| To investigate urban non-point source pollution and pollution characteristics of urban runoff, six rainfalls were monitored and calculated for Event Mean Concentration (EMC) and Event Pollutant Loads (EPL) per unit area for the upstream of Tangxi River, M(V) curve was used to study the first flush effect, three-dimensional fluorescence spectroscopy combined with ultraviolet-visible absorption spectra was employed to investigate the variation characteristics of dissolved organic matter (DOM) in runoff. The results showed that:(1) The performance of variation trend for pollutant concentration in separate system is that drainage system in the early formation of the runoff reached a peak and then decreased, the fluctuation of pre-concentration was significant.The size of the catchment area, rainfall characteristics and the sediment in pipeline would influence the pollutant concentration. Early runoff instantaneous concentration of major pollutants were higher than the V class of the Water quality, and with the continued erosion and runoff dilution effect it would gradually reduce, when rainfall decreases, post-dilution was weakened, the concentration of pollutants would become with upward trend.(2) The average value of each pollutants'EMC in research area were:TN (4.87±1.53) mg/L, TP (0.59±0.13) mg/L, CODCr (85.82±50.98) mg/L, SS(161.05±161.42) mg/L, NH4+-N (2.15±0.88) mg/L. The average value of each pollutants'EPL were:TN (14.14± 22.65) mg/L, TP(2.70±5.13) mg/L,CODCr (223.79±323.93) mg/L,SS (1134.49±2357.14) mg/L, NH4+-N (6.51±11.33) mg/L, different rainfall events'EPL was quite different from each other.(3) The physical methods which is aimed to remove SS would also effect on TN, TP, NH4+-N and CODCr removing. There was a significant negative correlation between the EMC of TN and rainfall as well as the average and maximum rainfall intensity. After estimation, the study area in following 3 months:June, July, August had a total of 10.38t TN,2.29t TP,1022.43t SS, 161.70t CODCr and 5.18t NH4+-N flowed into the Chaohu Lake with rain runoff in 2015.(4) Runoff flush in the study area belongs to the drainage pipe flush, first flush process was complex, erosion intensity is weak, FF30> 80 erosion criteria for conduit was too strict, FF50> 50 was better as the first flush criteria. Different rainfall events had different flushing circumstances, the intensity of first flush in 26 June rainfall was relatively high; in a rainfall event, flush situation of different pollutants would vary, only mean value of NH4+-N's FF50 was less than 50, first flush of SS and CODCr were relatively significant. Only TP appeared flush phenomenon in the six rainfall events. first flush effect of SS and CODCr are relatively significant or five contaminants only TP rainfall in six rainfall processes in the first flush phenomenon have occurred, the average value of each pollutant FF50 comparative results is SS> CODCr> TP> TN> NH4+-N. No correlation existed between the magnitude of first flush and rainfall characteristics.(5) The aromaticity of DOM and the proportion of hydrophobicity organic of DOM in runoff on June 16 were unstable, the molecular weight of DOM changed little in that rainfall event. The relative content of each component in the DOM in runoff had significant fluctuation in the early period and later stabilized gradually, essentially unchanged. Plastein materials like tryptophan had the max relative content, which is about 35%, humic-like substance had the least relative content, which is between 5% to 10%.The humic-like substance in runoff is mainly of outer-source,the degree of humification was low and relatively stable;DOM in runoff was mainly of self-source may under the influence of human activities. |
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