Save Me CO3: A Dynamic Equilibrium Analysis of kH, pH, and CO2
Tienlan Sun
Sir William Osler Elementary
Floor Location : J 178 D

A balanced carbon dioxide (CO2) concentration plays a pivotal role in a planted freshwater aquarium, but controlling the dissolved CO2 level within the water is a tedious and multivariable process. In contrast, the regulation of carbonate hardness (kH) is relatively straight-forward and could possibly provide a more simple alternative. If kH were to be regulated to an extent where the free-floating hydrogen concentration (pH) were to be near entire stability, the concentration of CO2 (dictated by pH and kH) would be consistent, denying any further acidification effects from excessive CO2 injection. However, there is no existing quantified measurements regarding the buffering effects of kH on CO2 acidification and the negative effects of increasing kH within a planted aquarium. The goal of this project is to investigate and quantify the buffering effects of kH on CO2 acidification in water through an experimental analysis of the dynamic equilibrium of kH, pH, and CO2. In order to measure the buffering effects of kH, an in-lab experiment was conducted with CO2 injection into water primed with varied kH values. The experimental results indicate that increasing kH resulted in a higher pH saturation/equilibrium point, where the corresponding CO2 concentration would be sufficient for plant photosynthesis and suitable for fish respiration. However, the study also shows that the kH buffering solution inflicted a dramatic pH increase upon addition and was unable to deny CO2 acidification when CO3 dominated as the main form of kH, during the start of injection. These undesirable effects of the buffering solution will have detrimental effects towards aquarium inhabitants. Based on the findings of the experiment, a new set of criteria was created to identify a more effective buffering mechanism.