Due to globally increasing numbers of single-use consumer products, significant amounts of plastic waste are polluting the world’s oceans. Plastics can become airborne in sea spray with an estimated emission flux of up to 22 megatons annually. Bisphenol-A (BPA), an additive in epoxy resins and polycarbonate plastics, is a known persistent organic pollutant found ubiquitously in both seawater and aerosol in the marine environment. However, the chemical lifetime of BPA with respect to oxidation by photosensitized and heterogeneous reactions with OH radicals in the presence of relevant sea spray aerosol (SSA) constituents are unknown. In this work, an extractive electrospray ionization high-resolution time-of-flight mass spectrometer (EESI-HR-TOF) was utilized to determine the uptake kinetics of OH-mediated and photosensitized degradation of BPA in both pure-component lab-generated aerosol and SSA mimics containing different levels of dissolved ions (Na⁺and Cl^-) and photosensitizers, including 4-benzoylbenzoic acid (4-BBA) and humic acid. A potential aerosol mass oxidative flow reactor equipped with an external ozone generator and both 369 nm and 254 nm lamps was used to simulate different oxidation and photochemical degradation levels. Results show that the uptake coefficient of OH by BPA increases the most when mixed with NaCl, independent of whether photosensitizers are also present. When exposed to 369nm light, both 4-BBA and humic acid increased the rate of degradation of BPA with more efficient photosensitization in the presence of 4-BBA, which is an effect that has been seen in previous literature. We attribute the enhanced degradation of BPA to the generation of Cl radicals when OH heterogeneously reacts with Cl^- and through formation of reactive oxygen species by photosensitization of 4-BBA and humic acid, and these results suggest that the lifetime of BPA decreases by a factor of two in the presence of these relevant SSA mixtures. This work contributes to a growing understanding of the processes affecting the emission and degradation of toxic plastic additives in the environment and may help guide future atmospheric risk assessment models of BPA.

Samantha Kruse

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