Jump to main content.

Research Project Search
 Enter Search Term:
   
 NCER Advanced Search

1999 Progress Report: Bioavailability and Biostabilization of PCBs in Soil

EPA Grant Number: R825365
Title: Bioavailability and Biostabilization of PCBs in Soil
Investigators: Luthy, Richard G. , McNamara, Sean W.
Current Investigators: Luthy, Richard G. , Dzombak, David A. , McNamara, Sean W.
Institution: Carnegie Mellon University
EPA Project Officer: Lasat, Mitch
Project Period: January 1, 1997 through December 31, 1999
Project Period Covered by this Report: January 1, 1999 through December 31, 2000
Project Amount: $499,056
RFA: Bioremediation (1996)
Research Category: Hazardous Waste/Remediation

Description:

Objective:

The objective of this study is to develop an understanding of the relationships between the aqueous-phase concentrations and mobility of polychlorinated biphenyls (PCBs) in soils and the impact that biotreatment may have on reducing PCB availability in soils. The project is designed to enhance scientific knowledge for improved estimates of the potential for release of PCB congeners in aged soils and soil/sludge mixtures. This knowledge will provide further insight into the concept of biostabilization, which envisions that contaminated materials can be actively, and passively, biotreated to remove a large fraction of potentially mobile and bioavailable organic contaminants, thus reducing risk.

This work is being performed in collaboration with the Aluminum Company of America (Alcoa) in Pittsburgh, PA, and Massena, NY, and builds on prior studies between Carnegie Mellon University, Alcoa, and other institutions.

Progress Summary:

To address objectives of this project, several key questions were initially posed?the first being: "How can we measure the availability and mobility of PCBs in unsaturated field soils?" Here, the aqueous-phase concentrations of PCBs in aged soils are expected to be in the parts-per-billion range (µg PCBs/L H2O) and the water found in unsaturated soils is largely unavailable for sampling because it is held in tension within the soil matrix.

A new sampling device was developed to overcome these difficulties. This new device provides a way to obtain laboratory and field measurements of PCB congener availability and mobility within a soil column. The device was conceived during the first year of the project (1997) and refined in subsequent years (1998 and 1999) through a series of laboratory and field evaluations. Design considerations for the sampler included size, geometry, materials, hydraulic performance, cost, ease of deployment and retrieval, and compatibility with existing extraction and analysis techniques for PCBs. The formalized design for the new sampling device consists of a cylindrical porous stainless steel interface, a sorbent packing media (granular activated carbon), and a fiberglass wick. The device was designed to be installed in field soils by direct-push or a soil auger pilot-hole, thus minimizing installation requirements. The device uses the capillarity of a fiberglass wick and elevation potential to provide the necessary driving force to slowly sample water from unsaturated soils, thereby eliminating the need for an external power source. Water is drawn through the cylindrical interface, into and along the wick, and is collected to quantify the amount of water sampled (maintains a water balance). The annular space of the cylinder is packed with a sorbent media so that water that passes through the interface must pass through the sorbent media before entering the wick. Target constituents are retained on the sorbent media for chemical analysis (allows for a chemical mass balance with minimal losses) at the end of the sampling interval (weeks or months). Recovery of the PCBs is achieved using a simple, pressurized fluid extraction procedure. Overall, the new sampling device is designed to provide an integrated field estimate of the time-averaged mass and volumetric flux rates of PCBs, or other hydrophobic organic compounds, in the soil column.

Future Activities:

The work plan for the final project year is designed to evaluate the key question posed in the initial grant proposal: "For aged soils that have undergone active biotreatment, what is the rate of release of residual PCBs?" This question is posed in the context of observed removal and/or biodegradation rates of PCBs in field soils with the implication that biostabilization may lead to a viable remedial endpoint if removal rates are equal to or greater than release rates.

The sampling device will be tested primarily in the laboratory in various soil columns of PCB-impacted materials. Field demonstrations may occur on a limited basis. The materials tested may include aged site soils and/or aged waste-oil sludge mix bulked with clean sand, depending on the quantities required for each test. The sampler/soil column tests will be supplemented by traditional column experiments and batch equilibrium studies. The experiments will be designed to assess the viability of using the sampling device as a simple in situ method for future field studies on PCB availability. The results from this year's experiments will be assessed in relation to the substantial database of PCB biotreatment information (e.g., removal rates, biodegradation rates, equilibrium-partitioning concentrations) that has been compiled during current and previous projects related to the same materials. The results from this study will help to solidify our understanding of the relationship between the residual release of PCBs and the effects that biotreatment may have on the availability and mobility of PCBs in soils.

The final report for this project will be submitted in January 2001 and the results are expected to be presented at The Sixth International Symposium on In Situ and On-Site Bioremediation in the spring of 2001 (the actual conference location and date are not set yet).

Journal Articles:

No journal articles submitted with this report: View all 7 publications for this project

Supplemental Keywords:

PCBs, leachate, soil, chemical transport, bioremediation, bioavailability, biostabilization. , Ecosystem Protection/Environmental Exposure & Risk, Toxics, Water, Scientific Discipline, Waste, RFA, chemical mixtures, Remediation, Ecosystem/Assessment/Indicators, Biology, HAPS, Bioavailability, Chemistry, Environmental Chemistry, Chemical Mixtures - Environmental Exposure & Risk, Contaminated Sediments, Bioremediation, Engineering, biostabilization of PCBs, risk assessment, biodegradation, environmentally acceptable endpoints, fate, fate and transport, land biotreatment, chemical transport, kinetic studies, PCBs, contaminated sediment, contaminant transport, models, hydraulic oils, contaminants in soil, contaminated soils, bioremediation of soils, physicochemical, chemical contaminants, vadose zone
Relevant Websites:

http://www.ce.cmu.edu/~mcnamara/RESEARCH/overview.htm Exit EPA icon
http://www.ce.cmu.edu/~rl10/ Exit EPA icon
http://www.ce.cmu.edu/EnvInst/ Exit EPA icon

Progress and Final Reports:
1997 Progress Report
1998 Progress Report
Original Abstract
Final Report

Top of page

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

Local Navigation

Jump to main content.