Progress 10/01/03 to 09/30/09
Outputs
OUTPUTS: The two main outputs of this study were to characterize field samples of petroleum-contaminated sediment for influx of fresh plant matter as sediments naturally re-vegetate and then to characterize how vegetation alters sediment composition and polycyclic aromatic hydrocarbon (PAH) desorption using batch sorption studies in the laboratory. Sediments from containated field sites were chemically finger-printed to evaluate petroleum aging. Natural abundance 14C analyses determined the percent modern C (plant C) to petroleum C in areas with different types of vegetation or no vegetation. Desorption data from aqueous batch and Tenax-TA beads for sediments at two different sites were fitted to a two compartment, first-order kinetic model to determine desorption kinetics to evaluate if desorption kinetics differed between vegetated and non-vegetated sediment fraction. PARTICIPANTS: This project supported two master students, Thorne Gregory and Jennifer Musella as well as five undergraduate researchers who were supported with funds from NC State or the College of Natural Resoruces. The five undergraduate researchers were Thomas Crawford, Zach Eyler, Carter Reeb, Rachel Zajac, Brian Levine. Collaborations included partnerships with USEPA for field site collection. TARGET AUDIENCES: The overall target audience for this project involves pratictioners and academics using plants are remedial tools for organic pollution. Elements of this project were incoporated into classroom instruction in a course on Environmental Monitoring and Analysis and via mentoring of undergraduate researchers. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The project resulted in two Master of Science degrees based on the work of two graduate students. Five undergraduate researchers also contributed to the project efforst with funding support from NC State University. Research findings tested two proposed two mechanisms of how plant organic matter would alter polycyclic aromatic hydrocarbon (PAH) bioavailability over time in soils and sediments. First, the rhizosphere can improve PAH bioaccessibility and increase PAH release by destabilizing organic matter (OM) via enhanced microbial activity, abundance, and carbon turnover and by alteration of OM composition due to microbial and plant release of organic acids, plant materials, and chelating agents. New plant carbon materials would be more polar and less likely to sorb PAHs. Alternatively, these same processes could produce OM matrices that are more non-polar in nature and further bind PAHs, thus reducing PAH bioaccessibility and slowing PAH release. Field site analyses showed that organic matter in petroleum contaminated sediment with vegetation was more polar and less condensed than non-vegetated areas. The modern carbon content of these sediments was much greater indicating the greater presence of plant carbon from Phragmites. These vegetated waste pit materials desorbed PAH faster than non-vegetated waste materials. PAH desorption usually involves PAH release from fast and slow OM compartments; vegetated OM had faster PAH desorption kinetics from the dominant slow release compartment. These results all support the first proposed mechanism which should result in greater PAH attenuation over time. In fact, vegetated OM had much lower concentrations of PAHs and specific PAH ratios that indicated greater weathering of the PAHs compared to non-vegetated OM. PAH loss and weathering were apparent in bulk sediment and humin fractions as well as high and low density fractions of vegetated OM. Modern carbon content of vegetated humin from waste pit materials (33%) was much greater than non-vegetated humin (2%).
Publications
- Nichols, E.G. and J. Musella. 2009. Differences in PAH Desorption and Sediment Organic Matter Composition Between Non-Vegetated and Recently Vegetated Fuel-Oiled Sediments. International Journal of Phytoremediation, 11:463 to 478, 2009.
- Nichols, E.G., Gregory, S.T. and J. Musella. 2008. The Impact of Vegetation on Sedimentary Organic Matter Composition and PAH Desorption. Environmental Pollution, 156: 928 to 935.
- Gregory, S.T. and E. Guthrie Nichols. 2008. Differences in Sediment Organic Matter Composition and PAH Weathering Between Non-Vegetated and Recently Vegetated Fuel-Oiled Sediments. International Journal of Phytoremediation, 10:473to 485.
