Effect of anaerobiosis on the geochemical cycling of plutonium in PAR Pond

Most of the fallout plutonium in Lake Michigan sediments is found associated with hydrous oxides which are significantly solubilized only under reducing conditions. As most of the sediments of Lake Michigan remain aerobic all year long, the possibility of resolubilization of these oxides and reintroduction of the associated plutonium into the overlying water through this mechanism is small. However, in some water bodies, such as PAR Pond, South Carolina, anaerobic sedimentary conditions do prevail for a portion of the year. PAR Pond was studied to determine if the seasonal anaerobic conditions in the sediments lead to a measurable increase in the plutonium concentration of the overlying water. The data indicated that there was a slight increase in the 239240Pu concentration near the bottom as compared to the rest of the water column in the July 1975 and August 1976 samples. However, no significant increase in 239240Pu concentration was observed in the hypolimnetic waters of the pond which could be related to the anaerobic conditions of the sediment and deep waters during the summer months