Emmanuela Diaz

Influence of surface roughness, volume diffusion and particle size in reflectance infrared spectroscopy

In the field of Defence and Public Security, standoff detection is a useful tool to identify many threats, such as chemical warfare agents, toxic industrial compounds and other chemical substances under various physical states (gas, liquid and solid). Over the years, Defence Research and Development Canada (DRDC) - Valcartier Research Centre has built an extensive expertise in the field of hyperspectral standoff detection. Although the technology behind the detection instruments is well known, the interpretation of spectral signatures of materials can sometimes be difficult. In reflectance infrared spectroscopy of solids, the same molecule can yield different signatures depending on sample surface roughness and particle sizes as opposed to the transmission and absorption infrared spectroscopies for which the signatures are significantly less influenced by these parameters. In principle, molecules containing one ionic bond, such as NaCl, must not exhibit infrared peaks, since only covalent bonds are supposed to generate active bands in the thermal infrared region. However, experimental results show significant spectral features in reflectance infrared spectroscopy. In fact, in reflectance spectroscopy, the volume diffusion phenomenon can generate spectral features even if no fundamental vibration occurs in the molecule. An effort has been undertaken at DRDC to understand the phenomenology associated with these variations. This paper summarizes experimental results which emphasize the roles of surface roughness and particle size in the interpretation of reflectance infrared spectra of solid materials.

A Conceptual Model of Fate and Transport Processes for RDX Deposited to Surface Soils of North American Active Demolition Sites.

The use of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) as an energetic material (EM) in ammunition constituents such as detonators, primers, mines, and rocket boosters and in plastic explosives has led to an international warning on possible soil, surface water, and groundwater contamination on military training sites. In Canada, the demolition sites of range training areas are known to be the second most contaminated sites by EM residues in terms of their concentrations in soil after anti-tank ranges. This research proposes a conceptual model of the presence of RDX at the field scale at demolition sites according to previous soil and water characterization studies. This model illustrates the origin of RDX contamination, the main RDX transport pathways and processes, and the main threatened receptors. This conceptual model is of importance to visualize and understand RDXs environmental fate and behavior and to ultimately enable the production of a detailed quantitative model that can help to manage those RDX-contaminated sites.