土壤—植物系统净化地表径流非点源污染物实验研究

Experimental study on removal of non-point pollutants in surface runoff with soil-vegetation system

利用自行设计的6 m土槽构建土壤—植物系统,以无植被土槽为空白对照,设置不同的污染物进水浓度,采用模拟径流方式进行非点源污染净化实验。结果表明:(1)植被的存在能有效滞缓径流和提高污染物去除率,其中土壤—高羊茅系统的净化效果略优于土壤—紫花苜蓿系统,其SS、NO3--N、NH3-N、TDP、PP去除率分别达到86.61%、25.83%、52.03%、26.53%及76.59%;(2)在本研究的进水浓度范围内,浓度变化对处理系统净化效果的影响与污染物存在状态有关,进水浓度增加后颗粒态污染物去除率无显著变化而溶解态氮去除率均出现明显下降;(3)以污染物出水浓度随径流长度的变化表征污染物截留特征,SS和PP出水浓度均随径流长度增加而呈指数降低,NO3--N、NH3-N和TDP出水浓度随径流长度增加而呈线性降低,植被及进水浓度条件对污染物截留特征无明显影响。

A soil-vegetation system is made up with self-designed 6 m soil-bins, the experiment on removing the non-point pollutants is carried out by simulation of runoff, i.e. setting various inflow-concentrations of pollutants and taking a soil-bin without vegetation for the blank comparison. The result shows that ： （ 1 ） the existence of vegetation can effectively buffer the surface runoff and enhance the removal rate ; in which the removal effect of the soil-tall fescue system is slightly better than that of the soilalfalfa system, and then the removal rates of SS, NO3^- -N, NH3 -N, TDP can reach 86.61%, 25.83%, 52.03%, 26. 53% 及 76. 59% respectively; （2）within the range of the inflow-concentrations of pollutants adopted in this study, the impact of inflow-concentrations of pollutants on the removal effect of the treatment system depends on the existence states of pollutants, and no any obvious changes are there after the increases of the inflow-pollutants, whereas the removal rate of the dissolved nitrogen shows a significant decline ; （ 3 ） if representing the interception characteristics of pollutants by the changes of the outflow concen-trations of pollutants along with the runoff extension, both SS and PP outflow concentrations decrease along with the increase of the runoff extension exponentially and NO3^- - N, NH3 - N and TDP outflow concentrations decrease along with the increase of the runoff extension linearly, meanwhile, the conditions of vegetation and inflow concentrations of pollutants have no obvious impacts on the interception characteristics of pollutants.