Assessment of radioactivity levels and associated radiological hazards index in lake water from eastern areas of Lake Hawassa, Sidama region, Ethiopia

Abstract Water samples from the Sidama Region of Ethiopia's Lake Hawassa have been measured for naturally occurring radioactivity. The radioisotopes of 238U (214Pb, 214Bi), 232Th (228Ac), and 40K were assessed on water samples through the use of gamma-ray spectrometry (a high-purity germanium detector). The activity concentrations (in Bq (Bq)) of these isotopes ranged from BDL to 4.17 ± 0.82, BDL to 9.13 ± 1.06 , and BDL to 92.10 ± 4.50, with average values of 2.35 ± 0.58, 6.05 ± 0.58 , and 55.13 ± 2.80 , respectively. In addition, the average values of the radiological hazard indices: external hazard index (= 0.04), absorbed dose rate ( = 7.14 nGy), and annual effective dose equivalent ( = 0.009 mSv) were assessed and compared to different countries and an international standard. According to literature from different countries, these findings of all activity concentrations and radiological hazard indices (the external hazard index, absorbed dose rate, and annual effective dose equivalent) fall within that range. It also appears to be baseline data that will facilitate ongoing assessments and comparisons of radiological safety in various environments. By establishing a reference point, it can help identify changes or trends over time, guiding future environmental policies and initiatives.摘要：对埃塞俄比亚锡达马地区哈瓦萨湖的水样开展天然放射性活度测量。采用γ射线能谱法（gamma-ray spectrometry，配备高纯锗探测器（high-purity germanium detector））对水样中的238U（对应子体核素214Pb、214Bi）、232Th（对应子体核素228Ac）及40K的放射性同位素进行分析评估。上述同位素的活度浓度（单位：贝可(Bq)）范围分别为低于检测限（BDL）至4.17±0.82 Bq、BDL至9.13±1.06 Bq以及BDL至92.10±4.50 Bq，平均活度浓度依次为2.35±0.58 Bq、6.05±0.58 Bq及55.13±2.80 Bq。此外，本研究评估了三类放射学危害指标的平均值：外照射危害指数（为0.04）、吸收剂量率（为7.14 nGy）以及年有效剂量当量（为0.009 mSv），并将其与不同国家的相关数据及国际标准进行对比。参照多国已发表文献，本次测得的所有活度浓度与放射学危害指标（外照射危害指数、吸收剂量率及年有效剂量当量）均处于已报道的合理区间内。本研究所得数据可作为基准数据，用于后续各类环境介质的放射安全评估与对比；通过建立参考基准，可助力识别随时间推移产生的变化或趋势，为未来环境政策制定与相关行动提供指导。