Pristine Tundra Lakes in the North of Murmansk Region (Arctic): Geochemistry of Sediments, Pollution Assessment and Heavy Metal Forms

Studying lakes in background areas of high-latitude regions is an important component of hydrological and ecological research. The article presents new data on the chemical composition of water and recent sediments of six small lakes located in the Natural Park “Rybachy and Sredny Peninsulas” (the Russian Arctic). The main hydrochemistry parameters, including pH, conductivity, alkalinity, the content of main ions (Ca+, Mg+, Na+, K+, HCO3−, SO4−, Cl−), and other elements were measured in the water of selected lakes. Furthermore, concentrations of heavy metals (Pb, Sb, Cd, Ni, Cu, and others) were estimated in the upper layers of recent sediments of the lakes. The integral pollution loan index (PLI), designed for geochemical studies of sediments, was calculated to determine the level of chemical pollution of the lakes. The results showed that, in general, the studied parameters did not exceed the background level. There was no serious impact of the Kola Mining and Metallurgical Company, which is situated 80 km to the west from the lakes. It was revealed that the studied lakes were less contaminated with heavy metals in comparison with the previously researched lakes of urban territories of the Russian Arctic zone. However, the analysis of distribution of concentrations of Ni (up to 127 mg/kg), Cu (up to 370 mg/kg), Pb (up to 90 mg/kg) revealed the influence of long-range atmospheric pollution on lakes of the Natural Park “Rybachy and Sredny Peninsulas”. The fractional analysis of the metals in the sediments showed that the elements were mainly associated with stable compounds of the sediments and, thus, there was an only potential environmental risk for the biota of the studied lakes. Elevated levels of Pb, Cd, and Zn have been found in the water and sediments of Lake Pitevoe, which is likely caused by natural processes. Samples of the sediments also revealed particles of the mineral sphalerite containing traces of Pb and Cd. The calculation of the integral pollution load index (PLI) showed that, from the point of view of sediment geochemistry, the values of the lakes of the Natural Park “Rybachy and Sredny Peninsulas” corresponded to the moderate level of pollution or the absence of any pollution. The exception is lakes where natural geochemical anomalies have been identified. Sediments of lakes Pitevoe and №4 are characterized as polluted (PLI value is more 3). It is should develop recommendations for monitoring the water bodies in the Natural Park «Rybachy and Sredny Peninsulas» and establish measures to ensure safety and counter potential threats to the well-being of people visiting the park.