Radioactive and stable trace metals in Narragansett Bay, Rhode Island

Experiments designed to determine the removal rates and mechanisms of various radioactive trace metals from the water of Narragansett Bay were performed in the spring and early summer in 150-liter microcosms simulating the bay. Overall removal rates were first order for all elements studied in the spring (54Mn, 58Co, 59Fe, 65Zn, /sup 115m/Cd) and most elements studied in the summer (58Co, 65Zn, 59Fe, 134Cs, 210Po, 228Th). For those elements studied in both seasons, removal was slower in the summer than in the spring. During the summer experiment 54Mn, 51Cr, and 75Se showed rapid first order removal in the initial 1 to 2 weeks followed by much slower removal. The seasonal differences appear to be the result of the association of the metals with low molecular weight organic compounds present only during the summer. Mass balance shows that the major removal reservoirs during the spring were the tank walls, suspended sediment, and the upper layers of the sediment. The seasonal behavior of the metals in the tanks was qualitatively similar to that of some radionuclides and stable metals studied in the bay