| Volatile organic compounds(VOCs),important precursors of secondary organic aerosols(SOA)and ozone(O3)in the surface layer,play a key role in the formation of complex air pollution and have profound effect on some environmental problems such as photochemical smog,acid rain,global warming et al.VOCs not only damage the ecological environment but also do harms to people's health,which have aroused growing concern and attention in recent years.A field sampling campaign collected by SU-MMA canister was conducted in Shandong Agricultural University,China from April 2017 to December 2017,and then 48 kinds of VOCs including 3 alkanes,1 alkene,29 halocarbons and 15 aromatics were analyzed by pre-concentration-GC/MS.The concentration characteristics,pollution level,chemical reactivity,source apportionment and health risk assessment were analyzed and discussed.The daily average concentration of 48 VOCs in Taian was 8.83±3.97 ppb,with the median of 7,72 ppb.The concentrations of VOCs were higher in the pollution days.Compared with other cities and background sites in the worldwide,the concentration of atmospheric aromatics in Taian was at the mid-low level.The contributions of alkanes,alkenes,halocarbons and aromatics to 48 VOCs in this research were 4.18%,6.19%,55.43%and 34.20%,respectively.The concentrations of four kinds of VOCs all showed the daily trend of higher in the morning and evening,lower at noon,which were concerned with human activities,the height variation of boundary layer and the intensity of photochemical reactions.The results of monthly variation of VOCs showed that there were obvious concentration fluctuations in summer and winter,which were related to human activities and the differences of climatic conditions.Potential regional sources of atmospheric VOCs in Taian were investigated by Hybrid Single Particle Lagrangian Integrated Trajectory(HYSPLIT)and potential source contribution fuction(PSCF)model.The results of HYSPLIT showed atmospheric VOCs during the field measurement were mainly influenced by six clusters including southeast of Taian(27%),southwest(23%),local sources(21%),north(16%)and two air masses outside China(13%).The results of PSCF were in accordance with HYSPLIT.Urban industrial and household emissions from these clusters were the major influencing factors of VOCs.Regional transmissions and local sources were the main sources of atmospheric VOCs from the findings of two methods combined.Positive matrix factorization(PMF)model were utilized to estimate emission sources of atmospheric VOCs,finding that PMF obtained the optimum solution with four emission factors.Four sources of PMF results were industrial activities and household emission(32.68%),vehicle exhaust(19.06%),industrial activities and fuel combustion(25.95%)and solvent evaporation(22.32%).The OH radical loss rate(LOH)and ozone formation potential(OFP)were used for evaluating the chemical reactivity of VOCs.The LOH of aromatics was the highest,accounting for 60.03%of all,and then followed by alkenes(35.57%)and alkanes(4.40%).1,3-Butadiene and naphthalene were the key reactive species of OH radical loss in this research.As for the ozone formation potential(OFP),1,3-butadiene and toluene had the greatest contributions to ozone formation.Aromatics had the major contribution followed by alkenes,halocarbons and alkanes in all four seasons.From the above two methods,aromatics and alkenes with higher chemical reactivity contributed most to the ozone formation.According to the list of hazadous air pollutants from U.S.EPA,we selected 34 VOCs for assessing the health risk to the population.The results showed that,VOCs selected had no significant risk of non-cancer health effect on exposed population.However,the lifetime cancer risks of 9 VOCs species such as naphthalene and benzene were beyond the accepted range of values of EPA,which showed that these VOCs posed potential carcinogenic risk to humans and need to be taken seriously. |
PDF Full Text Request