T8 AM Ecological Fate and Effects of Explosives and Related Compounds
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in 337-338

(ROB-1117-659142) Can bioavailability of metals and EM in contaminated soils be appraised by chemical bioaccessibility ?

Berthelot, Y^{1, 2}, Auroy, A^{1, 2}, Savard, K^{1, 2}, Robidoux, PY^{1, 2}, ¹ Biotechnology Research Institute, National Research Council Canada, Montreal, Quebec, Canada² Research Centre for Environmental Toxicology (TOXEN), University of Quebec at Montreal, Montreal, Quebec, Canada

ABSTRACT- Bioavailability is now recognized as a main ecotoxicological concern for all media. The challenge is however that it constitutes a multifaceted parameter, which can be tackled with several approaches. In military Energetic Compounds (EC)-contaminated soils, exposure of organisms such as earthworms to various metals and EC either single or in combination may result in deleterious impacts. Those toxic effects are expected to be modulated by toxicant bioaccessibility and bioavailability. This paper reports on the suitability of chemical measures of metals and EM bioaccessibility for the scope of bioavailability assessment. In this study, the earthworm Eisenia andrei was exposed experimentally for 28 days to sublethal concentrations of Pb, HMX and mixtures of Pb + HMX spiked in a forest soil with high organic matter content. Standard endpoints (survival, growth and reproduction parameters) were determined. A suite of different biomarkers has also been used. Bioaccessibilities of Pb and HMX were measured using KNO₃ aqueous extracts at the beginning and the end of the exposure, both in presence and absence of worms. Data showed that HMX and mixtures of Pb+HMX decreased fertility and destabilized lysosomal membranes of earthworm coelomocytes. Because of the high organic carbon content in soil, bioaccessibility of Pb was low when compared to HMX. The regression analysis revealed a significant negative relationship between initial bioaccessible HMX concentrations and either number of juveniles (R²=-0.81, p≤0.05) or total number of cocoons (R²=-0.87, p≤0.05) or number of hatched cocoons (R²=-0.83, p≤0.05). Also, a significant incidence of earthworm activity on bioaccessible Pb concentrations was evidenced but not for HMX. This paper highlights the relevance of jointly using chemical and biological tools for a better bioavailability and toxicity assessment.

Key words: Bioavailability, Bioaccessibility, Energetic material, Metals