Evaluation of Water Contamination in the East Kazakhstan Mining Area Using Multivariate Geostatistics

The East Kazakhstan region is one of the most industrialised regions in the country producing considerable amounts of mineable copper, zinc, and gold due to mining activities. Development of metallurgical and mining industries has been increasing the pollution of surface waters by toxic chemical elements, particularly Cu, Mn, and Zn. We assessed the extent of these metal contaminations in surface waters in this region, by multivariate geostatistical analyses of the concentrations of the above-mentioned heavy metals over the five year periods (2017-2022). The dataset consists of element concentrations and sampling locations, for which it was provided by the Republican State Enterprise “Kazhydromet”. Principal Component Analysis (PCA) coupled with Simple Cokriging have been incorporated to characterise the local distribution of the heavy metals in surface waters in the East Kazakhstan region. The first component of PCA is used for further analysis since it qualifies for 74% of the total variation in the data. Then, a Simple Cokriging over the four continuous variables (PC1, Cu, Mn, and Zn) has been carried out to map their spatial distribution. Furthermore, the estimation map of PC1 is categorised, linking it to Cu, Mn, and Zn estimated maps; where the high, medium and low concentration areas of above-mentioned heavy metals are recognised over the entire region. The results are then interpreted by superimposing the river network into the estimation maps of elements.  

According to estimation maps, variations in concentrations of Cu, Mn, and Zn depend on the season and resulted in a distinct pattern. The surface waters in the region are mostly contaminated in spring and winter seasons due to snowfall and subsequent melting, whereas they are least contaminated during the summer and autumn. Moreover, it was observed that Cu shows the most mobility among the three toxic elements. A significant amount of Cu is discharged to the surface waters in Spring periodically, when snow melting activities are enhanced in Ust’-Kamenogorsk city, and transported to downstream regions. Therefore, higher concentrations of Cu near Semey city are observed during summer. The same effect has not been observed for Mn and Zn elements, which indicates that their overall mobility is lower.

Generally, observed Cu and Mn concentrations are exceeding the Maximum Allowable Concentration (MAC) by 5 times in the vicinity of Ust-Kamenogorsk and Ridder cities, while Zn exceeded its MAC by 10 times in the same region. One possible source of such high concentrations of heavy metals in this region is linked to the mining operations, especially to the Tailings Storage Facilities (TSF) that have been driving surface water contamination since the 1960s. After every relevant TSF has been superimposed on the estimated maps, the relationship between high metal concentration and TSF was investigated, leading to a conclusion that both active and closed Tailings Storage Facilities are the primary sources of surface water contamination in the study region. This shows that the situation of the study region in terms of surface water pollution is deplorable and needs urgent remediation actions.

Keywords: Multivariate Geostatistics, Water Contamination, Tailings Storage Facilities.