Carbonic acid attacks the silicate mineral lattice, a rigid crystal of silicon, magnesium, and oxygen. The crystal structure breaks down; aluminium and silica reorganise into layered aluminosilicate clay sheets. Clay sheets carry permanent negative charge sites across their surfaces — cation exchange capacity. Released calcium and potassium bind to the negative charge sites: CEC increases and nutrients are held against leaching.
Silicate minerals dissolve and release calcium with bicarbonate alkalinity. In acidic soil, hydrogen ions occupy clay exchange sites. Calcium displaces hydrogen from clay surfaces, and bicarbonate neutralises the released protons. Net soil pH rises.
Atmospheric CO₂ dissolves in soil water to form carbonic acid. Carbonic acid weathers silicate mineral, releasing calcium, bicarbonate, and dissolved silica. Calcium and bicarbonate precipitate as carbonate mineral within the soil profile — permanent storage. Remaining bicarbonate is transported through the soil profile into groundwater and waterways as inorganic carbon in solution.