3.2. Major ions
Chloride and sulphate were the predominant anions in sampled waters (and presumably also bicarbonate, which was not measured, yet its concentrations estimated from the ionic balance approximated the concentrations of calcium ions, and if recalculated to mass, they were the main ions in the collected samples, reaching 311 mg L-1 in P2). Phosphate, nitrate, nitrite and bromide have only been detected in a few samples each, therefore they are not presented in graphs (Figure 3). The highest dissolved solid concentrations have been found in Yedoma-fed creeks (>100 mg/L of chloride and sulphate both), and sulphate was relatively high in most Kolyma river samples. Among cations, calcium was predominant, at the average level of 12.4 mg L-1 in the Kolyma river, while magnesium was usually second, exceeding Ca2+only in P2 sample at 74.2 mg L-1 in the permafrost cliff creeks (DY; Figure 4). Permafrost-fed creeks exhibited relatively high concentrations (approx. 50 mg L-1 or more) of all three cations: Ca2+, Mg2+ and Na+ (Figure 4). If the ionic water type is defined, using the [mval] concentrations of major ions amounting to at least 20% of the anion or cation total (Suppl. Mat. 2 ), three groups of objects emerge: (1) thermokarst lakes and permafrost ice represented the HCO3-Ca-Mg water type; (2) in the rivers, water types varied between SO4-HCO3-Ca-Mg, Ca-Mg-HCO3-SO4 and Ca-Mg-Na-HCO3-SO4, except sample A2 (SO4-Ca-Mg); (3) permafrost creeks were of Mg-Ca-Na-HCO3-Cl-SO4 type.