PW03 QSAR
Exhibit Hall
8:00 AM - Wednesday
(PW028) Analysis of naphthenic acid toxicity using (Quantitative) Structure-Activity Relationship models.
Frank, R1, Sanderson, H1, Hao, C2, Headley, J3, Solomon, K1, 1 University of Guelph, Guelph, Ontario, Canada2 Ontario Ministry of the Environment, Toronto, Ontario, Canada3 National Water Research Institute, Saskatoon, Saskatchewan, Canada
ABSTRACT- Naphthenic acids (NAs), a complex mixture of alkyl-substituted acyclic and cycloaliphatic carboxylic acids, have been identified as the principal toxic components of tailings wastes produced during oil sands refining in Alberta, Canada. Due to the toxicity of these tailings towards aquatic animals, they are collected in ponds on site. Initiatives to remediate these tailings ponds had been dependent on successful characterization methods capable of identifying individual NAs following TIE of extracted NAs mixtures. Recently, there has been progress in the application of GCxGC-TOF/MS to identify individual NAs within NAs mixtures based on their ring family and molecular weight. The first tier of the NAs risk characterization is a (Q)SAR study investigating the toxicity of NAs previously identified in literature and also the principle components of an environmental mixture collected from Syncrude Canada Ltd. The (Q)SAR analysis was performed using the ECOSAR program from the USEPA EPIWIN v.3.10 package. The predicted highest toxicity for each compound, in their neutral form as opposed to their naphthenate ionic form, was used in the analysis predicting acute and chronic toxicity to fish, daphnids, and green algae. The results from the literature NAs sample showed that toxicity increased with increasing carbon rings within the structure (varying z - families) and also with increases in molecular weight. Increasing molecular weight had a greater effect on fish baseline toxicity than did increasing the number of carbon rings. The toxicities for molecular weights varied by a factor of 8 while the toxicities for z - families varied by a factor of 3. (Q)SAR analysis of the environmental Syncrude sample showed that greater than 70% of the entire mixture was ′very toxic′ using OECD classification guidelines, and the NAs component was the most toxic. Work is continuing to extend the findings to the naphthenates found in natural environments with a focus on laboratory toxicity studies.
Key words: QSAR, naphthenic acid, oil sands, tailings pond