Evolution of Anthropogenic Pb and Pb isotopes in the Deep North Atlantic Ocean and the Indian Ocean

Jong-Mi Lee, Ph.D., 2013
Ed Boyle, Advisor

This study presents how anthropogenic Pb inputs have changed Pb and Pb isotopes in the deep North Atlantic Ocean and the Indian Ocean. First, a method was developed for the analysis of dissolved Pb and other trace elements in seawater using single batch nitrilotriacetate resin extraction and isotope dilution ICP-MS. Second, a ~550 year history of the Pb and Pb isotopes in the deep North Atlantic Ocean is reconstructed using a deep-sea coral, showing the penetration of anthropogenic Pb to deep sea. Then, time scales of the Pb penetration are estimated by comparing the results to the history of anthropogenic Pb inputs to the surface North Atlantic Ocean. Third, ~50 year changes of the Pb and Pb isotopes in the surface Indian Ocean are reconstructed from surface growing corals. Results show the increase of Pb concentrations from the mid-1970s, and major sources of the Pb, including leaded gasoline and coal burning, are discussed. Lastly, Pb and Pb isotopes are measured from the Indian Ocean water column. Higher Pb concentrations and lower Pb isotope ratios (²⁰⁶Pb/²⁰⁷Pb) are found in the upper layers (<1500m) due to anthropogenic Pb inputs, and the study also shows the importance of hydrography in determining the distributions of Pb in the Indian Ocean.