# Transmission of Heavy Metals in River Water and Self-Purification Capacity of Ile River
## 3 Research and Results
The concentrations of other trace elements periodically exceed the MPC\({}_{\text{f}}\). Thus, in terms of heavy metal content, the river water does not meet sanitary standards for fisheries, which is due to the characteristic presence of heavy metals in the Ile River as a result of discharges from industrial and agricultural production, as well as from municipal and domestic wastewater. Generally, the self-purification of water bodies from sewage liquid  
Figure 7: Changes in heavy metal concentrations under the influence of the Kapshagai reservoir. occurs only due to dilution with natural water, as well as by the processes of substance transformation (chemical, biological, physicochemical, physical, etc.) running in rivers. The calculation of the self-purification capacity (SPC) of the Ile River was made at the sites before the Kapshagai reservoir, after the reservoir, taking into account the influence of the Kapshagai reservoir and in the Kazakhstan part of the Ile River. In many cases, the concentration of pollutants in the downstream section exceeded the initial one. That was why the indicators of SPC of these areas were obtained with negative signs, which meant a lack of self-purification ability. The self-purification process was calculated for six heavy metals (Table 4). The obtained values of SPC with a negative sign were associated with anthropogenic impact, with sewage or collector water inflow occurring at these areas. The self-purification of water masses upward to the Kapshagai reservoir occurs to a greater extent from copper (77-99%) in the summer and winter periods. During the spring period, the process of self-purification from copper does not occur, probably caused by the arrival of pollutants from adjacent lands with melt water and humic layer erosion influences. The self-purification of water from cadmium during the year is 14-49%, only during spring, and for copper, it does not occur. The self-purification of zinc during the year is low, from 7 to 26%. The lowest self-purification of water masses occurs for cobalt and nickel, 6-9%, probably because of the higher total concentrations. The self-purification of river water from heavy metals after the Kapshagai reservoir to the delta top occurred in separate seasons in different ways during the observed period. For example, self-purification of water from cadmium in spring reached 90%, and in the rest of the year, the SPC had negative indicators. The self-purification process from cobalt  
Figure 8: Seasonal heavy metal concentrations in Ile River water downstream of the Kapshagai reservoir based on monthly measurements. was 54% and from copper, 32%, during summer, while from nickel, it was 46% in winter, and from zinc, it was 33% in autumn. To identify the effect of reservoir activity on water self-purification capacity, SPC calculations were performed between Dobyn and 37 km downstream from the HPP. Compared to previous calculations, the self-purification of water masses in this section was much more intensive. During the period under review, the SPC from cadmium was 28-81%, that of copper was 15-66%, and that of zinc was 22-37%. The self-purification of cobalt was low, at 5-9%, while the nickel self-purification of water did not occur. In general, from the Chinese border to the closing gauging station, the self-purification of water masses for cadmium and zinc was satisfactory at up to 93%. A low self-purification capacity in this section was manifested for copper (up to 33%), and zinc (29%) except during the autumn period, when it amounted to 2-11%, with a negative sign. During the winter period, the self-purification from nickel amounted to 27% while the other seasons had a negative sign, apparently, due to the fact that in addition to the river water transport from the upper station, there was an additional inflow of pollutants from China, which indicates water pollution rather than the self-purification of water.