Heterogeneous uptake and reaction of nitrogen oxides and volatile organic compounds on the surface of atmospheric particles including oxides, carbonates, soot and mineral dust: Implications for the chemical balance of the troposphere

The role of heterogeneous reactions of trace atmospheric gases on solid aerosol surfaces in the troposphere is not well understood. In this review, the heterogeneous chemistry of nitrogen oxides and volatile organic compounds on the surface of atmospherically relevant particles such as oxides, soot, carbonates and mineral dust is discussed. The approach to unravelling both the molecular level details and the global significance of these reactions is one that combines laboratory investigations and atmospheric chemistry models. The laboratory investigation utilizes spectroscopic measurements to provide an understanding of the details of the chemistry that occurs in the gas phase and on the surface of the particle together with kinetic measurements in order to quantify the rates of these reactions. These fundamental measurements provide a basis for understanding the detailed molecular level physical chemistry of atmospheric processes. The kinetic data, together with the details provided by the spectroscopic studies, are incorporated into atmospheric chemistry models in order to gain a greater understanding of the role that heterogeneous chemistry plays in the chemical balance of the troposphere. Several examples from the present author's laboratory are discussed in this review. These examples include: (i) the heterogeneous uptake and reactivity of nitrogen oxides (nitrogen dioxide and nitric acid) on oxide and dust particles; (ii) the role of water in the heterogeneous uptake of nitric acid on oxide, carbonate and dust particles; (iii) the heterogeneous production of nitrous acid on silica and soot particles; and (iv) the heterogeneous uptake and reactivity of acetone and other carbonyl compounds on oxide and mineral dust particles.