A Pb isotope record of mid-Atlantic US atmospheric Pb emissions in Chesapeake Bay sediments

Abstract

We have analyzed sediments from three sites in the mesohaline portion of Chesapeake Bay (CB) for Pb isotopes. The well-preserved and well-dated sediments provide an excellent opportunity to compare the anthropogenic Pb isotope record in CB to other Pb isotope records of US industrial atmospheric emissions . Over the past century, there is excellent temporal agreement between anthropogenic CB 206 Pb/ 207 Pb isotope ratios and those determined in a dated coral from Bermuda [Earth and Planetary Science Letters, 82 (1987) 289] almost 2000 km away. We use this correlation to argue that CB sediments contain a regional, industrial atmospheric Pb isotope signal that is representative of the mid-Atlantic region of the US. Anthropogenic Pb is found in sediments deposited as early as approximately 1800. From about 1800 to 1930, the Pb signal in the CB sediments is probably derived from the burning of coal. After this period, and up until about the 1980s, the signal is overwhelmed by the Pb derived from the combustion of gasoline.