• Natural Attenuation Evaluation
• Site Characterization

• Integrated Geochemical and Biochemical Characterization Methods
• Alkylbenzenes Process Probes

• Landfill Leachate
• Volatile Organic Compounds (VOCs)
• Metals

Environmental professionals and regulators are routinely tasked with assessing the feasibility of natural attenuation as an alternative to traditional remediation technologies at contaminated sites. Toxics Program scientists are developing methods that can be used by environmental professionals and regulators to assess the long-term potential for biodegradation of contaminants. USGS scientists and their university colleagues working at the Norman (Oklahoma) Municipal Landfill research site have developed two methods to help with this assessment.

• The first method uses a novel combination of microbiological and geochemical techniques. This method involves the detailed mapping of overlapping biogeochemical zones in contamination plumes. Such zone mapping is not possible when either microbiological or geochemical methods are used in isolation. Identification of these biogeochemical zones is key to evaluating the efficacy of natural attenuation because organic contaminants can degrade at different rates and to different extents depending on the dominant microbiological process.
  
  
• The second method relies on characterizing the composition and ratios of isomers of volatile hydrocarbons in ground water to determine whether biodegradation is a dominant mechanism for attenuation of ground-water contaminants. Isomers are compounds having similar physical-chemical properties, but slightly different chemical structures. Isomers of volatile hydrocarbons should be attenuated in contaminated aquifers in the same manner if physical processes, such as advection, sorption, and diffusion, control contaminant transport. In other words the isomers migrate through the subsurface the same distance from the source of contamination. When the isomers show strikingly different attenuation rates or transport distances in contaminated aquifers, it is evident that biodegradation is the dominant process causing attenuation of these compounds. In this instance, the hydrocarbon isomers present in the landfill leachate serve as "process probes." USGS researchers have developed an approach where isomeric alkylbenzenes (hydrocarbons with ring-like chemical structures that have the same chemical formulas, but slightly different structures) are used as probes to discover the processes that control the migration and fate of contaminants. This "process probe" approach has the potential to become one of the criteria for establishing the importance of biodegradation processes in contaminated aquifers.

USGS scientists have used these methods to demonstrate that natural attenuation of contaminants from the Norman Landfill is taking place.

• Fate of Landfill Leachate -- Norman Municipal Landfill, Norman, Oklahoma
• Organic Compounds in Near-Surface Environments: Understanding Fate in a Changing Biogeochemical Landscape
• Does Landfill Methane Degrade Naturally Before Contaminating Ground Water?

Cozzarelli, I.M., Suflita, J.M., Ulrich, G.A., Harris, S.H., Scholl, M.A., Schlottmann, J.L., and Christenson, S., 2000,

Geochemical and microbiological methods for evaluating anaerobic processes in an aquifer contaminated by landfill leachate: Environmental Science and Technology, v. 34, no. 18, p. 4025-4033.

Eganhouse, R.P., Cozzarelli, I.M., Scholl, M.A., and Matthews, L.L., 2001,

Natural attenuation of volatile organic compounds (VOCs) in the leachate plume of a municipal landfill-Using alkylbenzenes as process probes: Ground Water, v. 39, no. 2, p. 192-202.

Eganhouse, R.P., Dorsey, T.F., Phinney, C.P., and Westcott, A.W., 1996,

Processes affecting the fate of monoaromatic hydrocarbons in an aquifer contaminated by crude oil: Environmental Science and Technology, v. 30, p. 3304-3312.

Toxics Landfill Remediation Projects

• Solvent Plume Source Removal Test (Fenton's Reagent), (the source was in a landfill)
• Alternative Landfill Cover Assessment, Fort Carson, CO

USGS Information on Natural Attenuation

• A Unique Approach to Evaluating Natural Attenuation is Applied Worldwide
• Relying on Nature to Clean Up Contaminated Ground Water
  
• Topical Information on Natural Attenuation, Toxics Program
  
• Listing of Toxics Program Projects Evaluating Natural Attenuation
  
• Listing of Other USGS Projects Evaluating Natural Attenuation

Other USGS Landfill Remediation Studies

• Area 6 Landfill, Naval Air Station Whidbey Island, Island County, Washington
  • Simulation of Ground-Water Flow and Potential Contaminant Transport at Area 6 Landfill, Naval Air Station Whidbey Island, Island County, Washington: USGS WRIR 01-4252
  • Technical Oversight and Scientific Investigations at U.S. Navy Facilities in Washington and Alaska, Project Description
• Landfill Leachate Mobilizes Arsenic Bound in Aquifer Sediments: Saco, Maine
• Surface Geophysical Investigation of a Chemical Waste Landfill in Northwestern Arkansas
• Operable Unit 1 (Landfill), Naval Undersea Warfare Center, Division Keyport, Washington
  • Natural Attenuation of Chlorinated Volatile Organic Compounds in Ground Water at Operable Unit 1, Naval Undersea Warfare Center, Division Keyport, Washington: USGS WRIR 02-4119
  • Technical Oversight and Scientific Investigations at U.S. Navy Facilities in Washington and Alaska, Project Description
• Identification of Potential Water-Bearing Zones by the Use of Borehole Geophysics in the Vicinity of Keystone Sanitation Superfund Site, Adams County, Pennsylvania, and Carroll County, Maryland: USGS WRIR 97-4104 (pdf)