Modeling Heterogeneous Reactions on Mineral Aerosol with Detailed Schemes for the Surface Processes

Atmospheric particulates affect global biogeochemical cycles by providing reactive surfaces for multiphase or heterogeneous reactions and serving as carriers for many condensed and sorbed species. Although heterogeneous reactions on the surface of mineral aerosols have already recently been coupled into models for global climate and regional air quality, most of these models deal with heterogeneous reactions with simple assumptions. Many details, such as chemical composition of the aerosol, and the changing surface chemical and physical characteristics during the long distant transport, are seldom considered into models that include heterogeneous reactions. Laboratory studies on individual particles have shown that dust reactivity greatly depends on the composition of the mineral aerosol. Field campaigns also show that atmospheric particles are often coated or associated with nitrate and sulfate species and a water film. Some laboratory experiments have shown how the coating process affects the surface properties or reactions of particles, especially the heterogeneous reactions on the surface of aerosols. To better represent the complexity of the atmosphere, it is necessary to increase the level of detail incorporated into atmospheric chemistry models with respect to heterogeneous reactions.

A detailed multiphase chemistry box model, which consists of (i) a gas-phase chemistry module including 83 chemical species and 185 gas phase reactions (ii) and a size- and chemically-resolved aerosol module with both dynamic and equilibrium approaches to solve the aerosol dynamics, is developed and used to study heterogeneous reactions on mineral aerosols.

How mineralogy and chemical compositions of dust affect the dust reactivity on the surface will be investigated in the box model by treating different compositions with different reactivity and chemical mechanism on the surface. The surface chemical and physical characteristics of the aerosol and the changing of aerosol compositions will be tracked. How the changing and different coating on particles effect heterogeneous reactions will also be assessed in the box model.