Two graphs from the study.
Observation-based estimations of characteristic buffering time, τbuff, under different ambient conditions. The scenarios shown are characteristic for the Southeastern U.S. (SE-US), western Europe (WE), northern India (NI), and the North China Plain (NCP). Only sulfate formation from the multiphase reactions in aerosol waters are considered in (A), while sulfate formation due to the sulfur dioxide oxidation in the gas-phase by hydroxyl radicals is included in (B). Credit: Zheng et al. [2024], Figure 3
Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: AGU Advances

Multiphase reactions are important sources of secondary aerosols and fine particulate matter in the atmosphere, influencing air quality, climate, and human health. Acidity, a key parameter in multiphase reactions affecting gas-liquid partitioning and reaction rates, is particularly strong in sulfate formation, a major component of fine particulate in the atmosphere. Aerosol acidity largely regulates the chemistry of atmospheric particles and their environmental effects. Understanding the role of these reactions is a major challenge.

By accounting for competing effects of multiphase buffering and acidification, Zheng et al. [2024] developed a new method to evaluate the role of these reactions on aerosol pH. Over most populated regions, the buffering effect is so strong that it overwhelms the influence of acidification and sustains sulfate production from high pH-favored multiphase reactions. This highlights the importance of anthropogenic ammonia emissions in buffering the acidity of aerosol particles and in regulating the change of atmospheric compositions via multiphase reactions.

Citation: Zheng, G., Su, H., Andreae, M. O., Pöschl, U., & Cheng, Y. (2024). Multiphase buffering by ammonia sustains sulfate production in atmospheric aerosols. AGU Advances, 5, e2024AV001238. https://doi.org/10.1029/2024AV001238

—Don Wuebbles, Editor, AGU Advances

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