Grantee Research Project Results

1998 Progress Report: Rates of Arsenic Oxidation-Reduction Reactions in Contaminated Soils: Effects on Arsenic Fate and Mobility

EPA Grant Number: R825403
Title: Rates of Arsenic Oxidation-Reduction Reactions in Contaminated Soils: Effects on Arsenic Fate and Mobility
Investigators: Inskeep, William P.
Current Investigators: Inskeep, William P. , Jones, C. A. , Macur, R. E. , Langner, H. W.
Institution: Montana State University
EPA Project Officer: Chung, Serena
Project Period: December 15, 1996 through December 14, 1999
Project Period Covered by this Report: December 15, 1997 through December 14, 1998
Project Amount: $329,735
RFA: Environmental Fate and Treatment of Toxics and Hazardous Wastes (1996) RFA Text |  Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management , Safer Chemicals

Objective:

1. Determine rates and underlying mechanisms of the reduction of sorbed arsenate in model systems, contaminated soils and mine tailings.
2. Evaluate the importance of As-sulfide formation under conditions typical of As contaminated soils and mine tailings.
3. Evaluate the role of reduction of sorbed arsenate on the mobility and transport of As in contaminated soils, mine tailings and aquifers.

Progress Summary:

During the second year of this project, we have (i) studied the reduction of arsenate in the presence and absence of Fe oxides using different microbial populations, (ii) evaluated the role of arsenate reduction on solubilization of arsenic in contaminated mine tailings under aerobic conditions, and (iii) evaluated the reduction of arsenate and subsequent precipitation of As sulfides under constructed wetland environments. This report will summarize experimental progress during year two of a three-year project. Anticipated directions for the third year are also discussed in the context of results generated thus far.

Accomplishments and Research Results

1. Reduction of Arsenate under Fermentative Conditions
   • Evaluated reduction kinetics of aqueous arsenate using microorganisms from unenriched and enriched cultures obtained from a naturally contaminated As soil
   • Enriched culture found to be dominated by a single fermentative organism with closest relative of Clostridium intestinalis
   • Arsenate reduction not coupled to oxidation of glucose via dissimilatory reduction

2. Reduction of Arsenate in the Presence of Iron Oxides
   • sorbed arsenate not reduced or solubilized under fermentative conditions

3. Reduction of Arsenate under Column Conditions Using As Contaminated Mine Soils
   • Mobilization of arsenic coupled with microbial reduction of As(V) to As(III)

4. Reduction of Arsenate in Constructed Wetlands
   • reduction of As(V) under sulfate reducing conditions results in formation of As₂S₃(s)

Future Activities:

We plan to continue experiments designed to evaluate As (V) reduction rates in the presence and absence of Fe oxides using additional microbial populations capable of reducing either Fe(III) or sulfate. Iron oxides are one of the most important solid phases controlling As behavior in natural systems. Consequently, data on the rates of reduction of As(V) in environments where As(V) is strongly bound to an Fe oxide phase, should improve our understanding of factors responsible for As mobilization in contaminated soils and sediments. Specifically, we have shown that for organisms not capable of reducing Fe(III), As(V) bound to Fe oxides is not readily available for reduction. Conversely, reduction of soluble As(V) proceeds rapidly within time scales of hours, perhaps via a detoxification mechanism. We would like to now turn our attention to reduction rates of oxide-bound As(V) under Fe(III) and sulfate reducing conditions.

During the third year, we will also begin experiments to evaluate As oxidation-reduction processes in several field sites, with the specific goal of linking chemical transformations of As (reduction or oxidation) with specific members of microbial communities associated with As contaminated sites.

Journal Articles on this Report : 2 Displayed | Download in RIS Format

Publications Views

Other project views:	All 12 publications	7 publications in selected types	All 7 journal articles

Publications

Type	Citation	Project	Document Sources
Journal Article	Jones CA, Inskeep WP, Neuman DR. Arsenic transport in contaminated mine tailings following liming. Journal of Environmental Quality 1997;26(2):433-439.	R825403 (1998) R825403 (Final)	not available
Journal Article	Langner HW, Inskeep WP. Microbial reduction of arsenate in the presence of ferrihydrite. Environmental Science & Technology 2000;34(15):3131-3136.	R825403 (1998) R825403 (1999) R825403 (Final)	Abstract: ACS - Abstract Exit

Supplemental Keywords:

oxidation-reduction, microbial ecology, molecular analysis., RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Toxics, Waste, Geographic Area, Water, Ecosystem Protection/Environmental Exposure & Risk, POLLUTANTS/TOXICS, Water & Watershed, Bioavailability, National Recommended Water Quality, Contaminated Sediments, Environmental Chemistry, Geochemistry, State, Arsenic, Fate & Transport, Hazardous Waste, Ecological Risk Assessment, Water Pollutants, Hazardous, fate and transport, hazardous waste treatment, aquatic, contaminated mines, fate, sediment treatment, contaminant transport, redox metabolism, contaminated sediment, mine tailings, sediment transport, transport contaminants, arsenic sulfide, arsenic oxidation, contaminated soil, chemical contaminants, toxicity, mining, watershed influences, aquatic ecosystems, environmental stressors, environmental toxicant, harmful environmental agents, aquifers, redox cycle, aresenic oxidation reduction, arsenic mobility, water quality, Montana , hazardous waste sites, arsenic exposure, exposure assessment, arsenic oxidation reduction, groundwater, mining impacted watershed

Progress and Final Reports:

Original Abstract

1997 Progress Report

Final Report