Soil acidification gradients: Mode of development,status quo and classification

Studies on soil profiles down to a depth of 3.5 m were carried out in the catchment area of the Söse River (western Harz Mts. Germany). The results show that the presence of an acidification front in the soil or unsaturated zone is a normal occurrence. Acidification fronts can be classified on the basis of water flow paths: Type A: front developed under vertical flow conditions, Type B: front developed under conditions of different flow directions, Type C: front developed in the presence of layers of different permeability. Knowledge of the type of acidification front and its depth allows a simple ion-budget calculation to be used to predict whether and when acidification of fresh waters will take place.