Сезонная динамика содержания тяжелых металлов и оценка загрязнения воды в реке Северная Двина (Архангельск)

Abstract

The article presents the research results on the identification of seasonal variability in the values of physicochemical parameters and the metal content in the water of the Northern Dvina River. Sampling was carried out daily from January 23, 2020 to January 23, 2021 at low tide. In general, the researchers have revealed that the values of the studied parameters largely depend on the volume of seasonal river water runoff, on the underlying rocks of the river water basin, and also on anthropogenic influence. Thus, the values of pH, mineralization and a number of metals (Mg, Sr and Ba) are minimal during the flood period, which is explained by the large amount of melt water. Increased concentrations during the flood period are observed for Al, Mn, Cr, Zn, V, and Pb, which is associated with the dissolution of the underlying rocks and the runoff of winter precipitation in the form of melted snow. The researchers have determined elevated average content of natural elements Fe, Sr and Al, as well as anthropogenic metals Ni, Zn and Cr in the Northern Dvina relative to the average world concentration values. The calculation of water quality indices (HMEI, HMPL and HMTL) and public health risk indices (HI and CR) has revealed that the water in the Northern Dvina River has different levels of pollution, from mild to severe. However, the scientists have proved that permanent consumption of water as a drink can cause carcinogenic and non-carcinogenic effects. The main metals that contribute most to the index values are Fe, Ni, Al, Cr, Mn, Ba, and As. The study of the uranium content and its isotopes has revealed a large number of extremes, which does not allow drawing a conclusion about its seasonal dynamics, but the average value of the uranium content is similar to the global value for rivers.