Radiocesium in migratory aquatic game birds using contaminated U.S. Department of Energy reactor-cooling reservoirs: A long-term perspective

• Published in: Journal of environmental radioactivity 2017-05, Vol.171 (C), p.189-199
• Main Authors: Kennamer, Robert A., Oldenkamp, Ricki E., Leaphart, James C., King, Joshua D., Bryan, A. Lawrence, Beasley, James C.
• Format: Article
• Language: English
• Subjects: 137Cs; Animal Migration; Animals; Birds - metabolism; Cesium Radioisotopes - analysis; Cesium Radioisotopes - metabolism; Ecological half-life; Half-Life; Lentic ecosystems; Nuclear industry; Nuclear Reactors; Radiation Monitoring; USDOE Savannah River Site; Water Pollutants, Radioactive - analysis; Water Pollutants, Radioactive - metabolism; Wintering waterfowl
• ISSN: 0265-931X; 1879-1700
• DOI: 10.1016/j.jenvrad.2017.02.022

Low-level releases of radiocesium into former nuclear reactor cooling-reservoirs on the U.S. Department of Energy's Savannah River Site (SRS) in South Carolina, USA, dating primarily to the late 1950s and early 1960s, have allowed examination of long-term contaminant attenuation in biota occupying these habitats. Periodic collections of migratory game birds since the 1970s have documented 137Cs (radiocesium) activity concentrations in birds of SRS reservoirs, including mainly Par Pond and Pond B. In this study, during 2014 and 2015 we released wild-caught American coots (Fulica americana) and ring-necked ducks (Aythya collaris) onto Pond B. We made lethal collections of these same birds with residence times ranging from 32 to 173 days to examine radiocesium uptake and estimate the rate of natural attenuation. The two species achieved asymptotic whole-body activity concentrations of radiocesium at different times, with ring-necked ducks requiring almost three times longer than the 30–35 days needed by coots. We estimated ecological half-life (Te) for Pond B coots over a 28-yr period as 16.8 yr (95% CI = 12.9–24.2 yr). Pond B coot Te was nearly four times longer than Te for coots at nearby Par Pond where radiocesium bioavailability had been constrained for decades by pumping of potassium-enriched river water into that reservoir. Te could not be estimated from long-term data for radiocesium in Pond B diving ducks, including ring-necked ducks, likely because of high variability in residence times of ducks on Pond B. Our results highlight the importance: (1) for risk managers to understand site-specific bio-geochemistry of radiocesium for successful implementation of countermeasures at contaminated sites and (2) of residence time as a critical determinant of observed radiocesium activity concentrations in highly mobile wildlife inhabiting contaminated habitats. •Pond B137Cs ecological half-life (Te) for migrant American coots was 16.8 yr.•Pond B biota Te was about four times longer than Te for biota at nearby Par Pond.•Pumping potassium-enriched water into Par Pond constrained 137Cs bioavailability.•Positive mitigation relies on understanding 137Cs bio-geochemistry in environment.•Residence time is a critical determinant of 137Cs levels in highly mobile wildlife.