川中丘陵区生态沟渠对径流无机含氮化合物的截除效果

Interception Effect of Ecological Ditches on Inorganic NitrogenousCompounds from Runoff in Hilly Areas of Central Sichuan

为研究山区村镇居民分散式污水生态净化技术中生态沟渠对径流无机含氮化合物的截除效果,以川中丘陵区绵阳市盐亭县林山乡为例,采用野外观测法和实验分析法,对生态沟渠不同植物段水样中无机含氮化合物进行了监测,并测定其削减效率。研究结果表明:(1)生态沟渠对不同形态氮去除率大小为:硝态氮(NO^(-)_(3)-N)>总氮(TN)>亚硝态氮(NO^(-)_(2)-N)>铵态氮(NH^(+)_(4)-N);(2)污水经过沟渠植被净化后,无机含氮化合物浓度在总体上呈下降趋势,并呈阶梯状递减;无机含氮化合物的浓度均由入口处的超标排放削减为符合国家居民污水排放三级标准;(3)从空间尺度来讲,各植被段对无机含氮化合物的去除贡献率为:美人蕉段(A_(1)—A_(2))>杂草段(A_(2)—A_(3))>铜钱草段(A_(4)—A_(5))>菖蒲段(A_(3)—A_(4));(4)沉积物营养盐向上覆水体释放无机含氮化合物主要以NH^(+)_(4)-N为主。生态沟渠对径流无机含氮化合物具有较好的去除作用,可作为一项重要的非点源污染防控技术。

Nitrogen is the key factor of water eutrophication.Linshan village of Yanting county in Mianyang city is taken as an example to investigate the effect of ecological ditches on inorganic nitrogenous compounds from runoff by the decentralized sewage ecological purification technology in mountain villages.Inorganic nitrogenous compounds in water samples from different plant sections of ecological ditches are monitored and their reduction efficiency is determined by field observation method and experimental analysis.The results show as follows:(1)The removal rate of ecological ditches on nitrogen in different forms goes like NO^(-)_(3)-N>TN>NO _(2)--N>NH^(+)_(4)-N;(2)The concentration of inorganic nitrogenous compounds have generally decreased in a ladder pattern after the sewage is purified by ditch vegetation;The concentration of inorganic nitrogenous compounds at the entrance of ditches are reduced from excessive emission to Grade III standard of national sewage discharge;(3)In terms of spatial scale,the contribution rate of vegetation segment on removing inorganic nitrogenous compounds is in the order of canna(A_(1)—A_(2))>weed(A_(2)—A_(3))>copper weed(A_(4)—A_(5))>acorus gramineus(A_(3)—A_(4));(4)The inorganic nitrogenous compounds released from sediment nutrient salt to overlying water body is mainly NH^(+)_(4)-N.As ecological ditches have better interception effect on inorganic nitrogenous compounds from runoff,it will be an important non-point source pollution prevention and control technology.