Characteristics Of Water Quality And Source Analysis Of Fluorescent Dissolved Organic Material In Wujin District Surface Water

Wujin District is located in the northwestern area of Lake Taihu,connecting Lake Taihu and the Yangtze River with complicated and overlapping river network.With the rapid development of regional urbanization and industrial economy,a large number of pollutants were discharged into surface water,resulting in water pollution.Meanwhile,a large amount of fluorescent dissolved organic material(FDOM)in production and domestic wastewater were discharged into natural water bodies,leading to change of FDOM composition and content in surface water and endangering the ecological health of the water environment,by affecting the biochemical cycle and degradation of organic matter.In order to improve water environment management in Wujin District,further to protect the ecological health of the water environment of Lake Taihu,grasping the characteristics of regional water quality and analyzing the source of FDOM are significant.Based on collecting surface water at 60 sampling sites and drainages from 12 pollution sources in Wujin District during 2019,this study detected water quality parameters concentration(month/time)and heavy metals concentration of surface water(quarter/time),respectively,analyzing the distribution characteristics of water quality in the area.Furthermore,water quality index method(WQI),health risk assessment of heavy metals,principal component/factor analysis(PCA/FA)and positive matrix factor(PMF)receptor model were used to assess the surface water pollution status in Wujin District.Meanwhile,quarterly excitation-emission matrix fluorescence spectroscopy of surface water and pollution source wastewater were detected,analyzing the characteristics,composition and distribution of surface water FDOM,summarizing the characteristics of excitation-emission matrix fluorescence spectroscopy of typical pollution sources.Finally,the excitation-emission matrix fluorescence spectroscopy of surface water were compared with that of pollution source,to analyze the source of surface water FDOM.The research results can provide references for pollution control and water environment ecological treatment in Wujin District.The results of annual water quality parameters and heavy metals concentration distribution characteristics in whole area showed,the concentrations of all water quality parameters were higher in Cailing River.Yongan River and the northern canal area during winter and spring.Chemical Oxygen demand,total phosphorus,arsenic and iron concentrations increased in Zhushan Bay and Lake Ge during summer.On this basis,the WQI and health risk assessment of heavy metals were used to assess regional surface water pollution status.The WQI results indicated that in the Cailing River,Yongan River,Wunan River and the northern canal area,the water quality were relatively poor.The heavy metals in surface water were basically negligible health risk,while arsenic in lakes had carcinogenic risk.Based on PCA/FA and PMF receptor model,the potential pollution sources influencing water quality in the area were analyzed,the results showed that the contribution rates of each potential pollution source were as follows:industrial sources(27.9%)>agricultural non-point sources(25.5%)>other sources(23.6%)>Algae growth(23.0%).The characteristics,composition and distribution of FDOM in aquatic environment were studied by using excitation-emission matrix fluorescence spectroscopy couple with multiple spectral analysis methods and multivariate statistical analysis methods.3 protein-like components and 3 humic-like components were derived from excitation-emission matrix fluorescence spectroscopy couple with parallel factor analysis(PARAFAC),which can comprehensively reflect the composition and distribution of FDOM in water.Impacted by anthropogenic activities and terrestrial input,as well as autochthonous impact,the fluorescent composition of each point were different.Overall,the content of fluorescent components in regional tributaries were higher,more affected by human activities and terrestrial input than mainstreams.Consequently,the correlation between water quality parameters and fluorescent composition was studied,Fn(355)can be used to reflect variation of COD concentration,nitrogen and phosphorus nutrient elements were positively correlated with humic-like fluorescent components.On this basis,further analysis of the excitation-emission matrix fluorescence spectroscopy of the pollution source couple with the fluorescence regional intergration showed that the excitation-emission matrix fluorescence spectroscopy of various pollution sources have certain differences due to material compositions.Meanwhile,the the excitation-emission matrix fluorescence spectroscopy characteristics of different pollution sources were summarized by peak-picking method and AFE analysis.Based on the characteristics of the excitation-emission matrix fluorescence spectroscopy of different pollution sources,source analysis of FDOM was performed in typical river basins in the region(Cailing River,Yongan River and the northern canal area).The results show that Cailing River was affected by textile wastewater and domestic sewages;Yongan River was affected by textile wastewater,domestic sewages and agricultural sources;The northern canal area was affected by industrial sources,domestic sewages and agricultural sources.