Sub-Antarctic marine aerosol: Dominant contributions from biogenic sources
Biogenic influences on the composition and char-acteristics of aerosol were investigated on Bird Island (54 • 00 S, 38 • 03 W) in the South Atlantic during Novem-ber and December 2010. This remote marine environment is characterised by large seabird and seal colonies. The chem-ical composition of the submicron particles, measured by an aerosol mass spectrometer (AMS), was 21 % non-sea-salt sulfate, 2 % nitrate, 8 % ammonium, 22 % organics and 47 % sea salt including sea salt sulfate. A new method to isolate the sea spray signature from the high-resolution AMS data was applied. Generally, the aerosol was found to be less acidic than in other marine environments due to the high availabil-ity of ammonia, from local fauna emissions. By positive ma-trix factorisation five different organic aerosol (OA) profiles could be isolated: an amino acid/amine factor (AA-OA, 18 % of OA mass), a methanesulfonic acid OA factor (MSA-OA, 25 %), a marine oxygenated OA factor (M-OOA, 41 %), a sea spray OA fraction (SS-OA, 7 %) and locally produced hydrocarbon-like OA (HOA, 9 %). The AA-OA was domi-nant during the first two weeks of November and found to be related with the hatching of penguins in a nearby colony. This factor, rich in nitrogen (N : C ratio = 0.13), has implications for the biogeochemical cycling of nitrogen in the area as par-ticulate matter is often transported over longer distances than gaseous N-rich compounds. The MSA-OA was mainly trans-ported from more southerly latitudes where phytoplankton bloomed. The bloom was identified as one of three sources for particulate sulfate on Bird Island, next to sea salt sulfate and sulfate transported from South America. M-OOA was the dominant organic factor and found to be similar to ma-rine OA observed at Mace Head, Ireland. An additional OA factor highly correlated with sea spray aerosol was identified (SS-OA). However, based on the available data the type of mixture, internal or external, could not be determined. Potas-sium was not associated with sea salt particles during 19 % of the time, indicating the presence of biogenic particles in addition to the MSA-OA and AA-OA factors.