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Dherbecourt, Jean-Baptiste, Jean-Michel Melkonian, Antoine Godard, Vincent Lebat, Nicolas Tanguy, Cedric Blanchard, Stéphanie Doz et al. "NAOMI GAZL: A Multispecies DIAL Tested on the TADI Gas Leak Simulation Facility". EPJ Web of Conferences 237 (2020): 03016. http://dx.doi.org/10.1051/epjconf/202023703016.
Testo completoAbstract (sommario):
We report on a direct detection differential absorption lidar (DIAL), designed for remote detection of CH4 and CO2. The system is based on a single-frequency optical parametric oscillator/amplifier system, tunable in the 1.57-1.65 µm range. The DIAL system, called NAOMI GAZL, was tested on a controlled gas release facility in October 2018.
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Kuze, Akihiko, Nobuhiro Kikuchi, Fumie Kataoka, Hiroshi Suto, Kei Shiomi e Yutaka Kondo. "Detection of Methane Emission from a Local Source Using GOSAT Target Observations". Remote Sensing 12, n. 2 (13 gennaio 2020): 267. http://dx.doi.org/10.3390/rs12020267.
Testo completoAbstract (sommario):
Emissions of atmospheric methane (CH4), which greatly contributes to radiative forcing, have larger uncertainties than those for carbon dioxide (CO2). The Thermal And Near-infrared Sensor for carbon Observation Fourier-Transform Spectrometer (TANSO-FTS) onboard the Greenhouse gases Observing SATellite (GOSAT) launched in 2009 has demonstrated global grid observations of the total column density of CO2 and CH4 from space, and thus reduced uncertainty in the global flux estimation. In this paper, we present a case study on local CH4 emission detection from a single-point source using an available series of GOSAT data. By modifying the grid observation pattern, the pointing mechanism of TANSO-FTS targets a natural gas leak point at Aliso Canyon in Southern California, where the clear-sky frequency is high. To enhance local emission estimates, we retrieved CO2 and CH4 partial column-averaged dry-air mole fractions of the lower troposphere (XCO2 (LT) and XCH4 (LT)) by simultaneous use of both sunlight reflected from Earth’s surface and thermal emissions from the atmosphere. The time-series data of Aliso Canyon showed a large enhancement that decreased with time after its initial blowout, compared with reference point data and filtered with wind direction simulated by the Weather Research and Forecasting (WRF) model.
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Russ, Tamara, Joseph R. Stetter, Eric Luong, Avadhkumar Jitubhai Patel e Winncy Du. "(Invited) Detection, Location and Quantification of H2 Gas Leaks Based on Data Collected with Electrochemical Sensors in a Specifically Designed Test Chamber". ECS Meeting Abstracts MA2024-01, n. 51 (9 agosto 2024): 2756. http://dx.doi.org/10.1149/ma2024-01512756mtgabs.
Testo completoAbstract (sommario):
Hydrogen is one of the most important energy gases as it is carbon free and therefore can result in the emission reduction of the greenhouse gas CO2. However, hydrogen itself is a secondary greenhouse gas. As a secondary greenhouse gas, hydrogen does not directly add to global warming by entrapping heat. Instead, it reacts with molecules in the atmosphere that are needed to remove the greenhouse gas CH4. CH4 is comparably short-lived in the atmosphere with approximately 10 years compared to CO2 which can last in the atmosphere for centuries. However, CH4 traps at least 100 times as much heat as CO2. Considering the difference in heat capacities of CH4 and CO2, combined with the difference in lifetime, if the same amount of CH4 and CO2 were to be released into the atmosphere at the same time, the global warming effect of CH4 would be approximately 28 times higher than the warming effect of CO2. This means, by releasing hydrogen in the atmosphere, the global warming effect is indirectly enhanced by increasing the lifetime of CH4. Therefore, it is essential to be able to detect, locate and quantify hydrogen leaks right away. Due to the ever-growing hydrogen infrastructure including production facilities, transportation systems like pipelines, as well as storage facilities and user end stations, it is essential to create low-cost, low-power sensors that can be deployed in high numbers. Electrochemical sensors have the potential to fulfill all the needed criteria and are already used for the detection of hydrogen. However, in order to use these sensors to not only detect the leak, but also to locate and quantify the amount of hydrogen that leaked into the atmosphere, additional models and algorithms are needed. To our knowledge, no system currently exists on the market that can be used to fulfill all three tasks. We built a test chamber that enabled us to evaluate H2 leaks and to collect data with electrochemical sensors in a controlled room and environment. The chamber has the size of 800 x 400 x 450 mm3 with a total volume of 144 L. We placed seven of our commercial electrochemical sensors that can detect 0 – 250 ppm hydrogen at different positions inside the box. The box was equipped with one gas inlet and one gas outlet to ensure pressure stability inside the box during our leak test. The inlet was connected to a gas tube which was connected to two mass flow controllers as well as to an outlet tube via a three-way valve. This way, it could be ensured that the gas stream had a stable volume and a constant speed. We released controlled amounts of hydrogen into the box and collected the data with our seven sensors. We were able to see a location-dependent sensor response over time for a 1 second leak of H2 which indicates the capability of such a sensor system to be used for the location of a leak. Quantifying hydrogen is a very complex issue. It requires extremely accurate readings and an intelligent algorithm that is capable to use the reading from multiple sensors and turn that into a mass of hydrogen leaked or leaking. The extremely accurate reading is difficult because the zero and span readouts from the electrochemical sensor is dependent on temperature as well as humidity. This means that the readout zero and span will have to be compensated for both temperature and humidity. While we currently use algorithms to compensate for temperature, we found that these algorithms are not good enough when the sensors are used to measure concentrations in the low-ppm or ppb range. We are researching AI and other computational means to include both temperature and humidity in the compensation algorithms and how including both variables in the compensation process can improve the sensors performance at low concentrations. Both the H2 sensor and its deployment capabilities are technologically and economically significant to the rapidly expanding H2 market for protecting human health, the environment, stemming expensive product losses and promoting efficient use.
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Yang, Mingxi, John Prytherch, Elena Kozlova, Margaret J. Yelland, Deepulal Parenkat Mony e Thomas G. Bell. "Comparison of two closed-path cavity-based spectrometers for measuring air–water CO<sub>2</sub> and CH<sub>4</sub> fluxes by eddy covariance". Atmospheric Measurement Techniques 9, n. 11 (18 novembre 2016): 5509–22. http://dx.doi.org/10.5194/amt-9-5509-2016.
Testo completoAbstract (sommario):
Abstract. In recent years several commercialised closed-path cavity-based spectroscopic instruments designed for eddy covariance flux measurements of carbon dioxide (CO2), methane (CH4), and water vapour (H2O) have become available. Here we compare the performance of two leading models – the Picarro G2311-f and the Los Gatos Research (LGR) Fast Greenhouse Gas Analyzer (FGGA) at a coastal site. Both instruments can compute dry mixing ratios of CO2 and CH4 based on concurrently measured H2O, temperature, and pressure. Additionally, we used a high throughput Nafion dryer to physically remove H2O from the Picarro airstream. Observed air–sea CO2 and CH4 fluxes from these two analysers, averaging about 12 and 0.12 mmol m−2 day−1 respectively, agree within the measurement uncertainties. For the purpose of quantifying dry CO2 and CH4 fluxes downstream of a long inlet, the numerical H2O corrections appear to be reasonably effective and lead to results that are comparable to physical removal of H2O with a Nafion dryer in the mean. We estimate the high-frequency attenuation of fluxes in our closed-path set-up, which was relatively small ( ≤ 10 %) for CO2 and CH4 but very large for the more polar H2O. The Picarro showed significantly lower noise and flux detection limits than the LGR. The hourly flux detection limit for the Picarro was about 2 mmol m−2 day−1 for CO2 and 0.02 mmol m−2 day−1 for CH4. For the LGR these detection limits were about 8 and 0.05 mmol m−2 day−1. Using global maps of monthly mean air–sea CO2 flux as reference, we estimate that the Picarro and LGR can resolve hourly CO2 fluxes from roughly 40 and 4 % of the world's oceans respectively. Averaging over longer timescales would be required in regions with smaller fluxes. Hourly flux detection limits of CH4 from both instruments are generally higher than the expected emissions from the open ocean, though the signal to noise of this measurement may improve closer to the coast.
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Halley, Sleight, Kannan Ramaiyan, James Smith, Robert Ian, Kamil Agi, Fernando H. Garzon e Lok-kun Tsui. "Mixed Potential Electrochemical Sensors for Natural Gas Leak Detection – Field Testing of Portable Sensor Package". ECS Meeting Abstracts MA2023-01, n. 52 (28 agosto 2023): 2604. http://dx.doi.org/10.1149/ma2023-01522604mtgabs.
