Accumulation Chamber Research Articles

Indoor radon and thoron from building materials: Analysis of humidity, air exchange rate, and dose assessment

Building materials contribute significantly to the indoor radon and thoron levels. Therefore, parameters that influence the exhalation rates of radon and thoron from building material need to be analyzed closely. As a preliminary study, the effects of humidity on exhalation rates were measured using a system with an accumulation chamber and RAD7 detector for Korean brick, Korean soil, and Indonesian brick. Resulting doses to a person who resides in a room constructed from the building materials were assessed by UNSCEAR method for different air exchange rates. The measurements have revealed that Korean brick exhaled the highest radon and thoron while Indonesian brick exhaled the lowest thoron. Results showed that for a typical low dense material, radon and thoron exhalation rate will increase until reached its maximum at a certain value of humidity and will remain saturated above it. Analysis on concentration and effective dose showed that radon is strongly affected by air exchange rate (ACH). This is showed by about 66 times decrease of radon dose from 0.00 h−1 to those of 0.50 h−1 ACH and decrease by a factor of 2 from 0.50 h−1 to those of 0.80 h−1. In case of thoron, the ACH doesn't have significant effects on effective dose.

Applicability of the closed-circuit accumulation chamber technique to measure radon surface exhalation rate under laboratory conditions

A layer of phosphogypsum was placed at the bottom of two large volume boxes. This system allowed to measure the surface radon exhalation from phosphogypsum without altering the emitting material. The limits and optimal setup of the closed-circuit accumulation chamber technique were thoroughly studied. More precisely, the performance of different radon exhalation fitting methods was analyzed in the reference exhalation boxes, employing different measurement devices and three smaller operational accumulation chambers. As expected, the best approach to obtain the radon exhalation rate depends upon the effective decay constant of the measurement system and the time employed to perform the measurement. The time until the linear approximation can no longer be applied was scrutinized. Although this approximation is usually applied routinely in the literature, the effective time constant of the chamber is often not low enough for the linear fit to be applied safely, providing statistically acceptable measurements that can lead to significative underestimations of the radon exhalation rate.

Methanotrophy in geothermal soils, an overlooked process: The example of Nisyros island (Greece)

A multidisciplinary field campaign was carried out at Nisyros Island (Greece). Hydrothermal gases were sampled and analysed, and CH4 and CO2 fluxes from the soils were measured with the accumulation chamber method. The sampling area (Lakki plain) covers an area of about 0.08 km2, and includes the main fumarolic areas of Kaminakia, Stefanos, Ramos, Lofos and Phlegeton. Flux values measured at 130 sites range from −3.4 to 1420 mg m−2 d−1 for CH4 and from 0.1 to 383 g m−2 d−1 for CO2. The fumarolic areas show very different CH4 degassing patterns, Kaminakia showing the highest CH4 output values (about 0.8 t a−1 from an area of about 30,000 m2) and Phlegeton the lowest (about 0.01 t a−1 from an area of about 2500 m2). The total output from the entire geothermal system of Nisyros should not exceed 2 t a−1. Previous indirect estimates of the CH4 output at Nisyros, based on soil CO2 output and CH4/CO2 ratios in fumarolic gases, were more than one order of magnitude higher. The present work further underscores the utmost importance of direct CH4 flux data because indirect methods totally disregard methanotrophic activity within the soil. Ten soil samples were collected for CH4 consumption experiments and for metagenomic analysis. Seven of the soil samples showed small but significant CH4 consumption (up to 39.7 ng g−1 h−1) and were positive for the methanotrophs-specific gene (pmoA) confirming microbial CH4 oxidation in the soil, notwithstanding the harsh environmental conditions (high temperature and H2S concentrations and low pH).

