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 abundantorganic 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.

An anion-exchange high-performance liquid chromatography method coupled to total organic carbon determination for the analysis of water-soluble organic aerosols

The chemical composition of water-soluble organic carbon (WSOC) in atmospheric aerosol particles is largely unexplored, due to the myriad of individual compounds, which has hampered attempts to attain a full characterization at the molecular level. An alternative approach, focusing on the analysis of a few main chemical classes, allowed the quantitative fractionation of WSOC into neutral compounds (NC), mono- and di-acids (MDA) and polyacids (PA) through an anion-exchange liquid chromatographic method. Previous attempts to quantify NC, MDA and PA relied on a low-pressure chromatographic technique using a volatile buffer, followed by total organic carbon (TOC) analysis of the fractions, or alternatively on a faster HPLC-UV method which provided a quantification of the fractions based on empirical relationships between UV signal and TOC concentration. Here, we report an upgraded anion-exchange HPLC technique, allowing direct TOC analysis of the eluted fractions, without any pre-treatment, thus permitting a great simplification of quantitative analysis and preventing sample losses. The new HPLC-TOC methodology, employing completely inorganic eluents shows the same efficiency of the former HPLC-UV method employing organic additives, with the exception of phenolic compounds, which are retained on the column by secondary interactions, and low-molecular weight tricarboxylic acids, which are recovered among MDA. The new anion-exchange liquid chromatographic method can recover a substantial amount (86-100%) of water-soluble organic carbon from atmospheric aerosol extracts, thus allowing a higher retention and fractionation capacity with respect to alternative techniques, like solid phase extraction.