基于原位调控的排水沟渠深潭氮磷滞留实证研究

The nitrogen and phosphorus retention in pools of drainage ditches based on insitu manipulation

为检验小河流氮磷营养盐滞留中深潭地貌作用,在合肥市境内两条源头排水沟渠,开展深潭容积和水深的土袋原位调控实验,并利用示踪实验和模型模拟技术,估算了调控前后深潭渠段的暂态存储潜力和氮磷滞留能力.结果表明:土袋调控情形下,板桥河支流深潭渠段F_(med)^(200)下降85.42%,A_(s)/A比值降幅达43.49%;二十埠河支流F_(med)^(200)下降82.67%~89.36%,A_(s)/A比值降幅达31.59%~39.78%,表明两条排水沟渠暂态存储潜力显著下降.与空白对照情形相比,板桥河支流深潭渠段NH_(4)^(+)吸收长度Sw增幅达18.38%,PO_(4)^(3-)增幅达201.38%;二十埠支流源头NH_(4)^(+)增幅为15.91%~19.92%,PO_(4)^(3-)增幅为7.05%~24.40%,意味着深潭容积减小、水深下降明显弱化了深潭地貌的氮磷营养盐滞留能力.就滞留率而言,调控情形下两条排水沟渠深潭渠段NH_(4)^(+)滞留率下降了14.54%~31.53%,PO_(4)^(3-)下降了16.93%~53.09%,直观展示了调控对深潭地貌营养盐滞留的影响.总之,案例结果证明了深潭地貌在小河流氮磷滞留中的正面效应.

To testify to the effect of pools on the retention of nitrogen(N)and phosphorus(P),we selected two drainage ditches in two headwater streams in Hefei to in-situ manipulate the volumes and depths of pools by using soil-packed pockets.A pulse injection experiment was performed with nitrogen(NH4Cl),phosphorus(KH2PO4),and a conservative tracer(NaBr)before and after manipulation,respectively.The potential of both transient storage and nutrient retention of the stream reach were estimated based on water quality simulation.Results showed that both F_(med)^(200) and A_(s)/A ratios of the manipulated pools in the Banqiao River declined by 85.42%and 43.49%,respectively,while those in the Ershibu River were decreased by 82.67%~89.36%and 31.59%~39.78%,respectively,which indicated that the transient storage potential in the stream reach with pools was depressed after manipulation.Compared with the pre-manipulation conditions,uptake lengths(Sw)of the stream reach in the Banqiao River were increased by 18.38%for ammonia(NH_(4)^(+))and 201.38%for phosphate(PO_(4)^(3-)),and in the Ershibu River,Sw was increased by 15.91%~19.92%for NH_(4)^(+)and 7.05%~24.40%for PO_(4)^(3-),suggesting that reduced volume and depth of pools dramatically weakened the N and P retention capacities in both streams.Moreover,the retention rates of the pools in both streams after manipulation were decreased by 14.54%~31.53%for NH_(4)^(+)and 16.93%~53.09%for PO_(4)^(3-),which intuitively exhibited the effect of manipulation on nutrient retention in pools.In summary,the case study demonstrates the positive effect of pools on N and P retention in streams.