The Distribution of Lead Between Sea Salt, Dust, and Lead-Rich Aerosols in the Mid South Pacific Easterlies at American Samoa

Aerosols in the South Pacific Easterlies have been sampled at American Samoa with a cascade impactor and analysed for Pb, Ba, K, Ca, Sr, and Rb by isotope dilution mass spectrometry using ultraclean procedures. Some 84% of the Pb was found in fine (-<0.5/am) aerosols which were collected on the backup filter with an efficiency of only 33%. Sea salt and eroded terrestrial material (dust) containing 6% and < 1% respectively, of the Pb (sea salt indexed by the metals K, Ca, Sr, and Rb and dust indexed by Ba) were collected on early stages of the impactor, although 65% of the dust, because of its larger size, was lost to surfaces of the rain shelter before reaching the impactor. The remaining 10% of the Pb was associated with plant leaf waxes of continental origin which produced Pb and Ba peaks on stage 4 (0.5/am) of the impactor.