In this study, the activity concentrations of natural radionuclides in soil and beach sediment samples collected from 15 randomly but uniformly distributed locations in the coastal area of Akwa Ibom (southern Nigeria) were measured using hyper pure germanium (HPGe) detector. The activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K varied from 9 to 44 Bq/kg, 3 to 72 Bq/kg and 35 to 250 Bq/kg respectively. These results are below the 1000, 1000 and 4000 Bq/kg upper limits of safety for ²³⁸U, ²³²Th and ⁴⁰K respectively. Except ²³⁸U, ²³²Th and ⁴⁰K show lower standard deviations than their mean values, which indicate that soils and sediments have high degree of uniformity. The spatial distribution of radionuclide concentrations is nearly uniform except at locations where carbonaceous materials and clay soils exist. Mean value of Th/U ratio across the area was ≤ 7, typical of reducing condition in the depositional environment, thus suggesting enrichment of carbonaceous materials and clays. Additionally, the concentration of ⁴⁰K was observed to be slightly higher in locations where anthropic activities are prevalent. Apart from excess lifetime cancer risk (average concentration of 0.80 × 10⁻³), the average concentrations of other radiological parameters: radium equivalent (83 Bq/kg), absorbed dose rate (39 nGy/h), indoor annual effective dose equivalent (0.18 mSv/year), outdoor annual effective dose equivalent (0.05 mSv/y) and annual gonadal dose equivalent (259 μSv/y), are below permissible limits. Hence, the soils and sediments are safe and suitable for all purposes.

中文翻译：

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尼日利亚南部阿夸伊博姆海岸线土壤和海滩沉积物的放射性核素分布及相关的放射性危害评估

在这项研究中，使用超纯锗（HPGe）检测器测量了从阿克瓦伊博姆（尼日利亚南部）沿海地区的15个随机但分布均匀的位置收集的土壤和海滩沉积物样品中天然放射性核素的活动浓度。²³⁸ U，²³² Th和⁴⁰ K的活性浓度分别为9至44 Bq / kg，3至72 Bq / kg和35至250 Bq / kg。这些结果分别低于²³⁸ U，²³² Th和⁴⁰ K的1000、1000和4000 Bq / kg的安全上限。²³⁸ U，²³² Th和⁴⁰除外K的标准偏差低于其平均值，这表明土壤和沉积物具有较高的均匀度。放射性核素浓度的空间分布几乎均匀，除了存在碳质材料和粘土的地方。整个区域的Th / U比平均值平均值≤7，这是沉积环境中还原条件的典型表现，因此表明碳质物质和粘土的富集。此外，在人类活动盛行的地方，观察到⁴⁰ K的浓度略高。除了终生癌症风险过高（平均浓度为0.80×10 ^-3），其他放射学参数的平均浓度：镭当量（83 Bq / kg），吸收剂量率（39 nGy / h），室内年有效剂量当量（0.18 mSv /年），室外年有效剂量当量（0.05 mSv / y）和年性腺等效剂量（259μSv/ y）低于允许的限值。因此，土壤和沉积物是安全的，适用于所有目的。