The ecological and sanitary-hygienic assessment of the river systems located in the technogenic polluted zone of the Caucasus

The Caucasus is characterized by the large and at the same time increasing load from exploited metal and non-metallic mines. The sanitary-hygienic and toxic danger to people and the environment is quite high. There are 44 metal ores in the Syunik Region, and more than 90 non-metal deposits. In 2018, 12 metal and 29 non-metallic deposits were granted with the use rights for the purpose of mineral extraction. Also, geological survey permission was granted for 12 metal deposits. Currently, there are 12 operating and conserved tailings filled with about 400 million m3 of tailings, which are equipped with many heavy metals and other dangerous substances, as the result of the exploitation of the metal mines in Syunik. The present study focuses on the ecological assessment of the waters of the Voghji and the Khalaj Rivers that are located in the technogenic polluted zone of the Caucasus. The research revealed that along with the increase of the volumes of the Kapan-Qajaran copper-molybdenum mines, as well as the increase of the rock dumps and tailings, the organoleptic-chemical indicators of the waters of the Voghji and the Khalaj Rivers had increased. The quantity of the suspended particles and the heavy metals in the waters of these rivers had increased 1.5 and 2.0 times or by 58–100 % and 19.5 − 29.8 %, respectively, in the last 10 years. The trends are also observed in the values of the sulfates, the total dissolved salts, and the electrical conductivity, which are due to the chemical composition of the ores and the improper management of the acid drainage. The content of the heavy metals in the waters of the mentioned rivers is 9 − 20 times higher than the permissible limit density, and the degree of the mineralization is above the permissible limit. Thus, the waters of these rivers, after mixing with the effluent from the mining industry, are not guaranteed to be used for irrigation. Considering that the mobility of the heavy metals decreases several times in the alkaline environment (pH 8.5 − 9.0), it is recommended that the mining industry constantly adds lime (CaO) to the acid drainage of the mines so that the pH of the water become lower: from acid to alkaline (pH 8.5 − 9.0) and only after that, the water could be used for irrigation of the agricultural crops. This is possible for many types of heavy metals, including when using other wastewater treatment measures: engineering, physicochemical and biological.