Radionuclide export by deer mice at a solid radioactive waste disposal area in southeastern Idaho.
Concentrations of 90Sr, 137Cs, 238Pu, 239+240Pu, and 241Am in deer mice tissues collected from a radioactive waste disposal area in southeastern Idaho were significantly (p less than 0.05) higher than those from a control area. The highest concentrations of Pu and Am occurred in pelts of deer mice inhabiting an area which had elevated surface and subsurface soil concentrations of these nuclides as compared to other Subsurface Disposal Area locations. Therefore, transuranic contamination in tissues likely originated from both soil depths. However, 137Cs and 90Sr in tissues likely originated from subsurface areas, since surface soils were below background concentrations for these nuclides. Based on a minimum of 6160 deer mice inhabiting the 36-ha waste disposal area over a 1-yr period, a total minimum inventory of 22.8 mu Ci radioactivity was contained in deer mice tissues. Of this estimate, 22.7 mu Ci activity was due to the radionuclides 90Sr and 137Cs. An estimated total of 8.4 mu Ci was transported from the disposal area in mice dispersing from the area. A calculated annual radionuclide inventory of 28.8 mu Ci in deer mice feces was deposited in and around the radioactive waste disposal area. Deer mice inhabiting the SDA are a mode of radionuclide uptake and transport; however, the environmental consequences of this transport mechanism are likely minimal. The results for deer mice, which make up 69% of the small mammal biomass, are discussed in relation to other small mammals within the disposal area. Other modes of transport associated with the deer mice, such as radionuclides in excavated soils associated with burrowing activities and predation, are also discussed.
Radiation dose to small mammals inhabiting a solid radioactive waste disposal area
(1) Radiation dose rates received by deer mice (Peromyscus maniculatus (Wagner)) and Ord's kangaroo rats (Dipodomys ordii (Woodhouse) inhabiting a solid radioactive waste disposal area and a control area in south-eastern Idaho were determined by surgically implanting lithium-floride thermoluminescent dosimeter (TLD) packets. Fifty-three percent of the 542 and 135 TLD packets implanted in deer mice and kangaroo rats, respectively, were recovered. (2) The radiation dose rates received by animals from the radioactive waste disposal area varied from 4 to 418 000 gGy day-' (0-4-42 000 mrad day-') and were significantly (P < 0.01) higher than the dose rate of 4 gGy day-' (0-4 mrad day-') received by control animals. Doses resulted primarily from radiation from buried activation and fission products and not from radionuclides in/on tissues. (3) Ninety-six percent of the waste disposal area deer mice in the autumn-winter had radiation dose rates higher than the rates of the control animals, whereas in the spring-summer 73% of the deer mice received dose rates greater than the rates of control animals. Differences in seasonal data were probably related to increased subsurface time in autumn-winter. (4) Autumn-winter dose rates received by kangaroo rats were significantly (P < 0.05) higher than spring-summer rates and were attributed to the species entering torpor beneath the soil surface during winter. (5) Conservative comparisons between the radiation dose rates received by implanted TLD packets in individual small mammals and the potential dose rates received by individual animals on the surface of the area indicated a minimum of 49 and 20% of the deer mice and kangaroo rat populations, respectively, encountered areas of buried activation and fission waste and/or contaminated soil. (6) Data obtained provided an indirect method of measuring biological intrusion into soil covers over solid low-level radioactive waste disposal areas.
A method to trap rodents in snow, sleet, or rain
A bucket shelter for use with live traps has been developed and employed in over 20 000 live-trap nights during winter trapping of small mammals. This shelter is easily prepared, is relatively inexpensive, can be employed in large numbers, and affords good protection of traps.