Chemical characterization and sources of PM_2.5 at 12-hr resolution in Guiyang, China

The increasing emission of primary and gaseous precursors of secondarily formed atmospheric particulate matter due to continuing industrial development and urbanization are leading to an increased public awareness of environmental issues and human health risks in China. As part of a pilot study, 12-hr integrated fine fraction particulate matter (PM_2.5) filter samples were collected to chemically characterize and investigate the sources of ambient particulate matter in Guiyang City, Guizhou Province, southwestern China. Results showed that the 12-hr integrated PM_2.5 concentrations exhibited a daytime average of 51 ± 22microg·m^-3 (mean ± standard deviation) with a range of 17-128microg·m^-3 and a nighttime average of 55 ± 32microg·m^-33 with a range of 4-186 microg·m^-3. The 24-hr integrated PM_2.5 concentrations varied from 15 to 157 microg·m-3, with a mean value of 53 ± 25 microg·m^-3, which exceeded the 24-hr PM_2.5 standard of 35microg·m^-3 set by USEPA, but was below the standard of 75microg·m^-3, set by China Ministry of Environmental Protection. Energy-dispersive X-ray fluorescence spectrometry (XRF) was applied to determine PM_2.5 chemical element concentrations. The order of concentrations of heavy metals in PM_2.5 were iron (Fe) > zinc (Zn) > manganese (Mn) > lead (Pb) > arsenic (As) > chromium (Cr). The total concentration of 18 chemical elements was 13 ± 2 microg·m^-3, accounting for 25% in PM_2.5, which is comparable to other major cities in China, but much higher than cities outside of China.