COMMENTARY || Contaminant problems in the Athabasca River not overstated

Focus on specific contaminants overlooks complexity of river ecosystem, say scientists.


We disagree with the assessment of Prof. William Shotyk that “contamination problems in the oilsands region are overstated.”

Like Shotyk, previous research (including Kelly et al. 2010, Proceedings of the U.S. National Academy of Sciences) has found that the concentrations of elements dissolved in the Athabasca River were well below Canadian Council of Ministers of the Environment (CCME) guidelines for drinking water.

Most of the elements are carried in suspended particles, which he filters out before analyzing water samples. However, these particles are not inert — they contain a cocktail of toxic elements and petroleum hydrocarbons.

They are ingested by people and animals that drink directly from the river, and may enter the bloodstream. Considering the toxicity of one element at a time also overlooks potential interactive toxicity among elements and between elements and organics.

For example, bitumen-contaminated sediments from tributaries of the Athabasca are as toxic to fish embryos as sediments from tailings ponds. However, the contribution to toxicity of individual elements and petroleum hydrocarbons within those sediments remains unknown.

The fate and behaviour in particulates are also modified in the river ecosystem. A good example is mercury, which can undergo chemical and biological transformation into a potent neurotoxin, methylmercury, that bioaccumulates in aquatic food chains. In the Athabasca system, this has contributed to increasing mercury in the eggs of fish-eating birds and consumption advisories for walleye.

Another example is polycyclic aromatic hydrocarbons (PAHs), some of which are more toxic in sunlight than in the dark. A thorough assessment of toxic contaminants in the oilsands region must include a broad suite of chemicals in both suspended and dissolved phases to understand the true potential ecosystem impact.

Comprehensive water quality monitoring must include water samples under a range of seasons and river conditions. Sampling the river only at autumn low flow as the Shotyk team did, minimizes the apparent contaminant problem because that is when the river carries its lowest load of particles.

Inputs from tributaries that drain the active mining area, which have higher concentrations of contaminants than the mainstream Athabasca River, and input from snowmelt, are also lowest in the autumn when soil erosion from mining activities is least. The acidity of the river in the oilsands area increases significantly during snowmelt, as the result of acid deposition in snow. This too would increase the solubility of many elements, enhancing their mobility into food chains.

The Kelly et al. papers that are so often the focus of Shotyk’s criticisms have been among the most intensively scrutinized science in recent Canadian history. Many studies by the new government-sponsored monitoring program agree well with their assessment that the oilsands industry is an important source of contaminants in the area. Oilsands developments are associated with airborne emissions of contaminants, groundwater seepage from tailings ponds, and wind and water erosion of soils from landscapes stripped of their vegetation and topsoil for mining, road development, pipelines, power corridors, and survey lines.

In summary, focusing only on a few dissolved elements as Shotyk advocates misses important pathways to wildlife and humans, particularly indigenous people, and oversimplifies the complex nature of oilsands contaminants and the Athabasca River itself.

Fortunately, the current monitoring program carried out by Alberta Environment and Parks and Environment and Climate Change Canada measures both suspended and dissolved fractions of a wide suite of water quality parameters.

Results from this program have continued to build upon the Kelly et al. papers, reinforcing the need for better, more integrated scientific efforts.

David Schindler is professor emeritus at the University of Alberta. J.M. Blais is professor of biology and environmental toxicology at the University of Ottawa. P.V. Hodson is professor emeritus at Queen’s University. Peter Dillon is a professor at the School of the Environment, Trent University. Joseph Rasmussen is professor and Canada Research Chair in aquatic ecosystems at the University of Lethbridge.

This op-ed originally appeared in the Edmonton Journal.