Proceeding from that the radioactive inventory of the surface layer 
areally calculated and is represented as areal deposition. Fig. 19 
shows the Cs 137 distribution pattern of the surface deposition in 
kBq/m2 resulting from the mean radionuclide ratio Cs 134/Cs 137. 
The integration of the deposition over the North Sea surfaces inve- 
stigated, gives an input of circa 1300 TBq Cs 137. In comparison 
thereto, the total Cs 137 inventory of the North Sea in 1984 was 
circa 2200 TBq - the principal source of which was Sellafield Works. 
Below 40 m depth, the contamination, owing to mixing of the water 
column after the Chernobyl input, is only partly recognizable. It 
cannot be excluded that the vertical transport of the nuclides, due 
to the transport of adsorpted activity on particulate material, will 
be accelerated into the depths. (The samples were analyzed unfil- 
tered.) Radioactivity adsorpted onto small particles, therefore, was 
included in the analysis. 
B.4 
Sediment and suspended matter samples 
The sediment is an essential depository for the deposition of ra- 
dionuclides which have entered the sea. Each according to the che- 
mical properties of the radioactive elements and each according to 
the texture of the suspended matter, the corresponding radioactive 
nuclides enrich themselves after sedimentation on the sea bottom. 
For a series of nuclides, this enrichment signifies a largely irre- 
versible process, by which the radioactivity of the water column {is 
5cavenged and then concentrated in the surface of the sediment. For 
example, this is applicable to Ag 110m, Zr 95/Nb 95, Mn 54, Co 60, 
and the Transuranics, and also for the natural isotopes such as e. 
g. Pb 210/Po 210 and Th 234. For the benthic organisms this nuclide 
enrichment represents the main source for the assimilation of radio- 
nuclides, which in this way find the essential entrance into the nu- 
trient chain, and thereby into the radiation burden path of the sea. 
Besides the investigation of the final whereabouts of the radionu- 
clides in the sea, the Fallout from Chernobyl can be used for the 
study of marine geological and sediment biological processes. It 
labels the sediments of the North Sea and the Baltic Sea with a 
clear signal, which can be called upon in the coming years for da- 
ting purposes. The study of bioturbation processes in the sediment 
surface can also be carried out from this. The knowledge to be 
gained thereby are transferable to other pollutants, so that gene- 
rally valid ecological statements can be made therefrom. For that 
reason, the investigation of the sediments and suspended matter will 
be more intensively carried out in the future. 
Analyses results of the sediment surface of a sediment sample, taken 
from the North Sea on 8th August in the mud sedimentation area 
north-eastwards to Light Vessel "Elbe 1", allude to the contamina- 
tion, which had taken place at that time. The specific activity of 
Cs 137, Cs 134, Ru 106, Ag 110m, are significantly increased. On the 
öther hand, the activity in the sample of the isotopes Co 60 and