Radon Monitoring Research Articles

ASSESSMENT OF RADON CONCENTRATION AND ASSOCIATED HEALTH IMPLICATIONS IN GROUND WATER AND SOIL AROUND RIRUWAI MINE SITE, KANO STATE, NIGERIA AND ITS ENVIRONS

In this study 10 soil and 11 ground water samples were randomly collected, and the 222Rn concentrations were measured using a DURRIDGE RAD7 electronic radon detector. The radon concentration in ground water ranged from 0.53 BqL-1 to 5.13 BqL-1 with a mean value 2.37 BqL-1. The results show that all the groundwater samples collected have 222Rn concentrations below the US EPA Maximum Contaminant Level (MCL) of 11.1 BqL–1 (for states without radon monitoring policy and enhanced indoor air programs). All the ground water samples also have 222Rn concentrations below MCL of 100 BqL–1 recommended by EU. The annual effective dose due to ingestion (Hing) of 222Rn in the groundwater ranged from 0.00386 – 0.03744 mSvyear-1 with a mean value of 0.01706 mSvyear-1. These values are within the ICRP recommended reference level of 1 mSvy–1 for the intake of the radionuclide in water by the general public for a prolonged exposure. The effective radium content, radon mass exhalation rate and alpha index of the soil samples varied from 0.574 – 1.170 Bqkg-1, 0.104 Bqkg-1d-1 – 0,212 Bqkg-1d-1 and 0.00287 – 0.00585 respectively. The alpha index suggests that none of the selected soil samples have a radon mass exhalation that could cause indoor radon concentrations exceeding 200 Bqkg-1. Therefore, it is concluded that the radon concentration in ground water and soil in the study area indicate that the ground water is safe for drinking and it is safe to use the soil as a building material.

Connection between 222Rn emission and geophysical-geochemical parameters recorded during the volcanic unrest at Campi Flegrei caldera (2011–2017)

Studies concerning 222Rn emission from soils are growing interest in the Earth Sciences, due to the gas potential as a tracer of natural phenomena. This paper presents a study of radon monitoring in two sites of Campi Flegrei caldera (Neaples, Italy) during the period July 1, 2011–December 31, 2017. This area was characterized by several phases of volcanic unrest. A hybrid method based on Multiple Linear Regression + Remote Radon Estimation method + Singular Spectrum Analysis (MLR + RRE + SSA) is developed for the trend extraction and the identification of anomalies in the time series of 222Rn. The results are compared with several routinely used geo-indicators of the caldera unrest. The comparisons show strong correlation among the signals. The present study proves the 222Rn is a potential indicator of the evolution of a volcanic crisis.

Evaluation of indoor air pollutants in 100 retrofit residential buildings from Romania during cold season

The indoor air quality (IAQ) was in the last decades a major topic of scientific research due to evidences of adverse effects of different chemicals on the human health. The retrofit of the existing buildings in order to increase the energy performance without proper implementation may have a negative effect on IAQ. This paper is focused on a comprehensive evaluation of indoor air pollutants in 100 retrofit houses from five Romanian cities, during cold season. Radon, volatile organic compounds (VOCs) and carbonyl compounds were determined using passive samplers. At the same time, continuous, real-time monitoring of radon and carbon dioxide concentrations, as well as indoor physical parameters, such as temperature, atmospheric pressure and relative humidity was carried out. In 95% of the houses the formaldehyde concentration was higher than the guidevalue. The most present volatile organic compounds were limonene, heptane, carbon tetrachloride, tetradecane and a-pinene. A statistically significant difference in radon concentration was observed between the two sampling methods, which highlights the importance of temporal variability of indoor pollutants. High radon values were correlated with the lack of adequate ventilation, an aspect underlined by high CO2 concentrations. Additionally, the study finds that indoor air pollutants can be attributed to three main factors: the physical characteristics and usage of the indoor environment (volatile organic compounds and carbonyl compounds), the properties of the sub-slab soil (radon) and the occupational factor (CO2). Each factor should be treated separately when indoor air quality management is addressed.

