Low molecular weight dicarboxylic acids constituting a pivotal fraction of organic aerosols impact radiative forcing of Earth's atmosphere. However, a significant knowledge gap exists associated with their sources and formation pathways in the atmosphere. In this study, we report on water-soluble components such as dicarboxylic acids, oxoacids, and α-dicarbonyls as well as carbonaceous and ionic components in the continental outflow from the South Asian region to the Arabian Sea and the equatorial Indian Ocean during ICARB (Integrated Campaign for Aerosols, gases and Radiation Budget) 2018 experiment. Non-sea-salt sulfate (nss SO₄²⁻) was found to be the predominant component, followed by ammonium (NH₄⁺) and organic carbon (OC) in fine-sized (<1.1 μm) aerosols. Total diacids carbon content accounted for 17% (on average) of total carbon (TC). Oxalic acid (C₂) was the most abundant organic acid, contributing ~41% to total diacids, followed by terephthalic acid (tPh) and succinic acid (C₄). Of these results, together with selected organic and inorganic mass ratios and linear relationships among the organic acids, we highlight the sources of organic acids over Indian Ocean. Over continental outflow regions in Indian Ocean, di-carboxylic acids are majorly derived from the emissions of biomass burning and combustion related sources, that underwent transformation in the atmosphere through photochemical reactions during the long range transport. However, over the deep oceanic environment of Indian Ocean, photo-oxidation of biogenic unsaturated fatty acids were found to be the important sources. The findings from this study will be helpful to improve further our understanding of the sources and formation processes of organic aerosols and their climate effects over the South Asian outflow regions.

构成有机气溶胶关键部分的低分子量二羧酸会影响地球大气的辐射强迫。然而，与它们在大气中的来源和形成途径相关的知识差距存在很大。在这项研究中，我们报告了 ICARB 期间从南亚地区到阿拉伯海和赤道印度洋的大陆流出物中的水溶性成分，如二羧酸、含氧酸和 α-二羰基化合物以及碳质和离子成分。气溶胶、气体和辐射预算综合运动）2018 年实验。发现非海盐硫酸盐 (nss SO ₄ ²⁻ ) 是主要成分，其次是铵 (NH ₄ ⁺) 和细粒度 (<1.1 μm) 气溶胶中的有机碳 (OC)。总二酸碳含量占总碳 (TC) 的 17%（平均）。草酸 (C ₂ ) 是最丰富的有机酸，占总二酸的约 41%，其次是对苯二甲酸 (tPh) 和琥珀酸 (C ₄）。在这些结果中，连同选定的有机和无机质量比以及有机酸之间的线性关系，我们强调了印度洋上有机酸的来源。在印度洋大陆流出区域，二元羧酸主要来自生物质燃烧和燃烧相关来源的排放，它们在长距离传输过程中通过光化学反应在大气中发生转化。然而，在印度洋深海环境中，生物不饱和脂肪酸的光氧化被发现是重要的来源。这项研究的结果将有助于进一步提高我们对有机气溶胶的来源和形成过程及其对南亚流出区域的气候影响的理解。