The FIRST large-scale mapping of radon concentration in soil gas and water in Romania

Radon measurement and age-independent effective dose attributed to ingestion of bottled water in Iran: sensitivity analysis

A comprehensive study was made to measure the radon concentration in bottled water available in Iran market. The 222Rn concentration in 70 bottled water samples were measured by the sniffing mode technique and RTM 1688-2 (SARAD, Germany) in immediate sampling time and 3 months later for determination of radon decay. The measured radon concentration ranged from 0.003 to 0.618 Bq L-1 in bottled water samples, which were much lower than the recommended value for radon in drinking water by WHO (100 Bq L-1) and United states environmental protection agency (USEPA) (11.1 Bq L-1). The annual effective dose of 222Rn due to ingestion bottled water was also evaluated in this research. The mean annual effective dose due to ingestion of radon in bottled water for adults, children, and infants were estimated to vary from 5.30 × 10-4 mSv-1, 4.90 × 10-4 mSv-1, and 2.15 × 10-4 mSv-1, respectively. Overall, this study indicated that the Iranian people receive no significant radiological risk due to exposure to radon concentration in bottled water brands common consumed in Iranian market.

Soil gas radon and soil permeability assessment: Mapping radon risk areas in Perak State, Malaysia

In this study geogenic radon potential (GRP) mapping was carried out on the bases of field radon in soil gas concentration and soil gas permeability measurements by considering the corresponding geological formations. The spatial pattern of soil gas radon concentration, soil permeability, and GRP and the relationship between geological formations and these parameters was studied by performing detailed spatial analysis. The radon activity concentration in soil gas ranged from 0.11 to 434.5 kBq m⁻³ with a mean of 18.96 kBq m⁻³, and a standard deviation was 55.38 kBq m⁻³. The soil gas permeability ranged from 5.2×10⁻¹⁴ to 5.2×10⁻¹² m², with a mean of 5.65×10⁻¹³ m². The GRP values were computed from the ²²²Rn activity concentration and soil gas permeability data. The range of GRP values was from 0.04 to 154.08. Locations on igneous granite rock geology were characterized by higher soil radon gas activity and higher GRP, making them radon-prone areas according to international standards. The other study locations fall between the low to medium risk, except for areas with high soil permeability, which are not internationally classified as radon prone. A GRP map was created displaying radon-prone areas for the study location using Kriging/Cokriging, based on in situ and predicted measured values. The GRP map assists in human health risk assessment and risk reduction since it indicates the potential of the source of radon and can serve as a vital tool for radon combat planning.

Comprehensive survey on radon mitigation and indoor air quality in energy efficient buildings from Romania

Over the last 10 years applied scientific research has been carried out in Romania to tacked the residential radon issues. The increased interest to reduce the carbon footprint of buildings has lead to the implementation and use of new architectural solutions aimed to save energy in houses and other buildings. As a consequence, the degree of retrofit in existing buildings and energy efficiency of new buildings promoted the need to not only mitigate indoor radon, but improve indoor air quality overall. The present study found that the while the best performance in radon reduction was confirmed to be based on sub-slab depressurization (61% - 95% reduction), centralized and decentralized mechanical supply and exhaust ventilation with heat recovery yielded a good efficiency in overall improvement of indoor air quality (CO₂, VOC, RH, temperature). The outcome of our research, as well as future perspectives, take into account the recommended harmonization of energy efficiency programs with those of public health by finding and applying the best technologies in compliance with energy saving and indoor environmental quality.

Radon-222: environmental behavior and impact to (human and non-human) biota

As an inert radioactive gas, ²²²Rn could be easily transported to the atmosphere via emanation, migration, or exhalation. Research measurements pointed out that ²²²Rn activity concentration changes during the winter and summer months, as well as during wet and dry season periods. Changes in radon concentration can affect the atmospheric electric field. At the boundary layer near the ground, short-lived daughters of ²²²Rn can be used as natural tracers in the atmosphere. In this work, factors controlling ²²²Rn pathways in the environment and its levels in soil gas and outdoor air are summarized. ²²²Rn has a short half-life of 3.82 days, but the dose rate due to radon and its radioactive progeny could be significant to the living beings. Epidemiological studies on humans pointed out that up to 14% of lung cancers are induced by exposure to low and moderate concentrations of radon. Animals that breed in ground holes have been exposed to the higher doses due to radiation present in soil air. During the years, different dose-effect models are developed for risk assessment on human and non-human biota. In this work are reviewed research results of ²²²Rn exposure of human and non-human biota.