Testo completoAbstract (sommario):
According to the EPA, methane (CH4) emissions from oil and gas infrastructure accounted for 211 million metric tons of CO2 equivalent in 2020 [1]. Actual emissions may exceed this by a factor of three [2]. Current natural gas leak detection technologies largely consist of optical sensors such as IR spectrometers [3]. Optical sensors have high sensitivity, but the high cost and fragility of these sensors limit practical applications and continuous monitoring in the field. Mixed potential electrochemical sensors (MPES) are low cost, robust, selective and sensitive, making them a viable option for continuous natural gas leak detection [4]. While we have previously reported on the development of these sensors for natural gas detection in the laboratory, it is necessary to evaluate how these sensors perform in relevant environments. The MPES device consists of La0.87Sr0.13CrO3 (LSC), indium tin oxide (ITO, In2O3 90 wt%, SnO2 10 wt%), and Au sensing electrodes with a Pt pseudo-reference electrode, bridged by 3 mol% YSZ solid electrolyte. A low ionic conductivity magnesia stabilized zirconia (MSZ) substrate is used to enhance sensitivity with a demonstrated limit of detection (LOD) of < 40 ppm. The sensor is integrated with an internet of things (IoT) data collection and transmission package developed by SensorComm Technologies. Field testing was performed at Colorado State University’s Methane Emission Technology Evaluation Center (METEC). The sensors’ capability of detecting buried pipeline leaks was investigated by varying the leak rate from 7.2 SLPM to 37 SLPM, lateral sensor distance from 0 meters to 3 meters, and vertical distance from 0 meters to 0.28 meters (Figure 1). Machine learning methods were applied to a training dataset collected in the laboratory to quantify the CH4 concentration. These results serve as a first demonstration that a low-cost mixed potential electrochemical sensor system can successfully detect underground pipeline emissions and quantify CH4 concentrations that are in agreement with previously published results [6] collected using more complex and costly methods. References: [1] O. US EPA, “Estimates of Methane Emissions by Segment in the United States,” Aug. 27, 2018. https://www.epa.gov/natural-gas-star-program/estimates-methane-emissions-segment-united-states (accessed Dec. 08, 2022). [2] A. J. Marchese et al., “Methane Emissions from United States Natural Gas Gathering and Processing,” Environ. Sci. Technol., vol. 49, no. 17, pp. 10718–10727, Sep. 2015, doi: 10.1021/acs.est.5b02275. [3] T. Aldhafeeri, M.-K. Tran, R. Vrolyk, M. Pope, and M. Fowler, “A Review of Methane Gas Detection Sensors: Recent Developments and Future Perspectives,” Inventions, vol. 5, no. 3, Art. no. 3, Sep. 2020, doi: 10.3390/inventions5030028. [4] F. H. Garzon, R. Mukundan, and E. L. Brosha, “Solid-state mixed potential gas sensors: theory, experiments and challenges,” Solid State Ion., vol. 136–137, pp. 633–638, Nov. 2000, doi: 10.1016/S0167-2738(00)00348-9. [5] S. Halley, L. Tsui, and F. Garzon, “Combined Mixed Potential Electrochemical Sensors and Artificial Neural Networks for the Quantificationand Identification of Methane in Natural Gas Emissions Monitoring,” J. Electrochem. Soc., vol. 168, no. 9, p. 097506, Sep. 2021, doi: 10.1149/1945-7111/ac2465. [6] B. A. Ulrich, M. Mitton, E. Lachenmeyer, A. Hecobian, D. Zimmerle, and K. M. Smits, “Natural Gas Emissions from Underground Pipelines and Implications for Leak Detection,” Environ. Sci. Technol. Lett., vol. 6, no. 7, pp. 401–406, Jul. 2019, doi: 10.1021/acs.estlett.9b00291. Figure 1: Sensor response to various heights above a simulated buried pipeline leak on two successive days of testing (a and b), and estimated CH4 concentrations from sensor data (c). Figure 1
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Zellweger, Christoph, Lukas Emmenegger, Mohd Firdaus, Juha Hatakka, Martin Heimann, Elena Kozlova, T. Gerard Spain, Martin Steinbacher, Marcel V. van der Schoot e Brigitte Buchmann. "Assessment of recent advances in measurement techniques for atmospheric carbon dioxide and methane observations". Atmospheric Measurement Techniques 9, n. 9 (26 settembre 2016): 4737–57. http://dx.doi.org/10.5194/amt-9-4737-2016.
Testo completoAbstract (sommario):
Abstract. Until recently, atmospheric carbon dioxide (CO2) and methane (CH4) measurements were made almost exclusively using nondispersive infrared (NDIR) absorption and gas chromatography with flame ionisation detection (GC/FID) techniques, respectively. Recently, commercially available instruments based on spectroscopic techniques such as cavity ring-down spectroscopy (CRDS), off-axis integrated cavity output spectroscopy (OA-ICOS) and Fourier transform infrared (FTIR) spectroscopy have become more widely available and affordable. This resulted in a widespread use of these techniques at many measurement stations. This paper is focused on the comparison between a CRDS "travelling instrument" that has been used during performance audits within the Global Atmosphere Watch (GAW) programme of the World Meteorological Organization (WMO) with instruments incorporating other, more traditional techniques for measuring CO2 and CH4 (NDIR and GC/FID). We demonstrate that CRDS instruments and likely other spectroscopic techniques are suitable for WMO/GAW stations and allow a smooth continuation of historic CO2 and CH4 time series. Moreover, the analysis of the audit results indicates that the spectroscopic techniques have a number of advantages over the traditional methods which will lead to the improved accuracy of atmospheric CO2 and CH4 measurements.
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Zaini, Zaini, e Taffany Hudalil Alvy. "Design of Monitoring System for Hazardous Gas and Fire Detection In Building Based On Internet of Things". Andalas Journal of Electrical and Electronic Engineering Technology 2, n. 1 (24 giugno 2022): 13–20. http://dx.doi.org/10.25077/ajeeet.v2i1.20.
Testo completoAbstract (sommario):
Fires and gas leaks are events that still occur frequently. This incident is usually caused by various factors including leakage of LPG gas cylinders, cigarette butts that are disposed of carelessly, short circuits of electric current and so on. Generally, fires and gas leaks can only be detected if the fire has already grown or a lot of smoke comes out of the building. Therefore, a monitoring system for detecting dangerous gases and fires in buildings based on the Internet of Things was created that can monitor the condition of the building through a website as well as send notifications to the Telegram application on smartphones. The detection system implemented uses a flame sensor as a fire detector, an MQ-2 gas sensor as a detector of hazardous gases (CO, CO2, and CH4), and NodeMCU as a module to transmit data. The system will work continuously in real time, if gas is detected that exceeds the threshold or a fire is detected, the system will send a notification to Telegram and the website will display the value and status of the sensor and a map of the area where the fire or gas leak occurred. The results of the detection system created to be able to provide solutions so that cases of fire and gas leaks can be handled early by detecting signs of fire or gas leaks and sending the information to users via the website and notifications.
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Dowd, Emily, Alistair J. Manning, Bryn Orth-Lashley, Marianne Girard, James France, Rebecca E. Fisher, Dave Lowry et al. "First validation of high-resolution satellite-derived methane emissions from an active gas leak in the UK". Atmospheric Measurement Techniques 17, n. 5 (18 marzo 2024): 1599–615. http://dx.doi.org/10.5194/amt-17-1599-2024.
Testo completoAbstract (sommario):
Abstract. Atmospheric methane (CH4) is the second-most-important anthropogenic greenhouse gas and has a 20-year global warming potential 82 times greater than carbon dioxide (CO2). Anthropogenic sources account for ∼ 60 % of global CH4 emissions, of which 20 % come from oil and gas exploration, production and distribution. High-resolution satellite-based imaging spectrometers are becoming important tools for detecting and monitoring CH4 point source emissions, aiding mitigation. However, validation of these satellite measurements, such as those from the commercial GHGSat satellite constellation, has so far not been documented for active leaks. Here we present the monitoring and quantification, by GHGSat's satellites, of the CH4 emissions from an active gas leak from a downstream natural gas distribution pipeline near Cheltenham, UK, in the spring and summer of 2023 and provide the first validation of the satellite-derived emission estimates using surface-based mobile greenhouse gas surveys. We also use a Lagrangian transport model, the UK Met Office's Numerical Atmospheric-dispersion Modelling Environment (NAME), to estimate the flux from both satellite- and ground-based observation methods and assess the leak's contribution to observed concentrations at a local tall tower site (30 km away). We find GHGSat's emission estimates to be in broad agreement with those made from the in situ measurements. During the study period (March–June 2023) GHGSat's emission estimates are 236–1357 kg CH4 h−1, whereas the mobile surface measurements are 634–846 kg CH4 h−1. The large variability is likely down to variations in flow through the pipe and engineering works across the 11-week period. Modelled flux estimates in NAME are 181–1243 kg CH4 h−1, which are lower than the satellite- and mobile-survey-derived fluxes but are within the uncertainty. After detecting the leak in March 2023, the local utility company was contacted, and the leak was fixed by mid-June 2023. Our results demonstrate that GHGSat's observations can produce flux estimates that broadly agree with surface-based mobile measurements. Validating the accuracy of the information provided by targeted, high-resolution satellite monitoring shows how it can play an important role in identifying emission sources, including unplanned fugitive releases that are inherently challenging to identify, track, and estimate their impact and duration. Rapid, widespread access to such data to inform local action to address fugitive emission sources across the oil and gas supply chain could play a significant role in reducing anthropogenic contributions to climate change.
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Bonne, Jean-Louis, Ludovic Donnat, Grégory Albora, Jérémie Burgalat, Nicolas Chauvin, Delphine Combaz, Julien Cousin et al. "A measurement system for CO2 and CH4 emissions quantification of industrial sites using a new in situ concentration sensor operated on board uncrewed aircraft vehicles". Atmospheric Measurement Techniques 17, n. 14 (26 luglio 2024): 4471–91. http://dx.doi.org/10.5194/amt-17-4471-2024.
Testo completoAbstract (sommario):
Abstract. We developed and tested a complete measurement system to quantify CO2 and CH4 emissions at the scale of an industrial site based on the innovative sensor Airborne Ultra-light Spectrometer for Environmental Application (AUSEA), operated on board uncrewed aircraft vehicles (UAVs). The AUSEA sensor is a new light-weight (1.4 kg) open-path laser absorption spectrometer simultaneously recording in situ CO2 and CH4 concentrations at high frequency (24 Hz in this study) with precisions of 10 ppb for CH4 and 1 ppm for CO2 (when averaged at 1 Hz). It is suitable for industrial operation at a short distance from the sources (sensitivity up to 1000 ppm for CO2 and 200 ppm for CH4). Greenhouse gas concentrations monitored by this sensor throughout a plume cross section downwind of a source drive a simple mass balance model to quantify emissions from this source. This study presents applications of this method to different pragmatic cases representative of real-world conditions for oil and gas facilities. Two offshore oil and gas platforms were monitored for which our emissions estimates were coherent with mass balance and combustion calculations from the platforms. Our method has also been compared to various measurement systems (gas lidar, multispectral camera, infrared camera including concentrations and emissions quantification system, acoustic sensors, ground mobile and fixed cavity ring-down spectrometers) during controlled-release experiments conducted on the TotalEnergies Anomaly Detection Initiatives (TADI) test platform at Lacq, France. It proved suitable to detect leaks with emission fluxes down to 0.01 g s−1, with 24 % of estimated CH4 fluxes within the −20 % to +20 % error range, 80 % of quantifications within the −50 % to +100 % error range and all of our results within the −69 % to +150 % error range. Such precision levels are better ranked than current top-down alternative techniques to quantify CH4 at comparable spatial scales. This method has the potential to be operationally deployed on numerous sites and on a regular basis to evaluate the space- and time-dependent greenhouse gas emissions of oil and gas facilities.
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Hermon, Dedi. "Impacts of land cover change on climate trend in Padang Indonesia". Indonesian Journal of Geography 46, n. 2 (31 dicembre 2014): 138. http://dx.doi.org/10.22146/ijg.5783.
Testo completoAbstract (sommario):
ἀe purpose of this study was to analyze the trend of climate change through changes in the elements of Green House Gases (GHGs), includes the trend of CO2, N2O, and CH4. ἀe change of the extreme rainfall and temperature indices due to land cover change into developed area in Padang. IdentiḀcation and analysis trends of climate change and extreme climatic events were analyzed by using RclimDex the Expert Team for Climate Change Detection and Indices (ETCCDMI) technique. Where as the analysis and interpretation of land cover changes into developed area used Landsat TM 5 and Landsat 1985 7 ETM + of 2011 by ERDAS 9.2 GIS with the supervised classiḀcation method and GIS Matrix. ἀe results of the study provide informations of land cover changes into developed area at forest land (11,758.9 ha), shrub (3,337.3 ha), rice Ḁelds (5,977.1 ha), and garden (5,872.4 ha). It has an implication on increasing of the ele-ments of GHGs concentration such as CO2 (14,1 ppm), N2O (5,4 ppb) and CH4 (24,8 ppb). ἀis condition lead to an extreme temperature and presipitation indexs trends in Padang.
