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

1.3. LAKE KEUDSHERJAUR Lake Keudsherjaur (watershed of the River Pechenga) is located 20 km to the south of the town of Nikel. It is a small (area of the lake 0.11 km2), shallow-water (maximum depth 6 m) oval lake of glacial origin, with a maximum length of 4.0 km and maximum width 1.8 km. The points of maximum depth are scattered throughout the whole water body. According to the landscape type, the watershed area belongs to the forest- tundra zone with heights of up to 251.8 m.The lakeshores are waterlogged, peaty and covered by shrubs and birch stands. The water of the lake is colourless but, during flood and heavy precipitation periods, the colour of the water increases to 39 deg, and becomes slightly yellow­ ish. Brown silt deposits begin immedi­ ately at the waterline. Physico-geographica characteristics Watershed River Pechenga Latitude 69°08.853' Longitude 30°09.193' Height above sea level, m 211.8 Maximum length, km 4.0 Maximum width, km 1.8 Maximum depth, m 2 Area, m2 4.66 Watershed area, km2 10.25 Study period 1990-2005 1.3.1. Hydrochemistry The water of the lake is close to neutral and is characterized by low total mineralization values (average 14.7 mg/l) and alkalinity (average 83 peq/1). During flood periods, the pH falls to 5.94 and then increases back to 6.50, i.e. oxidation processes do not develop due to the buffering capacity of the water. The lake is characterized by low concentra­ tions of base cations and anions, sodium (average 1.64 mg/l) and bicarbonate (average 5.1 mg/l) predominating. The maximum degree of pollution of the lake occurred during the period of ex­ tremely high emissions from the smelter in the late 1980s and early 1990s. The maxi­ mum concentrations of most elements, especially sulphate (up to 8.4 mg/l), Cu and Ni, occurred during this period. At the present time the concentrations of these elements in the water are lower. The annual chemical cycle in the lake is characterized by the fact that, during flood and high precipitation periods, the inflow of humic-rich water increases and mineralization is reduced to 11.4 mg/l, the oxidizability increases and the pH falls. During low-water periods, mainly in winter and autumn, and when the flow of ground water increases, the total mineralization increases slightly to 25 mg/l, the oxidizability is reduced and the pH rises. Hydrochemical properties pH 6.41 5.94-6.75 Electrical conductivity, mS/cm 25 19-38 Ca, mg/l 1.54 1.20-2.43 Mg, mg/l 0.74 0.57-1.20 Na, mg/l 1.64 1.31-2.33 K, mg/l 0.33 0.29-0.40 HC03, mg/l 5J. 3.7-7.8 S04, mg/l 3j5 2.2-8.4 Cl, mg/l 18 1.4-2.4 Total mineralization, mg/l 14.7 11.4-25.0 Alkalinity, цед/І 83 60-128 Catalogue of Lakes in the Russian, Finnish and Norwegian BorderArea