139:(USEPA) has focused considerable attention on the remediation of DNAPL which can be costly. Removal or in situ destruction of DNAPLs eliminates the potential exposure to the compounds in the environment and can be an effective method for remediation; however, at some DNAPL sites remediation of DNAPL may not be practicable, and containment may be the only viable remedial action. The USEPA has a program to address sites where DNAPL removal is not practicable for remediation projects under
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interacts with the natural environment. As an example, a mixture of trichloroethene and cutting oil may be released and originally be denser than water—a DNAPL. As the mixture of trichloroethene and oil is leached by groundwater, the trichloroethene may preferentially leach out of the oil and the mixture may become less dense than water and become buoyant (e.g. the liquid may become an LNAPL). Similarly changes can be seen at some
127:, with the rate of usage for most solvents increasing into the 1970s. By the early 1980s, chemical analyses becoming available that documented widespread contamination of groundwater with chlorinated solvents. Since that time, a considerable effort has been extended to improve our ability to locate and remediate DNAPL present as chlorinated solvents.
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definition, yet still have a solubility above the concentrations allowed by drinking water protections. Therefore, DNAPL which is a chlorinated solvent can act as an ongoing pathway for constituents to dissolve into groundwater. Common use of chlorinated solvents in manufacturing operations began during
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Dense nonaqueous phase liquids (DNAPLs), have low solubility and are with viscosity markedly lower and density higher than water-asphalt, heavy oils, lubricants and also chlorinated solvents-penetrate the full depth of the aquifer and accumulate on its bottom. "DNAPL movement follows the slope of the
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technologies have been developed that can address DNAPL in some settings. Excavation is not always practicable due to the depths of the DNAPL, the dispersed nature of the residual DNAPL, mobility caused during excavation, and complexities with near-by structures. Technologies that are emerging for
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Most DNAPLs remain denser than water after they are released into the environment (e.g. spilled trichloroethene does not become lighter than water, it will remain denser than water). However, when the DNAPL is a more complex mixture, the density of the mixture can change over time as the mixture
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When spilled into the environment, chlorinated solvents are frequently present as DNAPL and the DNAPL can provide a long term secondary source of the chlorinated solvent to dissolved groundwater plumes. Chlorinated solvents are typically immiscible in water, having low solubility in water by
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Pankow, James F., Stan
Feenstra, John A. Cherry and M. Cathryn Ryan, "Dense Chlorinated Solvents in Groundwater: Background and History of the Problem" in Dense Chlorinated Solvents and Other DNAPLs in Groundwater ed. James Pankow & John Cherry,
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DNAPLs that are not viscous, such as chlorinated solvents, tend to sink into aquifer materials below the water table and become much more difficult to locate and remediate than non aqueous phase liquids that are lighter than water
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plants or manufactured gas plants where the tar mixtures can be denser than water, be neutrally buoyant or be less dense than water and the densities can change with time.
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when spilled in significant quantities and only stop when they reach impermeable bedrock. Their penetration into an aquifer makes them difficult to locate and remediate.
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Ruth M Davison, Gary P Weathhall and David N Lerner, 2002. Source
Treatment for Dense Non-Aqueous Phase Liquids. Technical Report P5-051/TR/01.
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ITRC, 2000. "Dense Non-Aqueous Phase
Liquids (DNAPLs): Review of Emerging Characterization and Remediation Technologies"
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U.S. EPA, 1993. "Guidance for
Evaluating the Technical Impracticability of Groundwater Restoration" Directive 9234.2-25
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impermeable strata underlying the aquifer and can move in the opposite direction to the groundwater gradient."
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http://cluin.org/contaminantfocus/default.focus/sec/Dense_Nonaqueous_Phase_Liquids_(DNAPLs)/cat/Overview/
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USEPA, 2003. "The DNAPL Remediation
Challenge: Is There a Case for Source Depletion?" EPA/600/R-03/143.
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Dense
Chlorinated Solvents and Other DNAPLs in Groundwater ed. James Pankow & John Cherry, 1996.
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ITRC, 2007. In Situ
Bioremediation of Chlorinated Ethene DNAPL Source Zones: Case Studies.
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315:"CLU-IN | Contaminants > Dense Nonaqueous Phase Liquids (DNAPLs) > Overview"
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Cohen R.M, and J.W. Mercer. 1993. DNAPL Site
Evaluation. CRC Press, Boca Raton, FL.
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http://www.itrcweb.org/documents/IntegratedDNAPLStrategy_IDSSDoc/IDSS-1.pdf
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http://publications.environment-agency.gov.uk/pdf/SP5-051-TR-1-e-p.pdf
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Interstate
Technology & Regulatory Council (ITRC) page on DNAPL:
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Groundwater Early
Warning Monitoring Strategy A Methodological Guide
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http://www.clu-in.org/download/contaminantfocus/dnapl/600r93022.pdf
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ITRC Integrated DNAPL Site Strategy technical/regulatory guidance:
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The term DNAPL is used primarily by environmental engineers and
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51:, surface water and sediments. DNAPLs tends to sink below the
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Examples of materials that are DNAPLs when spilled include:
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Intensive Use of Groundwater: Challenges and Opportunities
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Manuel Ramâon Llamas; Emilio Custodio, eds. (2003).
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and is immiscible in or does not dissolve in water.
329:http://www.clu-in.org/download/remed/600R03143.pdf
247:http://www.itrcweb.org/guidancedocument.asp?TID=8
401:http://www.itrcweb.org/Documents/DNAPLs-1.pdf
137:United States Environmental Protection Agency
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116:per- and polyfluoroalkyl substances
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18:dense non-aqueous phase liquid
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192:in situ surfactant flushing
47:to describe contaminants in
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364:. CRC Press. p. 478.
188:reductive dechlorination
94:polychlorinated biphenyl
152:Groundwater remediation
24:is a denser-than-water
163:potassium permanganate
105:extra heavy crude oil
75:1,1,1-trichloroethane
79:carbon tetrachloride
63:chlorinated solvents
425:2006-02-18 at the
205:coal gasification
186:in situ enhanced
168:hydrogen peroxide
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229:than water.
109:API gravity
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450:Categories
259:References
180:persulfate
143:under the
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382:(Report).
28:, i.e. a
423:Archived
221:LNAPLs (
211:See also
176:sparging
114:certain
89:creosote
84:coal tar
227:lighter
198:heating
100:mercury
273:, USGS
141:CERCLA
133:LNAPLs
118:(PFAS)
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34:denser
30:liquid
380:(PDF)
283:1996.
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