Distribution Of Methane Concentration Research Articles

Spatial Distribution of Methane Concentration in Baikal Surface Water in the Spring Period

Spatial Distribution of Methane Concentration in Baikal Surface Water in the Spring Period

Improved Gaussian regression model for retrieving ground methane levels by considering vertical profile features

Atmospheric methane is one of the major greenhouse gases and has a great impact on climate change. To obtain the polluted levels of atmospheric methane in the ground-level range, this study used satellite observations and vertical profile features derived by atmospheric chemistry model to estimate the ground methane concentrations in first. Then, the improved daily ground-level atmospheric methane concentration dataset with full spatial coverage (100%) and 5-km resolution in mainland China from 2019 to 2021 were retrieved by station-based observations and gaussian regression model. The overall estimated deviation between the estimated ground methane concentrations and the WDCGG station-based measurements is less than 10 ppbv. The R by ten-fold cross-validation is 0.93, and the R2 is 0.87. The distribution of the ground-level methane concentrations in the Chinese region is characterized by high in the east and south, and low in the west and north. On the time scale, ground-level methane concentration in the Chinese region is higher in winter and lower in summer. Meanwhile, the spatial and temporal distribution and changes of ground-level methane in local areas have been analyzed using Shandong Province as an example. The results have a potential to detect changes in the distribution of methane concentration.

Analysis of the influence of different pore ratios on methane adsorption characteristics of coal

The diverse pore structures in coal are pivotal in coalbed methane storage and transportation, making it highly significant to explore methane adsorption characteristics across varying pore sizes for effective prevention and control of coal mine gas disasters. Using the proposed graphene nanotube filling method, eight coal molecule models with varying pore size ratios were constructed, including four different pore radii: 0.35 nm, 0.55 nm, 0.75 nm, and 2 nm. Methane adsorption amount, methane density, and methane concentration distribution were obtained through Monte Carlo (GCMC) and molecular dynamics (MD) simulation methods. The research results show that coal consisting of multiple pore sizes had a better methane adsorption capacity than a single pore size. Combining pore sizes of 0.35 nm, 0.55 nm, and 0.75 nm in a 1:2:1 ratio resulted in the highest excess methane adsorption capacity in coal, reaching 5.623 mmol/g. The single pore size of 0.55 nm in coal had the lowest excess adsorption amount of methane, which was 2.236 mmol/g. The presence of mesopores weakened the methane adsorption capacity of coal, and this weakening effect increased with the increase of mesopore proportion. In the model composed of single pore size micropores, the methane concentration inside the pores was uniformly distributed. The coexistence of multiple micropores may lead to methane filling in the micropores in a monolayer adsorption form. The coexistence of micropores and mesopores does not alter methane filling in the micropores and monolayer adsorption in the mesopores. The research results provide new insights into our understanding of the impact of pores on methane adsorption in coal.

Distribution of dissolved methane in seawater from the East China Sea to the Ryukyu forearc

Methane is a greenhouse gas, and the East China Sea acts as a source of emissions to the atmosphere. On the other hand, the distribution of methane concentration in the Ryukyu Arc shelf and forearc region has not been clarified. Therefore, we investigated the continental slope and continental shelf areas from the Okinawa Trough to the landward side and the island shelf and forearc areas to the seaward side of the East China Sea. The methane concentration in the Kuroshio Current region was very low, and the methane concentration in the seawater just above the seafloor in the area directly above the hydrothermal systems was exceptionally high. In addition, methane concentration in seawater just above the seafloor where cold seeps and mud volcanoes are known is higher than the background, and higher methane concentrations were found in continental slope area and the island shelf area. The results suggest the existence of previously unreported methane sources such as cold seeps and mud volcanoes in the continental slope region and the island shelf region.

