12

Figure  1:
Location  of  nuclear  facilities  in
the  Baltic  Sea  region.

venly  distributed  in  the  drainage  area  of  the
Baltic  Sea;  the  most  contaminated  areas  were
situated  in  the  land  areas  surrounding  the
Bothnian  Sea  and  the  eastern  Gulf  of  Finland.
River  discharges
The  amount  of  Chernobyl-derived  137 Cs  carried ­
  into  the  Baltic  Sea  by  river  runoff  has
been  evaluated  in  Finland  for  all  Finnish  rivers
discharging  into  the  Baltic  Sea,  in  Russia  for
five  rivers  discharging  from  the  former  Soviet
Union,  and  in  Poland  for  the  River  Vistula.
Thorough  calculations  showed  that  a  total  of
65  TBq  of  137 Cs  was  discharged  by  Finnish  rivers ­
  into  the  Baltic  Sea  during  the  period  1986-1996
  (Saxen  &  llus  2000).  Corresponding
calculations  performed  in  Russia  showed  that
14  TBq  were  discharged  by  five  large  rivers

from  the  territory  of  the  former  Soviet  Union
during  the  years  1986-1988  (Gavrilov  et  al.
1990).  A  Polish  estimate  made  for  the  River
Vistula  showed  that  a  total  of  18  TBq  of  137 Cs
were  discharged  during  the  period  1986-1996
(llus  &  llus  2000).  The  total  river  input  of  137 Cs
was  estimated  at  300  TBq  during  the  decade
1986-1996  (llus  &  llus  2000).
2.3.3  Atmospheric  nuclear
weapons  tests
The  impact  of  global  fallout  caused  by  the
nuclear  weapons  tests  in  the  1950s  and
1960s  as  a  source  of  radioactivity  in  the
Baltic  Sea  was  thoroughly  considered  in  the
first  Joint  Evaluation  Report  of  the  HELCOM/
MORS  Group  (Nies  et  al.  1995).  According
to  recent  calculations  (Nielsen,  pers.  comm.),