What are NAPLs and how may they affect groundwater quality?

What are NAPLs and how may they affect groundwater quality?

NAPLs are liquids with a density less than water. They are hydrocarbons that can affect groundwater quality. Understanding their fate and transport in groundwater and the remediation technologies for NAPL recovery are important areas of study for EPA.

What are DNAPL and LNAPL?

A light non-aqueous phase liquid (LNAPL) is a groundwater contaminant that is not soluble in water and has lower density than water, in contrast to a DNAPL which has higher density than water. Examples of LNAPLs are benzene, toluene, xylene, and other hydrocarbons.

Is TCE an LNAPL or DNAPL?

For example, TCE introduced into the subsurface as a DNAPL may partition onto the soil phase, volatilize into the soil gas, and solubilize into the water phase resulting in contamination in all four phases. TCE can also partition between the water and soil, water and air, and between the soil and air.

How do you remediate LNAPL?

Steam injection: LNAPL is removed by forcing steam into the aquifer to vaporize and solubilize LNAPL, increase LNAPL recovery by reducing the viscosity and interfacial tension of LNAPL, and enhance LNAPL gradient. Vapors, impacted groundwater, and LNAPL are recovered via vapor extraction and hydraulic recovery.

Is diesel an LNAPL?

Light Nonaqueous Phase Liquid (LNAPL) generally refers to petroleum hydrocarbon liquids that are lighter than water (e.g., gasoline, diesel).

Is BTEX a LNAPL?

The entrapped LNAPL, comprised of multicomponent products (e.g., gasoline, jet fuel, diesel), is responsible for the release of benzene, toluene, ethylbenzene, and xylenes (BTEX) into the water, thus generating the dissolved phase plumes of these compounds.

What does LNAPL stand for?

Non-Aqueous Phase Liquids
NAPL stands for Non-Aqueous Phase Liquids. (Chlorinated compounds or petroleum hydrocarbon. products) LNAPL refers to Light Non-Aqueous Phase Liquids (those. that are lighter than water, generally petroleum.

How does TCE get into groundwater?

TCE is a volatile solvent used for degreasing during the manufacture of products. TCE can enter soil, groundwater, and surface water from leaking storage tanks or from improper disposal of wastes. Once TCE reaches groundwater aquifers, it can contaminate private and public drinking water wells.

How is DNAPL detected in soil and groundwater?

Visual detection of DNAPL in soil and groundwater samples may be difficult where the DNAPL is colorless, present in low saturation, or distributed heterogeneously. These factors confound characterization of the movement and distribution of DNAPL even at sites with relatively homogeneous soils and a known, uniform DNAPL source.

When does a DNAPL plume form in groundwater?

A plume of dissolved contaminants, known as the dissolved-phase plume, will form when groundwater contacts either residual saturation, DNAPL pools, or DNAPL lenses. The volume of soil that contains DNAPL at or above residual saturation is termed the source zone.

What happens to DNAPL in a water spill?

In this spill scenario, the residual saturation in the unsaturated zone exhausted the volume of DNAPL, preventing it from reaching the water table. This figure also shows the subsequent leaching (solubilization) of the DNAPL residual saturation by water percolating through the unsaturated zone (vadose zone).

What are the properties of DNAPL in water?

Table 4-1 Properties of Select DNAPL Components Commonly Found at DOE Sites NOTE: Properties are at 20°C. SOURCES: Mueller et al., 1989; Mercer and Cohen, 1990; Montgomery, 1991. a result, when released in the subsurface they typically do not dissolve totally in the groundwater but remain largely as a separate, nonaqueous-phase liquid (NAPL).