Gaseous Contaminants Research Articles

Geochemical evidence for fugitive gas contamination and associated water quality changes in drinking-water wells from Parker County, Texas.

Extensive development of horizontal drilling and hydraulic fracturing enhanced energy production but raised concerns about drinking-water quality in areas of shale-gas development. One particularly controversial case that has received significant public and scientific attention involves possible contamination of groundwater in the Trinity Aquifer in Parker County, Texas. Despite extensive work, the origin of natural gas in the Trinity Aquifer within this study area is an ongoing debate. Here, we present a comprehensive geochemical dataset collected across three sampling campaigns along with integration of previously published data. Data include major and trace ions, molecular gas compositions, compound-specific stable isotopes of hydrocarbons (δ13C-CH4, δ13C-C2H6, δ2H-CH4), dissolved inorganic carbon (δ13C-DIC), nitrogen (δ15N-N2), water (δ18O, δ2H, 3H), and noble gases (He, Ne, Ar), boron (δ11B) and strontium (87Sr/86Sr) isotopic compositions of water samples from 20 drinking-water wells from the Trinity Aquifer. The compendium of data confirms mixing between a deep, naturally occurring salt- (Cl >250mg/L) and hydrocarbon-rich groundwater with a low-salinity, shallower, and younger groundwater. Hydrocarbon gases display strong evidence for sulfate reduction-paired oxidation, in some cases followed by secondary methanogenesis. A subset of drinking-water wells contains elevated levels of hydrocarbons and depleted atmospherically-derived gas tracers, which is consistent with the introduction of fugitive thermogenic gas. We suggest that gas originating from the intermediate-depth Strawn Group ("Strawn") is flowing along the annulus of a Barnett Shale gas well, and is subsequently entering the shallow aquifer system. This interpretation is supported by the expansion in the number of affected drinking-water wells during our study period and the persistence of hydrocarbon levels over time. Our data suggest post-genetic secondary water quality changes occur following fugitive gas contamination, including sulfate reduction paired with hydrocarbon oxidation and secondary methanogenesis. Importantly, no evidence for upward migration of brine or natural gas associated with the Barnett Shale was identified.

Effect of H2S and NH3 in biomass gasification producer gas on CO2 capture performance of an innovative CaO and Fe2O3 based sorbent

This study has investigated the effect of contaminants in biomass gasification producer gas on the CO2 capture performance of an innovative CaO and Fe2O3 based sorbent material. It is well known that biomass gasification producer gas contains gaseous contaminants such as H2S and NH3. Experiments were conducted with the combined contaminants of H2S at 230 ppmv and NH3 at 2300 ppmv. Each run of the experiment included three major stages: H2 reduction, CO2 capture (carbonation) and CO2 release (calcination). The operation temperature was controlled at 650 °C with a duration of 3 h at the carbonation stage, and at 850 °C with a duration of 2 h at the calcination stage. In each experiment, three cycles of carbonation-calcination were performed.The experimental results show an average CO2 capture efficiency of 61.8% during the carbonation stage in the first cycle, reducing to 45.4% in the third cycle. However, effective CO2 capture was achieved in the initial 20 min of carbonation, with a capture efficiency of 75.1% for the first cycle and 62.8% in the third cycle.It was found that the CO2 sorbent can effectively remove contaminants from the producer gas, showing catalytic effect of the sorbent material. The H2S removal efficiency decreased from 99% in the first cycle to 82% after three cycles, while the NH3 removal efficiency was above 99% for all three cycles during the carbonation stage. Furthermore, concentrations of the N-based and S-based compounds in the outlet gas streams during calcination were examined for the potential impact when the gas is injected into plant nursery greenhouses for growth enhancement. Fundamental analysis was also performed and microstructural changes in the material were examined to understand the CO2 capture process by the tested sorbent.

