Grantee Research Project Results
Final Report: Bioavailability of Organic Contaminants in Estuarine Sediments to Microbes and Benthic Animals
EPA Grant Number: R825303Title: Bioavailability of Organic Contaminants in Estuarine Sediments to Microbes and Benthic Animals
Investigators: Taghon, Gary L. , Rockne, Karl J. , Shor, Leslie M. , Kosson, David S.
Institution: Rutgers University - New Brunswick
EPA Project Officer: Aja, Hayley
Project Period: October 1, 1996 through September 30, 1999
Project Amount: $496,239
RFA: DOE/EPA/NSF/ONR Joint Program on Bioremediation (1996) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management
Objective:
The objective of this research project was to determine the bioavailability of sediment-associated contaminants to microbes. Most often, "bioavailability" refers to the fraction of a contaminant that may enter into biological processes. Alternatively, bioavailability can refer to the flux of contaminants.
When defined as a flux, bioavailability will be a function of the local environmental conditions, including contaminant interactions with the solid matrix, concentration gradients, pH, redox potential, and solution composition. If, under a given set of conditions, the resulting flux is below the minimum flux required by the organism for uptake or utilization, then the contaminant would not be bioavailable. Understanding and quantifying the relationship between the physical and chemical characteristics of sediments and fluxes of contaminants to microbial and animal communities is essential for prudent risk-based decision making.
We focused our study on polycyclic aromatic hydrocarbons (PAHs), an important class of organic contaminants in many environmental matrices. The specific objectives of this project were to:
(1) Quantify the flux of PAHs from sediment under abiotic conditions.
(2) Examine the effect of microbial activity on PAH biodegradation rate and extent.
(3) Examine the impact of aging on PAH fluxes under abiotic conditions, and
on microbial
biodegradation rate and extent.
(4) Mathematically model bioavailability of PAHs based on contaminant flux
under abiotic
and biotic conditions.
Summary/Accomplishments (Outputs/Outcomes):
Roles of sediment structure and organic carbon properties on sequestration and release of PAHs in weathered sediment PAH-contaminated sediments from Piles Creek (PC) and Newtown Creek (NC) in the New York/New Jersey Harbor estuary were separated into size fractions and further separated into low (<1.7 g cm-3) and high (>1.7 g cm-3) density fractions.
The fractionated sediments were characterized for carbon content, pore structure, surface area, and PAH concentration. Most PAHs (50-80 percent) in both sediments were associated with the low-density fraction, which represented only 3-15 percent of total sediment mass, at levels greater than expected based on equilibrium partitioning. PC low-density sediment had 10 times greater organic carbon-normalized equilibrium partitioning coefficient (Koc) than the other size fractions and whole sediment. Characterization of the sediment organic matter suggested that the preferential sequestration observed in PC sediment was not correlated with soot carbon, but was likely due to the presence of detrital plant debris, an important food source for benthic animals.
Fractional PAH desorption from whole PC sediment was significantly higher than from NC sediment after 3 months. For both sediments, a smaller percentage of the total PAHs were desorbed from the low-density fraction. However, because PAH concentrations were greatly elevated in these fractions, more PAH mass was desorbed than from the corresponding bulk and high-density fractions. These results demonstrate that PAHs were preferentially sequestered in a separable, low-density fraction at levels not predictable by equilibrium partitioning theory.
Further, the low-density fraction apparently controlled whole-sediment PAH release. Although plant debris appeared to be an important sorbent for PAHs, this material more readily released PAHs into the aqueous phase. Desorption kinetics for field-aged PAHs from sediments. Sediment desorption kinetics for field-aged PAHs with a log octanol-water partition coefficient greater than six were well described by a one-domain diffusion model that assumes PAHs are initially uniformly distributed throughout spherical sediment aggregates. PAH hydrophobicity and sediment specific surface area were the parameters most strongly correlated with the magnitude of observed diffusivity for the one-domain model. For less hydrophobic compounds, two-domain diffusion modeling suggests that a large and predictable fraction of PAHs desorb via a relatively fast macro/mesopore diffusion mechanism. This fast-domain diffusivity was about two-orders of magnitude larger than the slow-domain diffusivity, depending on PAH hydrophobicity, and could be estimated by readily obtainable physical and chemical parameters. The slow-domain diffusivity was not a strong function of PAH structure/activity properties, but was significantly correlated with sediment surface area and sediment organic matter properties. Despite low aqueous solubility of PAHs, macro/mesopore diffusion may be an important mechanism controlling mass transport and bioavailability of the most readily and extensively desorbed PAHs in estuarine sediments.
Enrichment, isolation, identification, and characterization of a PAH-degrading bacterium. A bacterium, Mycobacterium sp. strain PC01, was isolated from Piles Creek sediment. The bacterium was verified as a species of Mycobacterium based on its 16s rDNA sequence and acid-alcohol fastness (Ziehl-Neelsen) staining. Strain PC01 has a highly hydrophobic cell surface, and the adherence of the bacterium to phenanthrene crystals was observed microscopically. Strain PC01 preferentially grows on low volatility, higher molecular weight PAHs and alkanes such as fluoranthene, pyrene, hexadecane, and heptadecane. The degradation of phenanthrene and pyrene in Piles Creek and Newtown Creek sediments varied, suggesting that the type of sediment might affect bacterial degradation of PAHs. No difference in either rate or extent of mineralization of phenanthrene was evident when phenanthrene was provided in crystalline form or freshly adsorbed to the sediment. This might result from the slow sorption of phenanthrene to the sediment.
