Fatty acids in the marine atmosphere: Factors governing their concentrations and evaluation of organic films on sea-salt particles

Fatty acids (C-14-C-32) in the marine boundary layer were measured in aerosols that were collected over the northern North Pacific from October 1996 to June 1997. Concentrations of lower molecular weight (C-14-C-19) saturated fatty acids (LFAs, 0.8-24 ng m(-3)) showed a positive correlation with sea-salt concentrations, suggesting that LFAs are released from the ocean surface to the atmosphere with sea-salt particles. The averaged ratios of [LFAs](air)/[ sea salt] in autumn, winter, spring and summer seasons were 1.8 (+/-1.3)x10(-4), 2.1 (+/-1.3)x10(-4), 3.7 (+/-2.9)x10(-4), and 4.6 (+/-1.8)x10(-4), respectively. The results indicate the seasonal variation of the sea-to-air flux of LFAs relative to that of sea salt with a maximum in spring to summer. The enhanced LFA flux was consistent with the satellite images of chlorophyll a over the northern North Pacific, which showed high biological productivity from spring to summer. On the basis of the ratios of [LFAs](air)/[sea salt], relative humidity, and modeled size distribution of sea-salt particles, the coverage of LFAs on sea-salt particles was estimated to range from 0.3 to 14%. This study suggests that the coverage of fatty acids, together with other film-forming materials, may have a significant effect on the physicochemical properties of aerosols, which may be affected by the high biological productivity in the high latitudinal ocean.