Plant‐Bacterial Combinations to Phytoremediate Soil Contaminated with High Concentrations of 2,4,6‐Trinitrotoluene

Abstract

AbstractThe explosive 2,4,6‐trinitrotoluene (TNT) is a contaminant of concern at abandoned manufacturing and military sites because of its mobility and toxicity. Phytoremediation may play a role in natural attenuation scenarios by reducing TNT levels at point sources. The purpose of this study was to develop a phytoremediation system suitable for use in soils contaminated with high TNT levels. Sixteen grasses were screened for their tolerance to 41 g TNT kg−1 soil. Meadow bromegrass (Bromus erectus Huds.), perennial ryegrass (Lolium perenne L.) and sweet vernalgrass (Anthoxanthum odoratum L.) grew in this soil. Inoculating these grasses with Pseudomonas sp. Strain 14, capable of transforming TNT into mono‐ and di‐amino metabolites, increased the growth of meadow bromegrass but was lethal to perennial ryegrass and sweet vernalgrass. Meadow bromegrass inoculated with Strain 14 reduced TNT levels by 30% compared with the control soil and had 50% more plant biomass than noninoculated plants. Meadow bromegrass, combined with Strain I4, increased the percentage of the culturable soil heterotrophic population containing the genes involved in 2‐nitrotoluene (ntdAa) metabolism 3‐fold, as well as the population containing the genes involved in 4‐nitrotoluene (ntnM) metabolism 14‐fold. Strain I4 inoculation of meadow bromegrass altered the portion of the rhizosphere community involved in nitroaromatic metabolism and led to a reduction in soil TNT levels.