Source Document: The Relationship Between Pocket Gophers (Thomomys bottae) and the Distribution of Buried Radioactive Waste at the Los Alamos National Laboratory

Abstract

Material Disposal Area G at the Los Alamos National Laboratory is a lowlevel radioactive waste storage facility. The noticeable presence of pocket gopher mounds and cast soil on closed waste burial sites of various types resulted in the need to understand possible interactions between gophers and radioactive waste at Area G. In our study, pocket gophers, mound soil, off-mound surface soil, and vegetation were collected at Area G and at off-site background locations. The samples were analyzed for 241 Am, 238 Pu, 239 Pu, 3 H, and total U. A comparison of radionuclide concentrations in mound soil to surface soil and in gophers to soil and vegetation implied that gopher activity is generally not resulting in the upward transport of radionuclides. Concentrations of 241 Am, 238 Pu, 239 Pu, and 3 H in some of the gopher, soil, and vegetation samples were higher than background at some of the sites, however, gophers at only one site within Area G had 3 H concentrations that resulted in an estimated dose to gophers that could impact their health. Relationships in radionuclide concentrations between the four media (pocket gophers, mound soil, off-mound surface soil, and vegetation) were examined by conducting correlation tests. Correlations were highest for Am 241 and 238 Pu, however, only the 238 Pu relationship may be accurate enough to be used in predicting concentrations. The relationship in radionuclide concentration between pelts and carcasses was highly variable-carcasses, including the gastrointestinal tract, contained between 51% and 575% of the radionuclide concentration on pelts. Data generated by this study are valuable for ecological risk assessments. Further investigation through modeling and monitoring may be necessary to determine if the 3 H shafts are a source of environmental 3 H levels that are of ecological concern. Future research should include modeling the transport of radionuclides through ecological receptors within and around Area G. This should include investigations of transfer to high-level carnivores, especially raptors. w3z-tGp-0~6 w-i fWw I!os Wd t 12 B85 t 'L 1 J~4uJOOOa 'hpsmy~. This report has been reproduced directly from the best available copy. It is available electronically on the Web (httn:l/www.doe.govlbridge).

Wildlife ecological screening levels for inhalation of volatile organic chemicals

“…The general inhalation ESL model used for burrowing mammals was modified from Carlsen [1] and is ESL ϭ (BW·TRV/IR)·OF (1) where ESL is the ecological screening level (mg/m 3 ); BW is the ecological receptor body weight (kg); TRV is the VOC toxicity reference value (mg/kg/d); IR is the ecological receptor inhalation rate (m 3 /d); OF is the occupancy factor, the fraction of time the ecological receptor spends in the burrow (unitless). Several conservative exposure assumptions were used in calculating ESLs, such as the use of the lowest adult body weight [12] for the ecological receptor to result in a maximum weight-adjusted inhalation rate, as well as use of the maximum body weight in TRV derivation to yield the lowest TRV. In addition, an occupancy factor of 1 for the ecological receptor is used to represent 100% occupancy, or all of its time in the burrow, for maximum exposure time.…”

The Uptake and Distribution of Buried Radionuclides by Pocket Gophers (Thomomys bottae)

“…[11] Two types of soil samples were collected at each study site, including at the reference sites. [11] Two types of soil samples were collected at each study site, including at the reference sites.…”

“…The pocket gophers occupying the area within the study site were identified as Thomomys bottae, or western pocket gopher. [11] MATERIALS AND METHODS The burrow system of pocket gophers usually consists of a relatively shallow main tunnel with many branching side tunnels that are used for foraging, and a deeper tunnel system.…”

Estimating Radiological Doses to Predators Foraging in a Low-Level Radioactive Waste Management Area

“…In recent years, there has been an increased interest in estimating doses to non-human biota that arise from radiological releases into the environment to evaluate the impacts to environmental resources (Gonzales et al 2000, Ferenbaugh et al 2002. The Laboratory, in 1998, developed an ecological risk assessment model for application to evaluating radiological doses in LANL's corrective action program (Environmental Restoration Project 1999).…”

“…In addition, transuranic wastes have been stored on pads in the northeast portion of the site. As part of the Laboratory's Environmental Surveillance Program, the Ecology Group has sampled media at Area G, including soils/sediments (Fresquez et al , 1999Nyhan et al 2000Nyhan et al , 2001, vegetation (Fresquez et al , 1999Nyhan et al 2000Nyhan et al , 2001, and small mammals (Biggs et al , 1997 Area G Gonzales et al 2000). These sampling and analytical activities have revealed elevated levels of several radionuclides in these media.…”