Citation: Liggio, John, et a. “Quantifying the Primary Emissions and Photochemical Formation of Isocyanic Acid Downwind of Oil Sands Operations.” Environmental Science and Technology, Article ASAP. doi: 10.1021/acs.est.7b04346
They’re what make Canada, our neighbor to the north, such an energy powerhouse on a global scale. 97% of Canada’s 1.75 trillion barrels of reserves are contained in these oil sands, placing Canada third in terms of global reserves, just behind Venezuela and Saudi Arabia and representing 75% of North America’s supply.
Figure 1. Athabasca oil sands of Canada. Source: Wikimedia Commons.
To many, these reserves represent energy independence for North America. But for these oil sands to be useful, they have to make it to American refineries.
This problem might be starting to feel familiar; in the past few weeks, several major pipelines in the US have been in the news, for spills and major legislative changes (see here, here, here, here, here, and here, all from the last two months). While the history of the pipeline is fascinating, the truth is, there will always be risks when we transport oil in any form from point A to point B. We have to manage our priorities as we try to feed our energy using cars and homes as well as mitigate sources of climate change and protect drinking water resources.
Focusing on pipelines, however, skips the beginning of the oil sands journey. To mine the oil sands, a mixture of silica, water, clay particles, and the valuable oil droplets, called bitumen, two methods can be used (see Figure 2). For deep deposits, steam is pumped underground; the resulting mixture is less viscous and can be pumped to the surface. More shallow deposits are surface mined using open pits. Only the bitumen can enter the pipeline, so the mixture has to be processed before heading to the pipeline, where it’s destined for further refining at American refineries.
Figure 2. Anatomy of an oil sand deposit. Source: Oil Sands Magazine.
These rising action pieces- the mining, the initial processing, and the transport to the pipeline – sometimes get lost in the big picture. When we think about pipelines and oil, we tend to think really big: carbon dioxide (CO2) emissions, climate change, large scale oil spills.
But the initial parts of the journey deserve another look: what happens on the oil sands operations site itself? Asking that question, John Liggio and his team at Environment and Climate Change Canada took a magnifying glass to an operations site over the Athabascan oil sands in northern Alberta and found something interesting coming out of operations: a toxin called isocyanic acid.
Isocyanic acid isn’t a new toxin; first noticed and attributed to burning biomass, it’s been found in other types of combustion too. If you inhale this acid, it can dissolve in your blood and modify proteins through a process called carbamylation, which has been associated with negative health effects such as atherosclerosis, cardiovascular disease, rheumatoid arthritis, renal failure, and cataracts. Isocyanic acid is considered one of the most dangerous inhalation toxins; exposure to even extremely low concentrations can cause the carbamylation process.
If you picture a dense, urban area, you can imagine that, with all the combustion, there’s bound to be high levels of isocyanic acid. Oil sands operations tend to be in remote, rural areas- so what’s the problem?
Figure 4. An employee walks past a hauler truck in Alberta, Canada. Source: Financial Post.
The answer is these bad boys- big off-road diesel operated trucks used to cart the oil sands from the open surface mines across the site.
What Liggio showed in this recent paper is novel in that they were able to demonstrate that direct emissions (called primary emissions) of isocyanic acid from tailpipe exhaust aren’t the only danger here; there are also secondary emissions– other vapors released from these trucks that react with sunlight to become isocyanic acid. This increases the total emissions coming out of an oil sands operations site overall.
What is exciting to me as an engineer is how the group was able to show this problem in several different ways. They proved that the exhaust coming from off-road diesel trucks could transform into isocyanic acid under lab conditions- but anyone who’s worked in the field and in the lab knows that working in the two settings aren’t always the same.
To measure isocyanic levels in the field, the Liggio team measured chemical levels in the air from aircraft. Using a total of 13 flights and flying in a box pattern, the team was able to study how exhaust fumes changed with sunlight by sampling at various points. Using a model called TERRA, they were able to find that secondary emissions process was rapid, occurring in less than four hours.
Figure 5. At left: a latitude/longitude map showing the route traveled by aircraft measuring isocyanic acid (HNCO). The flight routes sampled points at various altitudes. These data points generated concentration “screens” (at right). These were used to determine secondary emissions (values shown in yellow in right image). Source: reprinted with permission (see below). Copyright 2017 American Chemical Society.
So, the total contribution from oil sands operations, primary and secondary, is greater than all the other sources of isocyanic acid- namely other vehicle operations and wildfires. The primary contribution alone is on par with the entire Canadian on-road vehicle fleet, and is greater than estimates for the California South Coast Air Basin, including Los Angeles.
Figure 6. Daily primary and secondary isocyanic acid emissions from oil sands activities compared with other source estimates. Source: reprinted with permission (see below). Copyright 2017 American Chemical Society.
While the results indicated that there can be high variation in the level of enhancement for secondary emissions of isocyanic acid, the daily emission rates do indicate that the oil sands operations could potentially contribute to contamination of downwind communities.
In order to see if the concentrations of isocyanic acid were actually related to oil sands operations, the Liggio team also examined the nearby towns of Fort McMurray (population 66,000) and Edmonton, (population 900,000). What they found was surprising: both places had similar levels of the chemical as Pasadena, just south of Los Angeles in California, or Toronto. While Pasadena and Toronto’s isocyanic acid levels come from high numbers of cars, however, Fort McMurray and Edmonton’s sources come from cars and oil sands.
What’s more curious, though, is the changing impact of the oil sands: if the wind blows just right (northerly), the isocyanic acid levels increase by 10 times for long periods (12-24 hours). Closer communities, like employee work camps, of course, would see even higher levels of isocyanic acid in the air.
Figure 7. The heat map (A) shows monthly average total isocyanic acid (HNCO) for the period studied (August 15th to Sept 16th, 2013) using computer simulations. The pie chart top left (B) shows the average relative contribution of various isocyanic acid (HNCO) sources at Fort McMurray, Alberta (City Center). See paper for details. Source: reprinted with permission (see below). Copyright 2017 American Chemical Society.
While this concentration is still below the health limit, that might not be the case for long. Expansion of Alberta’s oil sands operations- more mining, more refining, and of course, more trucks – would increase local and regional levels of isocyanic acid.
The story of oil sands and oil in general is long, and much more convoluted than your role- pumping gas into your car, maybe. The impact of oil combustion on human health goes beyond the big picture of clean energy and climate change; zoom in, and you’ll see other factors, like this isocyanic acid, hiding in plain sight, in the rural oil sands of Alberta.
Note: Images reprinted (adapted) with permission from Liggio, John, et al. “Quantifying the Primary Emissions and Photochemical Formation of Isocyanic Acid Downwind of Oil Sands Operations.” Environmental Science & Technology, June 2017, doi:10.1021/acs.est.7b04346. Copyright 2017 American Chemical Society.