MODELING GEOCHEMISTRY AND LAKE PH SINCE GLACIATION AT LAKE-GARDSJON

The soil acidification model SAFE was modified to calculate historical changes in geochemistry and runoff since the last glaciation ended at the Lake Gardsjon Fl catchment 12 000 B.P.. Changes in runoff pH and ANC, soil weathering rate, soil mineralogy, soil texture and base satu ration was also calculated. The changes in mineralogy compared favorab le to data. Modeled historic weathering rates were slightly higher tha n data suggest, while present weathering rate was somewhat to low, 37 mmol(c) m(-2) yr(-1). The weathering rate was very high immediately af ter the last glaciation, and decreased as the smaller particles were c onsumed by weathering. The calculated runoff pH follows the pattern of the paleo-inferred pH. SAFE suggests a natural depletion of base cati ons in the C-layer.