稻秸秆添加强化沉水植物湿地对农田径流中不同形态氮的去除效果

Removal efficiency of different forms of nitrogen from farmland runoff by adding rice straw in submerged plant wetland

为提升稻田周边湿地对农田径流中不同形态氮的净化效率,有效拦截农田面源污染导致的氮磷流失,采用农业废物稻秸秆为有机碳源与沉水植物组合构建强化湿地系统,共设置不种植苦草且不添加稻秸秆(NS)、只种植苦草(VN)、只添加稻秸秆(SS)和种植苦草并添加稻秸秆(VS)4个处理,研究强化湿地对不同形态氮农田径流的净化效果与机制。结果表明:1)在处理以氨氮(NH_(4)^(+)-N)为主要氮形态的农田径流时,VN和VS对废水中TN和NH_(4)^(+)-N的去除率显著高于其他处理(P<0.05),表明种植苦草是提升湿地对NH_(4)^(+)-N农田径流净化效果的主要因素;2)处理以硝态氮(NO_(3)^(-)-N)为主要氮形态的农田径流时,SS和VS对废水中TN和NO_(3)^(-)-N的去除率显著高于其他处理(P<0.05),表明添加稻秸秆显著提升了湿地对NO_(3)^(-)-N农田径流的净化效果。3)湿地中只种植苦草时对NO_(3)^(-)-N去除效果不佳,只添加稻秸秆时对NH_(4)^(+)-N去除效果较差,种植苦草并添加稻秸秆对2种形态氮均有较好的去除效果,同时二者对磷的去除效果与只种植苦草的湿地无显著差异。因此,稻秸秆添加强化沉水植物湿地在拦截净化农田面源污染中具有推广应用的潜力。

In order to improve the purification efficiency of different forms of nitrogen in farmland runoff by constructed wetlands(CWs)around the paddy field,and effectively intercept nitrogen(N)and phosphorus(P)runoff loss caused by non-point source pollution in farmland,agricultural waste rice straw was used as organic carbon source to enhance the purification capability of CWs planted with submerged plant Vallisneria natans(Lour.)Hara.Four kinds of CWs were set up:without submerged plant(NS),only planted with V.natans(VN),only added with rice straw(SS)and with V.natans planted and rice straw added(VS).The purification performance and mechanism of CWs were studied when treating farmland tail water with ammonia nitrogen(NH_(4)^(+)-N)or nitrate nitrogen(NO_(3)^(-)-N)as the main N components.The results showed that the purification efficiencies of TN and NH_(4)^(+)-N in VN and VS were significantly higher than those of NS and SS(P<0.05)in the treatment of farmland tail water with NH4 the main nitrogen form,which indicated that planting V.natans played a crucial role in the removal of NH_(4)^(+)-N as+-N.The average removal rates of TN and NO_(3)^(-)-N by SS and VS were significantly higher than those of NS and VN CWs(P<0.05)in the treatment of farmland tail water with NO_(3)^(-)-N as the main nitrogen form,suggesting that the addition of rice straw significantly improved the reduction of NO_(3)^(-)-N.CWs only planted with V.natans had poor removal efficiency on NO_(3)^(-)-N.While the removal of NH_(4)^(+)-N was limited in CWs only added with rice straw.VS showed excellent purification performances on the removal of two forms of N.At the same time,VS showed similar TP removal efficiency to VN.The above results suggested that it was a feasible way to apply this kind of CWs to control agricultural non-point source pollution.