Stable isotopic ratios of lead in surface waters of the central Pacific

Abstract

The geographic variation in the isotopic composition of lead in surface waters of the central Pacific provides new evidence of the global anthropogenic perturbation of the element's cycle. Ratios of ^(206)Pb/^(207)Pb decrease from 1.196 in the northern hemisphere (19°N, 158°W) to 1.176 in the southern hemisphere (15°S, 150°W). This decrease parallels the geographic variation in surface concentrations of soluble lead which decrease from 13 ng kg^(−1) at the northern station to 4 ng kg^(−1) at the southern station. Both the ^(206)Pb/^(207)Pb and the 206Pb/208Pb ratios of those waters fit between the isotopic ratios of Australian (Broken Hill) and North American (Mississippi Valley) leads which are the predominant sources of leads in anthropogenic emissions to the Pacific Ocean basin