The Curious Behavior of Atmospheric Aerosol Acidity, Rodney Weber, Georgia Tech

Details

Atmospheric aerosol particles can reach acidity levels comparable to those of a lead–acid battery due to sulfate-driven strong acidity. Sulfur-containing aerosol species have long been associated with adverse health outcomes, including their central role in the 1952 London Fog mortality event and in the Harvard Six Cities Study (1974–1991). Controlled exposure studies in the 1990s further linked sulfuric acid aerosols to respiratory impairments. Although U.S. sulfur emissions and atmospheric sulfate concentrations have declined dramatically over recent decades, epidemiological studies continue to find strong associations between particle sulfur and negative health effects. Paradoxically, fine particle pH has not changed substantially over this same period, despite large reductions in the dominant acidic component. Recent studies utilizing aerosol thermodynamic models provide insight into this behavior, revealing unexpected stability in particle acidity under evolving emissions. In this talk, I will highlight this phenomenon using results from a health study that spans major reductions in coal-related sulfur emissions, and I will discuss new findings on the drivers of particle acidity across a range of urban and agricultural environments. Together, these results point to a more refined understanding of particle acidity and its implications for atmospheric chemistry, air quality, and human and environmental health.

Atmospheric aerosol particles can reach acidity levels comparable to those of a lead–acid battery due to sulfate-driven strong acidity. Sulfur-containing aerosol species have long been associated with adverse health outcomes, including their central role in the 1952 London Fog mortality event and in the Harvard Six Cities Study (1974–1991). Controlled exposure studies in the 1990s further linked sulfuric acid aerosols to respiratory impairments. Although U.S. sulfur emissions and atmospheric sulfate concentrations have declined dramatically over recent decades, epidemiological studies continue to find strong associations between particle sulfur and negative health effects. Paradoxically, fine particle pH has not changed substantially over this same period, despite large reductions in the dominant acidic component. Recent studies utilizing aerosol thermodynamic models provide insight into this behavior, revealing unexpected stability in particle acidity under evolving emissions. In this talk, I will highlight this phenomenon using results from a health study that spans major reductions in coal-related sulfur emissions, and I will discuss new findings on the drivers of particle acidity across a range of urban and agricultural environments. Together, these results point to a more refined understanding of particle acidity and its implications for atmospheric chemistry, air quality, and human and environmental health.