Reduction effect of sunken green space on urban rainfall-runoff pollution

Based on monitoring 14 rainfall-runoff samples in 7 rainfall events, the reduction effect of sunken green space on urban rainfall-runoff pollution was discussed, and effect of influent loading, soil and land cover of sunken green space, and rainfall duration on pollution reduction rate was analyzed. Sunken green space had a better decontamination efficiency when the event mean concentration of COD, NH₄⁺-N and TP were 56.0~216.0, 0.27~2.97 and 0.20~0.95mg/L, respectively. The average removal rate of COD, NH₄⁺-N and TP were 52.21%, 48.98% and 47.35%, respectively. The decontamination process could be divided into two periods. In the first one hour since rainfall, the relationship between the concentrations of COD, NH₄⁺-N and TP in influent and effluent followed linear equation. And then, the pollution reduction rate agreed with second-order kinetic model. The pollution reduction rate increased with the extension of rainfall duration. The integrated pollution reduction rate of COD, NH4+-N and TP could increase from about 40% to 65% when rainfall duration increased from about 3 to 20 hours.