Sandimirov S. Pollution of the Sediments of the Paz River basin / In State of the environment in the Norwegian, Finnish and Russian border area. The Finnish Environment. Finland, Jyvaskyla: Kopijyva Oy. 2007, №6, 98p.

Researches o f the contents o f elements in sediments in reservoirs o f the Paz River basin were carried out within the framework o f the international project “Development and realization o f monitoring of an environment, and the program o f an estimation in frontier area between Finland, Norway and Russia” during 2002 - 2005. These years the chemical composition o f sediments has been investigated on 5 Paz River isolated water areas, in 19 Russian, 14 Norwe­ gian and 11 Finnish lakes, and at all in 49 reservoirs o f the Inari Lake - Paz River system. The aim o f the recent investigations is an evaluation o f accumulation o f heavy metals (Ni, Cu, Co, Zn, Pb, Cd, Hg) and As in the Paz River basin sediments. Four aspects are considered: 1) background concentrations o f the elements; 2) vertical distribution o f the elements in lake sedi­ ment cores; 3) distribution o f the element concentrations in surface sediments; 4) contamination degree o f Hakanson (1980). 1.2. Materials And Investigation Techniques Sediment samples from the different lakes and stations o f the Paz River watersheds on the Fin­ nish, Russian and Norwegian sites were taken from the deepest area o f lakes with the Skogheim (1979) gravity corer and divided into 1-cm thick horizontal layers to facilitate the analysis. These samples were analyzed for their water content (H2O), loss on ignition (LOI) and concen­ trations o f Ni, Cu, Co, Zn, Cd, Pb, Sr, Mn, Fe, Ca, Mg, Na, K, Al, As, Hg and P; the elements were extracted with nitric acid and determined with the atomic absorption spectrophotometer. Hg was determined utilizing cold vapour atomic absorption. The techniques o f preparation and chemical analysis o f samples are described in detail earlier (for example, Dauvalter, 1994). Re­ sults o f these analyses are listed in the separate parts o f the report (Finnish, Russian and Norwe­ gian lakes) and in Appendix. The data on chemical composition o f sediments o f some Finnish lakes have been kindly submit­ ted by the Finnish Environment Institute and Lapland Regional Environment Centre. 1.3. Discussion 1.3.1. Background concentrations of the elements Researches o f the chemical composition o f sediment column allow to restore a history o f pollu­ tion o f lake watersheds and to estimate a degree o f their pollution. Lake sediments can be con­ sidered as a source o f the available ecological information in a time scale. The determination o f undisturbed background concentrations o f heavy metals forms a basis for all investigations o f lake sediments. Sediment samples taken from deepest core layers (usually deeper than 20 cm) allow to determine background concentrations o f elements in investigated lakes. These layers are several hundred years old, according to investigations o f Norton et al. (1992, 1996), Rognerud et al. (1993), i.e., they predate the industrial development in the North­ ern Fennoscandia. These layers reflect the geochemical features o f a drainage basin and permit to assess a degree o f contamination o f water objects, as well as to reveal anomalous concentra­ tions o f metals, which is useful in prospecting for mineral resources (Tenhola, Lummaa, 1979). The long-term human impact on drainage basins o f lakes resulted in changes in the environ­ mental conditions that control the chemical composition o f bottom sediments. Therefore, back­ ground concentrations o f heavy metals are important for determination o f the effect o f industrial activity on aquatic ecosystems. Maximal average background values o f Ni, Zn, Co, Pb are found in sediments o f the Paz River, Cu and Hg - in the Norwegian lakes, Cd - in the Finnish lakes, As - in the Russian lakes. Aver­ 5