Natural Radioactivity in Sediments and Water of Clotilde Briozzo Lagoon

The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in Clotilde Briozzo lagoon coastal sediments was determined to evaluate the external hazard index, the outdoor annual effective dose and the radium equivalent activity in order to determine if those represent a risk for inhabitants. Each sediment sample was dried and placed in a 500 mL Marinelli beaker. After approximately four weeks in order to reach secular equilibrium of ²³⁸U and ²³²Th series, samples were measured by gamma spectrometry with a high purity germanium detector. IAEA reference materials were used for efficiency calibration. The ²³⁸U series was studied by the photopeaks of ²¹⁴Bi (609.3 keV) and ²¹⁴Pb (295.2 keV). The ²³²Th series was evaluated by the photopeak of ²²⁸Ac (911.1 keV) and ⁴⁰K was evaluated by its own photopeak of 1460.8 keV. The ranges of activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K were found to be 14.92–67.86, 41.91–131.20, and 88.90–168.08 Bq/kg, respectively. The outdoor annual effective dose equivalent, the radium equivalent activity and the external hazard index associated with the samples were evaluated. Furthermore, the gross alpha and gross beta activities in water were also determined using a low background gas proportional counter. The average activity was 0.060 Bq/L. (author)