Comparative study between active and passive techniques for measuring radon concentrations in groundwater of Al-Najaf city, Iraq

In this work, Radon (222Rn) concentrations in groundwater, were measured Al- Najaf city, using the RAD-7 radon monitoring system of Durridge company the USA and CR-39 detector. Each location was determined on the map by using GIS program. The annual effective dose for all samples of groundwater was calculated by equations depending on the UNSCEAR organization.It is found that the average of the radon concentrations in groundwater samples using RAD-7 were varied from (174.5 ± 24.242 Bq/m3) to (2000.5 ± 165.8 Bq/m3), but using CR-39 varied from (179.101 ± 55.286 Bq/m3) to (557.772 ± 166.546 Bq/m3). Also, the results showed that annual effective dose in all groundwater samples was lower than the permissible limit of (1 mSv) recommended by ICRP 1993. The correlation of radon concentrations in present study using active technique (RAD-7) and passive technique (CR-39) is very good significant showing a linear correlation coefficient of (0.80). Certainly, this study was conducted to provide a health-oriented radon assessment of Al-Najaf cities, address long term management goals, especially from the environmental point of view. The results provide a framework for future studies that should include a large and broader survey of radon concentration in Iraq.

Radon Activity in Volcanic Gases of Mt. Etna by Passive Dosimetry

AbstractRadon (222Rn) activity in air was measured for about 6 months at the summit of Mt. Etna Central Crater (Sicily) by integrative radon dosimetry at two different heights above ground level (5 cm and 1 m). This technique for air radon monitoring proved operational in the harsh volcanic environment of Mt. Etna summit with a 94% recovery rate of dosimeters. In the southeast sector exposed to the main gas plume, mean radon activity in free air (height 1 m) is significantly higher than the local background and the ground level activity (height 5 cm). The results strongly suggest that the plume is enriched in radon by ≈550 Bq/m3, which has never been evidenced before. Radon activities also reflect soil degassing occurring in the proximity of the crater, with increased ground level activities in zones of enhanced soil fracturing and degassing. Radon measurements also revealed a hot spot in front of the Voragine vent with extraordinary high levels of air activities (26 kBq/m3 at ground level and 8 kBq/m3 in free air). The temporal variation of radon activity was investigated by replacing a few stations half way through the exposure period. The only significant increase was associated with the site located under the main gas plume and correlated with eruptive unrest within the crater. Finally, air radon levels higher than the recommended threshold of 300 Bq/m3 were detected in several zones on the rim and could generate a nonnegligible radiologic dose for workers on the volcano.

Monitoring soil radon during the 2016\u20132017 central Italy sequence in light of seismicity

The radioactive nature of radon makes it a powerful tracer for fluid movements in the crust, and a potentially effective marker to study processes connected with earthquakes preparatory phase. To explore the feasibility of using soil radon variations as earthquakes precursor, we analyse the radon concentration data recorded by two stations located close to the epicentre of the strongest mainshock (Mw 6.5 on October 30, 2016) of the seismic sequence which affected central Italy from August 2016. The two stations CTTR and NRCA operate in the framework of the permanent Italian Radon monitoring Network and recorded almost continuously since 2012 and 2016, respectively, the latter being installed just after the first mainshock of the sequence (Mw 6.0 on August 24, 2016). An increase of radon emanation is clearly visible about 2 weeks before the Mw 6.5 event on both the time series, more pronounced on NRCA, nearer to the epicentre, suggesting the possibility of a direct association with the earthquake occurrence. An independently developed detection algorithm aimed at highlighting the connections between radon emission variations and major earthquakes occurrence succeeds in forecasting the Mw 6.5 mainshock on NRCA time series. The resulting time advance of the alarm is consistent with that obtained using a Bayesian approach to compute the a posteriori probability of multiple change points on the radon time series of NRCA. Moreover, it is in agreement with the delay time which maximizes the correlation between radon and seismic anomalies. Applying the detection algorithm to CTTR time series returns alarms for both the Mw 6.0 event, with epicentre closer to this station, and the stronger Mw 6.5 event, but with a higher number of false detections. Finally, we found that a preliminary correction of the bias introduced by variations of meteorological parameters does not affect our main finding of an increase in radon concentration before the major mainshocks. Our study confirms that, although much work is still needed, a monitoring approach based on a permanent dense network is crucial for making radon time series analysis an effective complement to traditional seismological tools.

