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)
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Accurate Assessment of Natural Attenuation using Depth Discrete Multi-Level Monitoring: Evidence at Three Chlorinated Solvent Sites
Guilbeault, M.A. (Univ. of Waterloo, Waterloo, Ontario, Canada); B.L. Parker; J.A. Cherry. 2001 International Containment & Remediation Technology Conference & Exhibition, 10-13 June 2001, Orlando, Florida. Conference Program Abstracts. Florida State Univ., Tallahassee. p 120, 2001
Releases of PCE and TCE decades ago at three industrial sites in Florida, New Hampshire, and Ontario formed suspended DNAPL source zones and dissolved phase plumes within sandy aquifers. Detailed multi-level monitoring of ground-water concentrations along transects orthogonal to flow was performed at all three sites to examine natural attenuation processes. The Waterloo Profiler and permanently installed multi-level bundle samplers were driven by an Enviro-Core direct-push rig at more than 70 locations and used at a vertical spacing as close as 15 cm to determine peak concentrations within the source areas and downgradient dissolved phase plumes, where conventional monitoring wells had underestimated peak concentrations and even the location of the plume. Continuous cores used to determine stratigraphy and concentration profiles showed that the maximum concentration peaks along vertical profiles were extremely sharp and varied a maximum of 4.5 orders of magnitude over a vertical interval as small as 30 cm. The high resolution sampling showed that 90% of the mass discharge occurs within less than 20% of the transect cross-sectional area at each site. All three sites showed strong attenuation of peak concentrations from solubility to less than 15% (Ontario), 10% (New Hampshire), and 1% (Florida) of solubility within 10 m, 5 m, and 30 m, respectively. Dispersion was the dominant attenuation mechanism at all three sites and degradation accounted for considerable attenuation at the Florida site.
Detailed Vertical and Lateral Delineation of Redox Zones in Contaminant Plumes Using Redox-Sensitive Tapes (RST)
Blum, P. (Eberhard-Karls Univ. Tuebingen, Germany); F.D. Oeste (gM-Ingenieurbuero, Kirchhain, Germany); R. Melzer (URS Deutschland GmbH, Hannover, Germany); P. Martus (URS Canada Inc., Vancouver, BC). Eos, Transactions of the AGU, Vol 87 No 52, Abstract B53B-0345, 2006
Innovative redox-sensitive tape (RST) has been developed for a detailed vertical and lateral delineation of redox zones in contaminated aquifers. The tape consists of a synthetic textile 2 cm wide and coated with reactive manganese dioxide minerals. RST is submerged into existing monitoring wells for approximately one month, which is sufficient time to allow for a reaction of the mineral coating with ground water. RST can be used to investigate four different redox zones in contaminated aquifers: Mn(II)-oxidizing, Mn(IV)-reducing, Fe(III)-reducing, and sulfate-reducing. Two RST case studies are presented. RST investigations on a coal tar-contaminated site allowed for a precise lateral and vertical delineation of the contaminant plume via the existing monitoring well network. RST investigations on a BTEX-contaminated site showed good correlation of RST data with hydrochemical data in sampled wells. Repeated application of RST facilitated an assessment of the plume dynamics. RSTs have the potential to become an integral part of a data acquisition strategy for monitored natural attenuation.
Investigation of NA Processes at Reactive Fringes: Sampling Bias Introduced by High Resolution Multi-Level Monitoring
Piepenbrink, M. (Univ. of Tuebingen, Tuebingen, Germany); T. Ptak (Univ. of Goettingen, Goettingen, Germany); P. Grathwohl (Univ. of Tuebingen). Eos Trans. AGU, Vol 86 No 52, Fall Meet. Suppl., Abstract B31A-0966, 2005
High-resolution multi-level sampling (MLS) in the order of decimeters or less is an essential prerequisite for the investigation of natural attenuation processes at the reactive fringes at field scale. In contrast to engineered remediation techniques that usually address high contaminant concentration levels close to the source zone, monitored natural attenuation (MNA) relies heavily on the accuracy of the low concentration levels (down to the legal limits) measured in the plume. These data are often strongly biased due to the monitoring equipment. This paper presents results from ongoing controlled laboratory material tests and research on high-resolution MLS at six field sites. The focus was on a optimized site-specific hydraulic design and contaminant/MLS-material interaction. The most acceptable solutions (MLS resolution on the order of 0.1m) were found using sampling tubes with a small inner diameter (3-4 mm), which resulted in a small stagnant water volume prior to sampling, but was still not problematic with respect to the flow induced hydraulic losses within the tube. The authors present two major conclusions of the study to date. (1) Due to sorptive losses in dedicated, pristine tubing material, MLS systems tend to underestimate the contaminant concentrations, which leads to an overestimation of the NA potential. To avoid this false negative concentration bias, the most inert tubing material should be used. (2) Due to leaching of plasticizers (e.g., phthlates) out of the pristine tubing material, MLS systems tend to overestimate TOC sum parameters. To avoid this false positive concentration, only polymers with no or low plasticizer content should be used.
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