The transport mechanisms of 222Rn in soil at Tateishi as an anomaly spot in Japan

Assessment of soil-gas radon concentration over lithologies: a case study from district Karak, Khyber Pakhtunkhwa, Pakistan

The current study is aimed to determine the variation of soil-gas radon concentrations over different rock formations representing diverse lithologies in the district of Karak, Khyber Pakhtunkhwa, Pakistan. The stratigraphic units were grouped on the basis of lithological contents into four categories, i.e., limestone, evaporites, claystone/mudstone, and sandstone. The highest average soil-gas ²²²Rn concentration (544 Bq/L) was found in the uranium-bearing Dhok Pathan Formation of the Pliocene age, while the lowest radon levels (0.15 Bq/L) were observed in the salt-bearing strata of Bahadurkhel Salt of Eocene age showing the non-uraniferous nature of the salt. High radon potential associated with the Dhok Pathan Formation is likely to be related to the high degree of uranium mineralization which is contributing to the elevated soil-gas radon levels. The study revealed that the soil-gas radon concentration in all lithologies is varying in the order of RnSandstone > RnLimestone > RnClaystone/Mudstone > RnEvaporites with the highest radon levels in the sandstone unit of uranium-bearing Dhok Pathan Formation. High fluctuations of soil-gas radon levels observed in this study evidently show that lithology and uranium mineralization have strong control over the ²²²Rn concentrations.

Evaluation of soil-gas radon concentrations from different geological units with varying strata in a crystalline basement complex of southwestern Nigeria

The aim of this study is to determine the variation of soil-gas radon concentrations from different rock formations in Ogbomoso, southwestern Nigeria. The radon concentrations at different five geological domains in Ogbomoso are determined with respect to depth. The measurements varied from the surface (0 cm) to 100 cm depth, with an interval of 20 cm. At all the geological domains (Porphyroclastic, Granite, Quartzite, Migmatite and Banded gneiss), radon has its minimum emission over migmatite at 0 cm, while its maximum emissions occured over granite and banded gneiss at 80 cm. The overall soil-gas radon concentrations in Ogbomoso varied from 0.06 to 26.5 kBq/m³, which is within the natural limit of 0.4 to 40 kBq/m³ based on the International Commission on Radiological Protection's recommendation. An F-ratio of 6.989 and a p-value of 0.001 were obtained for the first inferential hypothesis, while an F-ratio of 2.489 and a p-value of 0.076 were obtained for the second inferential hypothesis using ANOVA test. The post hoc (using Tukey HSD and Duncan) tests revealed that at 60 + cm, depth controls the level of radon concentrations being emanated from the subsurface. The pollution index in Ogbomoso is of level 1 at 80 cm and level 0 (safe limit) at other depths. In conclusion, the soil-gas radon emission depends on the local geology and lithological sequences (depths). Cracks that could act as passage for indoor radon at the floors of the buildings around the polluted zones should be avoided in order to have a sustainable city.

Measurements of radon concentrations in waters and soil gas of Zonguldak, Turkey

The radon concentrations in soil-gas and water samples (in the form of springs, catchment, tap, thermal) used as drinking water or thermal were measured using a professional radon monitor AlphaGUARD PQ 2000PRO. The measured radon concentrations in water samples ranged from 0.32 to 88.22 Bq l(-1). Most of radon levels in potable water samples are below the maximum contaminant level of 11 Bq l(-1) recommended by the US Environmental Protection Agency. The calculated annual effective doses due to radon intake through water consumption varied from 0.07 to 18.53 µSv y(-1). The radon concentrations in soil gas varied from 295.67 to 70 852.92 Bq m(-3). The radon level in soil gas was found to be higher in the area close to the formation boundary thrust and faults. No correlation was observed between radon concentrations in groundwater and soil gas. Also, no significant correlation was observed between soil-gas radon and temperature, pressure and humidity. The emanation of radon from groundwater and soil gas is controlled by the geological formation and by the tectonic structure of the area.

Estimation of annual effective dose from indoor radon/thoron concentrations and measurement of radon concentrations in soil

Radon short-lived decay products generated from the earth is one of the serious indoor air and soil pollutants. The RAD-7 Electronic Radon Detector with a special accessory is used for the purpose of measurement. The radon and thoron concentrations in the houses of the study area are found to vary from 35±0.5 to 315.2±5.35 Bq m(-3) and 66.1±2.3 to 1710±139.36 Bq m(-3) with the average values of 98.65±1.9 and 388.19±11 Bq m(-3), respectively. From indoor air, the total annual effective dose is calculated and it varies from 0.88 to 7.94 mSv y(-1). The preliminary investigation shows that the thoron concentration is higher than the radon concentration in the houses of the study area. In general, the values of the indoor air are within the recommended action level of the International Commission on Radiological Protection, 2009.

