Concentrations and origins of atmospheric lead and other trace species at a rural site in northern China

Abstract

In this study we analyze the ambient levels of lead and other trace species in the bulk aerosol samples from a rural site ∼70 km ESE of Beijing in spring 2005. Lead (0.28 ± 0.24 μg/m3, average ± standard deviation), along with several pollution‐related trace elements, was enriched by over 100 fold relative to the Earth’s crust. The ambient lead levels showing large synoptic variations were well‐correlated with other anthropogenic pollutants (e.g., CO and SO2). The Unmix receptor model resolved four factors in the aerosol composition data: a biomass burning source, an industrial and coal combustion source, a secondary aerosol source, and a dust source. The first three sources were strongest in weak southerly winds ahead of cold fronts, while the dust source peaked in strong northerly winds behind cold fronts. The second source, primarily representing emissions from industrial processes and relatively small‐scale coal burning such as in home and institutional heating, was identified as the main source of ambient lead in this study. Mobile sources might also contribute to this factor, but there was no distinct evidence of emissions due to combustion of leaded gasoline, despite a correlation between lead and CO. Potential source contribution function, calculated from backward trajectories and aerosol composition, further reveals that lead observed in this study was predominantly from the populated and industrialized areas to the south and SW of Xianghe, rather than Beijing to the west. Our results and several recent studies show that the lead levels in suburban areas near big cities in China, although generally lower than those in industrial districts and urban areas, are substantial (near or above 0.15 μg/m3). More extensive studies on airborne lead and its emission sources in China are called for.