggested to be the main pollution sources of both PM2.5 and PM10. The PM2.5/PM10 ratios of anthropogenic element concentrations were much higher than ratios of earth crust element. As compared to PM10, S and Pb in PM2.5 had larger EFs, indicating that pollution elements were predominantly enriched in PM2.5. Furthermore, a paired sample t-test confirmed similar sources of PM2.5 and PM10. Our study provides basic database to evaluate the heavy metal pollution status of atmospheric particulates in Chinese cities.