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Chemical forms of arsenic in the modern sediments under microbiologically controlled condition concerned with arsenic polluted groundwater

与砷污染地下水有关的微生物控制条件下现代沉积物中砷的化学形态

基本信息

批准号：
12440155
负责人：
MATSUDA Harue
金额：
$ 8.77万
依托单位：
Osaka City University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

The highly arsenic-contaminated groundwaters, causing serious health hazards in the world, monstly present in the modern sediments. In this study, arsenic releasing mechanism is discussed based on the analyses of groundwaters, estuarine waters, and modern sediments of the Osaka basin, and the intertidal sediments from the iriomote island, OkinawaSediments of the intertidal zone of lriomote island record a naturally balanced arsenic-fixation system, where accumulated arsenic compounds are largely fixed into sulfide mineral(s) transformed by iron hydroxide/oxide. This transformation appears to be mediated by microbial reactions in the stagnant aquitard during the initial stage of diagenesis. Significant release of arsenic to groundwater would be unlikely to occur if the transformation rates among arsenic solid phase compounds are stablePhytoplankton and its body accumulates arsenic in the estuarine sediments, suggesting that high concentration of arsenic in the marine clay layers of Osaka Group sediments, from 7 to 20 ppm, is also the results of such a microbial accumulation. After the deposition, most of the arsenic is finally fixed in pyite. In the southem part of Osaka Basin, Senshu area, The heavy suifur isotope ratios (20-27 CDT) of sulfate-sulfur in the groudwater from the spring to fall indicate that the source of the sulfur is the pyite in the sediments. Afterpyrite decomposition supplies the arsenic into the groundwater, arsenic concentrations changes in harmony with dissolution of iron oxyhydroxide in reduced condition produced by bacterial activity. The observation in this well water suggests that the pyrite was he primary source of arsenic in the Osaka Basin, however, arsenic release is dependent on the solubility of iron oxyhydroxide, mainly controlled by the redox condition produced by the bacterial activity in the well

高砷污染的地下水，在世界范围内造成严重的健康危害，主要存在于现代沉积物中。本文通过对大坂盆地地下沃茨、河口沃茨和现代沉积物的分析，探讨了砷的释放机制。冲绳西表岛的潮间带沉积物记录了一个自然平衡的砷固定系统，其中积累的砷化合物大部分被铁的氢氧化物/氧化物转化为硫化物矿物。这种转变似乎是介导的微生物反应在停滞弱透水层在成岩作用的初始阶段。如果砷固相化合物之间的转化速率稳定，则不太可能发生砷向地下水的显著释放。浮游植物及其身体在河口沉积物中积累砷，这表明大坂组沉积物的海洋粘土层中的高浓度砷（7 - 20 ppm）也是这种微生物积累的结果。沉淀后，大部分砷最终固定在黄铁矿中。在大坂盆地南部的神州岛地区，从春季到秋季地下水中硫酸盐-硫的重硫同位素比值（20-27 CDT）表明，硫的来源是沉积物中的硫铁矿。黄铁矿分解后向地下水中提供砷，砷浓度的变化与细菌活动产生的还原状态下的氢氧化铁的溶解相协调。该井水中的观察结果表明，黄铁矿是大坂盆地砷的主要来源，但砷的释放取决于羟基氧化铁的溶解度，主要受井水中细菌活动产生的氧化还原条件控制