Cost-effectiveness of radon remediation programmes in the UK in the 2020s

Radon, a gaseous radioactive decay product of naturally-occurring uranium is widely distributed in the environment in rocks and soils and, in certain circumstances, can accumulate in the built environment. Initial studies confirmed a direct link between exposure to both radon gas and its short-lived radioactive progeny, and increased lung-cancer incidence, and demonstrated that radon levels in domestic housing can be sufficiently high to expose occupants to increased risk of lung-cancer. Subsequent studies worldwide have shown that it is cost-effective to detect and reduce domestic radon levels in order to reduce this risk.Recent advances in the early detection of lung-cancer, coupled with the development of improved treatment procedures, have progressively improved survival from the disease, with the numbers surviving at 5 years doubling over recent years, during which period the real costs of lung cancer treatment have risen by around 30%. In the meantime, however, in addition to radon and tobacco-smoke, other airborne pollutants have been identified as risk-factors for lung-cancer. This paper reviews both these actual developments and anticipated future trends, and concludes that since these advances in diagnosis and treatment of lung-cancer have had only a modest effect on cost-effectiveness, it is still important to conduct radon monitoring and remediation programmes. While the general increase in life-expectancy improves the cost-effectiveness of radon remediation programmes significantly, reducing tobacco-smoking incidence reduces that cost-effectiveness but with the overall benefit of reducing radon-related lung-cancers. The challenge remains of encouraging affected householders to remediate their homes to reduce radon levels.

Optimization of dissolved Radon monitoring in groundwater to contribute to the evaluation of the seismic activity: an experience in central-southern Italy

Anomalies in Radon (222Rn) concentrations prior to earthquakes have been widely documented in seismogenic areas worldwide, but questions about their predictability remain largely unanswered. Even if it is not universally accepted, the analysis of the high-resolution time series of Rn (222Rn) concentrations in groundwater, air and soil has been proposed as a suitable method to identify seismic precursors. This study, which is aimed at identifying potential gas-geochemical precursors to nearby earthquakes, analyses groundwater Rn concentrations, which were continuously measured between April 2017 and December 2019. We conducted a detailed time series analysis of dissolved Rn in two springs emerging along two active fault zones in the inner sector of the central-southern Apennines (i.e. the Matese and Morrone fault zones) in Italy. We used a simple statistical method to identify seismic precursor anomalies in Rn concentrations. Anomalies are commonly assumed as values exceeding ± 2σ. Furthermore, we calculated the strain radius (for which a gas-geochemical precursor was expected) and the epicentral distance (from both our monitoring stations) of each seismic event of Mw ≥ 3.5 that occurred in the monitoring area. Results from our ongoing research are promising and show significant correlations between seismic signals and Rn concentrations. However, longer time series data that include more energetic earthquakes are needed to shed light on the behaviour of this gas in relation to crustal deformation processes.

Long‐Term Monitoring and Characterization of Soil Radon Emission in a Seismically Active Area

AbstractRadon (222Rn) is a radioactive gas, which originates everywhere in rocks of Earth's crust through a process of natural decay of other radioactive elements. The monitoring of soil radon can be useful to address a multitude of geological and environmental issues. However, some difficulties arise when trying to use radon as earthquake precursor because the earthquake‐related anomaly cannot be easily and univocally discriminated from other anomalies of different origin. To explore the relationship between soil radon emission and seismicity, a local network is operating in southeastern Sicily (Italy). Its peculiarities are the uniform geological condition of the monitoring sites and the long data record with simultaneous measures of radon and the main climate variables. In this paper, we applied continuous wavelet transformation to a ≈ 3.5 years long soil radon time series to detect periodic variations. Results indicate the occurrence of cycles at annual, semiannual, and monthly periodicity, which are ascribable to the effects of the climatic‐environmental parameters. The periodic components have been modeled and the signal conveniently filtered. We show as the characterization of the long‐term behavior of radon signals is essential to recognize anomalies in radon emission, which can be related to geological/environmental phenomena. The methodology proposed in this work provides a reliable characterization of the radon time series and can be applied at various spatial/temporal scales, depending on the scientific objectives to be achieved. This approach can also represent the base for further analysis like the investigation of the modulation between the periodic components and short‐term forecasts.

Continuous radon monitoring during seven years of volcanic unrest at Campi Flegrei caldera (Italy)

This is a seven-year study (1/7/2011-31/12/2017) of radon monitoring at two sites of Campi Flegrei caldera (Neaples, Southern Italy) that in the last 70 years experienced repeated phases of volcanic unrest. The sites are equipped with devices for radon detection, based on the spectrometry analysis of the α-particles of radon daughters. A hybrid method, as combination of three known methods, is applied for the identification of residuals (anomalies) and trends of the time series of Radon. The results are compared with the following indicators of current caldera unrest: the tremor caused by the major fumarolic vent registered by a seismic station; the cumulative of background seismicity; the maximum vertical deformation acquired by GPS networks during the current phase of uplift; the temperature-pressure of the hydrothermal system estimated based on gas geo-indicators. The comparisons show strong correlation among independent signals and suggest that the extension of the area affected by current Campi Flegrei crisis is larger than the area of seismicity and of intense hydrothermal activity from which the radon stations are 1–4 km away. These results represent an absolute novelty in the study of a such calderic area and mark a significant step forward in the use and interpretation of the radon signal.

