Stable carbon and nitrogen isotope analysis of TNT: Two-dimensional sourceidentification

Data from a combination of laboratory and fieldwork is presented to initiat e testing of stable carbon and nitrogen isotope ratios to trace sources of TNT in contaminated soil and groundwater. Evaluation of these extraction me thods resulted in 99.9 and 99.8% recovery of TNT with Soxhlet and solid-pha se extraction (SPE), respectively. As a result of the high extraction effic iency, isotope fractionation did not occur, thus providing an accurate stab le isotope value on TNT from laboratory and field samples. Subsequent exper iments evaluated the stability of isotope signatures through incubations la sting up to four weeks with a 70% decline in the TNT concentration. During these experiments, no significant variation in stable carbon and nitrogen i sotope ratios was measured. Five different sources of TNT, compared for sta ble carbon and nitrogen isotope ratios, showed a range of 4.2 and 15 parts per thousand, respectively. This large range in the isotope ratios suggests excellent potential to trace sources in a complex environment. Finally, a site was surveyed for concentrations and isotope values of TNT extracted fr om groundwaters. Values from this site were substantially different relativ e to the variation measured on standards and in laboratory incubation exper iments. The data set indicates good potential to use stable isotopes to det ermine TNT sources and fate in the environment.