| Volatile Chlorinated Hydrocarbons(VCHs)played a key role in the formation of complex air pollution,stratospheric ozone depletion and global climate change,and finally posed a threat to human health.Moreover,VCHs)was one of the important and widely detected components of volatile organic compounds(VOCs)and there were many kinds of VCHs.such as chlorinated alkanes,chlorinated alkenes,chlorinated aromatic hydrocarbons,etc.VCHs were widely applied in the use of solvents and industrial production as raw materials or intermediates,so the current research were more focused on industrial waste residue,wastewater or soil pollution and chemical process.While VCHs were very volatile,once they emitted into the environment,and then evaporate easily into the atmosphere.Reactive VCHs could react with other compounds or free radicals to produce more toxic pollutants,while long-lived VCHs can persist in the atmosphere,causing regional even globally pollution with atmospheric transport.However,most studies on VOCs focused on ozone precursors such as alkanes and alkenes as well as benzene while less reported VCHs in the atmosphere.The laetest research reported that the main emission source regions that slowed down the recovery of ozone layer were located in Shdong Province of China.In order to learn about VCHs concentration levels,characteration and transport,we conducted the sampling campaign in northern China.High altitude(Mount Tai)and urban sites(Tai’an and Jinan)were selected as the research area.GC/MS was used to quantify VCHs species in this paper and concentrations were determined in the atmosphere of selected sites.The spatial and temporal distributions of VCHs were analyzed as well as the influencing factors were studied.Influences of regional transport were analyzed using backward trajectories and the major potential emission source regions were simulated with potential emission source function(PSCF).PMF(positive matrix factor)was applied to calculate the emission sources to find out the potential emission source regions combined with PSCF results.The major source regions needed to strengthen the control of emission sources.Due to the toxicity of VCHs,the health risk assessment was used to evaluate the carcinogenic risk and non-carcinogenic risk,and to analyze the impact of VCHs on the human health of exposed population,and identified the major pollutants that threaten the exposed human health.Thirty-two kinds of high toxic VCHs were selected as target compounds,including CFCs,CBs and CAs in this study.The TVCHs concentration was 3.6 ppbv in the atmosphere of Mount Tai while 5.4 ppbv in Tai’an and 8.0 ppbv in Jinan.The concentrations of CFCs、CAs and CBs were 0.9,2.4 and 0.2 ppbv,respectively at Mount Tai while 1.0,3.9 and 0.2 ppbv in Tai’an,and 1.1,5.1 and 0.2 ppbv in Jinan.The average concentrations of CFC-11,CFC-12,CFC-113 and CFC-114 were 257,577,80 and 18 pptv in the atmosphere of Mount Tai,respectively.The concentration of CFC-11 was similar with the data ontained in 2006 with 260 pptv while CFC-113 concentration was slightly higher than that of 70 pptv in 2006.CFCs concentrations were all higher in the atmosphere of Mount Tai than those in the global alpine atmospheric background sites(230,510,72 and 16 pptv),respectively.CAs included as more as 26 kinds of compounds,sunch as chloromethane(CM),dichloromethane(DCM),chloroform(CF),carbon tetrachloride(TeCM).The concentration of chloromethane(CM,1109 pptv),dichloromethane(DCM,374pptv),1,2-dichloroethane(1,2-DCA 220 pptv),chloroform(CF,147 pptv),1,2-dichloropropane(1,2-DCP,148 pptv),carbon tetrachloride(TeCM,1 10 pptv)were higher among these compounds.The concentrations of toxic compounds such as trichloroethylene(TCE),tetrachloroethylene(TeCE)and hexachlorobutadiene(HCBD)were lower.The mean concentrations of benzyl chloride(BC),chlorobenzene(CB),1,4-dichlorobenzene(1,4-DCB),1,2-dichlorobenzene(1,2-DCB)and 1,2,4-trichlorobenzene(1,2,4-TCB)were 25,49,33 and 30 pptv,respectively,which were about 3 times lower than those in the atmosphere of Mount Tai in 2006.The concentrations of CFCs,CAs and CBs in the atmosphere of Tai’an were all higher than at Mount Tai.The average concentrations of CFC-11,CFC-12,CFC-113 and CFC-114 were 279,593,92 and 26 pptv,respectively.CM(1526 pptv),DCM(507 pptv),1,2-DCA(530 pptv),CF(408 pptv),1,2-DCP(302 pptv),TeCM(131 pptv)and chloroethylene(CE,244 pptv)were in higher level among CAs.The concentration of CE in the atmosphere of Tai’an was higher than in Mount Tai.The aveerage concentrations of CB,1,3-DCB,1,2-DCB,1,4-DCB and 1,2,4-TCB in CBs compounds were 32,15,77,48 and 32 pptv,respectively.However,benzyl chloride(BC)concentrations were detected below MDL(method detection limit).Average concentrations of CFC-11,CFC-12,CFC-113 and CFC-114 in Jinan were 341,648,79 and 23 pptv,respectively,which were all higher than those at Mount Tai and in Tai’an.The CAs compounds with higher concentration in Jinan were the same as Tai’an,including CM(1256 pptv),DCM(2880 pptv),1,2-DCA(573 pptv),CF(733 pptv),1.2-DCP(581 pptv)and TeCM(230 pptv),while the same as Mount Tai for the compounds in low levels.The average concentrations of CB,1,3-DCB,1,4-DCB,1,2-DCB and 1,2,4-TCB in Jinan were 33,19,63,25 and 35 pptv,respectively.The concentration of VCHs in Tai’an