地下水位上升过程硝态氮(硝酸盐)污染变化规律研究

Study on the variation law of nitrate pollution during the rise of groundwater level

地下水水位上升会造成包气带外源污染物的输入,如硝态氮,同时引起浅层地下水水环境变化.为了研究水位上升过程对硝态氮(硝酸盐)的影响,选取北京市通州区代表性介质,建立室内砂槽实验,探究水位上升过程硝态氮的二维迁移转化规律.实验结果表明:随着地下水位上升,砂槽从上至下,从左至右,溶解氧和氧化还原电位含量均逐渐降低,地下水逐渐向还原环境转变.浅层地下水通过对包气带污染物的浸溶,硝态氮和铵态氮含量存在明显的分层特征,埋深越小,其硝态氮和铵态氮的含量越高.地下水位上升过程的侧向径流,有利于硝酸盐在地下水中的迁移转化,侧向水流方向下游,铵态氮存在升高的风险.因此,地下水位上升对硝态氮的影响不容忽视.

Rising groundwater levels will cause the input of exogenous pollutants,such as nitrate,in the vadose zone,and at the same time alter the shallow groundwater environment.In this study,we aimed to measure the effect of water level rise process on nitrate nitrogen(nitrate).Representative media were selected in Tongzhou District,Beijing,and an indoor sand tank experiment was established to simulate the migration and transformation of nitrate nitrogen during the groundwater level rise process.The experimental results show that as the groundwater level continues to rise,from the top to the bottom of the sand tank,and from the left side to the right side,both the dissolved oxygen and redox potential gradually decrease,and the groundwater gradually changes to the reducing environment.The shallow groundwater show the obvious characteristics of nitrate and ammonium stratification as a result of pollutants leaching into the vadose zone.The lower the burial depth,the higher the nitrate nitrogen and ammonium nitrogen content.There is also lateral runoff during the rise of the groundwater level,which is conducive to the migration of nitrate in groundwater.Along the direction of lateral water flow,there is a risk of increasing ammonium nitrogen.Therefore,the influence of groundwater level rise on nitrate nitrogen cannot be ignored.