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: R827015C032
Subproject: this is subproject number 032 , established and managed by the Center Director under grant R827015
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: IPEC University of Tulsa (TU)
Center Director: Sublette, Kerry L.
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: Lasat, Mitch
Project Period: September 1, 2004 through August 31, 2006
Project Period Covered by this Report: September 1, 2004 through August 31, 2005
RFA: Integrated Petroleum Environmental Consortium (IPEC) (1999) RFA Text |  Recipients Lists
Research Category: Hazardous Waste/Remediation , Targeted Research

Objective:

The objectives of this research project are to: (1) verify the hypothesis that degradation is the primary factor leading to isotopic fractionation in the field; (2) verify the hypothesis that stable isotopes provide both positive and negative evidence of biodegradation; (3) develop a database of isotope fractionation by available microbial cultures, primarily of methyl tertiary butyl ether (MTBE ) degraders (and as applicable–tertiary butyl alcohol (TBA) and other gasoline compounds); (4) develop a database of stable isotopic composition (carbon and hydrogen) of MTBE, TBA and other gasoline compounds (reference for data interpretation); (5) prepare a set of case studies of contaminated sites, primarily on MTBE and TBA, but ultimately on other gasoline-range contaminants; and (6) develop 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 Year 1 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 Objectives 1 and 2 (discussed below). A summary of the work in the area (including IPEC grant and other related activities) has been compiled in the form of a document currently under review by the American Petroleum Institute (API), which will be released in late 2005 as API’s “Questions and Answers” advisory on compound-specific isotope analysis (CSIA) application for MTBE remediation work.

Objective 1: Verify the Hypothesis that Degradation Is the Primary Factor Leading to Isotopic Fractionation in the Field

As described in our proposal, the two nondegradation factors potentially leading to isotope effects are sorption and volatilization. A recent publication in the field (Kopinke, et al., 2005) 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 to conduct a laboratory study on the volatilization-related isotope effects in the second year of the project.

Objective 2: Verify 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 have 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 that we studied recently, including some included in our 2005 paper. Biodegradation signatures that would otherwise be detected by CSIA can be obliterated in certain cases by sampling heterogeneous contaminant plume or in the vicinity of residual non-aqueous phase liquid. 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 (although TBA is a product of MTBE biodegradation, it also may 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 percent of wells where the TBA/MTBE concentration ratio was between 1:1 and 5:1, and at 90 percent of wells where the 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 a 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 being conducted in collaboration with Dr. Irene Davidova from Dr. Suflita’s group at The University of Oklahoma’s 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 a 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, although 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. The 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, six 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: Develop 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. 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 to analyze the equilibrate via PT-GCIRMS. This approach should permit better detection limits and also better chromatographic resolution, as the interfering matrix comprised of low molecular weight hydrocarbons dissolves and partitions into the aqueous phase with far lesser ratio.

Currently, we are evaluating the data from the recently finished analyses to compile a database of δ13C and δD of MTBE, TBA, and aromatics (benzene, toluene, ethylbenzene, and xylene [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: Prepare 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 sets. 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 percent. Current settings permit routine analysis of δ13C in MTBE at ca. 1.5 µg/L, δ13C in TBA at approximately 15 µg/L, without compromising accuracy or precision. Optimization of PT-GCIRMS for BTEX and TMB compounds also was 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:

We plan to perform experiments to simulate volatile organic compound 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.

We will continue 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 on 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 are continuing CSIA of the commercial gasoline samples. Carbon CSIA is currently in progress, and hydrogen CSIA is planned for Year 2 of 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).

We plan 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, showing an 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). The site background is being evaluated to identify those where biodegradation of gasoline aromatics may be of special interest.


