Radioactivity Exploration from the Arctic to Antarctica. Part 5: The Tundra-94 expedition

Abstract

The joint Swedish-Russian “Tundra Ecology-94” expedition during 1994 used the large Russian ice-breaking research vessel R/V Akademik Fedorov a platform and went along a coastline of 3500 km-from the Kola Peninsula 10°E to Kolyuchinskaya Bay 173°E. Radioactivity in air, seawater and sediment was explored at various locations along the route. The average of 7Be activity concentration in air over the Arctic Ocean was found to be only about 0.6 mBq.m-3, in air close to the Siberian coast-line, however, it was as high as 11 mBq.m-3. The activity concentration of 210Pb in the air over the Arctic Ocean varies between 37 – 176 micro-Bq.m-3. In the air close to the Siberian coastline 71oN 84oE, however, the activity concentration of 210Pb in the air was much higher, about 2500 micro.Bq.m-3. Anthropogenic radioactivity in the Arctic originate from nuclear weapons fallout, release from nuclear fuel reprocessing plant, and from the Chernobyl accident. The minimum values of the 137Cs activity concentration water along the route of the Tundra were found in South-eastern Barents Sea: 5.3 Bq.m-3 of surface-water, and of bottom-water 6.4 Bq.m-3. Maximum values were found in the Western Laptevsea: 12.8 Bq.m-3 of surface-water, and of bottom-water 5.1 Bq.m-3. East of 150 oE the 134Cs / 137Cs ratios are less than 0.003, indicating that less than 6% of the 137Cs originated from the Chernobyl accident. 137Cs levels are reduced to values of about 1.4 Bq.m-3 in the low salinity water near the mouths of the Ob and Yenisey Rivers. The 134Cs / 137Cs activity ratio of 0.014 in the freshwater indicates that the Chernobyl component in the river systems is the same (30%) as in the marine waters west of 150 oE. In surface water the 90Sr activity concentration range from 2 to 4 Bq.m-3, Maximuim values about 3.5 Bq.m-3 were found between 100-140 oE. But east of 150 oE the values decreased to about 0.5 Bq.m-3 at 170 oE. In bottom water the 90Sr activity concentration range from 1.5 at 40 oE to maximum values about 4 Bq.m-3 between 100-120 oE. . The measured 90Sr/137Cs ratios in surface water close to a value of 0.14 over a wide range of stations from the Barents to the Laptev Seas. The 129I concentration in sea-water along the route of the Tundra expedition decrease from about 20·1011 atoms.l-1 at 40 oE, to about 1·1011 atoms.l-1 east of 160 oE. The 239+240Pu activity concentration in surface seawater decrease from about 10 mBq.m-3 to about 1 mBq.m-3 east of 160 oE. In bottom seawater it is more evenly distributed between 10-4 mBq.m-3, with minimum at 60-80 oE and maxima at 40oE and 160 oE. Measured 238Pu/239,240Pu activity ratios in the water column yield no evidence of any leakage of plutonium from dumped nuclear wastes in the Kara and Barents Seas. (Less)