Ambient volatile organic compounds and their effect on ozone production in Wuhan, central China

Ambient volatile organic compounds (VOCs) were continuously measured from February 2013 to October 2014 at an urban site in Wuhan. The characteristics and sources of VOCs and their effect on ozone (O ₃ ) formation were studied for the first time. The total VOC levels in Wuhan were relatively low, and of all VOCs, ethane (5.2±0.2 ppbv) was the species with the highest levels. Six sources, i.e., vehicular exhausts, coal burning, liquefied petroleum gas (LPG) usage, the petrochemical industry, solvent usage in dry cleaning/degreasing, and solvent usage in coating/paints were identified, and their contributions to the total VOCs were 27.8±0.9%, 21.8±0.8%, 19.8±0.9%, 14.4±0.9%, 8.5±0.5%, and 7.7±0.4%, respectively. Model simulation of a photochemical box model incorporating the Master Chemical Mechanism (PBM-MCM) indicated that the contribution to O ₃ formation of the above sources was 23.4±1.3%, 22.2±1.2%, 23.1±1.7%, 11.8±0.9%, 5.2±0.4%, and 14.2±1.1%, respectively. LPG and solvent usage in coating/paints were the sources that showed higher contributions to O ₃ formation, compared to their contributions to VOCs. The relative incremental reactivity (RIR) analysis revealed that the O ₃ formation in Wuhan was generally VOC-limited, and ethene and toluene were the primary species contributing to O ₃ production, accounting for 34.3% and 31.5% of the total RIR-weighted concentration, respectively. In addition, the contribution of CO to the O ₃ formation was remarkable. The C ₄ alkanes and alkenes from the LPG usage also significantly contributed to the O ₃ formation. The results can assist local governments in formulating and implementing control strategies for photochemical pollution.