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BASIS # 2309TZ 26

Title Hazard Assessment of Contaminated Sites at Beltsville Agricultural Research Center

Project Description

The Beltsville Agriculture Research Center (BARC) was declared a Superfund site under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) in the 1980's due to historical pollution of persistent contaminants including metals and some organic compounds.  Several environmental assessments have been conducted since then and many of the forested wetlands located on BARC property have been identified as areas of concern.   

Amphibians have been of concern under these assessments because they are important parts of the communities they inhabit and are frequent residents and breeders in affected wetlands.  In the BARC Facility-wide Screening-Level Ecological Risk Assessment (SERA) and Step 3a ERA reports (ENTECH Inc., 2001 and 2002), exposure pathways for amphibians were considered in conjunction with fish as aquatic receptors.  In the subsequent Baseline Ecological Risk Assessment (BERA), amphibians were considered separately from fish because amphibians may be at increased risk to effects of environmental stressors including site-related contaminants.   

At least nine species of anurans (frogs and toads) and several more salamanders inhabit BARC or adjacent lands.  Many potential exposure pathways link these amphibians to contaminants of concern (COCs). These include contact with water borne or dissolved contaminants in any of the life stages, direct dermal or respiratory contact while on land as juveniles or adults, ingestion of contaminant-bearing detritus or insects as larval or adults, or dermal absorption from contaminated sediments as larvae or hibernating adults.  Effects from these contaminants in laboratory exposures generally occur in the ppm range for median lethal concentrations (LC50s) and even the ppb range for measurable sublethal effects.  Given the range of possible scenarios and that the source of contamination was more historical rather than current, we believe that the route of exposure of greatest concern comes from contact with sediments or over-lying water that contain persistent contaminants such as metals and certain organic compounds.   Because sediments contain much higher concentrations of persistent contaminants (by 1-3 orders of magnitude) than water, it can be surmised that sediments may pose greater threats.  

This study proposes to assess the hazards of contaminated wetlands at BARC to a common native amphibian, the southern leopard frog (Rana sphenocephala) that is known to inhabit or potentially use all of the wetlands of concern.  Specifically, the assessment endpoint selected for amphibians is the maintenance of amphibian population abundance. The hazard assessment will be based on a combination of lethal and sublethal indicators. Specific endpoints incorporated in this risk assessment include growth and development of larvae, occurrence and type of malformations, bioaccumulation of COCs, mortality, and selected measures of physiological health (e.g. glutathione).   

Keywords Sediment toxicity, amphibians, Superfund, risk assessment, organochlorines, metals, Rana, CERCLA, contaminants

Principal Investigator Don Sparling, USGS Patuxent Wildlife Research Center: Don_Sparling@usgs.gov 

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