RESUMO
A typical particulate matter pollution process occurred from October 9 to 17,2018,in Langfang,and 99 types of volatile organic compounds (VOCs) were monitored by using ZF-KU-1007. The characteristics of VOCs,formation potential of secondary organic aerosol (SOA),and source of VOCs were systematically analyzed. The results showed that the maximum concentration of PM2.5 was 198 µg·m-3 during the pollution process and was 2.64 times the National Ambient Air Quality Standard (GB 3095-2012). The average concentration of VOCs was 56.8×10-9,127.8×10-9,and 72.5×10-9 in the early,middle,and late stages of the pollution process,respectively,and the concentration of VOCs increased significantly in the middle stage. The formation potential of SOA was significantly positively correlated with PM2.5,and the contribution of aromatic hydrocarbon for SOA was larger and significantly correlated with the concentration of PM2.5. In the middle pollution stage,SOA increased,and the contribution ratio of aromatic hydrocarbon increased significantly. Conversely,the contribution of alkanes and olefin decreased significantly,which showed that aromatic hydrocarbons,namely benzene series,were the dominant species of SOA generation and had a great influence on the pollution process. Benzene,toluene,m-/p-xylene,o-xylene,and ethylbenzene and nonane,n-undecane,and methylcyclohexane were the priority control species in this pollution process. Solvent use source and motor vehicle emission source (gasoline and diesel vehicles) were the main sources affecting the concentration of VOCs during the autumn pollution process of Langfang,among which the contribution of gasoline vehicle emissions increased significantly in the middle pollution contribution and was the key control source.
RESUMO
A total of 99 volatile organic compound(VOC) species were detected the Langfang development zones based on continuous monitoring using a ZF-PKU-1007 between August 25 and September 30, 2018. The concentrations, reactivity, and sources of VOCs were studied under different O3 concentrations using compositional analysis. The results showed that the average VOCs concentration during the research period was(75.17±38.67)×10-9, and was(112.33±30.96)×10-9, (66.25±34.84)×10-9 on pollution days and cleaning days, respectively(VOCs concentrations were 69.6% higher on pollution days). The contribution of VOCs species to the ozone formation potential(OFP) were ranked in the order aldehydes > aromatics > alkenes > alkanes. In the case of L·OH, the main contributions were from aromatics(30.0%) and alkenes(25.8%) on pollution days, while the contribution from aromatic alkenes(29.8%) was a slightly higher than aromatics(28.0%) on cleaning days. By applying the positive matrix factorization(PMF) model, five major VOCs sources were extracted, namely vehicle emissions(34.4%), solvent usage and evaporation(31.7%), the petrochemical industry(15.7%), combustion(11.1%), and plant emissions(7.9%). The contributions of solvent usage and evaporation and plant emission sources on pollution days were 13.1% and 1.2% higher than on cleaning days, respectively, which was likely due to relatively higher temperatures on these days. Therefore, vehicle emissions and solvent usage and evaporation should be priorities in VOCs control strategies for the Langfang development zones between August to September.