Plutonium isotopes in the environment: some existing problems and some new ocean results

Marine sediments, terrestrial soils and polar glaciers yield different average values for the 240Pu/239Pu ratio resulting from the introduction of the actinide to the environment from weapons tests. The average value of the ratio in two sea water profiles from the North Pacific Ocean is 0.23, which is similar to that calculated from Arctic and Antarctic glaciers but differs considerably from the soil-derived average of 0.18. With the exception of near-surface waters, the sea water values of the 240Pu/239Pu ratio were nearly invariant with depth indicating that plutonium has been homogenized in the water column for a time period of decades. This contrasts with the glacial strata where there were systematic changes in the ratio with time of deposition. (author)