- Gregory, S.T., D. Shea, E. G. Nichols. 2005. The Impact of Vegetation on Sedimentary Organic Matter Composition and PAH Attenuation. Environmental Science and Technology, 39:5285 to 5292.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Activities have continued to characterize how vegetation alters sediment composition and polycyclic aromatic hydrocarbon (PAH) desorption. Desorption data from aqueous batch and Tenax-TA beads for sediments at two different sites were fitted to a two compartment, first-order kinetic model to determine desorption kinetics. The black carbon content of sediment fractions were also determined as well as equilibrium distribution coefficients for select PAHs (Log Koc). Project results have been disseminated by publication in peer-reviewed journals and presentation at scientific meetings.
PARTICIPANTS: Jennifer Musella (graduate student), ENSR Consulting and Engineering 7041 Old Wake Forest Road, Suite 103, Raleigh, NC 27616 Thorne Gregory (graduate student).
TARGET AUDIENCES: Professionals in Phytoremediation
Impacts
PAH desorption from distillate waste sediments appeared to be controlled by the slow desorbing fractions of sediment; rate constants were similar to literature values for kslow and kvery slow. This site is a refinery, distillate waste pit that has naturally re-vegetated over several decades with Phragmites australis. After several decades of plant colonization and growth (Phragmites australis), vegetated sediment fractions more extensively-desorbed PAHs and had faster desorption kinetics than non-vegetated sediment fractions. Vegetated sediments were more polar and contained 30-50% more plant carbon than non-vegeated distillate waste. Decadal growth of Phragmites and deposition of plant C into distillate waste appears related to increased PAH release from both labile (bulk sediment) and more refractory (humin) sediment organic matter. Increased PAH desorption is associated with reduced PAH concentrations and more PAH weathering in vegetated refinery waste. The second
site is a freshwater, canal contaminated with fuel oils in Gary, IN. At this site, Phragmites only recently colonized near shore sediments (< 2yrs). Phragmites sediments contained two-fold more modern carbon (plant carbon) but were less polar and more reduced than non-vegetated sediments. Desorption kinetics indicated that PAH desorption was primarily controlled by a slow-desorbing fraction of IHC sediment; however, the presence of plant carbon increased the rates of PAH desorption in vegetated sediments, particularly humin. We propose that plant carbon influx to IHC sediments adds more amorphous and less rigid carbon domains to IHC sediments that facilitate more rapid PAH desorption. Prior studies indicate that contamination is often not the primary factor controlling soil hydrophobicity. Increased soil hydrophobicity can be attributed to plant residues and microbially-derived lipids. These results suggest that more reduced and nonpolar (hydrophobic) Phragmites IHC sediment may
result primarily from Phragmites carbon influx and rhizosphere microbial activity. Increased PAH desorption is associated with reduced PAH concentrations and more PAH weathaering in fuel-oiled sediments although PAH reductions are small after only two years of plant growth.
Publications
- Nichols, E. G., and J. Musella. 2008. Differences in PAH Desorption and Sediment Organic Matter Composition Between Non-Vegetated and Recently Vegetated Fuel-Oiled Sediments. International Journal of Phytoremediation (in review).
- Nichols, E.G., Gregory, S.T. and J. Musella. 2008. The Impact of Vegetation on Sedimentary Organic Matter Composition and PAH Desorption. Environmental Pollution. (in review).
- Gregory, S.T. and E. Guthrie Nichols. 2007. Differences in Sediment Organic Matter Composition and PAH Weathering Between Non-Vegetated and Recently Vegetated Fuel-Oiled Sediments. International Journal of Phytoremediation. (in press)
- Nichols, E.G., and J. Musella. 2007. Plant Organic Matter Deposition Alters Sedimentary Organic Matter Composition and PAH Desorption. Annual Conference on Soils, Sediments, and Water. Amherst, MA. October 15th-18th, 2007.
- Nichols, E.G., S.T. Gregory, and J. Musella. 2007. The Impact of Vegetation on Sediment Composition, PAH Attenuation, and PAH Desorption. 4th International Phytotechnologies Conference, September 24-26, 2007. Denver, Colorado.
