塔里木盆地南缘浅层高碘地下水的分布及成因:以新疆民丰县平原区为例

塔里木盆地位于欧亚大陆腹地，远离海洋，地下水是塔里木盆地南缘重要的供水水源，查明该区浅层地下水中碘（I-）的分布及成因至关重要.基于新疆塔里木盆地南缘的民丰县平原区44组浅层地下水水样，综合运用水化学图解法、数理统计法和GIS技术，分析潜水和浅层承压水水化学特征、碘的空间分布及高碘地下水的成因.结果表明:民丰县平原区浅层地下水中碘的富集和贫乏共存；潜水和浅层承压水I-含量范围分别为≤730 μg/L和≤183μg/L，潜水水样中缺碘水、适碘水、高碘水和超高碘水占比分别为19.4%、69.4%、5.6%和5.6%，浅层承压水水样中缺碘水、适碘水和高碘水占比分别为12.5%、75.0%和12.5%，潜水中缺碘水和超高碘水均高于承压水.从山前倾斜平原到细土平原，地下水中I-含量呈明显上升趋势.高碘水和超高碘水水化学类型主要为Cl·SO₄-Na型和Cl-Na型.除水文地质条件和偏碱性的地下水环境外，研究区潜水碘主要受强烈的蒸发浓缩作用、第四系全新统沼泽堆积物和矿物溶解沉淀的影响，浅层承压水碘主要受矿物溶解沉淀及还原环境的影响. 

Distribution and Genesis of Shallow High-Iodine Groundwater in Southern Margin of Tarim Basin: A Case Study of Plain Area in Minfeng County,Xinjiang

Tarim Basin is located in the hinterland of Eurasia, far away from the sea. Groundwater is an important source of water supply in the southern margin of Tarim Basin. Based on the 44 groups of shallow groundwater samples from the plain area of Minfeng County in the southern margin of Tarim Basin, Xinjiang Uygur Autonomous Region, the hydrochemical characteristics of unconfined groundwater and shallow confined groundwater, the spatial distribution of iodine and the causes of the high-iodine groundwater were analyzed by using the hydrochemical graphic method, mathematical statistics method and geographic information system (GIS) techniques. The results show that iodine enrichment and iodine deficiency coexist in groundwater in plain area of Minfeng County. The I- contents in unconfined groundwater and shallow confined groundwater were ≤ 730 μg/L and ≤ 183 μg/L respectively. The proportions of iodine deficient water, suitable iodine water, high iodine water and ultra-high iodine water in unconfined groundwater samples were 19.4%, 69.4%, 5.6% and 5.6%, respectively. The proportions of iodine deficient groundwater, suitable iodine water and high iodine water in shallow confined groundwater samples were 12.5%, 75.0% and 12.5%, respectively. From the sloping plain in front of the mountain to the plain in the fine earth, the I- content in the groundwater increased obviously. The main hydrochemical types of high iodine groundwater and ultra-high iodine groundwater are Cl·SO₄-Na and Cl-Na. In addition to the hydrogeological conditions and alkaline groundwater environment, iodine content in unconfined groundwater is mainly affected by strong evaporation and concentration, Quaternary Holocene swamp deposits and mineral dissolution precipitation, and the shallow confined groundwater is mainly affected by mineral dissolution precipitation and reduction environment.