The inflow of (238)Pu and (239+240)Pu from the Vistula River catchment area to the Baltic Sea

Vertical distribution of 241Am in the southern Baltic Sea sediment profiles

The contamination of the Baltic Sea with radioactive substances occurred due to the global fallout of atmospheric nuclear weapon tests and the Chernobyl disaster. The knowledge of 241Am in the sediments of the Baltic Sea is limited. Thus, this study aimed to determine 241Am in sediment cores collected from the southern Baltic Sea. Time-based distributions were derived from age-depth profiles using the 210Pb dating method and further corroborated by 137Cs profiles. The activities of 241Am were measured by alpha spectrometry after radiochemical purification. The results show divergences in the concentrations of 241Am at the local level, varying from 0.017 ± 0.001 Bq·kg-1 at the Gotland Basin station to 3.19 ± 0.23 Bq·kg-1 in the Gdańsk Basin. These findings enhance our understanding of the radioactive contamination levels in the Baltic Sea and serve as a crucial reference dataset for future assessments and management strategies to mitigate the environmental impact of radionuclides in the region.

Distribution of 241Am and Pu isotopes in the Curonian Lagoon and the south-eastern Baltic Sea seawater, suspended particles, sediments and biota

Distribution trends and temporal variations of 241Am and Pu isotopes in the south-eastern Baltic Sea during the study period of 1999-2001 and 2011-2015 were investigated with the aim to study temporal changes of radionuclide levels in seawater, suspended particles and sediment, to estimate 241Am and 239,240Pu levels in marine biota and to assess the radiation doses received by the biota. The activities of 241Am and 239,240Pu were measured by alpha spectrometry after radiochemical purification. 241Pu was determined radiometrically via the ingrown daughter 241Am after 10-12 years of storage, while the 240Pu/239Pu atom ratio of was measured by accelerator mass spectrometry. The 239,240Pu activities in suspended particles collected in the coastal waters of the Baltic Sea decreased by a factor of ∼3 during the study period, while they decreased about fourfold in the Curonian Lagoon. This could indicate a decrease in the influx of particles containing Pu isotopes into the Baltic Sea. While in the Curonian Lagoon, the 239,240Pu activities in the sediment samples varied insignificantly during the study periods, in the Baltic Sea, the maximum activity decreased by a factor of 6, and the mean/median values decreased by ∼4 times. The assessment tool ERICA was used to calculate the dose rates for biota. The total dose rate from all analysed radionuclides was <0.1 μGy/h, therefore no risk to organisms was identified.

Estimation of plutonium 241Pu budget in the Gulf of Gdańsk and the Gdańsk Basin (the southern Baltic Sea)

Presented have been the results of inventory estimation of anthropogenic beta-emitting ²⁴¹Pu, in different components in the southern Baltic Sea ecosystem. The total ²⁴¹Pu activity present in the Gulf of Gdańsk and the Gdańsk Basin for 2021 was estimated at 1.99 TBq and 7.82 TBq, respectively, of which 1.59 TBq and 6.38 TBq in the sediments. The Vistula and the Neman River and the atmospheric fallout were distinguished as the primary sources of plutonium in these basins. In seawater of the Gulf of Gdańsk, there was about 0.40 TBq ²⁴¹Pu (20.1% of total activity) and 1.44 TBq ²⁴¹Pu (18.4% of total activity) in the Gdańsk Basin. The ²⁴¹Pu accumulated in living organisms in 2021 was 1.13 GBq in the Gulf of Gdańsk and 3.96 GBq in the Gdańsk Basin. In the Gulf of Gdańsk biota, 55.7% was accumulated in zoobenthos, while in the Gdańsk Basin, 48.3% was in zoobenthos.

A Review of the Occurrence of Alpha-Emitting Radionuclides in Wild Mushrooms

Alpha-emitting radioisotopes are the most toxic among all radionuclides. In particular, medium to long-lived isotopes of the heavier metals are of the greatest concern to human health and radiological safety. This review focuses on the most common alpha-emitting radionuclides of natural and anthropogenic origin in wild mushrooms from around the world. Mushrooms bio-accumulate a range of mineral ionic constituents and radioactive elements to different extents, and are therefore considered as suitable bio-indicators of environmental pollution. The available literature indicates that the natural radionuclide 210Po is accumulated at the highest levels (up to 22 kBq/kg dry weight (dw) in wild mushrooms from Finland), while among synthetic nuclides, the highest levels of up to 53.8 Bq/kg dw of 239+240Pu were reported in Ukrainian mushrooms. The capacity to retain the activity of individual nuclides varies between mushrooms, which is of particular interest for edible species that are consumed either locally or, in some cases, also traded on an international scale. The effective radiation dose from the ingestion of this food can reportedly range from 0.033 µSv/kg dw to 26.8 mSv/kg and varies depending on the country. Following pollution events, such consumption may expose consumers to highly radiotoxic decay particles produced by alpha emitters.