Influence of the accumulation chamber insertion depth to measure surface radon exhalation rates

A common method to measure radon exhalation rates relies on the accumulation chamber technique. Usually, this approach only considers one-dimensional gas transport within the soil that neglects lateral diffusion. However, this lateral transport could reduce the reliability of the method. In this work, several cylindrical-shaped accumulation chambers were built with different heights to test if the insertion depth of the chamber into the soil improves the reliability of the method and, in that case, if it could limit the radon lateral diffusion effects. To check this hypothesis in laboratory, two reference exhalation boxes were manufactured using phosphogypsum from a repository located nearby the city of Huelva, in the southwest of Spain. Laboratory experiments showed that insertion depth had a deep impact in reducing the effective decay constant of the system, extending the interval where the linear fitting can be applied, and consistently obtaining reliable exhalation measurements once a minimum insertion depth is employed. Field experiments carried out in the phosphogypsum repository showed that increasing the insertion depth could reduce the influence of external effects, increasing the repeatability of the method. These experiments provided a method to obtain consistent radon exhalation measurements over the phosphogypsum repository.

Offering subterranean clover can reduce methane emissions compared with perennial ryegrass pastures during late spring and summer in sheep

Sheep production systems in south-west Victoria are based predominantly on perennial ryegrass pastures, resulting in highly seasonal growth and declining feed quantity and nutritive value in late spring and summer. These changes result in reduced animal performance and increased CH4 emissions per kg DM intake. A potential alternative to the feedbase used in south-west Victoria that provides high quality and quantity of feed in late spring and early summer are legume-based pastures, such as clovers and lucerne. This experiment examined the impact of legume-based pastures on the growth rates and CH4 emissions of Maternal Composite ewes during late spring and early summer. In 2014, 240 Maternal Composite ewes grazed either perennial ryegrass (Lolium perenne L.), lucerne (Medicago sativa L.), subterranean clover (Trifolium subterraneum L.) or arrowleaf clover (Trifolium vesiculosum Savi.) pastures for 6 weeks during late spring and early summer (November and December). Sheep grazing subterranean clover were heavier at the end of the experiment than sheep grazing perennial ryegrass. Methane measurements using portable accumulation chambers indicated lower daily CH4 emissions (g/day) from sheep grazing subterranean clover (23.5 g/day) than from sheep grazing lucerne (27.3 g/day) and perennial ryegrass (32.3 g/day) pastures. Methane emissions and liveweight changes appeared to be associated with the nutritive characteristics of the forage offered. Legume-based pastures provide sheep producers in south-west Victoria an option to increase growth rates and decrease CH4 emissions during a period when perennial ryegrass pastures are declining in nutritive value.

Lead-210 profiles in radon barriers, Indicators of long-term Radon-222 transport

Conventional measurements of fluxes of Rn-222 from engineered earthen covers over uranium milling wastes use accumulation chambers over a 24-h period, making them sensitive to short-term environmental fluctuations. It is unlikely that such measurements represent a long-term average required for assessing cover performance. An alternative flux measurement approach is explored here based on the hypothesis that measurements of Pb-210 (a daughter of Rn-222) concentrations in the barrier material indicate where Rn-222 decayed in the barrier profile and thus indicate Rn transport within the barrier over long times. Samples of radon barrier materials from four mill tailings sites have been analyzed for Pb-210. In many cases, Pb-210 was detectable, was substantially above background values, and had higher concentrations at the bottom of the barrier adjacent to the underlying tailings. In some profiles, Pb-210 was found to decrease to background concentrations part way through the barrier, indicating that all Rn-222 had decayed before reaching the top. In other cases, Pb-210 concentrations were elevated near the top of the barrier, indicating radon migration through the entire radon barrier and possible long-term release of radon. These observations were generally confirmed by radon flux measurements at the top of the radon barrier. Some measured profiles of Pb-210 with depth in the radon barrier can be modeled by simple diffusion, suggesting that the diffusive transport mechanism, which was assumed for the original design of the barriers, is appropriate. In other cases, the Pb-210 profiles are not effectively modeled by diffusion, suggesting that at some locations the transport mechanism is complex and does not conform to the assumed process. Findings from this work indicate that Pb-210 concentrations measured near the top of radon barriers are promising as a monitoring approach for long-term Rn-222 radon fluxes. More detailed profiles of Pb-210 coupled with moisture and density information can be used to assess long-term Rn transport mechanisms.