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Jacobs, Erik, Henry C. Bittig, Ulf Gräwe, Carolyn A. Graves, Michael Glockzin, Jens D. Müller, Bernd Schneider e Gregor Rehder. "Upwelling-induced trace gas dynamics in the Baltic Sea inferred from 8 years of autonomous measurements on a ship of opportunity". Biogeosciences 18, n. 8 (30 aprile 2021): 2679–709. http://dx.doi.org/10.5194/bg-18-2679-2021.
Testo completoAbstract (sommario):
Abstract. Autonomous measurements aboard ships of opportunity (SOOP) provide in situ data sets with high spatial and temporal coverage. In this study, we use 8 years of carbon dioxide (CO2) and methane (CH4) observations from SOOP Finnmaid to study the influence of upwelling on trace gas dynamics in the Baltic Sea. Between spring and autumn, coastal upwelling transports water masses enriched with CO2 and CH4 to the surface of the Baltic Sea. We study the seasonality, regional distribution, relaxation, and interannual variability in this process. We use reanalysed wind and modelled sea surface temperature (SST) data in a newly established statistical upwelling detection method to identify major upwelling areas and time periods. Large upwelling-induced SST decrease and trace gas concentration increase are most frequently detected around August after a long period of thermal stratification, i.e. limited exchange between surface and underlying waters. We found that these upwelling events with large SST excursions shape local trace gas dynamics and often lead to near-linear relationships between increasing trace gas levels and decreasing temperature. Upwelling relaxation is mainly driven by mixing, modulated by air–sea gas exchange, and possibly primary production. Subsequent warming through air–sea heat exchange has the potential to enhance trace gas saturation. In 2015, quasi-continuous upwelling over several months led to weak summer stratification, which directly impacted the observed trace gas and SST dynamics in several upwelling-prone areas. Trend analysis is still prevented by the observed high variability, uncertainties from data coverage, and long water residence times of 10–30 years. We introduce an extrapolation method based on trace gas–SST relationships that allows us to estimate upwelling-induced trace gas fluxes in upwelling-affected regions. In general, the surface water reverses from CO2 sink to source, and CH4 outgassing is intensified as a consequence of upwelling. We conclude that SOOP data, especially when combined with other data sets, enable flux quantification and process studies addressing the process of upwelling on large spatial and temporal scales.
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Leroux, Killian, e Lahouari Krim. "Thermal and photochemical study of CH3OH and CH3OH–O2 astrophysical ices". Monthly Notices of the Royal Astronomical Society 500, n. 1 (20 ottobre 2020): 1188–200. http://dx.doi.org/10.1093/mnras/staa3205.
Testo completoAbstract (sommario):
ABSTRACT Methanol, which is one of the most abundant organic molecules in the interstellar medium, plays an important role in the complex grain surface chemistry that is believed to be a source of many organic compounds. Under energetic processing such as ultraviolet (UV) photons or cosmic rays, methanol may decompose into CH4, CO2, CO, HCO, H2CO, CH3O and CH2OH, which in turn lead to complex organic molecules such as CH3OCHO, CHOCH2OH and HOCH2CH2OH through radical recombination reactions. However, although molecular oxygen and its detection, abundance and role in the interstellar medium have been the subject of many debates, few experiments on the oxidation of organic compounds have been carried out under interstellar conditions. The present study shows the behaviour of solid methanol when treated by UV light and thermal processing in oxygen-rich environments. Methanol has been irradiated in the absence and presence of O2 at different concentrations in order to study how oxidized complex organic molecules may form and also to investigate the O-insertion reaction in the C–H bound to form methanediol HOCH2OH through a CH3OH + O(1D) solid-state reaction. The adding of O2 in the thermal and photochemical reaction of solid methanol leads to the formation of O3, H2O and HO2, in addition to three main organics, HCOOH, CHOCHO and HOCH2OH. We show that in an O2-rich environment, species such as CO, CH4, HCO, CH3OH and CHOCH2OH are oxidized into CO2, CH3OH, HC(O)OO, HOCH2OH and CHOCHO, respectively, while HCOOH might be formed through the H2CO + O(3P) → (OH + HCO)cage → HCOOH hydrogen-abstraction reaction.
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Hazan, Lynn, Jérôme Tarniewicz, Michel Ramonet, Olivier Laurent e Amara Abbaris. "Automatic processing of atmospheric CO<sub>2</sub> and CH<sub>4</sub> mole fractions at the ICOS Atmosphere Thematic Centre". Atmospheric Measurement Techniques 9, n. 9 (22 settembre 2016): 4719–36. http://dx.doi.org/10.5194/amt-9-4719-2016.
Testo completoAbstract (sommario):
Abstract. The Integrated Carbon Observation System Atmosphere Thematic Centre (ICOS ATC) automatically processes atmospheric greenhouse gases mole fractions of data coming from sites of the ICOS network. Daily transferred raw data files are automatically processed and archived. Data are stored in the ICOS atmospheric database, the backbone of the system, which has been developed with an emphasis on the traceability of the data processing. Many data products, updated daily, explore the data through different angles to support the quality control of the dataset performed by the principal operators in charge of the instruments. The automatic processing includes calibration and water vapor corrections as described in the paper. The mole fractions calculated in near-real time (NRT) are automatically revaluated as soon as a new instrument calibration is processed or when the station supervisors perform quality control. By analyzing data from 11 sites, we determined that the average calibration corrections are equal to 1.7 ± 0.3 µmol mol−1 for CO2 and 2.8 ± 3 nmol mol−1 for CH4. These biases are important to correct to avoid artificial gradients between stations that could lead to error in flux estimates when using atmospheric inversion techniques. We also calculated that the average drift between two successive calibrations separated by 15 days amounts to ±0.05 µmol mol−1 and ±0.7 nmol mol−1 for CO2 and CH4, respectively. Outliers are generally due to errors in the instrument configuration and can be readily detected thanks to the data products provided by the ATC. Several developments are still ongoing to improve the processing, including automated spike detection and calculation of time-varying uncertainties.
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Jońca, Justyna, e Izabela Sówka. "GAS SENSORS BASED ON METAL OXIDE NANOPARTICLES AND THEIR APPLICATION FOR ENVIRONMENTALLY HAZARDOUS GASES DETECTION A MINI-REVIEW". Zeszyty Naukowe SGSP 85 (20 marzo 2023): 7–27. http://dx.doi.org/10.5604/01.3001.0016.3143.
Testo completoAbstract (sommario):
Hazardous gases have adverse effects on living organisms and the environment. They can beclassified into two categories, i.e. toxic gases (e.g. H2S, SO2, CO, NO2, NO and NH3) and greenhousegases (e.g. N2O, CH4 and CO2). Moreover, their presence in confined areas may lead to fireaccidents, cause serious health problems or even death. Therefore, monitoring of these substanceswith gas sensors allows assessing the quality of the atmosphere, helps avoiding accidents and saveslives. Metal oxide semiconductor gas sensors (MOS) are one of the most popular choices for theseapplications owing to their numerous advantages, i.e. high sensitivity, long lifetime and shortresponse time. However, these devices have their limitations as well. They exhibit baseline drift,sensor poisoning and poor selectivity. Although much has been done in order to deal with thoseproblems, the improvement of MOS sensors continues to attract researchers attention.The strict control of gas sensing materials preparation is one of the approaches that helps to improveMOS sensors performance. Nanomaterials have been found to be more suitable candidates for gasdetection than materials designed at microscale. Moreover, it was found that the regular and orderedmorphology of metal oxide nanostructures, their loading with noble metals, or the formation ofheterojunctionscan exert additional influence on the properties of these nanostructures andimprove their gas sensing performance, which will be described in the following sections of thispaper. Following a discussion of the operation principle of MOS sensors, a comprehensive review ofthe synthesis and application of metal oxide nanoparticles in the construction of the MOS sensorsdedicated for environmentally hazardous gases is presented. The paper discusses also present issuesand future research directions concerning application of nanotechnology for gas sensing.
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Yang, Shuting, Robert Talbot, Michael Frish, Levi Golston, Nicholas Aubut, Mark Zondlo, Christopher Gretencord e James McSpiritt. "Natural Gas Fugitive Leak Detection Using an Unmanned Aerial Vehicle: Measurement System Description and Mass Balance Approach". Atmosphere 9, n. 10 (1 ottobre 2018): 383. http://dx.doi.org/10.3390/atmos9100383.
Testo completoAbstract (sommario):
Natural gas is an abundant resource across the United States, of which methane (CH4) is the main component. About 2% of extracted CH4 is lost through leaks. The Remote Methane Leak Detector (RMLD)-Unmanned Aerial Vehicle (UAV) system was developed to investigate natural gas fugitive leaks in this study. The system is composed of three major technologies: miniaturized RMLD (mini-RMLD) based on Backscatter Tunable Diode Laser Absorption Spectroscopy (TDLAS), an autonomous quadrotor UAV and simplified quantification and localization algorithms. With a miniaturized, downward-facing RMLD on a small UAV, the system measures the column-integrated CH4 mixing ratio and can semi-autonomously monitor CH4 leakage from sites associated with natural gas production, providing an advanced capability in detecting leaks at hard-to-access sites compared to traditional manual methods. Automated leak characterization algorithms combined with a wireless data link implement real-time leak quantification and reporting. This study placed particular emphasis on the RMLD-UAV system description and the quantification algorithm development based on a mass balance approach. Early data were gathered to test the prototype system and to evaluate the algorithm performance. The quantification algorithm derived in this study tended to underestimate the gas leak rates and yielded unreliable estimations in detecting leaks under 7 × 10 − 6 m3/s (~1 Standard Cubic Feet per Hour (SCFH)). Zero-leak cases can be ascertained via a skewness indicator, which is unique and promising. The influence of the systematic error was investigated by introducing simulated noises, of which Global Positioning System (GPS) noise presented the greatest impact on leak rate errors. The correlation between estimated leak rates and wind conditions were investigated, and steady winds with higher wind speeds were preferred to get better leak rate estimations, which was accurate to approximately 50% during several field trials. High precision coordinate information from the GPS, accurate wind measurements and preferred wind conditions, appropriate flight strategy and the relative steady survey height of the system are the crucial factors to optimize the leak rate estimations.
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Owsley-Brown, Farrer, Martin J. Wooster, Mark J. Grosvenor e Yanan Liu. "Can the remote sensing of combustion phase improve estimates of landscape fire smoke emission rate and composition?" Atmospheric Measurement Techniques 17, n. 20 (29 ottobre 2024): 6247–64. http://dx.doi.org/10.5194/amt-17-6247-2024.
