222Rn Concentrations In Groundwater Research Articles

222Rn in selected waters sources from Quang Nam - Da Nang region - Central part of Vietnam

This paper presents the radon concentrations of forty-eight samples collected from lakes, streams and rivers as surface water, from dug well as ground water and from boreholes and thermal waters as underground waters in the Da Nang – Quang Nam, central part of Vietnam. The measured radon concentrations varied from 0.265 (in lake water) to 107 Bq L−1 (in underground water) with the following trend from the lowest to the highest: 222Rn in lakes<222Rn in rivers<222Rn in stream<222Rn in dug wells<222Rn in thermal waters<222Rn in drilled wells. Overall, the average 222Rn concentration in groundwater is twelve times higher than that in the surface water.Assuming that each person drinks 2.10−3 m3 d−1 and uses six cubic meters for washing purposes per month, the estimated total annual effective dose due to ingestion and inhalation of radon from the studied water samples ranges from 1.3 to 541 μSv y−1 for adults; from 1.2 to 479 μSv y−1 for children; and from 2.1 to 838 μSv y−1 for infants.

Spatial distribution of radon concentration and risk evaluation through consumption of groundwater in the District of Kotli, Azad Jammu and Kashmir

Radon (222Rn) is naturally readily water-soluble, posing a cancer risk to the exposed community. Human exposure in the community may occur via 222Rn intake in drinking water. Groundwater is used for drinking and other domestic purposes in the region. Higher concentrations of 222Rn in groundwater have been reported near Kotli district, Azad Jammu, and Kashmir. This investigation aimed to measure 222Rn concentrations in groundwater and evaluate the associated risk assessment for children and adults in the Kotli district. 222Rn concentrations were measured in randomly collected groundwater samples of Kotli (n = 25) and Sehnsa (n = 15) towns in the Kotli district using the portable Radon Detector (RAD7, Durridge Company, United States of America). Among the studied areas, the Sehnsa showed a higher average 222Rn concentration (7.6 ± 0.2 Bq/L) in groundwater compared to Kotli (6.0 ± 1.9 Bq/L). The average concentrations of 222Rn were found within the recommended limit (11.1 Bq/L) of the United States Environmental Protection Agency (USEPA), except for 10% of sampling sites. 222Rn concentrations were used for the calculation of total effective dose for ingestion and inhalation pathways (EwTotal) values for infants (24.5 ± 7.5 and 30.7 ± 0.9 μSv/a), children (18.1 ± 5.5 and 23.5 ± 0.7 μSv/a), and adults (18.1 ± 5.5 and 22.7 ± 0.3 μSv/a) in the Kotli and Sehnsa, respectively. This study noted that EwTotal and estimated lifetime cancer risk (ELCR) values were found within the World Health Organization (WHO) and European Commission (EU) acceptable limits (<100 μ Sv/a and 0.1 × 10−3).

Elevated radon level in drinking water of Ajodhya Hill Area of West Bengal, India: probable health impact on lung and stomach.

A screening survey has been carried out to measure the radon concentration in drinking water at various locations of Ajodhya hill and surrounding areas in Purulia district of West Bengal, India, using AlphaGUARD radon monitor. The obtained 222Rn concentration in ground water varies from 5.71 ± 0.29 to 579.47 ± 23.18Bq/l with an average of 110.00 ± 6.61Bq/l. Comparison between our results with the internationally recommended reference levels reveals that drinking of water from the majority of these tube-wells can pose significant health risks to the local people. Correlation study indicates that tube-well depth has significant influence on the radon level in water samples. Using 60l/yr and 1642.50l/yr water consumption estimated annual effective radon doses for most of the samples (almost 70% and 96%, respectively) are high compared to the World Health Organization (WHO) and the European Union (EU) Commission prescribed reference dose limit of 100 μSv/yr. Also, the evaluated Excess Lifetime Cancer Risk (ELCR) values associated with the tube-wells are showing serious threat to the health of the locals.The primary goal of this work is to develop a radon profile map of this area and to find out the possible reasons behind the elevated radon level in ground water. This type of work may play a very crucial role to aware the locals in perspective of human exposure to radon. The local health officials and the water quality regulators of India are requested to take necessary steps for protecting the local people from water radon hazard.

