Journal of Japan Society for Atmospheric Environment / Taiki Kankyo Gakkaishi
Online ISSN : 2185-4335
Print ISSN : 1341-4178
ISSN-L : 1341-4178
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Studies of the Transboundary Transportation of Air Pollutants by Observation of Sulfur Isotopic Composition
Tsuyoshi Ohizumi
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2022 Volume 57 Issue 1 Pages 15-23

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Abstract

A large emission of air pollutants from the Asian continent has caused transboundary air pollution, especially in Northeastern Asia. This paper evaluates the sulfate deposition in a leeward area of the Asian continent, i.e., the Nagaoka observation station located along the Sea of Japan. We have monitored the atmospheric sulfate deposition and its sulfur isotopic ratio (δ34S) for 28 years at this station as well as the sulfur isotopic ratio of coal and oil used in the source and local areas. The sulfur isotopic ratios of non-sea-salt sulfate (δ34Snss) in Nagaoka ranged from 0.0 to +6.2‰. The isotopic ratios of the local emission and Chinese coal sulfur showed negative and positive values, respectively. Several statistically significant trends were detected regarding the deposition of non-sea-salt sulfate (nss-SO42−) during the study period. The amount of nss-SO42− deposition fluctuated in the mid-1980s, late 1990s to late 2000s, and mid-2000s with fluctuations in the δ34Snss value. Mass balance calculations suggested that sulfur released by coal combustion in China during the 1990s contributed to about 40% of the annual total sulfur deposition in Nagaoka, and its contribution increased to over 60% in the middle of the 2000s. The contribution began to decrease after that peak, which was in agreement with the temporal change in emissions from China.

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