Levels of radionuclide concentrations in benthic invertebrate species from the Balearic Islands, Western Mediterranean, during 2012-2018

The distribution of radiotoxic 137Cs concentrations in seaweed and mussel species in the Mediterranean Sea

A study was conducted to determine the 137Cs activity concentrations in various seaweed and mussel samples from the North East Mediterranean Sea, including the brown algae (Dictyota dichotoma) and oarweed (Laminaria digitata), and mussel species (Haliotis asinina, Mytilus edulis and Mytilus galloprovinciali). The 137Cs activity concentration in seaweed species exhibited varying levels, ranging from 84.20 ± 1.82 to 236.05 ± 5.72 mBq kg-1 fresh weight (fw) for oarweed, and 106.29 ± 2.26 to 252.38 ± 6.04 mBq kg-1 fw for brown algae. The 137Cs value in mussel species were between 12.94 ± 0.51-101.84 ± 1.35 mBq kg-1 fw for M. galloprovincialis, 15.49 ± 0.58-71.52 ± 1.16 mBq kg-1 fw for M. edulis, and 10.36 ± 0.11-69.13 ± 1.34 mBq kg-1 fw for H. asinine. When comparing the 137Cs concentration in seaweed and mussel species, the average concentration in seaweeds was approximately four times higher than that in mussels. This significant difference in radioisotope concentration highlights the potential for higher bioaccumulation of 137Cs in seaweeds compared to mussels.

Radiotoxic fission products and radiological effects in the Mediterranean Sea biota from a hypothetical accident in Akkuyu Nuclear Power Plant

A combined hydrodynamic/radiobiological model was used to calculate the distribution and dose rate of significant radionuclides in the Mediterranean Sea marine organisms in the event of an accident at the Akkuyu Nuclear Power Plant (ANPP). The Hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) model was applied to simulate the dispersion and deposition of artificial radionuclide concentrations. Environmental Risk from Ionising Contaminants: Assessment and Management (ERICA) tools were utilized to assess issues related to sea health and potential hazards in case of an accident. The scenario source term profile was derived from the Fukushima nuclear power accident. Volumetric concentrations and deposition levels of pollutants increased from 1 MBqm^-3 to 1 × 10³ MBqm^-3 and from 1 × 10^-1 MBqm^-2 to 1 × 10^-7 MBqm^-2 after 48 h. In terms of dose rates to the various marine biotas, polychaete worms had the greatest overall dose rate and the highest contribution to total dose rates attributable to ¹³⁷Cs radionuclide.

Current understanding and research needs for ecological risk assessments of naturally occurring radioactive materials (NORM) in subsea oil and gas pipelines

Thousands of offshore oil and gas facilities are coming to the end of their life in jurisdictions worldwide and will require decommissioning. In-situ decommissioning, where the subsea components of that infrastructure are left in the marine environment following the end of its productive life, has been proposed as an option that delivers net benefits, including from: ecological benefits from the establishment of artificial reefs, economic benefits from associated fisheries, reduced costs and improved human safety outcomes for operators. However, potential negative impacts, such as the ecological risk of residual contaminants, are not well understood. Naturally occurring radioactive materials (NORM) are a class of contaminants found in some oil and gas infrastructure (e.g. pipelines) and includes radionuclides of uranium, thorium, radium, radon, lead, and polonium. NORM are ubiquitous in oil and gas reservoirs around the world and may form contamination products including scales and sludges in subsea infrastructure due to their chemistries and the physical processes of oil and gas extraction. The risk that NORM from these sources pose to marine ecosystems is not yet understood meaning that decisions made about decommissioning may not deliver the best outcomes for environments. In this review, we consider the life of NORM-contamination products in oil and gas systems, their expected exposure pathways in the marine environment, and possible ecological impacts following release. These are accompanied by the key research priorities that need to better describe risk associated with decommissioning options.

The anthropogenic radiotoxic element of 137Cs accumulate to biota in the Mediterranean Sea

The abundance of ¹³⁷Cs radionuclide in the Mediterranean Sea has limited study despite its environmental effects in seafood chains. For this purpose, the activity concentration of ¹³⁷Cs in sediment and seawater have been determined using a high-resolution HPGe gamma-spectrometry system. The average activity concentrations in sediment and water were 14.16 Bq kg^-1 and 1.74 mBq L^-1, respectively. The results were used as input data of ERICA Tool modelling software to assess marine organisms' accumulation and dose. The highest and lowest accumulate activity concentration values were observed in birds (9.24E-01 Bq kg^-1) and the Vascular plant (1.37E-02 Bq kg¹), respectively. The total dose rate value was ranged between 1.94E-06 μGy h^-1 (Phytoplankton) to 4.70E-03 μGy h^-1 (Polychaete worm). The total dose rates of ¹³⁷Cs to the selected organisms were all <0.001 μGy h^-1, and there is no significant risk to marine biota in the study area.

Baseline levels of natural radionuclides concentration in sediments East coastline of North Cyprus

In this study, surface sediment samples from the North Cyprus East coast of the Mediterranean Sea were collected to determine the concentrations of three main natural radionuclides (²²⁶Ra, ²³²Th, and ⁴⁰K) using a high-resolution HPGe gamma-spectroscopy system. The activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in the selected sediment samples ranged from 11.5 to 31.6, 11.8 to 24.9, and 391.7 to 1014 Bq kg^-1 dw (dry weight), respectively. The concentration distribution analysis showed that the kurtosis statistics parameter was negative, and the concentration distribution was less peaked than the normal curve. The mean activity concentrations of ⁴⁰K (628.1 Bq kg^-1) in the sediment samples was higher than the worldwide average (420 Bq kg^-1) concentration. The radium equivalent activity, external hazard, internal hazard and gamma activity concentration indexes were calculated to assess the pollution and risk level of radionuclides. The radiological risk assessment indicated that observed values were below the threshold values.

Heavy metals and natural radioactivity concentration in sediments of the Mediterranean Sea coast

Heavy metal assessment and natural radioactivity determination in sediments of North Cyprus (Mediterranean coast) were carried out using different analysis methods. The average activity concentrations (range) of ²²⁶Ra, ²³²Th, and ⁴⁰K were found to be 20.1 (30.6-9.2) Bq kg^-1dry weight, 18.4 (26.9-12.4) Bq kg^-1dw, and 467.3 (619.9-147.6) Bq kg^-1dw, respectively. The average activity concentrations of ²²⁶Ra and ²³²Th in the sediment samples were less than the acceptable limits, whereas the average activity concentration of ⁴⁰K in the sediment samples was higher than the worldwide average concentration. With regard to the studied heavy metals, the corresponding decreasing average concentration orders were found to be Mn > Zn > Cr > Ni > Cu > Pb. The heavy metal concentration values that were determined for sediment samples were compared with the values obtained in other studies. According to contamination indexes, the results (except for Cu in S-9) indicated no significant contaminated area.