Grantee Research Project Results
1999 Progress 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. , Kosson, David S. , Young, Lily Y.
Current 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 Period Covered by this Report: October 1, 1998 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 goal of this project is to determine the bioavailability of sediment-associated organic contaminants to microbes and benthic animals. Bioavailability can be defined as the flux of contaminants to the biota. In this case, the flux observed will be a function of the local environmental conditions. If the resulting flux is below the minimum required by the organism for uptake or utilization, then the contaminant would be considered not bioavailable under the conditions examined. 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.Progress Summary:
Two sampling locations in the New York Harbor Estuary were chosen because they possess vastly different physical, chemical, and biological characteristics. Piles Creek, a tributary of the Arthur Kill, runs through a marshy area with abundant emergent vegetation. Newtown Creek is an industrial waterway in Queens, New York. Both sites had been exposed to polycyclic aromatic hydrocarbons (PAHs) for decades. The sediments were fractionated into five size classes (>500, 500-300, 300-125, 125-63, and <63 µm) by wet sieving in clean seawater. The low- and high-density fractions of each of these samples plus whole sediment were separated by equilibrium flotation/settling in a saturated CsCl (p=1.8 g/ml) (see Rockne, et al., 1999). The size- and density-separation resulted in 18 fractions from each site, for a total of 36 subsamples.
Chemical Characterization. On each fraction, total organic carbon was measured. PAHs were extracted from all sediment fractions using a novel hot acetonitrile extraction procedure. Sediments were dewatered by centrifugation (8000 g) and extracted in sealed Teflon Oak Ridge centrifuge tubes with boiling acetonitrile (85?C, 120 min) in an ultrasonic bath. This procedure was verified to provide high extraction efficiency with a National Institute of Standards and Technology (NIST) PAH-contaminated sediment standard. PAHs in the acetonitrile extract were analyzed by high performance liquid chromatography (HPLC) with fluorescence and photodiode array detection/identification.
Physical Characterization. Surface area, pore size distribution, and particle size analysis were measured by nitrogen adsorption/BET, Hg-Intrusion, and X-ray sedigraphy, respectively, as described (Rockne et al. 1999).
Abiotic PAH-Desorption. Desorption rates were measured using a modified procedure based on the method of Cornelissen et al. (1997). Poisoned sediment (HgCl2) was placed in glass separatory funnels and incubated with clean Tenax beads. At time intervals (30 min; 1.5, 3, 6, and 12 hr; 1, 2, 5, and 12 d; 1 and 3 mo), the sediment was separated from the Tenax and placed in a new separatory funnel with fresh Tenax. The Tenax beads were extracted with hexane (15 min, 150 rpm) and the extract was analyzed for PAHs as described above.
Single-Point Equilibrium Partitioning. Using the field-aged sediments, we were unable to vary the liquid/solid ratio in realistic fashion to provide multiple equilibrium distribution points, and therefore, we could only measure single-point aqueous/sediment partitioning coefficients. Sediment (1-10 g dry wt) was added to filtered (0.45 µm) seawater (4 L, poisoned with HgCl2) in clean 4 L amber solvent bottles. After incubation (25?C, 3 mo), the supernatant was decanted through solid-phase extraction filtration disks (3 M empore), which were extracted into hexane, concentrated, and analyzed as described above. This resulted in a 1500- to 2000-fold concentration of PAHs from the aqueous phase.
Bacterial Degradation of PAHs. We have isolated an aerobic bacterium from Piles Creek. Strain PC01 has been identified as a fast-growing Mycobacterium species that can use a wide range of PAHs as substrates (pyrene, phenanthrene, anthracene, benzo[a]anthracene, chrysene). Degradation rates of freshly added PAHs and PAHs historically present in field sediments have been determined.
The results of our research are discussed below.
Newtown Creek sediment is characterized by very fine particles (most particles smaller than 20 mm), low vascular plant debris, and 50-100 mg/kg of the 16 Environmental Protection Agency (EPA) priority PAHs. Piles Creek sediment was more graded and relatively more coarse-grained than Newtown Creek sediment. Piles Creek sediment also had much higher vascular plant debris than Newtown Creek and 100-200 mg/kg total PAHs.
PAH Distribution. The concentration of PAHs in the sediment varied
with size and density fraction. Piles Creek sediment had higher PAH
concentrations in the coarse material, while
Newtown Creek sediment had a
relatively larger amount in the finer particles (Figure 1). For both sediments,
the low-density fractions had significantly higher concentrations of PAHs. In
Newtown Creek sediment, the low-density material had roughly 10 times the PAH
concentration, while the trend in Piles Creek was much more dramatic. In some
fractions, there were more than 100 times more PAHs in the high-density fraction
for a given size fraction. On a mass basis, the low-density fractions of Piles
Creek and Newtown Creek sediment contained, respectively, 78 and 54 percent of
all PAHs in the sediment. This is striking because only a small fraction of the
sediment mass was in the low-density fraction. In Piles Creek sediment, nearly
80 percent of the PAHs were found in only 5 percent of the sediment mass.
