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

Abstract

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 10 and PM 2.5 , 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 206 Pb/ 207 Pb 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 206 Pb/ 207 Pb, 207 Pb/ 204 Pb, and 206 Pb/ 204 Pb 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.

Lead chromate detected as a source of atmospheric Pb and Cr (VI) pollution

“…The low detection rate of Pb-containing particles (i.e., 10 of about 800 individual particles in this study; 7 of 950 in Seoul24; Supplementary Fig. 1), despite the high levels of Pb in the dust dry deposition17, also implies the presence of Pb in the dust dry deposition in various forms, which cannot be observed under SEM-EDS probably because they were not present in discrete mineral phases. Besides, the speciation of PbCrO 4 and non-detection of PbCO 3 and PbSO 4 within the black carbon matrix by using SADP in this study implies that the sequential extraction analysis is not a perfect tool to determine the speciation.…”

“…The mean concentration of chromium in AD and NAD samples ranged from 94 μg/g (PM 10 ) to 381 μg/g (PM 2.5 ) and from 42 μg/g (PM 10 ) to 232 μg/g (PM 2.5 ), respectively7. The lead and chromium levels did not show a distinct annual variation in 2007–2008, but gradually increased from summer to winter and remained at a relatively high level in the spring1. Both AD and NAD samples showed high levels of Pb and Cr17.…”

“…The lead and chromium levels did not show a distinct annual variation in 2007–2008, but gradually increased from summer to winter and remained at a relatively high level in the spring1. Both AD and NAD samples showed high levels of Pb and Cr17. These high levels of lead and chromium in airborne particulates are of great concern due to their negative impacts on air quality and human health.…”

“…High levels of Pb and Cr and their seasonal variations are detected in the air in Korea12, China345 and Japan6. In the Korean city of Daejeon (Fig.…”

“…For the identification of mineral phases, selected area diffraction patterns (SADPs) were obtained in TEM (transmission electron microscope). In Table 1, AD samples were collected when the Korean Meteorological Research Institute (METRI) issued an AD warning, while NAD samples were collected in spring and winter to avoid the rainy season17. All the samples were collected at 13.2 m elevation on the roof of a building of the Korea Institute of Geoscience and Mineral Resources (KIGAM).…”