Microplastics in the Lower Volga–Northern Caspian System: Spatial Distribution in the Water Mixing Zone and Sources of Input

M. A. Antsiferova*, A. V. Kleshchenkov, A. M. Korshun

Federal State Budgetary Institution of Science "Federal Research Center Southern Scientific Center of the Russian Academy of Sciences", Rostov-on-Don, Russia

* e-mail: m12antsiferova@mail.ru

Abstract

The influence of hydrological and hydrochemical conditions on the spatial distribution of microplastics in estuarine zones has been poorly studied. The study aims to assess microplastics spatial distribution and their quantitative and qualitative characteristics in the Lower Volga–Northern Caspian system. The data were collected during an expedition on R/V Deneb in September 2023. The samples were taken using a neuston trawl net (0.3 mm mesh) in the surface layer (0–0.2 m), followed by processing according to a modified NOAA method and direct visual sorting under a microscope. The polymers were identified using the Raman and Fourier-transform infrared spectroscopy, with the PHI hazard index calculated. In parallel, hydrochemical, hydrological and meteorological parameters of the environment were measured, including ion composition. In the Lower Volga, the average particle concentration was 81 particles/m³, with peak values of 100 particles/m³ (following a downpour in Kalmykia), as well as 92 particles/m³ near Volgograd and 98 particles/m³ near Astrakhan, indicating anthropogenic runoff as the primary source. In the Northern Caspian Sea, particle concentrations were significantly lower (ranging from 3 to 44 particles/m³, with an average of 13 particles/m³), showing a pronounced downward gradient from the estuary. Fine microplastics (0.3–2 mm) in the form of fibres and fragments predominated, mainly consisting of polyethylene, polyethylene terephthalate and polyamide, which are classified as hazard class 2 according to the PHI index. The spatial distribution of particles correlates with variations in salinity and ionic composition (a 20- and 80-fold decrease in the Ca²⁺/Cl⁻ and HCO₃⁻/Cl⁻ ratios), turbulent mixing following a storm and shower precipitation. In the estuary zone, the dilution of river water with seawater leads to a significant reduction in particle count: from 98 particles/m³ to 44 particles/m³, and subsequently to 13 particles/m³. The primary source of microplastics is anthropogenic runoff from the Volga, including diffuse runoff from urbanised areas. The specific nature of the Caspian Sea as a closed basin with a strong river inflow results in relatively higher microplastics concentrations than those found in open seas. The obtained data justify the need to control surface runoff and monitor estuarine geochemical barriers.

Keywords

microplastics, Northern Caspian Sea, Lower Volga, mixing zone, ionic composition, anthropogenic pollution

Acknowledgments

The article was prepared under state assignment of SSC RAS no. 125012100503-4. The work was performed using equipment of the Shared Research Facility of SSC RAS, no. 501994.

About the authors

Marina A. Antsiferova, Junior Researcher, Federal Research Centre the Southern Scientific Centre of RAS (41 Chekhov Ave., Rostov-on-Don, 344006, Russia), PhD (Geogr.), ORCID ID: 0009-0006-6549-8606, m12antsiferova@mail.ru

Aleksei V. Kleshchenkov, Leading Researcher, Federal Research Centre the Southern Scientific Centre of RAS (41 Chekhov Ave., Rostov-on-Don, 344006, Russia), PhD (Geogr.), ORCID ID: 0000-0002-7976-6951, Scopus Author ID: 570697100, ResearcherID: E-6619-2014, kle-aleksej@yandex.ru

Anna M. Korshun, Researcher, Federal Research Centre the Southern Scientific Centre of RAS (41 Chekhov Ave., Rostov-on-Don, 344006, Russia), PhD (Geogr.), a_korshyn@mail.ru

For citation

Antsiferova, M.A., Kleshchenkov, A.V. and Korshun, A.M., 2026. Microplastics in the Lower Volga–Northern Caspian System: Spatial Distribution in the Water Mixing Zone and Sources of Input. Ecological Safety of Coastal and Shelf Zones of Sea, (2), pp. 93–109.

