Model
Simulations and Predictions of Hydroxymethanesulfonate
(HMS) in the Beijing-Tianjin-Hebei Region, China: Roles of Aqueous
Aerosols and Atmospheric Acidity
posted on 2023-12-28, 20:10authored byHaoqi Wang, Jiacheng Li, Ting Wu, Tao Ma, Lianfang Wei, Hailiang Zhang, Xi Yang, J. William Munger, Feng-Kui Duan, Yufen Zhang, Yinchang Feng, Qiang Zhang, Yele Sun, Pingqing Fu, Michael B. McElroy, Shaojie Song
Hydroxymethanesulfonate
(HMS) has been found to be an abundant
organosulfur aerosol compound in the Beijing-Tianjin-Hebei (BTH) region
with a measured maximum daily mean concentration of up to 10 μg
per cubic meter in winter. However, the production medium of HMS in
aerosols is controversial, and it is unknown whether chemical transport
models are able to capture the variations of HMS during individual
haze events. In this work, we modify the parametrization of HMS chemistry
in the nested-grid GEOS-Chem chemical transport model, whose simulations
provide a good account of the field measurements during winter haze
episodes. We find the contribution of the aqueous aerosol pathway
to total HMS is about 36% in winter in Beijing, due primarily to the
enhancement effect of the ionic strength on the rate constants of
the reaction between dissolved formaldehyde and sulfite. Our simulations
suggest that the HMS-to-inorganic sulfate ratio will increase from
the baseline of 7% to 13% in the near future, given the ambitious
clean air and climate mitigation policies for the BTH region. The
more rapid reductions in emissions of SO2 and NOx compared to NH3 alter the atmospheric
acidity, which is a critical factor leading to the rising importance
of HMS in particulate sulfur species.