Hotspot Detection and Estimation of Methane Emissions from Landfill Final Cover

The main objectives of this study were to identify methane hotspots through spatial distribution tests of the surface methane concentration above a landfill final cover and to investigate the effects of rainfall, atmospheric pressure, ground temperature, and ambient methane concentration on methane emissions. A portable laser methane detector was used to measure the spatial distribution of methane concentrations. The methane concentration distribution showed a distinct spatial variability. The maximum methane concentration reached 3225 ppm, while 73.0% of the methane concentration values were below 10.0 ppm. Several meteorological factors were found to be associated with the variation in methane emissions. Rainfall limited gas transport in the cover, resulting in more significant methane hotspots. Atmospheric pressure was negatively correlated with methane emission. The ambient methane concentration and methane flux had a significant positive linear correlation. Based on a linear correlation equation, the spatial distribution of methane concentrations in the landfill could be converted into a methane emission distribution. The estimated average value for methane emissions in the test area was approximately 4.3 g m−2 d−1. This study provides an experimental basis for locating methane hotspots and assessing methane emissions in landfill final covers, and proposes supplementary means for detecting geomembrane damage in landfill covers.

Applying Model Studies to Support the Monitoring of Methane Hazard during the Process of Underground Coal Mining

Abstract The process of underground mining is one of the most complex and hazardous activities. In order to maintain the continuity and efficiency of this process, it is necessary to take measures to reduce this hazard. The paper addresses this issue by presenting a developed methodology for using model studies and numerical simulations to support the process of monitoring methane hazards. Its basis is the developed model of the region of underground mining exploitation along with the ventilation phenomena occurring in it. To develop it, the ANSYS Fluent program was used, based on the finite volume method classified as computational fluid mechanics. The model reflects both the geometries and physical and chemical phenomena occurring in the studied area, as well as the auxiliary ventilation equipment used during operation. The research was conducted for two variants of methane emissions from goaf zones, the first of which concerned the actual state of the mining area, and the second of which concerned increased methane emissions from these goaf zones. The purpose of the study was to determine the distribution of methane concentrations in the most dangerous part of the studied area, which is the intersection of the longwall and the tailgate, as well as the distribution of ventilation air flow velocities affecting them. The studies for both variants made it possible to determine places particularly exposed to the occurrence of dangerous concentrations of methane in this region. The methodology developed represent a new approach to studying the impact of methane emissions from goaf zones into mine workings.

Methane Distribution in Lake Baikal Water

Data on the distribution of methane concentration in water in the open water area and the northern end of Lake Baikal and in the source of the Angara R. collected in September 2016 and 2019 are analyzed. To apply correlation analysis, in addition to methane, various hydrochemical characteristics were also determined, including the temperature, pH, the concentrations of О2, suspended matter, Corg, Norg, Porg, mineral compounds of nitrogen and phosphorus. Methane concentration in Baikal water in 2016 varied within 0.44–3.41 µL/dm3 (on the average, 0.80 µL/dm3); in 2019, within 0.20–5.19 µL/dm3 (on the average, 1.22 µL/dm3). The maximal methane concentration was recorded in the water mass of the deepest central depression of the lake, and the minimal, in its southern depression. Among shallow areas, minimal methane concentrations were recorded in the coastal zone of Listvenichnyi Bay, and its maximal concentrations, in the northern part of the lake, into which many rivers empty, as well as in Selenginskoe shallows. Most stations, either deep-water or shallow, showed a peak of subsurface maximum of methane concentration at depths of 25–50 m (thermocline zone), after which its concentrations commonly dropped, reaching their minimal values either in the intermediate water mass or in bottom layers. Shallow areas, in addition to higher methane concentrations compared to deep-water areas, also featured a higher contrast in its vertical distribution in the water mass. The analysis of correlation relationships between the examined hydrochemical characteristics revealed significant direct correlations of methane concentration with the concentrations of Corg and Norg and an inverse correlation with O2 concentrations.

