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查明地下水中砷的时间变异性规律及机理是高砷地下水研究的难点和热点,也是防控地下水砷污染的根本.选择在雨季前后对浅层潜水和孔隙承压水进行了动态监测.研究表明地下水砷含量和形态与地下水位波动存在明显的响应关系:雨季开始后随着地下水位抬升,地下水还原环境增强,As(Ⅴ)和Asp转化成As(Ⅲ),颗粒态铁大幅降低,导致水中溶解的砷和铁大幅增加,地下水砷含量在雨季达到最高且As(Ⅲ)所占比例达到90%;雨季结束后随着水位逐渐降低,地下水中As(Ⅲ)所占比例和溶解的砷含量下降.农业活动对浅层潜水砷形态季节性变化有明显的影响.孔隙承压水的砷形态分布变化较浅层潜水幅度大,其变化与水位波动存在滞后效应.自然或人为活动引起的地下水位季节性变化改变了含水层的氧化还原环境,补给水源与地下水之间的混合过程带来新的物质输入促进地下水系统中砷的迁移转化.
The regularity and mechanism of time variation of arsenic in groundwater were identified as the difficulties and hot spots in the study of arsenic in groundwater and the basis of prevention and control of arsenic contamination in groundwater.The dynamic monitoring of shallow subduction and pore pressure water was conducted before and after the rainy season Indicating that there is a clear response relationship between groundwater arsenic content and groundwater level fluctuations. As the groundwater level rises and the reduction environment of groundwater increases, As (Ⅴ) and Asp transform into As (Ⅲ) and the particulate iron decreases greatly after the onset of the rainy season, The arsenic and iron dissolved in water increased greatly. The arsenic content in groundwater reached the highest in the rainy season and As (Ⅲ) accounted for 90%. As the water level decreased gradually after the rainy season, the proportion of As (Ⅲ) in groundwater and dissolved arsenic Content decreased.Agricultural activities had a significant effect on the seasonal changes of arsenic species in shallow submerged.Arsenic species distribution in pore-confined water varied greatly from that in shallow submarine, and there was a lagging effect between changes and water level fluctuations.Among them, natural or human activities Seasonal changes in groundwater levels have changed the redox environment in aquifers, bringing new inputs into the mixing process between recharge sources and groundwater to promote groundwater Arsenic migration and transformation.