Heterogeneous atmospheric chemistry and photochemistry of mineral dust and its components – oxides, carbonates and clays

In recent years, there has been an increasing interest in the heterogeneous chemistry of atmospheric particulate matter due to the impact these reactions have on the chemical balance of the Earth’s atmosphere. Particles in the atmosphere provide reactive surfaces for adsorption as well as for important chemical and photochemical reactions. Among all the particulate matter, mineral dust aerosol which is mainly emitted in to the atmosphere from arid desert regions comprises a significantly large mass fraction. These dust particles can react with trace atmospheric gases such as NO₂, HNO₃, SO₂, O₃, HCl and organics and further undergo photochemical reactions during long range transport from the source region to remote locations due to wind currents. These reactions can change the physicochemical properties of the mineral dust particle and thus will alter the particles hygroscopicity, cloud nucleating properties and further reactivity comparative to original dust particle.

Additionally, heterogeneous reactions on mineral dust and its components may provide missing link for some reaction schemes that cannot be explained solely with gas phase reactions. They may also provide additional reaction pathways which may explain the discrepancies between laboratory and field measurements. In the Grassian laboratory, a combination of spectroscopy, microscopy and particle analysis is used to gain understanding of mechanisms and kinetics of heterogeneous reactions of mineral dust particles/model systems. Further, the kinetic data obtained from chamber studies are incorporated to global atmospheric models in collaborating with atmospheric modelers to evaluate the effect of heterogeneous reactions on mineral dust on the atmosphere. Ongoing projects in our lab include the studying of chemical and photochemical reactions of trace atmospheric gases to better understand the night time and daytime chemistry of mineral dust aerosol.