Lake acidification monitoring
Client
Rio Tinto
Place
Kitimat, BC, Canada
Year
2012 - 2025
Design
Critical acid loading: D. Marmorek, ESSA
Field ops/ Limnology: C. Perrin, S. Bennett
Safety: F. Seiler
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Product
High quality chemical data and limnology for critical acid load modeling done safely
Photographer
C. Perrin
Remote lakes of the northwest coast of Canada are spectacular; jewels nestled in forest covered valleys and between snow covered jagged mountain peaks rising to 1,800 m. Air access only. No roads. No boats. Exciting! Some of these lakes are exposed to emissions of sulfur dioxide, and acidity coming from the Rio Tinto aluminum smelter in Kitimat. We developed an aerial sampling method, a quality control system, and safety protocols, ensuring highest quality data for modeling and monitoring lake health in a 13 year partnership with ESSA Technologies supporting Rio Tinto for lake protection.
Safety is paramount in this project. Every detail is important. Helicopter operations are preferred. Drones with sampling gear have been found not be effective due to long distances from ground ops. With helicopter procedures an entire set of carefully selected exposure and control lakes are all sampled in a single day with ease, without landing except for fuel. Worker fatigue is reduced from what it can be during repeated landing and takeoff. Utmost care and attention avoids sample contamination. Its just easy, which makes it safe, which makes samples for chemical analysis ideal, which makes lab data perfect.
pH is one of the easiest measurements to make and one of the hardest to do well. Seems odd, but in the very low conductivity waters of the north coast, it is tough to get stable readings that are believable. And the values have to be right, given that differences of 0.2 pH units can mean the difference between exceedance of critical acid loading or no exceedance among the north coast lakes.
We developed standard methods for pH measurement that are customized to low conductance north coast lakes. Testing compared instruments, different types of electrodes, durations between sample collection and measurement, importance of degassing of carbon dioxide, and other factors. Results showed doing the measurements in a field lab using timed criteria for stability points, with a given make of instrument and electrode, no air space in sample bottles, and minimizing exposure to air once measurement begins is the way to go. Much of this is already known. It was just a matter of fine tuning each step.
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Many other attributes of water chemistry are examined in the project by world leading scientists at ESSA Technologies in lake acidification and support limnologists at Limnotek in a process digging into multiple lines of evidence of sensitivity of lakes to acid loading. All has resulted in a comprehensive analysis that builds confidence in understanding the limnology, and reducing uncertainty in protection of remote lakes on the North Pacific Coast of Canada.
