Oil pollution near the ports of Aktau, Kuryk and Ersai (the Caspian Sea): Satellite and in-situ data
2025-07-29 21:15
Oil pollution near the ports of Aktau, Kuryk and Ersai (the Caspian Sea): Satellite and in-situ data
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ANDREY G. KOSTIANOY1, 2, 3, NIKITA A. KNYAZEV4, OLGA YU. LAVROVA4, SYMBAT E. KOIBAKOVA5, * & SAMAL SYRLYBEKKYZY5
Abstract
To study oil pollution on the surface of the Caspian Sea in the area of the ports of Aktau, Kuryk and Ersai, the archives of radar data obtained from the synthetic aperture radars of the Sentinel-1 satellite constellation belonging to the European Space Agency for the period 2013 - 2022 were selected. For this purpose, a specialized satellite information service “See the Caspian Sea” (STCS) (http://caspian.geosmis.ru) created in 2023 jointly by Space Research Institute and Shirshov Institute of Oceanology of Russian Academy of Sciences was used. This system is specifically designed for the Caspian Sea and is created on the basis of the existing “See the Sea” (STS) service, which is part of the “IKI-Monitoring” Center for Collective Use established in Space Research Institute. For a given polygon in the region of the ports of Aktau, Kuryk and Ersai, in the STCS system, time series archives consisting of more than 3,700 radar images were examined. Each image was manually analyzed to identify dark areas of reduced radar signal that could be identified as oil contamination. A total of 15 oil slicks were discovered, up to 89 km in length and up to 8 km2 in area. A satellite image of each oil slick is presented in the article, as well as its main characteristics. In addition, as part of the project “Satellite monitoring of the water areas of the ports of Aktau and Kuryk”, sea water samples were taken in the area of the ports of Aktau and Kuryk, which showed the content of oil products in the range of 0.014-0.1 mg/dm3. Thus, the resulting concentrations turned out to be less than the maximum permissible concentration of 0.1 mg per liter.
The ports of Aktau and Kuryk (including Ersai Yard Harbor) are the most important sea gates of Kazakhstan in the Caspian Sea (Fig. 1), through which cargo is transshipped, including 15 million tons of oil per year. The development of ports leads to an increase in shipping, which increases the risk of oil pollution of the sea area and coastal zone, which occurs in all seas and oceans (Kostianoy, Lavrova, 2014; Zhiltsov et al., 2016; Carpenter, Kostianoy, 2018a,b; National Academies...., 2022). In addition, the drop in the level of the Caspian Sea (Ginzburg et al., 2021), which may continue in the next decades, may lead to disruption of their normal activities.
From April 2023 at the Shirshov Institute of Oceanology, Russian Academy of Sciences (Moscow), with the support of the Russian Science Foundation grant N 23-77-00027, the project “Study of the climatic variability of the thermohydrodynamic regime of the Caspian Sea according to remote sensing data” is being carried out (2023-2026). The main fundamental objectives of the project are:
(1) Analysis of climatic variability of the main physical parameters of the sea state (surface temperature, level, wind waves, sea ice, etc.) and meteorological parameters (air temperature, surface wind speed, integral water vapor content, water vapor content in clouds, precipitation) over the Caspian Sea;
(2) Application of the classical analysis of “extreme” (i.e., phenomena that stand out sharply against the background of the “norm”) to the study of the variability of the main parameters of the state of the Caspian Sea and the atmosphere. Analysis of extreme hydrological and meteorological events will be carried out using remote sensing and reanalysis data.
(3) Analysis of responses of the state of the sea surface to extreme meteorological phenomena observed over the sea and/or coast such as: upwelling variability; abnormal algae blooms or chlorophyll concentration in seawater; position and intensity of quasi-stationary vortices and vortex activity; ice conditions.
