Assessment of the level and risk of radioactive hazards in coastal sediments in northern Vietnam.

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 (Ra_eq), the absorbed dose rate (ADR), the annual effective dose equivalent (AEDE), the activity utilization index (AUI), the external hazard index (H_ex), the representative level gamma index (I_γr), 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 Ra_eq, H_ex, and AUI indices were below the recommended values, while the AEDE, ADR, AGDE, and I_γr indices were above the recommended values. Moreover, ⁴⁰K, ²³²Th, ²²⁶Ra, and ²³⁸U had significant impacts on the radiation hazard indices Ra_eq, ADR, AEDE, I_γr, AUI, H_ex, 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, I_γr, and AGDE indices in the sediment threaten the living environment.