江汉平原高砷地下水监测场砷的动态变化特征分析

Dynamic changes of groundwater arsenic concentration in the monitoring field site,Jianghan Plain

江汉平原高砷地下水的发现引起了广泛关注,通过对该区域高砷地下水监测场不同深度不同季节地下水样品的分析,揭示了地下水的水化学特征及高砷地下水的垂向分布规律。同时,结合地下水和地表水的水位波动,探讨了地下水中砷含量的动态变化特征。结果表明:地下水水化学类型主要为HCO3-Ca·Mg型,为强的还原性地下水环境,Fe、Mn含量高。大部分监测点都是25m监测井水中砷的含量最高。地下水中砷含量的季节性动态变化特征与地下水水位密切相关。10m监测井砷含量与水位变化的关系最明显,随着水位的下降(抬升),地下水砷含量出现明显的降低(升高)响应。25m和50m监测井地下水中砷含量的动态变化与测压水位的动态变化不完全同步,存在一定的滞后效应,且含水层深度越大,滞后效应越明显。

Groundwater and surface water samples were collected in each season in the monitoring field site,Jianghan Plain.Major constituents,stable hydrogen and oxygen isotopic compositions and elevations of the groundwater levels in different seasons were measured to characterize groundwater chemistry and evaluate the dynamic changes of groundwater arsenic concentration.Results show that groundwater is mainly HCO3-Ca·Mg type,negative Eh with high concentrations of Fe and Mn.High arsenic concentrations of groundwaters are mainly distributed at the depth of 25 m.Dynamic changes of groundwater arsenic concentration and groundwater elevations are closely correlated.Arsenic concentration fluctuation of the groundwaters at 10m deep is consistent with the elevation fluctuation of the groundwater levels,while the arsenic concentration fluctuation of the groundwaters at 25mand 50mdeep has a hysteresis effect on the elevation fluctuation of the groundwater levels.Moreover,the hysteresis effect is more conspicuous at deeper groundwaters.