Abstract. The composition of organic compounds in marine aerosols and the relative contributions of primary and secondary organic compounds remain uncertain. We report results from a novel approach to characterize and quantify organic components of the marine aerosol. Size-segregated discrete aerosol filter samples were collected at sea in the North Atlantic from both ambient aerosol and artificially generated primary sea spray over four
cruises timed to capture the seasonal phytoplankton bloom dynamics. Samples were analyzed by Fourier transform infrared spectroscopy (FTIR), extracted
into water, and analyzed by offline thermal desorption chemical ionization
mass spectrometry (TDCIMS) and ion chromatography (IC). A positive matrix
factorization (PMF) analysis identified several characteristic aerosol
components in the TDCIMS mass spectra. Among these is a polysaccharide
factor representing about 10 %–30 % of the submicron organic aerosol mass. Aerosol polysaccharide : sodium mass ratios were consistently higher in ambient air than in the artificially generated sea spray, and we hypothesize
that this results from more rapid wet deposition of sodium-rich aerosol. An
unquantified recalcitrant factor of highly thermally stable organics
showed significant correlation with FTIR-measured alcohol groups,
consistently the main organic functional group associated with sea spray
aerosol. We hypothesize that this factor represents recalcitrant dissolved
organic matter (DOM) in seawater and that by extension alcohol functional
groups identified in marine aerosol may more typically represent
recalcitrant DOM rather than biogenic saccharide-like material, contrary to
inferences made in previous studies. The recalcitrant factor showed little
seasonal variability in its contribution to primary marine aerosol. The
relative contribution of polysaccharides was highest in late spring and
summer in the smallest particle size fraction characterized (<180 nm).