Time pattern of off-site plutonium deposition from rocky flats plant by lake sediment analyses

A sediment core from a lake downwind of the Rocky Flats Plant, where nuclear weapons components are produced, was used to reconstruct a time pattern of off-site plutonium deposition. Core sections were dated by analyses of 137Cs, 239,240Pu, 238Pu, and 241Am fallout from nuclear testing and 238Pu fallout from a satellite failure. A peak in transuranic concentrations occurred in late 1969 which was attributable to the Plant. This was confirmed by mass isotopic analysis of plutonium isotopes in selected core segments where the global fallout and Plant contributions could be differentiated. The 18 nCi 239,240Pu per m 2 from the Plant that had accumulated in the sediment is reasonable when compared to soil analyses.