Temporal and spatial trends in the distribution of 137 Cs in surface waters of Northern European Seas-a record of 40 years of investigations
Résumé
The distribution of anthropogenic 137 Cs in surface waters of the NE Atlantic Ocean resulting from discharges from European nuclear reprocessing plants, the Chernobyl accident, and global fallout has shown decreasing concentrations in most regions in the past 2 decades, in proportion to the lessening of its release rates from the Sellafield and La Hague reprocessing plants. In contrast, concentrations increased significantly in the Baltic Sea in 1986, as a result of the Chernobyl accident. The average 137 Cs concentrations in surface water have been estimated for the year 2000 to be 60750 Bq m À3 for the Irish Sea, 371 for the Celtic Sea, 2.171.2 for the English Channel, 472 for the North Sea, 50720 for the Baltic Sea, 271 for the Norwegian Sea, 2.470.5 for the Barents Sea, and 471 Bq m À3 for the Kara Sea. On the basis of time series data, the corresponding effective half-lives of 137 Cs in surface water have been estimated to be 471 years for the Irish Sea, 271 for the Celtic Sea, 1.270.5 for the English Channel, 371 for the North Sea, 1372 for the Baltic Sea, 471 for the Norwegian Sea, 571 for the Barents Sea, and 1374 years for the Kara Sea. The mean transit times of water masses have been estimated to be 0.570.1 year from the Irish Sea to the North Channel, 270.2 years to the north of Scotland, 2.570.2 to the east coast of England, 370.5 to the southern North Sea, 470.5 to the central and eastern North Sea, 1.570.2 to the Celtic Sea, 270.2 to the English Channel, 571 to the Baltic Sea, 4.570.5 to the Norwegian Sea, 571 to the Barents Sea, and 671 years to the Kara Sea