References

  1. Rochman, C.M., Brookson, C., Bikker, J., Djuric, N., Earn, A., Bucci, K., Athey, S., Huntington, A., McIlwraith, H. et al., 2019. Rethinking Microplastics as a Diverse Contaminant Suite. Environmental Toxicology and Chemistry, 38(4), pp. 703–711. https://doi.org/10.1002/etc.4371
  2. Chubarenko, I.P., Esyukova, E.E., Khatmullina, L.I., Lobchuk, O.I., Isachenko, I.A. and Bukanova, T.V., 2021. [Microplastics in the Marine Environment]. Moscow: Nauchny Mir, 520 p. (in Russian).
  3. Frank, Yu.A., Vorobiev, E.D., Rakhmatullina, S.N., Trifonov, A.A. and Vorobiev D.S., 2022. Screening of Мicroplastic Сontent in Surface Waters of Russian Rivers. Ecology and Industry of Russia, 26(9), pp. 67–71. https://doi.org/10.18412/1816-0395-2022-9-67-71 (in Russian).
  4. Frank, Y.A., Vorobiev, E.D., Vorobiev, D.S., Trifonov, A.A., Antsiferov, D.V., Soliman Hunter, T., Wilson, S.P. and Strezov, V., 2021. Preliminary Screening for Microplastic Concentrations in the Surface Water of the Ob and Tom Rivers in Siberia, Russia. Sustainability, 13(1), 80. https://doi.org/10.3390/su13010080
  5. Gao, S., Orlowsky, N., Bopf, F.K. and Breuer, L., 2024. Review on Microplastics in Large European Rivers. WIREs Water, 11(3), e1713. https://doi.org/10.1002/wat2.1713
  6. Mikhailov, V.N., 1997. [River Mouths in Russia and Neighbouring Countries: Past, Present and Future]. Moscow: GEOS, 413 p. (in Russian).
  7. Nematollahi, M.J., Moore, F., Keshavarzi, B., Vogt, R.D., Saravi, H.N. and Busquets, R., 2020. Microplastic Particles in Sediments and Waters, South of Caspian Sea: Frequency, Distribution, Characteristics, and Chemical Composition. Ecotoxicology and Environmental Safety, 206, 111137, https://doi.org/10.1016/j.ecoenv.2020.111137
  8. Manbohi, A., Mehdinia, A., Rahnama, R., Hamzehpour, A. and Dehbandi, R., 2023. Distribution of Microplastics in Upstream and Downstream Surface Waters of the Iranian Rivers Discharging to the Southern Caspian Sea. Environmental Science and Pollution Research, 30(40), pp. 92359–92370. https://doi.org/10.1007/s11356-023-28898-8
  9. Taghizadeh Rahmat Abadi, Z., Abtahi, B., Grossart, H.-P. and Khodabandeh, S., 2021. Microplastic Content of Kutum Fish, Rutilus frisii kutum in the Southern Caspian Sea. Science of The Total Environment, 752. 141542. https://doi.org/10.1016/j.scitotenv.2020.141542
  10. van Emmerik, T.H.M., González-Fernández, D., Laufkötter, C., Blettler, M., Lusher, A., Hurley, R. and Ryan, P.G., 2023. Focus on Plastics from Land to Aquatic Ecosystems. Environmental Research Letters, 18(4), 040401. https://doi.org/10.1088/1748-9326/acc086
  11. Litvinov, K.V., Kalmykov, A.P. and Biryukova, M.G., 2020. Microplastics as a New Component in the Ecosystem of the Lower Zone of the Volga Delta. Astrakhan Bulletin of Ecological Education, (6), pp. 147–152. https://doi.org/10.36698/2304-5957-2020-19-6-147-152 (in Russian).
  12. Zobkov, M.B. and Esiukova, E.E., 2018. Microplastics in a Marine Environment: Review of Methods for Sampling, Processing, and Analyzing Microplastics in Water, Bottom Sediments, and Coastal Deposits. Oceanology, 58(1), pp. 137–143. https://doi.org/10.1134/S0001437017060169
