P-003

Sergej Šemčuk1

sergej.semcuk@ftmc.lt

Galina Lujanienė1, Vitaliy Romanenko2, Jonas Mažeika2

1Department of Environmental Research, Center for Physical Sciences and Technology (FTMC), Vilnius, Lithuania

2Laboratory of Nuclear Geophysics and Radioecology, Nature Research Centre, Vilnius, Lithuania

Investigation of the transport and accumulation of radionuclides in the Neman – Curonian Lagoon – Southern Baltic Sea system

The Baltic Sea is an inland water body with a relatively shallow depth and weak water circulation, which is mainly determined by wave action and creates favourable conditions for the accumulation of various pollutants in the bottom sediments of the sea. The main sources of pollution are human activities and the rivers that flow into the sea, carrying various substances that are absorbed by suspended matter. Of particular concern among all pollutants are the long-lived radionuclides (137Cs, 210Pb, 239,240Pu, 241Am, etc.) that have fallen to the earth's surface with the global fallout from nuclear weapons tests and nuclear accidents in nuclear power plants. In addition, their ability to rapidly disperse and accumulate affects the environment and contributes to bioaccumulation in living organisms and onward migration along the food chain, which can also affect human well-being [1-3]. The aim of this work was to investigate peculiarities of natural and artificial radionuclides distribution in the bottom sediments of the Neman River, the Curonian Lagoon and the deep waters of the southern Baltic Sea.

The radionuclides in the collected bottom sediment samples were analysed using alpha and gamma spectroscopy. To determine the carbonates and organic matter in the sediment samples, a Loss on Ignition (LOI) procedure was performed, which includes drying at 105 °C, ignition at 550 °C and ignition at 950 °C with mass registration changes of the samples after each step. The particle size distribution (from 0.4 µm to 2020 µm) was determined using a laser particle analyser (Analysette 22 MicroTec-plus). The particle size separation techniques were used to separate the sediments into fractions prior to the gamma-emitting radionuclide measurements. The samples were analysed using various radioanalytical methods [4] to determine the content of alpha-emitting isotopes (239,240Pu). Portions of 30–100 g of soil sediment dried at 550 °C were weighed and a 242Pu tracer was added to each sample to monitor losses in subsequent procedures. The samples were then dissolved in strong acids, separated by liquid-liquid extraction and purified using chromatography columns. Finally, the purified Pu isotopes were electroplated on stainless steel plates and measured by alpha spectroscopy. The results of radionuclide activity concentrations of 40K, 137Cs, 210,214Pb, 239,240Pu were analysed and plotted using statistical software (GraphPad Prism, 2024) and R (R core team, 2024; Wickham, 2016). The measured values of radionuclide activity were as follows: for 137Cs between 8 and 220 Bq/kg, 239,240Pu – 0.5 to 2.1 Bq/kg, 40K – 600 to 1100 Bq/kg, 210Pb – 112 to 171 Bq/kg and 214Pb – 25 to 80 Bq/kg. The information obtained is useful for analysing the slow and complex distribution of radionuclides in the environment. The data obtained can help to understand and predict the behaviour of other pollutants, their accumulation areas and transport pathways, and can also be used for predictive modelling.

References:

[1] G. Lujanienė et al., 2014, Journal of Environmental Radioactivity. Vol. 127, pp. 40–49.

[2] V. Romanenko et al., 2023, Lithuanian Journal of Physics. Vol. 63, No. 2, pp. 105–112.

[3] V. Romanenko et al., 2024, Journal of Radiation Research and Applied Sciences. Vol. 17, 101114.

[4] G. Lujaniene et al., 2022, Journal of Environmental Radioactivity, 249, Article 106892.