Quantifying Cs-137 aggregated transfer coefficients in a semi-natural woodland ecosystem adjacent to a nuclear reprocessing facility

Abstract

Radiocaesium (137Cs) activity concentrations and aggregated transfer factors (Tag values) were calculated for vascular plants, fungal fruiting bodies and invertebrates in a semi-natural Picea sitchensis woodland (Lady Wood) adjacent to the British Nuclear Fuels plc. reprocessing facility at Sellafield, Cumbria, UK. The Tag values for vascular plants ranged from 7.1×10−4–1.9×10−2 m2 kg−1, the maximum value being for Pteridium aquilinum. Fungal fruiting bodies had higher Tag values (1.9×10−3–1.8×10−1 m2 kg−1) than vascular plants, with a maximum value for Mycena galericulata. None of the activity concentrations for edible foodstuffs collected within this study (fungi and berries) exceeded the EC recommended limits of 137Cs in foodstuffs grown within the UK. The invertebrate community sampled during the study had Tag values ranging from 3.4×10−4 to 1.3×10−2 m2 kg−1. There were no systematic differences in 137Cs activity concentration between invertebrate guilds, or between seasonal cohorts within guilds. The invertebrates in Lady Wood were exposed to a dose from 137Cs (internal gamma + beta and external gamma) ranging between 4.37×10−4 and 6.40×10−4 mGy day−1. Including dose from radionuclides other than 137Cs and accounting for uncertainties due to the relative biological effectiveness of differing radionuclides could increase total dose by approximately an order of magnitude. These dose rates are at least three orders of magnitude lower than the 1 mGy d−1 level at which harm may be caused to terrestrial biota, hence the risk to the invertebrate community from the effects of ionising radiation in Lady Wood is low.