An organic liquid contaminant less dense than water that, when released, migrates downward to the water table and floats on top of it. Petroleum fuels (gasoline, diesel, jet fuel, crude oil) are the prototypical LNAPLs.
LNAPLs have specific gravity less than 1.0 and accumulate as a lens on the water table after gravity-driven downward migration through the vadose zone. Water-table fluctuation smears LNAPL through a vertical interval, creating a long-term source of dissolved-phase BTEX, PAHs, and other soluble fractions, plus a vapour-phase contribution to soil gas.
Remediation typically combines source-zone treatment (skimming, dual-phase extraction, multi-phase extraction, in-situ thermal, bioventing) with dissolved-plume management (biosparging, MNA, PRB). The ITRC LNAPL Guidance Document set the modern framework that distinguishes recoverable from residual LNAPL and ties remedial goals to risk and saturation rather than to total mass.
Also known as: LNAPL, light non-aqueous phase liquid, free product.
DNAPL and LNAPL (Non-Aqueous Phase Liquids): treatment approach
Free-phase organic liquids that do not fully dissolve in water and act as long-term source zones for dissolved plumes — DNAPL (denser than water: TCE, PCE, creosote, coal tar) pools below the water table; LNAPL (lighter than water: gasoline, diesel, jet fuel) floats on it.
Per- and polyfluoroalkyl substances: a class of more than 12,000 synthetic compounds built around exceptionally stable carbon-fluorine bonds. PFAS is the family name, not a single chemical. PFOA and PFOS are two specific members of this class.
Perfluorooctanoic acid: a specific eight-carbon long-chain PFAS compound, historically used in non-stick coatings and AFFF firefighting foam. Classified by IARC in 2023 as Group 1, carcinogenic to humans.
Perfluorooctane sulfonic acid: a specific eight-carbon long-chain PFAS compound, historically the active surfactant in 3M Scotchgard and AFFF firefighting foam. Classified by IARC in 2023 as Group 2B, possibly carcinogenic to humans.
Polychlorinated dibenzo-p-dioxins and related furans: highly persistent, fat-soluble chlorinated compounds formed as unintended byproducts of combustion, chlorine-based manufacturing, and herbicide production, with TCDD among the most toxic substances ever characterized.