Valence state: The combining capacity of an atom or radical determined by the number of electrons that it will lose, add, or share when it reacts with other atoms.
free product: A NAPL found in the subsurface in sufficient quantity that it can be partially recovered by pumping or gravity drain.
aerobic: Direct aerobic metabolism involves microbial reactions that require oxygen to go forward. The bacteria uses a carbon substrate as the electron donor and oxygen as the electron acceptor. Degradation of contaminants that are susceptible to aerobic degradation but not anaerobic often ceases in the vicinity of the source zone because of oxygen depletion. This can sometimes be reversed by adding oxygen in the form of air (air sparging, bioventing), ozone, or slow oxygen release compound (e.g., ORC(r)).
Aerobic dechlorination may also occur via cometabolism where the dechlorination is incidental to the metabolic activities of the organisms. In this case, contaminants are degraded by microbial enzymes that are metabolizing other organic substrates. Cometabolic dechlorination does not appear to produce energy for the organism. At pilot- or full-scale treatment, cometabolic and direct dechlorination may be indistinguishable, and both processes may contribute to contaminant removal. For aerobic cometabolism to occur there must be sufficient oxygen and a suitable substrate which allows the microbe to produce the appropriate enzyme. These conditions may be present naturally but often in the presence of a source area oxygen and a substrate such as methane or propane will need to be introduced.
Adapted from US. EPA 2006 Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites
anaerobic: Direct anaerobic metabolism involves microbial reactions occurring in the absence of oxygen and encompasses many processes, including fermentation, methanogenesis, reductive dechlorination, sulfate-reducing activities, and denitrification. Depending on the contaminant of concern, a subset of these activities may be cultivated. In anaerobic metabolism, nitrate, sulfate, carbon dioxide, oxidized metals, or organic compounds may replace oxygen as the electron acceptor.
Anaerobic dechlorination also may occur via cometabolism where the dechlorination is incidental to the metabolic activities of the organisms. In this case, contaminants are degraded by microbial enzymes that are metabolizing other organic substrates. Cometabolic dechlorination does not appear to produce energy for the organism. At pilot- or full-scale treatment, cometabolic and direct dechlorination may be indistinguishable, and both processes may contribute to contaminant removal.
Quoted from US. EPA 2006 Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites
architecture: "Architecture" refers to the physical distribution of the contaminant in the subsurface. Residuals that take the form of long thin ganglia or small dispersed globules provide a larger surface area that will dissolve much faster than if the same amount of liquid were concentrated in a competent pool.
Sources: For purposes of this discussion, a DNAPL source zone includes the zone that encompasses the entire subsurface volume in which DNAPL is present either at residual saturation or as "pools" of accumulation above confining units. In addition, the DNAPL source zone includes regions that have come into contact with DNAPL that may be storing contaminant mass as a result of diffusion of DNAPL into the soil or rock matrix.
source zone: For purposes of this discussion, a DNAPL source zone includes the zone that encompasses the entire subsurface volume in which DNAPL is present either at residual saturation or as "pools" of accumulation above confining units. In addition, the DNAPL source zone includes regions that have come into contact with DNAPL that may be storing contaminant mass as a result of diffusion of DNAPL into the soil or rock matrix.
focal ulceration: The process or fact of a localized area being eroded away.
metaplasia of the glandular stomach: A change of cells to a form that does not normally occur in the tissue in which it is found.
hyperplasia of the glandular stomach: A condition in which there is an increase in the number of normal cells in a tissue or organ.
histiocytic: Degenerative.
duodenum: First part of the small intestine.
microcytic: Any abnormally small cell.
squamous cell papillomas: A small solid benign tumor with a clear-cut border that projects above the surrounding tissue.
squamous cell carcinomas: Cancer that begins in squamous cells-thin, flat cells that look under the microscope like fish scales. Squamous cells are found in the tissue that forms the surface of the skin, the lining of hollow organs of the body, and the passages of the respiratory and digestive tracts. Squamous cell carcinomas may arise in any of these tissues.
jejunum: The middle portion of the small intestine, between duodenum and ileum. It represents about 2/5 of the remaining portion of the small intestine below duodenum.
ileum: The distal and narrowest portion of the small intestine.
squamous: Flat cells that look like fish scales.
metaplasia: A condition in which there is a change of one adult cell type to another similar adult cell type.
ossification: The process of creating bone, that is of transforming cartilage (or fibrous tissue) into bone.
clastogenesis: Any process resulting in the breakage of chromosomes.
neoplastic: Abnormal and uncontrolled growth of cells.
ulceration: The process or fact of being eroded away.
leucocytosis: An elevation of the total number of white cells in blood.
neutrophils: A type of white blood cell.
chromodulin: A small protein that binds four trivalent chromium ions.
biomagnification: The increased accumulation and concentration of a contaminant at higher levels of the food chain; organisms higher on the food chain will have larger amounts of contaminants than those lower on the food chain, because the contaminants are not eliminated or broken down into other chemicals within the organisms.
exencephaly: Cerebral tissue herniation through a congenital or acquired defect in the skull.
everted viscera: Rotated body organs in the chest cavity.
