Abstract

In order to identify the Pb pollution and its sources in continental shelf and slope areas, Pb concentration and Pb isotope ratios (²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb) were determined for 6 box corer sediments collected from the southern East/Japan Sea. Pb concentration, and ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb ratios were constant at around 25±5 ppm and 0.842 and 2.092 from 1700 to 1930 year, respectively and increased steadily up to 40±5 ppm and 0.867 and 2.123 at the beginning of 1990s', respectively. The increase of concentration and isotope ratios in the labile fraction (leached by 2M HCl+0.5M HNO₃) explains their increase in bulk sediments, while Pb concentration and isotope ratios in the residual fraction were nearly constant during 300 yrs. Temporal variation of Pb isotope ratios was explained by simple two end-members mixing of geo-genic and anthropogenic sources because isotope ratios and the inverse of Pb concentration showed the good linear relationships. Using Pb isotope ratios, we can constrain two Pb sources in the study area. The one is atmospheric particulates, compared with mean values of isotope ratios in atmospheric particulates collected at Jeju and Oki islands, based on the history of Pb emmission in Korea and China, and judged by oceanographic processes capable of homogenizing many sources. The other is local sources related to iron mills, refineries of Pb ore and of petroleum located at the coast of the study area. Isotope ratios of anthropogenic Pb can be estimated using two end-members mixing equation and were 0.879±0.005 and 2.144±0.008 before 1950s' while they increased up to 0.900±0.008 and 2.162±0.011 after 1980s', respectively.

Keywords Pb, Pb isotopes, southern East/Japan Sea, sediment, Pb pollution