Bio-Markers Clues in Chemical Sleuthing

Their feathers soaked with oil from a spill, a flock of murres founders on the open sea, unable to keep warm or stay afloat. Days later, a team of Environment Canada scientists begins analyzing the gooey substance clinging to the bodies that have washed ashore--a form of chemical sleuthing that can pinpoint the source of a spill with amazing accuracy.

When the Exxon Valdez ran ashore off the coast of Alaska ten years ago, there was no doubt as to the source of the oil that washed over the coastline and threatened the fragile ecosystem. However, millions of litres of oil wash onto Canada's shores each year, much of it from sources unknown. While nearly a third of this comes from municipal wastewater runoff, another significant source is ships that knowingly or unknowingly discharge oil into the ocean. In order to effectively enforce the laws against dumping, both the source and location of the discharge must be proven. And thanks to a chemical "fingerprint" known as a bio-marker, the forensic tools are now at hand.

Every oil contains a bio-marker--a chemical compound that is not readily degraded and that identifies the product in a unique way. In order to find the bio-markers in a wide range of commercial oils, Environment Canada scientists in the Atlantic region and at the Environmental Technology Centre in Ottawa had to characterize more than 300 other compounds found in these products.

To track down the source of a spill, bio-markers detected in a site sample are compared to those detected in the lab. These fingerprints may be the ratio of various compounds found in the oils, or the presence or absence of certain twin compounds. Bio-marker comparisons also tell scientists how much an oil has evaporated, biodegraded or separated, making it possible for them to not only identify the commercial product, but also determine the scene of the crime by figuring out how far it has travelled.

During the past year, there were "mystery" spills between California and British Columbia that caused oil to wash ashore every day for weeks. By using the bio-marker methodology on oil samples, scientists determined that there were actually two separate spill events--one close to shore near California, and the other a more northerly spill that occurred further out to sea. Bio-markers have also been used effectively in several actions in Atlantic Canada to enforce laws designed to protect the environment against oil spills that are either deliberate or caused by carelessness.

Thousands of litres of oil wash up on Canada's shores each year, many from "mystery" spills caused by sea-going tankers.

Environment Canada is currently developing a statistical program on oil signatures that can indicate the exact probability that two samples, identified as a match by chemical analysis, are the same oil. Interest in this new technology has already attracted the attention of countries all over the world, including China, the United States and Spain.

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