Soil and grapevine leaf quality in organic vineyards of different ages in DO Rioja-Alavesa, northern Spain

The soil from three organically cultivated plots in Rioja Alavesa vineyards, specifically in Lanciego (Álava, Spain), and the foliage of their vines were analyzed. The aim of this study was to determine differences in soil and grapevine quality between different aged vineyards. The first 20 centimeters of the soil were sampled and leaves were collected during the growing season. The results show that the quality of the soil in the three plots was optimal and did not differ from reported values of soils from traditionally cultivated plots. The only element found at a lower concentration in the three plots and the leaves was iron. Organic cultivation of vineyards is a viable mode of cultivation and could help reduce greenhouse gas emissions and contamination by pesticides and fertilizers.

Strategies for Integrated Capture and Conversion of CO2 from Dilute Flue Gases and the Atmosphere.

The integrated capture and conversion of CO2 has the potential to make valorization of the greenhouse gas more economically competitive, by eliminating energy-intensive regeneration processes. However, integration is hindered by the extremely low concentrations of CO2 present in the atmosphere (0.04 vol.%), and the presence of acidic gas contaminants, such as SOx and NOx , in flue gas streams. This Review summarizes the latest technological progress in the integrated capture and conversion of CO2 from dilute flue gases and atmospheric air. In particular, the Review analyzes the correlation between material properties and their capture and conversion efficiency through hydrogenation, cycloaddition, and solar thermal-mediated electrochemical processes, with a focus on the types and quantities of product generated, in addition to their energy requirements. Prospects for commercialization are also highlighted and suggestions are made for future research.

Removal of off-resonance xenon gas artifacts in pulmonary gas-transfer MRI.

Hyperpolarized xenon (129 Xe) gas-transfer imaging allows different components of pulmonary gas transfer-alveolar air space, lung interstitium/blood plasma (barrier), and red blood cells (RBCs)-to be assessed separately in a single breath. However, quantitative analysis is challenging because dissolved-phase 129 Xe images are often contaminated by off-resonant gas-phase signal generated via imperfectly selective excitation. Although previous methods required additional data for gas-phase removal, the method reported here requires no/minimal sequence modifications/data acquisitions, allowing many previously acquired images to be corrected retroactively. 129 Xe imaging was implemented at 3.0T via an interleaved three-dimensional radial acquisition of the gaseous and dissolved phases (using one-point Dixon reconstruction for the dissolved phase) in 46 human subjects and a phantom. Gas-phase contamination (9.5%±4.8%) was removed from gas-transfer data using a modified gas-phase image. The signal-to-noise ratio (SNR) and signal distributions were compared before and after contamination removal. Additionally, theoretical gaseous contaminations were simulated at different magnetic field strengths for comparison. Gas-phase contamination at 3.0T was more diffuse and located predominantly outside the lungs, relative to simulated 1.5T contamination caused by the larger frequency offset. Phantom experiments illustrated a 91% removal efficiency. In human subjects, contamination removal produced significant changes in dissolved signal SNR (+7.8%), mean (-1.4%), and standard deviation (-2.3%) despite low contamination. Repeat measurements showed reduced variance (dissolved mean, -1.0%; standard deviation, -8.4%). Off-resonance gas-phase contamination can be removed robustly with no/minimal sequence modifications. Contamination removal permits more accurate quantification, reduces radiofrequency stringency requirements, and increases data consistency, providing improved sensitivity needed for multicenter trials.

Occupational Risk Assessment for Workers of Aluminum Production Using the Example of RUSAL Bratsk OJSC

Aluminum is considered one of the most commonly used materials and has a wide range of applications in various industries. However, the production of aluminum is associated with a significant negative impact on the health of workers engaged in technological operations to produce it. In this regard, the aim of the work was to assess the occupational risks of workers in aluminum production. As a result of the analysis, it was found that the technological process for producing aluminum has a complex of negative effects on the health of workers, which includes industrial noise, general and local vibration, gas and dust contamination of the air in the working area, exposure to electromagnetic fields and radiation, adverse microclimate parameters. The totality of dangerous and harmful factors in working conditions and negative indicators of injuries and occupational morbidity for aluminum production workers requires carrying out a procedure for assessing occupational risks. Of the whole set of methods, we selected the three most informative and easy to use methods, i.e. the method of scoring occupational risks, the method of assessing the IOR level and the Fine-Kinney method. The object of the study was RUSAL Bratsk Aluminum Smelter OJSC. Based on the results of the assessment, it was established that the general level of occupational risk in RUSAL Bratsk OJSC corresponded to the “medium” and “high” values of these methods, which is considered unacceptable. To reduce the risk, it is necessary, in particular, to implement additional or modernize existing labor protection measures.

