SOME CONSIDERATIONS CONCERNING CS-137 VERTICAL PROFILE IN THE DANUBE DELTA - MATITA LAKE CORE

By using gamma-ray spectrometry and x-ray diffraction, the vertical pr ofile of Cs-137 specific activity as well as the mineralogical composi tion of a set of cores collected from the Danube Delta-Matita Lake was investigated; the observed profiles are typical for an undisturbed si te. An overlapping of the 1963 nuclear tests and 1986 Chernobyl-derive d Cs-137 specific activity peak was observed. From the experimental pr ofiles, two different values for the mixing rate, D-2 have been determ ined: D-1 = 1.81 x 10(-8) cm(2) s(-1) for the upper 10-cm layer and D- 2 = 6.20 x 10(-8) cm(2) s(-1) for the next 10-30-cm layer. These value s correspond to different bioturbation regimes. The sedimentation rate has been determined as R = 0.15 +/- 0.05 g cm(-2) year(-1). The total cesium inventory is 3.596 +/- 0.090 kBq m(-2), a value approximately equal to the sum of the nuclear tests and Chernobyl fallout.