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[en] Highlights: • Development of an analytical model for assessing the well-mixing length of a tracer in a duct airflow. • Validation on data from in situ experiments. • Model simplification for proposing correlations more suitable for the industrial issue. - Abstract: The aim of this study is to propose an analytical model for assessing the well-mixing length of a tracer in a ventilation duct. The first part of the article is devoted to describe an experimental bench developed for validating the proposed model. This bench allows to follow the evolution of a tracer injected at a source point in the center of a duct by using an original optical measurement technique. In a second part, an analytical model for the spatial evolution of a tracer concentration in a circular duct is developed, taking into account an eddy viscosity model. The difficulty for applying this model to industrial cases led us to propose a simplified version that can be used for a non-dimensional distance greater than 20 diameters. The latter was then inverted in order to access to two criteria: the coefficient of variation in the duct section and the difference between the local measured concentration and the expected homogeneous concentration. Each one has its interest depending on whether a global information on the duct section or a local information (on the axis for example) at a given distance is required.
[en] Highlights: • Outdoor radon levels can cause departure from lognormal indoor radon distribution. • An analytical method is proposed to evaluate and correct outdoor impact for every radon distribution. • Results of this study can be useful for a correct classification of radon areas. - Abstract: Outdoor radon concentration contributes to indoor radon levels, generally causing a shift from lognormal distribution of measured radon concentration data distribution, and it makes more challenging the estimation of radon distribution parameters on the basis of the lognormal assumption. In particular, lognormal assumption with no correction could lead to a significantly biased estimate of the percentage of dwellings exceeding a certain level, e.g. a reference level (RL), since this is based on biased estimates of geometric mean (GM) and geometric standard deviation (GSD) of radon concentration distribution. Subtracting to each measured data a constant outdoor radon level can usually compensate data distribution departure from log-normality (except for low radon levels), if the appropriate outdoor level value is chosen by means of a lognormal fit of the data. This approach – already (but not always) used in literature – cannot be applied in cases where all the data of radon concentrations are not available (e.g., for a review study). For these cases, this work presents an analytical method to quantitatively evaluate and correct the impact of outdoor on the lognormal distribution parameter estimates and, in particular, on the percentages of dwellings exceeding radon reference levels. The proposed method is applied to a number of possible situations, with different values of outdoor radon level, GM and GSD. The results show that outdoor radon levels generally produce an underestimation of the actual GSD parameter, which increases as the outdoor level increases, and in the worse cases, could lead to an underestimation higher than 50%. Consequently, if the outdoor contribution is not properly taken into account, the percentage of dwellings exceeding a certain RL is almost always underestimated, even by 80%–90% for RL equal to 300 Bq/m3. This could have implications for the classification of areas as regards radon concentration and for the estimation of avertable lung cancers attributable to radon levels higher than some possible RLs.
[en] Highlights: • Indoor radon was measured in randomly selected newly built houses in 2008 and 2016. • New building regulations with preventive measures on radon was introduced in 2010. • A significant reduction of radon concentrations was found in detached houses. - Abstract: Results from two national surveys of radon in newly built homes in Norway, performed in 2008 and 2016, were used in this study to investigate the effect of the 2010 building regulations introducing limit values on radon and requirements for radon prevention measures upon construction of new buildings. In both surveys, homes were randomly selected from the National Building Registry. The overall result was a considerable reduction of radon concentrations after the implementation of new regulations, but the results varied between the different dwelling categories. A statistically significant reduction was found for detached houses where the average radon concentration was almost halved from 76 to 40 Bq/m3. The fraction of detached houses which had at least one frequently occupied room with a radon concentration above the Action Level (100 Bq/m3) fell from 23.9% to 6.4%, while the fraction above the Upper Limit Value (200 Bq/m3) was reduced from 7.6% to 2.5%. In 2008 the average radon concentration measured in terraced and semi-detached houses was 44 and in 2016 it was 29 Bq/m3, but the reduction was not statistically significant. For multifamily houses, it was not possible to draw a conclusion due to insufficient number of measurements.
[en] Highlights: • Inhaled radon risk to the health of the employees. • Radon concentrations in the hot springs. • Radon content reduction in thermal spas consists of diluting the geothermal water concentration with fresh water. • Hot springs negative aspect is not confirmed by experimental result (below 20 mSv a-1). - Abstract: Inhaled radon and its progenies induce health concern due to high activity-concentration in selected thermal spas of Boyacá region. Hydrogeothermal water sources in a high risk seismic area, are studied to determine by water bubbling method radon concentration values; their occurrence is between few hundreds and 2000 Bq dm−3. Deposits, existing in this area, reach at the surface soil gas radon concentration up to 210 kBq m−3. Maintenance workers, health tourists and visitor's possible detrimental health effects, are discussed in relation to radon balneotherapy beneficial aspects.
