DEVELOPMENT OF A SOIL EXTRACTION PROCEDURE FOR ECOTOXICITY CHARACTERIZATION OF ENERGETIC COMPOUNDS

The acetonitrile-sonication extraction method (US EPA Method 8330) ass ociated with aquatic-based toxicity tests was examined to study the ec otoxicity of energetic substances in soil. Three studies mere carried out: (1) toxicological characterization of different energetic substan ces to select a representative toxicant and to validate the choice of bioassays; (2) choice of an appropriate solvent to transfer acetonitri le extracts to the bioassay incubation media; and (3) optimization of Method 8330 using soil samples spiked with the toxicant. Initial studi es indicated that pure 2,4,6-trinitrotoluene (TNT) was toxic to Vibrio fischeri [Microtox; IC50 (15 min) of 4.2 mu M], whereas RDX was less toxic (IC20 = 181 mu M) and HMX was not toxic up to its limit of water solubility (<22 mu M). Selected pure TNT metabolites were less toxic than TNT. Similar results were found using the 96-h Selenastrum capric ornutrum growth 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 wa ter. Data indicated that DMSO was the most appropriate solvent to tran sfer the acetonitrile extracts. A modified Method 8330 may be used in conjunction with bioassays and chemical analyses to examine the ecotox icity of soils contaminated with energetic substances. (C) 1998 Academ ic Press.