James L. Barnett

Chemical sensing thresholds for mine detection dogs

Mine detection dogs have been found to be an effective method to locate buried landmines. The capabilities of the canine olfaction method are from a complex combination of training and inherent capacity of the dog for odor detection. The purpose of this effort was to explore the detection thresholds of a limited group of dogs that were trained specifically for landmine detection. Soils were contaminated with TNT and 2,4-DNT to develop chemical vapor standards to present to the dogs. Soils contained ultra trace levels of TNT and DNT, which produce extremely low vapor levels. Three groups of dogs were presented the headspace vapors from the contaminated soils in work environments for each dog group. One positive sample was placed among several that contained clean soils and, the location and vapor source (strength, type) was frequently changed. The detection thresholds for the dogs were determined from measured and extrapolated dilution of soil chemical residues and, estimated soil vapor values using phase partitioning relationships. The results showed significant variances in dog sensing thresholds, where some dogs could sense the lowest levels and others had trouble with even the highest source. The remarkable ultra-trace levels detectable by the dogs are consistent with the ultra-trace chemical residues derived from buried landmines; however, poor performance may go unnoticed without periodic challenge tests at levels consistent with performance requirements.

Phase Partitioning of TNT and DNT in Soils

Detecting the presence of a burred landmine or unexploded ordnance using explosive chemical vapors has been considered possible with advances in sensitivity and selectivity of emerging chemical sensing technologies. Sampling and analysis of explosive vapors emanating from soils is a significant challenge due to the low vapor concentrations produced through this process; Understanding the environmental impacts to this chemical signature is also important, as environmental factors have a dramatic effect on the transfer of the chemical mass between soil solid, liquid and vapor phases. This work was completed to assess the phase partitioning phenomena of two explosive chemical materials (2,4,6-m and 2,4-DNT) typically found in landmines and ordnance. Laboratory measurements of water solubility, soil-water partitioning, and soil-vapor partitioning were completed in the absence of literature values. An integrated soil system partitioning analysis was completed using soil physics phase partitioning theory for use in evaluation of the impact of environmental factors. Using estimates of soil residues from samples adjacent to burred landmines and ordnance, performance requirements for vapor sensing buried landmines and unexploded ordnance have been estimated.

Explosive chemical emissions from landmines

Chemical sensing for buried landmines is a complex phenomenon that includes mine chemical emissions, soil chemical transport/degradation, and detection at the ground surface. The technology to assess soil chemical transport has evolved and now provides a complex systems analysis capability using high fidelity computational simulation tools. Data requirements to evaluate a chemical sensing scenario include soil chemodynamic properties, micrometeorological conditions, and mine chemical emissions. Mine chemical emission tests were performed on four antipersonnel landmines using whole landmines in soil flux chambers. Soil flux chambers are simple containers that surround landmines with dry soil that act as an adsorbent. After a certain soak time, residue analysis of the soil provides the total chemical emission - a combination of both permeation and leakage. An evaluation of permeation differences into wet soil versus dry soil was also completed using thin polymer coupon sections.

Measurement and Modeling of Energetic Material Mass Transfer to Soil Pore Water - Project CP-1227 Annual Technical Report

Military test and training ranges operate with live fire engagements to provide realism important to the maintenance of key tactical skills. Ordnance detonations during these operations typically produce minute residues of parent explosive chemical compounds. Occasional low order detonations also disperse solid phase energetic material onto the surface soil. These detonation remnants are implicated in chemical contamination impacts to groundwater on a limited set of ranges where environmental characterization projects have occurred. Key questions arise regarding how these residues and the environmental conditions (e.g., weather and geostratigraphy) contribute to groundwater pollution impacts. This report documents interim results of a mass transfer model evaluating mass transfer processes from solid phase energetics to soil pore water based on experimental work obtained earlier in this project. This mass transfer numerical model has been incorporated into the porous media simulation code T2TNT. Next year, the energetic material mass transfer model will be developed further using additional experimental data.

Environmental Impact to the Chemical Signature Emanating from Buried Unexploded Ordinance

