不透水表面坡度对溶解态污染物传输过程的影响研究

溶解态污染物是城市降雨径流污染的一个重要组成部分,揭示其在降雨径流阶段的传输过程对于城市污水治理具有重要意义。采用人工模拟降雨实验研究了不透水表面不同坡度(0.5°、1°、2°、3°、4°、5°)情况下降雨径流及溶解态污染物传输过程。结果表明:坡度越大,坡面产汇流时间越短,径流量越快达到稳定;污染物浓度随降雨径流深度增加呈逐渐减小趋势,坡度越大,初始浓度越高,衰减越快;污染物传输速率呈先增大后减小的变化规律,坡度越大,污染物传输速率峰值越大,峰值出现在径流深度为0.3~0.5mm之间;溶解态污染物传输过程符合指数冲刷模型,随着坡度的增大,冲刷系数k先线性增加,坡度大于3°基本保持稳定。相对于颗粒态污染物,溶解态污染物冲刷系数大,易被冲刷,冲刷集中发生在径流初期。

Influence of slope on the dissolved pollutant transport process over impervious surface

Disso lved pollutants are an important pa rt o f urban rainfall r unoff po llut ion. T o r eveal their t ranspo rt pro cess during the rainfall r uno ff stage is of gr eat sig nificance to urban wastew ater t reatment. I n this study, w e conducted a series o f ex peri2 ments to study the pro cesses of r ainfall- runoff and dissolved pollutant tr ansport o ver imper vio us surface at different slopes ( 01 5b, 1b, 2b, 3b, 4b, 5b) . The results show ed that the hig her the surface slope, the sho rter the time of runoff yield and concentr a2 tion, and t he faster it to ok fo r the runoff volume to reach stability. T he po llutant concentr ation would decrease as the ra infall runo ff depth increased; the hig her the slope, the higher the initial concent ratio n, and t he faster the attenuation. T he pollutant transpo rt r ate wo uld incr ease first and then decrease with time; the hig her the slope, the larg er the peak o f pollutant transpo rt rate. T he peak of pollutant transpo rt r ate appeared when the cumulative runoff depth was 01 3 to 01 5 mm. T he pollutant trans2 port process co nfo rmed to the ex po nential wash2off model. The wash2off coefficient k w ould increase linearly f irst and then re2 main basically stable w hen the slo pe was abov e 3b. Com par ed w ith particulate po llutants, the disso lv ed po llutants had a lar ger was2off coefficient and wer e more likely to be washed o ff, especially in the initia l r unoff stag e.