Contribution of Hydroxymethane Sulfonate to Ambient Particulate Matter: A Potential Explanation for High Particulate Sulfur During Severe Winter Haze in Beijing

Abstract

PM2.5 during severe winter haze in Beijing, China, has reached levels as high as 880 μg/m3, with sulfur compounds contributing significantly to PM2.5 composition. This sulfur has been traditionally assumed to be sulfate, although atmospheric chemistry models are unable to account for such large sulfate enhancements under dim winter conditions. Using a 1‐D model, we show that well‐characterized but previously overlooked chemistry of aqueous‐phase HCHO and S(IV) in cloud droplets to form a S(IV)‐HCHO adduct, hydroxymethane sulfonate, may explain high particulate sulfur in wintertime Beijing. We also demonstrate in the laboratory that methods of ion chromatography typically used to measure ambient particulates easily misinterpret hydroxymethane sulfonate as sulfate. Our findings suggest that HCHO and not SO2 has been the limiting factor in many haze events in Beijing and that to reduce severe winter pollution in this region, policymakers may need to address HCHO sources such as transportation.

Measurement techniques of identifying and quantifying sulfur compounds in fog and cloud water

“…Similarly, AMS measurements may have identified HMS as sulfate as explained above. This is also consistent with the explanation provided by Moch at al. (2018) and Song at al.…”

Retrospective analysis of 2015–2017 wintertime PM<sub>2.5</sub> in China: response to emission regulations and the role of meteorology

“…Increasing numbers of observations have revealed that anthropogenic emission-relevant aerosol species, such as sulfate, nitrate and ammonium (denoted as SNA), are the predominant inorganic species in the wintertime PM 2.5 in China (Y. S. Yang et al, 2015). Various reaction paths during haze events have also been proposed (e.g., Zheng et al, 2015;Cheng et al, 2016;Wang et al, 2016;Moch et al, 2018;Wang et al, 2018;Shao et al, 2019). For example, Moch et al (2018) used a 1-D model and revealed the importance of aqueousphase chemistry of HCHO and S(IV) in cloud droplets by forming a S(IV)-HCHO adduct, hydroxymethane sulfonate.…”

“…Various reaction paths during haze events have also been proposed (e.g., Zheng et al, 2015;Cheng et al, 2016;Wang et al, 2016;Moch et al, 2018;Wang et al, 2018;Shao et al, 2019). For example, Moch et al (2018) used a 1-D model and revealed the importance of aqueousphase chemistry of HCHO and S(IV) in cloud droplets by forming a S(IV)-HCHO adduct, hydroxymethane sulfonate. Shao et al (2019) implemented four heterogeneous sulfate formation mechanisms (via H 2 O 2 , O 3 , NO 2 and transition metal ions on aerosols) into GEOS-Chem model, which partially reduced the modeled low bias in sulfate concentrations.…”

ToF‐SIMS analysis of chemical composition of atmospheric aerosols in Beijing

“…The oxygen‐containing fragment ions, such as C 2 H 3 O + , C 14 H 7 O 2 + , C 3 H 7 O + , and C 11 H 14 O 5 + , and some oxygen‐containing unsaturated hydrocarbon ions even over m/z 200, such as C 16 H 14 O + , C 17 H 13 O 3 + , and C 22 H 18 O 4 + , may represent alcohols and carbonyl compounds in the atmosphere, which are mainly from automobile exhaust and atmospheric photochemical reactions . The nitrogen‐containing fragment ions and their oxidation derivatives in the atmosphere, such as C 2 H 7 N 3 + , C 2 H 2 N + , C 4 H 12 NO + , C 3 H 8 NO + , and C 5 H 12 N 2 O 3 + , which may be the heterocyclic compounds and the sulfur‐containing fragment ions and their oxidation derivatives, such as C 2 H 4 S 3 + , C 8 H 3 S + , and C 7 H 15 SO + , which may be the thiols and sulfonates are produced mainly by the burning of fossil fuels, biomass, and garbage, as well as vehicle emissions and, even, cooking, with secondary formation produced by landfill fermentation, organic solvent volatility, hydrocarbon oxidation, etc. In Table , unsaturated hydrocarbons ions, including C 16 H 10 + , C 20 H 12 + , and C 22 H 12 + , may be polycyclic aromatic hydrocarbons (PAHs) .…”