cation exchange capacity basic cation exchange capacity 2021-12-22T17:32:00Z A cation exchange capacity which inheres in an environmental material by virtue of the material's ability to adsorb basic exchangeable cations. BS The basic cation exchange capacity is often expressed as the percentage of the total exchangeable cations which are basic, known as the percentage base saturation. The percentage base saturation is expressed as follows: %BS = [(Ca2+ + Mg2+ + K+)/CEC] × 100