Development of a high-sensitivity radon monitor for a radon calibration system at KRISS

A radon calibration system is being developed with a high-sensitivity radon detector using electrostatic collection and an alpha spectrometer. Eight radon cells, each with a volume of 1.354 L, are integrated to achieve a high-sensitivity radon monitor with a total detector volume of 10.832 L. The sensitivity is estimated to be 35.6 ± 0.2 (36.8 ± 0.2) times higher relative to the RAD7 radon monitor for the detection of 218Po (214Po), respectively.

Using a scale model room to assess the contribution of building material of volcanic origin to indoor radon

Abstract In the frame of Radon rEal time monitoring System and Proactive Indoor Remediation (RESPIRE), a LIFE 2016 project funded by the European Commission, the contribution of building materials of volcanic origin to indoor radon concentration was investigated. First, total gamma radiation and related outdoor dose rates of geological materials in the Caprarola area (Central Italy) were measured to define main sources of radiation. Second, 222Rn and 220Rn exhalation rates of these rocks used as building materials were measured using an accumulation chamber connected in a closed loop with a RAD7 radon monitor. Among others, the very porous “Tufo di Gallese” ignimbrite provided the highest values. This material was then used to construct a scale model room of 62 cm × 50 cm × 35 cm (inner length × width × height, respectively) to assess experimental radon and thoron activity concentration at equilibrium and study the effects of climatic conditions and different coatings on radon levels. A first test was carried out at ambient temperature to determine experimental 222Rn and 220Rn equilibrium activities in the model room, not covered with plaster or other coating materials. Experimental 222Rn equilibrium was recorded in just two days demonstrating that the room “breaths”, exchanging air with the outdoor environment. This determines a dilution of indoor radon concentration. Other experiments showed that inner covers (such as plasterboard and different kinds of paints) partially influence 222Rn but entirely cut the short-lived 220Rn. Finally, decreases in ambient temperature reduce radon exhalation from building material and, in turn, indoor activity concentration.

Intercomparison study of atmospheric <sup>222</sup>Rn and <sup>222</sup>Rn progeny monitors

Abstract. The use of the noble gas radon (222Rn) as a tracer for different research studies, for example observation-based estimation of greenhouse gas (GHG) fluxes, has led to the need of high-quality 222Rn activity concentration observations with high spatial and temporal resolution. So far a robust metrology chain for these measurements is not yet available. A portable direct atmospheric radon monitor (ARMON), based on electrostatic collection of 218Po, is now running at Spanish stations. This monitor has not yet been compared with other 222Rn and 222Rn progeny monitors commonly used at atmospheric stations. A 3-month intercomparison campaign of atmospheric 222Rn and 222Rn progeny monitors based on different measurement techniques was realized during the fall and winter of 2016–2017 to evaluate (i) calibration and correction factors between monitors necessary to harmonize the atmospheric radon observations and (ii) the dependence of each monitor's response in relation to the sampling height and meteorological and atmospheric aerosol conditions. Results of this study have shown the following. (i) All monitors were able to reproduce the atmospheric radon variability on a daily basis. (ii) Linear regression fits between the monitors exhibited slopes, representing the correction factors, between 0.62 and 1.17 and offsets ranging between −0.85 and −0.23 Bq m−3 when sampling 2 m above ground level (a.g.l.). Corresponding results at 100 m a.g.l. exhibited slopes of 0.94 and 1.03 with offsets of −0.13 and 0.01 Bq m−3, respectively. (iii) No influence of atmospheric temperature and relative humidity on monitor responses was observed for unsaturated conditions at 100 m a.g.l., whereas slight influences (order of 10−2) of ambient temperature were observed at 2 m a.g.l. (iv) Changes in the ratio between 222Rn progeny and 222Rn monitor responses were observed under very low atmospheric aerosol concentrations. Results also show that the new ARMON could be useful at atmospheric radon monitoring stations with space restrictions or as a mobile reference instrument to calibrate in situ 222Rn progeny monitors and fixed radon monitors. In the near future a long-term comparison study between ARMON, HRM, and ANSTO monitors would be useful to better evaluate (i) the uncertainties of radon measurements in the range of a few hundred millibecquerels per cubic meter to a few becquerels per cubic meter and (ii) the response time correction of the ANSTO monitor for representing fast changes in the ambient radon concentrations.