Determining the Concentration Level of Air Pollutants Related to Road Traffic in Kano Metropolis

The problem of road traffic-related air pollutants is universal. Traffic air pollution usually occurs on roads and mainly at intersections which significantly affects the air quality of such areas. The research aims to provide empirical evidence on the relationship between road transport air pollutants and temperature conditions on climate modification in the study area, which might perfect environmental sustainability. The study was best designed on field Experimentation to assess the spatiotemporal emission levels and analyses the implications of road Vehicular traffic-related air pollutants Concentration (such as, Carbon monoxide, Nitrogen dioxide, Sulphur dioxide, Hydrogen Sulphide and Methane gas) on Kano weather conditions (precisely Temperature) in 15 selected sample sites or locations, the measurements of pollutants Concentration, temperature level were carried out using the instruments called a Crowcorn gas detector, field thermometer were used together with the help of 5 research assistants. presents the periodic concentration levels of CH4 (methane) in relation to road traffic in different time periods: afternoon, evening, and morning, categorized into three concentration levels: high, medium, and low. The table provides various statistical measures to describe the distribution of methane concentrations within each category. High Concentrations in the afternoon reveal an average mean methane concentration is 0.20. The coefficient of variability, which measures the dispersion of the data points around the mean, is 46.06%. The skewness of 1.19 implies a moderately positively skewed distribution. The kurtosis of 1.38 indicates a distribution with a peak slightly higher than a normal distribution and a moderate presence of outliers. These findings could inform air quality management and monitoring efforts in Kano Metropolis. If temperature is consistently correlated with higher CO and CH4 levels, authorities may need to consider seasonal variations and temperature-related interventions when addressing air quality issues.

Influence of the Auxiliary Air-Duct Outlet and the Brattice Location on the Methane Hazard—Numerical Simulations

The article presents the results of research into the influence of the location of auxiliary ventilation devices on the distribution of methane concentrations at the outlet of the longwall in an underground mine. Since this area is crucial from the point of view of explosion risk, the existence of an optimal arrangement of these devices could lead to improved safety of the crew working in the area. The aim of conducted study was to examine if the impact of this devices placement is significant. The research was carried out with the use of computational fluid dynamics (CFD) modeling—Ansys Fluent. The analyses took into account the location of the two most commonly used devices: a brattice and an auxiliary air-duct. The numerical model has been prepared and validated based on in situ measurements. Thirty-two cases of device configurations were analysed. The length and position of the brattice, as well as the height and position air-duct outlet along tailgate, were modified. It has been shown that although the presented solutions are an effective risk mitigation method, contrary to the common opinion of many practitioners, the impact of their exact placement, provided it is compliant with the regulations, is not significant for the registered methane concentration distribution at a longwall outlet.

Identification of zones with coal spontaneous combustion hazards in the three goafs surrounding an isolated Island working face: A case study on Qianyingzi Coal Mine

ABSTRACT Crushed coal pillars on both sides of isolated Island working face will form multiple goafs in series, resulting in complex air leakage in goafs. Therefore, it is crucial to explore the law of coal spontaneous combustion in the goaf of the isolated Island working face. Taking the W3225 isolated working face of Qianyingzi Coal Mine as the engineering background, a reliable numerical model was established and different porosity ratios of adjacent goafs and coal pillars were set. Oxygen and methane concentration distributions in goaf were calculated to identify the zones with spontaneous combustion hazards. The following conclusions were drawn. Spontaneous combustion hazards exist in the multiple goafs, and the areas of the zones with spontaneous combustion hazards in the goaf of the working face account for a large proportion of total areas of spontaneous combustion hazards. When the porosities of adjacent goafs within 10 m on the coal pillar sides or the porosities of coal pillars are reduced, the risk of spontaneous combustion hazards of multiple goafs is reduced. When the porosities of both is reduced simultaneously, the risk of spontaneous combustion hazards in multiple goafs and coal pillars is greatly reduced. According to the simulation results, the porosities of adjacent goafs and coal pillars on both sides of the isolated working face can be reduced by means of shotcrete and grouting, which can reduce the series air leakage channel between each goaf, thus the fire prevention and extinguishing ability of the working face will be improved. Ultimately, the pressure on working face advancement can be relieved.