We investigated the effect of aging on the bioavailability of phenanthrene to Mycobacterium strain PC01 in low- and high-organic matter sediments. The bioavailability of phenanthrene was determined in both low-and high-organic matter sediments over a 384-day aging period. Bulk sediment and plant fragments collected from Piles Creek served as low- and high-organic matter sediment in this study, respectively. The bioavailability of phenanthrene was evaluated by the rate and extent of mineralization of spiked (radiolabeled and non-radiolabeled) phenanthrene by Mycobacterium sp. strain PC01, isolated from Piles Creek. The data suggest that the extent of phenanthrene mineralization was greater in the high-organic matter sediment than in the low-organic matter sediment when phenanthrene had aged for 0 and 139 days. After aging for 251 days, the extent of mineralization decreased significantly in both high- and low-organic matter sediment though the decrease was less in the latter. Compared to nonaged phenanthrene, the extent of mineralization of phenanthrene that had aged for 384 days decreased 10 and 44 percent in the low- and high-organic matter sediment, respectively, indicating that organic matter may have an important effect on the bioavailability of phenanthrene.
We also investigated the bioavailability of field-aged PAHs in whole and density-fractionated sediments. Biodegradation kinetics for three- and four-ring PAHs by a pure culture sediment isolate, Mycobacterium sp. strain PC01, were measured in whole and density-fractionated estuarine sediments. They were further compared with biodegradation kinetics in a system without mass transport limitations, and with abiotic desorption kinetics. The results indicated that mass transport limitations and not differences in intrinsic bacterial biodegradation capacity, were most important in controlling rate and extent of biodegradation. Specifically, achievable extent of biodegradation may be limited by the fraction of desorbable PAHs in the fast-diffusion regime.
A closed-form model describing rapid aqueous-phase PAH diffusion through the macro/mesopore network of sediment aggregates followed by first-order biodegradation in the bulk aqueous phase effectively predicted biodegradation kinetics for several field-aged PAHs in two estuarine sediments. Despite low aqueous solubility of PAHs, macro/mesopore diffusion may be an important mechanism controlling mass transport and bioavailability of the most readily and extensively desorbed PAHs in sediments.
Journal Articles on this Report : 9 Displayed | Download in RIS Format
Other project views: | All 26 publications | 9 publications in selected types | All 9 journal articles |
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Type | Citation | ||
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Liang W, Taghon GL, Rockne KJ, Kosson DS, Shor LM, Young LY. Effects of the polychaete, Capitella sp. I, on the bioavailability of polycyclic aromatic hydrocarbons (PAHs) to microorganisms. Marine Environment Research. |
R825303 (Final) |
not available |
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Liang W, Rockne KJ, Shor LM, Taghon GL, Kosson DS, Young LY. Enrichment, isolation, identification and characterization of a PAH-degrading bacterium. FEMS Microbiology Ecology. |
R825303 (Final) |
not available |
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Liang W, Rockne KJ, Shor LM, Taghon GL, Kosson DS, Young LY. The effect of aging on the bioavailability of phenanthrene in both low- and high-organic matter sediments. Environmental Microbiology. |
R825303 (Final) |
not available |
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Rockne KJ, Taghon GL, et al. Sequestration of PAHs in size- and density-fractionated estuarine sediments. In situ and On-site Bioremediation 1999;5(8):191-196. |
R825303 (Final) |
not available |
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Rockne KJ, Shor LM, Young LY, Taghon GL, Kosson DS. Distributed sequestration and release of PAHs in weathered sediment: The role of sediment structure and organic carbon properties. Environmental Science & Technology 2002;36(12):2636-2644. |
R825303 (Final) |
not available |
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Rockne KJ, Liang W, Makkar RS, Young LY, Taghon GL. Culturability of E. coli in various density gradient media: implications for density-fractionation of soils and sediments. Applied and Environment Microbiology. |
R825303 (Final) |
not available |
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Rockne KJ, Taghon GL, Kosson DS. Pore structure of soot deposits from several combustion sources. Chemosphere (in press). |
R825303 (1999) R825303 (Final) |
not available |
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Shor LM, Rockne KJ, Taghon GL, Young LY, Kosson DS. Desorption kinetics for field-aged polycyclic aromatic hydrocarbons from sediments. Environmental Science & Technology 2003;37(8):1535-1544. |
R825303 (Final) |
not available |
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Shor LM, Liang W, Rockne KJ, Young LY, Taghon GL, Kosson DS. Intra-aggregate mass transport-limited bioavailability of polycyclic aromatic hydrocarbons to Mycobacterium strain PC01. Environmental Science & Technology 2003;37(8):1545-1552. |
R825303 (Final) |
Exit Exit |
Supplemental Keywords:
sediments, estuary, adsorption, chemical transport, risk assessment, bioavailability, PAHs, PNAs, bacteria, bioremediation, environmental chemistry, biology, engineering, ecology, modeling, analytical, northeast, Atlantic coast, New Jersey, NJ, New York, NY, industry., RFA, Scientific Discipline, Geographic Area, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, Bioavailability, Ecology, Water & Watershed, Contaminated Sediments, exploratory research environmental biology, Ecosystem/Assessment/Indicators, Chemical Mixtures - Environmental Exposure & Risk, Ecosystem Protection, Chemistry, State, Ecological Effects - Environmental Exposure & Risk, Environmental Microbiology, Ecological Effects - Human Health, Biochemistry, Bioremediation, Biology, Watersheds, Ecological Indicators, fate and transport, risk assessment, microbiology, risk-based decisions, contaminant transport, contaminated sites, benthic animals, contaminated sediment, aquifer sediments, chemical transport, kinetic studies, New Jersey (NJ), microbes, risk analysis, bioremediation of soils, contaminants in soil, mixed organic contaminants, soil characterization, aquatic ecosystems, contaminant release, contaminated aquifers, sediments, exposure assessmentRelevant Websites:
http://marine.rutgers.edu/biocomplexity/ Exit
Progress 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.