Spatial distribution of radon concentrations in groundwater and annual exposure doses in Mirpur District Pakistan

Radon (222Rn) is a readily water-soluble naturally occurring carcinogenic gas and poses serious threats to a humans’ health. This study aimed to investigate 222Rn concentration in groundwater and associated health risks. For this purpose, groundwater samples (n = 36) were collected from the Mirpur District (3 towns: Jatlan, Mirpur, and Dadyal), Pakistan. The concentration of 222Rn in groundwater samples was measured by the RAD7 (Durridge Company, USA). Results showed that the average 222Rn concentrations in groundwater were 5.99 ± 1.41, 5.39 ± 0.89, and 13.6 ± 3.33 Bq/l of Jatlan, Dadyal, and Mirpur, respectively. These results revealed that mean concentrations of 222Rn were found within the maximum threshold limits (MCL, 11.1 Bq/l) of the United States Environmental Protection Agency (USEPA), however, that of Mirpur surpassed these limits. The concentrations of 222Rn in Mirpur District were evaluated for the annual effective doses (EwTotal). Results revealed that mean EwTotal values of the three studied sites in Mirpur District were found lower than the threshold limit (100 μSv/a), except 6% of sampling sites in the Mirpur. Higher EwTotal values than the WHO threshold limit in the Mirpur could pose threat to human health. The estimated lifetime cancer risk showed higher values along with the Mirpur of the study area. Therefore, this study recommends that water in the Mirpur area should be aerated or heated before consumption to avoid 222Rn impact on human health.

Natural 222Rn as a tracer of mixing and volatilization in a shallow aquifer during a CO2 injection experiment

AbstractThis study aims to evaluate the application of 222Rn in groundwater as a tracer for monitoring CO2 plume migration in a shallow groundwater system, which is important to detect potential CO2 leakage in the carbon capture and storage (CCS) project. For this research, an artificial CO2‐infused water injection experiment was performed in a shallow aquifer by monitoring hydrogeochemical parameters, including 222Rn. Radon in groundwater can be a useful tracer because of its sensitivity to sudden changes in subsurface environment. To monitor the CO2 plume migration, the data were analysed based on (a) the influence of mixing processes on the distribution of 222Rn induced by the artificial injection experiment and (b) the influence of a carrier gas role by CO2 on the variation of 222Rn. The spatio‐temporal distributions of radon concentrations were successfully explained in association with horizontal and vertical mixing processes by the CO2‐infused water injection. Additionally, the mixing ratios of each monitoring well were calculated, quantitatively confirming the influence of these mixing processes on the distribution of radon concentrations. Moreover, one monitoring well showed a high positive relationship between 222Rn and Total dissolved inorganic carbon (TIC) by the carrier gas effect of CO2 through volatilization from the CO2 plume. It indicated the applicability of 222Rn as a sensitive tracer to directly monitor CO2 leakage. When with a little effect of carrier gas, natural 222Rn in groundwater can be used to compute mixing ratio of CO2‐infused water indicative of CO2 migration pathways. CO2 carrier gas effect can possibly increase 222Rn concentration in groundwater and, if fully verified with more field tests, will pose a great potential to be used as a natural tracer for CO2.

Annual effective dose of radon in groundwater samples for different age groups in Obuasi and Offinso in the Ashanti Region, Ghana

