Grantee Research Project Results
1998 Progress Report: A Comprehensive Investigation of the Effects of Organic Geochemistry on the Sorption-Desorption, Sequestration, and Bioavailability of Mixed Organic Contaminants in Subsurface Systems
EPA Grant Number: R825962Title: A Comprehensive Investigation of the Effects of Organic Geochemistry on the Sorption-Desorption, Sequestration, and Bioavailability of Mixed Organic Contaminants in Subsurface Systems
Investigators: Weber, Walter J.
Institution: University of Michigan
EPA Project Officer: Aja, Hayley
Project Period: January 1, 1998 through December 31, 2000
Project Period Covered by this Report: January 1, 1998 through December 31, 1999
Project Amount: $440,748
RFA: EPA/DOE/NSF/ONR - Joint Program On Bioremediation (1997) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management
Objective:
The objective of this research project is to obtain an understanding of mechanisms that lead to slow desorption and contaminant sequestration in subsurface soil and sediment systems, and an understanding of the implications of sorption-desorption hysteresis on contaminant mobility and bioavailability. This objective will be achieved through systematic studies designed to determine the effects of soil/sediment organic matter (SOM) in multicontaminant systems on: hydrophobic organic chemical (HOC) sorption-desorption rates, hysteresis, and sequestration of the subcritical water extractability of sorbed HOCs from soils; the bioavailability of sorbed HOCs and the relationships of their desorption and subcritical water extractability to bioavailability; and the effects of cumulative solute residence time (i.e., "aging") on each of the above.Progress Summary:
Soils that had been previously characterized in our laboratories have been used to evaluate relationships between SOM and sorption-desorption rates and hysteresis. During the last year, relationships between the bioavailability of sorbed phenanthrene and the SOM of the geosorbents were investigated.
Sorption and desorption equilibria, rates of desorption, and rates of biological mineralization of phenanthrene with respect to three different types of geosorbents were measured. The chemical nature of the organic matter associated with each geosorbent was characterized using solid-state 13C-NMR spectrometry. The results of these studies reveal that both the desorption behavior and the microbial bioavailability of the sorbed contaminant are dependent upon the physicochemical character of the geosorbent organic matter. The more reduced and condensed this organic matter, the greater the extent of sorption-desorption hysteresis, the slower the desorption rate, and the less readily bioavailable the sorbed contaminant.
The bioavailability of phenanthrene sorbed to geosorbents was evaluated as a function of soil organic matter and aging period. The geosorbents were not sterilized before conducting the experiments. The samples were prepared so that the equilibrium aqueous phase concentration of total phenanthrene was 800 g/L. The geosorbents were first equilibrated for 1 month with unlabeled and radiolabeled phenanthrene. They were aged for an additional 1 to 3 months. After aging, the soil and solution were transferred to slurry reactors and inoculated with Pseudomonas cepacia CRE7, a phenanthrene-degrading microorganism. Mineralization profiles obtained from this research show that phenanthrene sorbed to the younger geosorbents (Michigan peat and Chelsea soil) degrades at a much faster rate initially than that sorbed to the older geosorbent (Lachine shale). The degradation of phenanthrene in the younger geosorbents also slows and nearly ceases after the initial degradation. On the other hand, the degradation of phenanthrene in the older soil continues at a nearly constant rate after the initial degradation. Significant differences between the two aging periods were not found in these experiments.
Future Activities:
Future activities for this research project include: comparison of the microbial degradation kinetics in the presence and absence of various types of well-characterized geosorbents; commencement of a new set of sorption-desorption and bioavailability experiments using phenanthrene in both sterilized and nonsterilized soil to determine the effects of indigenous microorganisms; commencement of sorption-desorption and bioavailability experiments with an equimolar mixture of phenanthrene and three other contaminants; and development of experiments to determine the sequestration and transformation of phenanthrene metabolites.Journal Articles:
No journal articles submitted with this report: View all 13 publications for this projectSupplemental Keywords:
contaminant mobility, alternative remediation endpoints, biotransformation of contaminants., RFA, Scientific Discipline, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Bioavailability, Contaminated Sediments, exploratory research environmental biology, Environmental Chemistry, Ecosystem/Assessment/Indicators, Chemical Mixtures - Environmental Exposure & Risk, Ecosystem Protection, Health Risk Assessment, Chemistry, chemical mixtures, Ecological Effects - Environmental Exposure & Risk, Bioremediation, Biology, Geology, Environmental Engineering, risk assessment, fate and transport, risk-based decisions, contaminated sediment, chemical transport, subsurface systems, mixed organic contaminants, geochemistry, soil characterization, contaminant release, hydrocarbons, exposure assessment, chlorinated solvents, hydrophobic organic contaminantsProgress and Final Reports:
Original AbstractThe 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.