Exploration of O3-precursor relationship and observation-oriented O3 control strategies in a non-provincial capital city, southwestern China

To investigate photochemical ozone (O 3 ) formation and provide localized control strategies, an intensive sampling of O 3 and its precursors ( i.e. volatile organic compounds (VOCs) and nitrogen oxides (NO x = NO + NO 2 )) were conducted at an urban site in Leshan, Sichuan province during 4–13 August 2019. The mixing ratios of O 3 , total VOCs (TVOCs) and NO x were 40.0 ± 5.3, 22.5 ± 2.6 and 14.6 ± 3.8 ppbv, respectively (±95% confidence intervals). O 3 and its precursors existed a well negative correlation, indicating intensive local O 3 formation. To further explore the O 3 -precursors relationship and observation-oriented O 3 control strategies, a photochemical box model coupled with master chemical mechanism (PBM-MCM) was adapted. The relative incremental reactivity (RIR) calculated by model results showed that Leshan was in the VOCs-limited and O 3 production was most sensitive to alkenes. Moreover, O 3 isopleth diagram was drawn using the PBM-MCM simulation results and seven reduction scenarios were evaluated in Leshan. The reduction ratio of VOCs/NO x on 3:1 was proposed to be the best solution, which can be achieved effective reduction on local O 3 formation. At last, since VOCs were the key precursors of O 3 in Leshan, VOC sources and their potential contributions to O 3 formation were investigated by using the positive matrix factorization (PMF) model. Seven sources were identified, and traffic related emissions (including vehicle exhaust and gasoline evaporation, 29.9%) and fixed combustion (27.7%) had the large contribution to ambient VOCs. Among anthropogenic sources, fixed combustion and solvent usage in painting were the large contributors to O 3 formation, accounting for 30.9% and 18.3%, respectively, which should have high priorities on source reduction. This study provides scientific advices for future O 3 pollution control strategies in Leshan, which can be extended to other cities. • Ozone formation in Leshan was in VOCs-limited regime and most sensitive to alkenes. • The optimal reduction ratio of VOCs/NO x was 3:1 to reduce local O 3 formation. • Fixed combustion and solvent usage in painting were the main anthropogenic sources to O 3 formation.