Assessing aerobic natural attenuation of trichloroethene at four DOE sites
- North Wind, Inc., Idaho Falls, ID (United States)
- CDM, Inc., Denver, CO (United States)
A 3-year Department of Energy Environmental Science Management Program (EMSP) project is currently investigating natural attenuation of trichloroethane (TCE) in aerobic groundwater. This presentation summarizes the results of a screening process to identify TCE plumes at DOE facilities that are suitable for assessing the rate of TCE cometabolism under aerobic conditions. In order to estimate aerobic degradation rates, plumes had to meet the following criteria: TCE must be present in aerobic groundwater, a conservative co-contaminant must be present and have approximately the same source as TCE, and the groundwater velocity must be known. A total of 127 TCE plumes were considered across 24 DOE sites. The four sites retained for the assessment were: (1) Brookhaven National Laboratory, OU III; (2) Paducah Gaseous Diffusion Plant, Northwest Plume; (3) Rocky Flats Environmental Technology Site, Industrialized Area--Southwest Plume and 903 Pad South Plume; and (4) Savannah River Site, A/M Area Plume. For each of these sites, a co-contaminant derived from the same source area as TCE was used as a nonbiodegrading tracer. The tracer determined the extent to which concentration decreases in the plume can be accounted for solely by abiotic processes such as dispersion and dilution. Any concentration decreases not accounted for by these processes must be explained by some other natural attenuation mechanism. Thus, ''half-lives'' presented herein are in addition to attenuation that occurs due to hydrologic mechanisms. This ''tracer-corrected method'' has previously been used at the DOE's Idaho National Engineering and Environmental Laboratory in conjunction with other techniques to document the occurrence of intrinsic aerobic cometabolism. Application of this method to other DOE sites is the first step to determining whether this might be a significant natural attenuation mechanism on a broader scale. Application of the tracer-corrected method to data from the Brookhaven National Laboratory site using carbon tetrachloride as the conservative tracer under aerobic conditions showed evidence of TCE attenuation with a range of TCE half-lives from 2 to 9.5 years. At Paducah Gaseous Diffusion Plant's Northwest Plume the assessment was performed using Tc-99 as the conservative tracer. TCE appears to have a half-life of about 7 years in the lower portion of the Northwest Plume regional gravel aquifer. Evidence for TCE attenuation at Rocky Flats Environmental Technology Site was identified in two plumes. PCE was used as the conservative tracer in both plumes. TCE appears to be attenuating with a half-life of 0.85 years in the Industrialized Area--Southwest Plume, and with a half-life of 2.4 years in the 903 Pad South Plume. At the Savannah River Site, A/M Area, PCE was used as the conservative tracer in five different horizons. In four of the five horizons, TCE appears to be degrading with a half-life between 4 and 12 years, while no degradation could be quantified in the fifth horizon. If aerobic TCE degradation can be confirmed at these sites, this attenuation mechanism might be important much more often than previously thought, and might make MNA feasible where it was previously not considered.
- Research Organization:
- North Wind Inc. (formerly North Wind Environmental), Idaho Falls, ID (United States)
- Sponsoring Organization:
- USDOE Office of Environmental Management (EM)
- DOE Contract Number:
- FG07-02ER63510
- OSTI ID:
- 837340
- Resource Relation:
- Conference: Waste Management '05 (WM2005), Tuscon, AZ (United States), 27 Feb - 3 Mar 2005
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
AEROBIC CONDITIONS
ATTENUATION
BNL
CARBON TETRACHLORIDE
DILUTION
GASEOUS DIFFUSION
GASEOUS DIFFUSION PLANTS
HALF-LIFE
MANAGEMENT
PLUMES
SAVANNAH RIVER PLANT
VELOCITY
WASTE MANAGEMENT
natural attenuation
biodegradation
bioremediation
hazardous waste
organic chemicals
organic contaminants
groundwater
ground water
remediation