Abstract
To study the first flush effect of nonpoint source pollution in the Guangzhou community unit, runoff from roads, roofs, and green spaces during three rainfall events was collected and analyzed for pollutants. Nine runoff pollution indices were considered. The dimensionless cumulative curve of pollutant mass vs. volume, the first flush coefficient (b) and the mass first flush ratio (MFFn) were used to assess the first flush effect of different underlying surfaces. The assessment results pointed out that the roof was most prone to first flush effect. And ammonia nitrogen and phosphorus were the main pollutants in the first flush in the study area. For a quantitative analysis of the first flush, the Storm Water Management Model (SWMM) was used to simulate the hydrological effect of low impact development (LID) implementation in the community. The results showed that the first flush strength was reduced after setting LID. And LID measures, such as green roofs and sunken green spaces, contribute to flood control and rainwater purification. This research can be relevant regarding for constructing sponge cities and reducing the pollution caused by the first flush.
Highlights
Urban nonpoint source pollution refers to pollutants that flow into rivers and lakes via the runoff formed by rainfall, which pollute the receiving water in the city
If the curve is close to the diagonal line, it indicates that the pollutant concentration changed little during the early stage of runoff or that the load distribution is comparatively uniform[15]
The upward convex part of the curve of BOD5, NH3-N and total phosphorus (TP) is more obvious and that indicated that the first flush effect of these pollutant indices is more significant
Summary
Urban nonpoint source pollution refers to pollutants that flow into rivers and lakes via the runoff formed by rainfall, which pollute the receiving water in the city. As sponge city construction in China spreads, investigation of the first flush via rainfall runoff is an important basis for the study of characteristics control of urban nonpoint source pollution. Park et al.[9] estimated the probability of the mass first flush ratio (MFFn) by using the Storm Water Management Model (SWMM) to analyze the characteristics of the first flush In all of these studies, the emphasis is on the analysis of the first flush characteristics without quantitative analysis on the first flush effect. In the process of sponge city construction in Guangzhou, the principles and applications of LID have the potential to mitigate urban nonpoint source pollution and the impact of imperviousness in urban areas[11]. The land use of the area is mainly composed of roads, public squares, residential areas, and green spaces
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