99Tc in seawater in the West Spitsbergen Current and adjacent areas

TRS Cs CRwo-water values for the marine environment: analysis, applications and comparisons

A new TRS document on Transfer of radionuclides to Wildlife has compiled equilibrium CR(wo-media) values for a variety of radionuclides and ecosystems. Assessment tools such as the ERICA Tool use equilibrium whole organism concentration ratios (CR(wo-media)) to predict radionuclide activity concentrations in wildlife from those in media (e.g. water). The aim of this paper is to compare and contrast model predictions of doses from (137)Cs to marine organisms using three different approaches: (i) the ERICA Tool utilising the new TRS values to estimate internal and external doses to reference organisms for the Black sea and the Aegean Sea and for the sea close to the Fukushima Dai-ichi plant. (ii) a hydrodynamic site specific model for seawater for parts of the Aegean Sea, Greece which estimates radionuclide concentrations using site specific data and (iii) a biokinetic model for fish applied to the Fukushima releases to the Pacific. The advantages and limitations of these approaches are discussed with respect to determining doses to pelagic fish. The applicability of the three approaches will vary with the objective of an assessment. The site specific model can predict variation in (137)Cs with depth and uses site specific CR values. The application of the biokinetic model to predicted (137)Cs activity concentrations in seawater and fish due to near coastal inputs from Fukushima Dai-ichi showed that the maximum internal dose-rates in fish attributable to (137)Cs would be substantially lower than those determined using equilibrium assumptions in ERICA but the accumulative doses over 100 days were similar.

Sources and pathways of 90Sr in the North Atlantic-Arctic region: present day and global warming

The spatial and temporal distributions of the anthropogenic radionuclides (137)Cs and (90)Sr, originating from nuclear bomb testing, the Sellafield reprocessing plant in the Irish Sea (UK), and from the Ob and Yenisey river discharges to the Arctic Ocean, have been simulated using the global version of the Miami Isopycnic Coordinate Ocean Model (MICOM). The physical model is forced with daily atmospheric re-analysis fields for the period of 1948-1999. Comparison of the temporal evolution of the observed and the simulated concentrations of (90)Sr has been performed in the Kara Sea. The relative contributions of the different sources on the temporal and spatial distributions of the surface (90)Sr are quantified over the simulated period. It follows that the Ob river discharge dominated the surface (90)Sr over most of the Arctic Ocean and along the eastern and western coasts of Greenland before 1960. During the period of 1980-1990, the atmospheric fallout and the Ob river discharge were equally important for the (90)Sr distribution in the Arctic Ocean. Furthermore, an attempt has been made to explore the possible dispersion of accidental released (90)Sr from the Ob and Yenisey rivers under a global warming scenario (2 x CO(2)). The difference between the present-day and the global warming scenario runs indicates that more of the released (90)Sr from the Ob and Yenisey rivers is confined to the Arctic Ocean in the global warming run, particularly in the near coastal, non-European part of the Arctic Ocean.

Monitoring of microbial metal transformations in the environment

The biotransformation of metals is an exciting, developing strategy to treat metal contamination, especially in environments that are not accessible to other remediation technologies. However, our ability to benefit from these strategies hinges on our ability to monitor these transformations in the environment. This involves monitoring metals in both solid and aqueous samples, distinguishing between different chemical states, and obtaining information on the activities of specific microbial taxa in communities that inhabit the treated site. Accomplishing these goals requires cooperation among scientists from various disciplines and would benefit from both new, innovative approaches and the tailoring of established methods to control metal mobility in the environment.

The dispersion of 99Tc in the Nordic Seas and the Arctic Ocean: a comparison of model results and observations

The radionuclide (99)Tc had been discharged from the nuclear reprocessing facility in Sellafield (UK) into the Irish Sea in increased amounts in the 1990s. We compare the simulated dispersion of (99)Tc in surface water as calculated by a hydrodynamic model and an assessment box model with field-observations from 1996 to 1999 to study concentrations, pathways and travel times. The model results are consistent with the observations and show the typical pathway of dissolved radionuclides from the Irish Sea via the North Sea along the Norwegian Coast. Subsequently the contaminated water separates into three branches of which the two Arctic branches bear the potential for future monitoring of the signal in the next decades. The results of the hydrodynamic model indicate a large variability of surface concentrations in the West Spitsbergen Current which has implications for future monitoring strategies. According to the observed and simulated distributions we suggest an improved box model structure to better capture the pattern for concentrations at the surface.