Testo completoAbstract (sommario):
Abstract. The proportion of flaming and smouldering (or smoldering) activity occurring in landscape fires varies with fuel type and fuel characteristics, which themselves are influenced by ecology, meteorology, time since the last fire, etc. The proportion of these combustion phases greatly influences the rate of fuel consumption and smoke emission, along with the chemical composition of the smoke, which influences the effects on the atmosphere. Earth observation (EO) has long been suggested as a way to remotely map combustion phase, and here we provide the first known attempt at evaluating whether such approaches can lead to the desired improvements in smoke emissions estimation. We use intensively measured laboratory burns to evaluate two EO approaches hypothesized to enable remote determination of combustion phase and concurrent measurements of the smoke to determine how well each is able to improve estimation of smoke emission rates, smoke composition, and the overall rate of fuel consumption. The first approach aims to estimate the sub-pixel “effective fire temperature”, which has been suggested to differ between flaming and smouldering combustion, and the second detects the potassium emission line (K-line) believed only to be present during flaming combustion. We find while the fire effective temperature approach can be suited to estimating fire radiative power (FRP), it does not significantly improve on current approaches to estimate smoke chemical makeup and smoke emission. The K-line approach does however provide these improvements when combined with the FRP data, improving the accuracy of the estimated CO2 emission rate by an average of 17±4 % and 42±15 %, respectively, depending on whether the K-line detection is used to simply classify the presence of flaming combustion or whether its magnitude is also used to estimate its relative proportion. Estimates of CO and CH4 emission rates were improved to a lesser extent than that of CO2, but the accuracy of the smoke modified combustion efficiency (MCE) estimates increased by 30±15 % and 46±10 %, respectively. MCE is correlated to the emissions factors (EFs) of many smoke constituents, so remotely deriving MCE provides a way to tailor these during smoke emissions calculations. Whilst we derived and tested our approaches on laboratory burns, we demonstrate their wider efficacy using airborne EO data of a boreal forest wildfire where we find that combined use of K-line and FRP data significantly changed estimated smoke MCE and CO2 and CO emission rates compared to the standard approach. Our findings suggest that satellite EO methods that jointly provide K-line and FRP data could enable marked improvements in the mapping of landscape fire combustion phase, fuel consumption, and smoke emissions rate and composition.
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Lin, Yueyu, Dexter Manalili, Amir Khodabakhsh e Simona M. Cristescu. "Real-Time Measurement of CH4 in Human Breath Using a Compact CH4/CO2 Sensor". Sensors 24, n. 4 (7 febbraio 2024): 1077. http://dx.doi.org/10.3390/s24041077.
Testo completoAbstract (sommario):
The presence of an elevated amount of methane (CH4) in exhaled breath can be used as a non-invasive tool to monitor certain health conditions. A compact, inexpensive and transportable CH4 sensor is thus very interesting for this purpose. In addition, if the sensor is also able to simultaneously measure carbon dioxide (CO2), one can extract the end-tidal concentration of exhaled CH4. Here, we report on such a sensor based on a commercial detection module using tunable diode laser absorption spectroscopy. It was found that the measured CH4/CO2 values exhibit a strong interference with water vapor. Therefore, correction functions were experimentally identified and validated for both CO2 and CH4. A custom-built breath sampler was developed and tested with the sensor for real-time measurements of CH4 and CO2 in exhaled breath. As a result, the breath sensor demonstrated the capability of accurately measuring the exhaled CH4 and CO2 profiles in real-time. We obtained minimum detection limits of ~80 ppbv for CH4 and ~700 ppmv for CO2 in 1.5 s measurement time.
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Widodo, Slamet, M. Miftakul Amin e Adi Sutrisman. "The Design of The Monitoring Tools Of Clean Air Condition And Dangerous Gas CO, CO2 CH4 In Chemical Laboratory By Using Fuzzy Logic Based On Microcontroller". E3S Web of Conferences 31 (2018): 10008. http://dx.doi.org/10.1051/e3sconf/20183110008.
Testo completoAbstract (sommario):
There are many phenomena that human are exposed to toxins from certain types such as of CO2, CO2 and CH4 gases. The device used to detect large amounts of CO, CO2, and CH4 gas in air in enclosed spaces using MQ 135 gas sensors of different types based on the three sensitivity of the Gas. The results of testing the use of sensors MQ 135 on the gas content of CO, CO2 and CH4 received by the sensor is still in the form of ppm based on the maximum ppm detection range of each sensor. Active sensor detects CO 120 ppm gas, CO2 1600 ppm and CH4 1ppm "standby 1" air condition with intermediate rotary fan. Active sensor detects CO 30 ppm gas, CO2 490 ppm and CH4 7 ppm "Standby 2" with low rotating fan output. Fuzzy rulebase logic for motor speed when gas detection sensor CO, CO2, and CH4 output controls the motion speed of the fan blower. Active sensors detect CO 15 ppm, CO2 320 ppm and CH4 45 ppm "Danger" air condition with high fan spin fan. At the gas level of CO 15 ppm, CO2 390 ppm and CH4 3 ppm detect "normal" AC sensor with fan output stop spinning.
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Xia, Tian, Julia Raneses e Stuart Batterman. "Improving the Performance of Pipeline Leak Detection Algorithms for the Mobile Monitoring of Methane Leaks". Atmosphere 13, n. 7 (29 giugno 2022): 1043. http://dx.doi.org/10.3390/atmos13071043.
Testo completoAbstract (sommario):
Methane (CH4) is the major component of natural gas, a potent greenhouse gas, and a precursor for the formation of tropospheric ozone. Sizable CH4 releases can occur during gas extraction, distribution, and use, thus, the detection and the control of leaks can help to reduce emissions. This study develops, refines, and tests algorithms for detecting CH4 peaks and estimating the background levels of CH4 using mobile monitoring, an approach that has been used to determine the location and the magnitude of pipeline leaks in a number of cities. The algorithm uses four passes of the data to provide initial and refined estimates of baseline levels, peak excursions above baseline, peak locations, peak start and stop times, and indicators of potential issues, such as a baseline shift. Peaks that are adjacent in time or in space are merged using explicit criteria. The algorithm is refined and tested using 1-s near-ground CH4 measurements collected on 20 days while driving about 1100 km on surface streets in Detroit, Michigan by the Michigan Pollution Assessment Laboratory (MPAL). Sensitivity and other analyses are used to evaluate the effects of each parameter and to recommend a parameter set for general applications. The new algorithm improves the baseline estimates, increases sensitivity, and more consistently merges nearby peaks. Comparisons of two data subsets show that results are repeatable and reliable. In the field study application, we detected 534 distinct CH4 peaks, equivalent to ~0.5 peaks per km traveled; larger peaks detected at nine locations on multiple occasions suggested sizable pipeline leaks or possibly other CH4 sources.
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South, David W. "Methane Emissions, Nowhere to Hide from Detection and Compliance Monitoring with Newly Launched Satellite". Climate and Energy 40, n. 11 (7 maggio 2024): 28–32. http://dx.doi.org/10.1002/gas.22407.
Testo completoAbstract (sommario):
Climate change is often synonymous with carbon dioxide (CO2) emissions. But there is another greenhouse gas (GHG) that is also a contributor: methane (CH4), a short‐lived but extremely potent GHG. Methane emissions behave differently than CO2 emissions when emitted into the atmosphere. The warming effects of CH4 wear off quickly compared to CO2, which remains in the atmosphere for centuries. But what it lacks in retention time, it makes up for in potency: CH4 has approximately 80 times the warming impact of CO2 over a 20‐year period. That means it has a greater impact on near‐term (20‐year) temperature change. When CH4 escapes (or is released) into the atmosphere, it acts as a heavy blanket in the atmosphere, trapping the sun's heat and warming the world.
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Kolkman-Quinn, Brendan, Donald C. Lawton e Marie Macquet. "CO2 leak detection threshold using vertical seismic profiles". International Journal of Greenhouse Gas Control 123 (febbraio 2023): 103839. http://dx.doi.org/10.1016/j.ijggc.2023.103839.
Testo completo
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Bezdek, Máté J., Shao-Xiong Lennon Luo, Kang Hee Ku e Timothy M. Swager. "A chemiresistive methane sensor". Proceedings of the National Academy of Sciences 118, n. 2 (31 dicembre 2020): e2022515118. http://dx.doi.org/10.1073/pnas.2022515118.
Testo completoAbstract (sommario):
A chemiresistive sensor is described for the detection of methane (CH4), a potent greenhouse gas that also poses an explosion hazard in air. The chemiresistor allows for the low-power, low-cost, and distributed sensing of CH4 at room temperature in air with environmental implications for gas leak detection in homes, production facilities, and pipelines. Specifically, the chemiresistors are based on single-walled carbon nanotubes (SWCNTs) noncovalently functionalized with poly(4-vinylpyridine) (P4VP) that enables the incorporation of a platinum-polyoxometalate (Pt-POM) CH4 oxidation precatalyst into the sensor by P4VP coordination. The resulting SWCNT-P4VP-Pt-POM composite showed ppm-level sensitivity to CH4 and good stability to air as well as time, wherein the generation of a high-valent platinum intermediate during CH4 oxidation is proposed as the origin of the observed chemiresistive response. The chemiresistor was found to exhibit selectivity for CH4 over heavier hydrocarbons such as n-hexane, benzene, toluene, and o-xylene, as well as gases, including carbon dioxide and hydrogen. The utility of the sensor in detecting CH4 using a simple handheld multimeter was also demonstrated.
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Yang, Yunting, Jiachen Jiang, Jiafu Zeng, Zhangxiong Chen, Xiaosong Zhu e Yiwei Shi. "CH4, C2H6, and CO2 Multi-Gas Sensing Based on Portable Mid-Infrared Spectroscopy and PCA-BP Algorithm". Sensors 23, n. 3 (27 gennaio 2023): 1413. http://dx.doi.org/10.3390/s23031413.
Testo completoAbstract (sommario):
A multi-gas sensing system was developed based on the detection principle of the non-dispersive infrared (NDIR) method, which used a broad-spectra light source, a tunable Fabry–Pérot (FP) filter detector, and a flexible low-loss infrared waveguide as an absorption cell. CH4, C2H6, and CO2 gases were detected by the system. The concentration of CO2 could be detected directly, and the concentrations of CH4 and C2H6 were detected using a PCA-BP neural network algorithm because of the interference of CH4 and C2H6. The detection limits were achieved to be 2.59 ppm, 926 ppb, and 114 ppb for CH4, C2H6, and CO2 with an averaging time of 429 s, 462 s, and 297 s, respectively. The root mean square error of prediction (RMSEP) of CH4 and C2H6 were 10.97 ppm and 2.00 ppm, respectively. The proposed system and method take full advantage of the multi-component gas measurement capability of the mid-infrared broadband source and achieve a compromise between performance and system cost.
