Model Simulations and Predictions of Hydroxymethanesulfonate (HMS) in the Beijing-Tianjin-Hebei Region, China: Roles of Aqueous Aerosols and Atmospheric Acidity

Abstract

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 SO 2 and NO x compared to NH 3 alter the atmospheric acidity, which is a critical factor leading to the rising importance of HMS in particulate sulfur species.

Hydroxymethanesulfonate and Sulfur(IV) in Fairbanks Winter During the ALPACA Study

“…Overall, there are many factors that affect the concentrations of various S(IV) species in Fairbanks. High ALWC is more significant during periods of moderate temperatures and high RH, similar to what has been observed over the NCP, 27 (where ALWC is exceptionally high relative to Fairbanks). However, our analysis shows that in Fairbanks the most important factor identified is the extreme low temperatures.…”

“…An increasing PM 2.5 particle pH resulting from sulfur reductions could also produce a higher proportion of aldehyde-S­(IV) adducts relative to sulfate. Wang et al suggest a similar relative increase in HMS relative to SO 4 2– over the NCP due air quality regulations aimed at reducing PM 2.5 concentrations.…”

“… 26 There is also evidence of HMS formation in fine particle liquid water. 24 , 27 In these regions, including HMS in model predictions produced better agreement with observations of sulfur species concentrations. 17 , 28 …”

“…Some rural sites may have higher HMS concentrations than urban areas because of heightened fog and precursor concentrations . There is also evidence of HMS formation in fine particle liquid water. , In these regions, including HMS in model predictions produced better agreement with observations of sulfur species concentrations. , …”

Supplementary material to "Technical note: Influence of different averaging metrics and temporal resolutions on aerosol pH calculated by thermodynamic modeling"

“…The parameterization scheme for the heterogeneous uptake of sulfate in KPP was referred to Wang et al (2014) and Wang et al (2021). Similar to earlier studies (Wang et al, 2024), an apparent reactive uptake coefficient for SO2 was adopted to compensate for the underestimate of sulfate during the North China winter season, and the reactive uptake coefficient (γ) was taken as 10 -4 at RH > 50%. Gaseous and particle dry deposition adhered to a conventional resistance-in-series scheme (Wesely, 1989).…”