Research On Transportation Simulation Of Urban Rainfall-Runoff Non-Point Source Pollution And The First Flush Effects

Urban runoff pollution as the second source pollution, next to the agricultural nonpointsource pollution, the direct harm from the toxic pollutants in urban runoff pollution are thatthe organic phosphorus, organic pesticides and toxic pollutants accumulate in the food chain,resulting in cute poisoning to aquatic organisms in receiving water body. After toxicpollutants in urban rainfall runoff entering into the water environment, the pollutants wouldbe in synergy to harm aquatic organisms, ultimately transferred to humans through the foodchain, and threat to human health.Based on storm runoff water quantity and quality monitoring of representative ofdifferent land use in Tongsha Reservoir catchment, pollution output process in differentrainfall situation, pollution situation in different functional district, the form of occurrencepollutants and particle size distribution in Dongguan city were analyzed. Applying principalcomponent analysis to conclude main rainfall parameters and catchment parametersinfluencing on runoff pollutant. The non-point source pollution input shift erosion model wasestablished for simulation and prediction of pollution of the functional areas. The first flusheffect of the main pollutants in the Tongsha Reservoir catchment were studyed by qualitativeand quantitative evaluation of the identification method, for urban rainfall-point sourcepollution research, controlling, and management to provide effective technical means toprovide a theoretical basis, in order to reduce the pollution of receiving water bodies. Theresults eventually show that:（1） Regulation of pollutant concentration changing with time is analogous and has asignificant time feature. Concentration peak lags behind the rainfall peak. Furthermore, thetime interval of these two peaks depends on the diversity of rainfall characteristics. The higherrainfall intensity is, the shorter time interval will be;（2） The dominant pollutants of rainfall runoff in the industrialized city are COD_cr, TSSand TP. Concentration values in industrial, mixed commercial and residential district wereclose to the density of typical sewage, and exceed the V category standard of surface waterand the pollutant loads were rather high;（3） Particulate Pb, dissolved COD_cr, particulate Ni and dissolved Zn is the main form ofrunoff pollutant output, precipitation and other methods to remove the particulate matter aslocan remove heavy metals well;（4） Max rainfall intensity （MP）, antecedent dry days （ADD）, impervious rate （Imp） arethe main variables influencing EPL, and Max rainfall intensity （MP）, antecedent dry days（ADD）, storm duration time（SDT）, storm volume（SV） are the critical variables influencing EMC;（5） Runoff particles average median diameter D50sequence is: highway> niu shan xigou> huan cheng nan road, and particle size migration in the rainfall-runoff is5-40um. Theparticles of5-40um particle size trends in runoff process is relatively large in the first30minutes of heavy rain events; The correlation coefficien between runoff pollutantconcentrations and particle size of the smallest fine particles （<5um） is the largest, and thecorrelation coefficient between the pollutants concentration and particle size get smaller withthe particle size increasing, indicating the pollutants mainly adsorption to fine particlessurface;（6） Urban runoff pollutants washed mathematical models through the linear function andthe gamma function has been constructed, the model equation is: NewConc.[V_nRU（t）]=δ+V_nRU（t）·{γ+β·Exp×[-α·V（nRU）（t）}，VnRU（t）, the simulated pollutants concentration is close toexperimental results, to meet the requirements of model checking;（7） When max rainfall intensity and rainfall depth are greater, the first flush effect will bemore distinct; parallel result is that the ground of impervious area is more likely to producerainfall runoff pollution. Applying two kinds of graphic recognition method including thedimensionless cumulative M （V） and MFFn rate curve method, the results contrasting caneffectively eliminate intuitive tiny error caused by different graphics recognition;（8） Each pollutant concentration from highway and roof with dimensionless rainfallamount changing trend is similar. And the seasonal flushing effect happened in the pavementand roof. Seasonal flushing effect of heavy metal strength is larger than that of the basic waterquality parameters;（9） Using FF40as the reference value of early period runoff retention, intercepting theearly40%of runoff volume would be more effective and economical than intercepting thewhole.