Dense nonaqueous phase liquids (dnapls)

The purpose of this section is to identify documents, preferably online, that describe the chemical properties of DNAPLs and their fate and transport in the environment. DNAPL chemicals have a very broad range of chemical properties that make them difficult to group and these differences in chemical properties gives them very different fates. For example trichloroethene (TCE) is less viscous than water, will move readily through a permeable subsurface, can be anaerobically degraded under the proper conditions, and does not bioaccumulate in fauna. Polychlorinated byphenyls (PCBs) on the other hand, are much more viscous than water (up to 700 times for 1254 blend) and hence do not move as quickly through permeable soils as TCE. Unlike TCE, PCBs also bioaccumulate and biomagnify and have caused substantial damage to aquatic food chains.

This part of this section identifies general documents on DNAPL chemical properties and fate and transport mechanisms. Cohen and Mercer (EPA 1993) also contains a summary table with selected data on DNAPL chemicals (Table A-1). Documents on characteristics specific to a chemical class can be found in the subsections listed to the right. A general discussion of DNAPL movement in the subsurface can be found in the Overview and Treatment Technologies sections.

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Cohen, R. and J. Mercer. 1993. DNAPL Site Evaluation, EPA 600/R-93/022. Office of Research and Development, U.S. EPA.

General DNAPL Chemistry and Behavior Documents

An Illustrated Handbook of DNAPL Transport and Fate in the Subsurface
Environment Agency, United Kingdom
R&D Publication 133, 2003

This publication provides an overview of DNAPLs, their fate and transport, characterization and remedial approaches, and appendices on specific issues such as the aperture required to stop DNAPL migration in fractured rock.

DNAPL and LNAPL Distributions in Soils; Experimental and Modeling Studies
Durnford, D., D. McWhorter, C. Miller, A. Swanson, F. Marinelli, and H. Trantham
October 1997, Report No.: AFRL-SR-BL-TR-98, NTIS: ADA342524

This report examines the subtle aspects of immiscible fluid behavior that can be manifested in large scale effects. It presents a method for modeling one-dimensional, multiphase flow through layered media. Finally it presents details on a two-dimensional pore scale model based on modified diffusion limited aggregation algorithm.

DNAPL Site Evaluation
Cohen, R. and J. Mercer. 1993.
EPA 600/R-93/022. Office of Research and Development, U.S. EPA

While dated, this publication has an extensive discussion on the theoretical aspects of DNAPL flow in saturated and unsaturated media. It provides a good basis for understanding why DNAPL source zones can form complex architectures.

Role of Aquitards in the Protection of Aquifers from Contamination: A "State of the Science" Report
Cherry, J., B. Parker, K. Bradbury, T. Eaton, M. Gotkowitz, D. Hart, and M.A. Borchardt
AWWA Research Foundation, 2004

This report discusses the flow of contaminated water and DNAPLs in aquitards and the forces that allow or prevent their penetrating into an underlying water supply.

Impact of Clay-DNAPL Interactions on Transport and Storage of Chlorinated Solvents in Low Permeability Zones
Demond , A., M. Goltz, and J. Huang.
SERDP Project ER-1737, 126 pp, 2015

The objective of this research was to examine clay-DNAPL waste interactions as a contributor to the accumulation of chlorinated compound contamination in subsurface clay lenses and layers. The results showed that contact between DNAPL waste and Na-smectitic clay materials caused a contraction of the clay's basal space, producing cracking, in a time frame on the order of weeks. The hypothesized mechanism is syneresis, involving the sorption of the surfactants from the waste onto the clay surface and the solvation of the surfactants' aggregates. Numerical simulations suggest that even a small amount of cracking, and the time-variable dissolution of the DNAPL stored in the cracks into the surrounding clay matrix, extends the remediation time by decades.

The Impact of DNAPL Source-Zone Architecture on Contaminant Mass Flux and Plume Evolution in Heterogeneous Porous Media
Brusseau, M.
SERDP Project ER-1614, 128 pp, Aug 2013

In bench- and field-scale investigations, investigators employed contaminant mass discharge as an integrative measure of the performance and effectiveness of remediation efforts. The standard approach of characterizing discharge at the source-zone scale was expanded to provide characterization at the plume scale, which was evaluated by examining the change in contaminant mass discharge associated with plume-scale pump and treat. This approach allows linking the impacts of source-zone remediation to effects on site-wide risk. Portions of the project comprised long-term studies conducted at the Tucson International Airport Area federal Superfund site in southern Arizona.

Abstracts

Interaction of Multiple in-Series DNAPL Residual Source Zones: Implications for Dissolution, Repartitioning and DNAPL Mobilization at Contaminated Industrial Sites
C. Serralde, M.O. Rivett, and J.W. Molson.
Groundwater Quality: Securing Groundwater Quality in Urban and Industrial Environments (Proc. 6th International Groundwater Quality Conference, Fremantle, Western Australia). IAHS Publ. 324, p 388-395, 2008
Abstract