Fractionation of the elements F, Cl, Na, and K at the sea-air interface

The sea-air interface ion fractionation of F, Cl, Na, and K was studied in the field and the laboratory. Laboratory results show negative enrichment of fluoride and chloride versus Na and a positive enrichment of K. The same results were found in samples that were collected under ‘true marine’ conditions. From these results we propose the fractionation in a true marine sea salt aerosol to be F = −0.62, Cl = +0.12, and K = +0.40 normalized to Na. The chemistry of marine precipitation is quite different from these values and approaches more the chemistry of the tropospheric background aerosol or of a continental aerosol with the exception of chloride values.