Lead and sulfur isotopic ratios in precipitation and their relations to trans-boundary atmospheric pollution

We measured the lead (Pb) and sulfur (S) isotopic ratios in precipitation collected in Toyama Prefecture, Japan, to investigate their characteristics as tracers for trans-boundary air pollution. The Pb concentrations and isotopic ratios were measured by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). A relatively higher Pb-207/Pb-206 isotopic ratio (area 3: Northern China, 0.869 +/- 0.003; area 4: Central China and Korea, 0.870 +/- 0.006) was assumed to be related to Northern Asian sources, whereas the samples influenced by Japanese air mass showed a lower Pb-207/Pb-256 ratio (area 5: Japan, 0.863 +/- 0.004). Sulfur ion was measured by Ion Chromatography (IC), and S isotopic ratios were measured by Mass Spectrometry. The S isotopic ratios' weighted average values (area 3: 4.9 +/- 1.4%.; area 4: 6.3 +/- 1.5 parts per thousand.) of the Asian continent showed a higher isotopic ratio than that of Japan (area 5: 3.6 +/- 1.8 parts per thousand.). It was difficult to use the NO3-/non-sea-salt SO42-, (nss SO42-) (N/S) ratio's weighted average values to distinguish the Japanese origin (area 5: 0.71) from the continental origin (area 3: 0.68, area 4: 0.66). We attempted to use the S isotopic ratio in addition to the lead isotopic ratio to characterize the transported East Asian air pollution, and as a result we found that the combination of these isotopic ratios was useful for identifying the origin of air pollution in the East Asian region. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.