不同植物篱系统对坡耕地农田径流污染物的去除效果

Removals of pollutants in surface runoff from sloping farmland using different hedgerow systems

采用人工模拟实验,探讨了四种植物篱系统在不同坡度（5°、10°和20°）、不同污染物进水浓度（低、中、高）下对坡耕地农田径流污染物TN、TP、NH_3-N、TOC、COD的去除效果。植物篱系统分别是红叶石楠＋小叶女贞＋黑麦草（T1）、红叶石楠＋小叶女贞（T2）、小叶女贞＋黑麦草（T3）、红叶石楠＋黑麦草（T4）。结果表明：植物篱系统对污染物的去除率均随坡度的增加而下降,TP、NH_3-N、COD尤为明显,当坡度由5°增加到20°时,TP的去除率由52.25%~76.75%降至33.68%~60.34%,NH_3-N的去除率由36.84%~68.33%降至34.30%~45.46%,COD的去除率由13.26%~38.69%降至3.15%~26.74%。除NH_3-N外,随污染物进水浓度的升高,植物篱对污染物的去除效果越明显,TP的去除率可由33.33%~60.11%升至57.06%~81.44%,TOC的去除率可由-0.84%~2.92%升至9.64%~17.69%,COD的去除率可由-14.75%~11.25%升至20.62%~42.33%。植物篱系统对TN、TP、NH_3-N、TOC、COD的去除效果显著优于裸土（对照系统）,在不同坡度下去除率最高分别能由12.81%升至47.02%、34.29%升至76.75%、18.27%升至68.33%、-0.93%升至11.52%、2.31%升至38.69%,在不同污染物进水浓度下分别能由15.57%升至53.05%、37.93%升至81.44%、17.60%升至64.05%、2.92%升至17.69%、-33.40%升至11.25%。总体而言,植物篱系统平均去除效果依次为T1〉T4〉T3〉T2,即红叶石楠＋小叶女贞＋黑麦草去除效果最佳,这与三种植物的地表覆盖率高、根系发达以及在功能上相互取长补短、协同固定污染物有关。

Four hedgerow systems were designed to examine their removal efficiencies of TN, TP, NH_3-N, TOC and COD in surface runoff from farm land with different slopes（5°, 10°, 20°） at different influent concentrations（low, medium, high）. The hedgerow systems included photinia fraseri ＋ lobular privet ＋ ryegrass（T1）; photinia fraseri ＋ lobular privet（T2）; lobular privet ＋ ryegrass（T3） and photinia fraseri ＋ rye-grass（T4）. Results showed that the removal efficiencies of the pollutants, especially TP, NH_3-N and COD, by these 4 hedgerow systems all decreased with increasing slopes. When the slope increased from 5° to 20°, the removal rates decreased from 52.25%~76.75% to 33.68%~60.34% for TP, 36.84%~68.33% to 34.30%~45.46% for NH_3-N and 13.26%~38.69% to 3.15%~26.74% for COD, respectively. Increasing influent concentrations increased the pollutant removal efficiencies by the hedgerow systems with an exception of NH_3-N. The removal rates of TP, TOC, COD by the hedgerows increased from 33.33%~60.11% to 57.06%~81.44%,-0.84%~2.92% to 9.64%~17.69% and-14.75%~11.25% to 20.62%~42.33%, respectively. as compared with the bare soil system. The removal rates of TN, TP, NH_3-N, TOC and COD by hedgerow systems were significantly higher than those in the bare soil, with the maximum removal rates increased from 12.81% to 47.02%,34.29% to 76.75%, 18.27% to 68.33%,-0.93% to 11.52%, and 2.31% to 38.69% under different slopes and from 15.57% to 53.05%,37.93% to 81.44%, 17.60% to 64.05%, 2.92% to 17.69% and-33.40% to 11.25% at different influent pollutant concentrations, respectively. Overall, the average removal rate of pollutants by 4 hedgerow systems was in order of T1T4 T3T2, which was related to the high surface coverage, the developed root systems and the interaction among three plants to retard the pollutants.