Inventories and sorption-desorption trends of radiocesium and radiocobalt in James River estuary sediments

Anthropogenic radionuclides (Cs137, Cs134, Co60) have been introduced to the James River estuary as a result of low-level releases from the Surry Reactor site since 1973 and worldwide atmospheric fallout from nuclear weapons tests since the early 1950s. The total radionuclide burden in the estuary sediments has been estimated by integrating radionuclide activities in 29 box cores and extrapolating these integrated values over surface areas subdivided on the basis of sediment type, rate of accumulation, and proximity to the reactor release site. The results indicate that 30% of the Co60, but only 15% of the Cs134 released from the reactor site, has been retained in the estuary sediments, and about 40% of the Cs134 and Co60 sediment inventory is in areas that represent less than 5% of the total estuarine surface area. Depletion of the Cs134 in downstream sediments forms a noticeable trend in the James River estuary, and it is postulated that seawater cation competition and exchange is primarily responsible. 26 references, 1 figure, 4 tables