Blood feeding activates the vitellogenic stage of oogenesis in the mosquito Aedes aegypti through inhibition of glycogen synthase kinase 3 by the insulin and TOR pathways

Most mosquitoes, including Aedes aegypti, only produce eggs after blood feeding on a vertebrate host. Oogenesis in A. aegypti consists of a pre-vitellogenic stage before blood feeding and a vitellogenic stage after blood feeding. Primary egg chambers remain developmentally arrested during the pre-vitellogenic stage but complete oogenesis to form mature eggs during the vitellogenic stage. In contrast, the signaling factors that maintain primary egg chambers in pre-vitellogenic arrest or that activate vitellogenic growth are largely unclear. Prior studies showed that A. aegypti females release insulin-like peptide 3 (ILP3) and ovary ecdysteroidogenic hormone (OEH) from brain neurosecretory cells after blood feeding. Here, we report that primary egg chambers exit pre-vitellogenic arrest by 8 h post-blood meal as evidenced by proliferation of follicle cells, endoreplication of nurse cells, and formation of cytoophidia. Ex vivo assays showed that ILP3 and OEH stimulate primary egg chambers to exit pre-vitellogenic arrest in the presence of nutrients but not in their absence. Characterization of associated pathways indicated that activation of insulin/insulin growth factor signaling (IIS) by ILP3 or OEH inactivated glycogen synthase kinase 3 (GSK3) via phosphorylation by phosphorylated Akt. GSK3 inactivation correlated with accumulation of the basic helix-loop-helix transcription factor Max and primary egg chambers exiting pre-vitellogenic arrest. Direct inhibition of GSK3 by CHIR-99021 also stimulated Myc/Max accumulation and primary egg chambers exiting pre-vitellogenic arrest. Collectively, our results identify GSK3 as a key factor in regulating the pre- and vitellogenic stages of oogenesis in A. aegypti.

CO2 degassing from Pico Island (Azores, Portugal) volcanic lakes

The CO2 degassing from lakes on Pico Island (Azores archipelago) were characterized in order to estimate the total diffuse CO2 output and identify the possible sources of CO2. Two surveys have been made in each lake (Capitão, Caiado, Rosada, Peixinho, Paúl and Seca), in the winter and summer periods. These water bodies show small surface areas and are rather shallow, with depths ranging from 1.8 to 8.6 m. Water samples are cold, both in winter and summer periods, not presenting variations along the water column, with acid to neutral pH (5.26–7.06). The electrical conductivity values point out to very diluted waters (mean range between 27 and 33.4 μS cm−1), of the Na-Cl type, corresponding to meteoric waters influenced by marine salts.To measure the CO2 flux at the lakes surface the modified accumulation chamber method was used, and a total of 1632 measurements were accomplished (711 in winter surveys and 921 in summer). Two statistical analysis (GSA and sGs) were applied to the results of diffuse CO2 flux measurements, showing that the CO2 flux values measured in theses lakes are relatively low (0.60–20.47 g m−2 d−1), what seems to indicate a single source for CO2 (biogenic source), also suggested by the water δ13C isotopic signature.CO2 emissions range between 0.04 t d−1 (Rosada_1) and 0.25 t d−1 (Caiado_1) during the winter surveys, being in general similar to the values recorded during the summer surveys that vary between 0.03 t d−1 (Peixinho_2 and Seca_1) and 0.30 t d−1 (Caiado_2). Taken into account the surface area of the lakes, the highest values were estimated for both surveys made in Seca Lake (˜13 t km−2 d−1). The occurrence of a dense macrophyte mass in a few of the studied lakes, such as Caiado and Seca, seems to enhance the CO2 flux from these water bodies.

Testing the tunable diode laser system in extreme environments: Measuring high and low CO2 concentrations in both active volcanic and geothermal settings