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Chen, Jiuying, Pengxiang Cui, Chuncheng Zhou, Xiaoya Yu, Haohao Wu, Liangquan Jia, Mei Zhou et al. "Detection of CO2 and CH4 Concentrations on a Beijing Urban Road Using Vehicle-Mounted Tunable Diode Laser Absorption Spectroscopy". Photonics 10, n. 8 (17 agosto 2023): 938. http://dx.doi.org/10.3390/photonics10080938.
Testo completoAbstract (sommario):
The analysis of greenhouse gas emission characteristics on urban roads is of great significance for understanding the sources and sinks of urban greenhouse gases and their changing patterns. Based on tunable diode laser derivative absorption spectroscopy technology, which features high resolution, high sensitivity, and fast response, a vehicle-mounted system capable of simultaneously detecting CO2 and CH4 has been developed. The system has a response time of 0.38 s, with detection sensitivities of 5 ppb for CH4 and 0.2 ppm for CO2, power consumption of approximately 4.8 W, a weight of less than 3 kg, and dimensions of 255 mm × 275 mm × 85 mm. Using this system, monitoring campaigns were conducted on the same road in Beijing, running north–south, during different time periods in April and June 2023. The results show that there is little correlation between changes in CO2 and CH4 concentrations on the road, and these gas concentrations exhibit different influencing factors and spatiotemporal characteristics. The CO2 concentration on the road is primarily related to the degree of traffic congestion and does not exhibit significant seasonal variations. The average CO2 concentration measured on the road is much higher than the global average CO2 concentration during the same period. On the other hand, the CH4 concentration on the road is not strongly correlated with traffic congestion but is closely related to the leakage of methane from specific emission wells or covers. The CH4 concentration is higher in the morning, gradually decreases as the sun rises, and then increases again after sunset. The CH4 concentration measured at night in June is significantly lower than that in April, reflecting some seasonal variation. The CH4 concentration on the Beijing urban road is slightly higher than the global average CH4 concentration during the same period. The vehicle-mounted experiments verified the feasibility of using this self-developed system for vehicle-mounted detection of greenhouse gas concentrations on urban roads. The research results can provide data for analyzing the spatial pattern of regional carbon sources and sinks.
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Maazallahi, Hossein, Antonio Delre, Charlotte Scheutz, Anders M. Fredenslund, Stefan Schwietzke, Hugo Denier van der Gon e Thomas Röckmann. "Intercomparison of detection and quantification methods for methane emissions from the natural gas distribution network in Hamburg, Germany". Atmospheric Measurement Techniques 16, n. 21 (1 novembre 2023): 5051–73. http://dx.doi.org/10.5194/amt-16-5051-2023.
Testo completoAbstract (sommario):
Abstract. In August and September 2020, three different measurement methods for quantifying methane (CH4) emissions from leaks in urban gas distribution networks were applied and compared in Hamburg, Germany: the “mobile”, “tracer release”, and “suction” methods. The mobile and tracer release methods determine emission rates to the atmosphere from measurements of CH4 mole fractions in the ambient air, and the tracer release method also includes measurement of a gaseous tracer. The suction method determines emission rates by pumping air out of the ground using soil probes that are placed above the suspected leak location. The quantitative intercomparison of the emission rates from the three methods at a small number of locations is challenging because of limitations of the different methods at different types of leak locations. The mobile method was designed to rapidly quantify the average or total emission rate of many gas leaks in a city, but it yields a large emission rate uncertainty for individual leak locations. Emission rates determined for individual leak locations with the tracer release technique are more precise because the simultaneous measurement of the tracer released at a known rate at the emission source eliminates many of the uncertainties encountered with the mobile method. Nevertheless, care must be taken to properly collocate the tracer release and the leak emission points to avoid biases in emission rate estimates. The suction method could not be completed or applied at locations with widespread subsurface CH4 accumulation or due to safety measures. While the number of gas leak locations in this study is small, we observe a correlation between leak emission rate and subsurface accumulation. Wide accumulation places leaks into a safety category that requires immediate repair so that the suction method cannot be applied to these larger leaks in routine operation. This introduces a sampling bias for the suction method in this study towards the low-emission leaks, which do not require immediate repair measures. Given that this study is based on random sampling, such a sampling bias may also exist for the suction method outside of this study. While an investigation of the causal relationship between safety category and leak size is beyond the scope of this study, on average higher emission rates were observed from all three measurement-based quantification methods for leaks with higher safety priority compared to the leaks with lower safety concern. The leak locations where the suction method could not be applied were the biggest emitters, as confirmed by the emission rate quantifications using mobile and tracer methods and an engineering method based on the leak's diameter, pipeline overpressure, and depth at which the pipeline is buried. The corresponding sampling bias for the suction technique led to a low bias in derived emission rates in this study. It is important that future studies using the suction method account for any leaks not quantifiable with this method in order to avoid biases, especially when used to inform emission inventories.
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Wang, Kunyang, Ligang Shao, Jiajin Chen, Guishi Wang, Kun Liu, Tu Tan, Jiaoxu Mei, Weidong Chen e Xiaoming Gao. "A Dual-Laser Sensor Based on Off-Axis Integrated Cavity Output Spectroscopy and Time-Division Multiplexing Method". Sensors 20, n. 21 (30 ottobre 2020): 6192. http://dx.doi.org/10.3390/s20216192.
Testo completoAbstract (sommario):
In this article, a compact dual-laser sensor based on an off-axis integrated-cavity output spectroscopy and time-division multiplexing method is reported. A complete dual-channel optical structure is developed and integrated on an optical cavity, which allows two distributed feedback (DFB) lasers operating at wavelengths of 1603 nm and 1651 nm to measure the concentration of CO2 and CH4, simultaneously. Performances of the dual-laser sensor are experimentally evaluated by using standard air (with a mixture of CO2 and CH4). The limit of detection (LoD) is 0.271 ppm and 1.743 ppb at a 20 s for CO2 and CH4, respectively, and the noise equivalent absorption sensitivities are 2.68 × 10−10 cm−1 Hz−1/2 and 3.88 × 10−10 cm−1 Hz−1/2, respectively. Together with a commercial instrument, the dual-laser sensor is used to measure CO2 and CH4 concentration over 120 h and verify the regular operation of the sensor for the detection of ambient air. Furthermore, a first-order exponential moving average algorithm is implemented as an effective digital filtering method to estimate the gas concentration.
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Effendy, M., Yogi Wibisono Budhi, Yazid Bindar e S. Subagjo. "Metode operasi reverse flow reactor dengan umpan fluktuatif dalam pengolahan emisi gas metana di stasiun kompresor". Jurnal Teknik Kimia Indonesia 8, n. 3 (2 ottobre 2018): 74. http://dx.doi.org/10.5614/jtki.2009.8.3.1.
Testo completoAbstract (sommario):
Operation method of reverse flow reactor with fluctuating feed for methane gas emmision processing in compressor station.The leak of CH4 from the compressor stations can not be avoided and it may cause the global warming. The impact of the global warming can be reduced by oxidizing CH4 into CO2. The CH4 capture strategy using the exhaust mounted on the top of the building causes (1) CH4 levels detected in the gas mixture is very small (±1% volume), (2) the feed gas temperature is near the ambient temperature (±30 oC), (3) the CH4 concentration fluctuates over time. The reverse flow reactor (RFR) is a fixed bed reactor, which has the ability to abate the leak of CH4 and has the ability to act as an autothermal reactor. The purpose of this research is to find a proper operation procedure of the fixed bed reactor for the oxidation of lean methane emission via modeling and simulation. The reactor model is based on the continuity equation and the heat balance, while the concentration of the feed gas behavior dynamic and modeled as a step function. The model was solved numerically using the software package FlexPDE version 6. At ST (switching time) 50 seconds, the RFR operates autothermally with heat accumulation in the inert section fluctuating between 12.4 to 14.2 kJ. At ST 100 seconds, the heat trap inside the reactor increases monotonically. The use of ST 100 seconds requires an additional operation procedure to keep the reactor safe.Keywords: Global warming, concentration dynamic, autothermal operation, modeling and simulation, reverse flow reactor. AbstrakKebocoran gas CH4 dari stasiun kompresor tidak dapat dihindarkan dan ini merupakan salah satu sumber penyebab pemanasan global. Dampak pemanasan global ini dapat dikurangi dengan mengoksidasi gas CH4 menjadi gas CO2. Strategi penangkapan gas CH4 menggunakan exhaust yang terpasang pada bagian atas gedung menyebabkan (1) kadar CH4 yang terdeteksi dalam campuran gas cukup kecil (±1% volume), (2) temperatur gas umpan mendekati temperatur ruangan (± 30 oC), (3) konsentrasi gas CH4 akan berperilaku dinamik. Reverse flow reactor (RFR) mempunyai kemampuan untuk mengatasi akibat yang ditimbulkan oleh proses penangkapan gas CH4 di stasiun kompresor dan mempunyai kemampuan secara ototermal. Tujuan penelitian ini adalah mendapatkan metode operasi yang tepat untuk mengatasi gas umpan yang berperilaku dinamik. Model yang dikembangkan mengacu pada persamaan kontinuitas dan konsentrasi gas umpan yang berperilaku dinamik dimodelkan sebagai fungsi step. Model diselesaikan menggunakan software FlexPDE versi 6. Penggunaan switching time (ST) yang tepat dapat mengatasi permasalahan konsentrasi gas umpan yang berperilaku dinamik. Pada ST 50 detik, RFR mampu bekerja secara ototermal dengan nilai akumulasi panas di bagian inert yang berfluktuasi antara 12,4–14,2 kJ. Pada ST 100 detik, panas yang terjebak di dalam reaktor semakin lama semakin meningkat. Penggunaan ST 100 detik memerlukan prosedur operasi tambahan untuk menjaga reaktor agar tidak meleleh dan menjaga reaktor tetap beroperasi secara ototermal. Kata Kunci: Pemanasan global, dinamika konsentrasi, operasi ototermal, pemodelan dan simulasi, reaktor aliran bolak-balik.
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Carpenter, Chris. "Study Investigates Seismic Monitoring for Carbon Storage Leak Detection". Journal of Petroleum Technology 76, n. 02 (1 febbraio 2024): 86–88. http://dx.doi.org/10.2118/0224-0086-jpt.
