Atmospheric impact of the surface chemistry of nitrogen and halogen species over soil, ocean, and snow
Chemical reactions on various ground surfaces, including soil, snow, and ocean are increasingly recognized to play an important role in the chemistry of the atmospheric boundary layer. However, our understanding of this surface chemistry and the transport to/from the ground is still incomplete. This is, in part, because the observation of species undergoing chemistry at the surface requires analytical methods that overcome sampling artifacts and allow the determination of vertical fluxes. In addition, most atmospheric chemistry models were not designed to include chemical reactions and bidirectional fluxes at the ground.
Here the significance of chemistry at the ground (soil), snow, and ocean surface will be illustrated for three different chemical systems and environments: Nitrogen chemistry in polluted urban areas impacts radical levels and thus ozone and aerosol formation. Iodine chemistry over the tropical ocean lowers background ozone concentrations in the marine boundary layer and in coastal cities. Bromine chemistry over snow is known to deplete ozone and mercury during spring. Observations with long-path Differential Optical Absorption Spectroscopy instruments, combined with high-resolution one-dimensional atmospheric chemistry and transport models elucidate the chemistry and transport processes in these environments. These results allow identification of common characteristics, uncertainties, and a better quantitative descriptions of the influence of the surface on the composition of the overlaying atmosphere.