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Abstract:
Tropospheric ozone pollution is a critical air-quality concern in China. However, the most effective mitigation approach remains unclear, with prioritizing the reduction of volatile organic compounds or nitrogen oxides (NOX) currently still under debate. Here we analyse observational measurements of ozone in August, as well as its precursors, from urban Beijing between 2006 and 2020. We show that, despite a continuous increase in the primary atmospheric oxidant (hydroxyl radical, OH), ozone increased until 2014 and then decreased. This ozone trend can be explained by changes in OH turnover rate, primarily determined by the reactivity ratio between volatile organic compounds and NOX. Overall, reactive abatement of volatile organic compounds should be a near-future priority for ozone-pollution control in China, followed by further NOX controls.