The implementation of this project should use large scientific infrastructure facilities located on the territory of the Russian Federation, including Centers for Collective Use of scientific equipment or unique scientific installations. Such an infrastructure object for the ongoing project is the “IKI- Monitoring” Center for Collective Use, an integral part of which is the information and analytical system
“See the Sea”(STS), created at the Space Research Institute of the Russian Academy of Sciences (Lavrova et al., 2019b). This system contains a large amount of remote sensing data of high and medium spatial resolution obtained from various sensors and satellites, as well as some meteorological information for the entire territory and water area of the Russian Federation.
One of the main objectives of the ongoing RSF project is the creation of a specialized information and analytical system “See the Caspian Sea” (STCS) based on the existing “See the Sea” system and functionality, designed for collecting, analyzing and visualizing satellite and meteorological data for the Caspian Sea region. The “See the Caspian Sea” information and analytical system will be supplemented with meteorological data collected from coastal weather stations of the Caspian Sea, data from NCEP and MERRA-2 atmospheric reanalyses, data from NCEP and WRF atmospheric forecasts, as well as the SWAN wave model with a spatial resolution of 5 km. As part of joint work with the “IKI-Monitoring” Center for Collective Use, existing algorithms will be adapted or new ones will be developed to calculate the physical parameters of the state of the sea and atmosphere based on remote sensing data. The STS system has long been successfully used to study oil pollution, in particular, in the Caspian Sea (Mityagina et al., 2019; Lavrova et al., 2019a, 2022; Mityagina, Kostianoy, 2024).
From mid 2023 the Project “Satellite monitoring of the water areas of the ports of Aktau and Kuryk“ funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant No. AP19175786) is implemented at Yessenov Caspian University of Technology and Engineering in Aktau, Kazakhstan. Its purpose is the implementation of a pilot project to organize and conduct satellite monitoring of the coastal waters around the ports of Aktau and Kuryk. Satellite monitoring will be aimed at studying oil pollution in the Caspian Sea between these ports, as well as sea level from satellite data and in-situ measurements. Collection and analysis of radar and optical images of high spatial resolution of the study area will be carried out from January 2015 to December 2025 from the Sentinel-1 and Sentinel-2 satellites. Collection and analysis of informative optical images of medium spatial resolution (250 m) from the MODIS-Terra satellite will be carried out daily. Satellite observations will be complemented by the collection and analysis of the necessary meteorological information and in-situ data. The expected results are to develop a methodology for satellite monitoring of the study area under conditions of limited in-situ observations and the development of
recommendations for the organization of permanent monitoring of the study area of the Caspian Sea. In addition, the ongoing shallowing of the Caspian Sea leads to the drying of the coastline and a decrease in depths in the area of the ports of Aktau, Kuryk and Ersai, which may lead to disruption of their normal operation.
We have to note that previous studies of oil pollution with the help of satellite data for different time periods have shown that a degree of oil pollution in area of the ports of Aktau, Kuryk and Ersai is minimal in comparison with the area around Oil Rocks in Azerbaijan where a huge number of offshore oil rigs is located (Bayramov, Buchroithner, 2014, 2016; Bayramov et al., 2018a,b; Holsten et al., 2018; Mityagina et al., 2019; Lavrova et al., 2022; Mityagina, Kostianoy, 2024).
In the present paper we combined our efforts performed in the above mentioned national projects in order to investigate oil pollution in the coastal zone of Kazakhstan between Fort-Shevchenko city on the north and Cape Zmeiny on the south with the help of the “See the Caspian Sea” satellite information and analytical system. Satellite information is complemented with in-situ data on oil pollution and other pollutants collected during field sampling near the shore in the vicinity of ports of Aktau, Kuryk and Ersai.
