The Study Of Urban Stormwater Runoff Pollution Characteristics And Uncertainties Of Data Collection In An Urban Lawn Catchment

Non-point pollution resulting from urban stormwater runoff is recognized as one of the major causes of quality deterioration in the receiving water bodies in urban areas.As an important type of urban surface,lawn accumulated lots of pollutants due to human activities such as fertilizer application,parking and recreation,which will be washed off and carried into the water bodies during rainfall events.However,few studies on characteristic of stormwater runoff in lawn catchment have been reported. On the other hand,various stormwater runoff monitoring programs have been developed to investigate the characteristic of urban stormwater runoff.The monitoring data was often used directly and uncertainties of data collection were seldom evaluated.In this study,an urban lawn catchment,located in Xiamen,Southeast China was selected to characterize the urban stormwater runoff pollution based on the analysis of the Event Mean Concentration(EMC),hydrograph and pollutographs analysis,and first flush effect analysis.In addition,the uncertainties of data collection were evaluated by the development of monitoring program,theory of error and law of propagation of uncertainty.The major conclusions are as follows.Chemical oxygen demand(COD),total phosphorus(TP),nitrate and nitrite nitrogen(NO₃₊₂^--N) are the major pollutants from stormwater runoff in the lawn catchment,whose average EMC value of 60.48 mg/L,0.44 mg/L and 1.46 mg/L,and the polliton loads are 0.6334 kg/hm²,0.0047 kg/hm² and 0.00116 kg/hm²,respectively. The peak value of pollutant concentration precedes the peak runoff flow rate in most rainfall events.The first flush effects are not obvious.The portion of total pollution mass transported by the first 30%of total runoff volume(FF30) were 36.26%for COD,26.13%for total suspended solids(TSS),28.13%for TP,and 39.03%for NO₃^--N.Based on the results of multiple regression analysis,the first flush effect of stormwater runoff from the lawn catchment was positively related to the total rainfall depth and total runoff volume. The uncertainties of specific pollutants(COD,TSS) concentration(u(C)),flow rate(u(Q)),event flow volume(u(V)),COD pollution loads(u(L)) and COD EMC (u(EMC)) was evaluated.The results show that the sampling uncertainty,storage uncertainty and analytical uncertainty of COD are 13.99%,19.48%and 12.28%, respectively.The sampling uncertainty of TSS is about 31.63%;flow rate(u(Q)) is about 12.82%.Based on the Law of Propagation of Uncertainty(LPU) Calculation,u (V),u(L) and u(EMC) of COD is about 7.03%,18.47%and 10.26%,respectively.