Diaromatic sulphur-containing 'naphthenic' acids in process waters.

Area of Science:

• Environmental Chemistry
• Organic Geochemistry
• Toxicology

Background:

• Industrial process waters contain polar organic compounds, including naphthenic acids (NA) from petroleum residues.
• Some NA exhibit acute and sub-lethal toxicity to aquatic organisms like fish.
• Sulfur-containing acids, detected but unidentified, may contribute to NA toxicity.

Purpose of the Study:

• To investigate and characterize sulfur-containing acids in oil sands process water.
• To determine the potential toxicity and estrogenicity of these sulfur compounds.

Main Methods:

• Isolation of a sulfur-rich NA fraction using argentation solid-phase extraction.
• Analysis via multidimensional comprehensive gas chromatography-mass spectrometry (GCxGC-MS).
• Detection using GCxGC-sulfur chemiluminescence detection (GCxGC-SCD).
• Structure elucidation aided by synthesized standards and computer modeling.
• In vitro toxicity and estrogenicity assays using trout hepatocytes.

Main Results:

• A sulfur-rich fraction (12% of NA, 1.5% sulfur) was isolated.
• Structures of some sulfur-containing acids were partially identified, suggesting diaromatic sulfur-containing alkanoic acids.
• Computer modeling indicated potential toxicity similar to known compounds.
• The isolated sulfur-rich fraction exhibited no toxicity or estrogenicity in trout hepatocytes in vitro.

Conclusions:

• The structures of sulfur-containing acids in oil sands process water were partially elucidated.
• The lack of observed toxicity in vitro suggests that the concentrations of these sulfur acids were too low to elicit effects.
• Further investigation with different samples is recommended to fully assess the impact of these compounds.