Slits from a small lake in Karelia may be beneficial to people

Newswise — Russian limnologists have investigated the chemical composition of a small reservoir in the north-western part of Russia and have found out that sediment cores (slits) meet the standards of heavy metals concentrations. The scientist have established that the lake is clean despite the close proximity of a railway and a village. Theoretically, the lake’s sediment cores may be used in agricultural work or medicine. The work of scientists was published in Advances in Environmental and Engineering Research magazine.

It is known that sediment cores (or silts) enriched with organic substances and a number of trace elements are regarded as minerals. In production geology such sediments are called sapropel. It is mined in Russia, Belarus and the Baltic States. The most promising regions of our country for mining sapropel are the lake regions of the Northwest of Russia, the South Urals and Siberia. The most popular application areas of lake silts are agriculture (fertilizers, animal food) and medicine (therapeutic mud, the manufacture of medicines). For example, there are operating resorts in Karelia and the Arkhangelsk region that offer people mudbaths filled with specifically lake sapropel.

Scientists from the Karelian and The Kola Science Center of the RAS have investigated the chemical composition of sediments in a small lake called Okunozero, situated in the southern part of the Republic of Karelia. It was previously known that the reservoir silts have high levels of organic material — more than 87% of organic matter, relative to the total mass of sediments. But nobody has conducted an analysis of  the concentration of microelements and heavy metals, which is crucial when evaluating the practical use of lake silts. The limnologists have selected core samples of modern layers of the lake’s sediment cores and evaluated the content of nine elements, including lead, cadmium and zinc. Based on obtained the data for metals, the scientists have also calculated index values for evaluating the level of the reservoir’s anthropogenic load.

The research has shown that the average content of heavy metals in lake sediments Okunozero does not exceed the background levels for the Karelia region. The only exception is lead and cadmium (exceed in 9 and 2 times, respectively), which is typical for lakes situated in the relatively clean parts of Northwest Russia. Both metals are agents of long-range atmospheric transport gained from industrial emissions all over Earth's northern hemisphere. The same data are obtained when studying lakes in other regions of Russia and other countries — Finland, Japan, Canada. Russian scientists have also determined that regarding the domestic state standards for lake sapropel, lake silts may be safely used in agriculture. In conclusion, the researchers have evaluated the overall environmental health of lake Okunozero based on anthropogenic load index (PLI) and potential environmental risk index (RI). The first indicator showed that the lake is experiencing low anthropogenic load, and the second one has revealed no dangers from anthropogenic pollution. It is known that the fact that the index value of a potential ecological risk is lower than 150, it tells us that the reservoir and its silts are relatively clean. In case of Okunozero the RI index value varied from 92 to 150.

The material was prepared with the financial support of the Russian Ministry of Education and Science within the framework of the federal project "Popularization of science and technology".