Characterization Of Surface Stormwater Runoff Pollution Of An Urban Area In Chongqing

Nonpoint pollution resulting from stormwater runoff has been identified as one ofthe major causes for the deterioration of the receiving waters quality, and its severityand the importance of prevention and treatment has become an internationally focus ofresearch. As one of the most important types of urban non-point source pollution, urbansurface stormwater runoff poses a significant threat to receiving surface water bodies,therefore obtained more and more concerns. In this thesis, the characteristics of urbanstormwater runoff pollution and pollutants emissions regularity were studied, the factorsthat affected surface runoff quality were summarized, and the corresponding controlmeasures were proposed to reduce non-point source pollution.The contamination of mountain urban runoff was serious, and thus, surfacestormwater runoffs from a trunk road, the secondary major road and a residential area ofa typical moutainaous urban area in Chongqing were taken as research objects.Throughsampling and monitoring, particle size distribution and the variation of a single pollutantsuch as TSS,COD,NH₃-N,TN,TP,Fe were analyzed,and the correlation equationsbetween the pollutants were put forward.First flush effect, event meanconcertration（EMC） and pollution loads were studied,and the main factors of surfacerunoff quality was also summarized,the runoff retention time was praised to controlurban runoff pollution.The main results of this study are shown as followed,1) Surface stormwater runoff pollutants in the trunk road and the residential areaare mainly particulate matter of2⁷5μm. Surface stormwater runoff pollutants of thesecondary major road, are mainly particulate matter smaller than20μm. However,smaller than0.45μm particle matter was the smallest, larger than150μm particle matterdidn’t exist in the study area.2) The most important pollutants from urban stormwater runoff were TSS andCOD pollutions, then NH₃-N and TN, and TP pollution was relatively less important.The variation of TSS, COD, Fe with rainfall time were basically the same, and thevariation of TSS, COD, Fe with rainfall time were basically the same.Finally, pollutantconcentration tended to be stable.3) First flush took effect evidently,30%⁴0%of the stormwater runoff carryingpollution loads were as follows:TSS61%⁷9%,COD60%⁷4%, NH₃-N51%⁶9%, TN48%⁶6%,TP47%⁶6%,and Fe46%⁶4%. 4) TSS, COD, Fe of runoff in the trunk road were higher than that of the residentialarea, but NH₃-N,TN,TP were just the opposite in the study area.That is,NH₃-N,TN,TPof runoff in the trunk road were lower than that of the residential area.5) Rainfall and rainfall intensity, antecedent dry days were important factors forTSS、COD,and antecedent dry days was the first. For NH₃-N, TN, TP, construction sitesand other foreign sources of pollution were first, but rainfall characteristics andantecedent dry days were second. For Fe, the impact of traffic was greater than rainfallcharacteristics.Slope took greater effect on concentration of pollutants in the first flushrunoff.6) Generally, the retention time of the trunk road runoff was18⁵5min, but theretention time of the residential area runoff was12⁴0min.