Contributions of different anthropogenic volatile organic compound sources to ozone formation at a receptor site in the Pearl River Delta region and its policy implications

Abstract

Abstract. Volatile organic compounds (VOCs) are key precursors of\nphotochemical smog. Quantitatively evaluating the contributions of VOC\nsources to ozone ( O3 ) formation could provide valuable information for\nemissions control and photochemical pollution abatement. This study analyzed\ncontinuous measurements of VOCs during the photochemical season in 2014 at a\nreceptor site (Heshan site, HS) in the Pearl River Delta (PRD) region, where\nphotochemical pollution has been a long-standing issue. The averaged mixing\nratio of measured VOCs was 34±3 \u2009ppbv, with the largest contribution\nfrom alkanes ( 17±2 \u2009ppbv, 49\u2009%), followed by aromatics, alkenes\nand acetylene. The positive matrix factorization (PMF) model was applied to\nresolve the anthropogenic sources of VOCs, coupled with a\nphotochemical-age-based parameterization that better considers the\nphotochemical processing effects. Four anthropogenic emission sources were\nidentified and quantified, with gasoline vehicular emission as the most\nsignificant contributor to the observed VOCs, followed by diesel vehicular\nemissions, biomass burning and solvent usage. The O3 photochemical\nformation regime at the HS was identified as VOC-limited by a photochemical\nbox model with the master chemical mechanism (PBM-MCM). The PBM-MCM model\nresults also suggested that vehicular emission was the most important source\nto the O3 formation, followed by biomass burning and solvent usage.\nSensitivity analysis indicated that combined VOC and NOx emission\ncontrols would effectively reduce incremental O3 formation when the\nratios of VOC-to- NOx emission reductions were >\u20093.8 for\ndiesel vehicular emission, >\u20094.6 for solvent usage, >\u20094.6 for biomass burning and 3.3 for gasoline vehicular emission. Based on\nthe above results, a brief review of the policies regarding the control of\nvehicular emissions and biomass burning in the PRD region from a regional\nperspective were also provided in this study. It reveals that different\npolicies have been, and continue to be, implemented and formulated and could help\nto alleviate the photochemical pollution in the PRD region. Nevertheless,\nevaluation of the cost-benefit of each policy is still needed to improve air\nquality.