STUDY OF ACIDIFICATION, BUFFER CAPACITIES AND THEORETICAL NEUTRALIZATION DOSE OF NATURAL WATERS BY POTENTIOMETRIC pH-TITRATIONS
Water samples were taken during the ice-free period in 1991 from Isojoki river in southwestern Finland to study seasonal and local variations of the water chemistry of the river. In this paper we have especially concentrated on acidification problems and buffer properties of the river water. Except measurements of pH, alkalinity and other parameters, buffer capacities were calculated for water samples at varying pH from potentiometric pH-titration curves. The buffer capacity for the river water is low, normally in the range 0.05-0.10 mmol/l. The same potentiometric pH-curves were also utilized for the calculation of the theoretical lime (calcite) dose, when neutralizing acidified water to a desired endpoint pH value. Mainly due to low buffer capacities the river is very sensitive for acidification. This occurs as pH-shocks during periods of high water flow. These pH-shocks with subsequent release of e.g. aluminium are the greatest threat against Isojoki river as a living watercourse