Data and Methods
Oil pollution monitoring was carried out using the “See the Caspian Sea” (STCS) satellite information service, developed in 2023 at the Space Research Institute of the Russian Academy of Sciences under the contract with Shirshov Institute of Oceanology of the Russian Academy of Sciences. The intended use of the system was to study time series of satellite radar data, as well as the results of their processing together with external parameters such as the wind field. To study oil pollution of the Caspian Sea surface in the STCS system, archives of radar data obtained from synthetic aperture radars of the Sentinel-1 satellite constellation belonging to the European Space Agency were selected. Table 1 presents the technical characteristics of the imaging equipment installed at the Sentinel-1A, -1B satellites. More than 3,700 Synthetic Aperture Radar (SAR) images were studied for a given polygon in the STCS system for the period 2013–2022. Each image was manually analyzed to identify dark areas of reduced radar signal that could be identified as oil contamination. Analysis of SAR imagery is a standard and effective tool for oil spill detection at the sea surface (Kostianoy, Lavrova, 2022). Since our research was focused on ship discharges, cases of natural pollution of sea waters caused by organic films of surfactants were discarded. In addition, the study did not take into account other manifestations (similarities) of pollution, which could be falsely interpreted as oil slicks (Mityagina et al., 2015).
Oil pollution caused by ship discharges is most often defined as elongated areas of reduced signal, spreading in the direction of the vessel's movement and in the direction of the wind field, which leads to an increase in the area of pollution (Lavrova et al., 2011, Lavrova et al., 2016, Mityagina et al., 2015). Most often, in SAR images, the polluting ship is observed, which appears in the form of a bright white dot of increased reflected signal. Such unambiguously interpreted cases of ship discharges were identified and stored in the STCS database under the class “Oil slick (ship discharge)” thanks to the developed tools for highlighting the boundaries of oil spill manifestations. To study the extent of pollution distribution, we used weather data integrated into the STCS system based on the NCEP Climate Forecast System Version 2 model (Lavrova et al., 2019b). Particular attention was paid to wind speed and direction, which made it possible to predict the direction, speed and area of pollution. This methodology was successfully used by Knyazev et al. (2021) for oil spill detection in the northeastern part of the Black Sea where the port of Novorossiysk with a number of oil terminals is located.
In-situ measurements of oil pollution and contamination of sea water by other chemical substances have been done during field expeditions along the coastal zone in the vicinity of the ports of Aktau, Kuryk and Ersai. Monitoring observations were carried out in accordance with generally accepted methods, taking into account the experience of conducting similar work in the coastal zone of the Caspian Sea. Water sampling was carried out in accordance with the Interstate Standard (GOST), which is a regional standard adopted by the Interstate Council for Standardization, Metrology and Certification of the Commonwealth of Independent States, GOST 17.1.5.05-85 “General requirements for sampling of surface and sea waters”. Seawater samples were taken using a standard bathometer into clean plastic containers and glass containers. When taking samples, water temperature was measured with thermometers with a division value of 0.50C.
Sea water samples were taken at the following points on 17 July and 13 September 2023 (Fig. 3):
1. Aktau port area (station K4, coordinates: 43o 37' 12"N, 51o 12' 28"E); 2. Kuryk port area (station K2, coordinates: 43o 09' 35"N, 51o 26' 14"E); 3. Ersai port area (station K3, coordinates: 43o 11' 12"N, 51o 32' 51"E).
In Kazakhstan there is no Maximum Permissible Concentration (MPC) for contaminants in sea water, but it is recommended to use the hygienic standards listed in the document “On approval of hygienic standards for safety indicators of household, drinking and cultural and domestic water use”, the Order of the Minister of Health of the Republic of Kazakhstan dated November 24, 2022, No. KR DSM-138, registered by the Ministry of Justice of the Republic of Kazakhstan on November 25, 2022, No. 30713. Laboratory tests of water samples have been done in a certified laboratory “Tandem Eco” (Aktau, Kazakhstan).
Results
Oil spills detected on SAR images in the study area for the period 2013–2022 are presented in Figure 4. They look like black strips of a different length because most of them are resulted from a release of oil products from moving vessels which appear as bright white dots on SAR images. To have a general view of oil spills detected in 2013-2022 in the region of ports of Aktau, Kuryk and Ersai, we drew all the oil spills on one summary map (Fig. 5) and collected the most important information about these oil spills in Table 2. The obtained results lead us to the following conclusions:
(1) Analysis of SAR Sentinel-1 imagery for ten years has revealed only 15 oil spills in the region of investigation. This is a very small number of oil spills in comparison, for example, with the Southeastern Baltic Sea (Kostianoy, Lavrova, 2014; Krek et al., 2018, 2021) or Mediterranean Sea (Carpenter, Kostianoy, 2018a,b) or the Black Sea (Lavrova et al., 2016) where ship traffic is much intense. A degree of oil pollution in this area is minimal in comparison with the area around Oil Rocks in Azerbaijan where a huge number of offshore oil rigs is located (Bayramov, Buchroithner, 2014, 2016; Bayramov et al., 2018a,b; Holsten et al., 2018; Mityagina et al., 2019; Lavrova et al., 2022; Mityagina, Kostianoy, 2024).