To Be Considered: Documents, such as federal or state guidances, that are not legally binding but may be relevant to the topic in question.
gaining: A gaining surface water body is one where groundwater flows into it.
losing: A surface water body is losing when there is a permeable sediment bed that is not in contact with the groundwater allowing the surface water to seep through it.
fluvial: Of or pertaining to flow in rivers and streams.
lacustrine: Of or pertaining to a lake as in lacustrine sediments—sediments at the bottom of a lake.
lipid: Any class of fats that are insoluble in water.
lipophilic: Able to dissolve in lipids—in this case fatty tissue.
organelles: A part of a cell such as mitochondrion, vacuole, or chloroplast that plays a specific role in how the cell functions and membranes.
RfD: The RfD is an estimate of a daily exposure of the human population (including sensitive sub-groups) to a substance that is likely to be without "the appreciable risk of deleterious effects during a lifetime." An RfD is expressed in units of mg/kg-day.
autonomic: That part of the nervous system that controls non-conscious actions such as heart rate, perspiration and digestion.
ataxia: Lack of muscle coordination.
funnel-and-gate configuration: A system where low-permeability walls (the funnel) placed in the saturated zone direct contaminated ground-water toward a permeable treatment zone (the gate)
Hekster, F.M., R.W.P.M. Laane, and P. de Voogt. 2003. Environmental and toxicity effects of perfluoroalkylated substances. Reviews of Environmental Contamination and Toxicology 179:99-121.
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Two variants of hydrophobic flexible membranes have been employed in DNAPL characterization. The basic device is built around an inflatable tubular membrane. The membrane can be fitted with either discretely spaced hydrophobic sorbent packs, or with a dye-impregnated hydrophobic ribbon, or with a cover that changes color in the presence of DNAPL chemicals. It is effective in both the vadose zone and beneath the water table.
The membrane can be deployed using one of two techniques. The deployment method chosen depends on site geology and whether there is a risk of mobilizing the DNAPL. The first technique deploys the membrane directly into an open borehole. The tubular membrane is everted into the open hole using air pressure. As the membrane everts and expands, the sorbent pads or ribbon, which is attached to the membrane, are pressed against the sides of the hole and held there by air pressure. After a period of time ranging from minutes to hours the membrane is removed by pulling up on a removal tether that is attached to it. The retrieval process rolls the outside of the membrane back inside so that the reactive material does not touch the wall as it ascends. Once the membrane is on the surface, it is again turned inside out to expose the reactive ribbon/membrane pads. The presence of colored spots indicates the ribbon has come into contact with a DNAPL. If positive identification of the chemical is required, the stained area of the ribbon/membrane cover or sorbent pad can be preserved and transported to a laboratory facility for analysis. Field GC or GC/MS equipment is usually used to perform this analysis.
If it is unlikely that the borehole will stay open, then the membrane can be deployed through the rods of a cone penetrometer test rig or dual-tube direct push rig. In this configuration, the membrane is pushed directly into the rods with the hydrophobic ribbon/membrane cover facing out. Water is used to carry the membrane down to the bottom of the cased hole. As the rods are pulled up, more water is added to ensure that the membrane and reactive ribbon are flush against the surrounding soil. The water should also supply sufficient strength to keep the hole open. Retrieval is the same as with the open borehole method.
When continuous coring is not done, this method can provide a relatively cheap ($15/ft sampler and ribbon) way to determine if there is residual or mobile NAPL chemicals in the subsurface both above and below the water table.
Hydrophobic dye testing uses a hydrophobic dye to determine the presence of DNAPLs in ex situ soil samples suspected of DNAPL contamination based either on OVA screening results or on MIP results that show high concentrations of total VOCs in subsurface soils. The technique is designed to work with other analytical technologies. The sample is placed in a sample jar and a suitable dye is introduced (e.g., Sudan IV, Oil Red O). The jar is capped and vigorously shaken. A bright red coloration appears in the presence of DNAPL. The lack of a color change does not necessarily mean there is no DNAPL in the soil sample or the soil horizon from which it was taken. Sample handling during extraction of the core sample from the formation may affect results (e.g., draining while being brought to the surface), and poor dye mixing with clayey soil may mask DNAPL presence. Note that Sudan IV is highly toxic and should be carefully handled and disposed of.
This document describes a demonstration of a ribbon sampler at DOE's Savannah River facility at Aiken, SC. It includes a description of the technology, performance, costs, and lessons learned.
Abstracts of Journal Articles
A Comparison of Field Techniques for Confirming Dense Nonaqeuous Phase Liquids
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DNAPL Characterization Using the Ribbon NAPL Sampler: Methods and Results
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