PARENT SESSION
SA4 - Ecotoxicology and Risk Assessment of Explosives
Chair: Steevens, Jeffery1, 1 3909 Halls Ferry Road, Vicksburg, Mississippi, USA
Co-chair: Lotufo, Guilherme2, 2 3909 Halls Ferry Road, Vicksburg, Mississippi, USA
8:00 AM to 12:00 PM - Sunday, 17 November 2002
Room Ballroom F
(037) Aquatic toxicology of trinitrotoluene (TNT).
Lotufo, Guilherme*,1, Steevens, Jeffery1, 1 US Army Engineer Research and Development Center, Vicksburg, MS, USA
ABSTRACT- Trinitrotoluene (TNT) and its degradation products are contaminants of concern typically associated with military activities. The toxicity of TNT and the TNT breakdown products 2-aminodinitrotolune (2ADNT) and 2,4-diaminonitrotoluene (2,4DANT) and trinitrobenzene (TNB) were compared using fish and benthic invertebrates. In water exposures, 2,4DANT was substantially less toxic than the other compounds for the midge Chironomus tentans and the fish Cyprinodon variegatus, but was the most lethal compound for the amphipod Hyalella azteca. Radiolabeled TNT spiked to fresh water and marine sediments rapidly breaks down to ADNT and DANT congeners and a substantial portion of the compounds move into the overlying water during static exposures. The non-solvent-extractable fraction of the radiolabel increases with increasing aging of the sediment. In sediment exposures using C. tentans, concentrations associated with toxicity were similar for all compounds. Most of the TNT molecules accumulated by aquatic invertebrates appear to rapidly transform to ADNT or DANT and to strongly bind to organic molecules becoming non-extractable and non-detectable by traditional chemical analysis. Critical body residues determined as the sum molar concentrations of chemically detected nitroaromatics were similar for C. tentans (0.04 mmol/kg), C. variegatus (0.04 mmol/kg) and Leptocheirus plumulosus (0.07 mmol/kg). To further investigate the real-world effects of explosives, the combined effects of TNT with its degradation products were investigated. Exposures to a mixture of TNT, ADNT, DANT, and TNB in sediment and water were found to interact additively using a toxic unit approach. However, the mixture was not dose additive due to the lower potency of DANT. Knowledge of the toxicity, mechanisms of action, bioaccumulation, and mixture interactions for TNT and will provide valuable information when extrapolating laboratory data to ecological risk assessments.
Key words: TNT, Sediment, Critical body residue, Mixtures