- Reeb, C., S. T. Gregory, E. Guthrie Nichols. 2007. Use of Sediment Polarity to Predict Release of Petroleum Contaminants in Vegetated or Non-vegetated Sediment. NC State Undergraduate Research Symposium. April 14th, 2007.
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Progress 01/01/06 to 12/31/06
Outputs
Activities have focused on characterizing how vegetation alters sediment composition and polycyclic aromatic hydrocarbon (PAH) desorption. Aqueous batch and Tenax-TA beads were used for desorption studies of historic petroleum and fuel-oiled sediments with and without Phragmites australis colonization were placed in. One site, a freshwater canal, has recently been colonized by Phragmites; the other site, an estuary site, has had Phragmites present for more than 20 years. PAH desorption was measured in triplicate for seven time points spanning a 120-day period. An aliquot of the decanted aqueous phase was removed with a 10 mL pipette and transferred to another 50 mL Teflon Oak Ridge centrifuge tube and extracted with 5mL of dichloromethane (DCM); the DCM layer was removed and transferred to a 40 mL amber EPA vial with anhydrous sodium sulfate (Na2SO4) to remove any residual water. DCM extracts were evaporated under a gentle stream of N2 gas to approximately 1 mL and
transferred to a gas chromatography/mass spectrometry (GC/MS) vial using a 500 μL syringe. Sample volumes were adjusted to 1 mL, sealed, and stored at -2 oC until GC/MS analysis. Sediment composition was evaluated using fourier transform infrared spectroscopy (FTIR). Functional groups in sediment fractions were analyzed by FTIR on an Impact 400 Nicolet (1993) FTIR spectrophotometer equipped with an OMNIC automatic data acquisition system. The sample pellets used were prepared by grinding 0.5 to 1.0 mg of sediment fraction and 60 to 80 mg infrared-grade potassium bromide (KBr) salt separately using a mortar and pestle; powdered sediments were mixed with powdered KBR, pressed together, then analyzed. Data acquisition was accomplished by using a 32 spectrum resolution per cm. Elemental analyses of carbon, hydrogen, and nitrogen were determined by high-temperature combustion and/or pyrolysis techniques on a ConFlo III Elemental Analyzer (Thermo Electron North America LLC, West Palm
Beach, FL). One sediment fraction and a set of duplicate sediment fractions, making up 25% of samples analyzed, were sent to Huffman Labs (Golden, CO). Standard methods ASTM D-4129 (C and H), ASTM D-5373 (N), and ASTM D-5622 (O) were used. Percent relative standard deviation (RSD) was predominantly within 10% for most samples. FTIR and elemental analyses of sediment fractions from established Phragmites sediments (> 20 years) showed that Phragmites sediments contained more polar organic matter than non-vegetated sediment fractions. Batch aqueous desorption isotherms showed that the fraction of PAH desorbed was greater for Phragmites sediment and humin fractions than non-vegetated sediment fractions. Tenax extractions did not show such distinct differences. Sediments with recent Phragmites colonization (< 5 years) were less polar than non-vegetated sediments; PAH desorption from Phragmites was less than observed for non-vegetated sediments.
Impacts
We propose that one mechanism to explain enhanced PAH attenuation in Phragmites sediments over time is the deposition and accumulation of polar plant organic matter in both labile and refractory fractions of the sediment matrix. Previous studies have focused on plant exudates' relationships to PAH-degrading microbial communities; these results emphasize the broader chemical and physical impact of plant organic matter on contaminated SOM and PAH bioavailability. Polar plant organic matter accumulation in petrogenic SOM results in greater PAH desorption from labile and refractory sediment over time. The presence of labile plant organic matter should also support a more diverse and abundant microbial community in Phragmites sediment that would contribute to greater biogenic and PAH carbon turnover in sediment.
