Uptake of Atmospheric Gases
at Aqueous Surfaces

In collaboration with Bruce Garrett and Liem Dang at PNNL and Pavel Jungwirth and Martina Roeselová at the Academy of Sciences of the Czech Republic, the Tobias group is carrying out molecular dynamics (MD) simulations to provide a detailed understanding of the uptake of atmospheric gases — such as water, hydroxyl radical, and ozone — at the interface between air and aqueous solutions. 

For example, the schematic below shows the interaction of ozone (blue) with an aqueous solution of NaBr.  The close contact of ozone with the bromide ion (purple) at the interface is obvious and supports experimental observations in the Finlayson-Pitts group, interpreted using the MAGIC model of the Dabdub group, of oxidation of bromide by ozone at the interface.

Top view of ozone interacting with a bromide ion at the surface of
an aqueous solution of NaBr

This snapshot shows the impending collision/reaction of ozone with the surface and the close interaction of ozone with a bromide ion once it reaches the interface.

The atmospheric oxidants being studied exhibit surfactant activity, which has important implications for heterogeneous reactions of these species, particularly with halide ions and with organics adsorbed on the surfaces of particles.