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

2.9.1. Hydrochemistry The proximity of the sea has a considera­ ble influence on water quality. The pH of the water in the lake is close to neutral, and the water has a low total mineraliza­ tion (average 18.6 mg/l) and alkalinity (average 33 |ieq/l). During flood periods the pH falls slightly, i.e. oxidation proc­ esses do not develop due to the buffer­ ing capacity of the water. The lake has low concentrations of base cations and anions, with sodium (average 3.43 mg/l) and chloride (average 5.76 mg/l) pre­ dominating. 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 concentra­ tions of and relationships between spe­ cies of P and N vary according to the season and the dynamics is to a greater extent determined by the level of pro­ duction and, consequently, the trophic- ity of the water body The average con­ centrations of total P and total N during the vegetation period are 6 |ig/l and 205 |ig/l, respectively According to the concentrations of mineral nutrients, the lake is classified as oligotrophic. The colour values and the organic matter (2.5 mg/l) and Fe con­ centrations (average 10.4 |ig/l) are typi­ cal of small water bodies in the region. During flood periods in the summer the concentrations of P 0 43‘ and N 0 3", which determine the lake productivity, are low. Hydrochemical properties pH 6.40 6.32-6.55 Electrical conductivity, 34 mS/cm 34-37 Ca, mg/l 1.63 1.50-1.70 Mg, mg/l 073 0.68-0.80 Na, mg/l 3.43 3.25-3.58 K, mg/l 0.30 0.27-0.38 HC03, mg/l 2 J. 1.9-2.3 S04, mg/l 4.69 4.58-4.81 Cl, mg/l 5.76 5.24-6.26 Total mineralization. 18.6 mg/l 17.7-19.5 Alkalinity, |aeq/l 33 31-37 Water colour, deg. 6 5-6 NH4, цд/І 6 3-9 N03, цд/І 10 6-13 Total N, (jg/l 118 81-205 P04, цд/І 1 1-1 Total P, цд/І 4 3-6 Fe, цд/І 10.4 6.8-13.0 Cu, цд/І 11 1 . 2 - 2.6 Ni, цд/І 37 3.0-4.5 32 Al, цд/І 24-38 0.4 Pb, цд/І 0 . 2 - 1.0 The low micronutrient concentra­ tions of the water entering the water body reflect the low level of chemical weathering of the minerals present in the wa­ tershed area. Although the watershed of Lake Langvatn is relatively distant from the Pechenganickel smelter (distance of 34 km), it is still subjected to the impact of emis­ sions from the smelter. The main pollutants are sulphur compounds and heavy metals (Ni, Cu, Co, etc.). Despite the fact that emissions from the smelter have been reduced Catalogue o f Lakes in the Russian, Finnish and Norwegian BorderArea