Chemical composition and source apportionment of PM sub(10) and PM sub(2.5) in different functional areas of Lanzhou, China

To elucidate the air pollution characteristics of northern China, airborne PM sub(10) (atmospheric dynamic equivalent diameter less than or equal to 10 mu m) and PM sub(2.5) (atmospheric dynamic equivalent diameter less than or equal to 2.5 mu m) were sampled in three different functional areas (Yuzhong County, Xigu District and Chengguan District) of Lanzhou, and their chemical composition (elements, ions, carbonaceous species) was analyzed. The results demonstrated that the highest seasonal mean concentrations of PM sub(10) (369.48 mu g/m super(3)) and PM sub(2.5) (295.42 mu g/m super(3)) were detected in Xigu District in the winter, the lowest concentration of PM sub(2.5) (53.15 mu g/m super(3)) was observed in Yuzhong District in the fall and PM sub(10) (89.60 mu g/m super(3)) in Xigu District in the fall. The overall average OC/EC (organic carbon/elemental carbon) value was close to the representative OC/EC ratio for coal consumption, implying that the pollution of Lanzhou could be attributed to the burning of coal. The content of SNA (the sum of sulfate, nitrate, ammonium, SNA) in PM sub(2.5) in Yuzhong County was generally lower than that at other sites in all seasons. The content of SNA in PM sub(2.5) and PM sub(10) in Yuzhong County was generally lower than that at other sites in all seasons (0.24-0.38), indicating that the conversion ratios from precursors to secondary aerosols in the low concentration area was slower than in the area with high and intense pollutants. Six primary particulate matter sources were chosen based on positive matrix factorization (PMF) analysis, and emissions from dust, secondary aerosols, and coal burning were identified to be the primary sources responsible for the particle pollution in Lanzhou.