Seasonal variation in trace element concentrations and Pb isotopic composition of airborne particulates during Asian dust and non-Asian dust periods in Daejeon, Korea

Trace element contamination (As, Cd, Cr, Co, Cu, Mo, Ni, Pb, S, Zn, and Zr) in both Asian dust (AD) and non-Asian dust (NAD) periods taken from Daejeon, Korea, in 2008 was examined, and the pollution sources were evaluated based on the Pb stable isotope. Additionally, temporal variation in the trace element concentrations of total suspended particulate matter, PM<inf>10</inf> and PM<inf>2.5</inf>, was evaluated in 14 samples for AD and 46 samples for NAD collected from March 2007 to November 2008. Patterns showed that the monthly mean concentrations of trace elements in winter were 2–13 times higher than those in other seasons. In contrast, the monthly mean concentrations of sulfur were the highest in the summer monsoon season. Distinct temporal patterns were observed in the monthly mean concentrations of trace elements, due mainly to high coal combustion in China. These results were supported by the ²⁰⁶Pb/²⁰⁷Pb ratios of AD and NAD, which were identical or similar to those of the airborne particles in certain heavily industrialized Chinese cities and coal and coal combustion dust of China. The Pb isotopic composition in the particulate matter of NAD showed lower ²⁰⁶Pb/²⁰⁷Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁶Pb/²⁰⁴Pb ratios in the autumn, winter, and spring seasons, showing the influence of Pb from the heavily industrial cities of China, and higher values in the summer, indicating the dilution and/or mixing effect of the marine air mass from the south.