Mid-chain ketocarboxylic acids in the remote marine atmosphere: Distribution patterns and possible formation mechanisms

Abstract

In remote marine aerosol samples collected from the North Pacific ocean, Enewetak Atoll, American Samoa, and New Zealand, series of mid-chain ketocarboxylic acids in the range of C 6-C1s were detected. All the positional isomers, except for the 2-oxo and 3-oxo species, were detected for major ketoaeid families (e.g. C 9 , C H and C13 ). Higher ketoacid concentrations (up to 19 ng/m 3 ) were obtained in the northern North Pacific aerosol samples, which generally showed an odd carbon-numbered predominance with 5-oxoundecanoic acid being the major species. By contrast, lower concentrations were obtained in the lower-latitude or subtropical aerosol samples, where even carbon-numbered ketoacids were relatively abundant.The distribution patterns of the odd carbon-numbered ketoacids could not be explained by the primary emissions from source materials including terrestrial higher plants, soil particles, and ocean surfaces. We consider that the isomeric ketoearboxylic acids are produced in the atmosphere by the photochemical oxidation of semi-volatile monocarboxylic acids, which are counterparts of the oxidative degradation of unsaturated fatty acids emitted from seawater surfaces. Atmospheric production of the ketoacids is seemingly enhanced in the northern North Pacific, probably due to an enhanced primary productivity.

Molecular distributions of water soluble dicarboxylic acids in marine aerosols over the Pacific Ocean including tropics

“…These two components account for 90% of the variance in the data sets, with 52% accounted for by the first component and 38% accounted for by the second component. The results in Table 2 suggest that the diacid distributions can be explained by a 100 , , , i , , , I , , , i , , , i , [Kawamura and Gagosian, 1990]. They are produced in the marine atmosphere by photochemical oxidation of semivolatile fatty acids which are counterpart of oxidative degradation of unsaturated fatty acids (see Figure 8a).…”

Molecular distributions of dicarboxylic acids, ketocarboxylic acids and α-dicarbonyls in biomass burning aerosols: implications for photochemical production and degradation in smoke layers

“…Strong anti-correlations between the relative abundance of oxalic acid to total n-saturated dicarboxylic acids (C 2 -C 10 ) and some high carbon number dicarboxylic acids [methylmalonic (iC 4 ), maleic (M), methylmaleic (mM), methylsuccinic (iC 5 ), adipic (C 6 ) and phthalic (Ph)], ketocarboxylic acids [glyoxylic (ωC 2 ) and pyruvic (Pyr)], and dicarbonyl [glyoxal (Gly)] have been reported in summer aerosols collected from urban Tokyo (Kawamura and Yasui, 2005). These authors also suggested that longer-chain (C 5 -C 10 ) dicarboxylic acids were produced through the oxidation of semi-volatile fatty acids (Kawamura and Gagosian, 1990;Kawamura et al, 1996a), which are also the oxidation products of unsaturated fatty acids that are abundant in leaves of higher terrestrial plants and are also emitted from wood burning (Rogge et al, 1998).…”

Predicted hygroscopic growth of sea salt aerosol

“…The concentrations of 49 organic compounds in aerosol over the western Atlantic Ocean have been identified, and most of the species that were detected are long-chain insoluble species [Duce et al, 1983]. More polar substances, including dicarboxylic and ketocarboxylic acids, have also been identified in marine aerosol in the Pacific Ocean [Kawamura and Gagosian, 1990]. $axena and Hildemann [1996] postulate that a significant part of the unidentified organic aerosol mass consists of watersoluble polar species.…”