Toxicity reduction of explosives-contaminated soils by composting

The treatment of explosive-contaminated soil was evaluated using the compost technology. Two laboratory-scale compost reactors were used to provide enough composted material to conduct mutagenic and toxicological experiments and chemical analyses. Two explosive-contaminated soil mixtures containing cow manure and alfalfa were composted for 30 days. The Mutatox(TM) bacterial mutagenicity assay and the earthworm acute toxicity tests were used to evaluate the effectiveness of the non-composted and composted soils. The non-composted explosive-contaminated soil was lethal to all exposed earthworms, as were both composted soils prior to composting. Extracts of the initial materials were toxic to bacteria in the Mutatox(TM) assay. Dilutions of the extracts to sublethal concentrations showed a low level of mutagenicity. Extracts of the finished composts showed reduced bacterial toxicity. Composting also reduced the lethality to earthworms. Serial dilutions of the finished composts with artificial soil had earthworm 14-day LC50's of 100% and 35.3%. The reduction in lethality paralleled the evaluation of explosives caused by composting, as indicated by chemical analyses. However, the increased mutagenicity was a result that might not have been indicated by chemical analysis alone.