Pollution Characteristics And Health Risk Assessment Of Atmospheric Volatile Organic Compounds In Lanzhou

In recent years,O₃?Ozone?have become the primary pollutant in parts of China,leading to air pollution pattern shift from coal-smoke to mix mode.As a precursor of O₃ and SOA?Secondary Organic Aerosol?,VOCs?Volatile Organic Compounds?have received extensive attention of the government,as effectively control and reduction can greatly reduce the pollution of O₃ and SOA,and can improve air quality and reduce human health risks.In order to study VOCs pollution characteristics and explore the photochemical activity of VOCs and its active constituents,and potential formation to SOA,one-year monitoring was conducted by using an on-line monitoring instrument of VOCs in Lanzhou in 2018.By analyzing the sources of VOCs and evaluating the risk to human meanwhile,the following results were obtained:?1?Atmospheric VOCs and its components existed contamination variously during the study periodThe concentration of TVOCs ranged from 43.88 ppbv to 51.58 ppbv,and OVOCs had the highest concentration with 41.80⁴6.14 ppbv,then was the aromatic hydrocarbons and isoprene concentration was the lowest.The pollution levels of VOCs in heavily pollution weather and dust weather were much higher than that in other weather conditions,with the concentrations of 119.06 ppbv and 100.72 ppbv,respectively.Acetonitriles and isoprene were higher in dust weather conditions,while OVOCs and aromatic hydrocarbons were higher in heavily pollution weather.?2?The variations of VOCs and its components were differentBoth TVOCs and OVOCs showed a fluctuating pattern as their concentrations were higher in January to February,April to May and October to November.Except for May,the annual variation of acetonitrile was not significant.Isoprene had a relative high concentration in March to May.Aromatic hydrocarbons had the highest concentration in February.TVOCs and its components showed obvious seasonal variations,in which TVOCs in summer was much lower than the other three seasons,acetonitrile in autumn and winter were slightly higher than that in spring,isoprene in spring was much higher than that in other seasons,OVOCs in summer was slightly lower than that in other seasons,aromatic hydrocarbons was higher in winter,followed by autumn.The TVOCs and its components were basically higher in daytime than that in nighttime,and their diurnal variations showed a bimodal pattern,but the peaks appeared at different time.?3?Lanzhou atmospheric environment had a relatively strong photochemical activity and SOA formation potentialThe consumption rate of OH radical was 8.69 s^-11 and potential formation to O₃ was162.29?g/m³,and acetaldehyde,toluene,m-p-xylene,isoprene and m-p-ethyltoluene were the active components in the atmosphere.The potential formation to SOA was43.27?g/m³,in which toluene,m-p-xylene,o-xylene,m-p-ethyltoluene,ethylbenzene and 1,3,5-trimethylbenzene were the key VOCs to SOA formation.The potential of VOCs to the formation of SOA had obvious time variations.The annual variation showed that SOA formation in February was much higher than other months,SOA formation in autumn and winter were much higher than that in spring and summer,and heavily pollution and dust weather had higher SOA formation than that in other weather conditions.?4?The sources of VOCs in the atmospheric environment of Lanzhou were basically the same in different periods are,but the main contribution sources were not the same.The T/B value ranged from 0.7 to 2 in March to November,spring,summer,and autumn,and different weather conditions,indicating that VOCs were significantly affected by vehicle exhaust emissions,while the T/B in January to February,December,and winter is less than 0.7,indicating that VOCs were mainly affected by coal burning and biomass burning in these periods.Based on PMF analysis,VOCs mainly came from combustion+solvent-paint using?61.58%?,followed by vehicle exhaust emission?29.57%?,and natural emission only accounted for 8.85%.In the different weather conditions,it could be seen that the contribution of combustion+solvent-paint using to VOCs was as high as 82.96%in the heating period,and just accounted for 49.43%in the dust weather.The contribution of vehicle exhaust to VOCs was 47.14%in dust weather and 11.17%in heating period.?5?The atmospheric VOCs in Lanzhou had health risk to human partlyThere were no potential non-carcinogenic risks of VOCs to different groups of people,and the carcinogenic risks were in an acceptable level.While VOCs had potential non-carcinogenic risks for adults in heavily pollution weather and dust weather,and for children in heavily pollution weather,the carcinogenic risks of VOCs to different groups of people in different periods fell in the acceptable level.Above all,the atmospheric VOCs and its components existed contamination variously,and had obvious time variations,VOCs had strong photochemical activity,its source and potential formation to SOA were equally in different weather conditions,and it existed potential non-carcinogenic risks to human under the conditions of heavily pollution and dust weather.