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

of dwarf birch and dwarf shrubs. The water of the lake is colourless but, dur­ ing episodes of high precipitation in the summer, the colour ofwater increases to 39 deg and becomes slightly yellowish. There are some boulder beds and sandy beaches with a length of 40 m in the littoral zone. The boulder beds ex­ tend to a depth of about 2 m. The gaps between the boulders are filled with sand and pebbles. Dark green silt deposits are predominant at a depth of ca. 1.5-2.0 m. Physico-geographical characteristics Watershed River Puldshkash— River Nautsijoki— River Paz Latitude 68°45.894' Longitude 28°47.548' Height above sea level, m 182.0 Maximum length, km 1.8 Maximum width, km 1.0 Maximum depth, m 13 Area, m 2 1.25 Watershed area, km 2 13.7 Study period 1989-2007 1.17.1. Hydrochemistry The water of the lake is neutral, with a tendency to acidification; it has a low total min­ eralization (average 17.0 mg/l) and alka­ linity (average 133 peq/1). During flood periods the pH falls to 6.12 and then gradually rises back to 6.66. The lake has low concentrations of base cations and anions, with calcium (average 1.82 mg/l) and bicarbonate (average 8.2 mg/l) pre­ dominating. Severe pollution of the lake occurred during the period of peak emissions from the Pechenganikel smelter in the late 1980s and early 1990s. Maximum concentrations of most elements were recorded, especially of sulphate ( up to 6.9 mg/l), Cu and Ni. Currently the con­ centrations of these elements, as well as of other elements that characterize the state of the water, are lower. The annual chemical cycle of the lake is characterized by a reduction in total mineralization to 12.9 mg/l, an increase in the oxidizability and a fall in pH during flood periods and episodes of high precipi­ tation when the inflow of humic water increases. During low-water periods (mainly in the winter and autumn) and when the inflow of groundwater increases, the total mineralization increases slightly to 25.6 mg/l, the oxidizability drops and the pH in­ creases. The P and N concentrations ofwater are the main criteria used for assessing the de­ velopment of water eutrophication. The concentrations and relationships between the species of these mineral nutrients vary according to the season, and the dynamics is to a greater extent determined by the level of production and, consequently, the trophic- ity of the water body. The highest concentrations of total P in the lake (up to 13 |ig/l) typically occur in the summer and autumn, when the concentration is 2-3 times higher Hydrochemical properties pH 6.66 6.12-6.96 Electrical conductivity, 25 mS/cm 21-34 Ca, mg/l 1.82 1.37-2.51 Mg, mg/l 0.94 0.74-1.29 Na, mg/l 1.38 1.15-1.95 K, mg/l 0.37 0.30-0.52 HC03, mg/l 82 5.7-11.4 S04, mg/l 3.01 2.08-6.90 Cl, mg/l 1.26 0.83-2.28 Total mineralization. 17.0 mg/l 12.9-25.6 Alkalinity, цед/І 133 93-187 Catalogue ofLakes in the Russian, Finnish and Norwegian BorderArea