Search

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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Radon gas (Rn-222) in water poses health risks due to radiation exposure, yet it's also an important tracer for studying natural systems. Sampling procedures for Rn-222 analysis are very sensitive to potential losses of the gas to the atmosphere. It requires a well-defined and properly validated protocol to ensure accuracy and reliability. A novel sampler was developed to collect surface water from a distance (e.g. from bridges), addressing logistic challenges posed by topography. The sampler, manually operated, ensures precise depth-specific sampling throughout the water column. A three-stage validation process (technical performance test, uncertainty estimations and preliminary test) was followed to validate the protocol.•The comparison of the technical procedure for analysis and measurement through Liquid Scintillation Counting is statistically robust (one-way ANOVA p-value = 0.96).•For the protocol proposed for Rn-222 determination, the estimated sampling and measurement uncertainties ( k = 2) are respectively 5% and 15%. These are compatible with the literature and the laboratory's precision.•Preliminary tests, with meaningful patterns identified and possibly related to the river's hydrodynamics, revealed a very reliable protocol, even in low Rn-222 concentrations.Therefore, the sampler has demonstrated a good analytical reproducibility and was considered validated for Rn-222 determination in surface waters., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors. Published by Elsevier B.V.)

Indoor radon ( 222 Rn) and thoron ( 220 Rn) are the most important natural sources of ionizing radiation to the public. Radiological studies that assess simultaneously 222 Rn and 220 Rn, and their controlling factors are particularly scarce in African countries. Hence, we conducted a survey of indoor 222 Rn and 220 Rn in buildings located in the SW region of Angola. Bedrock samples were also collected, and a borehole was executed to assess 226 Ra and 224 Ra activity concentration, 222 Rn and 220 Rn exhalation and emanation potential in the surface and at depth. The aim of this study was to determine the factors (geological and anthropogenic) that may influence the annual inhalation dose (AID) received by the population. Overall, the sum of indoor radon and indoor thoron concentrations, labelled the total indoor radon concentration (TIRC), was higher than 300 Bq/m 3 in only 5% of the buildings studied. The contribution of 220 Rn to the TIRC averaged 35% but may reach 95%, demonstrating the relevance of discriminating radon and thoron in indoor radon surveys. Indoor 222 Rn and 220 Rn were not correlated, indicating both must be estimated to properly assess the AID. Indoor 220 Rn concentrations were statistically different according to the building materials and type of usage. Higher 222 Rn and 220 Rn concentrations were observed in dwellings compared to workplaces. The median AID estimated for dwellings was 1.50 mSv/y compared to 0.26 mSv/y for workplaces, which are lower than the estimated average radiation exposure due to natural sources of 2.4 mSv/y. AID values higher than 1 mSv/y effective dose threshold established in the Council Directive 2013/59/EURATOM for the purpose of radiation protection in workplaces were observed in 12% of the workplaces studied suggesting the need for mitigation measures in those buildings. The analysis of bedrock samples revealed statistically significant correlations between 224 and 226 Ra activity concentration, and 220 Rn and 222 Rn exhalation and emanation potential. The borehole samples indicated a strong influence of weathering processes in the distribution of radioisotopes. The highest 226 Ra and 224 Ra activity concentration, and 222 Rn and 220 Rn exhaled per unit mass, TIRC and AID were observed in association with A-type red granites and porphyries. We conclude that both geological and anthropic factors, such as the type of building usage and building materials, must be considered in dose assessment studies and for the development of risk maps., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

Indoor radon ( 222 Rn) measurements were carried out using solid state nuclear track detectors (SSNTD) in some dwellings from southwestern Nigeria. This was aimed at statistically assessing influence of building characteristics on the measured radon and estimating excess lifetime cancer risks (ELCR). The measured radon concentrations followed lognormal distribution and were significantly influenced by some building properties. The arithmetic mean (1.60 mSv) of annual effective doses (AEDs) due to indoor radon was observed to be higher than the world average level (1.15 mSv) but less than lower limit (3 mSv) of International Commission on Radiological Protection (ICRP). The evaluated excess lifetime cancer risk ranged from 1.5 to 28.1 (MPy) -1 with an average value of 6.3 (MPy) -1 , indicating that after exposure to indoor radon for 70 years, 6 people in every 1000 are likely to suffer the risk of developing lung cancer. Adequate ventilation systems were recommended for houses with high level of radon to avoid unnecessary exposure to radon. However, the investigated data would form important component of the database required to set up guidelines and policy of controlling radon at home.

The correlation between radon exposure and the increased probability of lung cancer is widely recognized. In Portugal, several efforts have been made to estimate the radon potential in granitic rocks, however, existing knowledge on sedimentary rocks is limited. For this reason, extensive representative sampling was conducted in the well-known Lower and Middle Jurassic of the Lusitanian Basin (Central Portugal) to evaluate the radon potential of latter type of rocks. This paper compares the variability of 226 Ra and 222 Rn activity, emanation coefficient, and radon production rate in several lithologies deposited on paleoenvironments ranging from distal continental to deep marine. To reach this goal, 190 samples were collected in 16 well-studied outcrop sections. 226 Ra and 222 Rn activity varies between 2.8-119.6 and 0.1-19.6 Bq/kg, respectively. Higher values are linked to sandstones, fine-grained siliciclastics, marls and black shales. The emanation coefficient is lower in lithologies presenting a low siliciclastic/carbonate ratio, namely in dolostones, dolomitic limestones, limestones and marly limestones, with median values ranging between 6.5 and 9.7%. The distribution of radon production rate in the different lithological groups varies between 1.7 and 241.1 Bq.m -3 .h -1 , increasing in samples of continental source (sandstones and fine-grained siliciclastics) and proximal marine with major continental influence (dolostones), as well as from marls and black shales associated to deeper marine environments. The variability of the radon potential in sedimentary rocks varies according to lithology but, since the typical organization of these rocks in layers, the dip of these ones in each structural block also contribute to increase the variability., Competing Interests: Declaration of competing interest The authors declare no conflict of interest, financial or otherwise., (Copyright © 2020 Elsevier Ltd. All rights reserved.)