Biogeochemical properties and potential risk of shallow arsenic-rich sediment layers to groundwater quality in Western Bangladesh
Biogeochemical properties and potential risk of shallow arsenic-rich sediment layers to groundwater quality in Western Bangladesh
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DOI：
10.1007/s10653-021-01087-7
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发表时间：
2021-09
影响因子：
4.2
通讯作者：
Nguyen Van Thinh;M. Matsumoto;Myo Zaw;Y. Kuwahara;Yiping Xie;Akinori Ozaki;K. Kurosawa
中科院分区：
文献类型：
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作者：
Nguyen Van Thinh;M. Matsumoto;Myo Zaw;Y. Kuwahara;Yiping Xie;Akinori Ozaki;K. Kurosawa
然而，在南亚和东南亚的许多三角洲地区，地下水砷污染已引起人们的关注，主要集中在深层含水层。本文利用ICP-MS、FE-EPMA、XRD和14 C-AMS等技术对孟加拉国浅层含水层沉积物柱样中砷的含量及其分馏进行了研究。研究结果表明，As的峰值浓度（54.7-79.1 μg/g）出现在泥炭层（7.5-8.0 m）。几种类型的铁（oxyhidr）的氧化物和framboidal黄铁矿，其中也含有砷，被发现在泥炭样品。高浓度的砷主要以可交换态、含砷铁晶体和含砷有机质的形式存在。结果表明，富As泥炭层形成于3170 ~ 3901卡年前，是由于海平面下降所致。基于16 S rRNA基因的系统发育分析表明，富砷泥炭中的细菌主要隶属于不动杆菌属、肠杆菌属、埃希氏菌属、芽孢杆菌属、梭菌科和不动杆菌属;通过计算沉积物的地积累指数和生态风险指数，富砷泥炭层分别属于中-重度污染和相当大的污染级别。在永久饱和条件下，富砷泥炭层应被视为该地区地下水砷的重要潜在驱动力。
The arsenic-contaminated groundwater has attracted attention in much south and southeast Asian deltas, however, mainly on the deep aquifers. Here, arsenic (As) concentration and its fractionation of the sediment cores in a shallow aquifer in Bangladesh were investigated using ICP-MS, FE-EPMA, XRD and14C-AMS chronology techniques. The results of the present study indicated that the peak concentrations of As (54.7–79.1 µg/g) were in peat layers (at a depth of 7.5–8.0 m). Several types of iron (oxyhidr)oxides and framboidal pyrite, which contain As also, were found in the peat samples. The high concentrations of As were in an exchangeable form, As-bearing iron crystalline and As-bearing organic materials. We revealed that the As-rich peat layers were formed from 3170 to 3901 cal yrs before, due to the sea level decrease in this area. The 16S rRNA gene-based phylogenetic analysis revealed that the bacterial strains in the As-rich peats were mainly affiliated with generaAcinetobacter, Enterobacter,Escherichia,Bacillus, Clostridiaceae and Acinetobacter.The geo-accumulation index (Igeo) and ecological risk index assessment were calculated for the sediments, which shows that As-rich sediment layers were in range of moderately to heavily contaminated and considerable classes, respectively. Under the permanent saturated condition, the As-rich peat layers should be considered as an important potential driver of the groundwater As in this area.