Uranium (234U, 238U) and thorium (230Th, 232Th) in mushrooms of genus Leccinum and Leccinellum and the potential effective ionizing radiation dose assessment for human

Evaluated has been bioconcentration potential by fungi and risk to human consumers from exposure to natural long-lived radioactive uranium (²³⁴U, ²³⁸U) and thorium (²³⁰Th, ²³²Th) sequestered in stems, caps and the whole fruiting bodies by mushrooms of the genus Leccinum and Leccinellum. Edible species in the study were collected from boreal forests in the northern regions of Poland and investigated: red-capped scaber (Leccinum aurantiacum), orange oak bolete (Leccinum aurantiacum var. quercinum), foxy bolete (Leccinum vulpinum), slate bolete (Leccinum aurantiacum var. duriusculum) and hazel bolete (Leccinellum pseudoscabrum). The study showed the species accumulated uranium (²³⁴U, ²³⁸U) and thorium (^230Th, ²³²Th) form soil to some degree but the calculated values of the bioconcentration factor were below 1. The evaluation showed that Leccinum and Leccinellum mushrooms can contribute to annual effective radiation dose maximally at about 0.9 μSv. Hence, consumption of these mushrooms might increase the annual effective ionizing radiation dose received by a human, while the exposure is considered low from the toxicological point of view even if eaten at elevated amounts.

On the distribution and inventories of radionuclides in dated sediments around the Swedish coast

The activity concentrations and distribution of ¹³⁷Cs, ²³⁸Pu, ^239+240Pu, ²⁴¹Am, and ²¹⁰Pb was determined by the analysis of six sediment cores from the Baltic Sea and Kattegat. The chronology of the sediment cores has been used to evaluate the origin and time trend of the radionuclide sources in these sediments. The sediment cores were dated with a ²¹⁰Pb model and the results were validated with fallout peaks, assumed to originate from the global nuclear weapons testing and the Chernobyl accident. Source identification, using the isotopic and radionuclide activity ratios, showed that the Chernobyl accident is the main source of ¹³⁷Cs in the Baltic Sea; for ^239+240Pu and ²⁴¹Am the dominant source was shown to be fallout from nuclear weapons tests. For ²³⁸Pu and ²⁴¹Am the Chernobyl accident had a significant impact on the direct fallout into the Baltic Proper, with up to a 65% contribution in the sediment slices dated to 1986. In these sediment slices the maximum activity ratios of ²³⁸Pu/^239+240Pu and ²⁴¹Am/^239+240Pu were 0.314 ± 0.008 and 1.29 ± 0.06, respectively. The ratios clearly deviate from the corresponding ratios for global nuclear weapons fallout (around 0.028 and 0.54, respectively). Calculated inventories were 63-175 Bq·m^-2 for ^239+240Pu, 2.8-7.8 for ²³⁸Pu Bq·m^-2 and 0.92-44.4 kBq·m^-2 for ¹³⁷Cs. Different fallout patterns for ¹³⁷Cs and plutonium isotopes from the Chernobyl accident were confirmed through depth profiles analyses. The maximum inventory of ¹³⁷Cs was observed in the Bothnian Sea, while Chernobyl-derived plutonium was found to be mostly present in Northern Baltic Proper. The radionuclides distribution in the depth profiles shows how contaminated water affects the sediment as it passes sampling stations according to the current circulation pattern in the Baltic Sea. Additionally, the effect of increased activity concentrations from of river discharges in the most contaminated area in the Bothnian Sea was observed.

Carbon and Pu isotopes in Baltic Sea sediments

Distributions of ¹³⁷Cs, ^239,240Pu, Δ¹⁴C and δ¹³C measured in sediments indicated low ¹³⁷Cs and ^239,240Pu activities in the Curonian Lagoon and higher levels in the open Baltic Sea. Depleted δ¹³C_TOC values were found in the Curonian Lagoon as compared with the open Baltic Sea, while the most depleted Δ¹⁴C_TOC values were found in the Gotland Deep. The global fallout Pu dominated in the deeper zones of the Baltic Sea, while higher ²⁴⁰Pu/²³⁹Pu atom ratios were characteristic of the coastal regions.

Transport of (137)Cs, (241)Am and Pu isotopes in the Curonian Lagoon and the Baltic Sea

Activities of (137)Cs, (241)Am and (239,240)Pu were analyzed with special emphasis on better understanding of radionuclide transport from land via the Neman River estuaries to the Baltic Sea and behavior in the marine environment. Although activity concentrations of (137)Cs in water samples collected the Baltic Sea were almost 100 times higher as compared to the Curonian Lagoon, its activities in the bottom sediments were found to be comparable. Activity (238)Pu/(239,240)Pu and atom (240)Pu/(239)Pu ratios indicated a different contribution of the Chernobyl-originated Pu to the suspended particulate matter (SPM) and bottom sediments. The largest amount of the Chernobyl-derived Pu was found in the smallest suspended matter particles of 0.2-1 μm in size collected in the Klaipeda Strait in 2011-2012. The decrease of characteristic activity (238)Pu/(239,240)Pu and atom (240)Pu/(239)Pu ratios towards the global fallout ones in surface soil and the corresponding increase of plutonium (Pu) ratios in the suspended particulate matter and bottom sediments have indicated that the Chernobyl-derived Pu, primarily deposited on the soil surface, was washed out and transported to the Baltic Sea. Behavior of (241)Am was found to be similar to that of Pu isotopes.

