Distribution of 228Ra and 226Ra in the Surface Layer of the Black Sea Waters

O. N. Kozlovskaia1, 2, D. A. Kremenchutskii1, ✉, Iu. G. Shibetskaia1, V. A. Razina1, N. A. Bezhin1, 2

1 Marine Hydrophysical Institute of RAS, Sevastopol, Russian Federation

2 Sevastopol State University, Sevastopol, Russian Federation

✉ e-mail: d.kremenchutskii@mhi-ras.ru

Abstract

Purpose. The purpose of the work is to summarize information on the features of spatial variability of the 226Ra and 228Ra concentration fields and the factors influencing these features in the surface water layer of the Black Sea.

Methods and Results. The data on spatial variability of the 228Ra and 226Ra concentrations in the surface (0.3–3.0 m) layer of the Black Sea obtained during four expeditions were used. The 228Ra and 226Ra isotopes were recovered from the seawater samples using the MnO2-based fiber. Their activity was measured by a UMF-2000 alpha-beta radiometer. The data on the content of main elements of the basic biogenic cycle were obtained photometrically.

Conclusions. The concentrations of 228Ra and 226Ra varied in a range of 17.2 to 172.2 dmp/m3 and from 38.0 to 270.1 dmp/m3, respectively. It is shown that in the region under study, the influence of submarine sources and, presumably, sewage is of a local character and is manifested in an increase of concentrations of these radionuclides or one of them by 1.5–2.3 times. The mesoscale eddies observed in the region of the Southern Coast of Crimea are assumed to affect spatial variability of the radium isotope concentration fields that results in a local decrease or increase in their concentrations by 2.3–2.8 times. It is shown that propagation of the Azov Sea waters in the Black Sea is traced by the 228Ra and 226Ra concentration fields: the increased (by 2.3–2.6 times) values of the contents of both isotopes are observed in these areas. It is established that in the areas subjected to the affect of river runoff, the concentration of long-lived radium isotopes is observed to increase with distance from the coast. The spatial scales, on which the influence of a particular source is manifested, are expected to be proportional to its power (flow rate and radionuclides concentration): the higher the power, the greater the distance at which its influence is monitored.

Keywords

228Ra, radium-228, 226Ra, radium-226, Black Sea, submarine groundwater discharge, river flow

Acknowledgements

The authors are grateful to the captain and crew of the R/V Professor Vodyanitsky for their help in carrying out expeditionary operations on the vessel, as well as to the members of the Hydrology and Currents group for providing the data on temperature and salinity. Water samples were taken in the Collective Center R/V Professor Vodyanitsky of FSBSI FSC A.O. Kovalevsky Institute of Biology of the Southern Seas. The study was carried out within the framework of a theme of state assignment of Ministry of Science and Higher Education of Russian Federation FNNN-2021-0004.

Original russian text

Original Russian Text © The Authors, 2023, published in MORSKOY GIDROFIZICHESKIY ZHURNAL, Vol. 39, Iss. 6, pp. 831–850 (2023)

For citation

Kozlovskaia, O.N., Kremenchutskii, D.A., Shibetskaia, Iu.G., Razina, V.A. and Bezhin, N.A., 2023. Distribution of 228Ra and 226Ra in the Surface Layer of the Black Sea Waters. Physical Oceanography, 30(6), pp. 792-810.

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