Final Report: Formation and Transformation of Pesticide Degradation Products Under Various Electron Acceptor Conditions

EPA Grant Number: R825549C037
Subproject: this is subproject number 037 , established and managed by the Center Director under grant R825549
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: HSRC (1989) - Great Plains/Rocky Mountain HSRC
Center Director: Erickson, Larry E.
Title: Formation and Transformation of Pesticide Degradation Products Under Various Electron Acceptor Conditions
Investigators: Parkin, Gene F , St. Clair, Martin A.
Institution: University of Iowa
EPA Project Officer: Hahn, Intaek
Project Period: May 1, 1992 through May 1, 1995
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (1989) RFA Text |  Recipients Lists
Research Category: Organic Chemical Contamination of Soil/Water , Land and Waste Management


The objectives for the proposed research include the following:

1. To develop and operate batch and column reactors, some including soil-water suspensions, under four different electron acceptor conditions (aerobic, nitrate reducing, sulfate reducing, and methanogenic) in which alachlor and atrazine are transformed.
2. To screen for as many biotransformation products from these systems as possible.
3. To determine the differences among the various electron acceptor conditions, and between the systems with and without soil, to aid in the determination of the degradative pathways for each pesticide under each electron acceptor condition.
4. To develop rate constants for the formation and transformation for of as many of the metabolites as possible.
5. To incorporate the newly developed rate constants into a mathematical model designed to predict the fate of the pesticides under each of the different electron acceptor conditions.

Summary/Accomplishments (Outputs/Outcomes):

Recent research has shown that while atrazine and alachlor are transformed in the environment under a variety of conditions, their rates of mineralization are likely much slower than their rates of initial transformation. Thus there are likely a number of degradation products being formed and perhaps accumulating in the environment, and the nature of these products will likely be a function of the particular environment in which they are formed (ea. the dominant electron acceptor condition). Therefore, it is desirable to gain information regarding the effect of these different environments on the formation and subsequent transformation of the major degradation products.

The proposed research will employ both batch and column reactor techniques, some with soil-water suspensions. Soil obtained from an Iowa agricultural field known to have been treated in the past with atrazine and/or alachlor will be used. The liquid media used in all experiments will be a "synthetic" groundwater designed to maintain one of the electron acceptor conditions of interest. All experimental reactors will be run at 16?C in an effort to keep the expenmental conditions as close as possible to those of a typical Iowa groundwater. Reactors will be seeded with culutres which have been growing under the desired electron acceptor conditions and have been shown to transform atrazine and alachlor. Acetate will be fed as a carbon and energy source. Pesticide, acetate, microbial biomass, and electron acceptors will be monitored over time during each experiment.

Once a significant fraction of the fed pesticide has been transformed, products of atrazine and alachlor will be assayed in the effluents and/or soil samples of each reactor. Standards for some of the expected transformation products will be obtained from The Monsanto Company, Ciba Geigy, or the University of Iowa Hygienic Laboratory. A number of analytical techniques will be employed for the identification and quantification of these metabolic products, including the use of selective GC detectors, GC-MS, or, if necessary, LC-MS. Unknown metabolites may be further analyzed using NMR spectroscopy.

Alachlor and atrazine disappeared in reactors maintained under all electron acceptor conditions, with the exception of aerobic. Batch experiments were carried out in the nine-liter sulfate-reducing and methanogenic reactors, while two-liter reactors were utilized for the experiments performed under denitrifying conditions. Resazurin, a color indicator of redox condition, was found to be involved in the transformation of alachlor and atrazine under denitrifying conditions. Second-order degradation coefficients for the biological transformation of alachlor and atrazine under denitrifying conditions were determined. Alachlor and atrazine degradation coefficients were also determined under methoanogenic and sulfate-reducing conditions. Over the course of four experiments, the rate of alachlor transformation decreased considerably under both of these electron acceptor conditions. Several metabolites of alachlor were positively identified in these systems. Under denitrifying conditions with organisms and resazurin present, aniline, m-xylene, acetyl alachlor, and diethyl aniline were positively identified as products of alachlor degradation. No metabolite accounted for greater than 35% of the initial mass of alachlor. m-Xylene was also detected in an abiotic reactor containing only resazurin, atrazine, and alachlor in groundwater medium under denitrifying conditions. Because this compound is readily degradable, it is unlikely that m-xylene would persist in aerobicv ground water as a result of alachlor contamination and subsequent transformation. The role of resazurin was not clearly defined. Experiments indicated that resazurin itself, or organisms capable of growth on resazurin were responsible for the formation of metabolites. It is also possible that resazurin facilitated electron transfer, as vitamin B12 is known to do, under abiotic conditions.

