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

Publisher Website
Google Scholar
Abstract
The ability of the earthworm Eisenia andrei to metabolize 2,4,6‐trinitrotoluene (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 sublethal concentrations was applied to the same soil and was monitored along with its metabolites in extracts of soil and earthworm tissue for up to 14 d postapplication. High performance liquid chromatography‐ultra violet analyses indicated that TNT was transformed in the presence of E. andrei by a reductive pathway to 2‐amino‐4,6‐dinitrotoluene (2‐ADNT), 4‐amino‐2,6‐dinitrotoluene (4‐ADNT), 2,4‐diamino‐6‐nitrotoluene (2,4‐DANT), and traces of 2,6‐di‐amino‐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. The TNT concentrations decreased from the spiked soils. However, the monoamino‐dinitrotoluene (2‐ADNT and 4‐ADNT) concentrations increased with exposure 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 earthworms present. The biotransformation of TNT into 2‐ADNT, 4‐ADNT, and 2,4‐DANT and the presence of these metabolites in E. andrei after dermal contact on TNT‐spiked filter paper showed that dermal uptake can be a significant exposure 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°C. This effect was inhibited by heat inactivation prior to incubation or by incubation at 4°C, suggesting that the biotransformation of TNT in the presence of E. andrei may be enzymatic in nature.