原生高砷地下水在全球分布广、危害大,严重威胁着全世界数亿人口的身体健康.为科学指导高砷地区地下水资源的合理开发利用,以中国大陆第一个砷中毒病区新疆奎屯为研究区域,分析了奎屯地区高砷地下水的分布规律、类型及成因.结果表明,奎屯地区有88.7%的地下水中砷浓度超出10μg·L-1,多为高砷地下水.高砷地下水多分布在深层承压含水层,砷浓度从南向北逐渐升高,与采样点海拔高度呈显著负相关.奎屯地区地下水整体呈弱碱性、碱性环境,氧化还原电位(Eh)均为负值,具有较强的还原性,属于还原性-弱碱性高砷地下水(I-2型).奎屯南面的天山与北面的河流沉积平原环境相结合,为该区地下水形成高砷提供了有利的地质环境.奎屯地区沉积层深厚,地下径流更替缓慢,相对封闭的水文地质条件使地下水中的砷富集而不易流失,强烈的蒸发可以使地下水中的砷进一步浓缩.同时,地下水的还原条件有利于含水层中砷的释放,砷浓度不仅受铁锰氧化物矿物还原的影响,而且受SO2-4还原和硫化物矿物沉淀的控制,吸附态砷的解吸附也是该地区地下水的富砷过程.
Geogenic high-arsenic groundwater has severe negative effect on hundreds of millions of people due to its wide distribution and high toxicity.As the first arsenic area in China,Kuitun was taken as the study area for distribution,classfication and cause analysis of high arsenic groundwater,which would provide theoretical reference for rational development and utilization of groundwater resources in high-arsenic areas.It is found that,88.7% of groundwater contains arsenic at the concentration of 10 μg·L-1or higher in Kuitun,and such high arsenic groundwater distributed mostly in deep confined aquifer;the arsenic concentration increased gradually from south to north,which had an extremely significant negative correlation to the sampling-point elevation.The groundwater in Kuitun was reductive-weak alkaline-high arsenic groundwater(Type I-2).Tianshan Mountains in the south and the alluvial plain in the north provided favorable geological environment for high arsenic groundwater,where the sediment layer is thick,groundwater runoff changes slowly,and the relatively closed hydrogeological conditions enrich the As in groundwater rather than being drained.The intensive evaporation made As in groundwater enriched further.While the reducing environment of groundwater was conducive to the release of As in the aquifer;As concentration was not only affected by Fe-Mn oxide reduction,but also controlled by SO2-4reduction and precipitation of sulfide minerals;the desorption of adsorbed arsenic also contributed to arsenic enrichment in groundwater of Kuitun.