NATURAL AND ANTHROPOGENIC MOLYBDENUM POLLUTION OF WATER BODIES IN THE CENTRAL CAUCASUS AND ITS BIOINDICATION

T.V. Reutova, F.R. Dreeva, N.V. Reutova

Federal research center “Kabardino-Balkar scientific center of the Russian Academy of Sciences”, ul. Balkarova 2, Nal’chik, Kabardino-Balkaria Republic, 360010 Russia.

E-mail: reutova371@mail.ru

In the region of Central Caucasus there is a large deposit of molybdenum. It was intensively developed for a long time. Mining and ore dressing was done in Tyrnyauz. Further processing takes place in Nalchik, metal smelting from concentrate is in Vladikavkaz. Modern orogenesis and volcanism are still active in this region at present. The aim of the research was the investigation of natural and anthropogenic contents of molybdenum in water and assessing the possibility of indicating the spatial pollution with plants. The investigation was done in 2013–2016. It included the main rivers (Malka, Chegem, Cherek rivers and anthropogenically affected Baksan river) and their glacial and nonglacial (of underground recharge) tributaries in the mountain zone. Concentrations of Mo were determined by AAS method with electrothermal atomization. Besides, leaves and branches of widespread bushes willow (Salix) and sea buckthorn (Hippophae rhamnoides caucasica Rousi) from river valleys were analyzed for Mo content. The later served as an indicator because it selectively accumulated molybdenum up to 200 µg/g on the tailing dump.

Average concentrations in the most of water objects didn’t exceed 1.5 µg/l. In anthropogenically polluted Baksan river the values increased to 5.7÷8.3 µg/l. The maximal concentrations were twice larger than the average ones. Some areas not related to mining, where water springs of underground alimentation contained high concentrations of Mo, were identified. They include the southern slope of Elbrus, the head of the Adylsu River, a vast zone (of over 50 km) beneath the Skalysty ridge and the right bank in the upper reaches of Cherek River. Their location indicates the relationship with the modern minerageny (Elbrus slopes), the ore oxidation and the dispersion of Mo from ancient ore belts. The variation in Mo concentration in the water bodies with its high natural content and in the group of anthropogenic polluted river water overlap partially.

In some cases, the average concentrations have similar values. The waterway migration of molybdenum from the tailings can be traced according to its concentrations in plants of sea buckthorn. These plants also had elevated levels of Mo in anthropogenic polluted town Tyrnyauz and natural polluted area in gorge Adylsu.

The more was contamination level, the more were differences between two plants willow and sea buckthorn.

Keywords: pollution, molybdenum, natural waters, bioindication, the Central Caucasus.

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