Transformation of 2,4,6-trinitrotoluene in soil in the presence of the earthworm Eisenia andrei

The ability of the earthworm Eisenia andrei to metabolize 2,4,6-trinitrotol uene (TNT) was studied in experiments with TNT-spiked soils, dermal contact tests, and with an in vitro assay. Lethality of TNT in a forest sandy soil was first determined (14-d LC50 = 143 mg/kg). Then TNT at lethal and suble thal concentrations was applied to the same soil and was monitored along wi th its metabolites in extracts of soil and earthworm tissue for up to 14 d postapplication. High performance liquid chromatography-ultra violet analys es indicated that TNT was transformed in the presence of E. andrei by a red uctive pathway to 2-amino-4,6-dinitrotoluene (2-ADNT), 4-amino-2,6-dinitrot oluene (4-ADNT), 2,4-diamino-6-nitrotoluene (2,4-DANT), and traces of 2,6-d iamino-4-nitrotoluene (2,6-DANT) in earthworm tissues. This transformation could be explained by either a metabolic mechanism within the earthworm or by the enhancement of an earthworm-associated microbial activity or both. T he TNT concentrations decreased from the spiked soils. However, the monoami no-dinitrotoluene (2-ADNT and 4-ADNT) concentrations increased with exposur e duration and were dependent on the initial TNT soil concentrations. This was also observed to a lesser extent in the TNT-spiked soils with no earthw orms present. The biotransformation of TNT into 2-ADNT, 4-ADNT, and 2,4-DAN T and the presence of these metabolites in E. andrei after dermal contact o n TNT-spiked filter paper showed that dermal uptake can be a significant ex posure route for TNT. In vitro experiments showed that earthworm homogenate could metabolize TNT and form 2-ADNT and 4-ADNT at room temperature and at 37 degrees C. This effect was inhibited by heat inactivation prior to incu bation or by incubation at 4 degrees C, suggesting that the biotransformati on of TNT in the presence of E. andrei may be enzymatic in nature.