Publications
- No publications reported this period
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Progress 01/01/05 to 12/31/05
Outputs
Activities have focused on characterizing vegetated and non-vegetated sediment density samples collected at the Indiana Harbor Canal area of Gary, (IN) in collaboration with Steve Rock, USEPA. Density sediments were analyzed for chemical fingerprinting, IRMS analyses, and total organic carbon analyses. Sediments were also fractionated into bulk sediment, bulk humin, and humin samples. Fractionation of sediment improves the detection sensitivity of natural and anthropogenic C in sediments and helps ascribe particular processes of stabilization or destabilization to specific portions of organic matter. Chemical fractionations for humic materials, size fractions, and density fractions have been used to correlate PAH bioavailability with specific C pools. Density fractions are used to improve our understanding of biogenic and anthropogenic PAH carbon cycling in the rhizosphere of plants at contaminated sites. Although stable carbon isotope analyses are applicable and
useful to our analyses, we will also use precise radiocarbon signature analysis to track the movement of (1) depleted PAH carbon from PAH contamination and (2) enriched 14C carbon from plant carbon deposition in density and humic fractions of sediment. Phragmites and cattails bulk sediment fractions contain significantly less PAH contamination than the non-vegetated sediment. Phragmites and cattails bulk humin sediment fractions contained more PAH contamination than non-vegetated or willow sediments. Only Phragmites humin fractions contained significantly more PAH contamination than other sediment analyzed. 14C AMS data for Phragmites and cattails bulk sediments at Indiana Harbor Canal show greater amounts of biogenic C in sediment fractions with reduced PAH contamination. Biogenic C in bulk humin fractions were significantly greater for Phragmites and cattails; whereas, only Phragmites had greater biogenic C in humin fractions. Unlike bulk sediments, bulk humin and humin fractions
contained increased biogenic C and PAH contamination for these vegetated fractions. Density fractions of sediments show greater PAH contamination (mass PAH/mass sediment) for vegetated light density fractions than vegetated heavy density fractions. Vegetated light density fractions contained more PAH than non-vegetated light density fractions; non-vegetated heavy density fractions contained significantly more PAH contamination than vegetated heavy density fractions. Significantly more biogenic C is found in heavy density fractions for all sediments than their light density fraction counterparts. For both density fractions, Phragmites fractions are the most weathered. These sediments are recently vegetated. When results are compared to PAH sediments with longer resident vegetation times, light density fractions appear to contain more biogenic C than heavy density fractions. Current desorption studies of PAHs in these fractions together with 14C AMS analyses will better delineate the
degree of sequestration and rates of biogenic and PAH C cycling.
Impacts
Understanding the mechanisms by which persistent and recalcitrant pollutants are impacted by biologically-active systems is critical to ensuring environmental protection at achievable fiscal costs. The collaboration between Nichols research with industry and government directly benefits undergraduate and graduate student education. Industry and government are eager to define bioavailability as it relates to their environmental sites and concerns. As our understanding of contaminant fate in complex environmental matrices expands; innovation of vegetated systems will advance our ability to determine environmental risk and improve environmental protection.
Publications
- Gregory, S.T., D. Shea, E. G. Nichols. 2005. The Impact of Vegetation on Sedimentary Organic Matter Composition and PAH Attenuation. Environmental Science and Technology, 39:5285-5292.
- Eyler, Z., S. T. Gregory, E. G. Nichols. 2005. The Impact of Metal Chelation and Vegetation on PAH Desorption from Refinery Waste Sediments. State of North Carolina Undergraduate Research Symposium. November 12th, 2005.
- Crawford, T., S. T. Gregory, E. G. Nichols. 2005. Presence of Glomalin in Petroleum-Impacted Sediments. NCSU Undergraduate Research Symposium. April 28th, 2005.
- Gregory S.T., S. Ejlali, E. Guthrie-Nichols. 2005. How Plant Carbon Inputs Affect PAH Bioavailability in Sediments. U.S. EPA International Applied Phytotechnologies Conference, April 19th-22nd,, 2005, Atlanta, GA.