and Jinan(the ground stations)were higher than that in Mount Tai and were also at a higher level compared to other ground stations.According to the analysis of VCH concentrations and the mixed layer height,temperature,wind speed as well as common air pollutants(PM2.5,PM10,SO2,NO2 and O3),the concentrations of VCHs mainly related to regional transport at high altitude,while the temperature,humidity,radiation and other meteorological conditions had no significant influences.However,the concentrations of VCHs in Jinan mainly related to temperature,wind direction and distribution of surrounding emission sources.Due to the volatilization of VCHs especially at higher temperature,it is easy to evaporate into the atmosphere from solvent or surface coating.The concentrations of VCHs would decrease when the wind speed was high,and increase when the wind was from the direction of emission sources.The concentration distribution of CAs was positively correlated with the concentration of common air pollutants which suggested that the anthropogenic sources.Probabilistic Matrix Factorization(PMF)model suggested that atmospheric VCHs mainly originated from the solvent service volatilization,which contributed 46.8%of the total emissions,followed by chlor-alkali chemical industry and the emissions in the process of producing chlorinated reagent(43.6%),weaving and dry cleaner production and emissions(2.0%),as well as pharmaceutical and chemical solvent using(7.6%),respectively.By using HYSPLIT backward airflow trajectory analysis,atmospheric VCHs at Mount Tai were mainly affected by airflows from northwest,though the concentrations were generally high under the influence of airflows from the south and the north.PSCF analysis based on the results from HYSPLIT suggested that the major regions contributed to VCHs at Mt.Tai were located in the Middle East region of China(e.g.,provinces of Henan,Anhui,Jiangsu(Lianyungang))and the Economic Zone around the Bohai Sea.In addition,the northwest Inner Mongolia region was also the emission source of CFCs and CAs.During the sampling period,Jinan was mainly affected by transport from northwest and north.Similar to Mount Tai,the concentrations of CFCs and CAs were high under the influence of airflows from the south and the north.Further analysis by PSCF showed that the sources affecting the distribution of VCHs in Jinan mainly distributed in the central and eastern region as well as the region around Jinan,including the industrial cities of Zibo,Rizhao and Weifang,and the Economic Zone around the Bohai Sea.The common potential source areas of VCHs at Mount Tai and Jinan were Weifang,Zibo,Economic Zone around the Bohai Sea of Shandong and the central and eastern China,in which the emission amounts of VCHs were large due to the intensive manufacturing industry,chlor-alkali industry and chemical industry.Aaccording to the US EPA-recommended health risk assessment method,benzene is toxic which is calculated for comparisons.The results showed that the high-concentration and high-toxicity VCHs had greater carcinogenic risk and non-carcinogenic risk tan benzene.The non-carcinogenic risk of VCHs in the atmosphere of Tai’an and Jinan was within the safe range,and the non-carcinogenic risk of trichloroethylene and tetrachloroethylene was higher among toxic compounds.The lifetime carcinogenic risk of atmospheric VCHs in Tai’an and Jinan were greater than the acceptable safety thresholds for adults,indicating an impact on the health of exposed populations and carcinogenic risk.The main compound of the carcinogenic risk of Jinan atmospheric VCHs was chloroform,indicating that the common potential sources of trichloroethylene,carbon tetrachloride and chloroform were located in the border area of Shandong,Anhui and Henan.Within Shandong Province,industrial cities such as Weifang and Zibo were also important emission sources.Therefore,the control of the emission of VCHs in these source areas needs to be paid attention.In summary,the concentration levels of atmospheric VCHs in the areas of this study were generally higher.The concentration level of CFCs was significantly higher than that of other high-altitude and ground stations at domestic and overseas and the concentration of CAs in the atmosphere of Mount Tai was higher than that of ten years ago,but the concentration of CBs was significantly lower.The main potential impact area of regional transport on alpine atmospheric VCHs was the central and eastern part of China.The concentration of CFCs and CAs in Tai’an and Jinan sites was obviously on the high side,while that of CBs was on the low side.The concentration distribution was mainly affected by temperature,wind speed and air pollution situation.The major potential emission sources of Jinan atmospheric VCHs were Zibo,Weifang and Economic Zone around the Bohai Sea.The carcinogenic risk in both Tai’an and Jinan exceeded the safe value and it was potentially harmful to the exposed population.Chloroform,trichloroethylene and tetrachloroethylene were the most dangerous compounds.Given that,it is vital to control the emission sources of VCHs in central China and Economic Zone of the Bohai Sea to reduce the emission of VCHs in the atmosphere,and lower the potential hazards of exposed people. |
PDF Full Text Request