Seasonal variations in activity concentrations of ¹³⁷Cs, ⁴⁰K, ⁷Be, ²²⁸Ra, ⁹⁹Tc, ⁹⁰Sr, and $^{239,240}$Pu in Fucus vesiculosus and Ascophyllum nodosum from the southeastern coast of Norway

Abstract

The aim of this study was to compare the indicator properties of Fucus vesiculosus and Ascophyllum nodosum. Activity concentrations of ¹³⁷Cs, ⁴⁰K, ⁷Be, ²²⁸Ra, ⁹⁹Tc, ⁹⁰Sr and $^{239,240}$Pu were measured in plants of the two species collected monthly in 2002 from one location at the southeastern coast of Norway. For ⁴⁰K, ¹³⁷Cs, ⁹⁰Sr, ⁷Be and ²²⁸Ra the activity concentrations were significantly higher in Fucus vesiculosus than in Ascophyllum nodosum, whereas the opposite was the case for ⁹⁹Tc. For ¹³⁷Cs, ⁹⁰Sr, ⁷Be and ²²⁸Ra the temporal variations in activity concentrations showed similar pattern for the two species, whereas for ⁹⁹Tc the temporal pattern was different for the two species. The observed temporal variations in activity concentrations of ¹³⁷Cs (both species) and ⁹⁰Sr (only Fucus vesiculosus) correlate with expected variations in seawater concentrations. For ¹³⁷Cs salinity, light conditions, temperature and growth rates seem to work in the same direction as the variations in seawater concentrations. A lack of correlation between salinity and ⁹⁹Tc concentrations in the algae indicates a slower dynamic in uptake and/or secretion for technetium. The observed differences between the two species may partly be explained by the difference in growth rate and life length between the two species.