Eastern Mineral and Environmental Resources Science Center

Development of Mineral Environmental Assessment Techniques at the Watershed Scale 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 biota, 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.

The objectives of this Task are to:

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

Statement of Work

Subtasks to accomplish these objectives are:

• 2.1 Groundwater Assessment Methods
• 2.2 Surface Water Assessment Methods
• 2.3 Development of Methods to Assess Biologic Effects and Metal Transport
• 2.4 GIS Applications and Methods to Estimate Deposit and Watershed Source Characterizations
• 2.5 Methods to Evaluate Uncertainty
• 2.6 Scale-Dependent Interpretation of Regional Geochemical Data
• 2.7 Development of Empirical Models
• 2.8 Development of Numerical Models
• 2.9 Development of Expert System Models

Products

See Subtasks for additional products.

• Smith, K.S., 2010, Development of mineral environmental assessment techniques at the watershed scale (Task 2): Mineral Resources Program Assessment Project Leaders Meeting, Lakewood, Colorado, January 26-28, 2010.
• Smith, K., Johnson, R., Manning, A., Yager, D., Bove, D., and Hageman, P., 2010, Watershed-scale modeling approach for metal transport in mineralized areas: 2010 Society for Mining, Metallurgy & Exploration (SME) Annual Meeting & Exhibit, February 28-March 3, 2010, Phoenix, Arizona, p. 104-105. (INVITED)
• Smith, K.S., Manning, A.H., Yager, D.B., and Johnson, R.H., 2010, Watershed-scale modeling approach in mineralized areas: Geological Society of America (GSA) 2010 Annual Meeting, October 31-November 3, 2010, Denver, Colorado, Abstracts with Programs, Vol. 42, No. 5, p. 214.
• Full-day oral session plus a poster session on "Integrated Approaches to Modeling Geochemical, Hydrological, and Ecological Processes in Watersheds," coconveners K.S. Smith, J.S. Baron, J.M. Holloway, and A.H. Manning: Geological Society of America (GSA) 2010 Annual Meeting, November 1-2, 2010, Denver, Colorado.

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