Study of 4-Benzoylbenzoic Acid as a Proxy of Environmental Photosensitizers

Sea-spay aerosols (SSA) released from the marine boundary layer (MBL) through wave breaking and bubble bursting contain marine chromophoric dissolved organic matter (m-CDOM). These complex substances can act as photosensitizers of atmospheric trace gases, opening previously unrecognized chemical reactions within SSA. Previous studies seeking to replicate the optical and photochemical properties of m-CDOM have used small molecules, such as pyruvic acid, to simulate m-CDOM. This work proposes an additional photosensitizer, 4-benzoylbenzoic acid (4BBA), to introduce the effects of aromaticity and low solubility. The pH dependent speciation and optical activity of 4BBA was studied experimentally and theoretically, yielding excellent agreement. Photoexcitation of 4BBA within the solar spectra is shown to catalyze indirect mass transfer and oxidation of nonanoic acid, a proxy fatty acid found in SSA. As m-CDOM can likely only be modeled by a combination of several molecules, this work offers an additional aromatic and low solubility chromophore towards a complete model of m-CDOM