Influence of Organic Coatings on Ozone Photochemistry at the TiO2 Surface

Mineral dust accounts for a significant fraction of aerosol mass loading in the atmosphere, with an estimated 1600 Tg emitted annually. Upon its release into the atmosphere, mineral dust can undergo long-range transport into urban areas, where it can mix with local pollution and affect climate, air quality, and health. Dust -pollutant interactions can alter the concentration of trace gases in the atmosphere, with many of these interactions promoted by light . The morphology, chemical composition, and reactivity of dust particles themselves can also change upon reaction with trace gases; in particular, field observations have shown that these reactions can result in the formation of inorganic and organic coatings on mineral dust surfaces. Although many studies have shown that viscous organic coatings can influence the uptake of trace gase s by particles, little is known about the influence of these coatings on the photocatalytic capabilities of mineral dust. Here, we present results from aerosol flow tube studies investigating the influence of organic coatings on ozone photodecomposition by TiO₂ particles, which we use as a simple model for the photoactive component of atmospheric dust. Specifically, we explore ozone photodecomposition by TiO₂ in the presence of two organic coatings of differing viscosity and as a function of coating thickness and relative humidity. Our results will provide new insights into the evolution of dust photochemistry with atmospheric transport, as well as the influence of atmospherically processed dust on urban air quality.