27 
'.gS 
Jr* 
•# 
A 
IS&P 
V 
S 
•■J> 
J? 
|F*r« 
a • 
* . 
. v 
9) 
■ v|St 
1 r5oT- -TT 
m • -* 
j 
?v/ 
Total amounts of Cs-137 (Bq/m2 
O' 
o 50 000 to - 
o 
o 
100 000 to 150 000 
20 000 to 50 000 
10 000 to 20 000 
0 to 10 000 
Figure 1: 
Total amounts of ,37 Cs (Bq/m 2 ) 
at different sampling stations 
in the Baltic Sea in the late 
1990s and the beginning of the 
2000s (llus et al. 2007). Most 
of ,37 Cs is in the sediments 
of the Bothnian Sea and in 
the eastern Gulf of Finland, 
due the high deposition of 
the Chernobyl fallout in these 
areas, the high tendency 
of ,37 Cs to bind in sediment 
particles in brackish water 
environments, and the high 
sediment accumulation rates in 
these areas. 
sediment / Bq kg 1 in water) in brackish water 
environments, and because it is relatively 
easy to measure. In the recent inventory, 
we estimated that the total amount of 137 Cs 
activity in the Baltic Sea sediments was about 
2,100-2,400 TBq at the beginning of the 2000s 
(llus et al. 2007). This amount was about 8-9 
times higher compared to the pre-Chernobyl 
level in the beginning of the 1980s (Table 2). 
In recent years, caesium has continued to 
be deposited on the sea bottom and, at the 
same time its physical half-life has reduced its 
activity slowly. Most of the 137 Cs activity is in 
the sediments of the Bothnian Sea and in the 
eastern Gulf of Finland (Figure 1). The newly 
compiled data has increased our knowledge 
of the distribution of 137 Cs activity between the 
so-called hard and soft bottoms in open sea 
areas. The total amounts of 137 Cs activity on 
hard bottoms varied from 0.3% to nearly 14% 
of those recorded on soft bottoms, while the 
average ratio was only about 4% (llus et al. 
2007). 
Additional data on transuranic elements was 
also compiled during the study period. The 
reported values of 239 ' 240 Pu activities varied 
between 0.01 and 14.1 Bq kg 1 d.w. and the 
values of 238 Pu activities between 0.006 and 
0.48 Bq kg -1 . The total amount of 239 240 Pu 
was estimated to be about 15.3 TBq (Table 
2). Most of the plutonium originated from the 
Baltic Sea Environment Proceedings No. 117