Comment on acp-2021-1016

Ambient volatile organic compounds (VOCs) were measured continuously to investigate their characteristics, sources, atmospheric oxidation capacity (AOC) and chemical reactivity from January 2018 to December 2020 at an urban site in Zhengzhou, China. In this study, the total concentration of observed VOCs was 38.2 ± 15.6 ppbv during the sampling period, with the characteristics that alkanes were the major VOC species, accounting for 60 % of total VOCs. During the sampling period, the inter-annual variation of VOCs gradually reduced from 45.0 ± 25.2 ppbv in 2018 to 36.7 ± 22.0 ppbv in 2019, and to 30.5 ± 15.4 ppbv in 2020. Ethane, ethene, and propane were the top three abundant species during the three-year observation period. The results showed that total AOC, dominated by OH radical reactions, was 7.4 × 107 molecules cm−3 s−1. The total OH reactivity was 45.3 s−1, and mainly contributed by NOx. The AOC and •OH reactivity exhibited well-defined seasonal and inter-annual patterns. Therefore, the control strategy should focus on key species among inter-annual and seasonal variations. Meanwhile, diagnostic ratios of VOC species indicated VOCs in Zhengzhou were greatly affected by vehicle emissions and liquefied petroleum gas/natural gas (LPG/NG). Positive matrix factorization analysis showed six sources were identified, consisting of industrial sources, solvent use, vehicle exhaust, LPG/NG, coal+biomass burning and biogenic sources. Vehicle emissions, solvent use and LPG/NG made the largest contributions to VOC emission in all three years. The proportion of the contribution of vehicle emissions and LPG/NG has increased with each passing year. However, the proportion of industrial and solvent sources presented a decreasing trend, which is speculated that the policy control effect is remarkable. The effect of VOCs on ozone formation suggests that vehicle emission and solvent utilization were still key sources. Therefore, it is necessary to formulate effective strategies for reducing ground-level O3, and those sources mentioned above should be strictly controlled by the regulatory authorities.