A càrrec de Genevieve BORDELEAU (INRS-ETE, Québec)
SEMINARIS DE LA FACULTAT DE GEOLOGIA I L'INSTITUT DE CIÈNCIES DE LA TERRA JAUME ALMERA

Universitat de Barcelona (UB)
Consell Superior d'Investigacions Científiques (CSIC)

Dia: divendres, 19 de març
Hora: 12.00 h
Lloc: Sala d'actes de l'Institut Jaume Almera

Resum:
At military training ranges, explosives are being deposited on the ground as a result of incomplete detonation of munitions, or as propellant powder residues. When undergoing natural attenuation, the main explosives usually release nitrite molecules, which can then be oxidized to nitrate in presence of oxygen. This is the case for RDX and nitroglycerin (NG), two explosives commonly found in soils at military training areas. Because several military training areas in Canada are located in agricultural areas, it is important to be able to determine the proportion of nitrate that comes from military activities, as opposed to fertilizers or atmospheric sources. Dual isotopic analyses (δ15N/δ18O) are a promising approach to allow this distinction, and could additionally allow the detection of natural attenuation of RDX and NG, which is otherwise very difficult to detect. However, very little is known about the degradation processes that can contribute to RDX and NG

Laboratory experiments are therefore being carried out in order to characterize the isotopic ratios of nitrate from the main degradation processes that can affect RDX and NG. Several groundwater samples were also collected at different military training areas, at locations where RDX or NG was detected in soils or groundwater. The preliminary isotopic results show that the ratios for nitrate produced from laboratory-degraded RDX and NG are partly found outside of the isotopic fields for the most common nitrate sources reported in the literature. Fractionation seems to be important during the degradation processes, and several more analyses at different time steps are needed in order to characterize each process. Once completed, this will probably be the first study that identifies nitrate as a major contaminant on training ranges, and that uses isotopic analyses to relate it to the degradation of explosives.