Measuring CO2 emissions in geothermal and volcanic areas is sometimes difficult because of large areas to cover and sites often inaccessible. Measuring high levels of CO2 concentration can provide information on hidden structure in geothermal areas and recording changes in CO2 concentration on volcanic areas can help monitor the level of volcanic activity. The purpose of this study was to use the Tunable Laser Diode (TDL) absorption spectroscopy method to test levels of CO2 concentrations at two extreme environments: White Island volcano, the most active volcano of New Zealand, with large and concentrated gas fluxes, and Ngapouri geothermal area, a small geothermal area in the Taupo Volcanic Zone, New Zealand, with relatively low and diffuse gas emissions. In 2017, for the first time using TDL at White Island, CO2 concentration measurements performed across the active fumarole fields had the highest CO2 concentrations of 657 ppm. TDL survey measurements were also conducted across fault strands near the Ngapouri geothermal area, and the results complemented CO2 flux results obtained with the accumulation chamber method. Higher CO2 concentrations were measured close to the mapped Ngapouri splays with a maximum of 484 ppm. The maximum CO2 flux measured in the same area was 100 g m−2 day−1 however the highest CO2 fluxes measured along the transects and by the mapped faults were less clear, but the CO2 concentrations increased closer to the fault splays. Advantages and disadvantages of using a TDL system have been described and compared to the accumulation chamber method. The results from the TDL system demonstrated that CO2 concentrations can be used as a tool, with other geophysical tools, for both detecting and highlighting geological structures where no obvious thermal activity is present and for monitoring purposes on active volcanoes.

CO2 Flux from Volcanic Lakes in the Western Group of the Azores Archipelago (Portugal)

Here, we present the first detailed study on diffuse CO2 degassing in the lakes in the Western Group (Corvo and Flores islands) of the Azores archipelago. This research is of interest in order to determine (1) the overall CO2 emission from such lakes, as volcanic lakes are often underrepresented in the databases of these water bodies, and (2) the diffuse CO2 degassing estimates in active volcanic areas such as the Azores. The lake waters on Corvo and Flores islands are mainly of the Na–Cl type, which is likely caused by the lakes’ sea salt signatures, arising from nearby seawater spraying; however, a few samples show evidence of slight alkali earth metal and bicarbonate enrichments in the lake waters, suggesting a contribution of water–rock interaction. In this study, diffuse CO2 flux measurements were taken using the accumulation chamber method, and statistical analyses utilizing the graphical statistical approach (GSA) and sequential Gaussian simulation (sGs) were conducted on the CO2 flux data, showing that the CO2 flux values measured in these lakes were relatively low (0.0–18.6 g m−2 d−1). The results seem to indicate that there is a single source of CO2 (a biogenic source), which is also supported by the waters’ δ13C isotopic signatures. Significant differences in the final CO2 output values were verified between surveys (e.g., 0.16 t d−1 in R1; 0.32 t d−1 in R2), and these differences are probably associated with the monomictic character of the lakes. CO2 emissions ranged between 0.18 t d−1 (CE1) and 0.50 t d−1 (CW1) for the Corvo lakes and between 0.03 t d−1 (P1) and 0.32 t d−1 (R2) for the seven lakes studied on Flores Island. The presence of a dense macrophyte mass in a few of the lakes appears to enhance the CO2 flux in these lakes.

Two-side cathode microbial electrolysis cell for nutrients recovery and biogas upgrading

Here a three-chamber microbial electrolysis cell (MEC) has been developed to couple the CO2 removal from a gas mixture to the ammonium nitrogen recovery. The here proposed MEC adopted an innovative two-side cathode configuration, where two identic cathodic chambers are connected in parallel by a titanium wire and separated from an intermediate anodic compartment by an anion and a cation exchange membrane (AEM and CEM). The two-side configuration has been proposed as a post treatment unit capable to perform the biogas upgrading through the CO2 reduction and removal into the cathodic chambers as well as the ammonium recovery from a liquid waste stream due to its migration for the electroneutrality maintenance of the cell. The experiments have been conducted at two different anodic potential (i.e. +0.2 and −0.1 V vs Standard Hydrogen Electrode SHE), using a synthetic feeding solution and a gas mixture simulating a domestic wastewater and a biogas, respectively. The results obtained using the new configuration have been also compared to the performances reported in a previous work where a three – chamber MEC, characterized by the presence of an intermediate accumulation chamber, was aimed to the CO2 removal and to nitrogen recovery; this comparison highlighted higher performances of the two-side configuration in terms of methane production, CO2 removal and energy consumption, keeping the same anodic performances.

