河岸草本缓冲带对模拟径流中污染物的净化

摘要

Three species of local plants (Cynodon dactylon,Lysimachia barystachys Bunge and Cynodon dactylon × C.transadlensis ‘ Tifdwarf') in North China were selected for the riparian buffer strips beside Chaobai River to perform pollutants removal,and the effect of buffer zone width,hydraulic loading and influent concentrations on the purifying ability of buffer zone was discussed with artificial surface runoff.The results showed that the pollutants concentrations in the runoff decreased with the increase of the buffer strip distance,and the faster in the front,the gradually slowdown in the later.The removal of SS was mostly achieved in the first 3 m,and the decrease of COD and TP concentrations mainly occurred in the first 6 m,while TN in the first 9 m.Hence,it was inferred that the basic purifying ability could be obtained if the minimum width of buffer zone was set up as 9 m.The removal efficiencies of NH4+-N by buffer strips with Cynodon dactylon,Lysimachia barystachys Bunge and Cynodon dactylon × C.transadlensis ‘ Tifdwarf'were 50.6％,32.0％ and 40.4％,respectively at the 15 m of strip width.Generally the ability of strip with Lysimachia barystachys Bunge to purify nitrogen and phosphorus was less than the other two kinds of strips.The buffer strips were qualified to remove SS (more than 70％) for the buffer strips with different hydraulic loading and influent concentrations.However,a higher influent concentration of NH4+-N could lead to a lower removal efficiency for all the three buffer strips.In addition,the removal of NO3--N and dissolved phosphorus (DP) was not as effective as the other pollutants probably due to their low influent concentrations,less than 1 mg/L.The effluent concentrations of NO3--N and DP were even higher than the influent concentrations in the buffer strips of Lysimachia barystachys Bunge.%选择华北地区3种常见草本植物——狗牙根、虎尾草和天堂草,通过人工配水模拟地表径流,在北京潮白河河岸设置径流试验,研究河岸带宽度、水力负荷和进水浓度对不同缓冲带截污能力的影响.结果表明:模拟径流中污染物均随缓冲带沿程距离增加有降低趋势,且前段下降较快,后段下降逐渐趋缓.SS的去除主要发生在沿程前3 m,TP和COD的去除主要发生在前6 m,TN的去除主要发生在9 m以内.若缓冲带的宽度设置受限,为保证一定的截污效果,宽度不应小于9 m.狗牙根、虎尾草和天堂草缓冲带在沿程15 m处对NH4+-N的去除率分别为50.6％、32.0％和40.4％,总体上狗牙根和天堂草对N、P的去除能力优于虎尾草.不同水力负荷和进水浓度下,草本缓冲带均能有效截留径流中的SS,去除率均在70％以上,而NH4+-N的去除受进水浓度的影响较大.由于模拟径流中N03--N和溶解性磷(DP)进水浓度低于1 mg/L,缓冲带对两者的去除效果较差,特别是虎尾草缓冲带,出现了出水浓度高于进水的情况.