Superfund Research Program
Investigating Biogeochemical Controls on Metal Mixture Toxicity Using Stable Isotopes and Gene Expressions
Project Leader: James F. Ranville
Grant Number: R01ES024358
Funding Period: 2014-2018
Assessing site-specific bioavailability is an important consideration in determining and affectively addressing hazards posed by metals-contaminated waste sites. Because metals occur in mixtures rather than as single contaminants at many contaminated sites, accurate assessment of metal exposure and effects to humans and ecosystems must account for mixture effects, which could be additive, less than additive, or more than additive. However, current water quality regulations and management practices usually address individual metals, because adequate tools are not yet available for predicting bioavailability and toxicity of metal mixtures.
The long term objective of this project is to detect, characterize, and assess the risks posed by contaminant metal mixtures. To accomplish that goal, the research team is developing and refining advanced techniques for the detection, assessment, and evaluation of metal bioavailability. Those techniques will include environmental molecular diagnostics and stable isotope assays. The methods being developed as part of this project under controlled conditions are "field-truthed" in a metals-contaminated stream at the North Fork Clear Creek Superfund sitein central Colorado. The approaches and tools developed for that site provide a physical and intellectual decision infrastructure applicable to other meta-contaminated sites.
In this project, a combination of organism- and community-level response studies, genomic bioassays of organism response to multiple-metals exposure, and measurements of bioavailable water-column metals and tissue-metal residues are being developed and applied. The researchers are gaining an understanding of the flux between biological, chemical, and geological interfaces as it relates to bioavailability and remediation effectiveness. Furthermore, the research team is elucidating the geochemical factors affecting biological uptake (e.g., transport into the food chain). They are also conducting a "natural experiment" in the metal-contaminated stream in which they will examine responses before, during, and after installation of a water-treatment system that will decrease concentrations of the metals.
Using the methods developed and tested during the first two years of the project, they will be able to model and observe the effectiveness of the remediation efforts during the later years of the project. Finally, the researchers have delineated a plan for research translation, including engaging end-users (e.g., regulatory agencies, metals-industry representatives, and toxicity modelers) throughout the duration of the project. Although the focus of the research is on a single Superfund site, the methodology and results will be applicable to metal mixtures in many receiving waters, regardless of the contamination source.