Emission inventory of semi-volatile and intermediate volatility organic compounds and theireffectson SOA over the Pearl River Delta region

Semi-volatile and intermediate volatility organic compounds (S/IVOCs) are considered as critical precursors of secondary organic aerosol (SOA), which is an important component of fine particulate matter (PM2.5). However, the knowledge on the contributions of S/IVOCs to SOA is still poorly understood in the Pearl River Delta (PRD) region, southern China. Therefore, in this study, an emission inventory of S/IVOCs in the Pearl River Delta (PRD) region was developed for the first time for the year 2010. The S/IVOCs emission was calculated based on a parameterization method involving the emissions factors of POA (primary organic aerosol), emission ratios of S/IVOCs to POA, and domestic activity data. The total emission of S/IVOCs was estimated to be 323.4 Gg, with major emissions from central cities in PRD, i.e., Guangzhou, Foshan, and Shenzhen. On-road mobile sources and industries were the two major contributors of S/IVOC emissions, with contributions of ~ 42 % and ~ 35 %, respectively. Furthermore, uncertainties of the emission inventory were evaluated through Monte Carlo simulation. The uncertainties ranged from −79 % to 229 %, which could be mainly attributed to mass fractions of OC (organic compound) to PM2.5 from on-road mobile emissions and emission ratios of IVOCs/POA. The developed S/IVOC emission inventory was further incorporated into the Weather Research and Forecasting with Chemistry (WRF-Chem) model with a volatility basis-set (VBS) approach to improve the performance of SOA simulation and to evaluate the influence of S/IVOCs on SOA formation at a receptor site (Wan Qing Sha (WQS) site) of PRD. The following results could be obtained: (1) The model could resolve about 34 % on average of observed SOA concentrations at WQS after considering the emissions of S/IVOCs, and 18 %–77 % with the uncertainties of the S/IVOC emission inventory considered. (2) The simulated SOA over the PRD region was increased by 161 % with the input of S/IVOC emissions, and it could be decreased to 126 % after the reaction coefficient of S/IVOCs with OH radical was improved. (3) Among all anthropogenic sources of S/IVOCs, industrial emission was the most significant contributor of S/IVOCs for SOA formation, followed by on-road mobile, dust, biomass burning, residential, and off-road mobile emissions. Overall, this study firstly quantified emissions of S/IVOCs and evaluated their roles in SOA formation over PRD, which contribute towards significantly improving SOA simulation and better understanding of SOA formation mechanisms in PRD and other regions in China.