Herriott cell spot imaging increases the performance of tunable laser spectrometers.

With the availability of high-power (milliwatts) single-mode tunable laser sources that operate at room temperature across the infrared (IR) region, tunable laser spectrometers have seen an explosion of growth in applications that include commercial, Earth and planetary science, and medical and industrial sensing. While the laser sources themselves have shown steady improvement, the detection architecture of using a single-element detector at one end of a multipass cell has remained unchanged over the last few decades. We present here an innovative new approach using a detector array coupled to an IR-transmissive mirror to image all or part of the multipass spot pattern of the far mirror and record spectra for each pixel. This novel approach offers improved sensitivity, increased dynamic range, laser power normalization, contaminant subtraction, resilience to misalignment, and reduces the instrument power requirement by avoiding the need for "fringe-wash" heaters. With many tens of pixels representing each spot during the laser spectral scan, intensity and optical fringe amplitude and phase information are recorded. This allows selection and manipulation (e.g., co-addition, subtraction) of the pixel output spectra to minimize optical interference fringes thereby increasing sensitivity. We demonstrate a factor of ∼20 sensitivity improvement over traditional single-element detection. Dynamic range increase of a factor of ∼100 is also demonstrated through spot selection representing different pathlengths. Additionally, subtracting the spectrum of the first spot from that of the higher pass normalizes the laser power and removes the contribution of contaminant gas and fringes in the fore-optics region. These initial results show that this imaging method is particularly advantageous for multi-channel laser spectrometers, and, once the image field is analyzed, pixel selection can be used to minimize data rate and volume collection requirements. This technique could be beneficial to enhanced-cavity detection schemes.

Evaluation of Tomato-Based Packing Material for Retention of Ammonia, Nitrous Oxide, Carbon Dioxide and Methane in Gas Phase Biofilters: A Laboratory Study

Biofilters are an effective air pollution control technology to break down gaseous contaminants and produce innocuous end products. This laboratory study aimed to evaluate a biofilter media, mainly composed by tomato waste, as packing material to reduce NH3, N2O, CO2 and CH4 losses from stored pig slurry. Three mixtures of packing materials, with and without oxalic acid, were arranged in treatments, namely: mixture of tomato waste, pine bark and agricultural compost; mixture of tomato waste and rice husk; tomato waste only. A control treatment (no biofilter) was also included. The experiments were conducted using a system of laboratory scale biofilters connected to jars filled with pig slurry and under a constant airflow rate. The gas concentrations were measured for 14 days and the physicochemical of the packing materials were assessed. Results showed that biofilter media mixtures had a potential for NH3 retention ranging from 51 to 77% and the addition of oxalic acid to these biofilters increased NH3 retention to 72–79%. Additionally, the biofilter media mixtures with and without oxalic acid showed a potential retention for CH4 (29–69%) but not for N2O, yet with no impact on the global warming potential. It can be concluded that tomato based biofilters had the potential to reduce gaseous emissions from slurry.

Highly selective H2S gas sensor based on WO3-coated SnO2 nanowires

The enhancement of the H2S gas-sensing performance of SnO2 nanowires is vital for practical application. In this study, H2S gas sensors based on WO3-coated SnO2 nanowires were fabricated through a two-step process, namely, the chemical vapor deposition of SnO2 nanowires and then coating with WO3 by sputtering method. The morphology and crystal structures of the SnO2 nanowires coated with WO3 were investigated by field-emission scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The H2S gas-sensing properties of the fabricated sensors were tested at temperatures of 150–250 °C. The SnO2 nanowires coated with 5 nm WO3 showed the best response to low-concentration H2S gas (0.1–1 ppm). At the optimal working temperature of 200 °C, the sensor had a sensitivity of 177 toward 1 ppm H2S with good selectivity over the contamination of NO2, NH3, H2, and CO gases. We also discussed the gas-sensing mechanism of the fabricated sensor based on the n–n heterojunction between n-type SnO2 and n-type WO3, which formed a thick depletion layer and thus enhanced the sensitivity to H2S.

