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Size-segregated aerosols (nine stages from &lt; 0.43 to &gt; 11.3 µm in diameter) were collected at Cape Hedo, Okinawa, in spring 2008 and analyzed for water-soluble diacids (C₂–C₁₂), <i>ω</i>-oxoacids (<i>ω</i>C₂–<i>ω</i>C₉), pyruvic acid, benzoic acid, and <i>α</i>-dicarbonyls (C₂–C₃) as well as water-soluble organic carbon (WSOC), organic carbon (OC), and major ions (Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺, Cl⁻, NO₃⁻, SO₄²⁻, and MSA⁻). In all the size-segregated aerosols, oxalic acid (C₂) was found to be the most abundant species, followed by malonic and succinic acids, whereas glyoxylic acid (<i>ω</i>C₂) was the dominant oxoacid and glyoxal (Gly) was more abundant than methylglyoxal. Diacids (C₂–C₅), <i>ω</i>C₂, and Gly as well as WSOC and OC peaked at fine mode (0.65–1.1 µm) whereas azelaic (C₉) and 9-oxononanoic (<i>ω</i>C₉) acids peaked at coarse mode (3.3–4.7 µm). Sulfate and ammonium were enriched in fine mode, whereas sodium and chloride were in coarse mode. Strong correlations of C₂–C₅ diacids, <i>ω</i>C₂ and Gly with sulfate were observed in fine mode (<i>r</i> =  0.86–0.99), indicating a commonality in their secondary formation. Their significant correlations with liquid water content in fine mode (<i>r</i> =  0.82–0.95) further suggest an importance of the aqueous-phase production in Okinawa aerosols. They may also have been directly emitted from biomass burning in fine mode as supported by strong correlations with potassium (<i>r</i> =  0.85–0.96), which is a tracer of biomass burning. Bimodal size distributions of longer-chain diacid (C₉) and oxoacid (<i>ω</i>C₉) with a major peak in the coarse mode suggest that they were emitted from the sea surface microlayers and/or produced by heterogeneous oxidation of biogenic unsaturated fatty acids on sea salt particles.