SHORT-TERM AND LONG-TERM LOSSES OF CS-137 FROM PEATLAND SOILS

Replicate soil cores were collected at adjacent peatland and mineral s oil sites in an area of low Chernobyl fallout. Three individual cores were collected at the mineral site and nine cores, subsequently bulked to give three composite samples, were taken from the peatland site. D ata are reported on the vertical distribution of Cs-137 and Cs-134 at 25 mm intervals to a depth of 225 mm. The integrated Cs-137 deposition from nuclear weapons testing, calculated as 8344 (s.e. 513) Bq m-2, s hows good agreement with a value of 7950 Bq m-2 predicted from previou s correlations with rainfall. Analysis of variance showed a highly sig nificant (P<0.001) difference in the Cs-137 retention capacity of the two different soils. The profile distribution of Cs-137 was also affec ted by soil type. Significant depletion of Cs-137, representing 62.5% of the nuclear weapons fallout and 47% of the Chernobyl deposition, wa s observed in the peatland soils. Surface run-off rather than vertical migration of Cs-137 was considered to be the dominant factor in losse s from the ecosystem in the months immediately following deposition wh ile, in later years, the radioactive half-life was the controlling inf luence. A two-compartment decay with effective half-lives of about 8 a nd 22 years, respectively, was calculated.