CO2 fluxes of two lakes in volcanic caves in the Azores, Portugal

This paper characterises diffuse CO2 degassing from lakes located inside volcanic caves on the islands of Terceira and Graciosa (in the Azores archipelago, Portugal). The Algar do Carvão lake is located inside a volcanic pit on Terceira at an altitude of 92 m and has a surface area of 11,500 m2 and a maximum depth of 8.2 m. The Furna do Enxofre lake is located inside a lava cave on Graciosa at an altitude of 500 m and has a surface area of approximately 300 m2 and a maximum depth of 9.3 m.The water temperature of both lakes is low, with values ranging between 11 °C and 13 °C, in both the winter and summer periods, and no variations are observed along their water columns. The electrical conductivity ranges from 585 μS cm−1 to 687 μS cm−1 in Furna do Enxofre and from 117 μS cm−1 to 131 μS cm−1 in Algar do Carvão, reflecting a higher mineralisation in the former lake. The pH values in Furna do Enxofre range between 6.50 and 6.58, which reflects the effect of CO2 dissolution, while in Algar do Carvão, the pH values are more basic (7.42–8.53). The water types are Mg-HCO3 for Furna do Enxofre and Na-HCO3 for Algar do Carvão; the Mg-enrichment in Furna do Enxofre is associated with water–rock interactions, which are enhanced by the acidic environment.Diffuse CO2 flux measurements were made using the accumulation chamber method, with a total of 37 measurements split into two surveys at Algar do Carvão and 71 measurements during a single survey at Furna do Enxofre. The total CO2 emitted from Furna do Enxofre was 6100 kg d−1, which was much lower than that emitted from Algar do Carvão (0.32–2.0 kg d−1). A volcanic origin was assigned to the lake on Graciosa due to the δ13C isotopic signature of the CO2; conversely, the CO2 released in Algar do Carvão is derived from a biogenic CO2 source.Considering the surface areas of the studied lakes, the CO2 flux is in the range of 1.5–6.7 t km−2 d−1 for Algar do Carvão and is 508.3 t km−2 d−1 for Furna do Enxofre.

Diffuse CO2 flux emission in two maar crater lakes from São Miguel Island (Azores, Portugal)

Santiago and Congro are two maar crater lakes, located at São Miguel, the largest island of the Azores archipelago. Santiago Lake is located on the Sete Cidades Volcano, at an altitude of 364 m, presenting a surface area of 0.25 km2 and a maximum depth of 33 m. Congro Lake is located on the Congro Fissural Volcanic System, at an altitude of 420 m, and has a surface area of 0.04 km2 and a maximum depth of 22 m. Both lakes are monomictic in character, with low mineralized waters of meteoric origin, being the temperature in the range between 12.4 °C (winter period) and 23.8 °C (summer period). The main water type is Na-HCO3, and the relative major-ion composition is HCO3− > Cl− > SO42− > F− for anions and Na+ > K+ > Mg2+ > Ca2+ for cations.Four sampling surveys were carried out between 2013 and 2016 in each lake in order to estimate surface diffuse CO2 degassing. A total of 1612 and 713 CO2 flux measurements were made with an accumulation chamber at Santiago and Congro lakes, respectively.The higher CO2 fluxes were measured during the winter surveys (0.2 t d−1 in Congro and 5.6 t d−1 in Santiago), while the lowest values (0.1 t d−1 and 0.2 t d−1, respectively, in Congro and Santiago lakes) were recorded in the summer. These seasonal differences observed in both lakes are associated with the monomictic character of the lakes, as the CO2 is not able to ascend to the surface when the water column is stratified during the warmer period. Due to the physical processes that occur in both lakes, the CO2 emission is mostly associated to a biogenic origin, but the higher CO2 emissions measured in Santiago Lake suggest that a volcanic influence cannot be excluded, as also shown through the heavier δ13C isotopic measured in this water body. The tectonic structures that cross Santiago Lake probably enable the observed degassing.

