Dense non-aqueous phase liquid

A dense non-aqueous phase liquid or DNAPL is a liquid that (1) is denser than water and (2) 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. Since the fluid is both immiscible in water and denser than water, DNAPL tends to sink below the water table when spilled in significant quantities. As the DNAPL penetrates deeper into the ground, it is more difficult to remediate. While DNAPLs are immiscible in water and therefore have low solubility in water, many DNAPLs have solubilities that is still above the concentrations protective of drinking water protection. Therefore, these DNAPLs can act as an ongoing pathway for constituents to dissolve into groundwater.

The most common types of DNAPL are chlorinated solvents, such as trichloroethylene and tetrachloroethene. Other types of DNAPL include coal tar and creosote, polychlorinated biphenyl (PCBs)and mercury. DNAPLs can also be mixtures of compounds.

LNAPLs (light non-aqueous phase liquids) consist of water immiscible liquids that are lighter than water.

Some DNAPLs that consist of chlorinated solvents can be broken down by methanogens, but only in anoxic conditions.

References

U.S. EPA, 2003. "The DNAPL Remediation Challenge: Is There a Case for Source Depletion?" EPA/600/R-03/143.

Cohen R.M, and J.W. Mercer. 1993. DNAPL Site Evaluation. CRC Press, Boca Raton, FL.

• http://www.clu-in.org/contaminantfocus/default.focus/sec/Dense_Nonaqueous_Phase_Liquids_(DNAPLs)/cat/Overview/ EPA's Technology Innovation and Field Services page on DNAPL
• DNAPL Definition from the USGS
• Educational website on DNAPLs in groundwater

de:Schwerphase