Electrokinetic Biodegradation of Glyphosate: Feasibility, Mechanism, and Transport Modeling

Glyphosate is the most widely employed herbicide in the United States and globally. Approximately, 800,000 tons of glyphosate are utilized worldwide every year. Although the impact of glyphosate (GLYP) on human health is still the subject of ongoing debate, exposure to high concentrations of GLYP has been shown to 1) adversely impact ecosystem health including toxicity to several species in aquatic ecosystems and 2) contribute to the emergence of glyphosate-resistant crops, and herbicide resistance in weed populations.

GLYP may also adversely impact soil quality and fertility, either through direct mechanisms such as complexation with metal ions that are essential to plant growth in soils, or through indirect mechanisms such as adversely affecting the growth and metabolism of mycorrhizae and earthworms, which can adversely impact plant access to nutrients and water infiltration in soils. In addition, GLYP accumulates in soils with limited (bio)degradation and mineralization through natural attenuation.

Given the widespread use of GLYP, its potential ecosystem toxicity, and the limitations of natural attenuation, there is a critical need for more efficient and cost-effective remediation technologies for GLYP contaminated soils. The overarching goal of this project is to explore and investigate the utilization of electrokinetic biodegradation (EK-Bio) as an effective remediation technology for GLYP contaminated soils.

The proposed EK-Bio remediation technology utilizes an electric field to enhance the biodegradation of contaminants in soils. The successful completion of this project will benefit society through the generation of new fundamental knowledge, data, and modeling tools to advance the design and deployment of more efficient and cost-effective technologies for the remediation of soils contaminated with GLYP to enable its safe and sustainable use in agriculture and farming.

Additional benefits to society will be achieved through student education and training including the mentoring of a post-doctoral research fellow, one graduate student, and one undergraduate student at the University of Alabama.

As a potential glyphosate (GLYP) soil remediation technology, electrokinetic biodegradation (EK-Bio) has several advantages. First, EK-Bio is an in-situ technology that utilizes an electric field to enhance the biodegradation of contaminants in soils including low-permeability soils. Second, EK-Bio can enhance the degradation of recalcitrant organic contaminants by enhancing ion movement (e.g., contaminants, nutrients, and electron donors/acceptors) and/or by increasing the activity of redox enzymes to enhance GLYP biodegradation in soils.

Third, EK-Bio can easily be integrated with other technologies (e.g., soil flushing) to broaden its applicability and enhance its effectiveness. In this project, the Principal Investigators (PIs) propose to evaluate the hypothesis that EK-Bio has the potential to become an effective technology for the remediation of GLYP contaminated soils. To test this hypothesis, the PIs propose to carry out an integrated experimental and modeling research program.

The specific objectives of the research are to 1) characterize GLYP degradation during EK-Bio under varying environmental and operating conditions in three model and representative soils; 2) probe and unravel the chemical and biological mechanisms of GLYP degradation using advanced analytical chemistry tools and molecular biology techniques; and 3) develop and validate a nonlocal reactive-transport model to simulate GLY fate and transport during an EK-Bio process. To implement the education and training goals of this project, the PIs plan to leverage existing programs at the University of Alabama (UA) to recruit and mentor undergraduate students to work on the project research activities.

In addition, the PIs propose to partner with the University of Alabama Regional In-Service Education Center to deliver two annual education activities consisting of immersive lab demonstrations for high school students and teachers selected from over 120 schools in Western Alabama including a “Scientist for Day” program (Fall Semester) and a “Honor Day” program (Spring Semester).

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.