Figure 1. Distribution of total PAH concentration (sum of 16 EPA priority PAHs) in (A) Piles Creek and (B) Newtown Creek sediments. Error bars in Piles Creek reflect average error in extraction of NIST PAH-contaminated sediment; in Newtown Creek, error bars show standard deviation of triplicate extractions.
Figure 2. Koc values for PAHs in various sediment fractions plotted against Koc for bulk, unfractionated sediment.
The large difference in PAH concentrations between the low- and high-density phases is not due to differences in the bulk organic carbon content of the two phases. The low-density phase consistently has 10-fold higher Koc values than bulk sediment, while various size fractions of sediment or the high-density phase of sediment have values similar to the bulk sediment (Figure 2).
Rate and Extent of Desorption. One of the most interesting trends in the desorption data is the difference in rate and extent of desorption between low- and high-density sediment fractions. Shown below are the data from whole Newtown Creek's low- and high-density sediment fractions for the 3-, 4-, and 5-ring PAHs pyrene (Pyr), chrysene (Chr), and benzo(a)pyrene (BAP) (Figure 3). Although the low-density fraction has a higher total PAH concentration, a smaller percentage of the PAHs are removed after 3 months versus the high-density fraction under identical desorption conditions. The total cumulative desorption after 3 months for Pyr, Chr, and BAP from high-density whole Newtown Creek sediment are, respectively, 51, 56, and 31 percent of the total ACN-extractable mass. The corresponding percent cumulative desorption for the same compounds from the low-density faction are less than half: 22, 16, and 15 percent, respectively.
Figure 3. Selected desorption kinetics data from high- and low-density whole Newtown Creek sediment (denoted H-p and L-p, respectively) for the 3-, 4-, and 5-ring PAHs pyrene (Pyr), chrysene(Chr), and benzo(a)pyrene. (A) Cumulative mass desorbed divided by total extractable concentration (unitless) vs time. (B) Flux (see text for definition) vs time until 1 day.
While the common trends among the six data series for cumulative mass desorbed are more a function of low- versus high-density sediment, the similarities among the flux data are more a function of compound. Flux is computed by finding the mass (mg PAH/kg dry sediment) released in a given time interval, divided by the amount of time in that interval, and divided by the specific surface area (m2/g), resulting in units of µg d-1 m-2. Regardless of sediment density, the trend among flux values for the first few observations is pyrene > chrysene > BAP. Pyrene displays a very rapid initial rate (exaggerated in the figure somewhat because the total concentration of pyrene in the sediment is so much higher than the concentrations of chrysene and benzo(a)pyrene), which falls to less than 10 percent of the initial value within the first few hours. The larger PAHs, especially in low-density sediment, display a more gradual decrease in flux with time.
PAH Degradation by Bacterial Strain PC01. PC01 rapidly degraded phenanthrene that was freshly added to Piles Creek sediment (Figure 4). Pyrene was less rapidly degraded. Degradation of both PAHs was slightly slower when they were added as a mixture, but degradation was still complete within 24 h. PC01 also was capable of degrading naturally present PAHs in Piles Creek and Newtown Creek sediment (Figure 4). Degradation was not as complete, however, as would be expected for aged contaminants.
Figure 4. Change in concentration of phenanthrene and pyrene freshly added to Piles Creek sediment and inoculated with PC01. Change in concentration of pyrene and fluoranthene naturally present in Piles Creek and Newtown Creek sediment that had been inoculated with PC01.
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 decisionmaking. As we continue with the analysis and modeling of this extensive data set, we can identify some important trends in PAH sequestration and the rate and extent of contaminant release among sediment fractions. Most notably, low-density fractions have highly elevated PAH concentrations compared to whole sediment, and this fraction is less readily desorbed, but is released at a relatively more constant rate than its high-density analogue. Although not shown here, the Piles Creek sediment is known to conform to the same behavior. These observations have important implications for site remediation strategies, biodegradation potential, and toxicity.
Future Activities:
Future work will compare independent biodegradation data with these results, and complete extensive modeling that will, hopefully, help to resolve the most important mechanisms controlling slow desorption and limited bioavailability for this important class of sediment contaminants.Journal Articles on this Report : 1 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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Rockne KJ, Taghon GL, Kosson DS. Pore structure of soot deposits from several combustion sources. Chemosphere (in press). |
R825303 (1999) R825303 (Final) |
not available |
Supplemental Keywords:
watersheds, exposure, indicators, environmental biology, zoology, modeling., RFA, Scientific Discipline, Water, Waste, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Water & Watershed, Ecology, Bioavailability, Ecosystem/Assessment/Indicators, Ecosystem Protection, exploratory research environmental biology, Chemical Mixtures - Environmental Exposure & Risk, Contaminated Sediments, Chemistry, State, Environmental Microbiology, Ecological Effects - Environmental Exposure & Risk, Biochemistry, Ecological Effects - Human Health, 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 assessmentProgress 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.