Journal Articles on this Report : 2 Displayed | Download in RIS Format

Other subproject views: All 5 publications 2 publications in selected types All 2 journal articles
Other center views: All 120 publications 19 publications in selected types All 16 journal articles
Type Citation Sub Project Document Sources
Journal Article Kopinke F-D, Georgi A, Voskamp M, Richnow HH. Carbon isotope fractionation of organic contaminants due to retardation on humic substances: implications for natural attenuation studies in aquifers. Environmental Science & Technology 2005;39(16):6052-6062. R827015C032 (2005)
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  • Journal Article 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. R827015C032 (2005)
    R830633C005 (2005)
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  • Supplemental Keywords:

    water, groundwater, sediments, bioavailability, metabolism, VOC, organics, bioremediation, cleanup, environmental chemistry, analytical, EPA Regions, petroleum industry,, RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Environmental Chemistry, Monitoring/Modeling, Environmental Monitoring, Environmental Engineering, environmental measurement, MTBE, carbon isotopes, biochemistry

    Relevant Websites:

    http://ipec.utulsa.edu Exit

    Progress and Final Reports:

    Original Abstract
  • Final

  • Main Center Abstract and Reports:

    R827015    IPEC University of Tulsa (TU)

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R827015C001 Evaluation of Road Base Material Derived from Tank Bottom Sludges
    R827015C002 Passive Sampling Devices (PSDs) for Bioavailability Screening of Soils Containing Petrochemicals
    R827015C003 Demonstration of a Subsurface Drainage System for the Remediation of Brine-Impacted Soil
    R827015C004 Anaerobic Intrinsic Bioremediation of Whole Gasoline
    R827015C005 Microflora Involved in Phytoremediation of Polyaromatic Hydrocarbons
    R827015C006 Microbial Treatment of Naturally Occurring Radioactive Material (NORM)
    R827015C007 Using Plants to Remediate Petroleum-Contaminated Soil
    R827015C008 The Use of Nitrate for the Control of Sulfide Formation in Oklahoma Oil Fields
    R827015C009 Surfactant-Enhanced Treatment of Oil-Contaminated Soils and Oil-Based Drill Cuttings
    R827015C010 Novel Materials for Facile Separation of Petroleum Products from Aqueous Mixtures Via Magnetic Filtration
    R827015C011 Development of Relevant Ecological Screening Criteria (RESC) for Petroleum Hydrocarbon-Contaminated Exploration and Production Sites
    R827015C012 Humate-Induced Remediation of Petroleum Contaminated Surface Soils
    R827015C013 New Process for Plugging Abandoned Wells
    R827015C014 Enhancement of Microbial Sulfate Reduction for the Remediation of Hydrocarbon Contaminated Aquifers - A Laboratory and Field Scale Demonstration
    R827015C015 Locating Oil-Water Interfaces in Process Vessels
    R827015C016 Remediation of Brine Spills with Hay
    R827015C017 Continuation of an Investigation into the Anaerobic Intrinsic Bioremediation of Whole Gasoline
    R827015C018 Using Plants to Remediate Petroleum-Contaminated Soil
    R827015C019 Biodegradation of Petroleum Hydrocarbons in Salt-Impacted Soil by Native Halophiles or Halotolerants and Strategies for Enhanced Degradation
    R827015C020 Anaerobic Intrinsic Bioremediation of MTBE
    R827015C021 Evaluation of Commercial, Microbial-Based Products to Treat Paraffin Deposition in Tank Bottoms and Oil Production Equipment
    R827015C022 A Continuation: Humate-Induced Remediation of Petroleum Contaminated Surface Soils
    R827015C023 Data for Design of Vapor Recovery Units for Crude Oil Stock Tank Emissions
    R827015C024 Development of an Environmentally Friendly and Economical Process for Plugging Abandoned Wells
    R827015C025 A Continuation of Remediation of Brine Spills with Hay
    R827015C026 Identifying the Signature of the Natural Attenuation of MTBE in Goundwater Using Molecular Methods and "Bug Traps"
    R827015C027 Identifying the Signature of Natural Attenuation in the Microbial Ecology of Hydrocarbon Contaminated Groundwater Using Molecular Methods and "Bug Traps"
    R827015C028 Using Plants to Remediate Petroleum-Contaminated Soil: Project Continuation
    R827015C030 Effective Stormwater and Sediment Control During Pipeline Construction Using a New Filter Fence Concept
    R827015C031 Evaluation of Sub-micellar Synthetic Surfactants versus Biosurfactants for Enhanced LNAPL Recovery
    R827015C032 Utilization of the Carbon and Hydrogen Isotopic Composition of Individual Compounds in Refined Hydrocarbon Products To Monitor Their Fate in the Environment
    R830633 Integrated Petroleum Environmental Consortium (IPEC)
    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