Photochemical Singlet Oxygen Production by Atmospheric Road Dust: Implications for Urban Pollutant Lifetimes

Abstract:

Road dust, the largest anthropogenic source of fine particulate matter in Canada and the United States, consists of a complex mixture of brake and tire wear, pavement particles, crustal material, semi-volatile vehicle exhaust components, and natural organic matter. Although the composition and health effects of road dust are relatively well-studied, little is known regarding its atmospheric reactivity. Our group recently showed that road dust collected from a single location in Edmonton, Alberta, is a photochemical source of singlet oxygen, an important environmental oxidant. Here, we present comprehensive measurements of singlet oxygen production by aqueous suspensions of pooled road dust samples collected from three road types (residential, arterial, and expressway) in Toronto, Ontario. In addition, we report the influence of organic matter content, particle size, and particle mass loadings on singlet oxygen production by these samples. Finally, we report quantum yields for singlet oxygen production by aqueous sample extracts and compare these values to those reported for other types of dissolved organic matter. These results highlight the photochemical activity of road dust and provide further evidence that its photochemistry can influence the lifetime of urban pollutants.