Assessment of Factors Affecting the Amount of Food Waste in Households Run by Polish Women Aware of Well-Being

Food waste is a pressing problem in Western countries. Increased food waste production directly affects environmental changes and pollution, including greenhouse gas emissions and contamination with packaging. In Poland, 9.2 million tons of food is lost annually, 53% of which is produced by consumers. To minimize food waste by consumers, it is necessary to understand the factors affecting the behaviors associated with food wasting. This work is focused on investigating the causes and behaviors related to food wasting, and determining the kinds of food that are wasted in Polish households run by women that possess a high awareness of well-being. It was found that most of the respondents who took part in the survey admitted that their households did waste food. It was shown that there is a positive correlation between the number of people living in a household and the amount of food wasted. It was also confirmed that age has an impact on the amount of food discarded by Polish women, because respondents over 37 years of age wasted less food and more often declared a lack of wasting compared to others. In households, fresh food with short expiry dates, including vegetables, fruit, bread, and meat, was wasted the most. The most important factors directly influencing the amount of wasted food were: purchasing too much food, a lack of expiry-date control, a lack of planning of purchases and menus, and a lack of ideas for using food residues. The main element affecting waste is purchasing too much food, most often resulting from susceptibility to promotions, willingness to buy in stock, and a lack of prior planning. Understanding the mechanisms of waste allows households to take actions to effectively reduce it, and therefore ensure greater food security in the world.

Predictive Boundary Tracking Based on Motion Behavior Learning for Continuous Objects in Industrial Wireless Sensor Networks

The diffusion of toxic gas, biochemical material, and radio-active contamination – known as continuous objects – endangers the safe production of the petrochemical and nuclear industries. To mitigate these well known hazards, the new paradigm of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">industrial wireless sensor networks</i> (IWSNs) shows great potential in monitoring evolving hazardous phenomena in unfriendly industrial fields. In order to prolong the lifetime of these networks, existing research focuses on energy-efficient boundary nodes selection. However, sensor state cannot be scheduled proactively, due to the difficulty in predicting the spatiotemporal evolution of diffusive hazards. In this article, we propose a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">motion behavior learning predictive tracking</i> (MBLPT) algorithm for continuous objects in IWSNs. Considering the relatively unpredictable patterns exhibited by continuous objects, the MBLPT uses a data-driven approach for motion state recognition, and then utilizes <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Bayesian model averaging</i> (BMA) for future boundary prediction. The prediction of the MBLPT provides the knowledge for establishing a wake-up zone, in which standby nodes are activated in advance to participate in tracking the upcoming boundary. Simulation results demonstrate that the MBLPB achieves superior energy efficiency while keeping effective tracking accuracy.

Experimental research on influence of gas adsorption on secondary electron emission of copper surface

Secondary electron (SE) emission is a superficial physical phenomenon. The range of SEs excited in materials which are finally emitted from the surface is generally within a few tens of nanometers. SE emission from materials by electron irradiation has great dependence on surface quality, such as gas adsorption, oxidation, contamination, and morphology. In this paper, the influence of surface adsorption of N2, O2, Ar and air on SE yield (SEY) and the SE spectrum (SES) of copper was investigated by experiment. The measured SEY and SES were compared before and after the copper surface was sputtered by Ar ions. The results show that gas adsorption could increase SEY, and air adsorption lead to the maximum increase, Ar adsorption the minimum. Meanwhile, the relationship between the SES and the SEY was deduced and validated by the experiment. It was also found in the experiment that the Ar ion sputtering or heating alone can effectively reduce the SEY, while heating the sample after Ar ion sputtering increases SEY. The reasons for the variation of the SEYs with gas adsorption, sputtering and heating are preliminarily explained with the help of in-situ XPS. Accordingly, the research helps to further reveal the mechanism of SEE influenced by complex superficial factors.

