Final Report: Using Plants to Remediate Petroleum-Contaminated Soil

EPA Grant Number: R827015C018
Subproject: this is subproject number 018 , 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: Using Plants to Remediate Petroleum-Contaminated Soil
Investigators: Thoma, Greg , Wolf, Duane , Ziegler, Susan
Institution: University of Arkansas - Fayetteville
EPA Project Officer: Lasat, Mitch
Project Period: July 1, 2001 through June 30, 2002 (Extended to May 15, 2003)
RFA: Integrated Petroleum Environmental Consortium (IPEC) (1999) RFA Text |  Recipients Lists
Research Category: Hazardous Waste/Remediation , Targeted Research

Objective:

Crude oil-contamination of soil often occurs in areas adjacent to wellheads and storage facilities. Phytoremediation is a promising tool that can be used to remediate such sites and uses plants and agronomic techniques to enhance biodegradation of the hydrocarbon compounds. The objective of this research project was to evaluate fertilizer addition and vegetation establishment on phytoremediation of crude oil-contaminated soil.

Summary/Accomplishments (Outputs/Outcomes):

Field Study

The field site in El Dorado, Arkansas, is located in a bermed crude oil storage/separation facility that was the site of an intentional spill in 1997 by vandals. The experimental plots consist of four replicates of the following treatments: (1) nonvegetated-nonfertilized control, (2) ryegrass (Lolium multiflorum L.)-fescue (Festuca arundinacea Schreb.) plus fertilizer, and (3) bermudagrass (Cynodon dactylon (L.) Pers.)-fescue plus fertilizer. Each field plot has 12 microplots (“soil socks”) that contain homogenized soil that allow monitoring of the field treatments, on a smaller scale, with less effect of field variability of the contaminant levels.

Soil samples were collected September, 28, 2001, at 30 months after plot establishment. Analysis of the soil samples collected 30 months after plot establishment shows the increase in nutrient levels and pH resulting from addition of fertilizer and lime (Table 1). The fertilized plots contained nutrient levels sufficient for plant growth.

Table 1. Chemical Properties of the Crude Oil Contaminated Soil Samples Collected September 28, 2001 at T=30 Months of the Field Study in El Dorado, Arkansas

 

----------Mehlich 3 Extractable-------------

 

----------Total-----

Treatment

pH

P

K

Ca

Mg

Na

 

C

N

 

(2.1)

--------------------------mg/kg----------------------

 

------%------

                   

Control
No Fertilizer
No Vegetation

5.7

8

65

532

70

70

 

4.063

0.065

                   

Fescue/Rye
+ Fertilizer

5.9

23

90

856

137

107

 

3.953

0.095

                   

Bermudagrass
+ Fertilizer

6.0

29

110

973

183

94

 

4.083

0.087

Winter sampling of the field site was done January 6, 2003, at 36 months after plot establishment. For soil samples collected at 36 months, the microbial numbers show that bacterial and fungal numbers were greater in the vegetated-fertilized plots compared to the control plots (Figure 1). There was no apparent difference between the fescue and bermudagrass treatments for bacterial or fungal numbers, and numbers were within ranges expected for petroleum-contaminated soils. The number of petroleum- and alkane-degrader microorganisms suggested that levels were not different among the three treatments at the 36-month sampling (Figure 2). Numbers were consistent with previous observations for the plots.

Figure 1. Bacterial and Fungal Numbers for Soil Samples Collected 36 Months After Plot Establishment at the El Dorado Field Site. The control treatment was not fertilized and vegetation was eliminated. The fescue and bermudagrass plots received fertilizer and lime to facilitate plant growth.

Figure 2. Petroleum- and Alkane-Degrader Microbial Numbers for the Three Treatments at the El Dorado Field Site for Samples Collected 36 Months After Plot Establishment. The numbers were similar across treatments and consistent with previous observations.

For samples collected 36 months after plot establishment, the plant parameter analyses show a high level of growth in the bermudagrass/fescue treatment. Root biomass, length, and surface area were greater in the bermudagrass/fescue treatment than in the fescue/ryegrass treatment that were greater than the control (Figure 3).

Plant root parameters indicate that a high potential exists for a positive rhizosphere effect to enhance crude oil biodegradation. Root biomass production was consistent with shoot biomass production levels (Figure 4).

Analysis of the soil samples collected 36 months after plot establishment show addition of fertilizer resulted in the expected increase in P, K, Ca, and Mg levels (Figure 5). Additional fertilizer applications are warranted as a result of harvesting and removing substantial quantities of shoot biomass.

Figure 3. Root Dry Biomass, Root Length, and Root Surface Area for Samples Collected 36 Months After Plot Establishment at the El Dorado Field Site. The control treatment was not fertilized and vegetation was eliminated. The fescue and bermudagrass plots received fertilizer and lime to facilitate plant growth.

Figure 4. Shoot Dry Biomass for Samples Collected 36 Months After Plot Establishment at the El Dorado Field Site. The control treatment was not fertilized and vegetation was eliminated. The fescue and bermudagrass plots received fertilizer and lime to facilitate plant growth.