(2) Statistics of oil spill observations is too small to get conclusions concerning seasonal and interannual variability of oil spill occurrence. At least we don’t observe an increase in oil spills with time.
(3) Oil spill location and configuration shows that some of them (NN 1-5, 12, 13 in Fig. 5) are directly related with the port of Aktau, Kuryk and Ersai activities. The other ones seem to be related with the main ship routes in the surrounding area.
(4) The length of oil spills varies from about 3 to almost 90 km and their area from about 0.5 to 38 km2. This is consistent with oil spill statistics, for example, in the Southeastern Baltic Sea (Krek et al., 2018, 2021).
(5) Some of the observed oil spills were located at a distance of about 7-10 km from the coast which represents a danger to the coastal zone environment even if it is not densely populated.
(6) Wind speed at which oil spills are reliably detected on SAR imagery varies from 2-3 to 7-8 m/s, which corresponds well to wind force indicated in other publications (Lavrova et al.,
2011, 2016, 2022).
(7) Overall conclusion from the remote sensing study is that the ports of Aktau, Kuryk and Ersai operate cleanly, there is no oil pollution in their waters, and there is a low probability of oil pollution in the coastal zone, including the city of Aktau and its resort areas. However, satellite monitoring of oil pollution should be installed here, since there remains the possibility of oil pollution of the coastal zone from passing ships with an unfavorable combination of local currents and wind.
In-situ measurements of oil pollution in the vicinity of ports of Aktau, Kuryk and Ersai provides independent quantitative data on the level of the petroleum products concentration in the seawater. In Tables 3 and 4 we gathered the results of chemical analysis of seawater samples taken in the vicinity of these ports on 17 July and 13 September 2023. In the tables we included the values of Maximum Permissible Concentrations (MPC) for different chemicals, which we used to calculate a percent from MPC for every value.
The results of chemical analysis of water samples show that the content of phosphates (PO4), nitrites (NO2), nitrates (NO3), manganese (Mn), copper (Cu), chromium (Cr), nickel (Ni), Zink (Zn) and Lead (Pb) are significantly less than the MPC. The pH of sea water varied within 8.11–8.7, which is in the range of the norm 6-9. The average value of suspended solids in the summer period in the area of the port of Aktau was 25-31 mg/dm3, in the area of the port of Kuryk 16,1-16,5 mg/dm3, in the autumn period at the port of Aktau 7 mg/dm3, the port of Kuryk 6 mg/dm3, and the port of Ersai 5 mg/dm3. This is explained by the peculiarities of water circulation in the coastal zone, wind and waves effects in the nearshore zone. The studies note that the amount of the dissolved suspended solids in laboratory analyses is subject to well-known distorting effects, such as incomplete conversion of carbonate to oxide. This also includes partial oxidation of organic matter and incomplete elimination of the effect of magnesium chloride, calcium sulfate and magnesium, etc.
As concerns oil pollution, all samples showed values less than the MPC which is of 0.1 mg/dm3. These in-situ data confirm that seawater in the region of the ports of Aktau, Kuryk and Ersai is clean,
oil pollution is minimal and is in the limits of the MPC. This is consistent with the conclusions made from the analysis of satellite data on oil pollution.