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Progress 01/01/04 to 12/31/04
Outputs
Activities have focused on characterizing samples collected at the Indiana Harbor Canal area of Gary, (IN) in collaboration with Steve Rock, USEPA and co-ordinating sample collection at North Carolina with North Carolina Department of Environmental and Natural Resources in Wilmington, NC. Initial chemical fingerprinting of alkylated and non-alkylated PAHs for preliminary vegetated and non-vegetated samples collected at the Indiana Harbor Canal has been completed. Target sediments have been fractionated into bulk, humic, and humin fractions as well as size and density fractions for chemical fingerprinting, IRMS analyses, total organic carbon analyses, toxicity screening, and CPMAS 13C NMR analyses. Initial screening of various naturally, vegetated sections of the Indiana Harbor Site provides some indication that some plant species appear to weather fuel oil contamination more than others. Both Phragmites and cattails rhizosphere sediments contain less PAH contamination
than the non-vegetated sediment. Stable carbon isotopic ratio analyses of bulk sediment from non-vegetated sediment are significantly different and more negative than sediment from cattails and Phragmites. Fractionation of sediment improves the detection sensitivity of natural and anthropogenic C in sediments and helps ascribe particular processes of stabilization or destabilization to specific portions of organic matter. Chemical fractionations for humic materials, size fractions, and density fractions have been used to correlate PAH bioavailability with specific C pools. Efforts for the next year will focus on utilizing density fractions to better understand biogenic and anthropogenic PAH carbon cycling in the rhizosphere. Although stable carbon isotope analyses are applicable and useful to our analyses, we will also use precise radiocarbon signature analysis to track the movement of (1) depleted PAH carbon from PAH contamination and (2) enriched 14C carbon from plant carbon
deposition in density and humic fractions of sediment. 14C AMS data for Phragmites sediments at Indiana Harbor Canal indicate that the heavy and light occluded fractions have incorporated more biogenic carbon than the free light fraction. D3/C3 PAH weathering ratios likewise show PAHs in these fractions as more weathered than in the free light fraction. Although residual mass amounts of PAHs in free light fractions are greater, they appear to be less bioavailable than PAHs in occluded and heavy fractions. 14C AMS data agree with D3/C3 PAH weathering ratios that plant material in light density fractions reduces PAH weathering and that heavier fractions appear to contain a fast-cycling and slow-cycling carbon pools. Desorption and bioassay studies of PAHs in these fractions together with 14C AMS analyses will better delineate the degree of sequestration and rates of cycling. 14C AMS data indicates the signature of PAH-derived carbon in Phragmites roots. Radiocarbon analyses of various
classes of compounds in sediment and vegetation will clarify not only the cycling (and stabilization) of PAHs in these sediments, but also contaminant feedbacks to the natural C cycle.
Impacts
Understanding the mechanisms by which persistent and recalcitrant pollutants are impacted by biologically-active systems is critical to ensuring environmental protection at achievable fiscal costs. The collaboration between Nichols research with industry and government directly benefits undergraduate and graduate student education. Industry and government are eager to define bioavailability as it relates to their environmental sites and concerns. As our understanding of contaminant fate in complex environmental matrices expands; innovation of vegetated systems will advance our ability to determine environmental risk and improve environmental protection.
Publications
- Gregory, S.T., D. Shea, E. Guthrie-Nichols. 2005 (in review). Field Assessment of Plant-derived Organic Matter Deposition on PAH Bioaccessibility and Attenuation. Submitted to: Environmental Science and Technology.
- Gregory S.T., E. Dzierzynski, S. Ejlali, P.G. Hatcher, E. Guthrie-Nichols. 2004. Understanding Plant Carbon Inputs on PAH Bioavailability in Sediments. 25th Annual Meeting of the Society of Environmental Toxicology and Chemistry - North American Conference, November 14-18, Portland, OR.
- Gregory S.T., E. Dzierzynski, E. Guthrie-Nichols. 2004. Effects of Plant Carbon Inputs on PAH Rremediation and Bioavailability in Sediments. National Science Foundation/Environmental Molecular Science Institute at The Ohio State University 3rd Annual Workshop. The Ohio State University, June 11-13th, Columbus OH.
