Department of Chemistry, University of Wisconsin, Madison, WI 53706, USA.
Chem Soc Rev. 2018 Apr 3;47(7):2374-2400. doi: 10.1039/c7cs00008a.
Sea spray aerosol particles (SSA), formed through wave breaking at the ocean surface, contribute to natural aerosol particle concentrations in remote regions of Earth's atmosphere, and alter the direct and indirect effects of aerosol particles on Earth's radiation budget. In addition, sea spray aerosol serves as suspended surface area that can catalyze trace gas reactions. It has been shown repeatedly that sea spray aerosol is heavily enriched in organic material compared to the surface ocean. The selective enrichment of organic material complicates the selection of representative molecular mimics of SSA for laboratory or computational studies. In this review, we first provide a short introduction to SSA formation processes and discuss chemical transformations of SSA that occur in polluted coastal regions and remote pristine air. We then focus on existing literature of the chemical composition of nascent SSA generated in controlled laboratory experiments and field investigations. We combine the evidence on the chemical properties of nascent SSA with literature measurements of SSA water uptake to assess SSA molecular composition and liquid water content. Efforts to speciate SSA organic material into molecular classes and specific molecules have led to the identification of saccharides, alkanes, free fatty acids, anionic surfactants, dicarboxylic acids, amino acids, proteinaceous matter, and other large macromolecules. However to date, less than 25% of the organic mass of nascent SSA has been quantified at a molecular level. As discussed here, quantitative measurements of size resolved elemental ratios, combined with determinations of water uptake properties, provides unique insight on the concentration of ions within SSA as a function of particle size, pointing to a controlling role for relative humidity and the hygroscopicity of SSA organic material at small particle diameters.
海雾气溶胶粒子（SSA）是通过海浪破碎在海洋表面形成的，它们在地球大气的偏远地区贡献了自然气溶胶粒子的浓度，并改变了气溶胶粒子对地球辐射平衡的直接和间接影响。此外，海雾气溶胶充当悬浮的表面积，可以催化痕量气体反应。已经反复证明，与海洋表面相比，海雾气溶胶富含有机物质。有机物质的选择性富集使 SSA 的代表性分子模拟物的选择复杂化，无论是在实验室还是计算研究中。在这篇综述中，我们首先简要介绍 SSA 的形成过程，并讨论在污染沿海地区和偏远原始空气中发生的 SSA 的化学转化。然后，我们将重点放在实验室控制实验和实地调查中生成的初生 SSA 的化学成分的现有文献上。我们将初生 SSA 的化学性质的证据与 SSA 水吸收的文献测量值结合起来，以评估 SSA 的分子组成和液态水含量。将 SSA 有机物质分类为分子类别和特定分子的努力导致了糖、烷烃、游离脂肪酸、阴离子表面活性剂、二羧酸、氨基酸、蛋白质物质和其他大分子的鉴定。然而，到目前为止，只有不到 25%的初生 SSA 有机质量在分子水平上得到了量化。如这里所讨论的，对元素比进行大小分辨的定量测量，结合水吸收特性的测定，提供了有关 SSA 中离子浓度作为粒径函数的独特见解，这表明相对湿度和 SSA 有机物质的吸湿性在小粒径下起着控制作用。
