The vertical distribution of the Cs-137 derived from Chernobyl fall-out in the uppermostSphagnum layer of two peatlands in the southern Alps (Italy)

Abstract

The patterns of concentration of the Cs-137 derived from the Chernobyl accident were analysed in a series of vertical profiles ofSphagnum collected at two peatlands in the southern Alps. The peak concentrations of the Chernobyl radiocesium were found in segments ofSphagnum located at different distances from the growing apex, probably corresponding to the plant tissues produced in the 1986 vegetation season. This indicated that the growth rates ofSphagnum 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 microhabitats at the same site. However, the concentrations of the Chernobyl-derived radiocesium are high also in theSphagnum segments produced after 1986. This was due to a continuous translocation of Cs-137 towards the capitulum, probably determined by the chemical similarity between 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 radiocesium in allSphagnum species were significantly higher at one of them, presumably because the fall-out deposition was conditioned by a number of meteorological factors besides precipitation.