Automatic Filtering of Soil CO2 Flux Data; Different Statistical Approaches Applied to Long Time Series

Monitoring soil CO2 diffuse degassing areas has become more relevant in the last decades to understand seismic and/or volcanic activity. These studies are specially valuable for volcanic areas without visible manifestations of volcanism, such as fumaroles or thermal springs. The development and installation of permanent soil CO2 flux instruments has allowed to acquire long time series in different volcanic environments, and the results obtained highlight the influence of environmental variables on the gas flux variations. A permanent soil CO2 flux station is installed at Caldeiras da Ribeira Grande area since June 2010. This degassing site is located in the north flank of Fogo Volcano, a polygenetic volcano at S. Miguel Island (Azores archipelago, Portugal). The station performs measurements based on the accumulation chamber method and has coupled several meteorological sensors. Average soil CO2 flux and soil temperature values around 1165 g m-2 d-1 and 33oC, respectively, were measured in this site between June 2010 and June 2017. This study discusses different statistical approaches applied to the long time series recorded in this degassing area, focusing on the application of stepwise multivariate regression analysis, wavelets and Fast Fourier Transform to understand the CO2 flux variations and to detect eventual anomalous periods that can represent deep changes in the volcano feeding reservoirs. Multivariate regression analysis shows that about 47% of the soil CO2 flux variations are explained by the effect of the soil and air temperature, wind speed and soil water content. Spectral analysis highlights the existence of 24 h cycles in the soil CO2 flux time series, mainly during the summer period. The models proposed have been applied on a near real-time automatic monitoring system and implementation of these approaches will be profitable in any volcano observatory of the world.

Research on the total leakage rate leak detection technology of the large spacecraft

The spacecraft is becoming bigger and bigger. This development trend brings us a strict challenge for the leak detection of spacecrafts, especially for the total leakage rate leak detection. So it is important to study the total leakage rate leak detection technology of the large spacecraft. In this paper, an idea on large flexible accumulation chamber was provided to overcome this strict challenge. But at the same time it also brings two key problems to be solved. That is how to build the large flexible accumulation chamber for accommodating the large spacecraft and whether the mixed helium gas concentration on the height direction in this flexible accumulation chamber is uniform because helium is lighter than air. The feasibility on building the large flexible accumulation chamber for the total leakage rate leak detection of the large spacecraft was firstly analyzed. Secondly, the mixed helium gas distributing rules on the height direction in the large accumulation chamber was also given from the theoretic analysis. Finally, a large flexible accumulation chamber was built for the total leakage rate leak detection of the large spacecraft and the six times repeatability tests were also finished. The results here indicated that the six times repeatability tests owned a well consistency and the large flexible accumulation chamber was suitable for the total leakage rate leak detection of the large spacecraft.

New Variable Stiffness Damper with Magnetorheological-Based Accumulator Control

This paper introduces a new design of variable stiffness damper using controlled accumulator filled with Magnetorheological (MR) fluids. The originality of the new design is in its capability to offer less consumption of MR fluids than the conventional design of MR damper. The new design does not fill the whole cylinder with MR fluids but only use the accumulator space as the volume compensation control zone with MR fluids. The MR fluids control the compressive movement of the accumulator piston which alter the flow of the hydraulic oil to the accumulator chamber. As a result, the regulated flow of oil to the accumulator chamber will only have a direct effect to the compression stiffness of the damper. The experimental results show that the proposed design is capable to adjust the compression force while maintaining the rebound force of the damper.

Particle-Transfer Between the Cyclone and Accumulator Sections of a Desander

Summary The flooded-core solid/liquid hydrocyclone, also called a desander, is often used in the upstream oil and gas industry to separate particulate solids from produced water. A desander incorporates a solid/liquid cyclone with an accumulation chamber connected to the apex. Solids collect in the accumulator for intermittent removal while the overflow is discharged continuously. With a flooded-core and static-liquid volume in the accumulator, the trajectory of a sand particle from the cyclone inlet to the apex is changed, compared with that in an open underflow hydrocyclone classifier. In this project, the transfer of solids from the cyclone to the accumulator section is studied, with emphasis on the limiting flux. The settling of solids from the cyclone to the accumulator follows a turbulent, hindered-settling relationship that can be approximated by models used for sedimentation hoppers. Measurement of the apex-flux rate shows a maximum choke point, beyond which solids will back up into the cyclone section. The limiting inlet solids concentration to reach this choke point is ≈2 g/L for small-diameter desanders. An apex-flux balancing system is proposed to overcome this flux-rate limitation.

