摘要
选取江汉平原典型地下水砷中毒区仙桃市沙湖原种场为研究区,对3个长50m的钻孔沉积物砷含量与赋存形态及其他化学组成进行了分析。结果表明区内沉积物砷质量分数为1.35~107.5mg/kg（平均值为12.8mg/kg）。黏土或亚黏土层中砷含量较高,这与细粒沉积物中铁锰氧化物、黏土矿物对砷的吸附有关。地下20m左右深度内含水层沉积物中砷含量最高,相应地下水中砷质量浓度高达到1 000μg/L。草酸-草酸铵选择性提取结果指示沉积物中10%~77%（平均38%）的As与无定形铁氢氧化物结合,表明无定形铁氢氧化物还原性溶解可能是控制砷释放与还原的主要地球化学过程,并且有机质生物氧化机制极大地促进了该过程。然而,沉积物中仅1.2%~23%的铁被草酸-草酸铵提取,含水层中砷浓度主要受铁的氢氧化物还原性溶解影响,但其他形式的铁、有机物的吸附作用亦控制着砷的含量。
To identify the mechanism of arsenic mobilization from sediments to groundwater in the Jianghan Plain, sediment samples of three 50m deep boreholes from the endemic arsenicosis area located in Shahu village were chosen for study. The results indicated that the arsenic concentrations of sediments in the re- gion have a range of 1.35--107.5 mg/kg, with a median of 12.8 mg/kg. The arsenic content in the silt and clay samples were higher because arsenic could be bounded with iron, manganese oxides and clay min- erals in fine grained sediments. ChemicaI composition of the sediments was affected by their lithology and particle size. The maximum content of arsenic was found at a depth of 20 m the content in the groundwater was up to 1 000μg/L. Reductive dissolution of amorphous iron oxides may be the main geochemical mech- anism controlling arsenic mobilization from sediments to groundwater. Between 10 %--77 % （a median val- ue of 38%） of arsenic in the sediments could be extracted by ammonium oxalate, only 1.2%--23% of iron could be extracted. Arsenic concentrations in the aquifer are mainly influenced by reductive dissolution of the Fe oxyhydroxides. In addition, adsorption of other forms of iron, organic matter also controls the con- tent of arsenic.
出处
《地质科技情报》
CAS
CSCD
北大核心
2015年第3期178-184,共7页
Geological Science and Technology Information
基金
国家自然科学基金项目(41102153
41120124003)
中央高校基本科研业务费专项基金"摇篮计划"(CUGL140412&CUG120113)
中国地质调查局地质调查工作项目(12120114069301)
关键词
砷
沉积物
迁移
铁氧化物
吸附作用
arsenic
sediment
mobilization
Fe oxides
adsorption
