[H-TT16] 環境トレーサビリティー手法の開発と適用

[HTT16-04] Multi-isotopic approach to evaluate effects of transboundary air pollution on forest ecosystems of central Japan

*佐瀬 裕之¹、諸橋 将雪¹、高橋 雅昭¹、大泉 毅¹、猪股 弥生²、藪崎 志穂³、齋藤 辰善^6,4、山下 尚之⁵、陀安 一郎³、中田 誠⁴ (1.一般財団法人日本環境衛生センターアジア大気汚染研究センター、2.金沢大学、3.総合地球環境学研究所、4.新潟大学、5.森林総合研究所、6.新潟県)

キーワード：硫黄、水文過程、緩衝メカニズム、酸性化からの回復

Japanese Islands have been influenced by transboundary air pollution from the Asian Continent. In particualr, the central Japan is known as the area in which high deposition amounts of acid substances have been reported. Both northwesterly seasonal winds in winter and high precipitation amounts contribute to the high deposition in the area. To evaluate transboundary air pollution on forest ecosystems in central Japan, we applied multi-isotopic analyes to rainwater, soil solution, and river water in two forest catchments, namely Kajikawa (KJK) and Ijira (IJR) in the Sea of Japan side and Pacific side, respectively. In this presentation, we mainly introduce results of S isotopic ratio and H and O isotopic ratios of H₂O in the environmental waters, while other isotopic analyses, including Pb, Sr, and NO₃^-, have been applied to the same samples. The peak SO₄^2- deposition amounts were observed in winter and summer at KJK and IJR, respectively. It has been suggested that IJR in the Pacific side was strongly influenced by domestic emissions in Chukyo Industrial Area near Nagoya, while KJK in the Sea of Japan side was influenced by transboundary air pollution. However, according to the multi-isotopic analyses, a slight diffrent view was suggested. The δ³⁴S values of SO₄^2- in rainwater increased in winter at both KJK and IJR, suggesting that S sources in winter were different from those in summer. It has been well known that sea salts (+20.3‰) and Chinese coals (mean, +6.6‰) contributed higher δ³⁴S values in winter in the Sea of Japan side, while oils imported from the Middle Eastern countries mainly used in Japan have lower isotopic values (mean, -2.7‰). Moreover, d-excess values (δ²H – 8 × δ¹⁸O) in rainwater increased in winter also at both KJK and IJR, suggesting that winter precipitations at both sites were derived from water vapor of the Sea of Japan. Seasonal changes of these isotopic values suggested that not only KJK but also IJR was certainly influenced by transboundary air pollution due to northwesterly winds in winter. We are going to present results of soil solution and river water, too.