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Development of Mineral Environmental Assessment Methodologies
(Project status is complete. Please check the project list for currently active projects.)

Development of Mineral Environmental Assessment Techniques at the Watershed Scale


Task Objectives

The potential impact of a mineralized area or a mine site on the environment depends not only on the characteristics of the mineral deposit present (i.e., geology, mineralogy, alteration, host rocks, grade, tonnage, trace metal content, etc.), but also the characteristics of the surrounding environment (watershed lithology, structure, geology, climate, hydrology, ground- and surface water compositions, precipitation, vegetation, topography, etc.). For example, for aquatic ecosystems, water chemistry factors such as the pH, alkalinity, hardness, and dissolved organic carbon (DOC) concentrations of the impacted water body greatly influence the toxicity of metals and related compounds. Likewise, the diluting role of precipitation also affects the concentration, and thus toxicity of toxic compounds. In assessing the potential environmental consequences of mineral deposits prior to mining and that may result from mining and/or mineral processing, it is essential to develop methodologies that account for these and many other disparate factors.

Commonly, a major concern of mineral development in watersheds is impact on plant and animal life, particularly aquatic biota or humans. The form, or species, of metals in the environment will affect both metal bioavailability and toxicity. Total aqueous metal concentrations are not good predictors of potential metal bioavailability and toxicity because water chemistry affects speciation and can greatly impact bioavailability and toxicity. Similarly, the form of ingested metals greatly affects their toxicity to humans. Without knowledge of speciation, the bioavailability and toxicity of metals tends to be considerably overestimated. Therefore, a methodology is needed that can account for metal speciation (and site-specific characteristics that influence metal speciation) in the assessment of potential consequences of mineral development in specific watersheds. Once metal speciation is accounted for, the link to potential metal toxicity can be made using toxicological models. One such model, the Biotic Ligand Model, has been incorporated into the U.S. Environmental Protection Agency's updated water-quality criteria for copper.

In this part of the project, we

  1. Determined master variables needed to define and forecast baseline water-quality conditions at the watershed scale.
  2. Suggested approaches to be tested at the regional and national scales.

Subtasks to accomplish these objectives are:

Products

See Subtasks for additional products.

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