Molecular characterization of marine organic aerosols collected during a round-the-world cruise

Organic molecular compositions of marine aerosol samples, collected at low latitudes to midlatitudes in the Northern Hemisphere during a round-the-world cruise, were studied using gas chromatography/mass spectrometry. More than 140 organic species were detected in the samples and were grouped into different compound classes based on the functionality and sources. The concentrations of total quantified organics ranged from 0.94 to 111 ng m(-3) (average of 34 ng m(-3)). Biogenic secondary organic aerosol (SOA) tracers from the oxidation of isoprene (e. g., 2-methyltetrols), alpha/beta-pinene (e. g., pinonic and pinic acids), and beta-caryophyllene (beta-caryophyllinic acid) were detected in all the samples. Their total concentrations ranged from 0.19 to 27 ng m(-3), which account for 0.48-29% of the total identified organics and 0.05-1.5% of organic carbon in the marine aerosols. The spatial distributions of biogenic SOA tracers exhibited higher loadings over the coastal/tropical regions than the open oceans. In marine aerosols collected over the North Pacific and North Atlantic, the contributions of marine natural emissions (22-33%) were higher than those in the coastal regions (4-14%). Over the tropical regions, atmospheric oxidation products can account for 47-59% of the total organics, with biomass burning emissions of only 1-2%. However, over the western North Pacific, fossil fuel combustion (26%), atmospheric oxidation products (25%), and biomass burning (24%) were the main sources. This study indicates that long-range atmospheric transport of continental aerosols and sea-to-air emission of marine organics, as well as atmospheric oxidation and/or photochemical aging, are important factors controlling the chemical composition of organic aerosols in the marine atmosphere.