Nonaqueous Phase Liquids (NAPLs) are hazardous organic liquids such as dry cleaning fluids, fuel oil, and gasoline that do not dissolve in water. A significant portion of contaminated soil and groundwater sites contain NAPLs, and they are particularly hard to remove from the water supply. NAPLs are always associated with human activity, and cause severe environmental and health hazards.

Dense NAPLs (DNAPLs) such as the chlorinated hydrocarbons used in dry cleaning and industrial degreasing are heavier than water and sink through the water column. They can penetrate deep below the water table and are difficult to find when investigating sites for contamination.

Hydrocarbon fuels and aromatic solvents are described as light NAPLs (LNAPLs), which are less dense than water and float. These include lubricants and gasoline, pollutants often associated with leaking gasoline or oil storage tanks.

It is difficult or impossible to remove all of the NAPLs once they are released into the ground. Although many NAPL removal technologies are currently being tested, there have been few field demonstrations capable of restoring an NAPL-contaminated aquifer to drinking-water quality. NAPL contamination can affect aquifers for tens or hundreds of years.

Internet Resource

Newell, Charles J.; Bowers, Richard L.; and Rifai, Hanadi S. "Impact of Non-Aqueous Phase Liquids on Groundwater Remediation." In Environmental Expert.com Web site. Available from http://www.environmental-center.com/art icles/article1079/article1079.htm.