() Terrestrial ecological risk assessment: comparing results and implications of a screening assessment and field studies.
Tardiff, M1, Hickmott, D2, 1 Neptune and Company, Inc, Los Alamos, New Mexico, USA2 Los Alamos National Laboratory, Los Alamos, New Mexico, USA
ABSTRACT- One mission of Los Alamos National Laboratory has been to develop explosives, machine explosive charges, and test explosive components for the United States nuclear weapons program. Effluents containing high explosives and metals from machining and photographic facilities were discharged to Cañon de Valle for forty years at rates up to ten million gallons per year, making up as much as half of the canyon's flow. Discharges to the canyon were discontinued in 1996. Cañon de Valle has an interrupted stream that supports an herbaceous ground cover and a multi-layer canopy of conifers, oak and aspen. There is an active nesting site for the Mexican spotted owl; a threatened species, within foraging range of the contaminated area. An ecological screening assessment and problem formulation identified barium, copper, lead, silver, and the explosives HMX and RDX as contaminants of potential ecological concern. Small mammals were chosen for field studies because of their small home ranges, site fidelity, year-round occupancy, and multiple trophic levels. Population characteristics were evaluated for Cañon de Valle and a reference canyon. Whole-animal contaminant body burdens were measured and the potential dose to the Mexican spotted owl was estimated. This presentation will compare the screening assessment results with the field study results with a focus on the implications for decision making. Options for bringing the ecological screening process into better alignment with the field study results and a process for using the field study results to generate site specific screening criteria will be discussed.
Key words: small mammals, terrestrial ecological risk assessment, population effects, whole animal body burdens