The Derivation of Transfer Parameters in the Assessment of Radiological Impacts on Arctic Marine Biota

Abstract

The initial stage of an environmental impact assessment requires quantification of radionuclide transfer in the study area. This paper evaluates the robustness of the concentration factor (CF) approach in assessing radiological impact on reference Arctic marine biota. By comparing region-specific data sets with recommended generic values for CFs, we tested the hypothesis that transfers to Arctic biota differ from transfers observed in temperate areas for 90 Sr, 137 Cs, 239,240 Pu and 99 Tc. Despite the general paucity of data and great uncertainty regarding radionuclide CFs in reference biota, we conclude that the use of Arctic-specific CFs for Sr and Pu can be justified in some cases where differences from generic CFs seem apparent. Where CF data are absent, a biokinetic modelling approach with allometric considerations might be used to bridge data gaps. Such an approach has been used here to estimate the trophic transfer of 137 Cs and 239 Pu in a marine food chain consisting of four trophic levels. For the simulation concerning 137 Cs, the preliminary results suggest that it takes more than five years to attain equilibrium for higher trophic levels (polar cod and harp seal). Biomagnification appears to occur at the lower trophic levels, but not at the highest (seal). For 239 Pu, transfer to successively higher trophic levels is low: there is a fall of several orders of magnitude between primary producers, represented by phytoplankton, and polar cod, representing trophic levels 3 and 4. However, the model predicts that this decreasing trend in activity concentrations along the food chain is reversed for the highest trophic level, represented by seal. The simulated results for seal display equilibrium activity concentrations about two orders of magnitude higher than those observed for polar cod (one of its prey species). However, equilibrium (165 years) is not reached during the life span of a seal. The equilibrium 137 Cs CFs are approximately 50 l kg-1 for zooplankton, 130 l kg-1 for polar cod, and 70 l kg-1 seal. The predicted equilibrium 239 Pu CFs are 2.5 •10 3 l kg-1 for zooplankton and 25 l kg-1 for polar cod. For seal, following a one-year equilibration period, a CF of approximately 75 l kg-1 is predicted.

Radiocaesium (137Cs) in marine mammals from Svalbard, the Barents Sea and the North Greenland Sea

“…In the present study, 137 Cs concentration factors for seal species, although often similar in magnitude, are typically higher than those reported for lower trophic levels, which suggests that 137 Cs is biomagnified through marine food chains to these consumers. The main prey of polar bears in the study area is ringed, bearded and harp seals (Derocher et al, 2000), and the results from these species compared to data for the polar bears does not suggest biomagnification of 137 Cs; thus this observation is in agreement with the findings of Brown et al (2004). It has also been reported that radionuclide specific activities varies by age or size of the animal (Watson et al, 1999).…”

“…More recently, Brown et al (2004), utilising a biokinetic modelling approach to the trophic transfer of 137 Cs in marine food chains, demonstrated biomagnification at lower trophic levels but not to the highest level, which was represented by the harp seal in their study. In the present study, 137 Cs concentration factors for seal species, although often similar in magnitude, are typically higher than those reported for lower trophic levels, which suggests that 137 Cs is biomagnified through marine food chains to these consumers.…”

Probabilistic biokinetic modelling of radiocaesium uptake in Arctic seal species: verification of modelled data with empirical observations

“…These data were used to construct and parameterise a biokinetic model that may be used to predict activity concentrations in the whole-body of ringed seal. The food-chain model used in this study has been modified from the earlier work conducted by Brown et al (2004). The food-chain structure modelled in this study is shown in Fig.…”

Environmental impact assessment for ionising radiation within the Arctic

“…Such models have been applied to Arctic environments for the purpose of simulating transfer. The application of a multi-compartmental model, parameterised using allometrically derived values where appropriate, has allowed the derivation of Cs and Pu CRs for several Arctic marine trophic levels [12]. The preliminary estimates agreed well with empirical datasets and demonstrated that, in some cases, the application of an equilibrium CR was highly inappropriate.…”