Influence of Concentration Distribution on Cross Diffusion Level in Building Room

The relationship of contaminant gas concentration distribution influence on cross diffusion character and level among temperature, humidity and contaminant gas concentration was obtained according to the non-equilibrium thermodynamic theory. The cross diffusion character and level under different contaminant gas concentration distribution were discussed, combining real temperature and humidity in building room. The results show that temperature grads and vapor mass grads are less than zero when contaminant gas mass grads and additional diffusion coefficient are both positive or negative, otherwise the two grads are more than zero. And the higher the initial temperature and humidity levels, the greater the absolute values of temperature grads and vapor mass grads, with the same contaminant gas mass grads and additional diffusion coefficient. While the influence of initial temperature level is finite, and that of initial humidity level is remarkable.

Analysis of the circumstances of methane explosions at the mines of Ukraine

The article analyzes and summarizes the circumstances of methane explosions in mines of Ukraine over the past 50 years, which occurred as a result of the formation of dangerous methane concentrations in the outgoing jets of mining areas. Both explosions in excavation areas and explosions associated with gas contamination of areas that occurred outside of them were reflected. The typification of methane explosions is carried out and the schemes of their occurrence are determined, the classification of which is based on the causes of the formation of an explosive atmosphere. These include explosions: in mined-out areas, in case of ventilation disturbances, in local accumulations of methane, in the degassing of areas after ventilation disturbances, in the degassing of dead-end workings within excavation areas, with increased gas release, as well as explosions caused by gas contamination of excavation areas that arose behind their limits. It has been established that the main reasons for the formation of an explosive atmosphere in mining areas during methane explosions are disturbances in ventilation, accumulation of methane in mined-out areas and the formation of local accumulations. Data on the most serious accidents from methane explosions in the history of the coal industry in Ukraine are given separately. It is concluded that stationary automatic equipment for monitoring the concentration of methane does not always make it possible to recognize a hazardous situation in mining areas in case of disturbances in ventilation and due to other causes of gas pollution. Several other gas-dynamic phenomena that have occurred in recent years have also been analyzed; these include endogenous fires from spontaneous combustion of coal during mining operations in an extremely stressed coal-rock mass. As recommendations, it was noted that to improve the efficiency of air-gas control and reduce the likelihood of methane explosions, the following measures are advisable: control of air consumption in mining areas of mines of category III for methane and higher, monitoring of carbon monoxide in the initial ventilation jets of mining areas during the development of coal seams prone to spontaneous combustion, improving the organization of notification of underground personnel about cases of gas contamination of mine workings. Keywords: coal mines, mining areas, methane, explosions, endogenous fires.

Indoor Climate and Energy Model Calibration with Monitored Data of a Naturally Ventilated Dairy Barn in a Cold Climate

HighlightsIndoor climate and energy model of a dairy barn is constructed and calibrated with collected data.Long-term monitoring of indoor conditions and electricity consumption greatly facilitates the model calibration process.Statistical benchmarks given by guidelines confirm the usability and reliability of the model.Abstract. This study demonstrates an application of ICE model calibration by using sensor building metrics in a naturally ventilated dairy house in a cold climate. The barn, at the time of the study, had 70 lactating cows and 30 calves with a total animal area of 1922 m2 and other auxiliary areas of 268 m2. Indoor condition data were collected by four integrated sensors inside the barn for six months, from March to August 2019. IDA ICE 4.8 SP1 simulation software was used to build and simulate the model, with calibration steps conducted first manually, then statistically. Actual weather and indoor condition data during the monitored period were used for calibration; statistical indices of the calibrated model were confirmed by the benchmarks given from ASHRAE Guideline 14-2014, IPMVP version 2016, and FEMP version 4.0 2015. The yielded result was a baseline ICE model, which can be further utilized in the study of energy conservation measures (ECMs), retrofitting feasibility, and ammonia and other contaminant gas emission mitigation. The abovementioned calibration practice and the proposals built on it open a pathway to achieve a higher level of energy efficiency for this type of livestock building. Keywords: Cold weather, Dairy farms, Model calibration, Natural ventilation.

