Contract EVK1-1999-00087 - RECOVER:2010

Part of the 'Sustainable Management and Quality of Water'

Ecosystem Functioning

Directorate General Research

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Czech Republic and Slovakia

Tatra Mountain Lakes

Bohemian Forest

Tatra Mountain LakesAll Czech sites are small lakes located in spruce-forested catchments in the Bohemian Forest along the border with Germany and Austria, in the largest woodland area in central Europe. Lakes are 200 km or more, south of major sources of emissions concentrated within the co-called Black Triangle of north-western Bohemia, southern Poland, and eastern Germany. Lakes Plesne and Zdarske are situated on granite, the rest on gneiss (mica schists). Rocks are usually covered by 1 to 5 cm of forest humus and total depth is only 0.1 to 0.5 m. Present (1998) S-deposition is ~ 1.3 g.m-2yr-1 , about 70 % lower than in the mid-1980s. Nitrogen deposition is variable (1 and 2 g m-2yr-1) and declined by 20 to 30 % around 1990. Long-term changes of the lake water chemistry are studied by regular sampling in summer (July), during the autumn overturn and irregularly in other seasons. Temporal changes of all major solutes and selected trace elements in water of lakes has been monitored since 1984. Four chronically acidified lakes (Cerné, Certovo, Prasilske and Plesne) exhibited a decrease in the concentration of strong anions at rates of 3.6 to 8.8 µeq L-1 yr-1 over the whole period 1984 - 1999. In addition to a decrease in SO4 (by 56 to 101 µeq L-1 , Fig.1) a decrease in NO3 (18 to 35 µeq L-1) and Cl- (5 to 10 µeq L-1) was also observed (Fig. 2). A multi-year decrease in NO3 in acidified lakes was observed for the first time in the Bohemian lakes. Average SO4 concentrations have been decreasing since 1986 and the annual decline of SO4 in lake water was related to SO4 concentrations in the acidified lakes. Lakes are now more sensitive to climatic variation causing ,e.g, temporal increase of SO2 in winter 1995 - 1996. A limited amount of longer-term data suggests that the NO3 concentrations have increased probably steadily in Cerné, Certovo and Prasilske lakes over the period 1936 to 1987 (Fig. 2). These data also suggest that NO3 concentrations in Cerné and Certovo lakes peaked near the beginning of the study period (1985-1988) and contributed up to 50 % of the anthropogenically induced increase in strong anions (primarily SO4 and NO3) in the lake waters. The decrease in the NO3 concentrations, especially in Certovo and Cerné lakes, has been relatively fast around 1990 (Fig.2). Besides nitrogen deposition, rate of organic matter decomposition, bioconsumption and 'acid stress' generally are factors affecting nitrate concentrations. The change of strong anions in Cerne, Certovo and Plesne lakes was accompanied by a decrease in Al, Ca, Mg and K contents (but not Na) and an increase in pH (rate of 0.009 to 0.023 pH yr-1).

Figure 1: Mean sulphate concentrations in epilimnetic waters in Bohemian Forest lakes

Mean sulphate concentrations in epilimnetic waters in Bohemian Forest lakes

Figure 2: Changes in nitrate concentrations in Cerné, Certovo and Prášilské lakes from 1936 to 1999. - Cerné Lake, - Certovo Lake, - Prášilské Lake; 1936-1980 data taken from Jírovec and Jírovcová, 1937; Procházková and Fott (personal communication)

Changes in nitrate concentrations in Cerné, Certovo and Práilské lakes from 1936 to 1999.

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Results from Czech Republic and Slovakia

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Upland Uk
Southern Norway
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