Tracing the source of the atmospheric lead during Asian dust season in Korea

Abstract

Introduction The air condition in Korea is largely affected by atmospheric dust coming from China during Asian dust period. Ewing et al. [1] reported that the influence of Asian dust on atmospheric Pb in California was increased up to 93 % during spring. We measured Pb isotope ratios of aerosol in Korea to identify the source during Asian dust period.

Method During 2011 and 2012, 22 atmospheric dust samples were collected at the background air monitoring observatory near to Yellow Sea. The samples were acid digested with HNO3, HClO4 and HF. Anion exchange column separation was done to separate Pb from matrix. Pb isotope ratios were determined by Nu Plasma II MC-ICP-MS (Nu, U.K.) equipped with DSN-100 desolvating system. Mass bias correction was done by NIST997 Tl solution spiked into samples.

Result and discussion Pb isotope ratios determined in this study were 2.0654~2.1048 for 208Pb/206Pb and 0.8457~0.8657 for 207Pb/206Pb. Seasonal variations of Pb isotope ratios were not found. During fall, Pb isotope ratios were quite constant compared with the other period. The atmospheric dust collected during Asian dust period showed exceptional higest 208Pb/206Pb and 207Pb/206Pb ratios. This represents the influence from atmospheric Pb of which isotopic composition was charasterized by high 208Pb/206Pb and 207Pb/206Pb. According to Biscaye et al. [2], the 208Pb/206Pb and 207Pb/206Pb ratios of soil in Gobi dessert ranged 2.036~2.059 and 0.8258~0.8333, respectively. Therefore the increase in 207Pb/206Pb and 208Pb/206Pb ratios during Asian dust period was not resulted from input of natural Pb from Gobi dessert. The three isotope plot for 208Pb/206Pb vs. 207Pb/206Pb revealed that Pb emitted from coal combustion and refining of Pb in China were most likely the sources for atmospheric Pb in Korea during Asian dust period.

[1] Ewing et al. (2010) Environ. Sci. Technol. 44, 8911-8916. [2] Biscaye et al. (1997) J. Geophys. Res. 102 (12), 26765-26781.