Ecological condition of marine waters in the area of dredging operations of the kashagan field, Kazakhstan

To determine the hydrophysical and hydrochemical parameters of sea water and their changes during dredging works in the north‐eastern part of the Caspian Sea along the Western Approach Route and near/inside block D, islands EPC‐2, EPC‐3, EPC‐4 and island A of the Kashagan field.

Measurement of hydrophysical parameters: salinity, temperature, turbidity, dissolved oxygen concentration, electrical conductivity, pH of seawater was carried out using a portable multi‐parameter analyser "Horiba‐U53" directly in the water column. Water transparency was determined using a Secchi disc. The depth of the water layer was determined using a sounder. Hydrochemical investigations were carried out for seven parameters, with all components sampled in the near‐surface and benthic horizons. Water samples were taken using probes or bathometers: BM‐48, GR‐18 or their analogues.

Hydrochemical analyses of seawater samples for: biogens (NO2, NO3, NH4, Ntotal, and Ptotal), synthetic surfactants, phenols, hydrocarbons including polyaromatic hydrocarbons (PAHS), heavy metals, chemical oxygen demand (COD) and biochemical oxygen demand (BOD5). These were carried out in laboratory conditions using analytical equipment according to scientifically accepted methods.

The data obtained as a result of the research allow us to draw the following conclusion: changes in the amount of suspended sediment in sea water lead to changes in physical and chemical properties of water (increase in turbidity, disturbance of sediment composition and properties), changes in biotopes, deterioration of oxygen regime, optical properties of water and temperature regime.

1. Huseynova S.A., Abdusamadov A.S. Forecast of the CaspianS ea level dynamics and its consequences for coastal territories. South of Russia: ecology, development, 2015, vol. 10, no. 4, pp. 119–126. https://doi.org/10.18470/1992‐1098‐2015‐4‐119‐126 (In Russian)

2. Nesterov E.S. Vodnyi balans i kolebaniya urovnya Kaspiiskogo morya. Modelirovanie i prognozirovanie. [Water balance and Caspian Sea level fluctuations. Modelling and Forecasting]. Moscow, Triad Publ., 2016, 378 р. (In Russian)

3. Tabelinkova A.C. [Caspian Sea level fluctuation: causes, consequences and research methods]. Evraziiskii Soyuz Uchenykh (ESU). 2019, no. 4(61), pр. 34–40. (In Russian) Available at: https://cyberleninka.ru/article/n/kolebanieurovnya-kaspiyskogo-morya-prichiny-posledstviya-imetody-issledovaniya/viewer

4. Kenzhegaliev A., Kanbetov A., Kulbatyrov D., Shakhmanova A., Abilgaziyeva A. Fluctuation in the level of the Caspian sea and its consequences. E3S Web of Conferences, International Symposium on Sustainable Energy and Power Engineering, (SUSE‐2021), 2021, vol. 288, article id: 01063. https://doi.org/10.1051/e3sconf/202128801064

5. Abuzyarov Z.K., Nesterov E.S. Some features of spatial and temporal variability of the Caspian Sea level. In: Trudy Gidromettsentra Rossii [Proceedings of the Hydrometeorological Centre of Russia]. 2011, iss. 345, рр. 5–23.

6. Ecological code of the Republic of Kazakhstan dated January 2, 2021 No.400‐VI LRK. https://adilet.zan.kz/eng/docs/K2100000400 (accessed 23.09.2023)

7. ISO 5667–1:2006 Water quality – Sampling –Guidance on the design of sampling programmes and sampling techniques. P. 1. (In Russian) Available at: https://www.iso.org/obp/ui/#iso:std:iso:5667:-1:ed2:v1:ru (accessed 23.09.2023)

8. ISO 5667–9:2013 Water quality. Sampling. Guidance on sampling from marine waters, IDT. P. 9. (In Russian) Available at: https://online.zakon.kz/Document/?doc_id=35831830 (accessed 25.09.2023)

9. GOST 17.1.5.04–81 Nature protection. Hydrosphere. Apparatus and mechanisms for selektion, initial treatment and stering samples of natural waters. (In Russian) Available at: https://files.stroyinf.ru/Data2/1/4294835/4294835624.pdf (accessed 07.10.2023)

10. ISO 5667–3:2012 Water quality. Sampling. Preservation and handling of water samples, IDT. P. 3 (In Russian) Available at: https://online.zakon.kz/Document/?doc_id=31724434 (accessed 10.10.2023)

11. Fonovye ekologicheskie issledovaniya po proektu «Dnouglublenie potentsial'nogo sudokhodnogo puti dlya dvizheniya sudov ot Ural'skoi borozdy do ostrova D i vokrug sushchestvuyushchikh ostrovov na mestorozhdenii Kashagan», 2020–2021 [NCOC Seasonal reports Background environmental studies for the project «Dredging of a potential navigation route for vessel traffic from the Ural furrow to D‐island and around existing islands in the Kashagan field», 2020–2021]. (In Russian) Available at: https://www.ncoc.kz (accessed 15.10.2023)

12. Sezonnye otchety «Monitoring vozdeistviya na morskuyu sredu v kazakhstanskom sektore Kaspiiskogo morya» (vesna, leto, osen'), 2020–2021 [Seasonal reports «Marine Impact Monitoring in the Kazakhstan Sector of the Caspian Sea» (spring, summer, autumn), 2020–2021]. (In Russian) Available at: https://www.ncoc.kz (In Russian) (accessed 15.10.2023)

13. Informatsionnyi byulleten' o sostoyanii okruzhayushchei sredy kazakhstanskoi chasti Kaspiiskogo morya na 2021– 2022 (Ministerstvo ekologii, geologii i prirodnykh resursov Respubliki Kazakhstan, respublikanskoe gosudarstvennoe predpriyatie «Kazgidromet», Departament ekologicheskogo monitoringa) [Information bulletin on the state of the environment of the Kazakhstan part of the Caspian Sea for 2021–2022 (of the Ministry of Ecology, Geology and Natural Resources of the Republic of Kazakhstan, republican state enterprise «Kazhydromet», Department of Environmental Monitoring)]. (In Russian) Available at: https://www.ncoc.kz (accessed 15.10.2023)