Important Source of Marine Secondary Organic Aerosol from Biogenic Amines

Relevant concentrations of dimethyl- and diethylammonium salts (DMA+ and DEA+) were measured in submicrometer marine aerosol collected over the North Atlantic during periods of high biological activity (HBA) in clean air masses (median concentration (minimum−maximum) = 26 (6−56) ng m−3). Much lower concentrations were measured during periods of low biological activity (LBA): 1 (<0.4−20) ng m−3 and when polluted air masses were advected to the sampling site: 2 (<0.2−24) ng m−3. DMA+ and DEA+ are the most abundant organic species, second only to MSA, detected in fine marine particles representing on average 11% of the secondary organic aerosol (SOA) fraction and a dominant part (35% on average) of the water-soluble organic nitrogen (WSON). Several observations support the hypothesis that DMA+ and DEA+ have a biogenic oceanic source and are produced through the reaction of gaseous amines with sulfuric acid or acidic sulfates. Moreover, the water-soluble fraction of nascent marine aerosol particles produced by bubble-bursting experiments carried out in parallel to ambient aerosol sampling over the open ocean showed WSON, DMA+, and DEA+ concentrations always below the detection limit, thus excluding an important primary sea spray source.