Migration of explosives in soil: analysis of rdx, tnt, and tetryl from a 14c lysimeter study

Abstract

Abstract This report describes the chemical analysis results of 121 water and 24 soil samples from a 14C lysimeter study of TNT, RDX, and tetryl performed at Battelle Columbus Laboratories. Lysimeters were constructed at Battelle by pressing steel pipes into various soils. The lysimeters were withdrawn to preserve the soil columns intact. 14C ring-labeled munition compounds were than mixed into the surface layer (first 3 inches) of the soils and the lysimeters were irrigated on a regular basis over a six month period. Periodic water samples (leachate) were taken for analysis at selected intervals. The study described here was undertaken (a) to assess the environmental fate of these compounds in various soil samples - since soils within the production areas of U.S. munition plants have become contaminated with raw materials, munition compounds, as well as waste materials, and (b) to determine the persistence and movement of these compounds and their possible decomposition and/or biotransformation products thru the soil to groundwater. The soils (Brookston, Bennington, Genesee, and Princeton) were chosen for their range of textures (from fine to coarse) as well as their ability to fix compounds due to their various amounts of organic matter and ion exchange capacity. Of the 121 water samples (leachate) received, forty-six had 14C activity greater than 100 dpm/ml and were further analyzed by GC/EC, HPLC, and TLC methods. The data indicate that neither TNT nor any of the typical TNT biodegradation or oxidation products were observed in the ‘‘TNT water samples'’ either by GC/EC or HPLC. Analysis of a Princeton - ‘‘TNT water sample'’ with high 14C activity revealed only highly polar, nonvolatile products which could neither be separated nor identified. Analysis of the Princeton - ‘‘RDX water samples'’ revealed increasing amounts of RDX in the leachate (from 1.4 mg/L in the 5/2 sample to 40,0 mg/L in the 8/22 sample). HMX, the impurity in RDX synthesis, was present to the extend of 10% of the RDX amount in each water sample. The Genesee - ‘‘RDX water samples'’ also contained RDX but only at 1/10 the level of that of the Princeton - ‘‘RDX water samples''. The Bennington and Brookston - ‘‘RDX water samples'’ contained virtually no RDX. TLC and 14C analysis of the residue from evaporation of the Princeton - ‘‘RDX #8/22 water sample'’ revealed the following amounts: 40 mg/L RDX, 4 mg/L HMX, 60 mg/L 14C labeled volatile decomposition products and approximately 30 mg/L of other 14C labeled polar nonvolatile decomposition products. Only three ‘‘tetryl water samples'’ had sufficient 14C activity to warrant analysis. Tetryl could not be detected, but trace amounts of picric acid were confirmed by HPLC. TLC analysis of one of the ‘‘tetryl water samples11 revealed only nonvolatile, highly polar products. Visual observations of the various soil textures and porosities coincide with those of Battelle (e.g., Brookston - silty clay, fine texture, Benning-ton - silt loam, medium texture, Genesee - silt loam, medium texture, Princeton - fine sandy loam, coarse texture). Evidence of both degradation and migration was apparent in this 14C study. The retention of the munition compounds (TNT, RDX) as well as their decomposition and/or biotransformation products on the various soils also coincide with the porosity of the soils. The theoretical material balance was also determined from the data obtained on each lysimeter segment analyzed by 14C TLC, and HPLC. Two biotransformation products of TNT, the 4-amino-2,6-dinitrotoluene and the 2-amino-4,6-dinitrotoluene were found in the TNT soil extracts. The Princeton - TNT soil sample contained approximately 6% of each of the aminodinitrotoluenes (ADNT), the Genesee - TNT soil had only 0.1% of each of the ADNT's. The Bennington - TNT soil contained 0,02% of each of the ADNT's, while only 0.01% of the 4A26DNT isomer was found in the Brookston - TNT soil extract. Both the Princeton and Genesee - RDX soil contained approximately 10% HMX, 4.5% volatile materials, and 20% polar type compounds. Known hydrolysis or alkaline degradation products, such as formic acid or formaldehyde were not found.