Sandimirov S.S. Catalogue of lakes in the Russian, Finnish and Norwegian Border Area. Finland, Jyvaskyla: Kopijyva Oy, 2008.

The water of the lake is colourless, but it occasionally increases to 41 deg. and become yellowish. 2.4.1. Hydrochemistry The water of the lake is slightly acidi­ fied and has a low total mineralization (average 14.1 mg/l) and alkalinity (aver­ age 116 |ieq/l). During flood periods the pH of the water drops slightly, i.e. oxida­ tion processes do not develop due to the buffering capacity of the water. The lake has low concentrations of base cations and anions, with calcium (average 1.99 mg/l) and bicarbonate (average 7.1 mg/l) predominating. Elevated concentrations of P and N are important criteria when estimating water eutrophication.The concentrations of and relationships between species of P and N vary according to the season and the dynamics is to a greater extent determined by the level of production and, consequently, the trophicity of the water body. The average concentrations of total P and total N during the veg­ etation period are 8 |ig/l and 202 |_ig/l, respectively. According to the concentrations of mineral nutrients, the lake is classified as mezotrophic. The colour values and the organic matter (8.4 mg/l) and Fe con­ centrations (average 138 fig/1) are typi­ cal of small water bodies in the region. During flood periods in the summer the concentrations of P043- and N03-, which determine the lake productivity, are low. Although the watershed of Lake Gjokvatn is relatively remote from the Pechenganickel smelter (distance of 58 km), it is exposed to anthropogenic impacts from the smelter. The main pollutants are sulphur compounds and heavy metals (Ni, Cu, со, etc.). Despite the fact that emissions from the smelter have been reduced to approximately one Hydrochemical properties pH 6.53 6.11-6.73 Electrical conductivity, mS/cm 26 24-28 Ca, mg/l 1.99 1.88-2.08 Mg, mg/l 0.64 0.59-0.71 Na, mg/l 1.68 1.52-1.90 K, mg/l 0.60 0.54-0.67 HC03, mg/l L I 6.5-7J S04, mg/l 2.38 2.15-2.63 Cl, mg/l 1.60 1.39-1.98 Total mineralization, mg/l 14.1 14.7-17.7 Alkalinity, цед/І 116 107-126 Water colour, deg. 37 34-41 NH4, цд/І 9 6-12 N03, цд/і 14 3-34 Total N, pg/1 196 192-202 po 4, мд/і 1 1-1 Total P, цд/І z 6-8 Fe, цд/І 138 100-200 Cu, цд/І 2 1 0.9-5.5 Ni, цд/І 1 2 0.9-1 .6 Al, цд/І 54 40-69 Pb, pg/1 06 0 . 2 - 1.2 Catalogue o f Lakes in the Russian, Finnish and Norwegian BorderArea