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The Influence of Nanoporosity in Soils from Contaminated Sites on Hydrocarbon Desorption Kinetics and Bioavailability

EPA Grant Number: R825959
Title: The Influence of Nanoporosity in Soils from Contaminated Sites on Hydrocarbon Desorption Kinetics and Bioavailability
Investigators: Pignatello, Joseph J. , Neimark, Alexander V.
Institution: Connecticut Agricultural Experiment Station , Princeton University
Current Institution: Connecticut Agricultural Experiment Station , Tri / Princeton
EPA Project Officer: Lasat, Mitch
Project Period: January 1, 1998 through December 31, 2000
Project Amount: $436,399
RFA: Bioremediation (1997)
Research Category: Hazardous Waste/Remediation

Description:

Bioremediation of soils and sediments containing organic compounds is often rate-limited by desorption. The underlying physical/chemical mechanisms responsible for desorption resistance are poorly understood. We hypothesize that desorption resistance is due to severely hindered diffusion in and out of subnanometer size pores. These pores are located both in the fixed mineral pore system and in soil organic matter. The objectives are to develop methodology to characterize the nanoporosity of a number of soils and aquifer sediments of current interest, and then to determine the relationship, if any, between nanoporosity and certain physical-chemical and biological availability parameters.

Approach:

The test compounds will be the aromatic hydrocarbons, toluene and phenanthrene. Soils to be investigated will be collected from several contaminated sites around the country. The proposed methodology for determining the nanoporosity of soil materials is based on obtaining the CO2 adsorption isotherm at a suitable temperature and applying molecular level theoretical models such as Density Functional Theory and Monte Carlo simulations to determine the pore size distribution from the isotherms. Chemical availability will be established by measuring the diffusion coefficient and the magnitude of an "irreversibly sorbed fraction" in batch desorption experiments by an in situ trap technique. Bioavailability will be measured as the rate and extent of mineralization by bacterial degraders. Effects of soil alteration will be examined, including progressive stripping of organic matter (H2O2 oxidation or alkaline extraction), wet-drying cycling, and competitive displacement by a second solute. These alterations were shown in preliminary tests to affect hydrocarbon availability.

Expected Results:

The results of this project will give insight into the underlying causes of resistant sorption and reduced bioavailability and will provide an analytical tool for measuring the potential of a soil to generate resistant fractions. This proposal thus fulfills a goal of the Joint Program on Bioremediation to further our fundamental understanding of the chemical, physical, and biological processes influencing the bioavailability and release of chemicals in soil and sediments under natural conditions. By lending insight into mechanisms of sequestration of chemicals, the results may also open up new approaches to remediation of contaminated sites. The methodology for characterizing soil particle nanoporosity will be widely applicable to nanoporous material in general.

Publications and Presentations:

Publications have been submitted on this project: View all 77 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 19 journal articles for this project

Supplemental Keywords:

sorption kinetics, competitive sorption, PAH, bacteria, organics, groundwater, hydrocarbons, characterization of porous materials. , Ecosystem Protection/Environmental Exposure & Risk, Water, Scientific Discipline, Waste, Geology, Microbiology, Bioavailability, Chemistry, Environmental Engineering, Environmental Microbiology, Environmental Chemistry, Contaminated Sediments, Geochemistry, Bioremediation, sorption kinetics, groundwater, Phenanthrene, hydrocarbon desorption kinetics, contaminated sediment, Toluene, bioremediation of soils, PAH, soil characterization, nonoporosity, aquifer sediments, sediments, sorption, contaminated sites

Progress and Final Reports:
1998 Progress Report
1999 Progress Report
Final Report

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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.

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