Study on Methane Distribution in the Face Zone of the Fully Mechanized Roadway with Overlap Auxiliary Ventilation System

An overlap auxiliary ventilation system is very often used for driving roadways in methane-rich coal seams. An overlap zone between the outlets of the forcing duct ends with a whirl flow air-duct (WFAD) and the exhaust duct ends with a dust scrubber that is created by applying the overlap system. This study examines the distribution of methane concentrations at various distances in the overlap zone. Maintaining a long overlap zone could increase the advance of the face. Therefore, the impact of overlap zone length on the methane concentration distribution, in and beyond the overlap zone, is investigated. The evaluation of methane concentrations is performed utilizing a well-established computational fluid dynamics (CFD) approach. The mathematical model of methane emissions into the roadway is adopted. Moreover, the CFD model is validated. A vortex of the return air, caused by the free airstream flowing out of the dust scrubber, is found. This air vortex is responsible for higher methane concentrations at the end of the overlap zone. Therefore, the conclusion can be drawn that maintaining the length of the overlap zone at 5 m to 10 m should be done to control permissible methane concentrations.

Modeling and Simulation of the Methane Risk in the Mining Production Process

Abstract The mining production process is of particular importance for the area of Upper Silesia, as well as a very significant impact on the economy of the entire country. One of the most common and most dangerous threats to this process is the methane hazard. It is related to the presence of methane in coal seams, which under appropriate conditions is a flammable and explosive gas. Events related to the methane hazard constitute a huge threat to the life and health of the crew as well as the infrastructure and equipment of excavations. Therefore, they have a huge impact on the efficiency of the entire mining production process. In order to ensure the safety and continuity of the production process, it is necessary to prevent the formation of dangerous methane concentrations in the area covered by the operation. One of the tools that can be used to assess the state of methane hazard are model studies supported by numerical simulation. Based on these studies, the article analyzes the distribution of methane concentration in the mining area. This area included an actual mining excavation in one of the hard coal mines. The model tests were carried out with the use of the finite volume method in the ANSYS Fluent software. The obtained results can be used for preventive measures and constitute an important source of information for the assessment of the methane hazard state.

Influence of concentration gradient on methane–air explosion propagation: An experimental study

ABSTRACT In underground coal mines, the methane distribution under actual conditions has a certain concentration gradient due to various factors such as air leakage and lower air velocity in local areas. In this paper, experiments were carried out to investigate the influence of the methane accumulation and concentration gradient on the methane–air explosion propagation. The experimental results show that in the process of methane explosion, the propagation distance of the flame and explosion wave in the rising stage are directly proportional to the methane accumulation. When the reaction time is less than a critical value, the flame propagation velocity and explosion overpressure with methane concentration distribution in the case of 9.5%–9.5%–3.5% are greater than those with a methane concentration change of 9.5%–9.5%–5.5%. However, when the methane concentration distribution is 9.5%–9.5%–0%, the flame propagation velocity and overpressure are less than those of the distributed methane in the working conditions of 9.5%–9.5%–3.5% and 9.5%–9.5%–5.5%.

Temporospatial Analysis of methane trend in China over the last decade — Estimation of Anthropogenic Methane Emission and Contributions from Different Anthropogenic Sources

China’s atmospheric methane burden has been on the rise in the past decades. However, the relationship between trends and major anthropogenic sources of methane emissions in China has not been well understood. The temporal and spatial distribution of methane concentration in China is investigated using ten years of methane column data (2010-2019) from the Greenhouse Gases Observing Satellite (GOSAT). High-value regions of methane enhancement are found in the northern provinces of China (northeast Xinjiang, northwest Gansu, inner Mongolia, and the border region of Heilongjiang and Jilin). Based on 2010-2018 China Official Statistical Yearbook data and the latest research about methane emission factors, the major anthropogenic methane emissions in China through 2010-2017 are estimated. With Principal Component Analysis (PCA) method on data of estimated anthropogenic emissions and deseasonalized year-averaged methane concentrations in China, it is found that the top three anthropogenic sources with the greatest impact on methane emissions are coal mining, sanitary landfill, and domestic animal rumination. They could have a potential connection with methane enhancement trend high value regions.

