The relationship between pH and CO2 levels in Saskatchewan waters
Saskatchewan’s alkaline lakes
Saskatchewan’s lakes are unique in many ways from other Canadian freshwater bodies. Saskatchewan is known for its saline lakes, like Little Manitou, that are so salty that bathers can float as effortlessly as in the Dead Sea. Another special feature is the alkalinity of certain Saskatchewan lakes. This feature, a basic rather than acidic pH, is important as it relates to carbon dioxide (CO2).
What is pH?
pH stands for the potential of hydrogen. It is the abundance of protons (H+) in the water. What this means is that acidic solutions have more protons and a lower pH. For example, lemon juice has a pH of between 2-3. Basic solutions, such as soapy water, have fewer protons and a higher pH. Pure water has a pH of 7 (neutral). The pH of lakes ranges from a pH of 6 to 9 due to the variety of substances that can dissolve and affect proton concentrations. Factors that contribute to the variety of pH readings include land use, climate change, aquatic sediments, the amount of internal solutes, and basic and acidic interactions from the atmosphere. Click here to read more on pH.
The relationship between pH and CO2
When lake water is basic, carbon dioxide (CO2), from animal and bacterial respiration, is chemically converted into another form of carbon, keeping the CO2 in the water low. But when lake water is acidic, it stays as CO2. In other words, when CO2 dissolves it forms carbonic acid (H2CO3), establishing an equilibrium between bicarbonate (HCO3) and carbonate (CO3), the two most common ions in aquatic ecosystems. The product of these compounds is known as dissolved inorganic carbon. This demonstrates the relationship that pH and CO2 have with one another. Environmental factors can cause changes in these compounds, which will result in disturbances of pH. The environmental factors that can cause these changes are photosynthesis and respiration because of CO2 either being produced or consumed. Intake of CO2 increases the water’s pH to approximately 8 to 9.2 which will have different implications than a lake that is more acidic.
Saskatchewan’s lakes act as carbon sinks
There is a connection between pH and CO2 levels. pH and inorganic carbon have a cause and effect relationship. Saskatchewan’s lakes are quite alkaline. What this means is that the lakes may act as carbon sinks because of the correlation between CO2 and dissolved inorganic carbon (CO2 chemically converted into another form of carbon, keeping CO2 in the water low).
Acidic versus alkaline lakes
Other regions, such as boreal lakes, are more acidic, meaning they do the opposite. Studies show that boreal lakes modify the concentration of carbon by oxidizing dissolved inorganic matter into CO2 and releasing it into the atmosphere. In contrast, Saskatchewan lakes, being alkaline, causes CO2 to be converted into bicarbonate and carbonate, as mentioned before, resulting in CO2 not being released into the atmosphere but retained. These findings conclude that regions where pH values are higher, such as many lakes of Saskatchewan, could in fact act as carbon sinks.
Ph scale. pH Scale | U.S. Geological Survey. (n.d.). Retrieved June 21, 2022, from https://www.usgs.gov/media/images/ph-scale-0
Finlay, K., Vogt, R. J., Bogard, M. J., Wissel, B., Tutolo, B. M., Simpson, G. L., & Leavitt, P. R. (2015). Decrease in CO2 efflux from northern hardwater lakes with increasing atmospheric warming. Nature, 519(7542), 215–218. https://doi.org/10.1038/nature14172
Datastream. (n.d.). Retrieved June 21, 2022
Finlay. K., Bogard. M. J. (2021). pH of Inland Waters.