Characteristics and Source Apportionment of Ambient Summer Volatile Organic Compounds in Zhengzhou, China

The concentrations of volatile organic compounds (VOCs) in the atmospheric environment in the urban area of Zhengzhou were investigated by a GC5000 online gas chromatography in the summer of 2019 and 2020 from June to August, respectively, and the pollution characteristics, especially the source apportionment, were explored with the methods of ratio analysis (RA), positive matrix factorization (PMF) model, and conditional probability function (CPF) model. The results showed that the average VOCs concentrations in 2019 and 2020 summer were 65.7 μg·m -3 and 71.0 μg·m -3, respectively. In 2019, the proportion of alkanes was changed little, accounting for about 55%. The aromatic hydrocarbon showed an upward trend and olefin was decreased month by month. The top ten species were accounted for 65.5% of the total VOCs with the main species of isopentane, ethane, propane, toluene, n-butane, and m/p-xylene, etc. In 2020, the proportion of alkanes and olefins was increased, while the proportion of aromatic hydrocarbons was decreased month by month. The top ten species were accounted for 71.1% of the total VOCs with the main species of ethane, ethylene, propane, isopentane, n-butane, toluene and m/p-xylene, etc. The average ozone formation potential (OFP) concentration in summer 2019 was 224.9 μg·m -3. It was found that the contribution ratio of aromatic hydrocarbons to OFP was increased, while that of olefin was decreased month by month, and the main species contributing to OFP were m/p-xylene, isoprene, trans-2-butene, toluene, ethylene, etc. In 2020, The average OFP concentration in summer was 243.6 μg·m -3, the contribution of aromatic hydrocarbons to OFP was decreased, while the contribution of olefin was increased month by month, and the major species contributing to OFP were ethylene, m/ p-xylene, isoprene, toluene, and m-ethyltoluene, etc. The RA, PMF and CPF model analysis showed that the major contributions in 2019 were the solvent usage and the oil / gas volatilization sources, accounted for 36.7% and 25.1% of VOCs, and their contributions to the OFP were accounted for 39.9% and 23.3% respectively, mainly from the southwest region of Zhengzhou. In 2020, the solvent usage and oil / gas volatilization sources were accounted for 24.9% and 22.5%, and solvent usage and motor vehicle exhaust were the major contribution to the OFP, accounting for 33.6% and 22.9%, respectively, mainly from the north and south regions. Therefore, more attention should be paid to the use of solvent, vehicle exhaust emissions, oil and gas volatilization sources emissions in the future, especially for the pollution sources in the southwest, north and southeast areas. © 2022 Science Press. All rights reserved.