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- Q902498 subject Q7297892.
- Q902498 subject Q8529495.
- Q902498 abstract "A dense non-aqueous phase liquid or DNAPL is a denser-than-water NAPL, i.e. a liquid that is both denser than water and is immiscible in or does not dissolve in water.The term DNAPL is used primarily by environmental engineers and hydrogeologists to describe contaminants in groundwater, surface water and sediments. DNAPLs tends to sink below the water table 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.Examples of materials that are DNAPLs when spilled include: chlorinated solvents, such as trichloroethylene, tetrachloroethene, 1,1,1-trichloroethane and carbon tetrachloride coal tar creosote polychlorinated biphenyl (PCBs) mercury extra heavy crude oil, with an API gravity of less than 10When 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 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 World War II, 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.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 (LNAPLs) which tend to float at the water table when spilled into natural soils. The United States Environmental Protection Agency (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 CERCLA under the Resource Conservation and Recovery ActDense 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.(2003 & Llamas 118)(2008 & Vrba 23) "DNAPL movement follows the slope of the impermeable strata underlying the aquifer and can move in the opposite direction to the groundwater gradient."(2008 & Vrba 23)Groundwater remediation 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 treatment include the following in situ chemical oxidation (ISCO) potassium permanganate hydrogen peroxide (with or without an iron catalyst) ozone sparging persulfate in situ enhanced reductive dechlorination in situ surfactant flushing air sparging heatingMost 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 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 then water and become buoyant (e.g. the liquid may become an LNAPL). Similarly changes can be seen at some coal gasification plants or manufactured gas plants where the tar mixtures can be denser than water, be neutrally buoyant or be less dense then water and the densities can change with time.".
- Q902498 wikiPageExternalLink Overview.
- Q902498 wikiPageExternalLink IDSS-1.pdf.
- Q902498 wikiPageExternalLink guidancedocument.asp?TID=8.
- Q902498 wikiPageWikiLink Q11027905.
- Q902498 wikiPageWikiLink Q11435.
- Q902498 wikiPageWikiLink Q15280487.
- Q902498 wikiPageWikiLink Q161268.
- Q902498 wikiPageWikiLink Q161598.
- Q902498 wikiPageWikiLink Q171877.
- Q902498 wikiPageWikiLink Q179509.
- Q902498 wikiPageWikiLink Q190865.
- Q902498 wikiPageWikiLink Q19598149.
- Q902498 wikiPageWikiLink Q211171.
- Q902498 wikiPageWikiLink Q225045.
- Q902498 wikiPageWikiLink Q2280718.
- Q902498 wikiPageWikiLink Q283.
- Q902498 wikiPageWikiLink Q29246.
- Q902498 wikiPageWikiLink Q3504641.
- Q902498 wikiPageWikiLink Q362.
- Q902498 wikiPageWikiLink Q36933.
- Q902498 wikiPageWikiLink Q3820407.
- Q902498 wikiPageWikiLink Q407936.
- Q902498 wikiPageWikiLink Q410772.
- Q902498 wikiPageWikiLink Q426809.
- Q902498 wikiPageWikiLink Q460173.
- Q902498 wikiPageWikiLink Q5611037.
- Q902498 wikiPageWikiLink Q583075.
- Q902498 wikiPageWikiLink Q7297892.
- Q902498 wikiPageWikiLink Q7306385.
- Q902498 wikiPageWikiLink Q7315799.
- Q902498 wikiPageWikiLink Q8529495.
- Q902498 wikiPageWikiLink Q909808.
- Q902498 wikiPageWikiLink Q909968.
- Q902498 wikiPageWikiLink Q925.
- Q902498 wikiPageWikiLink Q948232.
- Q902498 comment "A dense non-aqueous phase liquid or DNAPL is a denser-than-water NAPL, i.e. a liquid that is both denser than water and is immiscible in or does not dissolve in water.The term DNAPL is used primarily by environmental engineers and hydrogeologists to describe contaminants in groundwater, surface water and sediments. DNAPLs tends to sink below the water table when spilled in significant quantities and only stop when they reach impermeable bedrock.".
- Q902498 label "Dense non-aqueous phase liquid".