摘要
利用X射线衍射和X射线荧光分析、沉积物序列提取试验及矿物饱和度的计算,对采自江汉平原中部沙湖地区典型高砷含水层钻孔沉积物样品矿物学进行了分析,并讨论了控制含水层中砷释放和迁移的地球化学机制。对矿物在沉积物与土壤中的分布及组成的对比分析,在一定程度上指示了矿物赋存环境和/或高砷水形成的环境背景:土壤与沉积物中高岭石以低于其他3种粘土矿物的含量普遍存在,指示了含水层沉积物形成过程江汉平原存在一定的湿热古气候环境;沉积物绿泥石含量低于土壤中绿泥石,恰恰反映了土壤比沉积物略强的碱性环境;沉积物中黄铁矿的存在,显示了含水层局部的强还原性环境,指示地下水中广泛存在的Fe2+容易与二价硫发生沉淀并结合砷。砷主要以无定形铁锰氧化物结合态(平均在31%以上)形式存在,其次以碳酸盐和有机质结合态存在。无定形铁锰氧化物的还原溶解可能是控制砷迁移到地下水中主要的地球化学机制。相对高含量的绿泥石容易在含水层中发生风化,其溶解过程可以将铁释放到地下水中,从而成为影响地下水中砷活化的潜在因素。
Analysis of XRD and XRF, combined with sequential extraction experiment o{ sedi- ments and saturation index calculation were conducted to understand the mechanism of arsenic re- lease from sediments into groundwater. The difference in mineral composition distribution and characteristics between soil and sediments revealed the occurrence environment of minerals and the conditions for the formation of elevated arsenic groundwater. Detected pyrite reflected the re- ducing environment of aquifer. Arsenic bond to amorphous iron oxyhydroxides was the main spe- cies occurred in sediments. The reductive dissolution o{ iron oxyhydroxides was considered as the main geochemical mechanism responsible for arsenic mobilization. Chlorite was also a potential species associated with arsenic mobilization due to iron dissolution/release.
出处
《矿物岩石》
CAS
CSCD
北大核心
2012年第4期7-11,共5页
Mineralogy and Petrology
基金
国家自然科学基金(NSFC
40830748)
关键词
矿物学特征
砷
绿泥石
饱和指数
江汉平原
mineralogical characteristics
arsenic
chlorite
saturation index
JianHan Plain