The study presents radon (222Rn) activity concentration in the groundwater samples and their annual effective dose exposure in Offinso and Obuasi in the Ashanti, Region for different age groups. Radon measurement was made using Durridge RAD-7 H2O technique. In Obuasi, mean 222Rn concentration in groundwater was 0.09 ± 0.01 Bq l−1, mean annual effective dose due to ingestion for adult, child and infant were 0.64 ± 0.11 μSv yr−1, 1.28 ± 0.21 μSv yr−1 and 4.46 ± 0.73 μSv yr−1 respectively and the mean annual effective dose due to inhalation was 0.28 ± 0.05 mSv yr−1 for the dry season whiles in the rainy season the mean 222Rn concentration in groundwater was 0.08 ± 0.01 Bq l−1, the mean annual effective dose due to ingestion for adult, child and infant was 0.56 ± 0.09 μSv yr−1, 1.13 ± 0.18 μSv yr−1, 3.94 ± 0.62 μSv yr−1 respectively and the annual effective dose due to inhalation was 0.24 ± 0.04 mSv yr−1. In Offinso , the mean 222Rn concentration in groundwater was 0.14 ± 0.05 Bq l−1, mean annual effective dose due to ingestion for adult, child and infant was 1.03 ± 0.37 μSv yr−1, 2.06 ± 0.74 μSv yr−1, and 7.20 ± 0.74 μSv yr−1 respectively and the mean annual inhalation dose a mean of 0.46 ± 0.16 mSv yr−1 for the dry season. In the rainy season, the mean indoor 222Rn concentration in groundwater was 0.13 ± 0.04 Bq l−1, mean annual effective dose due to ingestion for adult, child and infant was 1.26 ± 0.31 μSv yr−1, 1.89 ± 0.61 μSv yr−1 and 6.62 ± 2.15 μSv yr−1 respectively and the mean annual effective dose due to inhalation was mean of 0.41 ± 0.13 mSv yr−1. The mean annual effective doses of all the samples are lower than the reference level of 0.1 mSvyr−1 for drinking water of WHO and EU Council. It has been concluded that drinking water of the study area is generally safe as far as radon related health hazards are concerned apart from a few isolated cases. It has been found that radon levels within the region have a positive correlation with depth of the water sources.

Constraining the temporal variations of Ra isotopes and Rn in the groundwater end-member: Implications for derived SGD estimates

Submarine groundwater discharge (SGD) has been recognized as an important supplier of chemical compounds to the ocean that may influence coastal geochemical cycles. Radium isotopes (223Ra, 224Ra, 226Ra,228Ra) and radon (222Rn) have been widely applied as tracers of SGD. Their application requires the appropriate characterization of both the concentrations of tracers in the discharging groundwater and their distribution in the coastal water column. This study evaluates the temporal evolution of Ra isotopes and 222Rn concentrations in a dynamic subterranean estuary of a microtidal Mediterranean coastal aquifer that experiences large displacements of the fresh-saltwater interface as a necessary initial step in evaluating the influence of SGD in coastal waters. We show that changes in groundwater salinities due to the seaward displacement of the fresh-saltwater interface produced large variations in Ra activities in groundwater (by a factor of ~19, ~14, ~6, and ~11 for 223Ra, 224Ra, 226Ra and 228Ra, respectively), most importantly during rainfall events. In contrast, the 222Rn activities in groundwater oscillated only by a factor of 3 during these rainy periods. The large temporal variability in Ra activities hampers the characterization of the SGD end-member when using Ra isotopes as tracers, and thus presents a challenge for obtaining accurate SGD estimates. This study emphasizes the need to understand the hydrodynamics of coastal aquifers to appropriately constrain the Ra isotopes and 222Rn concentrations in groundwater and when applying both tracers in dynamic microtidal coastal systems.

Variación espacial de la composición de 222Rn en los acuíferos Barva y Colima Superior, Costa Rica

