Soil-based phytotoxicity of 2,4,6-trinitrotoluene (TNT) to terrestrial higher plants

Seed germination and early stage seedling growth tests were conducted to determine the ecotoxicological threshold of 2,4, 6-trinitrotoluene (TNT) in two soils of different properties. Soils were amended up to 1,600 mg TNT kg-1 soil and four representative species of higher plants, two dicotyledons (Lepidium sativum L., common name: cress; and Brassica rapa Metzg., turnip) and two monocotyledons (Acena sativa L., oat; and Triticum aestivum L., wheat), were assessed. Cumulative seed germination and fresh shoot biomass were measured as evaluation endpoints. Phytotoxicity of TNT was observed to be affected by soil properties and varied between plant species. Cress and turnip showed higher sensitivity to TNT than did oat and wheat. The lowest observable adverse effect concentration (LOAEC) of TNT derived from this study was 50 mg kg-1 soil. In contrast to high TNT concentrations, low levels of TNT, i.e. , 5-25 mg kg-1 soil for cress and turnip and 25-50 mg kg-1 for oat and wheat, stimulated seedling growth. Oat was capable of tolerating as much as 1,600 mg TNT kg-1 and demonstrated a potential ability of TNT detoxification in one of the soils tested, suggesting that this plant might be useful in the bioremediation of TNT contaminated soils.