| With the acceleration of global industrialization and urbanization, O3 and PM2.5 have become global extremely serious types of air pollution, and it is urgent to control regional and complex air pollution in China. Therefore, to understand the production process and analyze the main control factors of O3 and PM2.5, study on influence of haze heavily polluted areas on surrounding areas are important for policymakers to establish pollution control strategies.This paper chose Qingdao as the key study area. WRF-CMAQ model was used for simulation research of O3 and PM2.5 in Qingdao and eastern China during two episodes, from May 17 to June 7 (non-heating season) and from November 8 to December 1 (heating season) of 2013, exploring reasons for the simulation biases by combining with air quality observational data, studying simulated error factors, analyzing the time and space distribution of O3 and PM2.5. The Integrated Process Rate Analysis (IPR) method was applied to study contributions of different physical and chemical processes to the changes of O3 and PM2.5 concentrations. The indicators including O3/NOx and PH2O2/PHNO3 were used to analyze the main controlling factor of O3 concentration. In addition, scenario simulation schemes were used to probing the influence of haze pollution in North China on PM2.5 concentration in Qingdao.WRF-CMAQ simulations showed that R2 between simulated and observed O3 concentrations in Qingdao in non-heating season and heating season were 0.13 and 0.21, respectively, and average standard deviations were 71.1% and 95.9%, respectively. O3 concentrations were overestimated due to biases of NOx source emission. R2 between simulated and observed PM2.5 concentrations in non-heating season and heating season were 0.20 and 0.21, respectively, and average standard deviations were -21.8% and -14.3%, respectively. Simulation biases of airflow, PBL and precipitation by WRF model, and some important formation pathways of SOA may still miss in current air quality models were the reasons for differences in variation trends of simulated and observed PM2.5 concentrations.The O3 process analysis indicates that the contributions of different process on diurnal variation of surface O3 concentrations in Qingdao were consistent in different seasons. The main source of surface O3 was vertical transport, the main removal processes were horizontal transport, dry deposition and gas-phase chemical processes. But on different height, the contributions of different process on diurnal variation of O3 concentrations in Qingdao were inconsistent in different seasons. O3 close to the ground by vertical transmission was generated from gas-phase chemical processes above the altitude of more than 100m in the non-heating season, as well as horizontally transferred from surrounding areas above the altitude of more than 240m. But in the heating season, O3 close to the ground by vertical transmission was generated from gas-phase chemical processes above the altitude of more than 240m, and horizontally transferred from surrounding areas above 500m.The PM2.5 process analysis indicates that the contributions of different process on diurnal variation of PM2.5 concentrations in Qingdao were inconsistent in different seasons. The main sources of surface PM2.5 were emissions, aqueous processes and vertical transport occurred during the afternoon to next morning in the non-heating season, the main removal processes of horizontal transport, aerosol chemical processes, dry deposition and the vertical transport occurred at noon; PM2.5 close to the ground by vertical transport was generated not only from emissions but also from gas-phase chemical processes above the altitude of more than 40m in the non-heating season, as well as horizontally transferred from surrounding areas above the altitude of more than 240m. But in the heating season, the main source of surface PM2.5 was emission, the main removal processes of horizontal transport, dry deposition, aerosol chemical processes, the vertical transport occurred at noon and aqueous processes; PM2.5 close to the ground by vertical transport was generated from aerosol chemical processes above the altitude of more than 100m, and horizontally transferred from surrounding areas above 500m.Results of the indicator analysis show that Qingdao is located in coastal VOC control belt, generation of O3 in Qingdao was due to the cooperative control of VOC and NOx or only control of VOC in the non-heating season. But in the heating season, the coastal VOC control belt expands from coastal regions to inland, generation of O3 in Qingdao was due to the control of VOC.Results of the scenario simulation show that abatement of NH3 and SO2 in North China could control PM2.5 concentrations in Qingdao to the maximum extent in the non-heating season. Abatement of NH3 and NOx emissions could significantly reduce PM2.5 concentrations in the heating season. The BTH (Beijing city, Tianjing city and Hebei province), SD (northwest Shandong province) and QD (Qingdao city) region were the main sources of PM2.5 pollution in Qingdao city, with contribution rates of 27.4%,28.5% and 24.1%, respectively. The major contributing components of BTH region were NO3- and NH4+, and the major contributing components of Yantai city may were S042-.Therefore, O3 and PM2.5 pollution in Qingdao could be controlled by reducing emissions of VOC and SO2 in NCP in the non-heating season. While in the heating season, the reduction of NOx emissions in BTH could control PM2.5 concentration in Qingdao, but would also lead to the increase of O3 concentration due to the O3 generation under the control of VOC. Thus, to effectively curb O3 and PM2.5 pollution in Qingdao in the heating season, except considering control factor of single pollutant, the characteristics of complex air pollution must be considered. |
PDF Full Text Request