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

The quality of the lakes was assessed on the basis of the ion composition and total mineralization, as well as indices depicting the trophic status of the water body (con­ centrations of ions and cations) and the heavy metal concentrations. The acidification of surface water was most clearly evident as a short-term (using during spring flood) reduction in pH (to 5-6) and alkalinity (Aik, |ieq/l). The mineralization index used in Russia is the sum of all mineral compounds dis­ solved in water, i.e. total concentration of anions and cations, as well as dissolved inor­ ganic matter. Total water mineralization is an important hydrochemical characteristic, which determines the fitness ofwater for economic utilization. Eutrophication is the enrichment ofwater systems by mineral nutrients (P and N) and, combined with biological phenomena, is related to an abundant inflow ofmineral components. An excess input and maintenance of high concentrations of mineral nu­ trients in water result in intensive growth of primary production, deterioration of the water environment, and a decrease in its recreational value. Generally, human activities are the primary cause of disturbances in the natural balance and an imbalance in the input ofmass flow into aqueous ecosystems. Arctic ecosystems are the most vulnerable to anthropogenic impacts. The consequences can include qualitative reorganization both at high and lower loads of biogenic elements, a deterioration in water quality, increase in the concentrations of suspended organic matters and a reduction in water transparency, a reduction in dissolved oxygen concentrations in the hypolimnion, and the intensive growth and successive replacement by algae populations and a reduction in the oxygen supply for salmon and whitefish species. Numerous studies have show that the critical levels of P and N in fresh waters, when a transition occurs from the meso- to the eutrophic type, are P >0.01 mg/1 N >0.3 mg/1. tot О Bottom sediments In most water systems the concentrations of elements in the upper layers of the bot­ tom sediments are much higher than those of elements dissolved in the water column. Bottom sediments act as “reserves”of many pollutants. Studying the chemical compo­ sition of bottom sediments provides reliable data about the distribution, geochemical migration and availability of elements and compounds to living organisms inhabiting the water bodies, and it also enables their impact on the ecosystem to be determined or predicted. Data on the chemical composition of bottom sediments are also required for modelling the transport of pollutants in aqueous systems and the environment as a whole, for assessing the geochemical cycles, and for determining the availability of elements in ecological systems. A summary table is presented for each lake giving the organic matter content (LOI%, i.e. loss in weight on ignition) and the concentrations of the main pollutants (Ni, Cu, Co, Zn, Cd, Pb, As Hg) in the uppermost (0-1 cm) and the deepest (pre-industrial lev­ el) layer in the bottom sediments (usually 20-25 cm deep). Joint international studies have demonstrated that the sedimentation rate in the lakes of northern Fennoscandia generally doe not exceed 1 mm per year. As a result, the upper layer provides an index of the recent load on the lake, and the deepest layer the background one, i.e. represent­ ing natural concentrations during the pre-industrial period, when there was no major anthropogenic impact on the environment and aquatic ecosystems. Graphs showing the depth distribution of a number of polluting elements in the lake in question were constructed on the basis of the results of chemical analyses on the bottom sediments. Catalogue o fLakes in the Russian, Finnish and Norwegian BorderArea