Aluminium and sulphate in acidic soils and groundwaters on the Swedish west coast

Acidic groundwaters and soils in Halland County (Hallands Iaen), southwest Sweden, have been investigated with respect to conditions of soluble aluminium (Al) and sulphate (SO42-). Basic Al-sulphate, Fe-oxide, Al-oxide, Al-hydroxide and clay minerals, are discussed and evaluated in their roles for governing Al and SO42- in the groundwaters. Based on this investigation, it is suggested that Al3+ solubility is controlled by amorphous Al-hydroxide. The SO42- in the groundwaters will depend primarily on the H2SO4 input. The H2SO4 load enhances soil mineral weathering which enhances the production of Fe-oxides, i.e. anion exchange surface sites, to which groundwater SO42- attain adsorption equilibra. The factors that control solubility of Al and SO42- are both influenced by the acidity in the soil catenas which in the area largely depend on the H2SO4 input. Clay minerals such as illite, smectites, halloysite, and variable composition Al-silicates do not exert strong control on Al in the groundwaters investigated. 39 refs., 5 figs., 1 tab