Transport and Fate of 137Cs Released From Multiple Sources in the North Atlantic and Arctic Oceans

Abstract

The North Atlantic and Arctic oceans, along with the North Pacific, are the main reservoirs of anthropogenic radionuclides introduced in the past 75 years. The POSEIDON-R compartment model was applied to the North Atlantic and Arctic oceans to reconstruct 137Cs contamination in 1945–2020 due to multiple sources: global fallout, exchange flows with other oceans, point-source inputs in the ocean from reprocessing plants and other nuclear facilities, the impact of the Chernobyl accident and secondary contamination resulting from river runoff and redissolution from bottom sediments. The model simulated the marine environment as a system of 3D compartments comprising the water column, bottom sediment, and biota. The dynamic model described the transfer of 137Cs through the pelagic and benthic food chains. The simulation results were validated using the marine database MARIS. The calculated concentrations of 137Cs in the seaweed and non-piscivorous and piscivorous pelagic fish mostly followed the concentration of 137Cs in water. The concentration in coastal predator fish lagged behind the concentration in water as a result of a diet that includes both pelagic and benthic organisms. The impact of each considered source on the total concentration of 137Cs in non-piscivorous fish in the regions of interest was analyzed. Whereas the contribution from global fallout dominated in 1960–1970, in 1970–1990, the contribution of 137Cs released from reprocessing plants exceeded the contributions from other sources in almost all considered regions. Secondary contamination due to river runoff was less than 4% of ocean influx. The maximum total inventory of 137Cs in the Arctic Ocean (31,122 TBq) was reached in 1988, whereas the corresponding inventory in the bottom sediment was approximately 6% of the total. The general agreement between simulated and observed 137Cs concentrations in water and bottom sediment was confirmed by the estimates of geometric mean and geometric standard deviation, which varied from 0.89 to 1.29 and from 1.22 to 1.87, respectively. The approach used is useful to synthesize measurement and simulation data in areas with observational gaps. For this purpose, 13 representative regions in the North Atlantic and Arctic oceans were selected for monitoring by using the “etalon” method for classification.

Long-Term Environmental Risks of the Baltic Sea's "Memory Effect" Revealed by Ocean Modeling and Observation of Reprocessing-Derived Radiotracers

“…The outflowing Chernobyl-derived 137 Cs from the Baltic Sea has been observed in the Skagerrak and along the Norwegian coast (Povinec et al, 2003). The modeling results indicated that the outflux from the North Sea has persistent contribution (even though less important than those from global fallout and nuclear reprocessing plants) to the 137 Cs in the Northern North Sea and the Norwegian Sea since the 1990 s (Maderich et al, 2021).…”

Simulated Inventory and Distribution of 137cs Released from Multiple Sources in the Global Ocean

“…However, it is believed that larger effects were observed in the vicinity of Chernobyl than those observed in Japan. The fallout into the marginal sea of Europe, including the Black Sea, Mediterranean Sea, and North Sea, was large, while the fallout into the North Atlantic was small (Maderich et al, 2021). In this comparison, the marginal sea was excluded from consideration because an ocean general circulation model with a resolution of 1 • was used.…”

“…The effect of the Chernobyl accident can be seen, although this setting was based on fallout data from the location of the MRI in Japan and was not accurate. The impact of the Chernobyl accident in the North Atlantic was small, however the impact on the Baltic Sea and other marginal sea was significant (Maderich et al, 2021). The impact of outflows from the Baltic Sea to the North Atlantic was not considered in this study and is a subject for future work.…”

Development of a Novel DGT Passive Sampler for Measuring Cs-137 In Situ in Marine Environments

“…Consequently, monitoring programs and research studies have been giving priority for Cs-137 activity concentrations, trends, and concentration factors in contaminated areas. For example, Cs-137 analysis and accumulation monitoring in edible fishes and marine wildlife have been given great attention in Japan, 6 the European Union, 7 , 8 and U.K. 9 Regulators and stakeholders make use of concentration factors and the derived concentration guideline levels for calculations of regulated discharges. Therefore, Cs-137 monitoring in seawater is important for decision-making and for supporting disposal programs.…”