Testo completoAbstract (sommario):
_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 22980, “Carbon Storage Leak Detection Through Seismic FWI and RTM: Different Survey Analyses,” by Sajjad Amani, Kyoto University. The paper has not been peer reviewed. Copyright 2023 International Petroleum Technology Conference. Reproduced by permission. _ In the complete paper, marine seismic data processing is investigated as a tool for monitoring possible leakages in geological carbon storage. Because of the great importance of storage permanence, a precise leakage-monitoring strategy is crucial. The proficiency of seismic monitoring solutions for leakage monitoring can be affected by shallower layers as a result of structure, seismic wave attenuation, and leak size. The authors explore two popular seismic monitoring methods used in this application in different scenarios: full waveform inversion (FWI) and reverse-time migration (RTM). Introduction Among the various carbon capture and storage (CCS) options, underground storage in saline aquifers is the best-understood solution. To assure storage consistency and permanence, finding the best strategy to precisely detect possible carbon leaks is essential. A perfect method must demonstrate the difference between stored CO2 and injected CO2 to detect potential fast- and slow-leakage areas. The seismic monitoring technique is the most efficient approach in this respect. Two popular tools for seismic monitoring are FWI and RTM. Several studies of their use in this application have been conducted. However, previous research did not analyze different survey arrays for carbon-leak detection using FWI and RTM. The current research aims to investigate quantitative aspects of CCS monitoring to conduct sensitivity analysis of the three different survey arrays [vertical seismic profile (VSP), crosswell, and surface] for different amounts of CO2-storage leakage in a saline aquifer reservoir. The capability of seismic-imaging methods for small amounts of leakage was tested. Comparison of these three arrays using monitoring methods such as RTM and FWI reveals their pros and cons in providing detailed information about the reservoir. In this research, a simple synthetic model was built that closely fits actual reservoirs characterized by suitable physical features such as velocity and density. Subsequently, elastic wave propagation simulation was implemented by use of a finite-difference scheme over a physical model of the reservoir. Then, FWI was applied to enhance the accuracy of the model parameters. With an efficient forward-modeling and inversion scheme, RTM was used as a powerful imaging tool that provides final high-resolution results for monitoring CO2 migration and possible leakage. This process examined the synthetic model for different amounts of CO2 leakage in saline aquifers to evaluate the performance of CO2 leakage monitoring using the seismic method. The results of the different receiver and source arrays also were compared to establish their effectiveness.
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Chen, Xiang, Hao Liu, Mai Hu, Lu Yao, Zhenyu Xu, Hao Deng e Ruifeng Kan. "Frequency-Domain Detection for Frequency-Division Multiplexing QEPAS". Sensors 22, n. 11 (26 maggio 2022): 4030. http://dx.doi.org/10.3390/s22114030.
Testo completoAbstract (sommario):
To achieve multi-gas measurements of quartz-enhanced photoacoustic spectroscopy (QEPAS) sensors under a frequency-division multiplexing mode with a narrow modulation frequency interval, we report a frequency-domain detection method. A CH4 absorption line at 1653.72 nm and a CO2 absorption line at 2004.02 nm were investigated in this experiment. A modulation frequency interval of as narrow as 0.6 Hz for CH4 and CO2 detection was achieved. Frequency-domain 2f signals were obtained with a resolution of 0.125 Hz using a real-time frequency analyzer. With the multiple linear regressions of the frequency-domain 2f signals of various gas mixtures, small deviations within 2.5% and good linear relationships for gas detection were observed under the frequency-division multiplexing mode. Detection limits of 0.6 ppm for CH4 and 2.9 ppm for CO2 were simultaneously obtained. With the 0.6-Hz interval, the amplitudes of QEPAS signals will increase substantially since the modulation frequencies are closer to the resonant frequency of a QTF. Furthermore, the frequency-domain detection method with a narrow interval can realize precise gas measurements of more species with more lasers operating under the frequency-division multiplexing mode. Additionally, this method, with a narrow interval of modulation frequencies, can also realize frequency-division multiplexing detection for QEPAS sensors under low pressure despite the ultra-narrow bandwidth of the QTF.
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Chen, Ke, Yewei Chen, Bo Zhang, Liang Mei, Min Guo, Hong Deng, Shuai Liu, Fengxiang Ma, Zhenfeng Gong e Qingxu Yu. "Highly Sensitive Photoacoustic Microcavity Gas Sensor for Leak Detection". Sensors 20, n. 4 (20 febbraio 2020): 1164. http://dx.doi.org/10.3390/s20041164.
Testo completoAbstract (sommario):
A highly sensitive photoacoustic (PA) microcavity gas sensor for leak detection is proposed. The miniature and low-cost gas sensor mainly consisted of a micro-electro-mechanical system (MEMS) microphone and a stainless-steel capillary with two small holes opened on the side wall. Different from traditional PA sensors, the designed low-power sensor had no gas valves and pumps. Gas could diffuse into the stainless-steel PA microcavity from two holes. The volume of the cavity in the sensor was only 7.9 μL. We use a 1650.96 nm distributed feedback (DFB) laser and the second-harmonic wavelength modulation spectroscopy (2f-WMS) method to measure PA signals. The measurement result of diffused methane (CH4) gas shows a response time of 5.8 s and a recovery time of 5.2 s. The detection limit was achieved at 1.7 ppm with a 1-s lock-in integral time. In addition, the calculated normalized noise equivalent absorption (NNEA) coefficient was 1.2 × 10−8 W·cm−1·Hz−1/2. The designed PA microcavity sensor can be used for the early warning of gas leakage.
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Siozos, Panagiotis, Giannis Psyllakis e Michalis Velegrakis. "Remote Operation of an Open-Path, Laser-Based Instrument for Atmospheric CO2 and CH4 Monitoring". Photonics 10, n. 4 (31 marzo 2023): 386. http://dx.doi.org/10.3390/photonics10040386.
Testo completoAbstract (sommario):
The technical specifications and the evaluation of the remote operation of the open-path, tunable diode laser absorption spectroscopic (TDLAS) instrument are presented. The instrument is equipped with two low optical power diode lasers in the near-infrared spectral range for the atmospheric detection of carbon dioxide, methane, and water vapors (CO2, CH4, and H2O). Additionally, the instrument eliminates the requirement of retroreflectors since it detects the back reflection of the laser beam from any topographic target. The instrument was operated remotely by measuring background concentrations of CO2 and CH4 in the atmosphere from 24 November 2022 to 4 January 2023. The accuracy of CO2 and CH4 measurement retrievals on a 200 m laser path was estimated at 20 ppm (4.8%) and 60 ppb (3.1%), respectively. The CH4 accuracy is comparable, but the CO2 accuracy is noticeably lower than the accuracy achieved in local operation. The accuracy issues raised are studied and discussed in terms of the laser driver’s cooling performance.
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Siozos, Panagiotis, Giannis Psyllakis, Peter C. Samartzis e Michalis Velegrakis. "Autonomous Differential Absorption Laser Device for Remote Sensing of Atmospheric Greenhouse Gases". Remote Sensing 14, n. 3 (19 gennaio 2022): 460. http://dx.doi.org/10.3390/rs14030460.
Testo completoAbstract (sommario):
A ground-based, integrated path, differential absorption (IPDA) light detection device capable of measuring multiple greenhouse gas (GHG) species in the atmosphere is presented. The device was developed to monitor greenhouse gas concentrations in small-scale areas with high emission activities. It is equipped with two low optical power tunable diode lasers in the near-infrared spectral range for the atmospheric detection of carbon dioxide, methane, and water vapors (CO2, CH4 and H2O). The device was tested with measurements of background concentrations of CO2 and CH4 in the atmosphere (Crete, Greece). Accuracies in the measurement retrievals of CO2 and CH4 were estimated at 5 ppm (1.2%) and 50 ppb (2.6%), respectively. A method that exploits the intensity of the recorded H2O absorption line in combination with weather measurements (water vapor pressure, temperature, and atmospheric pressure) to calculate the GHG concentrations is proposed. The method eliminates the requirement for measuring the range of the laser beam propagation. Accuracy in the measurement of CH4 using the H2O absorption line is estimated at 90 ppb (4.8%). The values calculated by the proposed method are in agreement with those obtained from the differential absorption LiDAR equation (DIAL).
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Wilson, Padarn, Andrew Feitz, Charles Jenkins, Henry Berko, Zoe Loh, Ashok Luhar, Mark Hibberd, Darren Spencer e David Etheridge. "Sensitivity of CO2 leak detection using a single atmospheric station". Energy Procedia 63 (2014): 3907–14. http://dx.doi.org/10.1016/j.egypro.2014.11.420.
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Wu, Xiao Nan, Mei Lin Hu, Bo Jun Shang e Yan Xian. "New City Gas Leak Detection Method and its Application". Applied Mechanics and Materials 204-208 (ottobre 2012): 4245–49. http://dx.doi.org/10.4028/www.scientific.net/amm.204-208.4245.
Testo completoAbstract (sommario):
In city gas leak detection, common methane detector is vulnerable to gases such as CO, CO2,H 2O and actual conditions of interference (such as humidity, coverings and wind direction), causing false detections and failure judgment. we put the optimization of optical methane detector with infrared absorption principle to replace the traditional combustible gas detector. In order to improve accuracy and efficiency of the gas leak detection, we put forward vehicle-mounted OMDTM optical methane detectors and complementary methane portable RMLDTM laser distance measuring instrument using a new method for gas leak detection. This method is effective to exclude other combustible gases such as methane to leak detection of interference effects, it not only covers the whole of the city gas network, proactively preventing leakage accidents from happening. In the leaks rescue operation, with it, testing vehicles can quickly arrive at the scene to participate to find the leaks, and deal with the leaks as soon as possible. Engineering field application effect suggests that the gas leak detection accuracy rate is higher, low false positive rates, fast response, and it meets the needs of modern urban gas leak detection.
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Nicoloso, Rodrigo da Silveira, Cimélio Bayer, Genuir Luis Denega, Paulo Armando Victória de Oliveira, Martha Mayumi Higarashi, Juliano Corulli Corrêa e Letícia dos Santos Lopes. "Gas chromatography and photoacoustic spectroscopy for the assessment of soil greenhouse gases emissions". Ciência Rural 43, n. 2 (febbraio 2013): 262–69. http://dx.doi.org/10.1590/s0103-84782013000200012.
Testo completoAbstract (sommario):
Assessments of soil carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions are critical for determination of the agricultural practices' potential to mitigate global warming. This study evaluated the photoacoustic spectroscopy (PAS) for the assessment of soil greenhouse gases (GHG) fluxes in comparison to the standard gas chromatography (GC) method. Two long-term experiments with different tillage and cropping systems over a Paleudult were evaluated using static chambers. PAS measurements of CO2 and N2O concentrations showed good relationship and linearity (R2=0.98 and 0.94, respectively) with GC results. However, CH4 measurements were significantly affected by air sample moisture which interfered on CH4 detection by PAS. Overestimation of CO2 and N2O concentrations in air samples determined by PAS (14.6 and 18.7%, respectively) were also related to sampling moisture. CO2 and N2O fluxes showed good agreement between methods (R2=0.96 and 0.95, respectively), though PAS overestimated fluxes by 18.6 and 13.6% in relation to GC results, respectively. PAS showed good sensitivity and was able to detect CO2 and N2O fluxes as low as 332mg CO2 m-2 h-1 and 21µg N2O m-2 h-1. PAS analyzer should be detailed calibrated to reduce humidity interference on CO2, CH4 and N2O concentrations measurements avoiding overestimation or erroneous determination of soil GHG fluxes.
