‘SENSI’: A model describing the accumulation and time-integration of radioactive discharges in the bioindicator Fucus vesiculosus

Abstract Quantitative estimates of the concentration and turnover of radioactive metal contaminants by the brown algae Fucus vesiculosus are utilized in the model ‘SENSI’, which describes the accumulation and loss of a series of radionuclides as a function of month of contaminant discharge into the sea and month of sampling. The concepts behind ‘SENSI’ are described and its capabilities are demonstrated by comparing calculated concentrations of 65 Zn, 60 Co, 58 Co and 54 Mn with measured values in Fucus vesiculosus , sampled monthly at the Swedish nuclear power plant, Ringhals. It is concluded that the dilution of contaminant concentrations with new growth is the major cause of decreasing concentrations of previously accumulated zinc, cobalt and manganese in Fucus . The actual loss of caesium from Fucus is of the same order of magnitude as the growth dilution. The model can be used in the estimation of uncontrolled discharges and in routine quality control of discharge data.