Master Thesis
A study in environmental chemistry: natural and anthropogenic radionuclides in sediment cores from the Norwegian Trench and the Vefsnfjord by Lena Helvik Master of Science Thesis Department of Chemistry University of Bergen Bergen, June 2019 SUMMARY In this work the anthropogenic radionuclide 137Cs and the naturally occurring radionuclides 226Ra, 228Ra, 210Pb and 40K have been studied in sediment cores from the Norwegian Trench and from the Vefsnfjord in Nordland. Caesium-137 is a fission product, introduced to the environment by nuclear weapons tests in 1950s and -60s, discharges from reprocessing plants for spent nuclear fuel, and from accidents like the Chernobyl accident in 1986. Levels of 137Cs in Norwegian marine areas are generally low, and the levels are routinely monitored. Investigations in selected Norwegian fjords have, however, shown elevated levels of 137Cs in surface sediments and sediment profiles, compared to adjacent open marine areas. The Vefsnfjord, which is investigated in this work, is one of the fjords in Norway with the highest measured levels of 137Cs. The contamination source is most likely the Chernobyl accident. Potassium-40 is a naturally occurring radioactive isotope of potassium (isotopic abundance of 0.012%). radium-226 and lead-210 are members of the natural radioactive “uranium series”, while radium-228 is member of the natural radioactive “thorium series”. All four are found in various amounts in bedrock and the marine environment. However, it is well known that different industries, including the oil and gas industry, also discharge naturally occurring radionuclides to the marine environment. In this thesis, local and regional variations of 137Cs, 226Ra, 228Ra, 210Pb and 40K in the two study areas have been investigated.
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