Abstract : Detecting the presence of buried unexploded ordnance (UXO) using chemical vapors derived from the main charge explosive has been considered possible with advances in sensitivity and selectivity of emerging chemical sensing technologies. Understanding the environmental impacts to this chemical signature is critical, as environmental factors have a dramatic effect on the source release, transport, phase transfers and degradation in soil systems. This project established several tasks to evaluate the environmental impact to the chemical signature from buried UXO. These tasks included simulation model development and utilization to evaluate the interdependent physico-chemical transport phenomena in near surface soils, fundamental property measurement for those parameters needed in the simulation model that had insufficient or poor quality data, and laboratory-scale experiments that produced data for comparison to simulation model results. This project also sponsored work to produce data on the chemical release characteristics of a small subset of ordnance and UXO, and to determine the chemical residues in the field adjacent to actual UXO. This work has resulted in the development of a simulation model, T2TNT, which incorporates the soil chemodynamic processes most important to near surface soil transport of chemical residues from buried UXO. Measurements were made of the temperature dependent water solubility of TNT and DNT, soil-liquid partition coefficient for DNT, and the soil-vapor partitioning coefficient as a function of soil moisture content for TNT and DNT. Comparison of T2TNT simulation results to laboratory-scale vapor flux experiments simulating a buried source release were excellent. UXO source release tests showed that prior to firing, ordnance contained a sufficient chemical reservoir for release into the soil. However, after firing and recovery (now as an UXO), the ordnance chemical flux was insufficient to overcome biochemical degradation rates.

Effect of soil wetting and drying on DNT vapor flux: laboratory data and T2TNT model comparisons

Sensing the chemical signature emitted from the main charge explosives from buried landmines is being considered for field applications with advanced sensors of increased sensitivity and specificity. The chemical signature, however, may undergo many interactions with the soil system, altering the signal strength at the ground surface by many orders of magnitude. A simulation code named T2TNT was developed specifically to evaluate buried landmine chemical transport issues. A vapor-solid partitioning parameter that is strongly dependent on soil moisture content is included in T2TNT. Laboratory soil vapor flux experiments were conducted to provide data to validate the T2TNT model under well-constrained laboratory testing conditions. The landmine source release, soil transport and surface flux was simulated by aqueous phase injection of DNT, evaporation induced upward water flux and solid phase microextraction sampling of headspace vapor in an air flowing plenum. The surface soil moisture content was reduced by suction removal of soil water followed by artificial rain to evaluate the soil-vapor partitioning function in T2TNT. The data showed the dramatic decline in DNT vapor concentrations expected as the surface soil moisture declined; and, then rebounded upon wetting. This phenomenon was modeled with T2TNT and showed excellent correlation.

GICHD Mine Dog Testing Project - Soil Sample Results No.3

A mine dog evaluation project initiated by the Geneva International Center for Humanitarian Demining is evaluating the capability and reliability of mine detection dogs. The performance of field-operational mine detection dogs will be measured in test minefields in Afghanistan and Bosnia containing actual, but unfused landmines. Repeated performance testing over two years through various seasonal weather conditions will provide data simulating near real world conditions. Soil samples will be obtained adjacent to the buried targets repeatedly over the course of the test. Chemical analysis results from these soil samples will be used to evaluate correlations between mine dog detection performance and seasonal weather conditions. This report documents the analytical chemical methods and results from the third batch of soils received. This batch contained samples from Kharga, Afghanistan collected in October 2002.

GICHD Mine Dog Testing Project - Soil Sample Results No.2

A mine dog evaluation project initiated by the Geneva International Center for Humanitarian Demining is evaluating the capability and reliability of mine detection dogs. The performance of field-operational mine detection dogs will be measured in test minefields in Afghanistan containing actual, but unfused landmines. Repeated performance testing over two years through various seasonal weather conditions will provide data simulating near real world conditions. Soil samples will be obtained adjacent to the buried targets repeatedly over the course of the test. Chemical analysis results from these soil samples will be used to evaluate correlations between mine dog detection performance and seasonal weather conditions. This report documents the analytical chemical methods and results from the fifth batch of soils received. This batch contained samples from Kharga, Afghanistan collected in June 2003.

Characterization of Scrap Materials for Mass Detonating Energetic Materials - Final Report, Project CU1194

Abstract : Military test and training ranges generate scrap materials from targets and ordinance debris. These materials are routinely removed from the range for recycling; however, energetic material residues in the range scrap has presented a significant safety hazard to operations personnel and damaged recycling equipment. The Strategic Environmental Research and Development Program (SERDP) sought proof of concept evaluations for monitoring technologies to identify energetic residues among range scrap. Sandia National Laboratories teamed with Nomadics, Inc. to evaluate the Nomadics FIDO vapor sensor for application to this problem. Laboratory tests were conducted to determine that the vapor-sensing threshold to be 10 to 20 ppt for TNT and 150 to 200 ppt for DNT. Field tests with the FIDO demonstrated the proof of concept that energetic material residues can be identified with vapor sensing in enclosed scrap bins. Items such as low order detonation debris, demolition block granules, and unused 8 1-nun mortars were detected quickly and with minimum effort. Conceptual designs for field-screening scrap for energetic material residues include handheld vapor sensing systems, batch scrap sensing systems, continuous conveyor sensing systems and a hot gas decontamination verification system.