Forming chemical composition of surface waters in the Arctic. Case study of lake Inari and the river Paz

Questions of studying the formation of surface and ground waters, their interaction with rocks, development of the basics of their rational use and protection are of great fundamental and practical importance. The influence of the northern Fennoscandian (Baltic) Shield rock composition on forming surface waters' chemical composition in the border area of Finland - Russia - Norway (Lake Inari, the River Paz) using physical-chemical modeling (Selector software package) has been evaluated. For the physical-chemical modeling there have been made two samples of chemical analyses of the most widespread rocks forming the catchment area, with their percentage ratio taken into consideration. Since the catchment area of the prevailing majority of streams feeding Lake Inari is composed of rocks of the Lapland granulite belt (LGB) and its framing, it will be the main sample (conditional influence of their composition on the chemical composition of waters is about 80 %). The second sample includes gneisses, migmatites, granite-gneisses, granites and quartz diorites typical for Inari terrane (conventional influence of their composition on the chemical composition of waters is about 20 %). It has been found that the chemical composition of the surface waters is formed by interaction of precipitation with intrusive, metamorphic and sedimentary rocks of northern Fennoskandia containing Clarke concentrations of S, C, F, Zn, Ni, Pb, Cu. It has been shown that due to interactions in the water - rock system the chemical composition of Lake Inari waters as well as upper and middle flow of the River Paz is formed by weathering of granulites of the Lapland granulite belt and Inari terrane granitoids of the northern Fennoscandia. The chemical composition of waters in the River Paz downstream is formed by weathering of metamorphosed volcanic and sedimentary rocks of the Pechenga structure and the impact of industrial pollution.