沉积物地球化学特征和土地利用方式对地下水砷行为的影响

发布时间：2018-06-26 19:55

本文选题：银川平原 + 沉积物　；参考：《地学前缘》2017年02期

【摘要】：银川平原是典型的高砷内陆盆地。然而人为活动及沉积物地球化学条件对地下水砷分布的影响并不清楚。本文选取银川平原北部平罗县作为研究区,在不同研究单元共采集119组地下水样品(冲洪积平原、冲湖积平原水田区和冲湖积平原旱田区分别为54组、31组和34组),分析了其主量和微量组分含量。另在水田和旱田分别钻井一眼,采集66组沉积物(水田和旱田单元分别为31组和35组)样品,分析了粒度分布、化学成分、强(S2)、弱(S1)结合态砷等物化指标。结果表明,高砷地下水主要分布在10~20m深度范围内;冲洪积平原地下水中砷浓度普遍较低,平均浓度1.71μg·L~(-1),约95%的样品中砷浓度在10μg·L~(-1)以下;而冲湖积平原水田和旱田砷浓度较高,90%以上超过10μg·L~(-1),平均浓度分别达到26.6μg·L~(-1)和39.6μg·L~(-1)。沉积物总砷含量为3.94~75.2 mg·kg~(-1),平均值为11.5 mg·kg~(-1),S1、S2含量范围分别为0.01~0.33mg·kg~(-1),0.01~19.5mg·kg~(-1),分别约占总砷的0.7%和6.2%。沉积物中砷与铁、锰含量呈正相关,其分布受水动力条件及岩性的控制,黏土中砷含量较高。结合相同深度地下水砷浓度,得到S2、S1对应的平均砷分配系数Kd分别为0.001L·g~(-1)和0.007L·g~(-1)。Kd与ORP呈较好的正相关性,表明还原环境利于砷的释放;PO3-4的竞争吸附也能促进沉积物中砷的释放。在冲湖积平原,同深度上沉积物组成相近的含水层中,旱田地下水砷浓度较水田高,表明土地利用方式对砷的分布和运移也有重要影响。
[Abstract]:The Yinchuan plain is a typical high arsenic inland basin. However, the effect of human activity and sediment geochemical conditions on the distribution of arsenic in groundwater is not clear. In this paper, 119 groups of groundwater samples were collected from Pingluo County in the northern part of Yinchuan plain. The dryfield area is 54 groups, 31 groups and 34 groups respectively, and the contents of the main and trace components are analyzed. In addition, in the paddy field and the dry field, 66 groups of sediments (water field and dry field unit are 31 and 35 groups respectively) are collected. The grain size distribution, chemical composition, strong (S2), weak (S1) binding arsenic and other physicochemical indexes are analyzed. The results show that the high arsenic groundwater It is mainly distributed in the depth range of 10~20m; the concentration of arsenic in groundwater in alluvial plain is generally low, with an average concentration of 1.71 mu g. L~ (-1). About 95% of the samples are under 10 mu g L~ (-1), while the concentration of arsenic in the paddy field and the dryland is higher than that of 10 mu g. L~ (-1), with the average concentration of 26.6 mu g, L~, and 39.6, respectively. The total arsenic content of the sediments is 3.94~75.2 mg kg~ (-1), the average value is 11.5 mg. Kg~ (-1), S1 and S2 are 0.01~0.33mg kg~ (-1), respectively, accounting for about 0.7% of the total arsenic and arsenic and iron in the sediments, and the manganese content is positively correlated, and the distribution is controlled by the hydrodynamic conditions and lithology, and the arsenic content in clay is higher. The average arsenic concentration in the same depth of groundwater was obtained by S2, and the average arsenic distribution coefficient Kd corresponding to S1 was 0.001L. G~ (-1) and 0.007L. G~ (-1).Kd and ORP, which showed that the reduction environment was beneficial to the release of arsenic, and the competitive adsorption of PO3-4 could also promote the release of arsenic in the sediments. In the aquifer, the arsenic concentration in the groundwater of the dry land is higher than that in the paddy field, which indicates that the land use pattern also has an important influence on the distribution and migration of arsenic.
【作者单位】：中国地质大学(北京)生物地质与环境地质国家重点实验室;中国地质大学(北京)水资源与环境学院;中国地质调查局水文地质环境地质调查中心;
【基金】：国家优秀青年科学基金项目(41222020) 中国地质调查局地质调查项目(1212010813104)
【分类号】：P641.3

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