Dissolved methane concentration distribution of reservoir in winter based on the underway high-resolution monitoring: A case study of the Xibeikou Reservoir in Hubei Province<sup>*</sup>

Dissolved methane concentration distribution of reservoir in winter based on the underway high-resolution monitoring: A case study of the Xibeikou Reservoir in Hubei Province<sup>*</sup>

Estimation of the Spatial Distribution of Methane Concentration in the Area of the Barents and Kara Seas in Summer in 2016–2017

The problem of estimation of average fields of air pollutant concentration based on local measurement data is stated: the problem of the passive location of the atmosphere by wind, or the problem of the fluid location of the atmosphere. The definitions of new functions are given: the average effective field of concentration and the average effective field of sources. The system of integral equations these functions obey is also presented. The results of numerical estimates of quasi-two-dimensional average fields of methane concentration in the area of the Barents and Kara seas retrieved from data on surface concentrations measured on Belyi Island in the summer of 2016 and 2017 are analyzed. A typical feature of the resulting fields is their mosaic pattern, as well as the higher values of methane concentration on the continent and in the coastal zone.

Analysis of spatiotemporal variations in middle-tropospheric to upper-tropospheric methane during the Wenchuan <i>M</i><sub>s</sub> = 8.0 earthquake by three indices

Abstract. This research studied the spatiotemporal variation in methane in the middle to upper troposphere during the Wenchuan earthquake (12 May 2008) using AIRS retrieval data and discussed the methane anomaly mechanism. Three indices were proposed and used for analysis. Our results show that the methane concentration increased significantly in 2008, with an average increase of 5.12×10-8, compared to the average increase of 1.18×10-8 in the previous 5 years. The absolute local index of change of the environment (ALICE) and differential value (diff) indices can be used to identify methane concentration anomalies. The two indices showed that the methane concentration distribution before and after the earthquake broke the distribution features of the background field. As the earthquake approached, areas of high methane concentration gradually converged towards the west side of the epicenter from both ends of the Longmenshan fault zone. Moreover, a large anomalous area was centered at the epicenter 8 d before the earthquake occurred, and a trend of strengthening, weakening and strengthening appeared over time. The gradient index showed that the vertical direction obviously increased before the main earthquake and that the value was positive. The gradient value is negative during coseismic or post-seismic events. The gradient index reflects the gas emission characteristics to some extent. We also determined that the methane release was connected with the deep crust–mantle stress state, as well as micro-fracture generation and expansion. However, due to the lack of any technical means to accurately identify the source and content of methane in the atmosphere before the earthquake, an in-depth discussion has not been conducted, and further studies on this issue may be needed.

ИССЛЕДОВАНИЕ РАСПРЕДЕЛЕНИЯ ГАЗОВОЗДУШНОЙ СМЕСИ В КОРПУСЕ ИНЖЕКЦИОННОЙ ГОРЕЛКИ С ТЕПЛОВЫМ РАССЕКАТЕЛЕМ

The article is devoted to the development of the design of a low-pressure injection burner equipped with a thermal divider and the study of the process of distribution of methane concentration and velocity of gas-air mixture velocity in the burner body. The Solid Works Flow Simulation software complex is used to study the process of formation of the gas-air medium in the burner body. The design of a low pressure injection burner with a conical-shaped heat spreader has been developed. Placing the divider in the burner body provides preheating of the gas-air mixture and allows to increase the speed of flame propagation. Computer simulation of the process of gas-air mixture formation in the burner body for 3 burner constructions is performed: without a divider, with a divider length of 11 mm and a divider length of 25,5 mm. As a result of modeling, it is found that the placement of the divider with a length of L = 11 mm does not affect the distribution of methane and the velocity of the gas-air mixture in the burner body and at the exit of the firing holes. Increasing the length of the divider to 25,5 mm leads to an increase in the speed of the gas-air mixture and an increase in the concentration of methane in the firing holes. Therefore, the placement of the burner housing to the heat spreader with a length of 11 mm is the best solution to improve the efficiency and stability of the combustion process.

