Redox Transformations, Complexation and Soil/Sediment Interactions of Inorganic Forms of As and Se in Aquatic Environments: Effects of Natural Organic Matter

EPA Grant Number: R829515C001
Subproject: this is subproject number 001 , established and managed by the Center Director under grant R829515
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: HSRC - Rocky Mountain Regional Hazardous Substance Research Center for Remediation of Mine Waste Sites
Center Director: Shackelford, Charles D.
Title: Redox Transformations, Complexation and Soil/Sediment Interactions of Inorganic Forms of As and Se in Aquatic Environments: Effects of Natural Organic Matter
Investigators: Macalady, Donald L. , Ahmann, Dianne , Westall, John C.
Current Investigators: Macalady, Donald L. , Ahmann, Dianne , Garbarino, John , Westall, John C.
Institution: Colorado State University , Oregon State University
Current Institution: Colorado State University , Oregon State University , U.S. Geological Survey
EPA Project Officer: Lasat, Mitch
Project Period: November 1, 2001 through October 31, 2003
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (2001) RFA Text |  Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management

Objective:

Waters and suspended sediments bearing inorganic forms of arsenic and selenium occur widely and are especially prevalent in sites impacted by mining. These systems present significant concerns for human and ecosystem health and most, if not all, contain natural organic matter (NOM). The chemical and physical properties of NOM suggest its involvement in several critical processes that affect the behavior of As and Se, including oxidation-reduction reactions, competitive interactions affecting sorption, and formation of metal-organic (bridging) complexes. NOM is expected to alter the mobility, transformations, bioavailability, and toxicity of As and Se, and therefore to play an important role in the design of methods to mitigate contamination problems.

We seek to understand and quantify the nature of these interactions and to delineate the environmental conditions under which they are expected to occur. Further, the research will assess the extent to which NOM influences the transport , transformations, bioavailability, and toxicity of As and Se in aquatic systems as a function of system characteristics. To meet these objectives, we will test the following general hypotheses: 1. NOM accelerates redox transformations of As and Se, either directly or by acting as an electron shuttle, to an extent determined by specific properties of the NOM and the system. 2. NOM increases the mobility of Se and As through complexation and interference with sorption. 3. NOM alters As and Se bioavailability and toxicity through its influence on redox reactions, sorption/desorption, and/or aqueous complexation; the net effects represent a balance among these mechanisms. 4. Microbial transformations of As and Se are influenced by the abundance and characteristics of the NOM present, as well as the aqueous geochemistry of the system.

Approach:

We will test well-characterized NOM samples from various environments within and outside EPA Region 8 for their abilities, under standardized conditions, to affect the processes hypothesized above. Using techniques already developed in our laboratories, we will evaluate the ability of each NOM sample to affect As and Se abiotic and microbial redox transformations, influence surface and aqueous complexation, and to alter bioavailability and toxicity. These data will be used to develop conceptual models of the roles of NOM in As and Se biogeochemical processes, and the models will be used for predictions of As and Se behavior at several field sites. Experiments using field samples will be used to modify the models and provide recommendations for the inclusion of the roles of NOM in remediation and abatement plans for sites contaminated with As and/or Se.

Expected Results:

The expected result of this project is the formulation of conceptual models for As/Se/NOM behavior that can be used to inform remediation design in situations where As and/or Se pose threats to ecosystem and human health.

Supplemental Keywords:

groundwater, sediments, environmental chemistry, mining, geochemistry, toxicology, remediation, metal mobility, subsurface, microbiology., RFA, Scientific Discipline, Industry Sectors, Waste, Water, Contaminated Sediments, Remediation, Mining - NAIC 21, Hazardous Waste, Ecology and Ecosystems, Ecological Risk Assessment, Environmental Engineering, Hazardous, Geology, risk assessment, contaminant transport, suspended sediment, contaminated marine sediment, contaminated waste sites, runoff, sediment transport, stream ecosystems, acid mine drainage, remediation technologies, natural organic matter, field monitoring, Selenium, mining, treatment, aquatic ecosystems, groundwater, heavy metals, mining impacted watershed, arsenic, mining wastes, redox

Progress and Final Reports:

  • 2002 Progress Report
  • Final

  • Main Center Abstract and Reports:

    R829515    HSRC - Rocky Mountain Regional Hazardous Substance Research Center for Remediation of Mine Waste Sites

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R829515C001 Redox Transformations, Complexation and Soil/Sediment Interactions of Inorganic Forms of As and Se in Aquatic Environments: Effects of Natural Organic Matter
    R829515C002 Fate and Transport of Metals and Sediment in Surface Water
    R829515C003 Metal Removal Capabilities of Passive Bioreactor Systems: Effects of Organic Matter and Microbial Population Dynamics
    R829515C004 Evaluating Recovery of Stream Ecosystems from Mining Pollution: Integrating Biochemical, Population, Community and Ecosystem Indicators
    R829515C005 Rocky Mountain Regional Hazardous Substance Research Center Training and Technology Transfer Program
    R829515C006 Technical Outreach Services for Communities and Technical Assistance to Brownfields
    R829515C007 Evaluation of Hydrologic Models for Alternative Covers at Mine Waste Sites
    R829515C008 Microbial Reduction of Uranium in Mine Leachate by Fermentative and Iron-Reducing Bacteria
    R829515C009 Development and Characterization of Microbial Inocula for High-Performance Passive Treatment of Acid Mine Drainage
    R829515C010 Reactive Transport Modeling of Metal Removal From Anaerobic Biozones
    R829515C011 Assessment of Electrokinetic Injection of Amendments for Remediation of Acid Mine Drainage
    R829515C012 Metal Toxicity Thresholds for Important Reclamation Plant Species of the Rocky Mountains
    R829515C013 An Improved Method for Establishing Water Quality Criteria for Mining Impacted Streams