Evaluation Of Water Quality Safety Of Rainfall Runoff On The Different Underlying Surface

With the rapid population growth and urban expansion,the demand of urban water resource has been increasingly urgent,which result in the shortage of water and serious water pollution.Much attention has been paid to the water quality.Based on the detection of routine indicators,the biological toxicity tests have become a promising means for the water quality monitoring,which can intuitively reflect the toxicological influence of pollutants and the potential ecological impacts.Therefore,the routine water quality methods combined with biological toxicity test are more suitable for the water quality.This work aimed to establish a safety evaluation method of rainwater quality based on biological toxicity and routine methods,which can test the comprehensive biological effects of all coexisting contaminants in the water to evaluate the safety of rainwater.The analytical methods in the rainwater quality was divided into routine index test and biological toxicity test.The routine test analyzed turbidity,pH,total nitrogen,total phosphorus,solid suspension and COD according to the national standard method.The biological toxicity test selected SOS/umu genotoxicity and the acute toxicity were conducted.The positive reference materials were also tested,respectively.The correlation coefficient R² is greater than0.95.In addition,the rain samples from roof and road in May,June and July were collected,respectively.The results of routine index test were as follows.The quality of rainwater on roof and road surface gradually decreased with the continuous rainfall time,and poor water quality early in the rain.The quality of the rainwater from the roof and road was quite different.The water quality from the asphalt roof was better than that from the road.The rain samples from roof and road had genetic toxicity.The toxicity equivalent concentrations of samples from the roof and road?4-NQO as positive reference?respectively fell from 269.0 ng/L and 177.6 ng/L to 21.0 ng/L and 142.1 ng/L in May.The toxicity equivalent concentrations of samples from the roof and road fell from 153.7 ng/L and 391.3 ng/L to 64.7 ng/L and 89.0 ng/L in June,respectively.The toxicity equivalent concentrations of samples from the roof and road fell from104.5 ng/L and 359.2 ng/L to 22.5 ng/L and 12.0 ng/L in July,respectively.The carcinogenic risk evaluation of rain samples in the range of 10^-410^-6 demonstrated the value-at-risk,which had low potential threat to the surrounding residents.The bio-toxicity of all rain samples was conducted with photobacterium.The calculated results of EQC_Zn²⁺of roof and road rainwater samples were 0-0.841 mg/L and 0-0.68 mg/L,respectively.The calculated results of EQC_Hg²⁺of roof and road rainwater samples were 0-75.75?g/L and 0-6.17?g/L,respectively.TU value of the evaluation results showed that the average TU values of rainwater samples points were less than 0.4,belonging to class?,non-toxic.In this study,YAAHP software of analytic hierarchy process was used to evaluate the rainwater quality of different underlying surfaces and established the quality safety evaluation model.The weight of the model was calculated by the order of:turbidity>COD>suspended solids>TN>TP>pH.The model can make a comprehensive judgment of several factors that affect the water quality of rainwater,and the evaluation results was accordance with the previous study,which can be used to evaluate the water quality in rainfall runoff.