Chemical characteristics and source apportionment of PM_(10) during Asian dust storm and non-dust storm days in Beijing

摘要

To study the chemical characteristics of Asian dust storm, airborne particulate matter PM_(10) (particles with aerodynamic diameter smaller than 10 μm) was collected at two sites in Beijing from March to May 2012. Water soluble ions, metals, organic carbon and elemental carbon were analyzed. Two dust storm (DS) samples were also collected during the sampling period on March 28th (DS1) and April 28th (DS2). Backward trajectory results showed that both events were originated from Inner Mongolia and Mongolia. A receptor model, positive matrix factorization (PMF) was applied to calculate the soil emission differences between DS and non-DS days. Five emission sources were identified that contribute to PM_(10) including soil dust, vehicular emission, industrial emission, metal processing and secondary ions. The PMF estimated contributions of dust aerosols to PM_(10) were in the range of 31%-40% during DS days, which were far greater than that contribution (10%-20%) from local soil dust only during non-DS days. Furthermore, lead isotopic composition analyses in PM_(10) in Beijing and the soil samples from Inner Mongolia Plateau and Zhangbei Plateau were conducted. Higher lead isotopic ratios (~(206)Pb/~(207)Pb, ~(206)Pb/~(208)Pb) in PM_(10) were observed in DS days than non-DS days, and those ratio compositions were found to be similar to those observed in the dry lakebed soil samples collected from Inner Mongolia Plateau and Zhangbei Plateau, which indicate that the dry lakebed region served as a dust transport pathway of those two DS events.