This SERDP and ESTCP webinar focuses on DoD-funded research to evaluate the fate, transport, and treatment of munitions constituents (MCs) in soil and groundwater. Specifically, investigators will present models using quantum chemical computations to estimate partition coefficients for MCs between groundwater and interacting soil and biotic phases, and discuss efforts to successfully engineer transgenic plants capable of removing MCs from soil and groundwater.

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Webinar #133 (5/06/2021)

Fate, Transport and Treatment of Munitions Constituents in Soil and Groundwater

Dr. Dominic Di Toro, University of Delaware

Dr. Neil Bruce, University of York

May 6, 2021

12:00 PM ET (9:00 AM PT)

Presentation Slides

Abstracts

“Estimating Munitions Constiutents Fate, Transport, and Treatment Model Parameters” by Dr. Dominic Di Toro ( SERDP Project ER-1734 Webpage)

Evaluating the fate, transport, and proposed treatment designs of munitions constituents (MCs) requires models that can account for the phase distribution of the compounds being evaluated. The quantity in groundwater, soil particles, vadose zone, organisms, and plants plays a central role in the degree to which an MC bioconcentrates, is toxic, and can be treated. The parameters that determine phase distribution are the partition coefficients between the groundwater and the interacting soil and biotic phases. This presentation covers the models that have been developed using funding from SERDP to estimate partition coefficients. The partition coefficient models utilize Abraham solute parameters for the MCs and Abraham system parameters for the phase being evaluated. The reason for this choice is that after the Abraham parameters for an MC are determined, they are applicable to all the systems for which Abraham system parameters are available. This presentation will also cover MCs partitioning to soil and bioconcentration into grass and worms. Progress on methods for estimating Abraham parameters for anion MCs will also be discussed.

“Demonstrating the Efficacy of Using Genetically Modified Plants to Remediate Explosives Pollution” by Dr. Neil Bruce ( ESTCP Project ER-201436 Webpage)

Decades of military activity on live-fire training ranges have resulted in the contamination of land and groundwater by high explosives. 2,4,6-Trinitrotoluene (TNT) and its transformation products are toxic, but these tend to bind strongly to clay and organic matter in soil and are largely contained at the site of contamination. On the other hand, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a major concern because of its high mobility through soils and subsequent contamination of groundwater. RDX contamination on training ranges is now proving to be a significant threat to drinking water sources. Currently, there are no cost-effective processes to contain RDX or remediate large areas of contaminated vegetated land on training ranges. In this presentation, we will discuss the molecular mechanisms behind the detoxification of explosives in plants and how we have used this knowledge, in combination with studies on the bacterial degradation of explosives, to successfully engineer transgenic plants to remediate toxic explosives pollutants. As part of this ESTCP effort, we have genetically modified military relevant plants by inserting genes into them that enable the plants to degrade RDX and detoxify TNT in soils. Field trials have been conducted at Fort Drum to demonstrate the potential of these plant systems to provide a self-sustaining, inexpensive, and environmentally friendly method to alleviate groundwater contamination. The use of this technology will allow the land to remain in use with limited closure to military activities. Specific areas that can potentially benefit from this technology are wide-ranging and include firing points, impact areas, manufacturing sites, and demolition areas.

Speaker Biographies

Dr. Dominic Di Toro is the Edward C. Davis Professor of Civil and Environmental Engineering at the University of Delaware. In a parallel professional career, he served as Senior Research Consulting Engineer at Hydroscience, Inc., and as Principal Consultant and Partner at HydroQual, Inc. His major areas of research have been in building models. At the start of his career, Dr. Di Toro focused on models of eutrophication in the Great Lakes and other estuaries, culminating in a 20-year association with the Chesapeake Bay, for which he built a sediment flux model. He also built models of the partitioning, fate, and toxicity of organic chemicals and metals in water column and sediments. The Biotic Ligand Model for metals and the Target Lipid Model for polycyclic aromatic hydrocarbons (PAHs) are currently part of recommended Environmental Protection Agency criteria. His most recent partitioning and toxicity models use Abraham parameters derived from quantum chemical computations. Dr. Di Toro’s current research projects focus on per- and polyfluoroalkyl substances (PFAS) partitioning models and multiple modes of action toxicity models. His awards include the Society of Environmental Toxicology and Chemistry Founders Award and the Institute of Scientific Information Highly Cited Researcher for Ecology and Environment. He was also elected to the National Academy of Engineering. Dr. Di Toro earned his master’s degree in electrical engineering and his doctoral degree in civil and geological engineering from Princeton University.

Dr. Neil Bruce is the director and professor of biotechnology in the Centre for Novel Agricultural Products at the University of York in the United Kingdom. Dr. Bruce’s research focuses on plant and microbial metabolism of xenobiotic compounds and the characterization of the enzymes mediating these metabolic processes. He has discovered a diverse range of enzymes that have environmental and biotechnological applications. Dr. Bruce has been studying the chemistry, biochemistry, and molecular genetics of explosives metabolism in plants and microbes for over 20 years. He has been an investigator on several SERDP- and ESTCP-funded projects aimed at understanding the fate and remediation of explosives pollution in the environment. Dr. Bruce has co-authored over 150 peer-reviewed papers, many of which focused on explosives biodegradation. He earned a bachelor’s degree from the University of Hertfordshire and a doctoral degree from the University of Kent.