Fate of 2,4,6‐trinitrotoluene in axenic sand culture systems containing smooth bromegrass

Abstract

Abstract-Plants have the potential to metabolize the munition 2,4,6-trinitrotoluene (TNT) in contaminated soils, sediments, and natural waters. However, microbial interference must be eliminated to demonstrate an intrinsic capacity for the metabolism of TNT by plants. An axenic sand culture system for smooth bromegrass (Bromus inermis Leyss) was established to investigate the influence of TNT on smooth bromegrass growth and metabolism. Shoot length growth was inhibited by 40% after 14 d of exposure to TNT at 36 mg/L in the sand solution, whereas photosynthetic and respiration rates were similar to controls. Addition of [ 14 C]-labeled TNT to the system resulted in the roots containing 21.3% and the shoots containing 3.8% of the radioactivity. The [ 14 C]TNT in media that contained plants was reduced about 50% compared to media without plants. Trace amounts (0.03%) of the initial [ 14 C]TNT was converted to 14 CO 2 during a 5-d incubation period. The TNT and its metabolites were observed in root and shoot extracts by radiochromatographic analysis. The major TNT metabolites identified were 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dinitrotoluene. Previous exposure of the plants to TNT did not increase TNT metabolism or prevent reduction of shoot length growth. From these results we concluded that smooth bromegrass is capable of taking up and metabolizing TNT.

Potential of activated carbon to decrease 2,4,6‐trinitrotoluene toxicity and accelerate soil decontamination

“…These activated carbon amendments maintained TNT concentration in soil solution below 5 mg/L. Corn root elongation measurements indicated tolerance of TNT at this concentration, which is consistent with reports for other terrestrial plants [13,23,24]. Our observations also confirmed the reported toxicity of TNT to microorganisms [8,17,18,20].…”

“…We previously demonstrated accelerated TNT transformation and binding in the rhizosphere of corn plants because of increased activity of soil microorganisms and readily available carbon [22]. Some plants can effectively take up TNT and reduce it to amino derivatives [23], although transpiration and subsequent TNT uptake and transformation can decrease significantly at solution concentrations greater than 5 mg TNT/L [13]. The TNT similarly reduced the growth of other terrestrial plants at elevated concentrations [12,23,24].…”

Selection of Specific Endophytic Bacterial Genotypes by Plants in Response to Soil Contamination

“…Thus, if F. arundinacea did not influence the enrichment process, its roots would need to be permeable to alkane hydrocarbons but not nitrotoluenes. Typically, nitrotoluenes are readily absorbed by grasses, so this is probably not the case (30,31,45).…”

Bioremediation of soils contaminated with explosives

“…Studies with plants have also demonstrated their ability to transform TNT to monoaminodinitrotoluenes and unidentified compounds more polar than TNT Sun et al, 2000;Thompson et al, 1998;Vanderford et al, 1997). Both emergent and submerged aquatic plants have been tested for their TNT tolerance and metabolism.…”

“…In another study TNT was transformed by the smooth bromegrass (Bromus inermis Leyss). However, a decrease in shoot length was observed, and the pretreatment of the plants with TNT decreased uptake and translocation of the radiolabel added in the form of [ 14 C-ring] TNT (Sun et al, 2000). Some recent research demonstrates the ability of plants to take up and covalently bind TNT metabolites (Bhadra et al, 1999c;Sens et al, 1999) and oxidatively transform TNT to 2-amino-4,6-dinitrobenzoic acid, 2,4-dinitro-6-hydroxy-benzyl alcohol, 2-N-acetoxyamino-4,6-dinitro-benzaldehyde, and 2,4-dinitro-6-hydroxytoluene (Bhadra et al, 1999a,b).…”