Arsenic Behavior in Paddy Fields during the Cycle of Flooded and Non-flooded Periods

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• 作者：Yoshio Takahashi ; Reiko Minamikawa ; Ké ; iko H. Hattori ; Katsuaki Kurishima ; Nobuharu Kihou ; and Kouichi Yuita
• 刊名：Environmental Science & Technology
• 出版年：2004
• 出版时间：February 15, 2004
• 年：2004
• 卷：38
• 期：4
• 页码：1038 - 1044
• 全文大小：188K
• 年卷期：v.38,no.4(February 15, 2004)
• ISSN：1520-5851

文摘

The behavior of As in paddy fields is of great interestconsidering high As contents of groundwater in severalAsian countries where rice is the main staple. We determinedthe concentrations of Fe, Mn, and As in soil, soil water,and groundwater samples collected at different depths downto 2 m in an experimental paddy field in Japan duringthe cycle of flooded and non-flooded periods. In addition,we measured the oxidation states of Fe, Mn, and As insitu in soil samples using X-ray absorption near-edge structure(XANES) and conducted sequential extraction of the soilsamples. The results show that Fe (hydr)oxide hosts As insoil. Arsenic in irrigation waters is incorporated in Fe(hydr)oxide in soil during the non-flooded period, and theAs is quickly released from soil to water during the floodedperiod because of reductive dissolution of the Fe(hydr)oxide phase and reduction of As from As(V) toAs(III). The enhancement of As dissolution by the reductionof As is supported by high As/Fe ratios of soil waterduring the flooded period and our laboratory experimentswhere As(III) concentrations and As(III)/As(V) ratios insubmerged soil were monitored. Our work, primarily basedon data from an actual paddy field, suggests that riceplants are enriched in As because the rice grows in floodedpaddy fields when mobile As(III) is released to soilwater.