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

(036) The Effect of RDX, HMX, and TNT on Methane and Acetate Formation in a Methanogenic Mixed Culture.

Adrian, Neal^*,1, Bookwalter, Denise¹, ¹ Engineer Research & Development Center; Construction Engineering Research Laboratory, Champaign, IL, USA

ABSTRACT- The effect of RDX, HMX, and TNT on a methanogenic mixed culture was studied in serum bottles (160 ml) containing 90 ml of a mineral medium and 10 ml of the culture. The effect of the explosives on the heterotrophic methanogens was investigated by amending one set of bottles containing a N₂-CO₂ headspace (80:20) with 5 mM acetate and RDX or TNT. The autotrophic methanogens were studied by amending another set of bottles containing a H₂-CO₂ headspace (80:20) with RDX, HMX or TNT. Compared to the controls, methane production from acetate decreased 52% and 72% in bottles containing 1 M RDX or TNT, respectively. RDX or TNT concentrations ≥5 M completely inhibited methane formation. In bottles containing a H₂-CO₂ headspace and amended with ≥5 M RDX, methane formation decreased more than 70%, while there was no apparent inhibition by HMX or TNT. In these bottles, the addition of RDX or HMX resulted in an increase in the amount of acetate formed. In the control bottles, the acetate was <1 mM, while it increased to 6.1, 9.2, 11.3, and 10.9 mM in the bottles amended with 1, 5, 10, and 20 M RDX. In the bottles containing 1, 2.5, 5, and 10 M HMX, the acetate concentrations were 0.4, 7.8, 10.7, and 12.1 mM. Our findings indicate the explosives inhibit the methangoens while there is an apparent increase in the activity of the homoacetogenic bacteria. Our findings further our understanding of the effect of explosives on anaerobic microbial communities and will be helpful in assessing biotreatment at explosive contaminated sites.

Key words: explosives, inhibition, toxicity, ecotoxicology