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The nature of dilbit reflects just how much trouble it takes to get petroleum out of Alberta’s oil sands — trouble that continues as it moves to market. The source product is heavier and more viscous than other types of crude oil, so much so that it will only flow through pipelines with the help of additives.����Orihel describes it like “peanut butter.” And, in the same way that it’s hard to sip peanut butter through a straw, it’s hard to pump bitumen through a pipeline. Bitumen must be mixed with a something like a light gas condensate to flow nicely in pipelines. The resulting diluted bitumen, or ‘dilbit’ for short, may have the look of Saudi’s black gold, but it’s not nearly as stable in the environment when exposed to nature’s elements.

Orihel has developed a keen interest in dilbit, which could leak out of pipelines to contaminate nearby rivers or lakes. The implications of that prospect demand her expertise in freshwater ecology and ecotoxicology, which she has also applied to issues from mercury contamination of aquatic food webs, nutrient cycling and harmful algal blooms, to pollution from flame retardants.

“We know surprisingly little��about diluted bitumen in freshwater ecosystems,” she explains. “We don’t understand its environmental fate, we don’t understand its effects on aquatic plants and animals, yet we’re pumping it through pipelines and want to build more pipelines.”

This potential threat of dilbit pollution became all too real in 2010, when a major spill of diluted bitumen highlighted just how much there is to learn about the behaviour of this substance. The accident took place in southern Michigan, where a pipeline operated by Calgary-based Enbridge Inc. ruptured and released some 3.7 million litres of this material, which subsequently made its way throughout dozens of kilometres of the Kalamazoo River.

It was the first time the US Environmental Protection Agency had attempted to clean up dilbit contamination, which in this single case would generate costs of more than a billion dollars over the next four years. The event also spawned a series of major studies to identify the research that would be necessary to understand and address the environmental impact of this product.

There had been no need for such knowledge – no need for dilbit – when most of the world was awash in cheap crude oil, which typically has a consistency that allows it to pour efficiently enough for easy transport. However, as petroleum producers began to extract oil from the bitumen found in Alberta’s plentiful oil sands, they had to deal with the thick, taffy-like nature of this source. Getting it to flow like standard crude became a matter of diluting the bitumen with light gas condensates.��

This relatively simple chemical fix did solve the industry’s transportation problem, even as it added to the supply chain an entirely new product with many unknown characteristics. Nor was this the only aspect of the problem in need of research. While a great deal of work has already been done on how oil spills could affect Canada’s marine coasts, very little scientific inquiry has focused on the lakes and rivers that define the country’s vast interior. In such settings, dilbit can now pose even more of a hazard, as demonstrated by the Michigan spill’s effect on a local population’s source of irrigation and drinking water.

“The pipeline spill in Michigan was a wake-up call for the research community and environmental agencies that — when it comes to dilbit — we’re not dealing with something we’re used to dealing with,” says Orihel. “Our scientific understanding of��dilbit is still only in its infancy, which is why our research is so essential.”

Orihel and her colleagues are helping dilbit science to mature through their current work at the ELA. In summer 2018, they turned one of the region's��lakes into oversized test tubes to study the most fundamental features of dilbit at close range. A set of nine large enclosed tubes, called limnocorrals, each 10 metres in diameter, were sunk into the lakes and anchored to the bottom, effectively isolating the water contained within them. Varying amounts of dilbit were then poured into these chambers, simulating spills of different magnitudes. The researchers then kept a close eye on what happened in each tube in the weeks and months that followed.

For Orihel, this activity was a search for answers to some key questions that are about as elementary as they come:

• What is the fate of dilbit in a freshwater environment?
• What the effect of dilbit on the structure and function of aquatic communities, including bacteria, phytoplankton (microscopic plants), zooplankton (microscopic animals), benthic invertebrates, and emerging insects?
• Which chemicals accumulate in the bodies of aquatic animals, such as mussels, fish, and tadpoles?
• What are the toxic effects of dilbit on these various organisms?��

This work was complicated by the fact that exposure to sunlight, moisture, and fluctuations in temperature can rapidly alter dilbit’s physical properties. However,��by addressing the questions above,�� the hope is that we can advance our scientific understanding of the fate and effects of dilbit in freshwater ecosystems, improve the design of sampling programs to monitor impacts and recovery after accidental dilbit spills, and inform societal and political debates on the environmental risks of building new pipeline projects.

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