Toxicity of Cold Lake Blend and Western Canadian Select dilbits to standard aquatic test species

Abstract Dilbitsare blends of bitumen and natural gas condensatesor crude oils with only limited toxicity data. Two dilbits, Cold Lake Blend and Western Canadian Select, were tested as either unweathered or weathered oils for acute and chronic toxicityto standard freshwater and estuarine organisms. Water accommodated fractions of the dilbitswere characterized for total petroleum hydrocarbons(TPH), polycyclic aromatic hydrocarbons (PAHs), and monoaromatics ( BTEX). Acute toxicity of unweathered and weathered dilbitsranged from 4 to 16 mg/L TPH, 8 to 40 μg/L total PAHs, and 0.7 to 16 mg/L BTEXin Ceriodaphnia dubia, Pimephales promelas, Americamysis bahia, and Menidiaberyllina . Concentrations of weathered dilbitscausing impaired growth ( A. bahia ) and reproduction ( C. dubia ) ranged from 0.8 to 3.5 mg/L TPH and 6 to 16 μg/L PAHs. The two dilbitshad generally similar acute and short term chronic toxicityexpressed as TPH or total PAHs as other crude oils and other petroleum products.