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Using artificial burrows to evaluate inhalation risks to burrowing mammals
James T Markwiese1, Brett Tiller, Randall T Ryti
1Neptune and Company, 1505 15th Street, Suite B, Los Alamos, New Mexico 87544, USA. jimm@neptuneinc.org
Integrated Environmental Assessment and Management
|July 3, 2008
Summary
Carbon tetrachloride (CCl4) vapor plumes at the Hanford Site pose potential risks to burrowing animals. Direct measurements using artificial burrows confirmed CCl4 presence but found levels below ecological screening limits, with no degradation products detected.
Area of Science:
- Environmental Science
- Toxicology
- Ecology
Background:
- Plutonium production at the Hanford Site led to significant carbon tetrachloride (CCl4) discharge into the soil.
- A dispersed CCl4 vapor plume exists in the subsurface, posing potential inhalation risks to fossorial (burrowing) wildlife.
- Historical CCl4 soil gas levels exceeded ecological screening levels, necessitating exposure pathway evaluation.
Purpose of the Study:
- To evaluate the inhalation exposure pathway for burrowing animals to subsurface carbon tetrachloride (CCl4).
- To assess CCl4 concentrations and its degradation products within artificial burrows mimicking fossorial wildlife habitats.
- To determine if CCl4 exposure levels in artificial burrows pose a risk to ecological receptors.
Main Methods:
- Artificial burrows were designed based on Hanford Site fossorial wildlife and deployed in areas with elevated CCl4 soil gas.
- Burrow atmospheres were sampled and analyzed for CCl4 and its degradation products (chloroform, methylene chloride, chloromethane) over three sampling events.
- Sampling captured varying atmospheric conditions to understand their effect on exposure concentrations.
Main Results:
- Carbon tetrachloride (CCl4) was detected in the artificial burrows.
- Maximum CCl4 exposures were observed during periods of low barometric pressure.
- All detected CCl4 levels were below the inhalation-based ecological screening level, and no degradation products were found.
Conclusions:
- Artificial burrows provide an efficient method for obtaining ecologically relevant exposure data.
- Direct measurement of the exposure medium under realistic conditions is a valuable approach for environmental risk assessment.
- Inhalation exposure to CCl4 for burrowing wildlife at this site appears to be below established ecological screening levels.
