Grantee Research Project Results
2005 Progress Report: Utilization of the Carbon and Hydrogen Isotopic Composition of Individual Compounds in Refined Hydrocarbon Products To Monitor Their Fate in the Environment
EPA Grant Number: R830633C005Alternative EPA Grant Number: R827015C032
Subproject: this is subproject number 005 , established and managed by the Center Director under grant R830633
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: HSRC (1989) - Northeast HSRC
Center Director: Sidhu, Sukh S.
Title: Utilization of the Carbon and Hydrogen Isotopic Composition of Individual Compounds in Refined Hydrocarbon Products To Monitor Their Fate in the Environment
Investigators: Philp, R. Paul , Kuder, Tomasz
Institution: University of Oklahoma
EPA Project Officer: Aja, Hayley
Project Period: September 1, 2004 through December 31, 2006 (Extended to August 31, 2007)
Project Period Covered by this Report: September 1, 2004 through December 31, 2005
Project Amount: Refer to main center abstract for funding details.
RFA: Integrated Petroleum Environmental Consortium (IPEC) (1999) RFA Text | Recipients Lists
Research Category: Targeted Research
Objective:
Progress of the first year of the project will be discussed using the framework of objectives defined in the proposal.
- Verification of the hypothesis that degradation is the primary factor leading to isotopic fractionation in the field.
- Verification of the hypothesis that stable isotopes provide both positive and negative evidence of biodegradation.
- A database of isotope fractionation by available microbial cultures, primarily of MTBE degraders (and as applicable – TBA and other gasoline compounds).
- A database of stable isotopic composition (carbon and hydrogen) of MTBE, TBA and other gasoline compounds (reference for data interpretation).
- A set of case studies of contaminated sites, primarily on MTBE and TBA, but ultimately on other gasoline-range contaminants.
- Development of a commercially viable method for site characterization based on the stable isotope values and trends observed in the results obtained from this study.
Progress Summary:
Activities in the first year of the project were primarily focused on combined field-microcosm studies of contaminated sites (Objectives 3 and 5) and the survey of isotope ratios on individual compounds in commercial gasolines (Objective 4). Progress made in stable isotope geochemistry by our group and other research groups, since the time the proposal was prepared resulted in a reevaluation of the significance of the objectives 1 and 2 (discussion below). A summary of the work in the area (including IPEC grant and other related activities) has been compiled to in the form of a document, currently under review by American Petroleum Institute, to be released later this year as API’s “Questions and Answers” advisory on CSIA application for MTBE remediation work (Appendix 1).
Objective 1 – Verification of the hypothesis that degradation is the primary factor leading to isotopic fractionation in the field
As described in our proposal, the two non-degradation factors potentially leading to isotope effects are sorption and volatilization. A recent publication in the field (Carbon Isotope Fractionation of Organic Contaminants Due to Retardation on Humic Substances: Implications for Natural Attenuation Studies in Aquifers; Frank-Dieter Kopinke, Anett Georgi, Michael Voskamp, and Hans H. Richnow, 2005, Environemntal Sci. Tech., 39, 6052 - 6062) provides a good base to understand the significance of sorption in isotope fractionation of contaminants. The basic conclusion from their work is that the contribution of sorption to the net isotope effect is negligible. We plan conducting a lab study on the volatilization-related isotope effects in the second year of the project.
Objective 2 – Verification of the hypothesis that stable isotopes provide both positive and negative evidence of biodegradation
In addition to the older publications, a number of publications (peer-reviewed journals and conferences) describing MTBE degradation has been released recently. To the best of our knowledge, all experiments where MTBE was confirmed to degrade were associated with TBA accumulation (in most cases the conversion was at stoichiometric ratio). This is the type of biodegradation, which is and has been the primary target for our microcosm work. Given the limited capacity of microcosm work and the apparent lack of success except where MTBE-TBA conversion is concerned, we have decided to abandon this line of research. We are in contact with different parties conducting microbiological studies of MTBE and in the case of breakthrough results becoming available we may revisit the original idea.
A more practically important factor for understanding the positive-negative evidence of CSIA emerged from a number of field cases we studied recently, including some included in our 2005 paper. Biodegradation signatures which would otherwise be detected by CSIA can be obliterated in certain cases by sampling heterogeneous contaminant plume or in the vicinity of residual NAPL. A rough estimate of the significance of this interference was made by looking at the total number of monitoring wells studied to date, where TBA occurred at significant quantity. High TBA concentration was considered a proxy for high probability of MTBE degradation (note – while TBA is a product of MTBE biodegradation, it may also be originally present in spilled gasoline, so that some of the monitoring wells might in fact not be affected by biodegradation). CSIA strongly confirmed biodegradation at 50 % of wells where TBA/MTBE concentration ratio was between 1:1 and 5:1, and at 90 % of wells where TBA/MTBE ratio was exceeding 5:1. With two exceptions (one with three, another with two “high-TBA” monitoring wells), at least one “high-TBA” monitoring well per site provided a positive CSIA result even if other wells did not.
