红枫湖流域农业面源污染治理的生物地球化学垒体系构建初探

A Pilot Study on the Construction of Biogeochemical Barriers for Agricultural Non-point Source Pollution Control in the Hongfeng Lake Watershed

在点源污染得到有效控制后,流域内农业面源污染逐渐成为了湖库氮、磷等营养物质外源输入的主要贡献者。本研究选取红枫湖流域农田土壤为研究对象,对其添加改良剂并种植植物来构建生物地球化学垒,并对其氮、磷拦截效应进行了综合评估。研究结果表明,添加Al_(2)(SO_(4))_(3)、CaCl_(2)与钠基膨润土显著提高了土壤对NH_(4)^(+)-N、NO_(3)^(-)-N和磷的拦截率,降低其流失程度。其中,对土壤添加CaCl_(2)改性钠基膨润土并种植植被构建的生物地球化学垒,对NH_(4)^(+)-N、NO_(3)^(-)-N和磷的综合拦截效果最佳,截留率分别为87%、95%、93%。而添加了FeSO_(4)的土壤,NO_(3)^(-)-N的淋失程度增强,不宜选取。种植植物后,植物生长对土壤中氮和磷有一定的活化作用,导致模拟径流中NH_(4)^(+)-N和溶解性磷浓度较种植植物前升高,但是均低于对照组。而且种植植物后经改良的土壤单元有效磷(Olsen-P)较种植植物前显著降低,也反映出植物对土壤磷的活化利用。综上表明,通过对土壤添加Al_(2)(SO_(4))_(3)、CaCl_(2)与钠基膨润土并种植适生植物(黑麦草和白花三叶草)来构建生物地球化学垒,可以实现红枫湖小流域内的氮、磷等污染物拦截和植物生长两相促进,从而有效、持续拦截土壤氮、磷,降低其流失程度,对实现农业面源污染的可持续治理具有重要意义。

When the point source pollution got under control,agricultural non-point source pollution in the watershed gradually became the main contributor to the exogenous inputs of nutrients,such as nitrogen(N)and phosphorus(P)and other nutrients.In this study,agricultural soils in the Hongfeng Lake watershed were chosen as the research object.The biogeochemical barrier was constructed by adding amendments and growing plants,and the interception effect of N and P was comprehensively evaluated.The results show that the addition of Al_(2)(SO_(4))_(3),CaCl_(2) and sodium-based bentonite significantly increased the interception rates of NH_(4)^(+)-N,NO_(3)^(-)-N and phosphorus,consequently reducing its loss.In addition,the biogeochemical barrier constructed by adding CaCl_(2) modified sodium-bentonite to soils and growing plants intercepted NH_(4)^(+)-N、NO_(3)^(-)-N and P most effectively with an interception rate of 87%,95% and 93%,respectively.Conversely,FeSO_(4) amended soils enhanced NO_(3)^(-)-N leaching and should not be considered.After planting,the plant growth had certain activation effects on soil N and P,which resulted in higher concentrations of NH_(4)^(+)-N and dissolved P in simulated runoff,although both were lower than the control.Moreover,the effective P per unit(Olsen-P)of the amended soil was significantly lower than before planting,which reflected the active utilization of soil P by plants.It can be said in conclusion that the biogeochemical barrier constructed by adding Al_(2)(SO_(4))_(3),CaCl_(2) and sodium-bentonite to the soil and planting suitable plants(ryegrass and white clover)can effectively and continuously intercept soil N and P which furthermore promotes plant growth in Hongfeng Lake watershed.This is of great significance for the sustainable control of agricultural non-point source pollution.