It’s rare that oil is spilled intentionally. But that is what recently happened at a lake in Ontario, Canada.
Earlier in June, bitumen – a molasses-like product that comes from oil sands – was drizzled into corrals in an unnamed lake in Ontario’s International Institute for Sustainable Development Experimental Lakes Area (IISD-ELA). The reason may seem counterintuitive: to protect future freshwater systems from oil spills.
In giant, test tube-like columns of natural lake water, scientists are studying the physical, chemical, biological and toxicological impacts of the diluted form of bitumen (called ‘dilbit’ for short) on freshwater organisms – from tiny plankton to frogs and fish.
Until now, these kinds of experiments have only been attempted in the laboratory. But lab-based work can’t replicate a real-life scenario. This experiment, the first of its kind in Canada, is an opportunity for scientists to answer the kinds of questions that could help protect Canada’s lakes in the future: What happens to spilled bitumen in freshwater ecosystems? Where does it go? And how can it be cleaned up in the safest, most effective way? That’s because clean up procedures for accidentally spilled dilbit are necessarily different than those for conventional crude oil.
In the weeks leading up to the spill, dozens of students have been labouring at the gravel pit, shovelling sand into bags. They haul their quarry along a muddy, root-filled trail to the lake by lorry and quad bike. Once unloaded, the heavy sandbags are muscled down to the wooden dock to be loaded onto boats. “It’s really cheap cross-fit,” says University of Manitoba student Sonya Michaleski, here for her third summer, with a laugh.
在倾倒稀释沥青之前的几个星期，许多学生已经在采石场工作了很久。他们铲沙装进袋子，然后开着卡车或四轮摩托，沿着树根缠绕的泥泞道路，把这些沙袋运到湖边，卸下来之后放在木制码头上，然后再搬到船上。这是曼尼托巴大学的学生麦考斯基（ Sonya Michaleski）来这里的第三个夏天，她笑着说，“不花钱就能健身。”
Hauling sandbags is one part of her job. Collecting fish slime and fish vomit for analysis is another. Graduate student Sam Patterson explains his role: drawing water from the enclosures before and after the dilbit spill, then placing the black-dotted eggs of wood frogs in the treated and untreated water to see how the exposure affects their development.
The bulk of the data collection will take place this summer and autumn before the lake freezes up. Subsequent analysis by their team of more than 30 scientists will be shared first in academic journals, but ultimately with the public.
The IISD-ELA is known for its whole lake experiments. Past work has contaminated some lakes with phosphorus, cadmium, mercury, and synthetic oestrogen, the active ingredient in birth control pills. But never oil.
The experiment – nicknamed Boreal, an acronym for Boreal Lake Oil Release Experiment by Additions to Limnocorrals – won’t be a whole lake experiment, either. Small enclosures restrict the oil spill area and four extra containment measures are in place to avoid contaminating the entire body of water, explains Vince Palace, IISD-ELA’s head research scientist and project leader for a separate oil spill experiment, the Freshwater Oil Spill Remediation Study (Forest).
Still, even this smaller spill area will give scientists a much better idea of how bitumen behaves, and how it affects the environment, than what they are able to mimic indoors in a laboratory.
In a lab, “there are technical problems with what we call scaling – how you go from a small scale to a big scale,” says Bruce Hollebone, an analytical chemist with Environment and Climate Change Canada and a collaborator on the Boreal experiment. “It’s not like model ships where you can test how a canal might work, for example, at a much smaller scale. You can’t do that with oil spills because you’ve got so many things involved, and they all change at different rates when you increase the size.
“Boreal gives us an opportunity to do work not at full scale, but very close to it… and really get a good handle on what happens in these natural settings.”
Plus, oil spills mainly have been studied in the ocean. Even of oil spill studies devoted to freshwater, Hollebone says, “there are vanishingly few that look at boreal ecosystems". (A boreal ecosystem is what many envision as iconic Canadian wilderness: its a landscape of conifer trees and granite outcrops, boggy wetlands and lakes).
“Half of Canada is a boreal ecosystem,” Hollebone adds.
How an oil spill could affect this and other ecosystems has become a controversial issue in Canada. All Canadians are soon to be part owners in a pipeline purchased by the federal government.
Multiple modes of transportation, including pipelines and railways, already move oil through Canada’s boreal ecosystems. Over the past decade, explains Hollebone, Canada has had multiple spills into boreal forest and wetlands. In dealing with these spills, “we are underequipped knowledge-wise,” he says.
One challenge is that bitumen is very viscous, even when it’s diluted with the lighter oil fractions that allow it to flow – as dilbit – through pipelines. When spilled, dilbit behaves very differently in freshwater versus marine systems, says Diane Orihel of Queen’s University in Kingston, Ontario, one of Boreal’s leaders. Among other questions, researchers want to investigate how long diluted bitumen will float in freshwater ecosystems, how quickly the lighter component evaporates, how much actually ends up in the sediment and how quickly it enters and accumulates in the food web.
To track where dilbit ends up, the researchers will work in teams, each targeting ecosystem effects in different categories, such as air, water, sediment, periphyton (the community of tiny organisms that grows on submerged surfaces) and animals like wood frogs and fathead minnows. Then they calculate the mass of polycyclic aromatic hydrocarbons (PAHs) – a family of chemicals found in organic materials like oil, which include known carcinogens – in each section.
The Boreal team will also examine how members of the community differ before and after the dilbit spill. What kinds of bacteria, phytoplankton, zooplankton, bottom-dwelling invertebrates, and insects are there? How many of each? And how does bitumen affect their ability to survive, function, reproduce, and provide food for all of the species that eat them?
Boreal’s lead principal investigator Jules Blais of the University of Ottawa is studying how quickly PAHs from the dilbit spill are accumulated or eliminated from fish. Boreal’s ability to look at biological effects of six different doses of dilbit, all in a natural setting, is unique, Blais says. “No study of this sort has ever been done before,” he says. “By looking at this from low doses to high doses, [and comparing to three enclosures with no doses] we can identify thresholds beyond which we see effects.”
北湖实验的首席研究员，来自渥太华大学的布莱（ Jules Blais）研究稀释沥青中的多环芳香烃在鱼类中累积或清除所需时间。他说，北湖实验能够在自然环境中研究六种不同量的稀释沥青对生物的影响，这是绝无仅有的。 “以前从未做过这种实验，从大量到少量，并和没有沥青的三个围栏圈作对比，因此我们能从对比中确定，一旦越过某剂量界限稀释沥青就会对生态环境产生影响。”
The doses of dilbit have been carefully calculated to mimic recent real-life US and Canadian bitumen and crude oil pipeline spills. In terms of oil-to-water ratios, their highest dose almost approximates that spilled into the Kalamazoo River, Michigan in July 2010 – one of the largest inland oil spills in US history.
Boreal’s researchers will be looking carefully to see how long the spilled bitumen floats on the surface, before sinking to the bottom. Diluted bitumen, a mixture that is about half asphalt, is a sticky problem that’s hard to clean up once it sinks.
Last year a pilot project for Boreal at IISD-ELA spilled bitumen into three land-based outdoor tanks filled with lake water and sediment. That work hinted that weather may play a key role in how long spilled bitumen floats. While initially floating on the surface “very quickly, the density and viscosity of that oil changed, and it began to sink,” says Orihel. The first week of the pilot study was quite sunny, but after a heavy rainfall on day seven, the bitumen all sank.
But that early observation, cautions Orihel, is preliminary. How bitumen will behave in the lake’s newly established giant test tubes remains a mystery waiting to be solved.