Collected reprints: Abstract 3507
Collected reprints
Abstract
Van Grieken, R.E.; Johansson, T.B.; Winchester, J.W. (1974). Trace metal fractionation effects between sea water and aerosols from bubble bursting. J. Rech. Atmosphériques 1974: 611-621
Laboratory experiments were performed using radioactive tracers of 65Zn, 75Se, 22Na, 137Cs and 152Eu added to natural sea water to determine differences in elemental composition between sea water and aerosol droplets as a function of particle size. The experiments were conducted using a flow of air as a stream of bubbles rising and bursting at the surface of a vessel containing sea water with added radioactive tracers at pH 8. The resultant aerosol cloud was drawn through a cascade impactor which separated particle size fractions for analysis. In a typical experiment 30 ml of sea water, collected in polyethylene no more than a few hours before along a sandy Gulf of Mexico beach, and a stream of clean air, giving bubbles with a rise distance through the water of 1 to 10 cm, were used, and two or more sequential samplings, usually 12 to 24 hours in duration, were made by cascade impactor. The impaction surfaces were then counted by gamma ray spectrometer.
Enrichments relative to Na in general vary systematically with particle size and may exceed a factor of 10 but appear to depend on the particular conditions of each experiment, such as the rise distance of the bubbles and the equilibration time between the added tracers and natural constituents in sea water. Fractionation effects, often quite large, appear to be the rule rather than the exception. Consequently, effects transfer of pollutants from water to air is a distinct possibility and should be documented for each substance of interest under varying conditions. At the very least, our results indicate that in the absence of data it is unwise to assume the composition of the marine aerosol, even as a first approximation, to be the same as sea water.
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