東北日本の雨水中の硫酸イオンとカルシウムイオン濃度の季節変動, 起源および広域風成塵降下量との関係

Translated title of the contribution: Influence of Asian Long-Range Eolian Dust on Chemical Components and Inorganic Dust Deposits of Rainwater in Northeast Japan

井上 克弘, 濱浦 尚生, 平舘 俊太郎, 葛西 攻

Research output: Contribution to journalArticle

Abstract

Five snow samples collected on Mt. Hachimantai (1400 m a. s. l. ) in the months of May and June from 1991 to 1996 contained significant amounts of eolian dust. Fifty-four rainwater samples were collected at Morioka from Jan. 17, 1992 to Apr. 27, 1994 and at Fukaura from Sept. 28, 1992 to Feb. 3, 1995 ; areas located in Northeast Japan. The pH values, concentration of chemical components, and amount of eolian dust in the rainwater samples were determined. Fifteen percent and 27% of the rainwater samples from Morioka and Fukaura, respectively, were acid rain. About 76 and 57% of the inorganic dust deposits in the rainwater samples from Morioka and Fukaura, respectively, were dominated by a <20 μm fraction and their depositions were marked from winter to spring, suggesting a strong influence of Asian long-range eolian dust. The annual deposition of nssSO_4^<2-> and nssCa^<2+> in rainwater was 4.5 and 4.0 meq m^<-2> in Morioka and 6.2 and 7.1 meq m^<-2> in Fukaura, respectively. The chemical compositions of eolian dust deposits in the rainwater samples were compared with Chinese loess and Hachimantai eolian dust in snow deposits. These deposits were characterized by almost the same chemical, physical and mineralogical properties. Sulfate in the Morioka rainwater is transported from China. In addition, the relatively low E factors of SO_4^<2-> of Japanese rainwater samples were partially influenced by sea salt, especially in the winter season. A significant correlation between the amounts of nssSO_4^<2-> and nssCa^<2+> of eolian dust deposits in rainwater samples suggests that nssSO_4^<2-> and most of the nssCa^<2+> and nssK^+ were dissolved from Asian long-range eolian dust contained in the rainwater samples. The annual deposition of nssSO_4^<2-> and nssCa^<2+> in Northeast Japan was 1.5 to 2 times higher for nssSO_4^<2-> and 3 to 5 times higher for nssCa^<2+> than that in Southwest Japan. The present results suggest that the rainwater samples in Northeast Japan are strongly influenced by Asian long-range eolian dust.
Translated title of the contributionInfluence of Asian Long-Range Eolian Dust on Chemical Components and Inorganic Dust Deposits of Rainwater in Northeast Japan
Original languageJapanese
Pages (from-to)445-456
Number of pages12
Journal日本土壌肥料学雑誌 = Japanese journal of soil science and plant nutrition
Volume69
Issue number5
Publication statusPublished - Oct 5 1998

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