Radon Concentration in Chandigarh, India using LR-115 detector

Radon monitoring has become a global phenomenon due to its health hazards. Mostly LR-115 detectors are being used to obtain the concentration levels of radon/thoron and their daughters. Studies have reported of the total exposure of radon to human being indor radon accounts for more than 50%. So study of radon in different region gains significance. In this paper we have studied the indoor radon concentration in various localities of Chandigarh a union territory and capital town of Punjab, India. We also compared the result with all India radon concentration level and WHO/UNSCEAR effective dose limit.

Investigation of diffusive transport of radon through bricks

Radon and their progeny are known indoor lung carcinogens with major sources from the subsoil followed by building materials. The present work was aimed to study the radon permeability of main building materials which is a dominant process for radon entry to indoor environment under normal room conditions. For this purpose, the radon diffusion coefficient and permeability for widely used bricks in the southern coastal region of India were measured with a specially designed twin-chamber experimental set up: a strong source of radon in one chamber and radon and progeny accumulation arrangement in another chamber. Brick samples (with varying thicknesses, firing time and porosity) collected from local kilns were sandwiched between the chambers allowing the radon gas to diffuse through them to get developed in the second chamber. An alpha scintillation based radon monitoring device was connected with both chambers for online radon measurement. Moderately- and lightly-fired bricks show relatively greater permeability than the highly-fired ones, but all the studied bricks are found to be in the radon-tight category. Measured data of radon diffusion coefficient (0.29–0.40) × 10−6 m2s-1 with a mean of (0.35 ± 0.05) × 10−6 m2s-1 and diffusion length (0.37–0.44 m) with a mean of 0.41 ± 0.03 m show a general agreement with the available results in the literature, albeit differing with an earlier study by Chauhan et al. (2008) due to the variation of the sample matrix. Measured data may help the building construction agency to choose a suitable brick to ensure a safer indoor environment for the dwellers.

Assessment of Uranium in Urine Samples of Primary School Students

The environmental monitoring of radon in the children urine has been carried out by using solid state nuclear track detector CR-39. This study has been undertaken for the purpose of health risk assessments. The concentration of uranium values excreted with the boy's urine samples ranged from 0.203 Bq.L-1 (1.246 ng/L) and 2.201 Bq.L-1 (13.486 ng/L) with an average value of 0.698 Bq.L-1 (4.007 ng/L). While the concentration of uranium values excreted with the girl's urine samples ranged between 0.290 Bq.L-1 (1.777 ng/L) and 0.675 Bq.L-1 (4.135 ng/L), with an average value of 0.474 Bq.L-1 (2.901 ng/L). The amount of uranium deposited in the kidneys, according to ICRP's biokinetic model, and the annual radiation dose were also calculated. All values of the study samples were within the normal range and do not indicate any health hazard.

Radon monitoring on the territory of Northern Tajikistan

The article presents the results of radon monitoring on the territory of Northern Tajikistan. Analysis of the results of the monitoring shows that at present, relatively high values of radon concentration in the atmospheric air are found in the areas where uranium tailings are located, primarily in the city of Istiklol and the Dehmoy tailings dam. This is primarily due to the lack of protective coatings on the surface of the tail material, which turns this area, in fact, into radon-prone areas of technogenic origin. In different parts of the Dehmoy tailings dam, the radon concentration in the atmospheric air varies between 200 and 1000 Bq/m3, and the radon flux density from the surface reaches 65,000 mBq/(m2∙s). On the territory of tailings dam in the city of Istiklol, the value of radon concentration in the atmospheric air is in the range of 44–195 Bq/m3. At the same time, it was found that the radon potential of the tailings dams, where the surface has a protective coating, is much lower. For example, the radon flux density from the surface of the Gafurov tailings dam, where surface is covered with loess-like loams up to 2.5–3.0 m thick, does not exceed 100 mBq/(m2∙s), with average values of 40-60 mBq/(m2∙s); the radon concentration in the atmospheric air is about 55 Bq/m3. Despite the intense exhalation of radon from the surface of some tailings dams, their territory is not currently a residential zone and, accordingly, does not affect the radon situation in buildings located in the settlements nearby. In the cities of Khujand, Buston, Gafurov, Istiklol and the village of Adrasman, the average values of indoor radon concentration do not exceed maximum permissible levels. It is recommended to conduct a full rehabilitation of uranium legacy sites, primarily uranium tailings dams in the city of Istiklol and Dehmoy tailings dam, for the improvement of the radon situation in Northern Tajikistan with consideration for possible expansion of the settlements.