241Pu concentrations in water, plankton and fish from the southern Baltic Sea

The aim of the work was to determine 241Pu activities in different components (water, plankton and fish) of the southern Baltic Sea ecosystem. Measurement of 241Pu in the samples was done indirectly by determining the increment in 241Am from the decay of the β-emitting 241Pu in samples collected 10–15 years after the Chernobyl accident.

Enhanced levels of 241Pu were observed in all analyzed Baltic samples. The highest 241Pu concentrations in fish were found in Perciformes: benthic round goby (0.863 ± 0.066 mBq/g ww) and pelagic perch (0.666 ± 0.001 mBq/g ww). Plutonium is also non-uniformly distributed in the organs and tissues of the analyzed fish; especially pelagic herring and cod as well as benthic flounder. Most of 241Pu in flounder, herring and cod is located in soft tissues, especially digestive organs (stomach, intestine, liver). The annual individual effective doses calculated on the basis of 241Pu concentrations in fish indicated that the impact of the consumption of 241Pu containing Baltic fish on the annual effective dose for a statistical inhabitant of Poland was very small.

241Pu in the biggest Polish rivers

In the paper the results of ²⁴¹Pu activity concentration determination in the biggest Polish rivers are presented. The analysis of more than 100 river water samples showed the Vistula and the Odra as well as three Pomeranian Rivers are important sources of ²⁴¹Pu in the southern Baltic Sea. There were differences in ²⁴¹Pu activities depending on season and sampling site and the plutonium contamination came mainly from the global atmospheric fallout as well as the Chernobyl accident, which is confirmed by plutonium activity ratios of ²⁴¹Pu/^239+240Pu and ²³⁸Pu/^239+240Pu.

The inflow of 238Pu and (239+240)Pu from the Odra and Pomeranian rivers catchments area to the Baltic Sea

The aim of the work was to estimate plutonium inflow from the Odra River catchments area to the Baltic Sea. The highest activities of (238)Pu and (239+240)Pu were observed in a winter and a spring season. The highest annual surface inflow of (239+240)Pu from the Odra River watershed was observed for a mountain tributary the Bóbr (1230 Bq km(-2) year(-1)). The annual inflow of (238)Pu and (239+240)Pu to the Baltic Sea was estimated at 9.51 MBq and 45.86 MBq respectively and the highest plutonium surface runoff was observed for the Bóbr drainage.

Polonium, uranium and plutonium radionuclides in aquatic and land ecosystem of Poland

This article presents the results of study about distribution, inflow and accumulation of polonium, uranium and plutonium in aquatic and land environment of Poland and the southern Baltic Sea. Radionuclides of (210)Po, (234)U and (238)U as well as (239+240)Pu and (241)Pu are strongly accumulated in Baltic organisms and plants and transferred through the trophic chain. The values of bioconcentration factor (BCF) in Baltic plants and animals are higher for polonium and plutonium in comparison with uranium. The principal source of radionuclides in the southern Baltic Sea is their inflow with rivers. Total annual runoff of polonium, uranium and plutonium from the Vistula and the Odra as well as the Pomeranian rivers were calculated at 95 GBq of (210)Po, 750 GBq of (234+238)U and 160 MBq of (238+239+240)Pu. Seasonal and spatial variability of (210)Po, (238)U and (239+240)Pu levels in the Vistula and the Odra drainage basins were assessed by application of neural-network based classification, especially cluster analysis (CA), principal component analysis (PCA) and self-organizing maps (SOM). The result for the Vistula river indicated correlation between polonium and plutonium as well as polonium and uranium. In the Odra drainage basin, the biggest differences were observed in the case of (238)U. To assess if there are statistically significant differences in mean concentration values of (210)Po, (238)U and (239+240)Pu for the Vistula and the Odra rivers drainage basins were obtained by used of the non-parametric tests. Comparing to the Vistula catchment area, statistically differences concentration of (210)Po and (239+240)Pu in all year was observed for river samples collected on the Odra drainage basin.

Plutonium fractionation in southern Baltic Sea sediments

In this study, different chemical plutonium fractions (dissolved in water, connected to carbonates, connected to oxides, complexed with organic matter, mineral acids soluble and the rest) in sediments from the Vistula River estuary, the Gdańsk Basin and the Bornholm Deep were determined. The distribution of (239+240)Pu in analysed sediments samples was not uniform but dependent on its chemical form, depth and the sediment geomorphology. The highest amount of plutonium exists in middle parts of sediments and comes from the global atmospheric fallout from nuclear tests in 1958-1961. According to all analysed fractions, the biggest amount of (239+240)Pu was in the mobile form, connected to carbonate fractions from the Vistula River estuary, the Gulf of Gdańsk and the Bornholm Deep sediments.