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Radioactivity in coastal sediments in northern Vietnam was examined using data from five sediment cores to assess radioactivity concentrations and radiation risk indices. Radiation risk indices included radium equivalent activity (Raeq), the absorbed dose rate (ADR), the annual effective dose equivalent (AEDE), the activity utilization index (AUI), the external hazard index (Hex), the representative level gamma index (Iγr), and the annual gonadal effective dose rate (AGDE). The radioactivity concentrations of 40K, 232Th, 226Ra, 238U, and 137Cs were 567, 56.1, 35.1, 37.9, and 1.18 Bq/kg, respectively. The average concentrations of 40K, 232Th, 226Ra, and 238U were above the global average at five sites, except for 137Cs, which was low. The Raeq, Hex, and AUI indices were below the recommended values, while the AEDE, ADR, AGDE, and Iγr indices were above the recommended values. Moreover, 40K, 232Th, 226Ra, and 238U had significant impacts on the radiation hazard indices Raeq, ADR, AEDE, Iγr, AUI, Hex, and AGDE. There are three coastal sediment groups on the northern coast of Vietnam: Group 1 has a higher radioactivity and radiation risk index than Group 2 but a lower value than Group 3. Group 3 had the highest radioactivity and radiation risk index. The values of 40K, 232Th, 226Ra, and 238U and the ADR, AUI, Iγr, and AGDE indices in the sediment threaten the living environment. [ABSTRACT FROM AUTHOR]

A method employing 137Cs sorption to copper hexacyanoferrate (Cu2[Fe(CN)6])-coated fibers for determining 137Cs activity in seawater is presented in this paper. The Cu2[Fe(CN)6]-coated fibers were packed into a PVC cartridge and used to treat 300 L of seawater, exhibiting a 137Cs sorption efficiency of above 99%. The Cu2[Fe(CN)6]-fiber samples containing 137Cs were subsequently dried and placed into a 500 mL Marinelli beaker to determine the activity concentrations by gamma spectrometry. This method was applied to seawater of the Phuoc Dinh and Vinh Hai coastal areas in Ninh Thuan province, Vietnam. The activity concentrations of 137Cs in the surveyed areas ranged from 1.14 to 1.44 Bq/m3. The activities of 137Cs in the seawater samples of this work were compared with those observed in seawater on the coasts of Vietnam and other countries along the South China Sea. [ABSTRACT FROM AUTHOR]