RISK ASSESSMENT OF WATER ACIDIFICATION BASED ON LONGTERM HYDROCHEMICAL RESEARCH AT FORESTED CATCHMENTS

Longterm hydrochemical research in forested catchment in Petrohan area has been carried out for risk assessment of water acidification. The time series are 27 years long. Deposition shows declining sulfate and nitrogen. The concentration of base cations has been decreased in both bulk precipitation and surface water showing the decrease of the neutralizing capacity of stream water. The mean value of pH for spring water have been averaged as 5.99 pH units and for stream water at the same catchment area 6,68 pH units respectively. It has been found that the ratio between the sum of base cations (K+, Na+, Ca2+ and Mg2+) and the sum of acidifying pollutants, like nitrogen sulfate and chloride, has been decreased for the period 1986- 2013. Critical loads of acidity, sulfur and nitrogen have been calculated in order to determine the sensitivity of water bodies to the acidifying pollutants and the results obtained showed different sensitivity. The time series analyzing has been shown that all critical loads of acidity, sulfur and nitrogen have been decreased showing the decreasing of the tolerance of the water ecosystems to the acidifying pollutants. The exceedances of critical loads were used to evaluate the risk for acidification