城市绿地削减降雨地表径流污染效应的试验研究

针对城市降雨地表径流造成的非点源污染已成为城市收纳水体水质恶化和生态退化的主要因素这一现状,利用室内土壤柱模拟城市绿地对典型降雨地表径流污染的削减效应,研究土地覆被、径流污染物浓度、土层厚度以及水力负荷与停留时间对污染削减率的影响.结果表明,在低、中和高3种典型降雨地表径流污染浓度水平(COD为44.5、144.3、487.2 mg.L-1;NH4+-N为4.27、11.44、36.61 mg.L-1;TP为0.98、2.85、9.66 mg.L-1),8.15、7.13和6.12 cm.h-1的进水负荷持续1 h条件下,城市绿地的污染削减能力良好、稳定,对照组对COD、NH4+-N和TP的平均削减率分别达到33.41%~37.14%、58.74%~61.49%和63.65%~67.08%;受复氧能力和水力停留时间的限制,绿地覆被植物对污染物削减率的影响不明显;随着降雨地表径流污染浓度水平的增加,绿地的污染综合削减率保持在50%~60%左右,略有增大趋势;绿地对降雨地表径流污染的削减主要发生在深度50~70 cm的土层之上.

Experimental Study on Rainfall-Runoff Pollutant Reduction by Urban Green Space

Based on the state that non-pointed pollution caused by urban rainfall-runoff was one of the major factors which led to urban surface water contaminated and ecology deteriorated, a soil aquifer treatment system was built to experimentally study the pollution reduction effectiveness of green space, and the impacts of land cover, influent concentration, soil depth, hydraulic loading rate and residence time were analyzed. The results exhibit that green space has a better and stabilized ability to reduce three representative urban rainfall-runoff pollution concentrations, which COD are 44.5, 144.3, 487.2 mg·L^-1, NH⁺₄-N are 4.27, 11.44, 36.61 mg·L^-1 and TP are 0.98, 2.85, 9.66 mg·L^-1, respectively, and with 8.15, 7.13 and 6.12 cm·h^-1hydraulic loading rate, respectively. The pollution reduction rates of COD, NH⁺₄-N and TP by green space are 33.41%-37.14%, 58.74%-61.49% and 63.65%-67.08%, respectively. The effect of land cover to pollution reduction rate is not significant because of the limitation of oxygen and hydraulic residence time. When pollution concentration increases, the comprehensive pollution reduction ability of green space is kept in 50%-60%, with a little increased tendency. Pollution reduction process happens mainly in the upper layer of the green space soil with a depth of 50-70 cm.