MEN: El 222Rn es un trazador natural que permite determinar la conectividad entre las aguas subterráneas y las superficiales. El estudio presenta el primer análisis espacial de 222Rn en aguas subterráneas, superficiales y agua potable de la red de abastecimiento en los acuíferos Barva y Colima Superior en el Valle Central de Costa Rica. Se analizó la composición de 222Rn, δ18O y otras variables físico-químicas in situ en un total de 40 sitios de muestreo. En general, las nacientes de la zona norte presentaron una composición homogénea de 222Rn con una concentración promedio de 21,3 Bq/L. La concentración de 222Rn en los pozos varió entre 2,0 Bq/L y 50,5 Bq/L. Las altas concentraciones de 222Rn en algunos pozos pueden atribuirse a la desgasificación profunda a través de los fallamientos locales. En la red de abastecimiento de agua potable, la concentración de 222Rn varió entre 4,7 Bq/L y 30,8 Bq/L. Los valores encontrados en la red de abastecimiento, superiores al límite sugerido por la Agencia de Protección Ambiental de los Estados Unidos (11,1 Bq/L) para agua de consumo humano, pueden atribuirse al corto tiempo de residencia del agua de extracción subterránea en la red de abastecimiento. La utilización de tanques de almacenamiento o captación permitiría aumentar el tiempo de residencia del agua antes de ingresar a la red de consumo, facilitando la pérdida de 222Rn hacia la atmósfera o por decaimiento radioactivo. Asimismo, un análisis espacial es requerido a escala nacional, especialmente, en áreas de fallas activas o actividad volcánica.

Is 222Rn a suitable tracer of stream–groundwater interactions? A case study in central Italy

River water infiltration into an unconfined porous aquifer (∼73% gravels, ∼12% sands, ∼15% silts and clays) in the Petrignano d’Assisi plain, central Italy, was traced combining isotopic techniques (222Rn) with hydrochemical and hydrogeologic techniques in order to characterize the system under study. The 222Rn gave information about the river water residence times within the aquifer and hydrochemical data, in a two-component mixing model, which allowed estimating the extent of mixing between surface waters and groundwater in wells at increasing distances from the river. The mixing measured in the well closer to the riverbank indicated a higher contribution of river water (up to 99%) during the groundwater recession phase and a moderate contribution (up to 64%) during the recharge phase. A model describing 222Rn concentrations in groundwater as the result of both parent/daughter nuclide equilibrium and mixing process (222Rn mixing/saturation model) was used to describe observed Rn concentrations and mixing index trends with the aim of evaluating water mean infiltration velocities along the transect. The stream bank infiltration velocities obtained by the model ranged from 1mday−1 during groundwater recharge periods, when river water infiltration is lower, to 39mday−1 during recession phases, when river water infiltration is larger.

Studies on radiation dose due to radioactive elements present in ground water and soil samples around Mysore city, India

A systematic study of the ground water and soil samples collected from different locations around Mysore city (12(°)N and 76(°)E) has been carried out. (226)Ra activity concentration in water samples varies from 0.28 to 189 mBq l(-1) with a geometric mean (GM) of 4.75 mBq l(-1) and (222)Rn concentration in ground water varies from 4.25 to 435 Bq l(-1) with a GM of 25.9 Bq l(-1). The GM of inhalation and ingestion doses due to (222)Rn in water is 65.2 and 5.43, µSv y(-1), respectively. The measured GM gamma dose rate in air is 85.4 nGy h(-1) and absorbed dose rate estimated from the measured activity of radionuclides is 92.6 nGy h(-1).

Preliminary studies on 222Rn concentration in ground water from selected areas of the Accra metropolis in Ghana

Preliminary studies on groundwater samples from selected wells in three communities in the Greater Accra region of Ghana have been carried out to determine the concentration of 222Rn. The studies were carried out in the dry season when the weather conditions were fairly stable and the communities depend mostly on groundwater sources for domestic use during this period. Measurements were carried out using gamma spectrometry. The average activity concentration obtained was 8.1 Bq/L with an average annual effective dose of 59.2 μSv. The result is within the range published by other countries and the recommended limit for radon in drinking water set by the World Health Organization.

222Rn concentration in ground water and river water of coastal Karnataka

The paper discusses the result of systematic measurement of activity concentration of radon in ground water and surface water samples of two major rivers of coastal Karnataka, namely, Kali and Sharavathi. Water radon concentrations were measured using an Alpha Guard PQ2000Pro (Genitron GmbH) equipped with an appropriate unit (Aquakit), following a protocol proposed by the manufacturer. 222Rn concentration in bore well water was found to vary in the range of 0.91 – 15.86 Bq l - 1 , for open well water the 222Rn concentration was found to vary in the range of 0.33 – 9.70 Bq l - 1 in the catchment areas of Kali river. The 222Rn concentration was found to vary in the range of 1.07 – 10.72 Bq l - 1 and 2.01 – 10.02 Bq l - 1 for bore well and open well, respectively, in the catchment areas of Sharavathi river. In the surface water of Kali river the 222Rn concentration was found to vary in the range of 0.16 – 1.79 Bq l - 1 and for surface water of Sharavathi 222Rn concentration was found to vary in the range of 1.19 – 9.92 Bq l - 1 , respectively.

