Water-soluble dicarboxylic acids, ketoacids and dicarbonyls in the atmospheric aerosols over the Southern Ocean and western Pacific Ocean

Water-soluble dicarboxylic acids (DCAs), ketoacids, and alpha-dicarbonyls in the marine aerosol samples collected over the Southern Ocean and western Pacific Ocean were determined. Oxalic acid was the most abundant species, followed by malonic acid and then succinic acid. It is suggested that aerosol concentrations of the organics over the Southern Ocean in this work represent their global background levels. Over the Southern Ocean, total concentrations of DCAs ranged from 2.9 to 7.2 ng m(-3) (average: 4.5 ng m(-3)), ketoacids from 0.14 to 0.40 ng m(-3) (av.: 0.28 ng m(-3)), and dicarbonyls from 0.06 to 0.29 ng m(-3) (av.: 0.11 ng m(-3)). Over the western Pacific, total concentrations of DCAs ranged from 1.7 to 170 ng m(-3) (av.: 60 ng m(-3)), ketoacids from 0.08 to 5.3 ng m(-3) (av.: 1.8 ng m(-3)), and dicarbonyls from 0.03 to 4.6 ng m(-3) (av.: 0.95 ng m(-3)). DCAs over the western Pacific have constituted a large fraction of organic aerosols with a mean DCAs-C/TC (total carbon) of 7.0% (range: 0.59-14%). Such a high value was in contrast to the low DCAs-C/TC (av.: 1.8%; range: 0.89-4.0%) for the Southern Ocean aerosols. Based on the relative abundances and latitudinal distributions of these organics, we propose that long-range atmospheric transport is more important over the western Pacific Ocean, in contrast, in situ photochemical production is more significant over the Southern Ocean although absolute concentrations of the organics are much lower.