Quantitative Decomposition of Influencing Factors to Aerosol pH Variation over the Coasts of the South China Sea, East China Sea, and Bohai Sea
Guochen Wang, Ye Tao, Jia Chen, Chengfeng Liu, Xiaofei Qin, Hao Li, Long Yun, Mingdi Zhang, Haitao Zheng, Huaqiao Gui, Jianguo Liu, Juntao Huo, Qingyan Fu, Congrui Deng, Kan Huang
Abstract
Aerosol acidity acts as a crucial parameter in regulating atmospheric chemistry; however, quantifying its major influencing factors is rare, especially at coastal regions which represent complex interfaces from both terrestrial and marine emissions and land breeze–sea breeze interactions. Three field campaigns conducted at coastal sites of the South China Sea, East China Sea, and Bohai Sea all revealed high aerosol acidity. By using a decomposition method based on the NHx phase-partitioning equilibrium, NH3 and relative humidity (RH) were identified as the two most important driving factors to hourly aerosol pH variation. In addition, the contributions of driving factors to the diel aerosol pH variation were first revealed. RH and temperature tended to increase (decrease) the aerosol pH during nighttime (daytime), while NH3 exhibited a reverse diurnal pattern. The diel cycles of aerosol liquid water and gas-particle partitioning of ammonium were responsible for the behavior of the driving factors of diel aerosol pH variation. Moreover, this study also highlighted that nonvolatile cations accounted for 8%–17% of the hourly aerosol pH variation, demonstrating that the role of sea salts in regulating coastal aerosol acidity cannot be ignored.