Figure 5. Selected Soil Chemical Values for the Three Treatments at the El Dorado Field Site for Samples Collected 36 Months After Plot Establishment

Our initial findings suggest that phytoremediation does reduce contaminant levels through the action of microbial communities associated with the rhizosphere. It is therefore important to develop successful agronomic management strategies that exploit this understanding. Our detailed knowledge of the microbial ecology of the rhizosphere, however, is lacking. We plan to use 13C isotopic labeling of specific contaminants coupled with phospholipid fatty acid (PLFA) analysis to identify specifically which class of microbes is responsible for the degradation. We will continue to investigate the modes of action of a phytoremediation system, keeping in mind that the ultimate goal remains site cleanup.

Microbial Analyses

Laboratory studies have been conducted assessing the 13C-labeling of microbial PLFA in soil using 13C-labeled glucose. Results suggest that the glucose was used to different extents by different microbial groups in the soil. Additionally, a fraction of the glucose was used solely as an energy source and lost as CO2. We currently are developing the means to isolate, purify, and analyze the CO2 evolved in our experiments for δ13C composition. This will enable us to partition the proportion of hydrocarbon contaminant lost to CO2 and incorporated into microbial biomass. Our results indicate that this approach may be used to identify those groups of microbes responsible for the degradation and incorporation of labeled hydrocarbons in soil. Additionally, we have analyzed successfully the microbial PLFA composition of hydrocarbon contaminated soil from our study site, enabling us to begin studies of contaminated soil both at the study site and in controlled experiments using labeled hydrocarbon contaminants. The soil from a single contaminated plot from our study site was dominated by bacterial biomarkers which were found to be as abundant as general PLFA markers such as hexadecanoic acid. The bacterial PLFA detected primarily were branched fatty acids, indicating a dominance of Gram positive bacteria over fungal biomass. Future studies are planned to: (1) assess soil type and conditions on the incorporation and degradation of labeled hydrocarbons, (2) identify those microbial groups responsible for this degradation, and (3) assess the microbial community composition of the established field plots where hydrocarbon degradation occurs.

Mathematical Model

The mathematical model has been extended to include the effect of local climate and soil texture on the efficacy of phytoremediation. The climatic effect includes both the effect of temperature and soil moisture content on the degradation rate constants in the soil. The model can take as input daily temperature and precipitation observations, or daily, monthly, or annual averages. The temperature effect is based on an Arrhenius model with a basal rate at 298K. The soil water potential is used with a published correlation (Gilmour, 1998) to provide a correction factor for moisture stress. The two correction factors are multiplied together to give an overall correction to the degradation rate constants. Thus, when weather patterns result in hot, dry conditions, the degradation rate is decreased because of moisture stress, and it is maximized during warm moist conditions. The choice of dataset does not significantly affect the model prediction; the implication is that short-term and seasonal variations from the mean conditions do not play a significant role in the efficacy of the system.

The mathematical model will be extended to include climatic effects (specifically temperature and moisture level effects on kinetic degradation rate constants), so more site specific screening can be simulated.


Journal Articles on this Report : 3 Displayed | Download in RIS Format

Other subproject views: All 14 publications 3 publications in selected types All 3 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 Thoma GJ, Lam TB, Wolf DC. A mathematical model of phytoremediation for petroleum contaminated soil:sensitivity analysis. International Journal of Phytoremediation 2003;5(2):125-136. R827015C018 (2002)
R827015C018 (Final)
  • Abstract from PubMed
  • Abstract: Informaworld
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  • Journal Article Thoma GJ, Lam TB, Wolf DC. A mathematical model of phytoremediation for petroleum-contaminated soil: model development. International Journal of Phytoremediation 2003;5(1):41-55. R827015C018 (Final)
    R830633 (Final)
  • Abstract from PubMed
  • Abstract: Informaworld
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  • Journal Article White Jr. PM, Wolf DC, Thoma GJ, Reynolds CM. Influence of organic and inorganic soil amendments on plant growth in crude oil-contaminated soil. International Journal of Phytoremediation 2003;5(4):381-397. R827015C018 (Final)
    R830633 (Final)
  • Abstract from PubMed
  • Abstract: Informaworld
    Exit
  • Supplemental Keywords:

    rhizosphere, rhizodegradation, species selection, Arkansas, south central United States,, RFA, Scientific Discipline, Waste, Water, Geographic Area, POLLUTANTS/TOXICS, Contaminated Sediments, Remediation, Chemicals, Chemistry, State, Environmental Microbiology, Hazardous Waste, Bioremediation, Hazardous, Environmental Engineering, degradation, waste treatment, petroleum, contaminated sites, microbial degradation, rhizospheric, petroleum contaminants, biodegradation, decontamination of soil, cleanup, Arkansas, microbes, soils, contaminated soil, bioremediation of soils, contaminants in soil, soil, hydrocarbons, models, phytoremediation, soil microbes

    Relevant Websites:

    http://ipec.utulsa.edu/ Exit
    http://rtdf.org/ Exit

    Progress and Final Reports:

    Original Abstract
  • 2002 Progress Report

  • 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