Natural radon reduction rate of the community groundwater system in South Korea

222Radon reduction in small-scale water supply systems using low-technology reduction methods in the Republic of Korea: A field research and mass balance model approach

In rural areas, low-technology radon reduction methods are essential for safe access to clean groundwater. This study monitored the radon reduction rates in small-scale groundwater-based water supply systems in the Republic of Korea and also presented a mass balance equation using physical environmental conditions from three radon reduction methods. The mass balance results showed that the radon reduction rate would be affected by the groundwater flow rate (m³/day), capacity of the drainage facility (m³), surface area of air-water interface (m²), air-water ratio (dimensionless), and ventilation system. The radon reduction order was as follows: simultaneously powered and non-powered aeration method (free-fall (60.0 %) > aeration (19.6 %) > decay (0.9 %) > diffusion (0.2 %)), low-technology non-powered aeration (free-fall (60.0 %) > decay (3.4 %) > diffusion (0.9 %)), and only storage (free-fall (35.5 %) > decay (4.4 %) > diffusion (1.1 %)). Overall, non-powered aeration using the maximum free-fall effect has the potential for use as a low-technology reduction method and natural decay during water storage is the most important factor underlying seasonal variations in the reduction effect.

Health Risk Implication and Spatial Distribution of Radon in Groundwater Along the Lithological Contact in South India

The presence of radioactive elements in groundwater results in high health risks on surrounding populations. Hence, a study was conducted in central Tamil Nadu, South India, to measure the radon levels in groundwater and determine the associated health risk. The study was conducted along the lithological contact of hard rock and sedimentary formation. The concentrations of uranium (U) varied from 0.28 to 84.65 µg/L, and the radioactivity of radon (Rn) varied from 258 to 7072 Bq/m³ in the collected groundwater samples. The spatial distribution of Rn in the study area showed that higher values were identified along the central and northern regions of the study area. The data also indicate that granitic and gneissic rocks are the major contributors to Rn in groundwater through U-enriched lithological zones. The radon levels in all samples were below the maximum concentration level, prescribed by Environmental Protection Agency. The effective dose levels for ingestion and inhalation were calculated according to parameters introduced by UNSCEAR and were found to be lesser (0.235-6.453 μSvy^-1) than the recommended limit. Hence, the regional groundwater in the study area does not pose any health risks to consumers. The spatial distribution of Rn's effective dose level indicates the higher values were mainly in the central and northern portion of the study area consist of gneissic, quarzitic, and granitic rocks. The present study showed that Rn concentrations in groundwater depend on the lithology, structural attributes, the existence of uranium minerals in rocks, and the redox conditions. The results of this study provide information on the spatial distribution of Rn in the groundwater and its potential health risk in central Tamil Nadu, India. It is anticipated that these data will help policymakers to develop plans for management of drinking water resources in the region.

Geochemical Behavior of Uranium and Radon in Groundwater of Jurassic Granite Area, Icheon, Middle Korea

Uranium concentrations (a total of 82 samples) in groundwater in Icheon, middle Korea, showed a wide range from 0.02 to 1640 μg/L with a mean of 56.77 μg/L, a median of 3.03 μg/L, and a standard deviation of 228.63 μg/L. Most groundwater samples had quite low concentrations: 32.9% were below 1 μg/L, while 15.9% exceeded 30 μg/L, the maximum contaminant level (MCL) of the US EPA (Environmental Protection Agency). Radon concentrations also ranged widely from 1.48 to 865.8 Bq/L. Although the standard deviation of radon was large (151.8 Bq/L), the mean was 211.29 Bq/L and the median was 176.86 Bq/L. Overall, 64.6% of the samples exceeded the alternative maximum contaminant level (AMCL) of the US EPA (148 Bq/L). According to statistical analyses, there was no close correlations between uranium and radon, but there were correlations between uranium and redox potential (Eh) (−0.54), dissolved oxygen (DO) (−0.50), HCO3− (0.45), Sr (0.65), and SiO2 (−0.44). Radon showed independent behavior with respect to most components in groundwater. Uranium concentrations in groundwater increased with increasing water–rock interactions. Anomalously high uranium and radon concentrations in groundwater are preferentially localized in granite areas and spatial distributions are remarkably heterogeneous.

