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Development of Stable-Metal Isotope Techniques to Determine Metal Pathways and Bioavailability to Aquatic Organisms: Andrew S. Todd
Project Title: Development of Stable-Metal Isotope Techniques to Determine Metal Pathways and Bioavailability to Aquatic Organisms
Mendenhall Fellow: Andrew S. Todd, (303) 236-1426,
Duty Station: Denver, CO
Start Date: January 22, 2007
Education: Ph.D., 2005, Environmental Engineering, University of Colorado
Research Advisors: Kathy Smith,; James Ranville,; Steve Brinkman,; Ian Ridley,
  Andrew S. Todd

Project Description: Acid rock drainage (ARD) is a common feature of watersheds in the Rocky Mountain region of the United States and Canada, and in many other regions of the world, limiting stream biota, including microbes, algae, macroinvertebrates, and fish for many kilometers downstream of ARD sources.  Aquatic biota are known to retain and accumulate dissolved heavy metals from their environment, with levels of uptake dependent on both exposure concentration and duration.  These tissue metal residue concentrations have been used, in conjunction with observations of fish behavior or health, as lines of evidence in weight-of-evidence studies aiming to shed light on observed ecosystem impairments.

Several novel laboratory techniques are proving to be effective tools in this prediction of metal pathways, bioavailability, and toxicity.  For example, radiogenic isotopes have been used successfully in metal exposure studies to determine trace-metal uptake by aquatic organisms.  Another new technique has been developed that offers many of the same advantages as radioisotopes, without the same assemblage of limiting factors.  The use of stable-metal isotopes is evolving as a promising method for the quantitative evaluation of trace metal biodynamics. 

The overarching research objective for this study is to utilize bioassay methods and newly available, stable-metal isotope analytical techniques to advance our quantitative understanding of trace-metal pathways, metal bioavailability, and toxicity to aquatic organisms.  This objective advances the science strategy of the U.S. Geological Survey through its interpretation and further characterization of the links between geologic processes (specifically ARD) and our understanding of human and ecosystem health.

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Last modified: 16:08:33 Thu 13 Dec 2012