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.

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.

A COMPREHENSIVE STUDY OF RESIDENTIAL, GEOGENIC AND WATER RADON IN THE NORTH AREA OF MURES COUNTY, ROMANIA.

This study presents results of a complex survey about residential, soil and water radon in the North of Mures county (Romania). Indoor radon measurements were performed by using CR-39 track detectors, while radon concentrations in soil and in water were measured by using the LUK3C device and accessories. The indoor radon concentrations of 157 houses ranged from 9 to 414 Bq m-3, with an arithmetic mean of 131 Bq m-3 and a geometric mean of 105 Bq m-3. In ~3.2% of the investigated houses exceed the recommended reference level of 300 Bq m-3. The soil gas radon concentrations in 137 sampling points varied from 5.0 to 88.0 kBq m-3, with a geometric mean of 14.6 kBq m-3. Results of 190 water samples shows radon concentrations from 0.2 to 28.0 Bq L-1, with a geometric mean of 5.0 Bq L-1. Beside these results, indoor, soil and water radon maps were performed, divided into cells of 5 km × 5 km.

Residential, soil and water radon surveys in north-western part of Romania.

The exposure to radon and radon decay products in homes and at workplaces represents the greatest risk from natural ionizing radiation. The present study brings forward the residential, soil and water radon surveys in 5 counties of Romania. Indoor radon measurements were performed by using CR-39 track detectors exposed for 3 months on ground-floor level of dwellings, according to the NRPB Measurements Protocol. Radon concentrations in soil and water were measured using the LUK3C device. The indoor radon concentrations ranged from 5 to 2592 Bq⋅m-3 with an updated preliminary arithmetic mean of 133 Bq⋅m-3, and a geometric mean of 90 Bq⋅m-3. In about 6% of the investigated grid cells the indoor radon concentrations exceed the threshold of 300 Bq⋅m-3. The soil gas radon concentration varies from 0.8 to 169 kBq⋅m-3, with a geometric mean of 28.4 kBq⋅m-3. For water samples, the results show radon concentrations within the range of 0.3-352 kBq⋅m-3 with a geometric mean of 7.7 Bq⋅L-1. The indoor radon map was plotted on a reference grid developed by JRC with the resolution 10 × 10 km2.

Testing radon mitigation techniques in a pilot house from Baita-Stei radon prone area (Romania).

This work presents the implementation and testing of several radon mitigation techniques in a pilot house in the radon prone area of Baita-Stei in NW part of Romania. Radon diagnostic investigations in the pilot house showed that the main source of radon was the building sub-soil and the soil near the house. The applied techniques were based on the depressurization and pressurization of the building sub-soil, on the combination of the soil depressurization system by an electric and an eolian fans. Also, there was made an application of a radon barrier membrane and a testing by the combination of the radon membrane by the soil depressurization system. Finally, the better obtained remedial efficiency was about 85%.

Soil and building material as main sources of indoor radon in Baita-Stei radon prone area (Romania).

Radon contributes to over than 50% of the natural radiation dose received by people. In radon risk areas this contribution can be as high as 90-95%, leading to an exposure to natural radiation 5-10 times higher than normal. This work presents results from radon measurements (indoor, soil and exhalation from building materials) in Baita-Stei, a former uranium exploitation area in NW Romania. In this region, indoor radon concentrations found were as high as 5000 Bq m(-3) and soil radon levels ranged from 20 to 500 kBq m(-3). An important contribution from building materials to indoor radon was also observed. Our results indicate two independent sources of indoor radon in the surveyed houses of this region. One source is coming from the soil and regular building materials, and the second source being uranium waste and local radium reached material used in building construction. The soil as source of indoor radon shows high radon potential in 80% of the investigated area. Some local building materials reveal high radon exhalation rate (up to 80 mBq kg(-1) h(-1) from a sandy-gravel material, ten times higher than normal material). These measurements were used for the radon risk classification of this area by combining the radon potential of the soil with the additional component from building materials. Our results indicate that Baita-Stei area can be categorized as a radon prone area.

Thorough investigations on indoor radon in Baita radon-prone area (Romania).

A comprehensive radon survey has been carried out in Baita radon-prone area, Transylvania, Romania, in 4 localities (Baita, Nucet, Fînate, and Cîmpani) situated in the vicinity of former Romanian uranium mines. Indoor radon concentrations have been measured in 1128 ground floor rooms and cellars of 303 family houses by using CR-39 diffusion type radon detectors. The annual average of indoor radon concentration for Baita area was found to be 241±178 Bq m(-3), which is about two times higher than the average value of 126 Bq m(-3), computed for Romania. About 28% of investigated houses exceed the reference level of radon gas in dwellings of 300 Bq m(-3). The indoor radon measurements on each house have been carried out in several rooms simultaneously with the aim of obtaining a more detailed picture on the exposure to radon in the studied area. An analysis on the variability of radon levels among floors (floor-to-floor variation) and rooms (room-to-room variation) and also the influence of factors like the presence of cellar or the age of the building is presented. The coefficient of variation (CV) within ground floor rooms of the same house (room-to-room variation) ranged between 0.9 and 120.8%, with an arithmetic mean of 46.2%, a large variability among rooms within surveyed dwellings being clearly identified. The mean radon concentration in bedrooms without cellar was higher than in bedrooms above the cellar, the difference being statistically significant (t test, one tail, p<0.001, n=82). For houses built during 1960-1970 an increasing trend for radon levels was observed, but overall there was no significant difference in indoor radon concentrations by age of dwelling (one-way ANOVA test, p>0.05).