In the methanogenic and sulfate-reducing reactors, diethyl aniline, acetyl alachlor, and an unidentified metabolite (called SM4 for the purposes of reporting) were detected. No metabolite accounted for greater than 30% of the initial mass of alachlor. Acetyl alachlor was an expected product, likely formed as a result of reductive dechlorination. Some toxicity was noted during the course of the experiments, possibly the result of accumulation of unidentified metabolites, SM1, SM2, and SM4.

Batch experiments were run on the methanogenic an sulfate-reducing reactors using acetyl alachlor. The goal was to identify further transformation products and to develop a degradation coefficient for acetyl alachlor. The acetyl alachlor was never detected in the sulfate-reducing reactor after the initial dosing, due either to poor dosing technique or immediate abiotic transformation by sulfide/bisulfide ions present in the reactor. Acetyl alachlor was detected and monitored in the methanogenic reactor. Acetyl alachlor was initially added at a concentration of approximately 180 mg/l. The concentration in the reactor decreased with time and was below detection levels after 14 hours. Diethyl aniline and aniline were expected metabolites, though aniline and an unidentified compound were the only two transformation products identified by gas chromatography. No transformation products of atrazine were identified under any of the conditions investigated.

The potential pathways leading to commercial application of this new knowledge would include publication of information in peer review journals, and presentation of information at seminars and conferences. Individuals and groups who can make use of the results of this research would include parties who produce and research agricultural chemicals, and also consultants. The results would best be communicated to audiences that can make use of them by publishing them in a peer review journal.

Journal Articles on this Report : 1 Displayed | Download in RIS Format

Other subproject views: All 7 publications 1 publications in selected types All 1 journal articles
Other center views: All 904 publications 230 publications in selected types All 182 journal articles
Type Citation Sub Project Document Sources
Journal Article Novak PJ, Christ SJ, Parking GF. Kinetics of alachlor transformation and identification of metabolites under anaerobic conditions. Water Research 1997;31(12):3107-3115. R825549C037 (Final)
  • Abstract: Science Direct - Abstract
  • Supplemental Keywords:

    atrazine, alachlor, transformation products, kinetics., RFA, Scientific Discipline, Toxics, Water, Waste, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Contaminated Sediments, Remediation, Environmental Chemistry, Geochemistry, pesticides, Chemistry, Fate & Transport, Analytical Chemistry, Hazardous Waste, Ecology and Ecosystems, Hazardous, EPA Region, sediment treatment, fate and transport, contaminant transport, soil and groundwater remediation, fate and transport , contaminated sediment, electron acceptors, contaminated soil, bioremediation of soils, groundwater remediation, chemical kinetics, Region 7, Region 8, contaminated groundwater, pesticide runoff, atrazine, hazardous wate, pesticide residue, phytoremediation, groundwater

    Relevant Websites: Exit

    Progress and Final Reports:

    Original Abstract
  • 1992
  • 1993

  • Main Center Abstract and Reports:

