Abstract

Human activities have increased the flux of lead (Pb) into the global environment by a factor of ten over natural fluxes. Close to home, Pb is a poison with no evidence of a threshold below which no harm occurs, and we have suffered from Pb pollution of the paint and plumbing in our houses, tin canned food, the fallout from leaded gasoline utilization and shockingly, even in children's plastic lunchboxes. In the remote environment, Pb is not a significant hazard because of the great levels of dilution, but nonetheless North Atlantic and Pacific surface water Pb and Pb isotope ratios during the past decades to centuries have undergone a systematic temporal variation due to changes in human
lead emission and sources. Some of these features in the temporal evolution are unique - some isotope ratios ofPb only exist for unique periods of time, allowing for an estimate of the time elapsed s41ce Pb was in the atmosphere and surface ocean. The most dramatic of these changes were those due to the dominance of Upper Mississippi Valley (UMV) Pb production in the mid-19th century United States. Pb in the deep eastern North Atlantic sank as NADW 80 years ago. It is possible that the lead that sank 150 years ago (from UMV Pb) will be identifiable in the South Atlantic Ocean.

Light refreshments are served in the Interaction Area (4th floor of the Oceanography/Physics Building) at 4:00 p.m.

All seminars begin at 3:00 p.m. and are held in room 200 of the Oceanography/Physics building.