Pollution Characteristics,environmental Effect And Health Risk Assessment Of Ambient VOCs In Zibo City

Volatile organic compounds（VOCs）,as the common precursor for ozone（O₃）and fine particles(PM_2.5),play an essential part on photochemical regime and have adverse influence on human health.Zibo City had been confronting serious atmospheric pollution,so it had implemented Clean Air Action to alleviate such challenges.To investigate the characteristics of ambient VOCs and their possible impact on the environment and human health in the urban area of Zibo,a long-term observation campaign with high-resolution gas chromatography mass spectrometer（GC-MS）was conducted from December 2020 to October 2021.This study analyzed the concentration level,changed characteristic and sources of VOCs,and their contribution on the formation between O₃ and PM_2.5.Finally,a health risk assessment method（US EPA）was applied to quantitatively evaluate the non-carcinogenic and carcinogenic risks of toxic VOC species with human health assessment.The results of this study were as follows:（1）The averaged concentration of total VOCs（TVOC）in the urban area of Zibo was 63.28±42.33 ppbv throughout the whole campaign.Additionally,the sequence of the contribution for VOC categories mainly followed as alkanes>oxygenated volatile organic compounds（OVOC）>halogenated>aromatic>alkenes>acetylene>isoprene.The sequence of TVOC concentration for four seasons was winter>spring>summer>autumn,and alkanes with its dominant species contributed the most in each season.The concentration of TVOC showed a trend for diurnal average of high at the nocturnal but low during the daytime.Nine main pollution sources for each season derived by the positive matrix factorization（PMF）were traffic emissions,solvent source,combustion source,regional background,industrial emission,plant emission source+regional background,secondary generation+regional background,plant emission source and plant emission source+secondary generation.Specifically,traffic source,solvent source and industrial emission contributed most in each season.（2）During the whole campaign,the averaged values of ozone formation potential（OFP）,·OH loss rate(L_·OH),and secondary organic aerosol formation potential（SOA_p）of VOCs were 192.75 ppbv,13.86 s^-1 and 1.89μg/m³,respectively.Additionally,the sequence of three indicators was winter>spring>summer>autumn.Specifically,Alkenes and OVOC had higher contributions to OFP and L_·OH,and aromatic had the highest contribution rate to SOA_p.（3）Integrating the calculation results derived by the VOCs/NO_x ratio method,Smog Production Model（SPM）and Relative Incremental Reaction Activity（RIR）,the photochemical regime covering summertime（from May to September）was mainly identified as VOCs-limited.On the other hand,all ozone precursors contributed to ozone formation during polluted period,whereas RIR（NO_x）was negative during clean period.Note that AVOC contributed the most to the O₃formation among multiple VOCs groups,and the dominated subgroups of AVOC were mainly C2～C5 alkenes and C7～C9aromatic hydrocarbons.（4）During the whole campaign,toxic VOCs species showed non-carcinogenic risk and high probability of carcinogenic risk to human health.Halogenated hydrocarbons were the leading VOCs category with the highest contributions to non-carcinogenic and carcinogenic risks,respectively.No single source based on PMF in each season did not show non-carcinogenic risk,while most of them had carcinogenic risk.The sum of the non-carcinogenic risks of each pollution source was higher than the safety threshold only in autumn,whereas the sum of the carcinogenic risks reached the high probability cancer risk in each season.Non-carcinogenic and carcinogenic risks caused by solvent sources,industrial emission,traffic emission and combustion sources were at a high level.