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

2.8.1. Hydrochemistry The proximity of the sea has aconsider- able influence on the water quality. The pH of the water in the lake is close to neutral, and the water has a low total mineralization (average 16.3 mg/l) and alkalinity (average 22 peq/1). During flood periods the pH drops slightly, i.e. oxidation processes do not develop due to the buffering capacity of the water. The lake has low concentrations of base cations and anions, with sodium (aver­ age 3.20 mg/l) and chloride (average 5.15 mg/l) predominating. The annual chemical cycle of the lake is characterized by a slight reduction in the oxidizability and pH of the water during flood periods when the amount of precipitation and inflow of humic wa­ ter increase. 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 vegeta­ tion period are 4 pg/l andl54 pg/l, cor­ respondingly. According to the concentrations of mineral nutrients, the lake is classified as oligotrophic. The colour values and the organic matter (2.1 mg/l) and Fe con­ centrations (average 6.5 pg/l) are typical of small water bodies in the region. Dur­ ing flood periods in the summer the av­ erage concentrations of P 0 43' and N 0 3", which determine the lake productivity, are low. Hydrochemical properties pH 6.26 6.03-6.46 Electrical conductivity, 31 mS/cm 30-32 Ca, mg/l 1.24 1.05-1.36 Mg, mg/l 0.68 0.59-0.74 Na, mg/l 3.20 3.14-3.27 K, mg/l 0.31 0.29-0.36 НСОЗ, mg/l 1 4 0 . 8 - 1.8 S04, mg/l 4.37 4.05-4.57 Cl, mg/l 5.15 5.10-5.43 Total mineralization, 16.3 mg/l 14.9-17.4 Alkalinity, peq/l 22 13-30 Water colour, deg. 4 3-5 NH4, цд/І 7 4-13 N03, цд/І 3Z 32-51 Total N, цд/І 107 80-154 P04, цд/і 1 1-1 Total P, цд/І 3 1-4 Fe, цд/І 65 3.8-11.4 Cu, цд/І 18 0.3-3.3 5.8 Ni, цд/І 5.4-6.9 21 Al, pg/l 18-24 Pb, цд/І 03 0.2-0.4 The low micronutrient concentra­ tions of the water entering the water body reflect the low level of chemical weather­ ing of the minerals present in the watershed area. Although the watershed of Lake Kobbholmvatn is relatively distant from the Pechenganickel smelter (distance of 34 km), it is still subjected to the effects of emissions from the smelter. The main pol­ lutants are sulphur compounds and heavy metals (Ni, Cu, Co etc.). Despite the fact Catalogue o f Lakes in the Russian, Finnish and Norwegian BorderArea