An Assessment of Groundwater Contamination Risk with Radon Based on Clustering and Structural Models

There is currently some controversy in the scientific community regarding the efficiency of the water–rock interaction process in the contamination of radon in groundwater. In this study, some difficulties were found in the sampling phase. Many of the water collection points are used for human consumption. As such, some municipalities did not want to collaborate. When this natural contaminant is undetectable to the human sense and may cause pulmonary neoplasms in the long term, it is difficult to obtain collaboration from the municipalities concerned. To overcome this controversy, it is important to understand that geogenic, climatic, hydrological, and topographic features may contribute to the effective transfer of radon from rocks to groundwater. In brief, this new approach combines the radon transfer from the geological substrate to the groundwater circulation through hierarchic agglomerative clustering (HAC) and partial least squares-path modeling (PLS-PM) methods. The results show that some lithologies with higher radon production may not always contribute to noticeable groundwater contamination. In this group, the high-fracturing density confirms the recharge efficiency, and the physical-chemical properties of the hydraulic environment (electric conductivity) plays the main role of radon unavailability in the water intended for human consumption. Besides, the hydraulic turnover time of the springs can be considered an excellent radiological indicator in groundwater. In the absence of an anomalous radioactive source near the surface, it means that the high-turnover time of the springs leads to a low-radon concentration in the water. Besides linking high-risk areas with a short period required to free local flow discharges, this study exposes the virtues of a new perspective of a groundwater contamination risk modeling.

A New Framework for the Management and Radiological Protection of Groundwater Resources: The Implementation of a Portuguese Action Plan for Radon in Drinking Water and Impacts on Human Health

In general, this study was developed to assess the radon contamination in groundwater intended for human consumption, to raise awareness among policy-makers to implement a legal framework for drinking water management and the radiological protection of groundwater resources. Thus, we analyzed with parallel coordinate visualization (PCV) plots what features may influence the water–rock interaction and promote high-radon concentrations in water intended for human consumption. The results show that in granitic areas composed by biotite granites (Group V), although there is a higher radon production in the rocks, the radon transfer to groundwater was not effective, mainly due to the physical and chemical properties of the water. The main conclusions show that in all springs sampled (n = 69) for the entire study area, there are only four springs that must have an immediate intervention, and 22 of them are above the limit imposed by the Portuguese legislation. These results are intended to promote a Portuguese Action Plan for Radon that can be framed in the guidelines on the management and protection of groundwater resources.

Radon concentrations in the community groundwater system of South Korea

Groundwater samples were collected from 3818 wells used for the community groundwater system (CGS) in the remote rural areas of South Korea and analyzed to determine radon concentrations. Radon concentrations varied with rock type, ranging from 0.1 to 2393.5 Bq/L with an average of 86.6 Bq/L and a median of 46.4 Bq/L. Among 10 geological units, the median CGS radon concentration was highest (59.6-103.0 Bq/L) in granite, and lower in sedimentary rocks (16.9-21.1 Bq/L) and porous volcanic rocks (17.6 Bq/L), respectively. Of the 3818 samples, 26.1% exceeded the World Health Organization (WHO) radon level limit of 100 Bq/L. The application of the natural radon reduction rate (26.5%) recently suggested by Yun et al. Applied Radiation and Isotopes, 126(1), 23-25 (2017) to the CGS water tank appeared to decrease exceedance of the WHO radon level limit to 20.2%. Because of the high radon concentrations in CGS groundwater in South Korea, the establishment of a radon level limit for drinking water is strongly recommended to ensure the health and safety of the people using CGS water.