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Wu, Xu, Yulong Du, Shijian Shi, Cong Jiang, Xueliang Deng, Song Zhu, Xiaolong Jin e Jingsong Li. "Simultaneous Detection of CO2 and CH4 Using a DFB Diode Laser-Based Absorption Spectrometer". Chemosensors 10, n. 10 (24 settembre 2022): 390. http://dx.doi.org/10.3390/chemosensors10100390.
Testo completoAbstract (sommario):
In this paper, an attractive gas sensing technique based on fiber optical sensing ideal was developed for the detection of multi-gas species simultaneously. Calibration-free laser absorption spectroscopy (LAS) was used and combined with a multi-pass optical absorption cell, two fiber-coupled near-infrared (NIR) distributed feedback (DFB) diode lasers are used and coupled into a single optical path for measuring CO2 and CH4 absorption spectra simultaneously. The optimal sampling pressure, laser tuning characteristics, spectral sampling points, and potential optical interference are theoretically and experimentally investigated in detail. The results indicated that the proposed technique has good reliability and has been successfully demonstrated for ambient CO2 and CH4 detection by using a single sample cell and detector. An Allan–Werle deviation analysis shows that detection limits of 0.12 ppm for CH4 and 35.97 ppm for CO2 can be obtained with an integration time of 181 s and 166 s, respectively. The proposed technique can be expanded to measure more molecules simultaneously by combing laser array and may pave a new way for developing a low-cost and ultra-compact multi-gas laser spectroscopy sensing system.
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Zhao, Wen, Nouha Alcheikh, Sofiane Ben Mbarek e Mohammad I. Younis. "Multi-functional resonant micro-sensor for simultaneous magnetic, CO2, and CH4 detection". Journal of Applied Physics 132, n. 14 (14 ottobre 2022): 144502. http://dx.doi.org/10.1063/5.0104007.
Testo completoAbstract (sommario):
We present a highly sensitive multi-parameter sensor for magnetic and gas detection. The device is based on an in-plane doubly clamped micro-beam micro-resonator, which is electrothermally heated. It acts as a Lorentz force magnetic sensor of high sensitivity, good linearity, good repeatability, and low hysteresis effect. It also functions as a gas-sensor based on the cooling/heating effect of the micro-beam as demonstrated for carbon dioxide (CO2) and methane (CH4) detection. The CO2/CH4 sensor shows high sensitivity and excellent linearity. In addition, we demonstrate simultaneous magnetic and gas detection by tracking the frequency shift of the first two symmetric and anti-symmetric modes at the same time. We show that the sensitivity of the magnetometer is gas-independent and only depends on the frequency shift of the second mode, which is unaffected by variations of the thermal axial load. For the first time, high sensitivity to magnetic fields, CO2, and CH4 is demonstrated using the same device. The demonstrated simultaneous and highly-sensitive multi-parameter sensing platform using a single resonator is promising for smart environmental and monitoring applications.
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Schmidt, Mark, Peter Linke, Stefan Sommer, Daniel Esser e Sergiy Cherednichenko. "Natural CO2 Seeps Offshore Panarea: A Test Site for Subsea CO2 Leak Detection Technology". Marine Technology Society Journal 49, n. 1 (1 gennaio 2015): 19–30. http://dx.doi.org/10.4031/mtsj.49.1.3.
Testo completoAbstract (sommario):
AbstractDuring RV Poseidon cruise POS469 (May 2014), the distribution of pCO2 in the near field of submarine volcanic gas flares in shallow water depths down to 50 m below sea level was continuously monitored using three different and independent methodologies. In situ nondispersive infrared (NDIR) spectrometry, pH measurements, and onboard membrane inlet mass spectrometry (MIMS) were used to determine the fate of rising CO2 bubbles and the dissolved CO2 plume patterns in a 300 × 400-m working area. The In situ sensor carrier platform, a towed video-controlled water sampling rosette, equipped with CTD sensors, guaranteed excellent ground truthing of seafloor characteristics and bubble discharge. Sensor data and near-seafloor observations indicated that the gas bubbles (<9 mm in diameter, >97 vol.% of CO2) dissolved very rapidly within the first 10 m above seafloor. Bottom water masses enriched with pCO2 (up to 1,100 μatm) show low pH values (up to 7.80) and tend to spread rather downslope west than following the measured weak current in SSE-SSW direction. The 3-D evaluation of pCO2 plume is a valuable tool to back-trace the origin of CO2 leakage when compared with local current regimes, water column CTD data, and seafloor bathymetry. Seep sites offshore Panarea can be used for studying CO2 leakage behavior and testing measuring strategies in shallow waters. Moreover, this area is a naturally designed laboratory to improve existing physicochemical and oceanographic transport models for subsea CO2 leakage.
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Eminov, R. A., e N. Z. Mursalov. "DEVELOPMENT OF NEW METHODS FOR DETECTION OF LEAKS OF HYDROCARBON GAS". Kontrol'. Diagnostika, n. 251 (maggio 2019): 60–64. http://dx.doi.org/10.14489/td.2019.05.pp.060-064.
Testo completoAbstract (sommario):
The paper is devoted to development of new methods for detection of leaks of hydrocarbon gas. It is determined that the wellknown fact on inverse interrelation of concentration of oxygen and such gases as N2 and CH4 can be used for remote determination of leaks of hydrocarbon gases. The gradient method for detection of leaks of natural gas composed of determination of two directions with minimum value of gradient of concentration of O2 in two fixed points and characterization of the point of crossing of them as a site of leak is suggested. The method of circles for detection of natural gases leaks site providing for determination of three points in supposed zone of leak and drawing up the circles around these points with growing radius with defined regularity is suggested. The point of crossing of all circles in some cycle of radiuses increase is presented as the gas leaks site. The carried out experimental researches held in various amounts of wind speed shown that when the wind speed surpass the fixed value location of gas leak site would be impossible due to effect of wind on spatial distribution and concentration of natural gas. Thus the proposed method is not designated for cases when a heavy wind occurs.
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Maazallahi, Hossein, Julianne M. Fernandez, Malika Menoud, Daniel Zavala-Araiza, Zachary D. Weller, Stefan Schwietzke, Joseph C. von Fischer, Hugo Denier van der Gon e Thomas Röckmann. "Methane mapping, emission quantification, and attribution in two European cities: Utrecht (NL) and Hamburg (DE)". Atmospheric Chemistry and Physics 20, n. 23 (7 dicembre 2020): 14717–40. http://dx.doi.org/10.5194/acp-20-14717-2020.
Testo completoAbstract (sommario):
Abstract. Characterizing and attributing methane (CH4) emissions across varying scales are important from environmental, safety, and economic perspectives and are essential for designing and evaluating effective mitigation strategies. Mobile real-time measurements of CH4 in ambient air offer a fast and effective method to identify and quantify local CH4 emissions in urban areas. We carried out extensive campaigns to measure CH4 mole fractions at the street level in Utrecht, the Netherlands (2018 and 2019), and Hamburg, Germany (2018). We detected 145 leak indications (LIs; i.e., CH4 enhancements of more than 10 % above background levels) in Hamburg and 81 LIs in Utrecht. Measurements of the ethane-to-methane ratio (C2:C1), methane-to-carbon dioxide ratio (CH4:CO2), and CH4 isotope composition (δ13C and δD) show that in Hamburg about 1∕3 of the LIs, and in Utrecht 2∕3 of the LIs (based on a limited set of C2:C1 measurements), were of fossil fuel origin. We find that in both cities the largest emission rates in the identified LI distribution are from fossil fuel sources. In Hamburg, the lower emission rates in the identified LI distribution are often associated with biogenic characteristics or (partly) combustion. Extrapolation of detected LI rates along the roads driven to the gas distribution pipes in the entire road network yields total emissions from sources that can be quantified in the street-level surveys of 440±70 t yr−1 from all sources in Hamburg and 150±50 t yr−1 for Utrecht. In Hamburg, C2:C1, CH4:CO2, and isotope-based source attributions show that 50 %–80 % of all emissions originate from the natural gas distribution network; in Utrecht more limited attribution indicates that 70 %–90 % of the emissions are of fossil origin. Our results confirm previous observations that a few large LIs, creating a heavy tail, are responsible for a significant proportion of fossil CH4 emissions. In Utrecht, 1∕3 of total emissions originated from one LI and in Hamburg >1/4 from two LIs. The largest leaks were located and fixed quickly by GasNetz Hamburg once the LIs were shared, but 80 % of the (smaller) LIs attributed to the fossil category could not be detected and/or confirmed as pipeline leaks. This issue requires further investigation.
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Pihlatie, M. K., R. Kiese, N. Brüggemann, K. Butterbach-Bahl, A. J. Kieloaho, T. Laurila, A. Lohila et al. "Greenhouse gas fluxes in a drained peatland forest during spring frost-thaw event". Biogeosciences Discussions 6, n. 3 (23 giugno 2009): 6111–45. http://dx.doi.org/10.5194/bgd-6-6111-2009.
Testo completoAbstract (sommario):
Abstract. Fluxes of greenhouse gases (GHG) carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) were measured during a two month campaign at a drained peatland forest in Finland by the eddy covariance (EC) technique (CO2 and N2O), and automatic and manual chambers (CO2, CH4 and N2O). In addition, GHG concentrations and soil parameters (mineral nitrogen, temperature, moisture content) in the peat profile were measured. The aim of the measurement campaign was to quantify the GHG fluxes before, during and after thawing of the peat soil, a time period with potentially high GHG fluxes, and to compare different flux measurement methods. The forest was a net CO2 sink during the two months and the fluxes of CO2 dominated the GHG exchange. The peat soil was a small sink of atmospheric CH4 but a small source of N2O. Both CH4 oxidation and N2O production took place in the top-soil whereas CH4 was produced in the deeper layers of the peat. During the thawing of the peat distinct peaks in CO2 and N2O emissions were observed. The CO2 peak followed tightly the increase in soil temperature, whereas the N2O peak occurred with an approx. one week delay after soil thawing. CH4 fluxes did not respond to the thawing of the peat soil. The CO2 and N2O emission peaks were not captured by the manual chambers and hence we conclude that automatic chamber measurements or EC are necessary to quantify fluxes during peak emission periods. Sub-canopy EC measurements and chamber-based fluxes of CO2 and N2O were comparable, although the fluxes of N2O measured by EC were close to the detection limit of the EC system. We conclude that if fluxes are high enough, i.e. greater than 5–10 μg N m−2 h−1, the EC method is a good alternative to measure N2O and CO2 fluxes at ecosystem scale, thereby minimizing problems with chamber enclosures and spatial representativeness of the measurements.
