THE VERTICAL-DISTRIBUTION OF THE CS-137 DERIVED FROM CHERNOBYL FALLOUT IN THE UPPERMOST SPHAGNUM LAYER OF 2 PEATLANDS IN THE SOUTHERN ALPS (ITALY)

The patterns of concentration of the Cs-137 derived from the Chernobyl accident were analysed in a series of vertical profiles of Sphagnum c ollected at two peatlands in the southern Alps. The peak concentration s of the Chernobyl radiocesium were found in segments of Sphagnum loca ted at different distances from the growing apex, probably correspondi ng to the plant tissues produced in the 1986 vegetation season. This i ndicated that the growth rates of Sphagnum are subject to considerable variations not only between species, but also between years and even between individuals of the same species when growing in different micr ohabitats at the same site. However, the concentrations of the Chernob yl-derived radiocesium are high also in the Sphagnum segments produced after 1986. This was due to a continuous translocation of Cs-137 towa rds the capitulum, probably determined by the chemical similarity betw een cesium and potassium. Although the two sites investigated received nearly the same amounts of rainfall in the two-week period following the arrival of the Chernobyl plume, the average concentrations of radi ocesium in all Sphagnum species were significantly higher at one of th em, presumably because the fall-out deposition was conditioned by a nu mber of meteorological factors besides precipitation.