    R825549    HSRC (1989) - Great Plains/Rocky Mountain HSRC

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R825549C006 Fate of Trichloroethylene (TCE) in Plant/Soil Systems
    R825549C007 Experimental Study of Stabilization/Solidification of Hazardous Wastes
    R825549C008 Modeling Dissolved Oxygen, Nitrate and Pesticide Contamination in the Subsurface Environment
    R825549C009 Vadose Zone Decontamination by Air Venting
    R825549C010 Thermochemical Treatment of Hazardous Wastes
    R825549C011 Development, Characterization and Evaluation of Adsorbent Regeneration Processes for Treament of Hazardous Waste
    R825549C012 Computer Method to Estimate Safe Level Water Quality Concentrations for Organic Chemicals
    R825549C013 Removal of Nitrogenous Pesticides from Rural Well-Water Supplies by Enzymatic Ozonation Process
    R825549C014 The Characterization and Treatment of Hazardous Materials from Metal/Mineral Processing Wastes
    R825549C015 Adsorption of Hazardous Substances onto Soil Constituents
    R825549C016 Reclamation of Metal and Mining Contaminated Superfund Sites using Sewage Sludge/Fly Ash Amendment
    R825549C017 Metal Recovery and Reuse Using an Integrated Vermiculite Ion Exchange - Acid Recovery System
    R825549C018 Removal of Heavy Metals from Hazardous Wastes by Protein Complexation for their Ultimate Recovery and Reuse
    R825549C019 Development of In-situ Biodegradation Technology
    R825549C020 Migration and Biodegradation of Pentachlorophenol in Soil Environment
    R825549C021 Deep-Rooted Poplar Trees as an Innovative Treatment Technology for Pesticide and Toxic Organics Removal from Soil and Groundwater
    R825549C022 In-situ Soil and Aquifer Decontaminaiton using Hydrogen Peroxide and Fenton's Reagent
    R825549C023 Simulation of Three-Dimensional Transport of Hazardous Chemicals in Heterogeneous Soil Cores Using X-ray Computed Tomography
    R825549C024 The Response of Natural Groundwater Bacteria to Groundwater Contamination by Gasoline in a Karst Region
    R825549C025 An Electrochemical Method for Acid Mine Drainage Remediation and Metals Recovery
    R825549C026 Sulfide Size and Morphology Identificaiton for Remediation of Acid Producing Mine Wastes
    R825549C027 Heavy Metals Removal from Dilute Aqueous Solutions using Biopolymers
    R825549C028 Neutron Activation Analysis for Heavy Metal Contaminants in the Environment
    R825549C029 Reducing Heavy Metal Availability to Perennial Grasses and Row-Crops Grown on Contaminated Soils and Mine Spoils
    R825549C030 Alachlor and Atrazine Losses from Runoff and Erosion in the Blue River Basin
    R825549C031 Biodetoxification of Mixed Solid and Hazardous Wastes by Staged Anaerobic Fermentation Conducted at Separate Redox and pH Environments
    R825549C032 Time Dependent Movement of Dioxin and Related Compounds in Soil
    R825549C033 Impact of Soil Microflora on Revegetation Efforts in Southeast Kansas
    R825549C034 Modeling the use of Plants in Remediation of Soil and Groundwater Contaminated by Hazardous Organic Substances
    R825549C035 Development of Electrochemical Processes for Improved Treatment of Lead Wastes
    R825549C036 Innovative Treatment and Bank Stabilization of Metals-Contaminated Soils and Tailings along Whitewood Creek, South Dakota
    R825549C037 Formation and Transformation of Pesticide Degradation Products Under Various Electron Acceptor Conditions
    R825549C038 The Effect of Redox Conditions on Transformations of Carbon Tetrachloride
    R825549C039 Remediation of Soil Contaminated with an Organic Phase
    R825549C040 Intelligent Process Design and Control for the Minimization of Waste Production and Treatment of Hazardous Waste
    R825549C041 Heavy Metals Removal from Contaminated Water Solutions
    R825549C042 Metals Soil Pollution and Vegetative Remediation
    R825549C043 Fate and Transport of Munitions Residues in Contaminated Soil
    R825549C044 The Role of Metallic Iron in the Biotransformation of Chlorinated Xenobiotics
    R825549C045 Use of Vegetation to Enhance Bioremediation of Surface Soils Contaminated with Pesticide Wastes
    R825549C046 Fate and Transport of Heavy Metals and Radionuclides in Soil: The Impacts of Vegetation
    R825549C047 Vegetative Interceptor Zones for Containment of Heavy Metal Pollutants
    R825549C048 Acid-Producing Metalliferous Waste Reclamation by Material Reprocessing and Vegetative Stabilization
    R825549C049 Laboratory and Field Evaluation of Upward Mobilization and Photodegradation of Polychlorinated Dibenzo-P-Dioxins and Furans in Soil
    R825549C050 Evaluation of Biosparging Performance and Process Fundamentals for Site Remediation
    R825549C051 Field Scale Bioremediation: Relationship of Parent Compound Disappearance to Humification, Mineralization, Leaching, Volatilization of Transformaiton Intermediates
    R825549C052 Chelating Extraction of Heavy Metals from Contaminated Soils
    R825549C053 Application of Anaerobic and Multiple-Electron-Acceptor Bioremediation to Chlorinated Aliphatic Subsurface Contamination
    R825549C054 Application of PGNAA Remote Sensing Methods to Real-Time, Non-Intrusive Determination of Contaminant Profiles in Soils
    R825549C055 Design and Development of an Innovative Industrial Scale Process to Economically Treat Waste Zinc Residues
    R825549C056 Remediation of Soils Contaminated with Wood-Treatment Chemicals (PCP and Creosote)
    R825549C057 Effects of Surfactants on the Bioavailability and Biodegradation of Contaminants in Soils
    R825549C058 Contaminant Binding to the Humin Fraction of Soil Organic Matter
    R825549C059 Identifying Ground-Water Threats from Improperly Abandoned Boreholes
    R825549C060 Uptake of BTEX Compounds by Hybrid Poplar Trees in Hazardous Waste Remediation
    R825549C061 Biofilm Barriers for Waste Containment
    R825549C062 Plant Assisted Remediation of Soil and Groundwater Contaminated by Hazardous Organic Substances: Experimental and Modeling Studies
    R825549C063 Extension of Laboratory Validated Treatment and Remediation Technologies to Field Problems in Aquifer Soil and Water Contamination by Organic Waste Chemicals