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Ecology

The lake area used to be clean but pollution is gradually increasing, especially in the northwestern and northern parts which contain the industrial facilities of Petrozavodsk, Kondopoga and Medvezhyegorsk. About 80% of the population and more than 90% of industry of the basin are concentrated in these areas. The pollution from these three cities amount to about 190 million cubic metres (6.7 billion cubic feet) of sewage and drainage water and 150 tonnes (170 short tons) of emissions per year. Human activity results in about 315 million cubic metres (11.1 billion cubic feet) of drain water per year, of which 46% are industrial and household water, 25% is stormwater runoff and 16% is melioration -related drainage. This drainage contains 810 tonnes (890 tons) of phosphorus and 17,000 tonnes (19,000 tons) of nitrogen; 280 and 11,800 tonnes (310 and 13,010 tons) respectively of these elements are removed through the River Svir whereas the rest accumulates in the lake. Ships and motor boats (about 8,000 units) bring oil pollution at the level of about 830 tonnes (910 tons) per navigation year, as well as phenols (500 kg), lead (100 kg) and oxides of sulfur, nitrogen, and carbon.