The present study is the first report of the oxidative potential (OP) of atmospheric PM₁₀ over marine environments. PM₁₀ samples were collected onboard the Fishery Oceanographic Research Vessel Sagar Sampada (SS#359) over the Arabian Sea during April–May, 2017 and analyzed for a variety of chemical species and OPs. The PM₁₀ mass concentration, volume-normalized OP [represented as nmol dithiothreitol (DTT) min^–1 m^–3 or OP_V], and mass-normalized OP (represented as pmol DTT min^–1 μg^–1 or OP_M) over the study region varied from 61 to 184 μg m^–3, 0.69 to 2.08 nmol DTT min^–1 m^–3, and 6 to 26 pmol DTT min^–1 μg^–1, respectively. The study period was classified into two categories (Class-A and Class-B) based on 5-day air mass back trajectories for each sampling location. The mass fraction of mineral dust was ∼2.5 times higher in Class-B samples (representing the Arabian Desert/marine air masses) in comparison with Class-A samples (representing the continental air mass). The average OP_V and OP_M associated with Class-A showed ∼1.5 times higher values as compared to those associated with Class-B. Furthermore, Class-A samples showed ∼95% Cl^– depletion from sea salt aerosol, which was also found to be significantly correlated with OP_M. These observations suggest the importance of free acidity not only in affecting the chemistry of marine atmosphere but also in catalytic generation of reactive oxygen species. Moreover, water-soluble organic nitrogen (WSON) contributes ∼15% to total nitrogen, and the mass fraction of WSON was observed to be positively correlated (R = 0.79) with OP_M, suggesting that water-soluble (WS) nitrogenous organics are highly DTT-active. Further, OP_M also exhibited a significant correlation (R = 0.83) with nss-K⁺, indicating the effect of biomass burning emissions on aerosol OP. In addition, the mass fraction of WS-Mn, WS-Cu, and WS-Zn also correlated significantly with OP_M. Our results also infer that aerosol aging increases their OP. These results have important implications in assessing the effects of continental aerosol on marine atmospheric boundary layer and ocean biogeochemistry.

中文翻译：

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阿拉伯海大气PM _10的化学组成和氧化电位

本研究是大气PM ₁₀在海洋环境中的氧化势（OP）的第一份报告。2017年4月至5月，在阿拉伯海的渔业海洋研究船Sagar Sampada（SS＃359）上采集了PM ₁₀样品，并分析了各种化学物种和OP。在PM ₁₀质量浓度，体积标准化OP [表示为纳摩尔二硫苏糖醇（DTT）分钟^-1米^-3或OP _V ]和质量标准化OP（表示为皮摩尔DTT分钟^-1微克^-1或OP_中号）过研究区域从61到184μgm ^–3，从0.69到2.08 nmol DTT min ^–1不等米^-3，和6至26皮摩尔DTT分钟^-1微克^-1，分别。根据每个采样地点的5天空气质量反演轨迹，研究期分为两类（A类和B类）。与A类样品（代表大陆空气质量）相比，B类样品（代表阿拉伯沙漠/海洋空气质量）的矿物粉尘质量分数高约2.5倍。与A类关联的平均OP _V和OP _M值比B类关联的平均OP _V和OP _M高约1.5倍。此外，A类样品显示出约95％的海盐气溶胶中的Cl ^–损耗，这也与OP _M显着相关。。这些观察结果表明，游离酸度的重要性不仅在于影响海洋大气的化学性质，而且在催化生成活性氧方面也很重要。此外，水溶性有机氮（WSON）对总氮的贡献约为15％，并且观察到WSON的质量分数与OP _M正相关（R = 0.79），表明水溶性（WS）含氮有机物是高度DTT活跃。此外，OP _M还表现出与nss-K ⁺的显着相关性（R = 0.83），表明生物质燃烧排放物对气溶胶OP的影响。另外，WS-Mn，WS-Cu和WS-Zn的质量分数也与OP _M显着相关。。我们的结果还推断，气溶胶老化会增加其OP。这些结果对评估大陆气溶胶对海洋大气边界层和海洋生物地球化学的影响具有重要意义。