Distribution Characteristics And Health Risk Assessment Of VOCs In Shihezi Atmospheric Environment

Recently,there is growing concern about ozone（O₃）and fine particle pollution.Shihezi,a core city of Wu-Shi-Chang urban agglomeration,is always with a high fine particulate matter level,the mixing ratio of ozone also increasing with years.However,volatile organic compounds（VOCs）,the important precursor of O₃ and secondary organic aerosols（SOA）,have not been reported in details in Shihezi.During this study,Summa canisters were applied to sample and gas chromatograph-mass spectrometer was used to analyze VOCs from 2018 to 2019 in Shihezi.The pollution and variation characteristics of VOCs in Shihezi were analyzed.In addition,PMF model was also applied to analyze emission sources.The ozone formation potential（OFP）and secondary organic aerosol formation potential（SOAFP）of VOCs were estimated by Maximum Incremental Reactivity（MIR）and Fractional Aerosol Coefficient（FAC）.Finally,Monte-Carlo simulation as well as health risk assessment methods recommended by USEPA were used to analyze the health risks that VOCs may cause to human.The important results were listed as follows:（1）The mixing ratio of TVOCs in the atmospheric environment of Shihezi area was 51.09 ppbv,of which the mixing ratio of alkane showed the largest contribution,accounting for 51.22%of TVOCs, followed by ethyne,accounting for 39.81%,the alkene and aromatic hydrocarbon percentages were low,4.77%and 4.20%,respectively.The level of ethyne was significantly higher than other cities in China.VOCs in Shihezi area were under the combination impact of coal combustion and traffic related emission sources,and both local emissions and short scale transportation showed big contribution to Shihezi ambient VOCs.（2）PMF model was applied to quantitatively analyze the pollution sources of VOCs in the atmosphere of Shihezi,a total of 5 pollution factors were distinguished,of which coal combustion contributed the most to VOCs concentration,which was 41.0%,followed by transportation Sources（31.6%）,fuelvolatilization and solvent use sources（11.4%）,industrial sources（8.2%）,and LPG/NG useage （7.9%）.（3）The L^OH and OFP of VOCs in Shihezi were 167.40 S^-1 and 59.77 ppbv,respectively.Among the L^OH and OFP,the proportion of alkanes was the largest,which showed 41.97%and 37.21%,respectively.The percentage of ethyne in TVOCs was large,but they do not contribute much to L^OH and OFP,10.08%and 18.44%,respectively.The proportion of alkene in TVOCs is not high.The contribution of L^OH and OFP reached 32.75%and 33.34%,which is related to its more active and prone to photochemical reactions in urban ambient;The contributions of aromatic to L^OHH and OFP were 15.2% and 11.01%.（4）The SOAFP in Shihezi area was 0.52μg/m³,of which alkane was 0.13μg/m³,accounting for 24.71%,and aromatic hydrocarbon was 0.39μg/m³,accounting for 75.19%.Among them,n-decane accounted for 22.22%.As for aromatic hydrocarbons,toluene（31.54%）contributed the most to SOAFP in Shihezi,but the contributions of p-xylene,benzene,ethylbenzene,and o-xylene cannot be ignored.（5）The average HQ of a single species of VOCs in the atmospheric environment of Shihezi area was between 0.00-0.61,and the average value of HI value was 1.48,indicating that VOCs in Shihezi area may have potential non-carcinogenic risks.The average Risk of benzene in Shihezi’s atmospheric environment was 143.25,indicating that benzene may have potential carcinogenic risks.In general,based on the results of VOCs study in Shihezi,alkanes,alkenes,alkynes and aromatic hydrocarbons were detected.VOCs pollution was mainly related to coal combustion and traffic emission sources.VOCs health risk assessment results indicated that VOCs may contribute to potential non-carcinogenic and carcinogenic risks.This study not only laid the foundation for the study of the pollution characteristics of VOCs,but also has important significance for the health risk management and pollution prevention of VOCs in Shihezi.