ECOGEOCHEMICAL CHARACTERISTICS OF THE YARLY-AMRY AND THE CHIBITKA RIVERS, LOCATED IN THE DISPERSION TRAIN OF AKTASH MERCURY DEPOSIT AND ITS WASTES (GORNY ALTAI)

Abstract

The relevance of the study is caused by the need to develop Russian guidelines for assessing the environmental state of bottom sediments and their impact on living organisms, as well as water bodies in general. The pollution of natural waters by potentially toxic elements is currently important. There are no federal standards regulating the quality of bottom sediments in Russia. Additionally, the study area is located in a popular tourist region of Gorny Altai. The knowledge about environmental state of the aquatic ecosystem in this region is of great importance. The main aim is to study the potentially toxic elements (Hg, As, Cu, Zn, Ni, Pb, Cd, Sb, Se) distribution in the waters and bottom sediments of the Yarly-Amry and the Chibitka Rivers and assess the environmental state of bottom sediments based on Russian and International guidelines as well as identify their toxicity to living organisms. Study area. The Chibitka River and its tributary, the Yarly-Amry River (Ulagan District, Aktash village) are located within the Kurai mercury zone and are additionally influenced by the Aktash Mining and Metallurgical Enterprise wastes stored on the Yarly-Amry River bank. Methods. pH and Eh were measured in waters by potentiometry. The dissolved Corg was determined by IR spectroscopy. The anions were studied by capillary electrophoresis. The potentially toxic elements contents in river waters were determined by flame and electrothermal atomic absorption spectrometry, as well as by mass spectrometry with inductively coupled plasma; Hg was determined by «cold vapor» atomic absorption spectrometry. The PTE contents in bottom sediments were determined by SR-XRF, flame and electrothermal atomic absorption spectrometry and «cold vapor» atomic absorption spectrometry. The geochemical features of bottom sediments were identified calculating their enrichment degree relative to the upper continental crust. The pollution degree of bottom sediments and the toxic impact probability on living organisms were estimated based on a comparison of potentially toxic elements content with Russian and International guidelines. Results. The increase of Cu, Cd, Hg and Se total contents in river water takes place due to the effect of Aktash Mining and Metallurgical Enterprise wastes on the Yarly-Amry River. The contents of Ni, Zn, As, Pb, Sb are higher in the source of Yarly-Amry River than in the part of the river affected by Aktash Mining and Metallurgical Enterprise wastes. The Chibitka River water above the mouth of the Yarly-Amry River (section 1) contains more Zn and Sb than section 2 (below the mouth), where the contents of Ni, Cu, As, Hg increase. The exceedances of the maximum permissible concentration for water bodies of fishery importance for Zn, Cu and Hg are 4,9; 1,7 and 46 times in the waters of both rivers. The bottom sediments of both rivers are significantly enriched by Hg, As, Ni, Sb, Se than the upper continental crust. The contents of Hg, As, Sb, Se in the sediments of the section 1 of the Chibitka River increase with distance from the river source. Hg and Sb sharp increase in in the sediments of the section 2 of the Chibitka River was found. Hg, As, Se and Sb pollution of bottom sediments of both rivers varies from moderate to very strong and even dangerous levels (according to the guidelines of permissible concentrations, contamination factor, degree of contamination and sediment quality index); Ni, Cu, Zn, Pb, Cd pollution is from low to moderate levels. Bottom sediments of the Yarly-Amry River and section 2 of the Chibitka River have the 50–100 % probability of the toxic effect on the microbiota (according to the ERL/ERM and TEL/PEL) due to the effect of Aktash Mining and Metallurgical Enterprise wastes and high contents of Hg, Ni, As, Cu. The probability of bottom sediments toxicity of both rivers is estimated at 5–30 % and it is due to the content of Zn, Pb and Cd. The mean effect range median (M-ERM-Q) shows the total toxicity of bottom sediments of the Chibitka and the Yarly-Amry Rivers, and varies from 21 to 76 % depending on the distance from Aktash Mining and Metallurgical Enterprise wastes. Bottom sediments of the Chibitka River near Aktash village is also highly toxic; the probability of toxicity decreases to moderate (21 %) only 9,2 km from the Yarly-Amry River mouth. The key factor of bottom sediments and river waters pollution is the Kurai mercury zone high natural geochemical background with accompanying ore mineralization and technogenic anomalies formed as a result of the Aktash Mining and Metallurgical Enterprise activity. The change in environmental state and quality of water bodies (mainly bottom sediments) is selectively determined by geochemical specifics of the area and depends on the content of Hg and, to a lesser extent, As, Cu, Ni, Se, Sb. The obtained results are important for assessing the environmental state of the Gorny Altai tourist region. Also, they make it possible to carry out a comparative analysis of environmental conditions with other world mercury zones in order to identify the features of pollution and migration of potentially toxic elements.

Keywords

• kurai mercury zone
• aktash mercury mine
• dispersion train
• river waters
• bottom sediments
• pollution
• mercury
• potentially toxic elements