Why is Lake Gardsjon acid? An evaluation of processes contributing to soil and water acidification

An evaluation was made of the relative importance of atmospheric acid deposition compared with the internal proton fluxes for the soil acidification in a coniferous forest catchment on the Swedish west coast. A proton budget indicated that the atmospheric deposition contributed with 40-55% of the total proton input to the soil. The recent acidification of the nearby Lake Gårdsjön is likely to have been caused by a combination of direct atmospheric deposition on the lake surface and an increased flux of protons and aluminium from the drainage area. This latter increase seems to be caused by an increase of the sulphate flux and by soil acidification, both processes being significantly influenced by the atmospheric deposition. Direct deposition of protons plus SO₂ on the lake surface accounts for 37-44% of the proton input to the lake.