Spatial variation of the chemical composition of lake waters in the Tatra National Park

The aim of this study is to determine the factors affecting the spatial variation of the chemical composition of lake waters in the Tatra Mountains. In most cases, the lake waters are acidic and very dilute, with a low ionic content and low conductivity values. In general, HCO3- is the predominant anion and Ca2+ is the predominant cation in the chemical composition of the analysed water samples. Among nutrients, NO3- is the dominant form of nitrogen, but also NH4+ may be found in lake waters. By using principal component analysis (PCA) two factors have been identified that explain 63.6% of the variation in the chemical composition of water. Factor 1, which explains 43.2% of the total variability, is associated with Ca2+, SO42-, HCO3-, Na+, pH and lake area and is related to weathering and atmospheric deposition. Factor 2 explains 20.4% of the total variability and is associated with Mg2+, K+, Cl- and with lake altitude. In terms of chemical composition, based on the projection of cases of the first and second factor, the lakes in the Tatra Mountains may be divided into four groups, representing the following: lakes situated within the subalpine forest at the lowest altitude (<1300 m a.s.l.), characterized by medium mineralization (~14 mg dm-3) and the highest concentration of NH4+ and Cl- (Group I, 8 lakes); slightly alkaline lakes, with the lowest average acidification, medium mineralization (~31 mg dm-3) and the highest concentrations of Ca2+, Mg2+, Na+, K+, HCO3-, SO42-, and low concentrations of NO3- (Group II, 2 lakes); small lakes (<0.01 ha) located within the alpine meadow and the nival zones at high elevations with the lowest mean mineralization (~4.3 mg dm-3), with the highest ammonium contribution to the sum of ions among all lakes and the largest sensitivity to acidification (Group III, 13 lakes); large lakes with high mineralization and slightly acidic pH (Group IV, 26 lakes) and medium mineralization (~31 mg dm-3).