Influence of Inundation of Ground Surface on 222Rn Concentrations in Shallow Groundwater

Radon-222 (222Rn) is a good indicator for analyzing the speed at which surface water infiltrates the ground and reaches groundwater. Preferential flow, which is very fast, is expected to occur when the ground surface is inundated. Piston flow, which is very slow, is expected to occur when the ground surface is not inundated but is only sprinkled with water such as during a light rainfall. We hypothesized that preferential flow would reduce the 222Rn concentration in groundwater but that piston flow would not ; our study verified this hypothesis experimentally. We then measured 222Rn concentrations in groundwater for one year in lowland and upland locations. 222Rn concentrations in groundwater decreased at the lowland site, where the ground surface was inundated by irrigation and heavy rainfall, while 222Rn concentrations in groundwater did not decrease at the upland site, where the ground surface was not inundated.

Estimation of groundwater flow rate using the decay of 222Rn in a well

A method of estimating groundwater flow rate using the decay of 222Rn in a well was investigated. Field application revealed that infiltrated water (i.e., precipitation, pond water and irrigation water) accelerated groundwater flow. In addition, the depth at which groundwater was influenced by surface water was determined. The velocity of groundwater in a test well was estimated to be of the order of 10-6cms-1, based on the ratio of 222Rn concentration in groundwater before and after it flowed into the well. This method is applicable for monitoring of groundwater flow rate where the velocity in a well is from 10-5 to 10-6cms-1.

Analysis of recharge by paddy field irrigation using 222Rn concentration in groundwater as an indicator

Groundwater recharge must be well understood in order that water resources can be effectively used and contamination of groundwater by surface water can be prevented. Evaluating recharge from groundwater levels alone does not show downward flow when outflow exceeds recharge. This article showed the variation of 222Rn concentrations in soil water according to degree of saturation in the aquifer. The theory used for analysis is based on gas solubility theory between two phases, liquid and gas. Field investigation confirmed that 222Rn concentration in the groundwater at the surface of a saturated zone decreases with downward flow in the unsaturated zone above. After that, we investigated the recharge by paddy fields with the method using 222Rn concentration in the groundwater at the surface of a saturated zone. The results showed that the state of recharge could be analyzed as expected, i.e., the occurrence of downward flow of soil water pushed out by irrigation water, unsaturated percolation during the irrigation period, and the redistribution of soil water after the release of ponding water. The degree of saturation of downward flow in the unsaturated zone was calculated to be about 50% from the ratio of 222Rn concentration in the irrigation period to that in the non-irrigation period. This shows that the downward flow in the underlying layer was very unsaturated. When the groundwater table is deep, and less pervious soil overlies more pervious soil, it is known that percolation from paddy fields is unsaturated in the underlying layer. Since the saturated hydraulic conductivity of the underlying layer was on the order of 10−1 cm/s and that of surface soil is 10−5 to 10−6 cm/s, it is likely that unsaturated downward flow occurred. The 222Rn concentration in the groundwater at the surface of a saturated zone is a useful indicator for detecting the existence of downward flow to the saturated zone through an unsaturated aquifer.

An evaluation of 222Rn concentrations in Idaho groundwater.

Factors potentially correlated with 222Rn concentrations in groundwater were evaluated using a database compiled by the U.S. Geological Survey. These included chemical and radiological factors, and both well depth and discharge rate. The 222Rn concentrations contained within this database were examined as a function of latitude and longitude. It was observed that the U.S. Geological Survey sample locations for 222Rn were not uniformly distributed throughout the state. Hence, additional samples were collected in southeastern Idaho, a region where few 222Rn in water analyses had been performed. 222Rn concentrations in groundwater, in Idaho, were found using ANOVA (alpha = 0.05) to be independent of the chemical, radiological, and well parameters thus far examined. This lack of correlation with other water quality and well parameters is consistent with findings in other geographical locations. It was observed that an inverse relationship between radon concentration and water hardness may exist.

