This study was devoted to determining the concentration of hexavalent chromium (Cr 6+ ) in the Ishim River during the high water and low water season in the vicinity of the city of Petropavlovsk, Kazakhstan. During 2020, water samples were collected in May and September and examined for the presence of hexavalent chromium concentrations by atomic absorption spectrometry. The study showed that the average concentration of hexavalent chromium in the Ishim River in the vicinity of the city of Petropavlovsk in the high water season was 32 µg/l, while in the low water season the concentration of chromium was 36 µg/l. The average year concertation of chromium was 34 µg/l. Kazakhstan, 1425 km), the fall of the river from source to mouth is 513 m, the average slope is 21 cm/km (within the Republic of Kazakhstan, the fall is 475 m, with a slope of 33 cm/km). Ishim flows through the territory of Kazakhstan and Russia and is the main waterway, a centralized source of fresh drinking water for the North Kazakhstan region, in particular, the city of Petropavlovsk.
SamplingWater samples were taken in each May and September of 2020 from 9 AM to 12 PM. Water samples were taken around 150 meters from the enterprise-supplier of drinking water in Petropavlovsk from the Ishim River from a depth of 50-60 cm. Samples were taken in glass vessels with a volume of 1 liter, prematurely treated with distilled water. The selected water samples were placed in a portable refrigerating chamber, where the air temperature was maintained no higher than 4 °C. Then, within 4 hours, the samples were delivered to the National Center of Expertise in Petropavlovsk, Kazakhstan. Hexavalent chromium concentrations were studied using the SpectrAA 55 atomic absorption spectrometer (Agilent Technologies, USA).
Statistical analysisDescriptive statistics were used to determine the mean, minimum, and maximum values, as well as the standard deviation and 95% confidence interval. The calculations were performed in a software for statistical data processing IBM SPSS Statistics 26 (SPSS Inc., Chicago, Illinois, USA).
Results and discussionThe results of this study are shown in Figure 1 and Table 1. The current study showed that the concentrations of hexavalent chromium in the Ishim River near the water supply enterprise do not significantly vary when comparing the high water and low water seasons: the highest concentrations of chromium were in autumn (36 µg/l), while the lowest -in spring (32 µg/l). References 1. WHO, Guidelines for drinking water quality 4 th edition, 2017. https://www.who.int/publications/i/item/9789241549950 2. Bessonova V., Ivanchenko O. Chromium in the surrounding environment // Voprosy bioindicatsii i ekologii [issues of bioindication and ecology].