Marine organic aerosol and biological oceanic activity

Marine aerosol constitutes one of the most important natural aerosol systems at the global level and comprises both organic and inorganic components of primary and secondary origin. This work presents new results on organic marine aerosol properties and its link with oceanic biological productivity. Laboratory experiments have shown that sea-spray aerosol originating from highly biologically active sea water has a significant organic fraction, which increases with decreasing particle size, up to 77±5% below 0.25 μm diameter. Submicron sea-spray organic matter is mainly water-insoluble and composed of phytoplankton exudates (mainly lipo-polysaccharides). With regard to secondary organic aerosols, new components have been detected: dimethyl and diethyl amine salts turned out to be the most abundant organic species, alongside methanesulphonic acid, in fine marine particles over the North Atlantic. Clear evidence of a marine biological origin for dimethyl and diethyl amine salts has been observed, pointing to a new atmospheric organic nitrogen global source, with a seasonality connected to oceanic biological productivity and an atmospheric cycle parallel to that of the organosulphur species.