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Progress 01/01/03 to 12/31/03
Outputs
To understand mechanistically how plants either (1) enhance organic contaminant desorption for biodegradation or (2) accelerate organic contaminant sequestration in refractory organic fractions of contaminated geomedia, we have conducted forensic analyses of polycyclic aromatic hydrocarbons (PAHs) distributions in fractions of soil/sediment organic matter from a coastal estuary contaminated with PAHs and naturally revegetated with Phragmites. In addition to determination of alkylated and non-alkylated PAH distributions in organic matter fractions, the same fractions were analyzed by IRMS. Organic matter has also been separated by particle size and density fractionation to compare difference among PAH distributions along the successional vegetation gradient. Alklyated and non-alkylated PAH concentrations were determined by GC/MS-SIM. A site with PAH contaminated soil planted with hybrid poplars, willows, and native vegetation has been sampled but analyses are not
complete. PAH analyses of these sites show that PAH concentrations decline as plant communities increase in complexity. However, this decline is not as dramatic in stable fractions of the sediment matrix such as humin. d13C values for site 1 and site 3 suggest that distillate petroleum waste SOM is impacted by plant organic matter as plant communities develop for bulk sediment and refractory organic matter such as humin. Sediments from four sites across the vegetation gradient were sieved and each size fraction was density separated using CsCl. Each size and density fraction was then extracted to determine the concentrations of the 16 Priority PAHs. Overall, lighter fractions of geomedia contain more PAHs per kg geomedia than denser fractions. Larger, lighter particles (>300mm L) and smaller, heavier particles (<32mm H) increase in percent sediment mass as vegetation dominates. PAH concentrations also shift more to lighter fractions (though different size - <32mm L) and the smaller,
heavier particle fraction (<32mm H) as vegetation dominates. Larger-sized and lighter particles appear to contain more bioavailable PAHs for removal than smaller particles. Plant material and black carbon represent lighter particles found in soil. Isotopic and total organic carbon analyses will help us determine source differences between size and density particles relative to PAH contamination.
Impacts
Understanding the mechanisms by which persistent and recalcitrant pollutants are impacted by biologically-active systems is critical to ensuring environmental protection at achievable fiscal costs. The collaboration between Nichols research with industry and government directly benefits undergraduate and graduate student education. Industry and government are eager to define bioavailability as it relates to their environmental sites and concerns. As our understanding of contaminant fate in complex environmental matrices expands; innovation of vegetated systems will advance our ability to determine environmental risk and improve environmental protection.
Publications
- Gregory, T; Blair, N; Goldfarb, B; Ball, L; Dria, K; Hatcher, PG; Guthrie-Nichols E. PAH Bioavailability in Soils/Sediments: Applications of 13C-labeling techniques to understand plant carbon inputs on PAH fate. Joint Interagency Program on Phytoremediation Research, National Science Foundation, Arlington, VA, January 20-21, 2004.
- T. Gregory, K. Dria, P.G. Hatcher, E. Nichols. 2003. Effect of Successional Revegetation on PAH Bioavailability in Refinery Waste Sediment. Advancing The Science of Toxicology and Entomology Symposium. September 18th-19th, Research Triangle Park, NC.
- Guthrie-Nichols, E; Walker, A; Grasham, A; Simpson, M; Hatcher, P.G. 2003. PAH Fate in Anaerobic Sediments: Applications of 13C-labeling techniques to understand PAH Bioavailability and Biodegradation. Department of Environmental and Molecular Toxicology, North Carolina State University, Raleigh, NC, April 15th, 2003.
- Guthrie-Nichols, E; Gregory, T; Chefetz, B; Simpson, M.;Hatcher, P.G. 2003. Influence of Vegetation on PAH Bioavailability. U.S. EPA International Applied Phytotechnologies Conference, March 3-5th, 2003, Chicago, IL.
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