Rather than trying to obtain microcosm data from sites where field samples show no biodegradation signatures in CSIA, we have generated some preliminary results showing the impact of sampling technique on the results, e.g., well purging vs. no purging resulting with different volume of the potentially heterogeneous plume being sampled. This line of research – optimizing the field sampling routine and defining criteria for site selection – will be pursued in the second year of the study.
Objective 3 – A database of isotope fractionation by available microbial cultures
This part of the study is done in collaboration with Dr. Irene Davidova from Dr. Suflita’s group at OU Microbiology Department. This arrangement allows us to conduct the microcosm experiments drawing on the expertise in anaerobic biodegradation provided by our partner.
Soil/sediment samples from two contaminated gas station sites in California have been obtained from BP partner early in the project for microcosm construction. The sites have been previously studied for isotope effects in groundwater and evidence of biodegradation was detected. At one site, the evidence of MTBE biodegradation was very strong, while there was no apparent effect for TBA. Microcosms constructed from this site were amended with fresh MTBE which was rapidly converted to TBA (within 10 weeks). The rate of degradation was higher than expected, so that no samples with enough MTBE were collected to measure isotopic fractionation characteristic of this culture. Currently, the microcosms are incubated after new reamendment with MTBE. This time the lag time is longer and no evidence of degradation is available yet. Three of the original microcosm bottles where all MTBE was converted to TBA are set aside and monitored for TBA degradation. Second sediment sample set has been amended with TBA only. The previously studied water specimens contained TBA with δ13C more positive than the typical range, possibly indicating TBA biodegradation. Currently no microcosm activity has been observed.
As will be discussed under Objective 5, a number of field sample sets have been analyzed permitting identification of sites where MTBE or TBA degradation is suggested by isotopic enrichments. Based on this data, 6 sites have been selected for microcosm study (and another one based on preliminary results acquired in years 2001-2004). Soil sampling has been scheduled for the last week of September 2005 (they will be collected together with the water samples for the quarterly site monitoring). Microcosms – one set for TBA degradation study, using soil from a site where TBA seems to be degrading based on both isotope data and decreasing site concentrations, and the remaining sets for MTBE degradation – will be constructed immediately after the material arrives.
Objective 4 – A database of stable isotopic composition (carbon and hydrogen) of MTBE, TBA and other gasoline compounds
A collection of 50 samples of commercial gasoline has been obtained from Dr. Graham Rankin (Marshal University). Analysis of those specimens has been initiated, first by direct injection for carbon isotope composition. The same samples will be reanalyzed in the future for hydrogen isotope composition, and for the samples where MTBE and TBA in particular cannot be measured due to insufficient concentration or poor chromatographic resolution, the samples will be equilibrated with water to utilize the preferential partitioning of the two compounds into the aqueous phase and analyze the equilibrate via PT-GCIRMS. This approach should permit better detection limits and also better chromatographic resolution, as the interfering matrix comprising of low molecular weight hydrocarbons dissolves does partitions into the aqueous phase with far lesser ratio.
We are currently evaluating the data from the recently finished analyses to compile a database of δ13C and δD of MTBE, TBA and aromatics (BTEX, tri- and tetramethylbenzenes and naphthalenes), to supplement the existing data or provide the first reference data for the compounds where none or only few data were published. For the specific purpose of the project, MTBE, TBA and BTEX numbers will be particularly interesting, as biodegradation of those compounds is of most interest.
Objective 5 – A set of case studies of contaminated sites, primarily on MTBE and TBA, but ultimately on other gasoline-range contaminants
Nine sets of field samples have been provided by industrial partners and analyzed (carbon CSIA) to select good candidates for soil sampling and microcosm experiments (as discussed in Objective 3). The sites have been selected using the criteria of historical MTBE concentration data (decrease of MTBE) and on standard geochemical biodegradation criteria. Eight of the sets were collected in California (gas station sites) and one in Illinois (former refinery). Evidence of biodegradation (“heavy” signatures of MTBE) was detected in seven of those. A sample from one of the sites has shown 13C enrichment in TBA, possibly also indicating biodegradation. Six of the most promising sites (including the one with suspected TBA biodegradation) are scheduled for soil sampling. Additionally, soil sampling is scheduled at another site, where CSIA indicated 13C enrichment TBA (analyses completed prior to IPEC grant initiation).
In continuation of the previously performed carbon isotope work, a sample set from a BP gas station site in New York has been analyzed for hydrogen isotopes of MTBE. Combined carbon + hydrogen results supported the expected aerobic biodegradation mechanism of MTBE attenuation at this site.
Other activities
Analytical methods development has been in progress resulting with improving quantitation limits of the PT-GCIRMS for the oxygenates by 100 %. Current settings permit routine analysis of δ13C in MTBE at ca. 1.5 μg/L, δ13C in TBA at ca. 15 μg/L, without compromising accuracy or precision. Optimization of PT-GCIRMS for BTEX and TMB compounds was also done in anticipation of extending CSIA applications to those contaminants in the second year of the study. Current settings permit analysis of those compounds at 0.5 – 1 μg/L concentration.
