Using Stable Isotopes of Carbon and Nitrogen as In-Situ Tracers for Monitoring the Natural Attenuation of Explosives

Abstract : The use of carbon and nitrogen stable isotope measurements from TNT was examined as a possible tool for monitoring the natural attenuation of TNT incubation studies of spiked soil samples were conducted. The concentration of TNT and the delta values for C-13 and N-15 of the soil and of TNT were measured with time. Results indicated that no measureable changes in the C-delta 13 or N-delta 15 value of the soil or C-delta 13 values for TNT could be detected as the concentration of TNT decreased. Measureable changes in the N-delta 15 value of TNT with changing TNT concentration suggested a possible monitoring route. Field studies using both soil and groundwater samples support the laboratory finding that changes in the N-delta 15 for TNT extracted from groundwater could be detected in samples collected at different points along transects at the Louisiana Army Ammunition Plant and that no measurable change in the C-delta 13 values for soil or TNT could be seen.