  13. Xu, P., Peng, G., Su, L., Gao, Y., Gao, L. and Li, D., 2018. Microplastic Risk Assessment in Surface Waters: A Case Study in the Changjiang Estuary, China. Marine Pollution Bulletin, 133, pp. 647–654. https://doi.org/10.1016/j.marpolbul.2018.06.020
  14. Lithner, D., Larsson, Å. and Dave, G., 2011. Environmental and Health Hazard Ranking and Assessment of Plastic Polymers Based on Chemical Composition. Science of the Total Environment, 409(18), pp. 3309–3324. https://doi.org/10.1016/j.scitotenv.2011.04.038
  15. Antsiferova, M.A., Glushko, A.E., Bespalova, L.A., Kleshchenkov, A.V. and Nazarenko, A.V., 2025. Microplastics in Water and Problems of Its Identification (the Water Bodies in the South of the European Part of Russia are Example). Proceedings of Voronezh State University. Series: Geography. Geoecology, (1), pp. 115–124. https://doi.org/10.17308/geo/1609-0683/2025/1/115-124 (in Russian).
  16. Antsiferova, M.A., 2024. Polymer Microparticles: Content, Distribution in the Lower Volga. Ekologia. Ekonomika. Informatika. Seriya: Sistemny Analiz i Modelirovanie Ekonomicheskikh i Ekologicheskikh Sistem, 1(9), pp. 19–21 (in Russian).
  17. Antsiferova, M.A., 2024. Concentrations of Microplastics in the Waters of the Northern Caspian Sea. In: SSC RAS, 2024. Strategic Problems, Threats, and Risks of the Sea of Azov Basin and the Sea of Azov Region (“Hazardous Phenomena–V”). Proceedings of the 5th International Scientific Conference in Memory of Corresponding Member RAS D.G. Matishov (Rostov-on-Don, 10–14 July 2024). Rostov-on-Don: SSC RAS Publishers, pp. 277–279 (in Russian).
  18. Yakushev, E., Gebruk, A., Osadchiev, A., Pakhomova, S., Lusher, A., Berezina, A., van Bavel, B., Vorozheikina, E., Chernykh, D. et al., 2021. Microplastics Distribution in the Eurasian Arctic is Affected by Atlantic Waters and Siberian Rivers. Communications Earth and Environment, 2, 23. https://doi.org/10.1038/s43247-021-00091-0
  19. Werbowski, L.M., Gilbreath, A.N., Munno, K., Zhu, X., Grbic, J., Wu, T., Sutton, R., Sedlak, M.D., Deshpande, A.D. et al., 2021. Urban Stormwater Runoff: a Major Pathway for Anthropogenic Particles, Black Rubbery Fragments, and Other Types of Microplastics to Urban Receiving Waters. ACS ES&T Water, 1(6), pp. 1420–1428. https://doi.org/10.1021/acsestwater.1c00017
  20. Kravchishina, M.D., Klyuvitkin, A.A., Lukashin, V.N., Politova, N.V., Novigatsky, A.N. and Lisitsyn, A.P., 2018. Distribution of Suspended Particulate Matter in the Caspian Sea. Russian Meteorology and Hydrology, 43(10), pp. 697–705. https://doi.org/10.3103/S1068373918100096
  21. Tsytsarin, A.G. and Lobov, A.L., 1995. Formation of Salt Barriers in the Sea of Azov, the Caspian and Aral Seas. Meteorologiya i Gidrologiya, (6), pp. 84–94 (in Russian).
  22. Lisitsyn, A.P., 1994. A Marginal Filter of the Oceans. Oceanology, 34(5), pp. 735–747 (in Russian).

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