Grantee Research Project Results

2001 Progress Report: Modeling Microbial PCB Degradation and Binding

EPA Grant Number: R826652
Title: Modeling Microbial PCB Degradation and Binding
Investigators: Balaz, Stefan
Institution: North Dakota State University Main Campus
EPA Project Officer: Aja, Hayley
Project Period: September 1, 1998 through August 31, 2001 (Extended to August 31, 2002)
Project Period Covered by this Report: September 1, 2001 through August 31, 2002
Project Amount: $375,000
RFA: Exploratory Research - Environmental Chemistry (1998) RFA Text | Recipients Lists
Research Category: Air , Safer Chemicals , Land and Waste Management , Sustainable and Healthy Communities

Objective:

The objective of this research project is to develop a complete kinetic description of the fate of individual PCB congeners in aqueous media and soil systems as determined by structure and physicochemical properties of congeners.

Progress Summary:

Partitioning between aqueous and nonpolar phases of biological systems is one of the factors governing the PCB fates. The process is most comfortably studied in defined model systems, in absence of any complicating interactions. We used a modified slow-stirring method (de Bruijn, et al., 1990) with increased throughput for kinetic experiments.

The partitioning was monitored for selected pure PCB congeners, present either in Delor 103, Delor 106, or both. In some cases, the partitioning for various initial PCB concentrations and binary PCB mixtures was studied. The 1?octanol/water partition coefficients Kow of individual PCB congeners in technical mixtures are lower than the respective values observed for pure congeners by up to 230 percent. The higher the overall hydrophobicity (chlorination) of the technical mixture, the lower the value of Kow.

To gain more insight, the 1?octanol concentrations in the aqueous phase also were analyzed, and the variations ranged from +25 percent to -28 percent of solubility. Complexity of the phenomenon is illustrated using partitioning of pure biphenyl and biphenyl/2-chlorobiphenyl mixture with varying initial biphenyl concentration in the experimental system (Figures 1 and 2).

Figure 1. The values of the 1-octanol/water partition coefficient Kow of biphenyl at different initial biphenyl concentration in the experimental system. Figure 2. The values of Kow for biphenyl (!) and 2?chlorobiphenyl (1 g/L; l) measured in mixture at shown initial biphenyl concentra-tions in the experimental system.

For pure biphenyl, the values of log Kow increase with concentration by about 0.5 unit. In the, biphenyl/2?chlorobiphenyl mixture, the changes are significantly smaller. The results indicate that different molecular species may be present in the phases of the experimental system. To characterize and quantitatively describe the fractions of the actual molecular species present during biphenyl and PCB partitioning in individual phases of the 1?octanol/water system, experiments on evaporation kinetics of biphenyl and PCBs from individual phases were initiated.

Future Activities:

Kinetics of evaporation from individual phases of the 1-octanol/water system for biphenyl and individual PCB congeners, both as pure and in mixtures, will be studied. The aim is to reveal the composition of the PCB solutions in terms of number of molecular species and their fractions. Partitioning in phospholipid monolayers that imitate biological membranes will be monitored and modeled. Interactions of PCB congeners with individual soil components and complete soils after a yearlong incubation will be studied by extraction. Degradation of PCB in soils will be monitored and described in a similar way as for the liquid media.

Journal Articles on this Report : 1 Displayed | Download in RIS Format

Publications Views
Other project views:	All 39 publications	18 publications in selected types	All 12 journal articles

Publications
Type	Citation	Project	Document Sources
Journal Article	Balaz S, Lukacova V. Subcellular pharmacokinetics and its potential for library focusing. Journal of Molecular Graphics & Modelling 2002;20(6):479-490.	R826652 (2001) R826652 (Final)	Abstract from PubMed Abstract: ScienceDirect-Abstract Exit

Supplemental Keywords:

quantitative structure-activity relationships, QSAR, quantitative structure-time-activity relationships, QSTAR, biosorption, hydrophobicity, lipophilicity., RFA, Air, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Waste, Toxics, National Recommended Water Quality, Remediation, Ecological Indicators, Ecological Risk Assessment, Ecosystem Protection, Environmental Chemistry, Ecosystem/Assessment/Indicators, Engineering, Chemistry, & Physics, Ecological Effects - Environmental Exposure & Risk, Bioavailability, Bioremediation, Physics, quantitative structure activity relationship, ecological effects, fate of PCB congeners, binding, microbial degradation, dioxin, bioremediation model, bioremediation of soils, human exposure, hydrophobic chemicals, soil, aquatic ecosystem, risk assessment, aquatic, biostabilization of PCBs, PCB, polychlorinated biphenyls, fate and transport, furans, decontamination of soil and water, enzymes, ecological exposure, chemical kinetics, bioacummulation, chemical transport, PCBs, physicochemical, biokinetic model, modeling

Relevant Websites:

http://www.ndsu.nodak.edu/instruct/balaz/pcbdegrb.htm Exit EPA icon

Progress and Final Reports:

Original Abstract

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.