RP14 Ecological Fate and Effects of Explosives and Related Compounds
Thursday, 17 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(ZHA-1117-140268) Acute Toxicity and Bioavailability of Hexahydro-1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) Metabolites to the Earthworm, Eisenia fetida.

Zhang, B¹, Anderson, T¹, ¹ Texas Tech University, Lubbock, TX, USA

ABSTRACT- MNX and TNX are two important metabolites of the common explosive RDX. Although several studies have demonstrated that RDX is toxic to a number of organisms, including humans, the toxicity of MNX and TNX is not known. In this study, acute toxicity and bioavailability of MNX and TNX to Eisenia fetida was evaluated. Results indicate that both MNX and TNX had lethal and sublethal effects on earthworms. Exposure to MNX- or TNX-contaminated soil caused a significant concentration-dependent decrease in survival and growth of earthworms. Earthworms were more sensitive to TNX than to MNX. MNX and TNX were more toxic in sandy loam soil than in silt loam soil. The Lowest Observed Lethal Concentration (LOLC) for both MNX and TNX was 100 mg/kg in the sandy loam soil, and 200 mg/kg in the silt loam soil. At 7 days of exposure, the Lowest Observed Effect Concentration (LOEC) for earthworm growth was 50 mg/kg for TNX and 100 mg/kg for MNX in both soil types. The kinetics of MNX and TNX uptake into passive sampling devices (PSDs), and the ability of PSDs to serve as surrogates for evaluating bioavailability of RDX metabolites were also investigated. MNX and TNX absorption into PSDs was best fitted with a polynomial curve model: y = ax2 + bx + c (y: amount of MNX or TNX absorbed into PSD; x: incubation time of PSDs in soil), with an excellent correlation coefficient (r2 > 0.95). A linear relationship between PSD uptake and earthworm uptake was observed. The correlation coefficients were > 0.90 in almost all test soils spiked with MNX or TNX. These data indicate that C18 PSDs may be used as a surrogate for soil organisms such as earthworms and provide a simple chemical test for assessing the bioavailability of contaminants in soils.

Key words: explosive, toxicity, bioavailability, earthworm