Plastics have become
ubiquitous in the world’s oceans, and
recent work indicates that they can transfer from the ocean to the
atmosphere in sea spray aerosol (SSA). Hazardous chemical residues
in plastics, including bisphenol-A (BPA), represent a sizable fraction
of consumer plastics and have been measured consistently in air over
both terrestrial and marine environments. However, the chemical lifetimes
of BPA and mechanisms by which plastic residues degrade with respect
to photochemical and heterogeneous oxidation processes in aerosols
are unknown. Here, we present the photosensitized and OH-initiated
heterogeneous oxidation kinetics of BPA in the aerosol phase consisting
of pure-component BPA and internal mixtures of BPA, NaCl, and dissolved
photosensitizing organic matter. We found that photosensitizers enhanced
BPA degradation in binary-component BPA + photosensitizer aerosol
mixtures when irradiated in the absence of OH. OH-initiated degradation
of BPA was enhanced in the presence of NaCl with and without photosensitizing
species. We attribute this enhanced degradation to greater mobility
and thus reaction probability between BPA, OH, and reactive chlorine
species (RCS) formed through reaction between OH and dissolved Cl–in the more liquid-like aerosol matrix in the presence
of NaCl. Addition of the photosensitizers in the ternary-component
BPA + NaCl + photosensitizer aerosol led to no enhancement in the
degradation of BPA following light exposure compared to the binary-component
BPA + NaCl aerosol. This was attributed to quenching of triplet state
formation by dissolved Cl–in the less viscous aqueous
aerosol mixtures containing NaCl. Based upon measured second-order
heterogeneous reaction rates, the estimated lifetime of BPA with respect
to heterogeneous oxidation by OH is one week in the presence of NaCl
compared to 20 days in the absence of NaCl. This work highlights the
important heterogeneous and photosensitized reactions and the role
of phase state, which affect the lifetimes of hazardous plastic pollutants
in SSA with implications for understanding pollutant transport and
exposure risks in coastal marine environments.