Similarities and differences in PM₁₀ and PM_2.5 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 PM_2.5 (particle size smaller than 2.5 μm) and PM₁₀ (particle size smaller than 10 μm). The mean levels of PM_2.5 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 PM_2.5 (Pearson's coefficient r = 0.94) rather than PM₁₀ concentrations. The PM_2.5/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 PM_2.5 and PM₁₀. The PM_2.5/PM₁₀ ratios of anthropogenic element concentrations were much higher than ratios of earth crust element. As compared to PM₁₀, S and Pb in PM_2.5 had larger EFs, indicating that pollution elements were predominantly enriched in PM_2.5. Furthermore, a paired sample t-test confirmed similar sources of PM_2.5 and PM₁₀. Our study provides basic database to evaluate the heavy metal pollution status of atmospheric particulates in Chinese cities.