Toxicity assessment of collected fractions from an extracted naphthenic acid mixture.
Recent expansion within the oil sands industry of the Athabasca Basin of Alberta, Canada has led to increased concern regarding process-affected wastewaters produced during bitumen extraction. Naphthenic acids (NAs) have been identified as the primary toxic constituents of oil sands process-affected waters (OSPW) and studies have shown that with time, microbial degradation of lower molecular weight NAs has led to a decrease in observed toxicity. As earlier studies identified the need for an "unequivocal demonstration" of lower molecular weight NAs being the primary contributors to mixture toxicity, a study was initiated to fractionate an extracted NA mixture by molecular weight and to assess each fraction's toxicity. Successful molecular weight fractionation of a methylated NA mixture was achieved using a Kugelrohr distillation apparatus, in which fractions collected at higher boiling points contained NAs with greater total carbon content as well as greater degree of cyclicity. Assays with Vibrio fischeri bioluminescence (via Microtox assay) revealed that the lowest molecular weight NAs collected had higher potency (EC50: 41.9+/-2.8 mg l(-1)) than the highest molecular weight NAs collected (EC50: 64.9+/-7.4 mg l(-1)). Although these results support field observations of microbial degradation of low molecular weight NAs decreasing OSPW toxicity, it is not clear why larger NAs, given their greater hydrophobicity, would be less toxic.
Centre for Toxicology, University of Guelph, Guelph, ON, Canada. frankr@uoguelph.ca
Richard A
RA
Frank
Richard
R
Kavanagh
B
B
Kent Burnison
Gilles
G
Arsenault
John V
JV
Headley
Kerry M
KM
Peru
Glen
G
Van Der Kraak
Keith R
KR
Solomon
D000416:Alberta; D048908:Aliivibrio fischeri / Q000187:drug effects; D001681:Biological Assay; D002264:Carboxylic Acids / Q000737:chemistry / Q000302:isolation & purification / Q000633:toxicity*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003978:Diazomethane / Q000138:chemical synthesis / Q000737:chemistry; D007221:Industry; D049449:Luminescence; D008745:Methylation; D008970:Molecular Weight; D010578:Petroleum; D021241:Spectrometry, Mass, Electrospray Ionization
D002264:Carboxylic Acids; D010578:Petroleum; D003978:Diazomethane; C046170:naphthenic acid