Numerical Simulation Of The Chemical Components Of Fine Particles And Their Response To Precursor Emissions

China is faced with severe fine particle(PM 2.5) pollution. PM2.5 consists of complex chemical components. Effective control strategies should be developed considering different physicochemical characteristics and formation mechanisms of different chemical components. This study aims to improve the numerical simulation of the chemical components of PM2.5, especially organic aerosol(OA). Based on the improved simulation results, this study assesses the real-time response of PM2.5 and its chemical components to the emissions of air pollutants in city-clusters, thereby contributing to the decision-making of PM2.5 pollution control.In this study, we simulated a series of OA multi-generation oxidation experiments using the state-of-the-art Two-Dimensional Volatility Basis Set(2D-VBS) box model, and based on the simulation results, proposed the parameterization of 2D-VBS for the application in three-dimensional air quality models. Then, we developed the CMAQ/2D-VBS three-dimensional air quality modeling system, and evaluated its simulation results against field measurements. In addition, we developed an Extended Response Surface Modeling(ERSM) technique, and based on this technique, assessed the nonlinear response of PM2.5 and its chemical components to the emissions of multiple pollutants from multiple regions and sectors ov er the Yangtze River Delta region. Finally, we identified the sources of PM2.5 and its major chemical components, and conducted scenario analysis for the control of PM 2.5 pollution with the ERSM technique.The simulation results of the chamber experiments indicates that the first-generation oxidation of traditional secondary organic aerosol(SOA) precursors should be treated explicitly, and three parallel layers of 2D-VBS with different configurations should be applied to simulate the aging of anthropogenic SOA, the aging of biogenic SOA, and the multi-generation oxidation of primary organic aerosol(POA)/Intermediate Volatility Organic Compounds(IVOC).Based on the configuration above, the CMAQ/2D-VBS air quality modeling system significantly improved the simulation results of OA and SOA concentrations, and the simulated O:C, which reflects the oxidation state of OA, agrees well with the observations in most sites. The simulation results of CMAQ/2D-VBS indicate that the multi-generation oxidation of OA enhances the OA and SOA concentrations by 42% and 10.6 times, respectively. Anthropogenic non-methane volatile organic compounds(NMVOC), biogenic NMVOC, POA, and IVOC contribute 8.7%, 5.4%, 40.2%, and 45.7%, respectively, to the average OA concentration s in eastern China.The ERSM technique developed in this study has a high accuracy, and can be applied for the nonlinear source apportionment of PM2.5. In the Yangtze River Delta region, the PM2.5 concentration is most sensitive to the emissions of primary inorganic PM2.5. Among the precursors, in January, the PM2.5 concentration is most sensitive to ammonia(NH3) emissions; in August, the PM2.5 concentration is sensitive to all the precursors considered. The sensitivities of PM2.5 to NH3 and nitrogen oxides(NOX) increase significantly with the increase of reduction ratios. The ERSM technique is applicable for the rapid decision-making of PM2.5 pollution control in major city-clusters.