| The effects of vegetation type, pollutant concentration, flow velocity and slope on runoff pollutant removal efficiency were studied by comparing three kinds of soil-plant systems, namely “soil- alfalfa” system, “soil-tall fescue” system and control system with no vegetation. Results indicated that the influence of vegetation type, pollutant concentration, flow velocity and slope on pollutant removal efficiency varies with the status and nature of pollutants. The trapping of particulate pollutant SS（suspended solid）, PP（particulate phosphorus） and CODMn is affected by the above mentioned four parameters obviously. The particulate pollutant removal efficiencies in the “soil-alfalfa” system and “soil-tall fescue” system were significantly superior to the control system, and decreased with the increasing of influent concentration, influent flow rate and slope. The removal efficiencies of dissolved pollutant NO-3-N, NH+4-N and TDP（total dissolved phosphorus） were affected by vegetation type and influent concentration significantly. The dissolved contaminant removal efficiency in the “soil-tall fescue” system was better than the “soil-alfalfa” system as well as the control system. Nitrate removal rate reached highest in moderate concentration. The removal efficiencies of NH+4-N and TDP increased with the increase of their concentrations. Nitrate removal rate decreased remarkably with increasing influent flow rate. The removal rate of NH+4-N decreased significantly with increasing slope of soil system. It was concluded through the investigation that while constructing soil-plant system to control runoff pollutants, the upstream pollution status and the receiving water quality requirement should be considered, a dense growth of surface vegetation should be selected, and the slope of the soil system should be lowered to improve contaminant trapping function of soil-plant system. |