Rapid Cycle Temperature Swing Adsorption Process Using Solid Structured Sorbent for CO2 capture from Cement Flue Gas

Concrete is the most widely used man-made material in the world. The production process of cement, a key component of concrete, contributes significantly to CO2 emissions. Every year, over 4 billion tonnes of cement are produced, releasing approximately 7%-8% of global CO2 emissions [1]. Cement flue gas, processes and raw materials, contain around 16% CO2 and 7-10% O2 and NOX /SOX (100-300 ppm), contingent on the fuel type. High amounts of NOX/SOX are a significant challenge for any carbon capture system. The presence of high O2 concentration in the emitted gas stream can chemically degrade typical amines via production of amides or other oxide derivatives. Therefore, it is crucial to conduct preliminary studies at a pilot scale using real cement flue gas conditions to develop a viable technology and accurate techno-economic analysis for large plants (1 million+ tonnes of captured CO2 per year). Svante (formerly Inventys) has a strong patent portfolio on Rapid Cycle Temperature Swing Adsorption (RC-TSA) processes using structured adsorbents, steam-assisted direct regeneration with fast kinetics (< 1.5 mins cycle time) as an alternative to traditional liquid amine technologies. This project utilized scaled up CALF-20 sorbent, one of the first Metal Organic Frameworks (MOFs) used in an industrial CO2 capture project. This MOF is robust with regards to steam, O2 and acidic contaminant gases (such a NOX/SOX) which make it an ideal candidate for the cement CO2 capture application. This article discusses efforts to scale up the CALF-20 MOF sorbent from lab scale to ton scale. A review of CALF-20 performance after 2300 hrs of VeloxoTherm™ capture process results on a boiler flue gas doped with CO2 and Air to simulate Cement kiln flue gas at 0.1 TPD capacity is presented. Also included are results from Phase 1 of the cement project related to NOX/SOX stability tests on CALF-20 sorbent.

Synthesis and Stability of Metal-organic Frameworks (MOFs) Photocatalysts for the Removal of Persistent Organic Pollutants (POPs) from Wastewater

Background: The removal of persistent organic pollutants (POPs) from the contaminated water by employing photocatalytic adsorption is considered as one of the most emerging technologies due to its’ cost- and energy-effectiveness. It has attracted significant attention of global researchers to process the world’s wastewater. Methods: Among different adsorbents, the metal-organic frameworks (MOFs) have demonstrated remarkable potential and a bright future perspective in the photocatalytic-based adsorptive removal of POPs from wastewater. This review deals with the introduction of MOFs and contaminations in wastewater, followed by the synthesis method for MOFs and their properties. The review is extended to the review of mechanisms for the photocatalytic adsorption along with the recent progress in removal of persistent toxic substances, pesticides, herbicides, phenols, and antibiotics. Furthermore, the future challenges in this promising area are also discussed. Results: Much research work has been done in the area of photocatalytic adsorptive removal of the POPs using the MOFs due to their significant structural and texture properties. Substantial research efforts have been carried out to functionalize the MOFs in order to improve their adsorption potential. Overall, this review demonstrated that the MOFs could be applied successfully for the photocatalytic adsorptive removal of the POPs from contaminated water. Conclusion: Despite the bright future perspective of the MOFs, there are some issues that need to be accounted for: The development of MOFs with redox-active metals and/or organic functionalized ligands, MOFs application for the photocatalytic adsorptive removal of the gaseous contaminants, indepth understanding of the mechanism of the photocatalytic adsorptive removal of the POPs, and the application of the MOFs for photocatalytic adsorptive removal of the POPs in real environmental conditions. The fast development of the MOFs in the recent era indicates a bright future perspective in spite of the challenges in this area.

