Program
 
Special Session 5: Ocean-atmosphere interaction, multi-scale climate variability and their implication for biogeochemical processes
 

 
 
1425
Evolution of secondary aerosols during transport at coastal receptor site of the YRD
Wednesday 11th @ 1425-1445
Room 1
Min Hu* , State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University
Jianfei Peng, State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University
Zhaoheng Gong, Key Laboratory for Urban Habitat Environmental Science and Technology, School of Environment and Energy, Peking University Shenzhen Graduate School
Ming Wang, State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University
Weiwei Hu, State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University
Ming Wang, State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University
Wei Cao, State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University
Zhijun Wu, State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University
Xudong Tian, Zhejiang Province Environment Monitoring Centre, Hangzhou, Zhejiang 310015, China
Song Guo, State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University
Presenter Email: minhu@pku.edu.cn
Understanding the evolution of aerosols in the atmosphere is of great importance for improving air quality and reducing aerosol-related uncertainties in global climate simulations. We present a case study of a severe haze episode that occurred at the Wenling receptor site in the YRD region. This coastal site is located downwind of the YRD region and is generally not exposed to local emissions. Thus, the haze episode that is described provided a unique opportunity to study aerosol transport from a polluted region to an unpolluted region. Both backward trajectory analysis and local meteorology conditions were used to investigate the origins of the air mass and to categorize the pollution types present. In addition, the influence of urban emissions on the chemical composition of the atmospheric aerosols was investigated. Evolution of particle size distribution, cloud condensation nuclei (CCN) concentration, and inorganic and organic aerosol chemical composition during transport were also examined and are quantified. An increase in photochemical age from 5 h to more than 25 h and a progressive increase in the fitted mean particle diameter from 70 nm to approximately 300 nm were observed. According to the pollution features and meteorology conditions involved, pollution accumulation (PA), sea breeze (SB), and land breeze (LB) periods were identified. Concentrations of black carbon (BC), hydrocarbon-like organic aerosols (HOA), semi-volatile oxidized organic aerosols (SV-OOA), and nitrate increased by 7-fold up to 39-fold when the air masses passed through Taizhou, a nearby city. In addition, nitrate and SV-OOA dominated the aerosol composition in the urban outflow plumes (52% and 18%, respectively), yet they gradually decreased in concentration during transport. In contrast, sulfate and the low-volatile oxidized organic aerosols (LV-OOA) exhibited more regional footprints and potentially have similar formation mechanisms. The atomic oxygen-to-carbon (O/C) ratio also increased from 0.45 to 0.9, thereby suggesting that rapid formation of highly oxidized secondary organic aerosols (SOA) occurred during transport. Overall, these results provide valuable insight into the evolution of the chemical and physical features of aerosol pollution during transport and also highlight the need for regulatory controls of nitrogen oxides, sulfur dioxide, and VOCs to improve air quality on different scales. Since particulate nitrate and SOA can be formed from nitrogen oxides and VOCs emitted from vehicles in the urban atmosphere, regulatory controls of urban nitrogen oxides and VOCs emission may significantly improve air quality. However, given that the concentration of nitrate decreases during the transport of emissions, this benefit may be limited to urban areas and nearby downwind regions. In contrast, sulfate has a regional footprint and its formation process is less influenced by urban emissions. Thus, sulfate is a key factor in regional heavy pollution and control of sulfur dioxide from regional industrial and domestic sources will benefit even broader regions.