A case study on the correlation between radon and multiple geophysicochemical properties of soils in G island, Korea, and effects on the bacterial metabolic behaviors

This study was conducted to assess the natural radiation intensity of radon observed from 'G' islands and its effects against Bacillus pumilus, predominantly found throughout the field survey. The physicochemical properties and microbial characteristics were simultaneously investigated and compared. From these studies, it was confirmed that the areal distribution of radon concentration varied from 920 Bq/m³ to 3367 Bq/m³ depending on the soil depth, lithology, or geophysicochemical properties (including pH, moisture content, and grain size) inherently subject to each location. Particularly, the slightly acidic (pH < 6) and low-fertility soil with a higher level of radon concentration exceeding 3000 Bq/m³ had a considerably low level of bacterial density. In contrast, the fertile soil of a relatively middle level of radon radioactivity revealed a much larger bacterial community density, dominated by Bacillus spp., Pseudomonas sp., Paenarthrobacter sp., and Microbacterium sp. Furthermore, the monitored metabolic activity and growth of Bacillus pumilus against the various radon exposure conditions clearly indicated that radon could be considered as the potential ecological risk to natural environmental habitats of microbial soil biota.

The path from geology to indoor radon

It is generally accepted that radon emission is strongly influenced by the geological characteristics of the bedrock. However, transport in-soil and entry paths indoors are defined by other factors such as permeability, building and architectural features, ventilation, occupation patterns, etc. The purpose of this paper is to analyze the contribution of each parameter, from natural to man-made, on the radon accumulation indoors and to assess potential patterns, based on 100 case studies in Romania. The study pointed out that the geological foundation can provide a reasonable explanation for the majority of the values recorded in both soil and indoor air. Results also showed that older houses, built with earth-based materials, are highly permeable to soil radon. Energy-efficient houses, on the other hand, have a tendency to disregard the radon potential of the geological foundation, causing a higher predisposition to radon accumulation indoors and decreasing the general indoor air quality.

VARIATION OF INDOOR RADON CONCENTRATION WITHIN A RESIDENTIAL COMPLEX

A recent challenge in research dedicated to residential exposure to radon comes from the growing number of houses retrofitted to reduce energy consumption. Efficiently insulated buildings and modern architectural solutions can lead to the accumulation of high levels of indoor pollutants. A systematic analysis was conducted in a residential complex (consisting of six houses) in order to assess the annual radon concentration and to evaluate the intensity of the relationships with various factors, such as the indoor-outdoor temperature differences, wind speed and wind direction. Three types of occupational behaviour, influencing the ventilation rate of the dwellings and, implicitly, the indoor radon activity concentration were observed. By calculating the partial correlation coefficient between the radon concentration and the wind direction, with the wind speed as the control variable, for all six houses the correlation coefficient presents negative values.

A laboratory method for concurrently determining diffusion migration parameters and water saturation effects of thoron in uranium tailings

Environmental humidity has a significanteffect on changes in free ²²⁰Rn (thoron) production rate and effective diffusion coefficient of ²²⁰Rn in uranium tailings. To understand such changes, a closed cavity containing porous ²²⁰Rn media with finite thickness was studied. Based on the ²²⁰Rn diffusion migration theory in porous media with finite thickness, a model for calculating the uniform ²²⁰Rn activity concentration in a closed container with porous media of finite thickness was established. A laboratory method for concurrently determining free ²²⁰Rn production rate and effective diffusion coefficient of ²²⁰Rn was proposed and a corresponding experimental setup was made. With samples taken from a uranium tailing impoundment in southern China, water content, free ²²⁰Rn production rate, and effective diffusion coefficient of ²²⁰Rn in uranium tailings were determined under certain environmental temperature and humidity conditions. Results show that: (1) The method and experimental setup presented in this study can simultaneously determine free ²²⁰Rn production rate and effective diffusion coefficient of ²²⁰Rn in porous media such as uranium tailing; (2) The free ²²⁰Rn production rate in uranium tailings increases linearly with water saturation. Effective diffusion coefficient of ²²⁰Rn, on the other hand, decreases exponentially with the increase in water saturation.

A fast method for the simultaneous determination of soil radon (222Rn) and thoron (220Rn) concentrations by liquid scintillation counting

This paper presents a fast method dedicated to measurements of radon nuclides in the soil gas. The soil gas is sampled by a typical hollow tube probe by 10 min of sucking of about 3 dm³ of gas and passing it directly through a 16 cm³ of water-immiscible liquid scintillator placed in a typical 20 cm³ scintillation vials, where the radon and thoron nuclides are effectively absorbed. Most of the presently used active methods for radon isotopes determination (e.g., RAD7 or AlphaGuard) require the soil gas transfer to the measuring device. The serious limitation of such approach is the necessity to wait until the radon daughter isotopes decay, before counter is ready for the next measurement. In the proposed method, several samples can be simultaneously gathered from the examined areas in the form of the scintillation vials, which are ready for later measurements in the automatic liquid scintillation counters in the lab or directly in situ. For that purpose, the combined mathematical model for the simultaneous radon and thoron determination has been elaborated. The direct in situ measurements of the sample activity between 60 and 240 s after the end of sampling followed by a second activity measurement after 3 h allow for the determination of both ²²⁰Rn and ²²²Rn concentrations in the soil gas. The limit of detection for ²²²Rn isotope during 10 min counting is 25 Bq·m^-3, whereas for a 3 min counting of ²²⁰Rn just after sampling was found to be ca. 150 Bq·m^-3. The method was successfully verified and applied for the simultaneous radon and thoron concentrations measurements in the soil gas in Central Poland region.