Pollution Characteristics And Health Risk Assessment Of BTEX In The Atmosphere Of Beijing Road Area In Urumqi In Autumn And Winter

In recent years,severe ozone pollution has often occurred in some areas of China,affecting hundreds of millions of people.Volatile organic compounds（VOCs）are one of the important precursors of ozone.The reduction of VOCs is the key to achieving ozone pollution control.Therefore,it is necessary to carry out research and implement prevention of VOCs.Benzene series（BTEX）is an important component of VOCs,It is an effective pollutant in VOCs.In this study,benzene series（BTEX）in the atmosphere of Urumqi Beijing Road Area in autumn and winter of 2020 were continuously observed by using EXPEC3500 portable gas chromatography-mass spectrometry（GC-MS）.Based on the analysis of the observed data,the composition characteristics and temporal variation of BTEX were obtained;The·OH reaction activity,ozone generation potential and secondary organic aerosol generation potential of BTEX were investigated by using·Oh consumption rate(L^OH),maximum incremental reaction activity（MIR）and aerosol generation coefficient（FAC）;The paper analyzed the source of BTEX by eigenvalue method,principal component analysis（PCA）,positive matrix factor analysis（PMF）and backward trajectory model（Traj Stat）;Finally,the paper assessed the potential health risk of BTEX in the atmosphere to the population in the Beijing Road Area of Urumqi.The mainly research findings are as follows:（1）The average concentrations of VOCs in the atmosphere of Beijing Road Area of Urumqi are as follows:aromatics>alkanes>halogenated hydrocarbons>oxygenated compounds,and their average concentrations are 90.54?μg/m³,85.60?μg/m3,67.37?μg/m³,61.24?μg/m³,respectively.The average concentrations of benzene,m-xylene,p-xylene,toluene,ethylbenzene and o-xylene were 16.791?μg/m³,12.767?μg/m³,9.080?μg/m³,?8.786?μg/m³,?6.470?μg/m³,respectively.The percentages of the concentration of each component of the benzene series to the total are 33.33%,26.67%,20.00%,13.33%,6.67%,respectively.（2）During the observation period,the benzene series and its components showed diurnal variation with bimodal characteristics.The concentration is higher in the morning and evening rush hours,and lower in the afternoon when the sunlight is the strongest.The monthly concentration change of BTEX was opposite to that of O₃,but the same as that of PM_2.5and NO₂.With the increase of AQI index,the concentration of BTEX increased gradually and reached the maximum value in the period of severe pollution.（3）The order of the components of BTEX according to the L^OHvalue was m-xylene,p-xylene,ethylbenzene,toluene,o-xylene and benzene.The contribution rate of m-xylene and p-xylene to OPP was the highest,accounting for 49.0%;the contribution rate of benzene to OPP was the lowest,accounting for3.67%.The contribution rates of BTEX components to secondary organic aerosol formation potential（SOAFP）were 23.69%,21.32%,16.02%,12.63%and 12.00%,respectively.（4）Both PCA and PMF models belong to receptor models,but there are still some differences.After several adjustments and operation,the two quantitative analysis models identify two pollution factors.Combined with the industry type around the sampling point and the model analysis results,the main factors of the observation point are determined.The sources of pollution are motor vehicle exhaust,?fossil fuel burning（mainly natural gas）,catering ndustry and waste incineration.E/X is 2.18,indicating that most of the pollution in this region is localized emission source.?The Traj Stat model shows that Urumqi Beijing Road Area mainly transports short distance air mass.The results show that the main pollution source of BTEX in Urumqi Beijing Road Area is coal combustion,and the local transportation is the main one.（5）The average value of HQ of the monomer components in the atmosphere of Urumqi Beijing Road Area is between 0.00-0.23,and the average value of HI is 0.31.There is a 95%possibility that HI will fall in the range[0.27,0.37],The results showed that the benzene series in Beijing Road area of Urumqi did not pose a non-carcinogenic risk during the observation period.Benzene is one of the most harmful species in the atmospheric environment.The average value of risk is 5.31E-05,and the median value is 4.97E-05.There is a 95%probability that the risk will fall in the range[3.48E-05,8.25E-05],This suggests that benzene may pose a potential carcinogenic risk to the population near the sampling site during the observation period.