Abstract. The concentrations of submicron aerosol particles in maritime regions around
Antarctica are influenced by the extent of sea ice. This effect is two ways:
on one side, sea ice regulates the production of particles by sea spray
(primary aerosols); on the other side, it hosts complex communities of
organisms emitting precursors for secondary particles. Past studies
documenting the chemical composition of fine aerosols in Antarctica indicate
various potential primary and secondary sources active in coastal areas, in
offshore marine regions, and in the sea ice itself. In particular,
beside the well-known sources of organic and sulfur material originating
from the oxidation of dimethylsulfide (DMS) produced by microalgae, recent
findings obtained during the 2015 PEGASO cruise suggest that
nitrogen-containing organic compounds are also produced by the microbiota
colonizing the marginal ice zone. To complement the aerosol source
apportionment performed using online mass spectrometric techniques, here we
discuss the outcomes of offline spectroscopic analysis performed by nuclear
magnetic resonance (NMR) spectroscopy. In this study we (i) present the
composition of ambient aerosols over open-ocean waters across bioregions,
and compare it to the composition of (ii) seawater samples and (iii) bubble-bursting aerosols produced in a sea-spray chamber onboard the ship. Our
results show that the process of aerosolization in the tank enriches primary
marine particles with lipids and sugars while depleting them of free
amino acids, providing an explanation for why amino acids occurred only at
trace concentrations in the marine aerosol samples analyzed. The analysis of
water-soluble organic carbon (WSOC) in ambient submicron aerosol samples
shows distinct NMR fingerprints for three bioregions: (1) the open Southern
Ocean pelagic environments, in which aerosols are enriched with primary
marine particles containing lipids and sugars; (2) sympagic areas in the
Weddell Sea, where secondary organic compounds, including methanesulfonic
acid and semivolatile amines abound in the aerosol composition; and (3)
terrestrial coastal areas, traced by sugars such as sucrose, emitted by land
vegetation. Finally, a new biogenic chemical marker, creatinine, was
identified in the samples from the Weddell Sea, providing another
confirmation of the importance of nitrogen-containing metabolites in
Antarctic polar aerosols.