Effects of Fluorine Deposition on the Chemistry of Acid Luvisols

Abstract

The deposition of airborne fluorine by an aluminum smelter in Upper Austria (Central Europe) during 50 years caused a storage of fluorine in the soils up to 170 g m^?2, corresponding to an annual deposition up to 3.7 g m^?2. The proportion of 1:50 water extractable fluorine increased with total fluorine and ranges from 25% to 37% of the total deposition, indicating an increasing risk of groundwater pollution through further fluorine input. The deposited fluorine increased the solubility of exchangeable and ammonium oxalate soluble aluminum. This is explained by ligand exchange of OH^?-groups at the surface of amorphous Al-oxides with consequent dissolution of Al. Subsequently, aluminum was leached and the contents of exchangeable and oxidic aluminum in the topsoils decreased. The released OH^? neutralized protons (H⁺) dissociating from organic matter, causing a significant decrease of the base neutralization capacity, and raising the pH of the soils.