地下水流动对砷迁移的影响: 大同盆地试验场的观测与模拟

地下水流动特征对水文地球化学特征具有重要控制作用, 研究分析了大同盆地地下水流动特征对高砷水迁移的影响.以山阴县桑干河南岸地下水试验场(SYFS)的监测数据为基础, 建立了河岸带三维非稳定地下水流模型.结果表明, 灌溉在很大程度上影响着地下水位动态变化.灌溉活动减慢了地下水埋深和水平地下水流速, 加速了不同岩性地层之间的垂向水量交换.粉土(L1、L2、L3和L4)、粘土1(L5)和砂1(L6)之间始终存在由上至下的垂向水量交换, 粘土2(L7)、砂2(L8)、粘土3(L9)和砂3(L10)以水平水量交换为主.灌溉水和大气降水从地表向下垂直入渗至含水层的过程中, 推动了地表和包气带沉积物中的砷逐渐向下迁移; 到达含水层后, 水平交换量占主导, 地下水在水平方向上频繁的水量交换促使As在含水层中发生水平迁移. 

Impact of Groundwater Flow on Arsenic Transport:A Field Observation and Simulation in Datong Basin

Groundwater flow patterns often play an important role in controlling groundwater hydrogeochemical characteristics. To better understanding of hydrological influences on arsenic transport in groundwater of Datong basin, a transient three dimensional groundwater flow model of riparian zone was conducted based on the monitoring data of Shanyin field site. The model indicates that irrigation diminishes the groundwater depth and horizontal groundwater flow velocities and further accelerates the groundwater flux among different formations. Vertical water exchanges occur frequently among silt layers (L1, L2, L3, L4), clay1 layer (L5) and sand1 layer (L6), while among clay2 layer (L7), sand2 layer (L8), clay3 layer (L9) and sand3 layer (L10), the horizontal groundwater exchanges dominates. The model also presents a possible phenomenon that the vertical infiltration of irrigation water and precipitation from ground surface toward aquifer induces a downward movement of arsenic of vadoze zone sediments, and frequent groundwater exchange greatly promotes the horizontal migration of arsenic in aquifers.