Grantee Research Project Results
1997 Progress Report: Effect of Spatial Heterogeneity on the Natural Bioattenuation of Dissolved Hydrocarbons
EPA Grant Number: R825418Title: Effect of Spatial Heterogeneity on the Natural Bioattenuation of Dissolved Hydrocarbons
Investigators: Barlaz, Morton A. , Borden, Robert C.
Institution: North Carolina State University
EPA Project Officer: Hahn, Intaek
Project Period: October 28, 1996 through October 27, 1999 (Extended to April 30, 2000)
Project Period Covered by this Report: October 28, 1996 through October 27, 1997
Project Amount: $449,052
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:
The overall objective of this research is to improve our understanding of processes controlling the anaerobic bioattenuation of dissolved hydrocarbons in groundwater. Field and laboratory studies will be conducted in two petroleum contaminated aquifers. The major groundwater contaminants at these sites are benzene--a known carcinogen, toluene, ethylbenzene, and xylene isomers (BTEX). At each site, we will measure spatial variations in contaminant biodegradation rates, sediment characteristics, and microbial populations, and relate these variations to field-scale plume behavior. Results from this work will improve our ability to: (1) estimate the effect of natural bioattenuation processes on the fate and transport of hazardous organics in groundwater; and (2) estimate the risk of these contaminants to the public and environmental receptors.Progress Summary:
We have identified two BTEX plumes for our field studies. The first site is a former fire training area at Pope Air Force Base (Pope AFB) near Fayetteville, NC. The second site is located at Wurtsmith Air Force Base, MI. At this site, the BTEX plume results from the crash of a tanker aircraft carrying JP-4 in October 1988. In the first year of the project, all work has been focused on the Pope AFB site.Objective 1. Develop and validate a field technique for measuring in-situ biodegradation rates over small vertical intervals.
We have completed initial development and testing of a prototype in-situ chamber for measuring vertical variations in biodegradation rates. The system consists of a multilevel injection well installed in the center of a perforated 24-inch diameter steel casing. The perforation size and spacing were determined based on mathematical modeling of solute residence time in the chamber. Preliminary field tests have shown that we can install and monitor this system with minimal mixing between adjoining layers.
Objective 2. Measure small-scale variations in biodegradation rates in two petroleum contaminated aquifers and relate variations in biodegradation rates to differences in sediment composition, geochemistry, and microbial population.
We have completed our initial hydrologic and geochemical characterization of the Pope AFB site. Multilevel samplers have been installed along a transect through the contaminant plume and monitoring has begun for BTEX, electron donors, electron acceptors and indicator parameters. We have also collected sediment samples along the same transect and begun the geochemical characterization of the aquifer solids. Injection well permit applications have been completed and submitted to the US Air Force and State of North Carolina to allow installation of the test chambers. We hope to receive approval and install the first full set of chambers in February 1998.
Objective 3. Use sediment from two petroleum contaminated aquifers to determine: (a) if spatial variations in contaminant biodegradation are due to large-scale spatial variations in the composition of the microbial community; and (b) if spatial variations in microbial populations correlate with the lag period prior to compound biodegradation in laboratory microcosms.
We have collected sediment samples at several locations within the contaminant plume at the Pope AFB site where different redox processes appear to dominate (Fe(III) and SO4 reduction and methanogenesis). At each location we have used the sediment to enumerate total anaerobes, Fe reducers, sulfate reducers and methanogens. We have also used the sediment to construct microcosms under various redox conditions and are monitoring the microcosms to determine if biodegradation activity against specific varies with sediment source location and/or available electron acceptors. Preliminary results suggest that there are significant spatial variations in biodegradation activity. Additional studies will be conducted with this material to determine if the variation in biodegradation is related to differences in the microbial community or differences in sediment characteristics.
Objective 4. Evaluate the effect of large- and small-scale variations in biodegradation rates on field- scale plume behavior.
We have begun using the computer package GMS (Groundwater Modeling System) for data analysis and modeling of solute transport at the Pope AFB site. In our initial work, we are attempting to simulate transport of a non-reactive solute along a vertical transect down the contaminant plume. Solute movement will be calibrated against monitoring data from the existing conventional well network and lines of multilevel samplers installed as part of this project. Spatial variations in hydraulic conductivity will be determined from specific capacity test conducted at multiple depths and locations along the transect.
Future Activities:
This spring we will complete installation of the in-situ test chambers at Pope AFB and begin modeling of contaminant transport and biotransformation under anaerobic conditions. We expect to begin fieldwork at Wurtsmith AFB this summer and install in-situ chambers at that site in the fall.Journal Articles:
No journal articles submitted with this report: View all 17 publications for this projectSupplemental Keywords:
natural, attenuation, hydrocarbon, anaerobic, heterogeneity., RFA, Scientific Discipline, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Contaminated Sediments, exploratory research environmental biology, Environmental Chemistry, Ecosystem/Assessment/Indicators, Chemical Mixtures - Environmental Exposure & Risk, Ecosystem Protection, Ecological Effects - Environmental Exposure & Risk, Ecological Effects - Human Health, Hazardous Waste, Ecological Risk Assessment, Groundwater remediation, Hazardous, Ecological Indicators, treatment residuals, ecological exposure, risk assessment, petroleum contaminants, ecological receptors, biodegradation, spatial heterogeneity, contaminated sediment, hazardous organic contaminants, dissolved hydrocarbons, bioattenuation, ecological impacts, risk assessments, aquifers, hydrocarbons, ecosystem impactsProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.