Non-aqueous phase liquids, or NAPLs, are
organic liquid
A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, a ...
contaminant
Contamination is the presence of a constituent, impurity, or some other undesirable element that spoils, corrupts, infects, makes unfit, or makes inferior a material, physical body, natural environment, workplace, etc.
Types of contamination
Wi ...
s that do not dissolve in, or easily mix with, water (
hydrophobic
In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water.
Hydrophobic molecules tend to be nonpolar and, th ...
), like
oil
An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...
,
gasoline
Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic co ...
and
petroleum
Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
products.
NAPLs tend to
contaminate soil and
groundwaters for very long period of time: they are
persistent organic pollutant
Persistent organic pollutants (POPs), sometimes known as "forever chemicals", are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. They are toxic chemicals that adversely ...
s (POPs).
Many common groundwater contaminants such as
chlorinated
In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polyme ...
solvents and many petroleum products enter the subsurface in nonaqueous-phase solutions. They do not mix readily with water and therefore flow separately from ground water.
If the NAPL is denser than water, like
trichloroethylene
The chemical compound trichloroethylene is a halocarbon commonly used as an industrial solvent. It is a clear, colourless non-flammable liquid with a chloroform-like sweet smell. It should not be confused with the similar 1,1,1-trichloroethane, ...
, it is called
DNAPL (Dense NAPL) and will tend to sink once it reaches the water table. If it is lighter, like gasoline, it is called
LNAPL (Light NAPL) and will tend to float on the water table.
[National Research Council, 1997]
See also
*
DNAPL
*
LNAPL
Notes
References
* National Research Council, 1997
Innovations in ground water and soil cleanup--From concept to commercialization Washington, D.C., National Academies Press, 310 p.
* National Research Council, 1994
Alternatives for ground water cleanup Washington, D.C., National Academies Press, 315 p.
* National Research Council, 1993
In situ bioremediation--When does it work? Washington, D.C., National Academies Press, 224 p.
External links
Toxic Substances Hydrology Programfrom the
USGS
The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, a ...
{{Watersupply-stub
Organochlorides
Water chemistry
Hydrogeology
Water pollution