Lipids in aerosols from the tropical North Pacific: Temporal variability

Lipid components in air masses were sampled during 1979 at Enewetak Atoll as part of the Sea‐Air Exchange Program (SEAREX). The investigation was designed to determine the terrestrial and marine sources and to search for atmospheric transformation processes of oceanic aerosols. Four particulate lipid compound classes (aliphatic hydrocarbons, fatty alcohols, fatty acid esters, and salts) all unequivocally show a terrestrial vascular plant source. Their temporal trends correlate well with those of other continental source indicators, such as particulate Al and 210 Pb. These particulate lipids originate from wind erosion of Eurasian soil and direct emission from vegetation rather than from biomass burning, anthropogenic sources, or evaporation/condensation processes. A series of apparently marine‐derived lower molecular weight alcohols and fatty acid salts and esters are also present. The more typically marine polyunsaturated acids are absent, probably due to their rapid rates of atmospheric degradation. A marine origin for the fatty acid salts <C 20 would require marine aerosols to be enriched ca. 300‐fold over the levels found in surface seawater samples. Although particulate total organic carbon data imply major influences of atmospheric transformations on the atmospheric particulate material, these effects are not observed in the lipid class compound distributions.