Seasonal variation in the elimination rate constants of two radionuclides was examined in the yellow-bellied slider (Pseudemys scripta). Thirty-six turtles from waste ponds contaminated with cesium-137 and strontium-90 were placed in an uncontaminated 18 × 20 m experimental pond and fed ad libitum weekly. Total body burdens of the radionuclides were measured five times at approximately 2-month intervals. These data were used to determine seasonal and overall elimination rate constants. Elimination rate constants differed between radionuclides and among seasons. Seasonal rate constants ranged from 0.002 to 0.029 day−1 for 137Cs, and from < 0.001 to 0.006 day−1 for 90Sr. Rate constants were highest, and presumably metabolic activity was greatest, in late April through June. This period corresponds to the spring breeding season in P. scripta. The overall biological half-lives of cesium-137 and strontium-90 were 64 and 365 days, respectively.
