不同降雨强度下铅在屋面径流中迁移规律的模拟研究

针对面源污染日趋严重的实际问题,研究采用模拟降雨的方式与铅同位素示踪技术,对不同降雨强度下不同来源铅(屋面累积颗粒物源与湿沉降源)在屋面径流系统中的迁移与分配特征进行了探讨.结果表明屋面径流系统中不同来源铅的行为特征受降雨强度影响较大,降雨持续时间为30 min,雨强分别为9.8、21.8、42.5、82.2 mm·h~(-1)时,屋面累积颗粒物源铅被冲刷进入径流的速率分别为0.275、0.434、0.595、1.019mg·m~(-2)·h~(-1),湿沉降源铅进入径流的速率分别为0.102、0.269、0.642、1.288 mg·m~(-2)·h~(-1).降雨强度对不同来源铅在屋面径流系统中的分配特征有显著影响.不同降雨强度下累积颗粒物源铅在屋面径流,屋面剩余颗粒物,屋面材料中的分配比例依次为(9.8 mm·h~(-1))29.0%、33.5%、37.5%;(21.8 mm·h~(-1))45.0%、19.0%、36.0%;(42.5 mm·h~(-1))61.2%、7.8%、31.0%;(82.2 mm·h~(-1))92.9%、2.2%、4.9%;湿沉降源铅相应归趋中的比例依次为(9.8 mm·h~(-1))62.6%、36.3%、1.1%;(21.8 mm·h~(-1))74.1%、14.3%、11.6%;(42.5 mm·h~(-1))90.7%、2.6%、6.7%;(82.2 mm·h~(-1))94.0%、0.5%、5.5%.

Characterizing the transport and distribution of lead in roof-runoff system under different rain intensity

The mobilization and distribution of lead originating in roof dust and wet deposition was investigated within a roof dust-rooftop-runoff system. The results indicate that the behavior of lead with different sources in roof-runoff system was affected by the rainfall intensity. When the rainfall duration was 30 min and the intensity was 9.8, 21.8, 42.5, 82.2 mm·h^-1, respectively, the wash-off rate of lead derived from roof dust was 0.275, 0.434, 0.595, 1.019 mg·m^-2·h^-1, respectively, the corresponding value for wet deposition was 0.102, 0.269, 0.642, 1.288 mg·m^-2·h^-1, respectively. As regards to the lead distribution, the lead from different sources showed different distribution patterns in the solids (dust particulates) and liquids (runoff water) of the rooftop runoff system. Additionally, the distribution pattern of input lead was significantly influenced by the rainfall intensity. Approximately, 29.0%, 45.0%, 61.2%, and 92.9% of the total lead originating from the roof dust appeared in the runoff water for rainfall events with the above rainfall intensity, and 62.6%, 74.1%, 90.7% and 94.0% of the total lead originating from wet deposition appeared in the runoff water for the corresponding events, respectively.