Effects and bioavailability of 2,4,6‐trinitrotoluene in spiked and field‐contaminated soils to indigenous microorganisms

Abstract

The response of potential nitrification activity (PNA), nitrogen‐fixation activity (NFA), and dehydrogenase activity (DHA) in soil to 2,4,6‐trinitrotoluene (TNT) was assessed. Two garden soils of contrasting texture (sandy loam vs clay loam) were spiked with TNT (25–1,000 mg TNT/kg). Soil microbial activities and TNT residues were analyzed 1 week later. The estimated IC50 (concentration causing 50% inhibition) ranged from 39 to 533 mg/kg of the acetonitrile‐extractable (AE) TNT (1 week after spiking), depending on indicators and soils. The lowest LOEC (lowest‐observed‐effect concentration) was 1 mg AE TNT/kg. Field soil (0–15 cm) was collected from three known contaminated sites in an abandoned TNT manufacturing facility. Microbial toxicity significantly correlated to TNT levels in these soils. The LOEC and NOEC (no‐observed‐effect concentration) values were site and indicator specific, with the lowest LOEC being 1 mg AE TNT/kg and the lowest NOEC being 0.4 mg AE TNT/kg. The IC50 of the pooled field samples was 51 mg AE TNT/kg for PNA or 157 mg AE TNT/kg for DHA. These results indicate that microbial responses were consistent and comparable between the laboratory and the field and that TNT could significantly inhibit soil microbial activities at very low levels. Both AE TNT and deionized water–extractable (DW) TNT concentrations correlated well with microbial toxicity, but AE TNT provided a better evaluation of TNT bioavailability than did DW TNT.

Toxicity and fate of two munitions constituents in spiked sediment exposures with the marine amphipod Eohaustorius estuarius

“…Fast degradation to aminated transformation products was reported for TNT [10,18,27] and for the related compounds trinitrobenzene [15,18] and 2,6-dinitrotoluene [17,23]. The inverse relationship between spiking level and magnitude of degradation observed in this study has been reported previously for TNT and related compounds in sediments [10,15,18] and soils [29,30]. It has been demonstrated that this pathway is preferable thermodynamically [28].…”

Reduction in denitrification activity in field soils exposed to long term contamination by 2,4,6-trinitrotoluene (TNT)

“…Typically, it is assumed that ammonia‐oxidizing bacteria are the most susceptible to pollution [22], yet the correlation between TNT levels in soil and ammonia‐oxidizing ability can be quite low, e.g. r 2 =0.393 [3] and r 2 =0.49 [23]. In contrast, in this study, denitrification activity was strongly negatively correlated, r 2 ≥0.90, with TNT concentrations in soil.…”

“…The extensive manipulation required for the assessment of nitrification activity and prolonged incubation under slurry conditions may be responsible for the differences seen between these two assays [24]. Despite these differences, the IC 50 values for nitrification and denitrification at this field site were similar with an IC 50 of 51 mg TNT kg −1 soil for nitrification [23] and 26 mg TNT kg −1 soil for N 2 OR activity.…”

Effect of experimental contamination with the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine on soil bacterial communities

“…The lowest concentration at which RDX had observable negative effects on the measured parameters was 1235 mg RDX (kg soil) −1 . In contrast, another widely used explosive, TNT, inhibited the same metabolic activities at only 1–2 mg TNT (kg soil) −1 [26].…”