Occurrence of a nearly constant air flux through the accumulation chamber and determination of the two components of the CO2 flux from soil. I: Laboratory experiments.

Different types of laboratory experiments were carried out during this study. In type A experiments a standard gas mixture is continuously injected, at constant flux, into the accumulation chamber, mimicking the soil CO 2 flux measurements performed in field surveys. In type B experiments, a standard gas mixture is initially injected into the accumulation chamber for a short lapse of time, to achieve a relatively high CO 2 concentration inside the accumulation chamber; then the injection of the standard gas mixture is stopped and the CO 2 concentration inside the chamber is monitored for a sufficient interval of time. In both types of experiments, the accumulation chamber appears to be flushed by a considerable flux of atmospheric air, which is virtually constant in each experiment but is different from experiment to experiment. The occurrence of this air flux through the accumulation chamber (i) has no effect on the determination of the soil CO 2 flux on the basis of the initial slope (at time zero) of the CO 2 concentration-time curve, but (ii) it complicates the evaluation of the two components of the soil CO 2 flux, namely the CO 2 molar fraction of soil gas and the flux of the soil gas mixture. A method to obtain both the CO 2 molar fraction of soil gas and the flux of the soil gas mixture is presented and the implications related to the knowledge of the two components of the soil CO 2 flux are discussed.

ISSUES IN ASSESSMENT OF POTENTIAL RADON HAZARD AT BUILDING SITES

High concentrations of radon in the premises leads to a risk of lung cancer for the population. In this regard, in the production of design and construction works, an assessment is made of the potential hazard of radon in the construction sites. At the present, the unified approach to methodology of assessment is not developed. Abroad, various categorical and numerical values, such as radon potential or radon index, are used as criteria for radon hazard. In different countries, these criteria are determined using various parameters: uranium / radium concentration, radon volumetric activity in soil air and premises, gas permeability of soils, geological structure of underlying rocks, dose rate of gamma radiation. Studies conducted abroad show that the parameters used, as a rule, do not correlate with the amount of radon entering buildings during its operation. In the Russian Federation, the radon flux density measured on the soil surface is used to estimate the potential radon hazard of a building site. Applied today method of potential radon hazard assessment has one general drawback. It is low reliability of results. Such a quality of assessments obtained by measuring the radon flux density is due to the variability in the values of this value and to the measurement of the surface of the soil. The paper discusses the results of measuring the radon flux density obtained by the methods of «accumulation chambers» and «carbon adsorbers» in the summer periods of 2014, 2016 and 2017. It was confirmed that the strongest influence on the values and variability of radon flux density is exerted by precipitation. The paper presents the results of radon flux density measurements on the soil surface, as well as on the surface of dense loams lying at depths of 0.5 m and 1.5 m. It is shown that the radon flux density measured on the soil surface is two to three times smaller than the values of this value measured on the surface of dense rocks. It is important to note that the lowest variability of the results (20%) was observed in 2014, when measurements were made on the surface of dense loams during dry, stable weather.

Open‐loop geothermal heat exchanger system for heating and cooling of the Sport arena in Skopje

AbstractThe alternative energy sources are essential for the sustainable development and protection of the environment. In this context, the renewable energy usage had become the new engineering paradigm. The direct use of geothermal energy for cooling and heating is simple and efficient alterative which is widely available and without any restrictions or conditions. Nowadays, more and more buildings use the geothermal energy satisfying more than 80% of the total energy demand for heating and cooling. Most popular are the geothermal heat exchanger systems with deep installations due to their efficiency and cost‐effectiveness. Such an example is the geothermal system of the new Sport arena build in Skopje with open‐loop geothermal heat exchangers is classified as energy efficient facility under class. The primary fluid‐water is exhilarated from the five 30 m geothermal exploitation wells, which through heat pumps is brought to the accumulation chamber inside the building bellow the main court where the heat is stored. Hence, the system is planned to operate in night mode during the cheaper energy tariff used by energy pumps, later to use the stored heat or cold for daily needs. A significant role in the system plays the controlling system with three different management levels.