Low molecular weight dicarboxylic acids and related polar compounds in the remote marine rain samples collected from Western Pacific

Richard Sempere (1, 2) , Kawamura Kimitaka (2)

1 MIO - Institut méditerranéen d'océanologie
2 TMU - Tokyo Metropolitan University [Tokyo]

During the western Pacific Ocean cruise of R/V Hakuho-Maru (20°N-40°S), fourteen rainwater samples were collected. They were studied by a capillary gas chromatography (GC) and GC-mass spectrometry (GC/MS) for the molecular distributions of C2C10 α, ω-dicarboxylic acids and related polar compounds, i.e. ketoacids (C2C9) and α-dicarbonyls (C2C3). Samples were also analysed for dissolved (DOC) and total organic carbon (TOC). Total diacid concentration range was 36−959 μg−1 and accounted for 3% (av.) of TOC (1.2−2.5 mgC−1), which is much higher than the previous numbers found in Tokyo rain samples (av. 1 %). This indicates that low molecular weight dicarboxylic acids are an important class of organic compounds in the marine rains. All the samples showed that the smallest diacid (oxalic acid) which comprised 50% of the total diacids was the most abundant followed by malonic (C3) or succinic acid (C4). The shorter chain diacids (C2C4) accounted for 63–90% (av. 80%) of total diacids and their relative abundances increase from the Northern to the Southern Hemisphere. These results suggest that shorter chain diacids are in part produced in the marine atmosphere by photochemical oxidation of organic matter through the intermediates such as ketoacids and dicarbonyls. The major portion of diacids and their precursors is probably derived from the Asian and Australian continents by a long-range transport.

Mots clés: Pacific ocean; Pacific atmosphere; DOC; αω-dicarboxylic acids; α-dicarbonyls; Dicarbonyls; rainwaters

Domaines: Océan, Atmosphère

Richard Sempere, Kawamura Kimitaka. Low molecular weight dicarboxylic acids and related polar compounds in the remote marine rain samples collected from Western Pacific. Atmospheric environment, 1996, 30 (10-11), pp.1609-1619. ⟨10.1016/1352-2310(95)00436-X⟩. ⟨hal-01171595⟩