Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


INEEL geoscientist to present NAPL contaminant modeling advance at AGU Meeting


DOE News Release Embargoed for release December 6, 2002 INEEL geoscientist to present NAPL contaminant modeling advance at AGU Meeting By modifying the mathematical theory describing the relationship between permeability, saturation, and pressure in a multiple fluid system, researchers can now more accurately predict the movement of non-aqueous phase liquid (NAPL) contaminants in the subsurface. New calculations account for residual NAPL that remains in the vadose zone-forming a long-term source for groundwater contamination, and also explain how part of this residue can be flushed into groundwater during rainstorms or flooding.

This research, funded through U.S. Department of Energy’s Idaho National Engineering and Environmental Laboratory’s Subsurface Science Initiative (SSI), supports the DOE’s mission in environmental science.

Hydrologist Robert Lenhard of the INEEL, has resolved a critical contamination modeling problem by refining current constitutive theory - theory describing relations among fluid relative permeabilities, saturations, and pressures. His new model predicts the distribution of residual NAPL based on the prior fluid wetting and drying cycles in the subsurface. Lenhard will present his work at the American Geophysical Union meeting in San Francisco, CA, on December 8, 2002 during the Hydrology session.

"If you run existing multiphase flow models long enough, the results show that NAPL will completely drain from a vadose zone, which is contrary to field and experimental observations" said Lenhard. Better constitutive theory is needed for developing accurate computer models. "The lack of well-founded constitutive theory may be the foremost element impeding the development of accurate predictive multiphase flow models," he adds.

Lenhard’s modeling advance represents a shift in researchers’ conceptual understanding of NAPL behavior by recognizing that some NAPL becomes immobilized in pore spaces or as thin films on soil solids. Nowadays, subsurface contamination by NAPLs is almost ubiquitous. As a result of DOE’s efforts to develop, test, manufacture, and maintain nuclear weapons for national security purposes, the DOE has very complex contamination problems with NAPLs that are denser than water. Additionally, an estimated 60 percent of Superfund (DOE, industrial and municipal) sites have NAPL contamination.

Lenhard and colleagues conducted pilot-scale (mesoscale) experiments in the laboratory to study how NAPLs behave under different conditions. NAPLs can move through the vadose zone as liquid, vapor, or carried along as dissolved droplets within a moving stream of water. His experiments indicate that residual NAPL will generate pulses of contamination during heavy rainstorms or flooding, especially at arid sites. A better understanding of how residual NAPLs contribute to contamination could influence environmental remediation choices.

Most NAPLs, such as fuels and degreasing solvents, are petroleum based. Predicting the movement of NAPLs in the subsurface is challenging because NAPLs can be either lighter or heavier than water and don’t mix with water. Light NAPLs accumulate above the water table, and can depress the water-saturated region. Heavy or dense NAPLs sink below the water table and are very difficult to locate and clean up.

In order to predict the subsurface movement of multiple fluids, it is very important to know how the fluids are distributed throughout the pore spaces. The sizes of the pores containing the fluids will affect how rapidly these fluids can move downward to groundwater. If the fluids contain compounds harmful to humans and the environment, then by knowing how fast and in what quantities these compounds will reach the groundwater, effective remediation strategies can be developed using computer modeling. Lenhard has spent much of his career developing new techniques for measuring subsurface NAPL behavior and developing mathematical models for describing multi-fluid flow constitutive theory, which is needed to predict the flow behavior of multiple fluids in porous media. He is a leader in multiphse flow constitutive theory and his models are used worldwide by many scientists to predict air-NAPL-water flow behavior.

Martinus Oostrum of the DOE’s Pacific Northwest National Laboratory, who has worked with Lenhard, plans to use Lenhard’s new methodology to enhance the accuracy of the STOMP model- a numerical computer program for predicting Subsurface Transport Over Multiple Phases (STOMP). It is expected that the improved computer model will be used to help address NAPL contamination at DOE sites. Lenhard is also interested in employing his constitutive models in other multiphase flow

Deborah Hill | INEEL
Further information:

More articles from Earth Sciences:

nachricht Wandering greenhouse gas
16.03.2018 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

nachricht Unique Insights into the Antarctic Ice Shelf System
14.03.2018 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

Im Focus: Radar for navigation support from autonomous flying drones

At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.

Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

International Virtual Reality Conference “IEEE VR 2018” comes to Reutlingen, Germany

08.03.2018 | Event News

Latest News

Wandering greenhouse gas

16.03.2018 | Earth Sciences

'Frequency combs' ID chemicals within the mid-infrared spectral region

16.03.2018 | Physics and Astronomy

Biologists unravel another mystery of what makes DNA go 'loopy'

16.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>