Grantee Research Project Results
1997 Progress Report: Bioavailability of Aromatic Hydrocarbons in Saturated Porous Media: The Effects of Chemical Aging and Mass Transfer
EPA Grant Number: R825406Title: Bioavailability of Aromatic Hydrocarbons in Saturated Porous Media: The Effects of Chemical Aging and Mass Transfer
Investigators: Bouwer, Edward J. , Ball, William P.
Institution: The Johns Hopkins University
EPA Project Officer: Chung, Serena
Project Period: December 6, 1996 through December 5, 1999 (Extended to December 5, 2001)
Project Period Covered by this Report: December 6, 1996 through December 5, 1997
Project Amount: $439,725
RFA: Environmental Fate and Treatment of Toxics and Hazardous Wastes (1996) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management , Safer Chemicals
Objective:
The primary objective of this research is to evaluate, quantify, and model the effects of sorption/desorption processes and diffusional mass transfer on the biodegradation of hydrophobic organic contaminants (HOCs) under conditions where aquifer solids and impermeable aggregates of such solids have been exposed to long-term contamination (aging). Furthermore, it is the objective of this research to predict the intrinsic rates of bioremediation of aged compounds based on sorbent and sorbate properties using a coupled desorption/biodegradation model.This research consists of abiotic and biotic batch and column studies to elucidate the effects of sorption/desorption processes on contaminant bioavailability. An experimental matrix of batch and column work (incorporating both batch abiotic and biotic studies) has been established on the basis of work with five different natural sorbents and the following three sorbates: benzene, naphthalene and phenanthrene. The sorbents are organic-free quartz sand (Ottawa sand), a microporous aquifer material from Ontario, Canada (Borden sand), A-horizon sediments from Bozeman, Montana, and two aquitard materials obtained from Dover Air Force Base in Dover, Delaware (OSCL-orange silty-clay-loam and DGSL-dark gray silt loam). Research progress to date includes sediment characterization, initiation of batch aging studies with all sorbents and sorbates, batch sorption studies with phenanthrene and naphthalene on OSCL, DGSL, and Bozeman sediments, batch liquid enrichment mineralization studies using naphthalene, phenanthrene and benzene as primary substrates, batch sediment mineralization studies with naphthalene and Ottawa sand and Bozeman sediments, column set-up design and initiation of construction, and application of fate and transport models under conditions of the column experiments.
Progress Summary:
Solids characterization included soil pH, organic carbon content, solid density measurements, porosity measurements, grain size distribution, cation exchange capacity, mineralogy, inter and intraparticle surface area, and bulk density. Batch sorption results completed to date are summarized in Table 1.Table 1 - Summary of Sorption Isotherm Data
| Sorbent | Naphthalene | Phenanthrene |
| Kf | 1/n | Avg. Kd (L/Kg) | Kf | 1/n | Avg. Kd (L/Kg) | |
| Ottawa Sand | TBD | TBD | TBD | TBD | TBD | TBD |
| Borden Sand | TBD | TBD | TBD | TBD | TBD | TBD |
| DGSL | 137 | 0.87 | 53.1 | 3540 | 0.78 | 1006.2 |
| OSCL | 0.80 | 0. 98 | 0.72 | 27 | 0.88 | 13.6 |
| Bozeman Sediment | 6.35 | 0.99 | 6.43 | NA | NA | NA |
| NA = Not analyzed, TBD = To be determined, |
Batch degradation and mineralization studies without sediments were undertaken to estimate intrinsic biokinetic rate parameters for substrate utilization. Zero-order, first-order and Monod models were fit to the observed data. These results are summarized in Table 2.
Table 2 - Summary of Biokinetic Parameters
| Compound | kbio (mg/L-hr) | kbio (hr-1) | µmax (hr-1) | Yobs | Ks (mg/L) |
| Benzene | 0.0056 - 0.183 | 0.307 -0.655 | 0.127 | 0.35 | 0.010 |
| Naphthalene | 0.633 - 0.966 | 0.216-1.199 | 0.093 | 0.45 | 0.202 |
| Phenanthrene | 0.0127 -0.0137 | 0.108 - 0.281 | 0.086 | 0.80 | 0.040 |
Laboratory soil columns have been constructed using Borden sand and Ottawa sand as the porous media. An advective/dispersive/sorption/diffusion Fortran-based computer model has been utilized to simulate solute transport, estimate column breakthrough times, and aid in the construction of the experimental systems. The model can be adapted to describe different processes of diffusion from regions of immobile water including diffusion in spheres, diffusion from a macropore into an annulus, and first-order mass transfer.
Future Activities:
Future work will include additional batch sorption isotherm experiments, sorption and desorption rate studies, sediment mineralization studies and column aging experiments.Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 11 publications | 3 publications in selected types | All 3 journal articles |
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Zhang WX, Bouwer EJ, Ball WP. Bioavailability of hydrophobic organic contaminants: Effects and implications of sorption-related mass transfer on bioremediation. Ground Water Monitoring and Remediation 1998;18(1):126-138. |
R825406 (1997) R825406 (1998) R825406 (1999) R825406 (2000) R825406 (Final) |
not available |
Supplemental Keywords:
bioavailability, sorption, mass transfer, aging, intrinsic bioremediation, Scientific Discipline, Toxics, Waste, Ecosystem Protection/Environmental Exposure & Risk, Bioavailability, National Recommended Water Quality, Environmental Chemistry, HAPS, Chemistry, Fate & Transport, Bioremediation, Ecological Risk Assessment, fate and transport, hydrocarbon, bioremediation model, Naphthalene, aquifer sediments, biodegradation, field studies, sorption kinetics, chemical speciation, saturated porous material, adsorption, chemical transport, kinetic studies, mass transfer, soils, toxicity, contaminants in soil, hazardous waste cleanup, soil characterization, saturated porous media, 1, 2-Dichlorobenzene, environmental toxicant, harmful environmental agents, mobility, aging, biodegradation of hydrophobic organic contaminants, contaminated aquifers, Phenanthrene, groundwater, hydrocarbon desorption kinetics, transportProgress 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.