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Pihlatie, M. K., R. Kiese, N. Brüggemann, K. Butterbach-Bahl, A. J. Kieloaho, T. Laurila, A. Lohila et al. "Greenhouse gas fluxes in a drained peatland forest during spring frost-thaw event". Biogeosciences 7, n. 5 (25 maggio 2010): 1715–27. http://dx.doi.org/10.5194/bg-7-1715-2010.
Testo completoAbstract (sommario):
Abstract. Fluxes of greenhouse gases (GHG) carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) were measured during a two month campaign at a drained peatland forest in Finland by the eddy covariance (EC) technique (CO2 and N2O), and automatic and manual chambers (CO2, CH4 and N2O). In addition, GHG concentrations and soil parameters (mineral nitrogen, temperature, moisture content) in the peat profile were measured. The aim of the measurement campaign was to quantify the GHG fluxes during freezing and thawing of the top-soil, a time period with potentially high GHG fluxes, and to compare different flux measurement methods. The forest was a net CO2 sink during the two months and the fluxes of CO2 dominated the GHG exchange. The peat soil was a small sink of atmospheric CH4 and a small source of N2O. Both CH4 oxidation and N2O production took place in the top-soil whereas CH4 was produced in the deeper layers of the peat, which were unfrozen throughout the measurement period. During the frost-thaw events of the litter layer distinct peaks in CO2 and N2O emissions were observed. The CO2 peak followed tightly the increase in soil temperature, whereas the N2O peak occurred with a delay after the thawing of the litter layer. CH4 fluxes did not respond to the thawing of the peat soil. The CO2 and N2O emission peaks were not captured by the manual chambers and hence we conclude that high time-resolution measurements with automatic chambers or EC are necessary to quantify fluxes during peak emission periods. Sub-canopy EC measurements and chamber-based fluxes of CO2 and N2O were comparable, although the fluxes of N2O measured by EC were close to the detection limit of the system. We conclude that if fluxes are high enough, i.e. greater than 5–10 μg N m−2 h−1, the EC method is a good alternative to measure N2O and CO2 fluxes at ecosystem scale, thereby minimizing problems with chamber enclosures and spatial representativeness of the measurements.
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Loyon, L., F. Guiziou e P. Saint Cast. "Impact of manure management of different livestock on gaseous emissions: laboratory study". Australian Journal of Experimental Agriculture 48, n. 2 (2008): 128. http://dx.doi.org/10.1071/ea07263.
Testo completoAbstract (sommario):
A laboratory study investigated the impact of manure management and air temperature on the gaseous emissions of ammonia (NH3), methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) from manure stored under summer and winter conditions. Trials were carried out for 10–18 days on a pilot scale and were located outside the laboratory with a standardised protocol for ambient air speed. The concentrations of N2O, CH4, and CO2 in exhaust air from the storage vessel were analysed sequentially either by infrared detection or by gas chromatography coupled with a flame ionisation detector/electron captor detector, while NH3 concentration was determined by passing the exhaust air through acid traps. The results confirm that manure composition and temperature affect emissions of CH4, N2O, CO2 and NH3. NH3 emissions, expressed as a percentage of total nitrogen present in manure, ranged from 0.1% (duck slurry) to 12% (laying hen droppings) in winter and from 0.03% (scraped farmyard cattle manure) to 13% (laying hen droppings) in summer. Whatever the manure, nitrous oxide emissions were low, less than 0.5% of the total nitrogen. Solid manure tends to produce more CO2 than CH4, while the opposite is observed with liquid manure.
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Xiao, Chunlei, Bihong Fu, Hanqing Shui, Zhaocheng Guo e Jurui Zhu. "Detecting the Sources of Methane Emission from Oil Shale Mining and Processing Using Airborne Hyperspectral Data". Remote Sensing 12, n. 3 (6 febbraio 2020): 537. http://dx.doi.org/10.3390/rs12030537.
Testo completoAbstract (sommario):
Methane (CH4) is one of important greenhouse gases that affects the global radiative balance after carbon dioxide (CO2). Previous studies have demonstrated the detection of known sources of CH4 emission using the hyperspectral technology based on in situ vertical CH4 profile or ground CH4 emissions data. However, those approaches have not yet to detect the unknown terrestrial sources of CH4 emission at local-scale or regional-scale. In this paper, the Shortwave Airborne Spectrographic Imager (SASI) was employed to detect concentrated sources of CH4 emissions based on the absorption of CH4 in the shortwave infrared (SWIR) region. As a result, a band ratio (namely RCH4, RCH4 = Band91/Band78) determined through wavelet transform singularity detection has proposed for detection of the terrestrial CH4 emissions sources using SASI hyperspectral radiance image data, and elevated CH4 locations in the oil shale retorting plants were identified. Additionally, SASI surface reflectance data and multiple reference spectra in the spectral angle mapper (SAM) were used to classify surface sources of CH4 release. High-resolution Google Earth imagery and thermal imaging camera (FLIR GF320) had also verified that the CH4 releasing sources are mainly the oil shale mining field and the retorting plant. Therefore, the high-resolution imaging hyperspectral spectrometer can provide a powerful tool for detecting terrestrial CH4 release sources at local-scale to reduce the greenhouse gas emissions related to hydrocarbon development.
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Zhu, Tao, Xiao Chen, Shengping Wu, Jingjing Liu, Qi Liu e Zhao Rao. "Numerical Simulation of Urban Natural Gas Leakage Dispersion: Evaluating the Impact of Wind Conditions and Urban Configurations". Atmosphere 15, n. 4 (11 aprile 2024): 472. http://dx.doi.org/10.3390/atmos15040472.
Testo completoAbstract (sommario):
This study investigates the dispersion of natural gas leakages in urban environments under varying wind conditions (Beaufort levels 1, 2, and 6) and street layouts, with a focus on the implications for mobile leak detection at a height of 0.3 m above ground. Through numerical simulations, we analyze how urban canyons influence wind field and methane (CH4) concentration distributions, highlighting the impact of wind speed and urban geometry on gas dispersion. The key findings indicate that urban structures significantly affect gas dispersion patterns, with higher wind speeds facilitating better dispersion and reducing the risk of high-concentration gas buildups. The study underscores the need to consider both meteorological conditions and urban design in enhancing gas leak detection and safety measures in cities. The results contribute to improving emergency response strategies and urban planning for mitigating the risks associated with gas leaks.
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Oleksenko, L. P., N. P. Maksymovych, I. P. Matushko, G. V. Fedorenko, O. P. Ripko e L. V. Lutsenko. "Chromatographic Detector Based on Adsorption-Semiconductor Sensor for Detection of Reducing Gases in Air". Methods and Objects of Chemical Analysis 17, n. 1 (2022): 34–42. http://dx.doi.org/10.17721/moca.2022.34-42.
Testo completoAbstract (sommario):
A semiconductor sensor with a gas sensitive layer based on SnO2 and Sb2O5 with Pd additive synthesized by co-precipitation was studied as a chromatographic detector. It was found that the subject detector, using air as a carrier gas, can selectively detect each of the reducing gases (H2, CO, CH4, C2H2, C2H4, C2H6) which can leak into transformer oil if defects emerge during high-voltage transformers operation. It was established that for the fabricated detector the dependences of the signals on concentrations of the analyzed gases are linear in the range of 0–50 ppm for H2, CO, CH4 and 0–100 ppm for C2H2, C2H4, C2H6. The detector can be on-stream as combined with a chromatograph instrumentality which is rational for a wide practical application. The usage of the semiconductor detector based on the adsorption-semiconductor sensor is promising to significantly reduce the detection cost of the gases and to simplify diagnostics of the high-voltage transformer conditions.
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Somekawa, Toshihiro, e Masayuki Fujita. "Raman spectroscopy measurement of CH4 gas and CH4 dissolved in water for laser remote sensing in water". EPJ Web of Conferences 176 (2018): 01021. http://dx.doi.org/10.1051/epjconf/201817601021.
Testo completoAbstract (sommario):
We examined the applicability of Raman spectroscopy as a laser remote sensing tool for monitoring CH4 in water. The Raman technique has already been used successfully for measurements of CO2 gas in water. In this paper, considering the spectral transmittance of water, third harmonics of Q-switched Nd:YAG laser at 355 nm (UV region) was used for detection of CH4 Raman signals. The Raman signal at 2892 cm-1 from CH4 dissolved in water was detected at a tail of water Raman signal.
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Cheng, Yaopeng, Yinghe Xu, Ting Chen, Huaiyu Mei e Sailing He. "Differential laser-induced thermoelastic spectroscopy for dual-gas CO2/CH4 detection". Measurement 240 (gennaio 2025): 115594. http://dx.doi.org/10.1016/j.measurement.2024.115594.
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van Leeuwen, Charlotte, Arjan Hensen e Harro A. J. Meijer. "Leak detection of CO2 pipelines with simple atmospheric CO2 sensors for carbon capture and storage". International Journal of Greenhouse Gas Control 19 (novembre 2013): 420–31. http://dx.doi.org/10.1016/j.ijggc.2013.09.018.
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Mazza, Francesco, Ona Thornquist, Leonardo Castellanos, Thomas Butterworth, Cyril Richard, Vincent Boudon e Alexis Bohlin. "The ro-vibrational ν2 mode spectrum of methane investigated by ultrabroadband coherent Raman spectroscopy". Journal of Chemical Physics 158, n. 9 (7 marzo 2023): 094201. http://dx.doi.org/10.1063/5.0138803.
Testo completoAbstract (sommario):
We present the first experimental application of coherent Raman spectroscopy (CRS) on the ro-vibrational ν2 mode spectrum of methane (CH4). Ultrabroadband femtosecond/picosecond (fs/ps) CRS is performed in the molecular fingerprint region from 1100 to 2000 cm−1, employing fs laser-induced filamentation as the supercontinuum generation mechanism to provide the ultrabroadband excitation pulses. We introduce a time-domain model of the CH4 ν2 CRS spectrum, including all five ro-vibrational branches allowed by the selection rules Δv = 1, Δ J = 0, ±1, ±2; the model includes collisional linewidths, computed according to a modified exponential gap scaling law and validated experimentally. The use of ultrabroadband CRS for in situ monitoring of the CH4 chemistry is demonstrated in a laboratory CH4/air diffusion flame: CRS measurements in the fingerprint region, performed across the laminar flame front, allow the simultaneous detection of molecular oxygen (O2), carbon dioxide (CO2), and molecular hydrogen (H2), along with CH4. Fundamental physicochemical processes, such as H2 production via CH4 pyrolysis, are observed through the Raman spectra of these chemical species. In addition, we demonstrate ro-vibrational CH4 v2 CRS thermometry, and we validate it against CO2 CRS measurements. The present technique offers an interesting diagnostics approach to in situ measurement of CH4-rich environments, e.g., in plasma reactors for CH4 pyrolysis and H2 production.