Systematic survey of natural radioactivity of soil in Slovenia

Soil samples, from 70 points uniformly distributed over entire Slovenia, were analysed for (40)K, (232)Th and (226)Ra using gamma spectrometry, and for (234)U and (238)U using alpha spectrometry. The following ranges and averages of activity concentrations (Bq kg(-1)) were obtained: 98-2600 and 800 ± 520 for (40)K, 9-170 and 77 ± 33 for (232)Th, 12-270 and 63 ± 44 for (226)Ra, 12-84 and 34 ± 19 for (234)U, and 11-90 and 34 ± 19 for (238)U. With respect to lithology, the highest average values for (40)K and (232)Th were found at clastic sediments containing clay and for (226)Ra on carbonate rocks. Based on the measured activity concentrations, terrestrial gamma dose rates were calculated. The total dose rate ranged from 15 to 260 nGy h(-1), with arithmetic mean of 110 ± 49 nGy h(-1), being the highest over carbonates.

In situ measurements of radon levels in water and soil and exhalation rate in areas of Malwa belt of Punjab (India)

Radon concentration levels in water and soil gas from 36 locations pertaining to some areas of Malwa region of Punjab have been measured on an in situ basis using a continuous active radon detector (AlphaGuard, Model - PQ 2000 PRO, Genitron instruments, Germany). Exhalation rate measurements have also been carried out at these places, using a closed-circuit technique. The radon concentrations in soil and water varied from 1.9 to 16.4 kBq m(-3) and 5.01 to 11.6 kBq m(-3), respectively. The exhalation rate (E (Rn)) ranged between 7.48 and 35.88 mBq m(-2) s(-1) with an average value of 18.17 mBq m(-2) s(-1). Annual dose rates have been calculated for water radon concentrations. The minimum to maximum values of dose rates were found to be 13.42-31.08 μSv y(-1). The recorded values of radon concentration in water are within the safe limit of 11 Bq l(-1) recommended by the US Environment Protection Agency [National Research Council, Risk Assessment of Radon in Drinking Water (Academy Press, Washington, DC, USA, 1999)]. All measurements were made in similar climatic and environmental conditions to ensure minimal variations in meteorological parameters. An intermediate correlation coefficient (0.5) was observed between radon exhalation rates and soil gas values.

Soil gas radon analysis in some areas of Northern Punjab, India

The radon concentration levels in soil samples from 39 locations of Northern Punjab are measured using AlphaGUARD (PQ 2000 PRO Model) of Genitron instruments, Germany. The radon concentration in soil varies from 0.3 to 35.8 kBq/l. The minimum value of radon is observed in Talwandi Choudhrian and is maximum for Nushera Dhala. The soil gas radon is correlated with soil temperature, pressure, and humidity to observe the effect of these parameters on radon release. The soil gas radon values in the study area are compared with that obtained in groundwater. The results are also compared with the available radon data for other parts of Punjab and Himachal Pradesh.

Measurement of soil gas radon and its correlation with indoor radon around some areas of Upper Siwaliks, India

Radon is a radioactive gas which makes the primary contribution to the natural radiation to which people are exposed. For that reason, great importance is attributed to the determination of radon concentration levels in water, indoor air and soil gas and outdoors. In this paper, measurements of radon concentration in soil gas have been carried out around some areas of the Upper Siwaliks of the Kala Amb, Nahan and Morni Hills, India, using a portable AlphaGUARD PQ 2000 device into which the soil gas is drawn using active pumping. The soil gas radon concentration around the Upper Siwaliks was found to vary from 11.5 +/- 0.9 to 78.47 +/- 3.1 kBq m(-3). The annual average indoor radon concentration in the study area was measured in the range from 71.7 +/- 21.0 to 421.7 +/- 33.6 Bq m( - 3) using LR-115 type II cellulose nitrate films in the bare mode. The values of soil gas radon concentration in the study area were compared with those from the adjoining low-radioactive areas of Punjab. Since the soil or bedrock beneath a building is one of the sources of radon gas in the indoor air, an effort has been made to find a possible correlation between soil gas radon with the indoor radon. A satisfactory positive correlation has been observed between soil gas radon and indoor radon in the study area.

Simultaneous measurements of radon and thoron exhalation rates and comparison with values calculated by UNSCEAR equation

We simultaneously measured radon and thoron exhalation rates in areas of weathered acid rocks in Japan to investigate the relationship between them and between measured and calculated radon exhalation rates. To calculate the radon exhalation rate, we used an equation proposed by UNSCEAR. Our analysis showed that both the radon and thoron exhalation rates measured at one location in a natural environment fluctuated widely, even within one day. We found a strong correlation between the radon and thoron exhalation rates. The measured radon exhalation rates tended to be lower than the calculated values: the mean ratio of the measured exhalation rate to the calculated rate was 0.65. We concluded that the UNSCEAR equation is applicable under a controlled environment (temperature, humidity, etc.), but not where there are artificial underground structures that may influence the transportation of radon in soil.

Space charge effect on the electrostatic collection of thoron decay products

Investigations on electrostatic collection of thoron decay products as a function of field strength in a special source-electrode arrangement have been performed. Yields of the decay products vs. field strength were measured by solid state silicon and CR-39 track-etched detectors. Results show a significant space charge effect on the yield of collected products if an insulator is placed between the electrodes. The intensities of the collected thoron daughters are influenced strongly by the air stream present in the cell.