Sea spray aerosol (SSA) has been shown to undergo heterogeneous reactions with trace atmospheric gases. Such reactions can have sizeable impacts on the physicochemical properties of the SSA, leading to changes in their climate relevant characteristics (e.g., water uptake properties, light scattering properties, etc.). Previous studies have focused on the well-known reactions involving nitrogen oxides such as NO2, NO3, HNO3, and N2O5 with NaCl to yield nitrate salt products. For example, the reaction of nitric acid with sodium chloride is shown in (1): NaCl(aq) + HNO3(g) à NaNO3(aq) + HCl(g,aq) (1). However, it is well known that SSA consists of more than just chloride salts, with contributions from sugars, lipids, and other biologically derived molecules. These components also have reaction sites for heterogeneous chemistry. Here we show a different reaction pathway with nitric acid from that shown in (1) for biological SSA composed of lipopolysaccharides, an important part of the cell wall of gram negative bacteria. In particular, we propose an acid-base type reaction on some of the basic components of LPS which can be written as follows: HNO3(g) + R-COONa(s) à NaNO3 + R-COOH (2), and HNO3(g) + R-HPO4Na(s) à NaNO3 + R-H2PO4 (3). The results from Raman microspectroscopy, ATOFMS, XPS, and SEM-EDX to further understand the heterogeneous reactivity of biologically derived SSA will be presented. We compare the relative rates of reaction for pathways (2) and (3) with that for the well-known pathway presented in (1). Additionally, reactions involving SSA derived from other relevant biomolecules with HNO3 are explored.

Insights into the heterogeneous reactivity of biologically derived components of sea spray aerosols

251st National Meeting (2016)

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