Future Activities:
The following paragraphs refer to the objectives defined in the proposal (see “introduction” above):
- It is planned to perform experiments to simulate VOC volatilization in the conditions of porous medium in contact with contaminated groundwater. Vapor transfer-related isotope fractionation is to be sought. No published experimental data are relevant due to experiments being performed in closed system or volatilization from NAPL rather than from aqueous solution, resulting with different physical mechanisms affecting isotope fractionation.
- Continuation of the preliminary field study of the importance of small-scale heterogeneity of plumes on CSIA results. Different sample collecting methods and the significance of spatial sample coverage will be investigated.
- Continuation of the work with the existing microcosms is planned to enable enough data to be collected for precise calculation of the magnitude of isotope effects upon MTBE biodegradation. Monitoring of TBA microcosms for evidence of biodegradation will continue. Seven more sites have been selected for microcosm experiments. The sites will be sampled in late September 2005 and microcosms developed immediately after the soil samples are available.
- We continue CSIA of the commercial gasoline samples. Carbon CSIA is currently in progress and hydrogen CSIA is planned for the second year on the project. Currently, 40 specimens of gasoline are available. If significant variations of the isotope ratios in the compounds of interest (MTBE, TBA, BTEX, TMB) are observed, we have access to another sample set of similar size (also to be provided by Dr. Rankin, Marshal University).
- It is planned to initiate screening of the incoming field samples for stable isotope effects indicative of monoaromatic compound degradation (carbon and more importantly – hydrogen; hydrogen fractionation is known to be very strong upon BTEX compounds biodegradation and hydrogen CSIA is likely to be more diagnostic than carbon CSIA). The prerequisite for data interpretation will be provided by the database of carbon and hydrogen isotope ratios in fresh gasolines discussed above. Resampling of some of the formerly analyzed sites is planned to investigate temporal trends in biodegradation (one set, shoving interesting trend in TBA isotope ratios, is scheduled for resampling in September 2005). Currently no other field sites are specifically scheduled for sampling in the nearest quarterly monitoring round. We expect incoming field material in the following quarter(-s). Site background is being evaluated to identify those where biodegradation of gasoline aromatics may be of special interest.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other subproject views: | All 10 publications | 2 publications in selected types | All 2 journal articles |
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Other center views: | All 32 publications | 8 publications in selected types | All 8 journal articles |
Type | Citation | ||
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Kuder T, Wilson JT, Kaiser P, Kolhatkar R, Philp P, Allen J. Enrichment of stable carbon and hydrogen isotopes during anaerobic biodegradation of MTBE: Microcosm and field evidence. Environmental Science & Technology 2005;39(1):213-220. |
R830633C005 (2005) R827015C032 (2005) |
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Supplemental Keywords:
Water, groundwater, sediments, bioavailability, metabolism, VOC, organics, bioremediation, cleanup, environmental chemistry, analytical, EPA Regions (1 through 10), petroleum industry,, RFA, Scientific Discipline, TREATMENT/CONTROL, Waste, Sustainable Industry/Business, Sustainable Environment, Treatment Technologies, Remediation, Technology for Sustainable Environment, Environmental Engineering, decontamination, environmental technology, contaminated sediments, petroleum contaminated soil, environmental sustainability, petrochemicals, petroleum industry, remediation technologies, ecological impacts, environmental regulations, environmental education, bioremediationProgress and Final Reports:
Original AbstractMain Center Abstract and Reports:
R830633 HSRC (1989) - Northeast HSRC Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R830633C001 Development of an Environmentally Friendly and Economical Process for Plugging Abandoned Wells (Phase II)
R830633C002 A Continuation of Remediation of Brine Spills with Hay
R830633C003 Effective Stormwater and Sediment Control During Pipeline Construction Using a New Filter Fence Concept
R830633C004 Evaluation of Sub-micellar Synthetic Surfactants versus Biosurfactants for Enhanced LNAPL Recovery
R830633C005 Utilization of the Carbon and Hydrogen Isotopic Composition of Individual Compounds in Refined Hydrocarbon Products To Monitor Their Fate in the Environment
R830633C006 Evaluation of Commercial, Microbial-Based Products to Treat Paraffin Deposition in Tank Bottoms and Oil Production Equipment
R830633C007 Identifying the Signature of the Natural Attenuation in the Microbial Ecology of Hydrocarbon Contaminated Groundwater Using Molecular Methods and “Bug Traps”
R830633C008 Using Plants to Remediate Petroleum-Contaminated Soil: Project Continuation
R830633C009 Use of Earthworms to Accelerate the Restoration of Oil and Brine Impacted Sites
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.
Project Research Results
2 journal articles for this subproject
Main Center: R830633
32 publications for this center
8 journal articles for this center