Natural and artificial radionuclide activity concentrations in surface sediments of Izmit Bay, Turkey

Surface sediments from the north-eastern coast of the Marmara Sea, Turkey's most industrialized coastal region, were enriched with radioisotopes from the Chernobyl explosion in 1986. Caesium-137 in these sediments is also thought to originate from one former paper mill located nearby that used wood contaminated by Chernobyl explosion-originated 137Cs for paper production. The average activity concentration of the 137Cs was 21 Bq kg−1, while naturally occurring radioisotopes, i.e. 40K, 226Ra, and 228Ra, were 568, 18 and 24 Bq kg−1, respectively, in surface sediments. The natural radionuclide activities reached their highest levels near petrochemical, phosphate and fertilizer processing facilities. Average 137Cs activities were generally up to ten times higher than in Middle Eastern marine sediments and lower than those in Northern European sediments.