Lead Precipitation Fluxes at Tropical Oceanic Sites Determined From ^(210)Pb Measurements

Creators: Settle, D. M.; Patterson, C. C.; Turekian, K. K.; Cochran, J. K.

Abstract

Concentrations of lead, ^(210)Pb, and ^(210)Po were measured in rain selected for least influence by local sources of contamination at several tropical and subtropical islands (Enewetak; Pigeon Key, Florida; and American Samoa) and shipboard stations (near Bermuda and Tahiti). Ratios expressed as ng Pb/dpm ^(210)Pb in rain were 250–900 for Pigeon Key (assuming 12% adsorption for ^(210)Pb and no adsorption for lead), depending on whether the air masses containing the analyzed rain came from the Caribbean or from the continent, respectively; about 390 for the northern Sargasso Sea downwind from emissions of industrial lead in North America; 65 for Enewetak, remote from continental emissions of industrial lead in the northern hemisphere; and 14 near Tahiti, a remote location in the southern hemisphere where industrial lead emissions to the atmosphere are much less than in the northern hemisphere. (The American Samoa sample yielded a higher ratio than Tahiti; the reason for this is not clear but may be due to local Pb sources.) The corresponding fluxes of lead to the oceans, based on measured or modeled ^(210)Pb precipitation fluxes, are about 4 ng Pb/cm^2y for Tahiti, 10 for Enewetak, and 270 for the Sargasso Sea site, and between 110 to 390 at Pigeon Key.

Additional Information

© 1982 by the American Geophysical Union. Received June 15, 1981; revised September 14, 1981; accepted September 15, 1981. Paper number 1C1463. We are indebted to the University of Miami, Florida, for provision of facilities at their Florida Keys Environmental Field Station at Pigeon Key, to the University of Hawaii and their staff at the Mid-Pacific Marine Laboratory on Enewetak, and to the NOAA staff at the GMCC Laboratory on Tutuila for provision of facilities and assistance in sample collection, to R. Flegal and B. Schaule for collecting the shipboard rain sample near Tahiti, and to A. Ng for collection of the shipboard rain sample near Bermuda. This work was funded by NSF grant OCE 77-14520 and OCE 77-12847. California Institute of Technology contribution number 3690.

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