Contamination of soils and sediments with explosives such as trinitrotoluene (TNT), and cyclic nitramines (RDX) are widespread problems at military training installations, abandoned production facilities, and munition disposal sites. These compounds are not only toxic and potentially carcinogenic but are also transformed to products of even higher toxicity. Assessing the routes of transformation of such explosives is, however, particularly challenging. Explosives were often spilled in large quantities and they are present in different phases as solid residues, sorbed to soil constituents, and in dissolved form. Moreover, NAC transformation can occur by different, often competing, reaction pathways over years and decades.
To provide estimates of explosives degradation through natural attenuation and through remediation by in and ex situ treatment, we have developed methodologies on the basis of compound-specific stable isotope analysis (CSIA). With this approach, we quantify biological and mineral-catalyzed transformation of explosives as well as various structurally related nitroaromatic compounds and selected nitramines through changes of their stable isotope composition. This so-called isotope fractionation allows for studying combinations of reactive processes that occur over long timescales and regardless of whether contaminant concentrations are affected by dilution and sorption. Applications of CSIA from specific studies of microbial explosives degradation to evaluation of (enhanced) natural attenuation is document in our publications.