For some chemicals in seawater, MPCs are not established, therefore the MPC value of hydrocarbonates and suspended solids is taken as the background value established by KazHydromet (Meteo service of Kazakhstan) for the study period. Chlorides and sulfates significantly exceed the MPCs at all sampling points of seawater, which is directly related to the salinity of seawater. For the most of chemical parameters, the observed values in the study area correspond to the average values characteristic for this area, and the results of observations and monitoring of the marine environment performed by KazHydromet.
Conclusions
The scientific novelty of this research lies in the implementation of a pilot project to organize and conduct satellite monitoring of the vast water area between the ports of Aktau and Kuryk, the largest sea gates of Kazakhstan in the Caspian Sea. The monitoring is focused on the study of oil pollution, as well as sea level from satellite data and in-situ measurements. Not only archival satellite images starting from 2015 will be collected and analyzed, but also current data during the project implementation. Such kind of satellite monitoring will be carried out for the first time in Kazakhstan. Similar work was carried out only in the Russian Federation, where permanent near-real time satellite monitoring of the D-6 offshore oil platform in the southeastern Baltic Sea for Lukoil company was organized in 2004 (Kostianoy et al., 2004, 2005, 2006). Until now, this is the only system in the Russian Federation that has been successfully operating so far and effectively detects oil pollution throughout the Southeastern Baltic Sea, including approaches to the ports of Kaliningrad (Russia), Klaipeda (Lithuania), Gdansk and Gdynia (Poland) (Krek et al., 2018; 2021). In the ongoing project, this unique experience and knowledge will be used to create the foundations of a similar near-real time system for the water area between the ports of Aktau and Kuryk. In the future, it can be extended to the entire water area of the Kazakhstani sector of the Caspian Sea, where large-scale activities are underway in the offshore oil and gas industry.
The socio-economic significance of the project lies in the fact that it will allow starting the training of Kazakhstan national personnel in the field of remote sensing of the seas from space, will further introduce new scientific and educational programs at the Yessenov Caspian University of Technology and Engineering (Aktau), to supplement the training program for students of the Maritime Academy with new disciplines. All this will provide scientific and technical potential and personnel for the creation of the Kazakhstan Scientific and Educational Marine Center on the basis of the Yessenov Caspian University of Technology and Engineering.
The project is directly aimed at solving urgent problems of socio-economic, scientific and technical development of the Republic of Kazakhstan, since it is associated with monitoring oil pollution in the waters of the ports of Aktau and Kuryk, which is extremely important for the ecology of the coast of the rapidly developing city of Aktau. Regional climate change leads to the ongoing shallowing of the Caspian Sea (Ginzburg et al., 2021), which may continue in the next decades, which may lead to disruption of the normal operation of the ports of Aktau, Kuryk, Ersai, the yacht port in Aktau, a radical change in the coastal strip, which is already taking place along the embankments of Aktau. Therefore, the results of the project will undoubtedly be important both for the administration of the city of Aktau and for the ports of Aktau, Kuryk and Ersai.
As for international activities, the results of the project will be a significant contribution of the Yessenov Caspian University of Technology and Engineering in the implementation of the project “The Caspian Sea Digital Twin”, which was supported by the Intergovernmental Oceanographic Commission of UNESCO in 2021 and included in the implementation plan of the UN Decade of Ocean Science for Sustainable Development (2021 -2030, https://en.unesco.org/ocean-decade) (Kostianoy, 2024).
Acknowledgements
In-situ measurements and analysis of water samples on oil pollution and other pollutants have been done by Symbat Koibakova and Samal Syrlybekkyzy in the framework of the Project “Satellite monitoring of the water areas of the ports of Aktau and Kuryk“ funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant No. AP19175786). Andrey Kostianoy and Olga Lavrova performed the analysis of satellite data on oil pollution with the support of the RSF Grant N 23-77-00027 «Investigation of the climate variability of thermo-hydrodynamic regime of the Caspian Sea based on remote sensing data», https://rscf.ru/en/project/23-77-00027/. Nikita Knyazev processed and analyzed radar images in the “See the Caspian Sea” system within the framework of the State assignment of the Space Research Institute of the Russian Academy of Sciences, topic “Monitoring”, State registration No. 122042500031-8.
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