Study On Prioritization Of Pollutants In Nanjing Chemical Industrial Park

The chemical industry is one of the pillar industry in China,Chemical Industry Park(CIP),as a concentrated zone of chemicals,has developed rapidly in recent years.Hundreds of CIP have been established alongside the Yangtze River,and a large amount of industrial wastewater is discharged into the Yangtze River every day.Different chemical production in CIP resulted in different compositons of the wastewater,so,priority contaminants in different CIP need to be investigated in order to effectively conduct environmental management for CIP and protect the surrounding environment of CIP.This study analyzed the main contaminants in wastewater from the wastewater treatment plant(WWTP)of Nanjing Chemical Industry Park,investigated the levels and distribution of the target contaminants in wastewater and surrounding rivers,and ranked the prioritization of pollutants using risk assessment.The results of this study can provide an important guidance in screening of priority pollutants in CIP.The solid-phase extraction and gas chromatography-mass spectrometry method were used to determine 17 kinds of main pollutants in wastewater in this study.Through the optimization of the pretreatment method and instrument analysis condition,the qualitative and quantitative methods were established for the target pollutants.The recoveries of the method ranged between 67.5%-113.9%and the detection limits ranged 0.60?g/L?10.51?g/L,which could meet the requirments of the detection of pollutants in the environmental samples.The water samples including wastewater from WWTP and surface water in surrounding rivers were collected and analyzed.The results showed that higher concentrations of pollutants—in the wastewater were mainly 2-ethylhexanol,N,N-dimethylaniline,tetramethyl-succinonitrile,4-methoxy-4-methyl-2-pentanone,1,2-dibromo-3-chloropropane,bis(2-chloro-l-methylethyl)ether,Phorone,N-methylaniline.The results of the five sampling analysis of the WWTP is that the total concentration of 17 target pollutants in the effluent was between 9.72?g/L-21464.24?g/L.Differences in the concentration of pollutants between influent and effluent in WWTP showed that the removal rates for different target contaminants varied greatly(12%-98%),which reflects the complex and greatly changing characteristics of wastewater in the industrial concentrated area.The 17 target contaminants were analyzed in four different rivers in January,March and May,respectively.In the Chuhe River,the main pollutants are 4-methoxy-4-methyl-2-pentanone,phorone and bis(2-chloro-l-methylethyl)ether with the highest concentrations 18.46 g/L,5.57 g/L and 3.63 g/L,respectively.The total concentration of pollutants in May is the lowest compared to that in January and March,and showing an increase trend from upstream to downstream.In the Macha River,the main pollutants are phorone,bis(2-chloro-l-methylethyl)ether,2-ethylhexanol,4-methoxy-4-methyl-2-pentanone and tetramethyl-succinonitrile with the highest concentrations 12.57?g/L,0.57?g/L,0.37?g/L,0.33?g/L and 0.25?g/L,respectively.The total concentrations of pollutants were different in different months with Jan>Mar>May and maintaining a relatively small upward trend from upstream to downstream.In the Yuezi River,the main pollutants are 1,2,3-trimethyl-benzene,4-methoxy-4-methyl-2-pentanone,phorone,2-ethylhexanol,tetramethyl-succinonitrile and bis(2-chloro-l-methylethyl)ether with the highest concentrations 32.41 ?g/L,15.58?g/L,6.28?g/L,1.92pg/L,1.55?g/L and 0.29?g/L,respectively.The total concentrations of pollutants showed a significant increase trend from the upstream to the downstream,and were different in different months with Jan>Mar>May.In the Huangchang River,the main pollutants are 4-methoxy-4-methyl-2-pentanone,bis(2-chloro-l-methylethyl)ether,N-methylaniline,2-ethylhexanol and tetramethyl-succinonitrile with the highest concentrations 12.35?g/L,4.07?g/L,0.58?g/L,0.35?g/L,0.37?g/L and 0.28?g/L,respectively.The total concentrations of pollutants were relatively stable,and showed an increase trend from the upstream to the downstream.According to the physicochemical parameters of 17 target pollutants including the octanol water partition coefficient,acute toxicity(fish,Daphnia and algae),half-life,bioaccumulation and environmental exposure concentrations,the risk of the pollutants in the WWTP and surrounding rivers were ranked by three different methods which include the toxicity unit method,the risk entropy method and the comprehensive evaluation method.Six priority pollutants including 1,2-dibromo-3-chloropropane?bis(2-chloro-1-methylethyl)ether,2-ethylhexanol,N-methylaniline,phorone and isophorone in the WWTP were screened by Integrating the three evaluation methods,but the risk values for the target pollutants in surrounding rivers are far below the risk value in the WWTP,and no obvious priority order for these contaminants.