Application of static critical load models for acidity to high mountain lakes in Europe

Critical load models for acidity provide a measure of the sensitivity of surface waters to acid deposition, and can be used to determine critical load exceedance and potential long-term harmful effects. Three static models, the Steady-State Water Chemistry model, diatom model and First- order Acidity Balance model, are here applied to 11 high mountain lakes in Norway, Scotland, the Alps, the Pyrenees and the Tatras. Between five and seven of the lakes show critical load exceedance, depending on the model used. Nitrogen as well as sulphur deposition is important in causing exceedance. Since soil and vegetation cover are generally sparse, geology and lake retention time appear to be key factors in the determination of critical load. Retention of nitrogen is observed, but is unclear whether this occurs within the lake or the terrestrial part of the catchment.