The radioactivity levels were measured using a hand-held gamma-ray survey meter and NaI (Tl) based gamma spectroscopy to evaluate the seasonal variation of radioactivity levels in the riverine area of Ado-Odo Ota. The measured iso-dose map reported higher gamma dose rate of 79 nGy/h, approximately 34% higher than the world average of 59 nGy/h. The values for U-238, Th-232 and K-40 activity levels ranged between 29.9 and 21.6; 103.2 and 31.2; 802.2 and 233.5 with mean values of 26.1, 55.6 and 499.3 Bq/kg, respectively. According to the mean, 5th and 95th percentiles of the probabilities using the Monte Carlo simulation, the Radium equivalent activities and the absorbed dose rates are within their respective recommended limits of 370 Bq/kg and 84 nGy/h. This study could be used to monitor dose rates and radiological risks for the areas covering the small area (Ado-Odo Ota) to the larger area (West African Region) as baseline data.

中文翻译：

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尼日利亚西南部 ADO-ODO OTA 河流土壤沉积物中放射性分布的季节变化测量：使用蒙特卡洛的概率方法

使用手持式伽马射线测量仪和基于 NaI (Tl) 的伽马能谱测量放射性水平，以评估 Ado-Odo Ota 河流地区放射性水平的季节性变化。测量的等剂量图报告了 79 nGy/h 的更高伽马剂量率，比 59 nGy/h 的世界平均水平高出约 34%。U-238、Th-232 和 K-40 活性水平的值介于 29.9 和 21.6 之间；103.2 和 31.2；802.2 和 233.5，平均值分别为 26.1、55.6 和 499.3 Bq/kg。根据使用蒙特卡罗模拟的概率的平均值、第 5 个和第 95 个百分位数，镭当量活度和吸收剂量率均在各自推荐的 370 Bq/kg 和 84 nGy/h 限制范围内。