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.

1. Summary of the Sediment Investigations 1.1. Introduction Lake Inari and the Paz River form one o f the greatest water system in the Northern Fennoscan- dia. The drainage basin o f this system includes the adjacent areas of Russia, Norway, and Finland. Within these areas, the anthropogenic load consists mainly o f heavy metals released by the melting furnaces o f the “Pechenganikel” Plant and domestic sewage from populated areas, which are located within the drainage basin o f this system. The river is strongly regulated for hydroelectric power production. Therefore, the investigation o f the ecological situation and im­ provement o f environmental conditions in the Paz River basin are important for these three countries. Last century in many countries o f the world the increasing attention attracts high latitude re­ gions having richest mineral resources. Development o f mineral deposits, processing of mineral raw material, reception o f a final product (including, chemical fertilizers and metals) have re­ sulted in infringement o f natural geochemical circulation of elements in Arctic and Subarctic ecosystems. The mining and metallurgical activity has significant negative influence on fresh- waters o f high latitude, which are extremely sensitive to anthropogeneous stress owing to low levels o f masses and energy volumes (Moiseenko et al., 1996, 1997; Moiseenko, 1997). The Paz River basin is one o f industrial centres o f ecological trouble in the Northern Fenno- scandia with the advanced mining and metallurgical industry. The main pollution sources by heavy metals o f the Kola Peninsula territory are the Pechenganickel and Severonickel Compa­ nies. The significant part o f heavy metals entering in a lake in composition o f waste water and pre­ cipitated on watershed territory are connected and buried in sediments. Therefore their contents in sediments characterize total loading, allow to determine sources o f pollution and to establish historical trends. In the majority o f water systems, the element concentrations in the top several centimetres o f sediments are much higher, than element concentrations in water column. The close connection of microelements (for example, heavy metals) with seston and sediments means, that distribution, transport and availability o f these elements cannot be correctly appreci­ ated extremely by means o f only collection o f water samples and analysis of a soluble phase (Horowitz, 1991). Sediments accumulate many microelements and other polluting substances, therefore can be considered as an informative parameter o f water quality and, simultaneously, source o f secon­ dary pollution for the following reasons: • unbroken sediments contain "historical records" o f the last chemical conditions and allow to establish background levels, to which the existing conditions can be compared; • under influence o f change o f physical and chemical conditions (for example, pH, Eh, dis­ solved oxygen, bacterial activity) the compounds, connected with sediments, can be dissolved in water column, enter to foodweb and have secondary effects for hydrobionts; • inorganic substances, some rather inert or harmless to environment, can be destroyed or react with others, forming soluble and potentially toxic forms (for example, transmission o f elemen­ tary mercury into methyl-mercury (Linnik and Nabivanets, 1986; Moore and Ramamoorthy, 1987)); • sediments are one o f main sources o f pollution and should be investigated for definition o f potential transmission o f polluting substances.