富砷地热废水排放的水环境效应——以西藏羊八井热田为例

Water-environmental Effects Induced by Discharging Geothermal Wastewater with High As Levels:A Case Study at Yangbajing in Tibet

西藏羊八井热田是我国目前唯一用于地热发电的高温热田,地热电厂产生的高砷废水直接排入了藏布曲(河)——热田内最主要的地表水体。通过地热废水、藏布曲(河)河水、羊八井河水和藏布曲南溪水的砷含量的对比,阐明了地热废水排放与其他水体汇入对藏布曲河水砷含量变化的影响。地热废水中的砷在排入藏布曲后受到了河水稀释作用与河床沉积物吸附作用的影响。计算了藏布曲不同河段内砷的综合衰减系数,并与河床沉积物对砷的吸附分配系数进行了对比,发现二者的拟合曲线符合指数关系。这表明随着河床沉积物吸附作用的加强,河水中砷的天然衰减将相应呈指数形式增加。

The geothermal power plant at Yangbajing of Tibet discharges effluents containing high arsenic directly into the Zangbo River, the major surface water body which is joined by the Yangbajing River. This study is based on a simultaneous survey including fiver water and sediment sampling and analysis of As and focused on the effects of dilution of fiver water and adsorption of fiver bed sediments, The comprehensive attenuation coefficients of As is calculated in different sections of the Zangbo River and compared with the adsorption coefficients of the relative sediments, indicating that there is clear exponential relation between them and natural decline of arsenic in the fiver is exponentially strengthened by adsorption of fiver sediments.