Measurement report: Aircraft observations of ozone, nitrogen oxides, and volatile organic compounds over Hebei Province, China

Benish, Sarah E.; He, Hao; Ren, Xinrong; Roberts, Sandra J.; Salawitch, Ross J.; Li, Zhanqing; Wang, Fei; Wang, Yuying; Zhang, Fang; Shao, Min; Lu, Sihua; Dickerson, Russell R.

To provide insight into the planetary boundary layer (PBL) production of ozone (inline-formulaO3) over the North China Plain, the Air chemistry Research in Asia (ARIAs) campaign conducted aircraft measurements of air pollutants over Hebei Province, China, between May and June 2016. We evaluate vertical profiles of trace gas species including inline-formulaO3, nitrogen oxides (inline-formulaNOx), carbon monoxide (CO), and volatile organic compounds (VOCs) and relate to rates of inline-formulaO3 production. This analysis shows measured inline-formulaO3 levels ranged from 45 to 146 inline-formulappbv, with the peak median concentration (inline-formula∼ 92 inline-formulappbv) occurring between 1000 and 1500 inline-formulam. The inline-formulaNOx concentrations exhibited strong spatial and altitudinal variations, with a maximum of 53 inline-formulappbv. Ratios of inline-formulaCO∕CO2 indicate the prevalence of low-efficiency combustion from biomass burning and residential coal burning but indicate some success of regional pollution controls compared to earlier studies in China. Concentrations of total measured VOCs reveal alkanes dominate the total measured volume mixing ratio of VOCs (68 %), and sources include vehicular emissions, fuel and solvent evaporation, and biomass burning. Alkanes and alkenes/alkynes are responsible for 74 % of the total VOC reactivity assessed by calculating the OH loss rates, while aromatics contribute the most to the total ozone formation potential (OFP) (43 %) with toluene, inline-formulam/inline-formulap-xylene, ethylene, propylene, and inline-formulai-pentane playing significant roles in the aloft production of inline-formulaO3 in this region. In the PBL below 500 inline-formulam, box model calculations constrained by measured precursors indicate the peak rate of mean inline-formulaO3 production was inline-formula∼ 7 inline-formulappbv h−1. Pollution frequently extended above the PBL into the lower free troposphere around 3000 inline-formulam, where inline-formulaNO2 mixing ratios (inline-formula∼ 400 inline-formulapptv) led to net production rates of inline-formulaO3 up to inline-formula∼ 3 inline-formulappbv h−1; this pollution can travel substantial distances downwind. The inline-formulaO3 sensitivity regime is determined to be inline-formulaNOx-limited throughout the PBL, whereas it is more VOC-limited at low altitudes near urban centers, demonstrating that control of both VOCs and inline-formulaNOx is needed to reduce aloft inline-formulaO3 pollution over Hebei.

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Benish, Sarah E. / He, Hao / Ren, Xinrong / et al: Measurement report: Aircraft observations of ozone, nitrogen oxides, and volatile organic compounds over Hebei Province, China. 2020. Copernicus Publications.

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