Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, United States.
J Phys Chem A. 2023 Jun 1;127(21):4724-4733. doi: 10.1021/acs.jpca.3c00127. Epub 2023 May 18.
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.
塑料在世界海洋中无处不在，最近的研究表明，它们可以通过海雾气溶胶（SSA）从海洋转移到大气中。塑料中含有危险的化学残留物，包括双酚 A（BPA），这是消费者塑料的重要组成部分，并且在陆地和海洋环境的空气中都有持续的测量。然而，BPA 的化学寿命以及塑料残留物在气溶胶中光化学和非均相氧化过程中降解的机制尚不清楚。在这里，我们提出了纯 BPA 和气溶胶中 BPA 的内混物的光敏和 OH 引发的非均相氧化动力学，这些气溶胶由纯 BPA 以及 BPA、NaCl 和溶解的光敏有机物的内混物组成。我们发现，当在没有 OH 的情况下照射时，光敏剂增强了二元 BPA + 光敏剂气溶胶混合物中 BPA 的降解。在有和没有光敏物种的情况下，NaCl 的存在增强了 OH 引发的 BPA 降解。我们将这种增强的降解归因于在 NaCl 存在下更具流动性，从而使 BPA、OH 和通过 OH 与溶解的 Cl 在更具液态的气溶胶基质中反应形成的反应性氯物种（RCS）之间的反应概率增加。在三元 BPA + NaCl + 光敏剂气溶胶中添加光敏剂，与二元 BPA + NaCl 气溶胶相比，光照后 BPA 的降解没有增强。这归因于在含有 NaCl 的粘性较低的水相气溶胶混合物中，溶解的 Cl 对三重态形成的猝灭。根据测量的二级非均相反应速率，与不存在 NaCl 相比，BPA 与 OH 的非均相氧化的估计寿命在有 NaCl 的情况下为一周。这项工作突出了非均相和光敏反应的重要性以及相态的作用，这影响了 SSA 中危险塑料污染物的寿命，对理解沿海海洋环境中的污染物传输和暴露风险具有重要意义。