[en] In order to investigate the corrosion behavior and impact toughness of 105SS drill pipe steel in the wet H2S environment, the impact and corrosion testing were carried out. The results show that the diffusible hydrogen concentration is mainly influenced by the morphology of the corrosion scales and the dynamic fracture toughness loss of 105SS drill pipe steels increases with the increase of diffusible hydrogen concentration. However, when hydrogen was released, the impact energy increases. The area of quasi-cleavage features on the fracture surfaces increases with the increase of hydrogen concentration. (paper)
[en] Highlights: • Nationwide indoor radon survey in Montenegro. • Distribution of radon concentrations deviates from log-normality. • Log-normality obtained by subtracting contribution from radon in outdoor air. • Fraction of homes with high radon levels estimated using transformed data set. • National reference level, “urgent action level” and radon priority areas proposed. - Abstract: The first nationwide indoor radon survey in Montenegro started in 2002 and year-long radon measurements with CR-39 track-etch detectors, within the national grid of 5 km × 5 km and local grids in urban areas of 0.5 km × 0.5 km, were performed in homes in half of the country's territory. The survey continued in 2014 and measurements in the rest of the country were completed at the end of 2015. The 953 valid results, obtained in the national radon survey, give an average radon activity concentration in Montenegrin homes of 110 Bq/m3. Assuming a log-normal distribution of the experimental results, geometric mean GM = 58.3 Bq/m3 and geometric standard deviation GSD = 2.91 are calculated. However, normality tests show that the experimental data are not log-normal, and that they become closest to a log-normal distribution after subtracting from them radon concentration in the outdoor air of 7 Bq/m3, which is theoretically calculated. Such a transformed distribution has GMtr = 46.7 Bq/m3 and GSDtr = 3.54. The estimations derived from positing a priory that the experimental results conform to a log-normal distribution underestimate the percentage of homes with radon concentrations at the thresholds of 300 Bq/m3 and above, which is better estimated by using GMtr and GSDtr. Based on the results of radon survey, a new national radon reference level of 300 Bq/m3 and an “urgent action level” of 1000 Bq/m3 are suggested, with estimated fractions of the national dwelling stock above these levels of 7.4% and 0.8% respectively. Fractions of homes with radon concentrations above the suggested levels are also estimated for each of the 23 municipalities in Montenegro, using appropriate GMtr and GSDtr. The six municipalities which have more than 10% of homes with radon concentration above 300 Bq/m3 are recommended as radon priority areas.
[en] This paper has conducted a contrastive study on the AIRS retrieval results and the observational data of methane concentration at Mt. Waliguan atmospheric background station, and has analyzed the distribution characteristics of atmospheric methane concentration over the Qinghai-Xizang Plateau from 2003 to 2015. The results show that the AIRS retrieval data display the same monthly, annual, and seasonal variation trend, as well as segmental variation characteristics. The methane concentration features high in the north and low in the south along with the geographical line of Kunlun Mountains–Tanggula Mountains–Hengduan Mountains, and decreases significantly as the altitude rises, with the highest and the most sensitive variability in the south central region of the Qinghai-Xizang Plateau. From 2003 to 2015, the methane concentration in the Qinghai-Xizang Plateau continued to rise, with the fastest growth in autumn, the slowest in winter, and an annual growth rate of 5.2 nmol mol−1 a−1, while the growth rate from 2013 to 2015 was lower than the global average. The seasonal variation showed a unimodal curve, with the highest value in summer and the lowest value in spring, and with the altitude rising, the seasonal variation was more significant.
[en] Superabsorbent polymer (SAP) is a kind of polymer with advantages like high water absorption and conservation. We studied the effect of various concentrations of SAPs on the infiltration of soil water with sand mulching. Five soil columns with surface sand mulch and evenly distributed SAPs at concentrations of 0, 0.1, 0.2, 0.5 and 1.0% were tested. The SAPs slowed the migration of the wetting front and thus the rate of infiltration of water, and the higher the SAP concentration, the slower the migration. The relationship between the wetting front displacement and time could be described by a logarithmic function, . The amount of cumulative infiltration was inversely proportional to the amount of SAPs. The final cumulative infiltration was proportional to the amount of SAPs, within a limited range. The relationship between cumulative infiltration and time was described by a power function, . The relationship between wetting front displacement and cumulative infiltration could be characterized by a linear equation, , indicating that the rate of cumulative infiltration increased with the amount of SAPs for the same infiltration depth, which satisfied the Kostiakov model (). High concentrations of SAPs strongly inhibited the infiltration of water. The infiltration rate of soil water was optimal at a SAP concentration of 0.2%, which effectively increased the amount of water in the soil.