Analysis of The Effects of the Position of the Air Duct Supplying Fresh Air to the Working Face of the Mined Dog Heading on Methane Concentration Levels

Each year, more than one hundred kilometres of new dog headings are mined in underground hard coal mines. Such headings are ventilated by means of an air duct system. A stream of fresh air is supplied to the working face of the mined heading through an air duct with a view to ensuring proper chemical composition and temperature of the mining atmosphere. This is because this heading is being exploited and the ventilation must provide adequate working conditions for the crew. While dog headings are being mined in the body of coal, they are additionally filled with methane, which is released in this process. Due to the risk of its combustion and explosion, methane is a highly dangerous gas. It represents one of the greatest hazards in underground mining. Therefore, a particularly essential issue during the mining of dog headings is to reduce the potential for dangerous methane concentrations to occur. To prevent this from happening, it is necessary to select adequate parameters for the fresh air supplied through the air duct and the position of this air duct. It is the position of the air duct that appears to be a very significant element in the ventilation process of dog headings. Model-based tests were conducted to determine how the position of the air duct affects methane concentration levels. Their results have been presented in the paper. The tests were conducted using Computational Fluid Dynamics (CFD). The related calculations were performed in ANSYS Fluent, based on the finite volume method (FVM). The analyses performed made it possible to identify the concentrations levels of methane and the physical parameters of the flowing gas mixture at each spatial point of the area under examination, for the boundary conditions adopted. The purpose of the tests was to determine whether and to what extent the position of the air duct, which is used to supply fresh air to the mined dog heading, influences methane concentration in this heading. The tests were conducted for an actual mining region in which a dog heading was mined. The input parameters for the model (boundary conditions) were therefore adopted from the actual system. The model-based tests helped to determine the distributions for methane concentration depending on the position of the air duct. The analysis mainly encompassed the distance between the outlet of the air duct and the surface of the mined body of coal. The use of model-based tests which employed numerical methods made it possible to determine a series of significant physical and chemical parameters of the resulting mixture of gases. Their distributions and values in selected points for the variants under analysis have been presented in the paper. The results obtained unambiguously demonstrate that the position of the air duct has a significant impact on the distributions of methane concentration levels in the mined dog heading. In the Authors’ opinion, these results may constitute an essential source of information for service teams responsible for ensuring ventilation-related safety in mines. This is because they allow for predicting the distribution of methane concentration and other parameters of the gas mixture that occurs in dog headings during the mining process.

Methane in water and bottom sediments of lake Baikal

The results of the methane concentration distribution in different areas of Lake Baikal obtained in 2014 and 2015 were analyzed in this study. In periods of expedition examinations, the methane concentration in the water and in the bottom sediments of the lake varied in a range from <0.1 to 13.9 μl/dm3 (average: 0.7 μl/dm3) and from <0.01 to 3.69 μg/g of the dry deposition (average: 0.34 μg/g). The maximum methane concentrations in the water and bottom sediments in the lake were typical for the North region, where rivers Verkhnyaya Angara and Kichera are flowing, and in the individual stations of the profile set along the mouth area of the river Selenga, as well as the stations located in the zone of the waste water underwater release of Baikalsk City and the Baikalsk pulp and paper mill closed in 2013. The presence of increased and decreased methane concentrations in the examined top strata of the sediments of Lake Baikal was stipulated herein aside from the differences in the power of the anthropogenic effect by the variation of the sediment accumulation conditions determining the particle size distribution and the organic matter content and, as a result, by the methanogenesis intensity.