Assessment of radioactivity and radiological risk indices in the sediments of the Tam Giang-Cau Hai, Thi Nai, and Nai lagoons in the Center of Vietnam

Using gamma and alpha spectrometers, the radioactive isotopes Ra-226, Pb-210, Th-232, and K-40 were determined in three sediment cores from the Tam Giang-Cau Hai (TG), Thi Nai (TN), and Nai (DN) lagoons, and radiation risk indices were computed. The radioactivity concentrations of Pb-210, K-40, Th-232, and Ra-226 were 55.46 Bq/kg, 675.78 Bq/kg, 67.22 Bq/kg, and 34.15 Bq/kg, respectively. The Ra-eq, ADR, AEDE, I-gamma r, AUI, Hex, and AGDE indices were 182.31 Bq/kg, 84.46 nGy/h, 0.10 mSV/y, 1.35, 1, 18, 0.49, and 598.71 mu SV/y, respectively; the values of K-40, Th-232, AEDE, ADR, I-gamma r, and AGDE were greater than the global average and UNSCEAR values. The radioactivity and radiation risk indices decreased in the order DN > TN > TG.