Theoretical and experimental study of the LR-115 detector response in a non-commercial radon monitor

B.trαcks, a simulation program for SSNTD's sensitivity, has been developed to study the response of LR-115 (cellulose nitrate) and CR-39 (poly allyl glycol carbonate) nuclear track detectors. Detectors are located inside detector holders and are used for radon measurements. The program incorporates a variety of special features gathered together to achieve good agreement between theoretical approach and experimental results. The input parameters to study the detector response are radon exposure, geometry and dimensions of a detector holder (it can be cylindrical, conical or semi-spherical), entrance type for radon gas, detector type, and V function (four different functions were selected from literature). The output results are detector response and radon progeny distribution onto internal chamber walls. In this article, the response of the LR-115, which is placed inside a non-commercial-conductive radon monitor based on diffusion chambers called G2, was theoretically and experimentally studied. The common Monte Carlo simulation procedure and an alternative approach that replicates how monitors are exposed to different radon exposures were used as theoretical approaches. Experimental methodology was conducted in a radon test chamber from Italy (MI.AM s.r.l.). Comparison results of both theoretical and experimental methodology are presented and discussed. One of the major results, among others, shows that the monitor material (conductive or non-conductive) does not influence the LR-115 response.

INCORPORATING KENAF AND OIL PALM NANOCELLULOSE IN BUILDING MATERIALS FOR INDOOR RADON GAS EMANATION REDUCTION.

This study aims to reduce radon gas emanations in the indoor environment by incorporating kenaf and oil palm nanocellulose that act as nano-fillers into building materials. Fabrication of composite brick was carried out according to the MS and ASTM standards. In this research, 40, 80, 120, 160 and 200 ml of nanocellulose were used to replace the usage of sand, stone and cement materials, respectively. Kenaf and oil palm nanocellulose were utilised to reduce the internal and surface porosity as well as to replace the radon resources (stone), which indirectly reduced radon gas emanation. Radon gas emanated from each composite brick was measured within 10 consecutive days in an airtight prototype Perspex room using Radon Monitor Sentinel 1030. A compression test was also carried out to investigate the physical strength of the fabricated composite bricks. The results showed that 40 ml of kenaf and oil palm nanocellulose was the optimum amount in reducing the radon concentration, where the radon readings were 1.4 and 0.93 pCi per l, respectively. Meanwhile, the brick with no nanocellulose exhibited the highest radon reading of 3.77 pCi per l. Moreover, the Young modulus for the composite brick of both kenaf and oil palm nanocellulose was 28.92 and 27.8 N per mm2 compared to the control brick, which was 27 N per mm2. The results proved that radon gas emanations were reduced by 62.86% for kenaf and 75.3% for oil palm by incorporating the organic nanocellulose, which has high potential towards a healthy indoor environment.

Changes in groundwater radon concentrations caused by the 2016 Kumamoto earthquake

This study examined radon concentrations in springs in Kumamoto and Aso regions following the 2016 Kumamoto earthquake, in addition to monitoring springs near the Futagawa-Hinagu fault zone for more than two years following the earthquake to investigate the relationship between crustal deformation and the radon concentration variation. We compared these radon concentrations with those obtained prior to the earthquake. The springs that showed elevated radon concentrations were located within the compressive strain quadrant of the earthquake. The post-seismic concentration variations of the monitored springs can be explained by rock porosity changes. These results suggest that the radon concentration in spring water is affected by porosity changes caused by stress changes derived from earthquake deformation and subsequent post-seismic relaxation. Our results are consistent with the previously inferred permeability enhancement model. Mass conservation calculations for radon release yielded porosity changes ranging from 30% to 70% for some aquifer systems. This study explores the possibility of radon monitoring as a tool to investigate not only seismic precursors but also post-seismic crustal deformation and aquifer property changes due to large earthquakes on a regional scale.