Articles | Volume 18, issue 10
Research article
28 May 2018
Research article |  | 28 May 2018

Fine-particle pH for Beijing winter haze as inferred from different thermodynamic equilibrium models

Shaojie Song, Meng Gao, Weiqi Xu, Jingyuan Shao, Guoliang Shi, Shuxiao Wang, Yuxuan Wang, Yele Sun, and Michael B. McElroy

Data sets

E-AIM model S. Clegg, P. Brimblecombe, and A. Wexler

ISORROPIA II model A. Nenes, C. Fountoukis, S. Pandis, and C. Pilinis

S. Song and J. Shao Bug fixes for ISORROPIA II stable mode

Short summary
Severe haze events occur frequently over northern China, especially in winter. Acidity plays a critical role in the formation of secondary PM2.5 and its toxicity. Using field measurements of gases and particles to critically evaluate two thermodynamic models routinely employed to determine particle acidity, we found that China's winter haze particles are generally within a moderately acidic range (pH 4–5) and not highly acidic (0) or neutral (7) as has been previously reported in the literature.
Final-revised paper