Temporal And Spatial Variability,Source Analysis And Risk Assessment Of POPs In The Atmospheric Dry And Wet Deposition In Shanghai

Persistent Organic Pollutants(POPs)is a kind of synthetic organic pollutants including PAHs,PCBs and OCPs with the feature of strong toxicity,bioaccumulation,perdurability,and long-distance migration.The POPs may lead to malformation,cancer and mutation,which can interfere,restrain or devastate the nervous system,immune system and endocrine system of animals and human beings.The POPs have a huge jeopardy to human health and ecosystem as well.This study was supported by bidding project of Shanghai Environmental P rotection Bureau,(2010-04).The dry and wet depositionin Shanghai was selected as the research objective and many methods were used in the research.The temporal and spatial variability features and the sources of PAHs,DL-PCBs and OCPs indry and wet deposition of Shanghai were analyzed,as well as their health risks and environment risks.The main contents were as follows:(1)This study analyzed the concentrations of PAHs in 20 sampling points from 18 administrative districts of Shanghai between November 2010 and October 2011.The concentrations of PAHs in dry and wet deposition monitored by different sites in Shanghai varied from 0.07?g·L-1 to 0.67?g·L-1.The concentrations of PAHs in wet deposition increased greatly in the first six months of 2011,while it decreased slowly from July to October.The average fluxes of PAHs in the wet deposition was 20.8?g·m-2·month-1.The concentrations of PAHs in dry deposition were between 3.60 and 92.15?g·g-1.and the average flux in the dry deposition was 123.34?·m-2·month-1.From the perspective of time and season,all the maximum values appeared in winter and spring(December,January,April and May).Sporadic dust weather exist with relative high rate in china.Using dry deposition was the main way for PAHs to migrate from atmosphere to the surface of Shanghai.(2)In wet deposition,the concentrations of DL-PCBs were between ND and 0.49?g·L-1.The maximum appeared in November,2010,while DL-PCBs were not detected in April,2011.The average concentration of DL-PCBs was 0.04?g·L-1 in wet deposition.The average flux of DL-PCBs in the wet deposition was 3.54 ?g·m-2·month-1.The concentrations of DL-PCBs in dry deposition were between ND and 0.83?g·-1.The average concentration of DL-PCBs was 0.24?g·g-1 in dry deposition.The average flux in dry deposition was 0.93 ?g·m-2·month-1.Using wet deposition was the main way for DL-PCBs to migrate from atmosphere to the surface of Shanghai.(3)OCPs was not detected in wet deposition.Nevertheless,OCPs including DDTs,HCB and Mirex were detected in dry deposition,while the Mirex was only detected at PD2 site.Concentrations of DDTs varied from ND to 0.68?g·g-1 in dry deposition.Concentrations of HCBs varied from ND to 2.49?g·g-1.Concentrations of Mirex ranged from ND to 1.81?g·g-1.There was no linear correlation between the content of three pesticides in dry deposition and meteorological parameters.In view of flux deposition,the average flux of OCPs in dry deposition was 0.78 ?g·m-2·month-1.The average flux of OCPs was 0.77?g·m-2·month-1 in the dry deposition of suburb.The average flux of OCPs was 0.65?g·m-2·month-1 in the dry deposition of urban area.The average flux of OCPs in the suburb was higher than in the urban area.(4)According to the result of source apportionment analysis,PAHs in the atmospheric wet deposition in Shanghai from November 2010 to October 2011 mainly came from the thermal power plant and the combustion of coal,gasoline and diesel,etc.As calculated using PMF model,the contribution of coal,gasoline and diesel combustion and the thermal power plant to the total PAHs pollution was 16.4%,14.7%,13.7%and 1 3.8%,respectively.The sourcesof PAHs in dry deposition was quite similar to those in the wet deposition of Shanghai during the same period.Likewise,result of PMF model indicated that the thermal power plant and the combustion of coal and gasoline accounted for about 18%,19%and 18.4%of the total PAHs,respectively.Overall,these three sources contributed approximately 55.4%to the total pollution.According to various methods,the results showed that the PAHs in the atmospheric dry and wet deposition in the city was generally derived from the combustion of gasoline and diesel.In winter and spring,the city is easily affected by the emission of PAHs pollution sources from thermal power plants.Thermal power plant was the main heat source of central heating in the northern region.From January to Marchof 2011,PAHs in atmospheric environment was significantly affected by the input of external pollution sources from the strong southward airstream.(5)According to pollution source analysis,the main component of DL-PCBs in the dry and wet deposition at each sampling point in Shanghai was penta PCBs,followed by seven PCBs.Comparison of PCBs product spectra and domestic and overseas research results,the DL-PCBs in the dry and wet deposition in Shanghai were affected by KC series product,KC600 in particular.This is consistent with homologous ratio analysis.The sum of influence factor of KC600 and Aroclor1260 in deposition was close to or over 50%in central city(20.6%of KC600 and 29.6%of Aroclor1260 in dry deposition;26.5%of KC600 and 18.7%of Aroclor1260 in wet deposition),suggesting that the main pollution source of PCBs in Shanghai might be remain of Aroclor1260 and KC600,not low-chlorinated PCBs.(6)Only three substances of the OCPs were detected in dry deposition.In the light of our previous research,historical residues accounted for part of DDTs in the dry deposition in Shanghai,and some industrial products became the new source of DDTs,especially in February and March 2011 as discovered in this study.Only HCB was detected in HCHs.Based on analysis of the temporal and spatial variation of OCPs in atmospheric deposition in Shanghai,DDTs and HCB in the dry deposition may also come from other regions by sporadic dust windexcept for the local release.Besides,according to the analysis result of sampling point PD2,the source of Mirex in the dry and wet deposition was mainly from the residues of pesticide which contained a high concentration of Mirex in surrounding surface soil.(7)Health risk assessment result showed that the risk of daily exposure to PAHs for children was 2-3 times of that for adults in terms of the wet deposition.As for the dry deposition,daily exposure to PAHs through respiratory pathway was much higher than other pathways for adults and children especially.Besides,daily exposure to DL-PCBs for adult and children in the dry deposition was much higher than that in the wet deposition.Likewise,children may bear a higher risk than adults regarding the DL-PCBs exposure through skin in the dry deposition and respiratory pathway in the wet deposition.The health risk of DL-PCBs caused by dry deposition was about 10-100 times higher than that of wet deposition.Generally,the total risk for children was higher than adults considering the exposure through both skin and the respiratory pathway.In conclusion,the risk of OCPs,inclusive of DDTs and HCHs,for children was 2-4 times of that for adults in dry deposition,and the exposure risk of HCHs was 5-8 times higher than DDTs for both children and adults.In terms of the risk acceptability level,various types of POPs are still at a very low risk level in the dry and wet deposition in Shanghai.(8)Based on the existing multi-media environmental risk model and the simulation of the fluxes of POPs in deposition in Shanghai from November,2010 to October,2011,the influence of POPs on shallow underground water was still small and in controllable range.From the regional perspective,the northern area of Shanghai was more susceptible to PAHs as the main pollutant.Based on the environmental quality standards of residential soils in Canada,the effect of POPs on shallow soils was more serious than that in shallow undergroundwater,according to the simulation of the fluxes of POPs in dry and wet deposition in Shanghai from 2010 to 2011.From the regional perspective,the CM sites at northern Shanghai were have more possibility to be pollutant by PAHs.The results of simulation showed that naphthalene,acenaphthylene and fluorene in PAHs were likely to be threatofregion's surface soil environmental qualityin the future 20-30 years.