Pollution Characteristics And Health Risk Assessment Of Benzene Series In Three Typical Main Roads In Guilin City

In recent years,due to the development of tourism in Guilin,the per capita living standards and the number of motor vehicles in Guilin have been increasing as well.However,environmental pollution problems caused by exhaust emissions from motor vehicles have also followed.Among them,the BTEX(benzene,toluene,ethylbenzene,o-xylene,m-p-xylene)are deeply concerned because they can seriously affect human health and the high chemical activity.In this paper,the monitoring of ambient air in three typical traffic arteries of Kaifeng Road,Zhongshan South Road and Zhongshan Middle Road in Guilin were carried out with gas chromatography coupled with activated charcoal adsorption and carbon disulfide desorption.Pollution levels of BTEX,composition distribution characteristics and variation characteristics(seasonal changes and sampling period changes),hydroxyl consumption rate,ozone and secondary organic aerosol generation potential,and health risk assessment were analyzed.The conclusions were indicated below.The average concentrations of BTEX in the three main roads in Guilin under normal weather were 45.76?g/m~3,47.05?g/m~3,and 40.34?g/m~3 respectively.Through B/T analysis,the pollution of BTEX in Guilin mainly came from motor vehicle exhaust,but it was also affected by fossil fuels.The seasonal variation characteristic showed that the average concentrations of BTEX in summer,autumn and winter were 17.95?g/m~3,58.48?g/m~3,and 56.73?g/m~3respectively and the concentrations of BTEX were the highest in autumn and the lowest in summer.In general,the variation characteristics of BTEX in the three main roads in the sampling period were decreasing from 8:00 am to 14:00 pm in different seasons.The concentrations of total BTEX were the highest in each main road in summer and winter from 8:00am to 9:00am while the concentration of the total BTEX was the highest in the autumn from 9:00am to 10:00am.The results of chemical reactivity studies of BTEX showed that m-p-xylene was a key component in photochemical reactions,and it was also the most potential substance for ozone generation,while toluene was the most potential substance for secondary organic aerosol generation.The order of hydroxyl consumption rate was generally rendered as m-p-xylene>toluene>o-xylene>ethylbenzene>benzene;The trend of total ozone generation potential in each season was rendered as autumn>winter>summer;The total secondary organic aerosol generation potential of each season was rendered as winter>autumn>summer.The Hazard index(HI)of Kaifeng Road,Zhongshan South Road and Zhongshan Middle Road were 0.515,0.548,0.516 respectively and the Risk values were8.626E-4,9.392E-4,9.302E-4 respectively.Those values indicated the BTEX of the three main traffic lanes in Guilin City had no non-carcinogenic risk to the study areas.The carcinogenic risk of benzene exceeded 1.00E-6,it indicated that the benzene in the air of traffic trunks had a carcinogenic risk to the health of residents.