Total Carbon and Nitrogen Contents and Molecular Composition of Water Soluble Organic Matter in the Marine Aerosols from Western North to Tropical Central Pacific

Abstract

Marine aerosol samples collected from the western North to equatorial Pacific Ocean (16°S–35°N, 140°E–150°W), were studied for total carbon (TC: 0.069–5.27 μgm⁻³, ay. 0.39 μgm⁻³) and nitrogen (TN: 0.026–1.44 μgm⁻³, ay. 0.12 μgm⁻³) contents employing an elemental analyzer. Homologous series of dicarboxylic acids (C₂–C₁₀) and w-oxocarboxylic acids (C₂–C₉) in the aerosols were determined by capillary gas chromatography (GC) and GC/mass spectrometer (GC/MS). Their molecular distributions indicated a predominance of oxalic acid (C₂) and glyoxylic acid (C₂). The concentrations of total diacids and ω-oxoacids were 10–250 ngm ⁻³ (ay. 63 ngm⁻³) and 0.333.3 ngm⁻³ (ay. 3.4 ngm⁻³), respectively. The dicarboxylic acids showed a spatial distribution with higher concentrations in the western North Pacific region and lower concentrations in the central tropical Pacific. Relative abundances of total diacid carbon in TC, however, were highest (up to 16%) in the central equatorial Pacific, suggesting that small diacids are secondarily produced in the remote marine atmosphere. Further, ω-oxoacids were also abundant in the western North and tropical Pacific. In the remote marine atmosphere, oxalic acid and glyoxylic acid are likely produced by oxidative chain reactions occurring in the gaseous and particulate organic compounds which are transported long distances from the Asian continent.