Grantee Research Project Results

2003 Progress Report: 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: EAGLES - Consortium for Estuarine Ecoindicator Research for the Gulf of Mexico
Center Director: Brouwer, Marius
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. , Westall, John C. , Ahmann, Dianne , Garbarino, John
Institution: Colorado State University , United States Geological Survey , Oregon State University
Current Institution: Colorado State University , Oregon State University , United States Geological Survey
EPA Project Officer: Aja, Hayley
Project Period: November 1, 2001 through October 31, 2003
Project Period Covered by this Report: November 1, 2002 through October 31, 2003
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (2001) Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management

Objective:

The objectives of this research are to: (1) characterize water samples and their associated natural organic matter (NOM) from sites within and beyond the U.S. Environmental Protection Agency (EPA) Region 8 for pH, alkalinity, conductivity, metals content, anion character and quantity, total organic and inorganic carbon, elemental composition, acidity, aromatic content, Fourier Transform Infrared spectrum, and average molecular weight of the NOM; (2) determine the ability of each NOM sample to form aqueous complexes with As and Se; (3) determine the ability of each NOM sample to compete with As and Se for sorption onto hematite and gibbsite, and to estimate the extent to which each NOM sample accelerates redox transformations of As and Se; (4) quantify the abilities of selected NOM samples to accelerate redox transformations as a function of sample history and presence or absence of microorganisms and external electron donors and acceptors; (5) codify observed relationships among NOM characteristics, aqueous geochemistry, and influences on complexation, sorption, and redox reactions of As and Se in an attempt to correlate measurable NOM properties with the magnitudes of the observed effects using techniques such as ANOVA and principle component analysis; (6) investigate the influences of selected samples of NOM on As and Se bioavailability and toxicity in the light of known influences of NOM samples on As and Se complexation, adsorption, and redox behavior; and (7) formulate a conceptual model describing the interactions between NOM, As, and Se that are pertinent for remediation design, and test this model with experiments from field sites for which predictions of As and/or Se behavior can be formulated and tested based on the site properties and the conceptual model.

Progress Summary:

The influence of NOM on the adsorption of As species on hydrous iron oxides has been established, and variations in these effects among five different NOM samples have been detailed. NOM facilitates the partial release of adsorbed As species, and prevents the total adsorption of As species from solution in cases where both NOM and As are co-solutes. The redox chemistry associated with these adsorption events is not understood as well at this point, and work is being performed on the reproducibility and fundamental characterization of the apparent nonequilibrium processes that govern the redox speciation of As in the presence of NOM and iron oxide solids.

In addition, work has been performed with aluminum oxyhydroxide suspensions to remove the complications associated with iron redox chemistry. The presence of very small colloidal material in aqueous systems containing Al oxides has provided rather large analytical challenges to ferreting out the role of adsorption, formation of NOM-Al-As complexes, redox processes mediated by NOM and/or bacteria, and chromatographic separation of various As and As-Al(OH)x species. These difficulties have revealed the care that must be taken to eliminate microbial processes from consideration, and will cause a revisitation of initial conclusions about the role of NOM in As redox speciation in iron oxyhydroxide suspensions. Other work has focused on investigations designed to elucidate the nature of As-NOM-Fe interactions at iron oxyhydroxide surfaces. This understanding is crucial for the application of this research to the design and operation of remediation systems and general problems of As mobility in aqueous systems. An attempt is being made to determine the extent to which such interactions are dependent on the precise nature of the oxide surface and the origin and functional composition of the NOM samples.

Finally, the analytical capability to extend this work to Se is being developed. A reliable technique for the separation and quantification of Se(IV) and Se(VI) in aqueous systems has been developed and tested, and work currently is being undertaken on the capability to reliably detect and quantify aqueous complexes of Se with NOM and colloidal Fe and/or Al oxyhydroxides.

Future Activities:

This project was terminated at the end of the second year of Center activities, although a 6-month, no cost extension has been granted to allow the investigators to complete ongoing tasks.

Supplemental Keywords:

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

Relevant Websites:

http://www.engr.colostate.edu/hsrc/ Exit

Progress and Final Reports:

Original Abstract

2002 Progress Report

Final

Main Center Abstract and Reports:

R829515    EAGLES - Consortium for Estuarine Ecoindicator Research for the Gulf of Mexico

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