University of Coimbra, LRN - Laboratory of Natural Radioactivity, Department of Earth Sciences, Coimbra, Portugal.
University of Coimbra, LRN - Laboratory of Natural Radioactivity, Department of Earth Sciences, Coimbra, Portugal; University of Coimbra, CITEUC - Centre for Earth and Space Research, Department of Earth Sciences, Coimbra, Portugal.
J Environ Radioact. 2024 Sep;278:107484. doi: 10.1016/j.jenvrad.2024.107484. Epub 2024 Jun 18.
In southern African countries most of the population uses groundwater collected in dug wells for domestic consumption instead of water from public distribution systems. To investigate the impact of natural and human factors on urban groundwater quality, 276 samples were collected in the Lubango region (Angola) in water distribution systems and dug wells ranging from a few meters to almost one hundred meters in depth. Radon concentrations (RC) were determined by liquid scintillation counting according to ISO 13164-4:2015. Geology is the main source of the variability of RC, with median values higher than 100 Bq/L in granitoid units and lower values in mafic and sedimentary units (ranging from 5 to 38 Bq/L). On average, RC was higher in dug wells compared to public water distribution systems. The annual effective dose due to ingestion of radon in water is, on average, ten times lower in the later compared to dug wells. Therefore, from a public exposure perspective, water distribution systems are preferred as means for water distribution. A severe multi-year meteorological drought over the past decade affecting 76-94 % of the population in southern Angola has been linked with climate change. Consequently, a regional lowering of the water table was observed, as well as a reduction in the productivity of shallower wells, leading to a search for water at greater depths. This work demonstrates an increase in median RC from 66 Bq/L in wells shallower than 30 m to values over 100 Bq/L with increasing depth of water extraction and for the same geological unit. The highest RC observed were also observed at the deepest wells. The dose ingested is proportional to RC, being also higher at deeper water extraction depths. The increase in public radiation exposure from radon ingestion due to water extraction at greater depths is attributed to the underlying issue of climate change. Monitoring water quality in terms of radionuclide concentration is advised to ensure the exposure to ionizing radiation remains at acceptable levels in the future.
在南部非洲国家，大多数人口使用从挖掘井中采集的地下水来供家庭消费，而不是使用公共分配系统的水。为了研究自然和人为因素对城市地下水质量的影响，在安哥拉卢班戈地区的供水系统和深度从几米到近百米不等的挖掘井中采集了 276 个样本。氡浓度（RC）是根据 ISO 13164-4:2015 通过液体闪烁计数法确定的。地质是 RC 变化的主要来源，在花岗岩单元中，中位数高于 100 Bq/L，而在镁铁质和沉积单元中则较低（范围为 5 至 38 Bq/L）。平均而言，挖掘井中的 RC 高于公共供水系统。与挖掘井相比，水中氡摄入的年有效剂量平均要低十倍。因此，从公众暴露的角度来看，供水系统是首选的供水方式。过去十年，南部安哥拉 76-94%的人口受到了严重的多年气象干旱的影响，这与气候变化有关。因此，观察到地下水位下降，较浅水井的产量下降，导致人们在更深的地方寻找水源。这项工作表明，从中等深度（<30 米）的水井中 RC 的中位数从 66 Bq/L 增加到 100 Bq/L 以上，随着开采深度的增加，同一地质单元的 RC 也随之增加。观测到的最高 RC 也出现在最深的水井中。摄入的剂量与 RC 成正比，在更深的水提取深度下也更高。由于更深的水提取导致从氡摄入引起的公众辐射暴露增加，这归因于气候变化这一根本问题。建议监测水中放射性核素浓度的水质，以确保未来的电离辐射暴露保持在可接受的水平。