222Rn transport in a fractured crystalline rock aquifer: results from numerical simulations

Dissolved 222Rn concentrations in ground water from a small wellfield underlain by fractured Middle Proterozoic Pikes Peak Granite southwest of Denver, Colorado range from 124 to 840 kBq m −3 (3360-22700 pCi L −1). Numerical simulations of flow and transport between two wells show that differences in equivalent hydraulic aperture of transmissive fractures, assuming a simplified two-fracture system and the parallel-plate model, can account for the different 222Rn concentrations in each well under steady-state conditions. Transient flow and transport simulations show that 222Rn concentrations along the fracture profile are influenced by 222Rn concentrations in the adjoining fracture and depend on boundary conditions, proximity of the pumping well to the fracture intersection, transmissivity of the conductive fractures, and pumping rate. Non-homogeneous distribution (point sources) of 222Rn parent radionuclides, uranium and 226Ra, can strongly perturb the dissolved 222Rn concentrations in a fracture system. Without detailed information on the geometry and hydraulic properties of the connected fracture system, it may be impossible to distinguish the influence of factors controlling 222Rn distribution or to determine location of 222Rn point sources in the field in areas where ground water exhibits moderate 222Rn concentrations. Flow and transport simulations of a hypothetical multifracture system consisting of ten connected fractures, each 10 m in length with fracture apertures ranging from 0.1 to 1.0 mm, show that 222Rn concentrations at the pumping well can vary significantly over time. Assuming parallel-plate flow, transmissivities of the hypothetical system vary over four orders of magnitude because transmissivity varies with the cube of fracture aperture. The extreme hydraulic heterogeneity of the simple hypothetical system leads to widely ranging 222Rn values, even assuming homogeneous distribution of uranium and 226Ra along fracture walls. Consequently, it is concluded that 222Rn concentrations vary, not only with the geometric and stress factors noted above, but also according to local fracture aperture distribution, local groundwater residence time, and flux of 222Rn from parent radionuclides along fracture walls.

Investigation on Shallow Groundwater in a Small Basin Using Natural Radioisotopes.

The authors conducted an investigation on shallow groundwater using natural radioisotopes as indicators in the small basin of the Hinuma River, Kasama City, Ibaraki Prefecture, Japan.3H concentrations in the groundwater showed that it originated from precipitation in the 1960's. Since 222Rn concentrations decreased as groundwater flowed downstream, they were influenced by infiltration of surface water. Especially, during the irrigation period, the decrease of 222Rn concentrations was remarkable in the lowland. From the distribution of 222Rn concentrations in surface water, the sections where groundwater seeped into a river were found, and a quantitative analysis of groundwater seepage in the two sections was conducted on the basis of 222Rn concentrations in groundwater and in surface water. The ratios of groundwater seepage to the flow at the upstream station for the two sections were about 5% and 10%, respectively. The water movement within the basin, i.e., the actual manner in which surface water infiltrated underground and groundwater seeped into a river, was clarified by analyzing the variations of natural radioisotope concentrations in water and the water balance of the basin.

The 222Rn content of groundwater in strata of the Plio-Pleistocene Osaka Group in the Sennan area, Japan

Studies on the 222Rn content of groundwater were conducted to obtain knowledge of its distribution in the geosphere just below ground surface and below the depth of 100 m in the Osaka Group (Plio-Pleistocene). Samples analyzed from ten bore holes within 10 m depth below land surface showed that a sandy layer contained groundwater with consistent radon concentrations except for a few locations where the variations in the water level were large due to precipitation and/or the water level was within 2 m of ground surface. The average 222Rn concentration in groundwater within 10 m of land surface was found to be approximately equal to 1 3 to 3 5 of the highest concentration found in groundwater from a well penetrating 100–200 m (420 pCi/l −1).