Development of a Soil Extraction Procedure for Ecotoxicity Characterization of Energetic Compounds,

The acetonitrile–sonication extraction method (US EPA Method 8330) associated with aquatic-based toxicity tests was examined to study the ecotoxicity of energetic substances in soil. Three studies were carried out: (1) toxicological characterization of different energetic substances to select a representative toxicant and to validate the choice of bioassays; (2) choice of an appropriate solvent to transfer acetonitrile extracts to the bioassay incubation media; and (3) optimization of Method 8330 using soil samples spiked with the toxicant. Initial studies indicated that pure 2,4,6-trinitrotoluene (TNT) was toxic toVibrio fischeri[Microtox; IC50(15 min) of 4.2 μM], whereas RDX was less toxic (IC20=181 μM) and HMX was not toxic up to its limit of water solubility (<22 μM). Selected pure TNT metabolites were less toxic than TNT. Similar results were found using the 96-hSelenastrum capricornutumgrowth inhibition test. The toxicity of pure TNT in different solvents (acetonitrile, acetone, and DMSO) and that from Method 8330-extracted TNT-spiked soil samples were compared to TNT dissolved in water. Data indicated that DMSO was the most appropriate solvent to transfer the acetonitrile extracts. A modified Method 8330 may be used in conjunction with bioassays and chemical analyses to examine the ecotoxicity of soils contaminated with energetic substances.