# Transmission of Heavy Metals in River Water and Self-Purification Capacity of Ile River
## 4 Discussion  
One of the most pressing issues in the studied basin is the degradation of natural water quality and the state of the aquatic ecosystem due to human activities and the transboundary nature of the river. Previous studies [40, 41] had revealed exceedances of permissible concentrations of heavy metals in the transboundary flow of the Ile River, \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Period** & **Initial** & **Final** & **Cu** & **Zn** & **Pb** & **Cd** & **Co** & **Ni** \\ \hline \hline \multicolumn{10}{c}{In the territory of the Republic of Kazakhstan} \\ \hline Winter & & & 20 & 12 & \(-\)420 & 43 & 7 & 27 \\ \hline Spring & & & 15 & 23 & 46 & 93 & 25 & \(-\)20 \\ \hline Summer & & & 33 & 29 & 28 & 38 & 5 & \(-\)10 \\ \hline Autumn & & & \(-\)2 & 1 & 24 & 3 & \(-\)11 & \(-\)57 \\ \hline \multicolumn{10}{c}{Before the Kapshagai reservoir} \\ \hline Winter & & & 99 & 7 & \(-\)890 & 49 & \(-\)7 & 9 \\ \hline Spring & & & \(-\)27 & 26 & 46 & 14 & \(-\)15 & \(-\)46 \\ \hline Summer & & & 77 & 13 & \(-\)5 & 41 & \(-\)4 & \(-\)3 \\ \hline Autumn & & & 5 & 20 & 16 & \(-\)3 & 6 & \(-\)133 \\ \hline \multicolumn{10}{c}{Taking into account the influence of the Kapshagai reservoir} \\ \hline Winter & Dobyn & 37 km below HPP & 40 & 23 & \(-\)730 & 49 & 9 & \(-\)36 \\ \hline Spring & & & 15 & 37 & 60 & 28 & 5 & \(-\)46 \\ \hline Summer & & & 66 & 22 & 0 & 81 & \(-\)9 & \(-\)18 \\ \hline Autumn & & & 66 & 22 & 0 & 81 & \(-\)9 & \(-\)18 \\ \hline \multicolumn{10}{c}{After the Kapshagai reservoir} \\ \hline Winter & & & \(-\)33 & \(-\)15 & 37 & \(-\)11 & \(-\)2 & 46 \\ \hline Spring & 37 km below HPP & Kokzhide & & 0 & \(-\)21 & \(-\)35 & 90 & 21 & 18 \\ \hline Summer & & & 33 & 0 & 5 & \(-\)13 & 54 & 20 \\ \hline Autumn & & & \(-\)13 & 32 & 24 & \(-\)11 & \(-\)13 & \(-\)57 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Degrees of self-purification capacity (SPC) of the Ile River water at selected river sections. which were confirmed by the results of the present research conducted between October 2023 and September 2024. This situation has persisted for several years, with a growing trend in the concentrations of certain pollutants in recent years. Among pollutants, heavy metals pose a significant danger to aquatic biota, as unlike organic pollutants, metals do not undergo degradation but can only be redistributed among the ecosystem components. Therefore, analyses of heavy metal pollution in water bodies are very important nowadays since they are the main sources of anthropogenic pollution of aquatic ecosystems. In Kazakhstan, as well as in other countries, the main pollutants of water bodies are heavy metals because of their high stability and cumulative effect. These substances, being accumulated along trophic chains to concentrations hundreds and thousands of times higher than their contents in water, are capable of causing deep disturbances of physiological and biochemical processes in aquatic organisms [42]. The content of trace elements in water is one of the important indicators determining the ecological states of water bodies. These play a major role in the development of living organisms, regulating many biochemical processes. However, their excess in a water body, created under the influence of various anthropogenic factors, leads to the disruption of the normal functioning of aquatic ecosystems. Heavy metals are able to accumulate in various objects of the aquatic environment, including fish, without undergoing chemical and biological degradation [42; 43; 44]. The main causes of such anthropogenic pollution of water basins are wastewater and air emissions from large industries and the transboundary transfer of toxicants along large rivers. The Ile River also accepts these influences. It is affected by transboundary pollution and tributaries that flow through small towns and large population centers [43; 44].