The patterns of heavy metals accumulation in water, soil and their transfer in the soil–plant system in the catchment area of the Sotk and Masrik rivers

The problem of pollution of the catchment area of the Masrik river, located in the basin of lake Sevan, is associated with the gold mining plant in the basin of its Sotk tributary, where ore is mined and crushed. Industrial activity changes the natural background of the formation of the quality of various media within the river basin in terms of the heavy me-tals content in them. Geo-ecological studies in areas of mining activity are relevant from the point of view of assessing the level of pollution and environmental quality control. The object is the drainage basin of the Masrik river with the Sotk tributary that flows near the territory of the gold ore plant. The subject of research is heavy metals in various environments ‒ in water, soil, plants, their behaviour, accumulation and transfer. The contents of Cu, Zn, Pb, Cr, Co, Cd and Ni were determined in water samples, floodplain soils and plants collected in the basins of the Sotk and Masrik rivers. The regularity of the prevalence of summer concentrations of copper over spring was established. It is associated with the difference in water flow in the river, when summer low water is characterized by a sharp decrease in the water content of the rivers. Lead is characterized by the predominance of spring concentrations in the upper reaches of the Sotk river and summer concentrations in the lower reaches of the Masrik River basin. This trend can be due to the washout of storm drains in spring in the Sotk River basin, which is characterized by steep banks and accumulation in the summer period in the flat part of the Masrik river. In general, for both seasons, zinc and nickel differ in relatively high concentrations. According to studies, the values of the distribution coefficient of heavy metals in soils showed a dependence on pH level. The distribution coefficients increased with decreasing acidity values. Pb was among the highest coefficients studied, and the minimum values were typical for Cu. The obtained values of the distribution coefficient indicate that copper has a high solubility and, under favourable conditions, passes into the soil solution. High lead coefficients indicate its low solubility and high adsorption in the soil. The results of the trends analysis and revealed patterns confirmed the presence of a high level of copper solubility in the soil, as well as the significant bioavailability of this metal to plants. For lead, trends of low solubility in soil have been found, but on the issue of bioavailability to plants, it exhibits ambiguous behaviour. Nickel, in terms of accumulation of soil–plant migration in the soil, shows the lowest chemical activity