Acidification of Sensitive Soils: Cation to Aluminum Ratio

The long-term soil acidification monitoring program also looks at several other measures of soil impact. These measures are related to ion concentrations and aluminum toxicity. One such measure is the Base Cation to Aluminum ratio, which is a reflection of base cation concentrations in the soil compared to aluminum. Soil acidification results in loss of base cations. A reduction in soil pH enables mobilization and plant uptake of aluminum, which is toxic to vegetation. The ratio of these parameters is an indication of the potential for impact on vegetation. When the base cation:aluminum ratio drops below a threshold level of 1, vegetation damage is expected. It should be noted that although the overall forested site average is well above the threshold, the Fort McMurray site has a very low base cation:aluminum ratio (slightly over 3). This is very close to the threshold level of 1 where damage is anticipated.