Speaker
Description
The Kapshagai Reservoir is located in the Almaty Region, near the city of Konaev and the megapolis of Almaty, within an actively developing industrial and agricultural zone. Specifically, it serves multiple purposes including irrigation, hydroelectric power, recreation and flood control. The study of water quality is essential for ensuring the environmental safety of the region and the well-being of the population of the Republic of Kazakhstan (RK). Water from the reservoir is supplied to irrigation canals and several small rivers, which support the cultivation of grain, melons, vegetables, and fruits, with cotton growing and horticulture also being well developed in the region. The research of pollution by heavy metals and toxic elements in such water bodies is highly relevant for assessing anthropogenic impacts on the environment [1]. From this perspective, bottom sediments also serve as an important indicator of the ecological state of a water basin, as they accumulate heavy metals and toxic elements precipitated from water [2-3].
The sampling methodology and analytical methods used in this study were developed within the framework of the ISTC regional project “Navruz” [4] and have been continuously improved [5]. Environmental sampling for the assessment of the Kapshagai Reservoir was conducted at 13 sample points (SPs) in the channels of small foothill rivers flowing into the reservoir, as well as at 4 SPs along its shoreline. Elemental composition analysis of the samples was carried out at the Center for Integrated Environmental Research (CIER) using certified methodologies and calibrated equipment. CIER is accredited in accordance with the international standard ISO/IEC 17025:2019 “General requirements for the competence of testing and calibration laboratories”. The analytical methods include inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectrometry (ICP-AES), energy-dispersive X-ray fluorescence analysis (XRF), and neutron activation analysis (NAA). Quality control was performed using IAEA standards. The analysis of the obtained results was performed using statistical methods and in accordance with the regulatory documents of the Republic of Kazakhstan (RK) and the World Health Organization (WHO). During the water composition analysis, Rh (5 µg/L) was added to all samples and calibration solutions as an internal standard for correcting instrumental deviations and matrix effects in ICP-MS, and Sc (0.25 mg/L) was used for the same purpose in ICP-AES.
The elemental composition of bottom sediment samples was investigated using XRF and NAA. The XRF method was applied using an energy-dispersive X-ray fluorescence spectrometer manufactured by the Kazakhstan company LLP “AspapGeo”, specifically designed for the analysis of geological samples, soils, and bottom sediments. Spectral processing was performed automatically using the built-in software. Detection limits for the contents of Fe, Mn, and V were from 0.01%; for Cu, Ni, Pb, Sr, and Zn from 0.001%; and for Mo from 2 µg/g. The NAA method is based on measuring gamma radiation emitted by radionuclides produced through nuclear reactions during the activation of the sample by a neutron flux. Irradiation of 100 mg sample aliquots was carried out at the WWR-K research nuclear reactor (Institute of Nuclear Physics, Almaty, RK) using a thermal neutron flux of 6.6 × 10¹³ neutrons cm⁻² s⁻¹ for a duration of 90 minutes. The induced activity spectra of the samples were recorded 7 and 21 days after irradiation using a Canberra gamma spectrometer equipped with a high-purity germanium semiconductor detector. Spectral processing was performed using the Genie-2000 software. Quantification of element concentrations was conducted using the relative method with standards of IAEA Soil-7, SL-1, SL-3, GSO 8670-2005, Oreas 506, Oreas 600b and Oreas 100a.
The research results revealed the concentrations of elements as follows: As up to 8.0 µg/l in water and 9.4 mg/kg in bottom sediments; Cu up to 5.4 µg/l in water and 20 mg/kg in bottom sediments; Ni at 17 µg/l in water and 40 mg/kg in bottom sediments; Pb up to 1.7 µg/l in water and 28 mg/kg in bottom sediments; Th up to 16.5 mg/kg in bottom sediments; U up to 34 µg/l in water and 19 mg/kg in bottom sediments; Ba up to 87 µg/l in water and 920 mg/kg in bottom sediments; Cr up to 7.1 µg/l in water and 93 mg/kg in bottom sediments; Mn up to 20 µg/l in water and 1000 mg/kg in bottom sediments; Sb up to 1.8 µg/l in water and 1.0 mg/kg in bottom sediments; Fe up to 168 µg/l in water and 3000 mg/kg in bottom sediments; Sr up to 3320 µg/l in water and 2501 mg/kg in bottom sediments; Zn up to 15 µg/l in water and 71 mg/kg in bottom sediments; Co up to 0.5 µg/l in water and 9.8 mg/kg in bottom sediments; Mo up to 46 µg/l in water and 8.2 mg/kg in bottom sediments; and V up to 6.0 µg/l in water and 110 mg/kg in bottom sediments.
The analysis of the samples showed that the concentrations of the studied elements in the water generally did not exceed the maximum permissible limits established by RK and WHO. An exception was recorded at monitoring point 10, located on the Lep River (Karasu), where the uranium concentration in the water sample exceeded the WHO guideline value by 15%. In bottom sediments, exceedances of Clarke values [6] for elements such as As, Pb, U, Sr, Sb, Ba, Th, and Mo were observed at certain monitoring points. These anomalies may be attributed to the natural geochemical characteristics of the region rather than to anthropogenic impact on the ecosystem. This research requires further investigation.
Acknowledgment: this research was funded by the Ministry of Energy of the Republic of Kazakhstan, IRN: BR23891691.
The main ideologist and leader of this research was the late Doctor of Physical and Mathematical Sciences and Environmental Sciences Vladimir Solodukhin, whose inspiring ideas formed the foundation of this study and served as an important guide for its successful completion.
References
1. Assessment of the Water Quality of the Khodtsa River near Elektrostal during the Spring Flood Period. In Ecology of River Basins: Proc. 9th Int. Sci.-Pract. Conf. (Suzdal, September 5–8, 2018); 68–74 (2018).
2. Bai, J.et al., Spatial Distribution and Ecological Risk Assessment of Heavy Metals in Surface Sediments from a Typical Plateau Lake Wetland, China. Ecol. Modell. 222 (2), 301–306 (2010)
3. Ryzhakov, A. N.and Martynov, D. V. Assessment of the Degree of Pollution of Bottom Sediments in Small Rivers of Rostov Region. Ecol. Water Manag., 2, 29–39 (2021)
4. Barber D.S., etc…and Solodukhin V. The Navruz experiment: Cooperative monitoring for radionuclides and metals in Central Asia transboundary rivers. Journal of Radioanalytical and Nuclear chemistry. 263, № 1, 213-218 (2005).
5. Solodukhin V. P., etc, Zheltov D. A. Radionuclide and toxic chemical elements in the transboundary «Kyrgyzstan - Kazakhstan» rivers. J. Radioanal. Nucl. Chem., 309, 115-124 (2016)
6. Taylor, S. R. Abundance of Chemical Elements in the Continental Crust: A New Table. Geochim. Cosmochim. Acta, 28 (8), 1273–1285 (1964).