Transformation of arsenic compounds in modern intertidal sediments of Iriomote Island, Japan |
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Authors: | Harue Masuda Yoshito Yamatani Mitsuru Okai |
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Affiliation: | aDepartment of Geosciences, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan;bKansai Environmental Engineering Center Co. Ltd., Chuo-ku, Osaka 541-0052, Japan |
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Abstract: | The arsenic accumulation process in intertidal sediments of Iriomote Island, Japan, is analyzed as a naturally balanced arsenic-fixation system. Major and minor element chemistry is analyzed by X-ray fluorescence photometry, mineralogy is investigated by X-ray diffractometry, and four arsenic compounds are characterized by hydrogen-generated atomic absorption photometry. It is found that arsenic is accumulated by iron hydroxides/oxides precipitated following the decomposition of humic acids in the shallower sediment, and is subsequently incorporated into iron sulfide minerals at depth. The arsenic is immobile during incorporation into arsenic-bearing phases, suggesting that arsenic is unlikely to be released into the porewater under natural conditions in early diagenesis. The formation and decomposition of arsenic-bearing organic compounds appear to be associated with the formation and decomposition of arsenic in oxyhydroxides/oxides, suggesting that microbial activity may play an important role in controlling the behavior of arsenic and arsenic-bearing phases in the sediment column. |
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Keywords: | Arsenic Sulfur Iron Humic acids Intertidal sediments Groundwater pollution |
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