engleski

Mosses as Bioindikators of Radioactive Contamination

Mosses, lichens and perennial plants, all characterized by slow growth, are able to efficiently accumulate different radionuclides from their environment to a much higher degree than other vegetation. Consequently, they are sensitive bioindicators of radioactive contamination for various ecosystems. Results of systematic, long-term measurements of 137Cs activities in mosses for the period 1986-2006 are summarized. The study was conducted in the Radiation Protection Unit of the Institute for Medical Research and Occupational Health in Zagreb, as a part of an extensive monitoring program of the Croatian environment. All the samples were gamma-spectrometrically analysed using HPGe and/or Ge(Li) detector (resolution 1.78 keV on 1.33 MeV 60Co, relative efficiency 16.8% ; resolution 1.56 keV on 1.33 MeV 60Co, relative efficiency 18.7%) coupled to data acquisition system. The samples were measured in Marinelli beakers of 1 l volume. Counting time was 80.000 s or higher. Radiocaesium activity concentrations in mosses are in good correlation with fallout activities. In the overall observed period the highest activity concentration of 137Cs deposited by fallout has been recorded in 1986, which is the year of Chernobyl accident, causing peak 137Cs activity concentration in moss of (maximum value being 8800 Bqkg-1 and mean value 3150 Bqkg-1). For comparison, in the same year mean concentration in grass was 919 Bqkg-1 After the Chernobyl nuclear accident the 134Cs: 137Cs activity ratio in moss was 0.5 and did not differ from the value found in other environmental samples. Ten year after Chernobyl accident, in 1996, mean 137Cs activity concentration in moss was 1345 Bqkg-1 with maximum value of 3940 Bqkg-1. In 2006, mean 137Cs activity concentration in mosses was 251 Bqkg-1 with maximum value of 955 Bqkg-1

moss; bioindicators; radiocaesium; radioactive contamination

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