生物滞留对城市地表径流磷的去除途径

根据武汉城市地表径流水文变化以及磷污染特征,通过1 a模拟运行监测,研究了生物滞留种植植物(狼尾草)、设置饱和带对城市地表径流溶解性磷(PO3-4-P)去除的影响及去除途径.结果表明,生物滞留采用75%河砂与25%当地黄棕壤混合基质,对地表径流PO3-4-P的平均去除率可达到90%以上.生物滞留种植狼尾草可显著降低出水PO3-4-P浓度.生物滞留设置饱和带可进一步提高对PO3-4-P的去除,不影响出水TP浓度.生物滞留通过基质吸附去除地表径流中的磷,表现为0~22.5 cm基质剖面中植物有效磷的增加,约占试验期间进水磷负荷的50%.从生物滞留系统磷输入(进水)与输出(出水与植物地上部分)角度分析,种植狼尾草一个生长周期地上部分吸收的磷可占进水磷负荷57.1%~76.1%,定期收割植物地上部分可作为城市地表径流磷可持续管理的主要途径.

Urban Runoff Phosphorus Removal Pathways in Bioretention Systems

The role of vegetation and saturated zones in stormwater-dissolved phosphorus (PO₄^3--P) removal was investigated using bioretention microcosms. Nine bioretention columns were dosed with synthetic stormwater under various hydrological conditions and phosphorus loading rates and monitored over a 12-month period. Remarkable phosphorus removal (>90%) was achieved using the mixed filter media of sand and local soil, with or without vegetation. Bioretention columns in which P. alopecuroides was planted could significantly enhance PO₄^3--P removal. The saturated zones could also reduce the effluent PO₄^3--P concentrations, but had no significant effect on total phosphorus removal. Approximately 50% of the input phosphorus retained in the filter media was extracted in the top 0-22.5 cm, where it could be available for uptake by plants. Further, 57.1% to 76.1% of the total phosphorus input recovered in the total plant biomass was stored in the above-ground shoots. Thus, periodic harvesting of shoots can be a sustainable method of phosphorus removal from stormwater bioretention systems.