Verification of three-dimensional mathematical modeling when calculating the combustion of hydrocarbon fuel in an experimental cylindrical furnace enriched with a plasma fuel system

In this work, the operation of the boiler in traditional and plasma-activated conditions is investigated. To test the possibility of modeling the Cinar ICE program with an understanding of the physical mechanism of the processes of electrothermochemical fuel preparation (ETCF) and combustion, a study of coal combustion in an experimental furnace with a thermal power of 3 MW equipped with a plasma fuel system was carried out. To study the combustion process of an air mixture that had undergone preliminary plasma preparation for combustion, one-dimensional plasma-coal and three-dimensional computer programs Cinar ICE were used, which study in detail the mechanism of the kinetics of thermochemical exchange in a two-phase flow, where the plasma fuel source is located, and the exact geometry of the furnace, and the kinetics of the process сombustion of coal particles. As a result of calculations, the distribution of temperature, velocity of gas and particles in the process of ETCPT, the concentration of gas-phase mixtures, the concentration of carbon and the degree of gas contamination in the remainder of alloyed coal were determined. It was found that the plasma activation of combustion affects the thermal characteristics of the Torch, the mechanical non-combustible fuel residue and the concentration of nitrogen oxide at the outlet from the furnace. It has been proven that when simulating coal combustion, it is possible to achieve an effective description of the process using the Cinar ICE program.

Numerical Study on Indoor Environmental Quality in a Room Equipped with a Combined HRV and Radiator System

Heat recovery ventilation (HRV) systems can be integrated with an additional air heater in buildings with low energy demand in order to cover space heating demand. The employment of coupled HRV-heater systems is, therefore, gaining increasing interest for the improvement of the indoor environmental quality (IEQ), as well as the reduction of ventilation energy loss. The present paper analyses the efficacy of a HRV system, coupled with a low-temperature radiator, in satisfying the IEQ indices inside a retrofitted dormitory room. A computational fluid dynamic (CFD) model based on the finite volume method is established to investigate IEQ characteristics including indoor air quality and thermal comfort condition. The presented CFD code provides a practical tool for a comprehensive investigation of the IEQ indices in spaces employing a coupled HVAC system. In an analysis of indoor air quality, parameters such as age of the air, air change efficiency, and ventilation efficiency in removal of gaseous contaminants, namely VOCs and CO2, are evaluated. The results obtained by the numerical model allow addressing the interaction between HRV and radiator systems and its effects on airflow field. The results show the decrease of the indoor operative temperature with increment of the supply air flow rate, which is mainly due to the decreased thermal efficiency of the HRV system. The obtained results indicate that, while higher ventilation rates can significantly decrease the age of the air and gaseous contaminants level, at the same time, it would cause a local discomfort in some parts of the room.

New technique for high-precision, simultaneous measurements of CH&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;, N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O and CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; concentrations; isotopic and elemental ratios of N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;, O&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; and Ar; and total air content in ice cores by wet extraction

Abstract. Air in polar ice cores provides unique information on past climatic and atmospheric changes. We developed a new method combining wet extraction, gas chromatography and mass spectrometry for high-precision, simultaneous measurements of eight air components (CH4, N2O and CO2 concentrations; δ15N, δ18O, δO2∕N2 and δAr∕N2; and total air content) from an ice-core sample of ∼ 60 g. The ice sample is evacuated for ∼ 2 h and melted under vacuum, and the released air is continuously transferred into a sample tube at 10 K within 10 min. The air is homogenized in the sample tube overnight at room temperature and split into two aliquots for mass spectrometric and gas chromatographic measurements. Care is taken to minimize (1) contamination of greenhouse gases by using a long evacuation time, (2) consumption of oxygen during sample storage by a passivation treatment on sample tubes, and (3) fractionation of isotopic ratios with a long homogenization time for splitting. Precision is assessed by analyzing standard gases with artificial ice and duplicate measurements of the Dome Fuji and NEEM ice cores. The overall reproducibility (1 SD) of duplicate ice-core analyses are 3.2 ppb, 2.2 ppb and 2.9 ppm for CH4, N2O and CO2 concentrations; 0.006 ‰, 0.011 ‰, 0.09 ‰ and 0.12 ‰ for δ15N, δ18O, δO2∕N2 and δAr∕N2; and 0.63 mLSTP kg−1 for total air content, respectively. Our new method successfully combines the high-precision, small-sample and multiple-species measurements, with a wide range of applications for ice-core paleoenvironmental studies.