Contaminant monitoring of biota downstream of a radioactive liquid waste treatment facility, Los Alamos National Laboratory

Small mammals, plants, and sediments were sampled at one upstream location (Site 1) and two downstream locations (Site 2 and Site 3) from the National Pollution Discharge Elimination System (NPDES) outfall number-sign 051-051 in Mortandad Canyon, Los Alamos National Laboratory, Los Alamos, New Mexico. The purpose of the sampling was to identify radionuclides potentially present, to quantitatively estimate and compare the amount of radionuclide uptake at specific locations (Site 2 and Site 3) within Mortandad Canyon to an upstream site (Site 1), and to identify the primary mode (inhalation/ingestion or surface contact) of contamination to small mammals. Three composite samples of at least five animals per sample were collected at each site. The pelt was separated from the carcass of each animal and both were analyzed independently. In addition, three composite samples were also collected for plants and sediments at each site. Samples were analyzed for americium (241Am), strontium (90Sr), plutonium (238Pu and 239Pu), and total uranium (U). With the exception of total U, all mean radionuclide concentrations in small mammal carcasses and sediments were significantly higher at Site 2 than Site 1 or Site 3. No differences were detected in the mean radionuclide concentration of plant samples between sites. However, some radionuclide concentrations found at all three sites were higher than regional background. No differences were found between mean carcass radionuclide concentrations and mean pelt radionuclide concentrations, indicating that the two primary modes of contamination may be equally occurring