Variability Of Methane Fluxes Research Articles

Spatio-temporal variations of methane fluxes in sediments of a deep stratified temperate lake

Spatio-temporal variability of sediment-mediated methane (CH4) production in freshwater lakes causes large uncertainties in predicting global lake CH4 emissions under different climate change and eutrophication scenarios. We conducted extensive sediment incubation experiments to investigate CH4 fluxes in Lake Stechlin, a deep, stratified temperate lake. Our results show contrasting spatial patterns in CH4 fluxes between littoral and profundal sites. The littoral sediments, ∼33% of the total sediment surface area, contributed ∼86.9% of the annual CH4 flux at the sediment-water interface. Together with sediment organic carbon quality, seasonal stratification is responsible for the striking spatial difference in sediment CH4 production between littoral and profundal zones owing to more sensitive CH4 production than oxidation to warming. While profundal sediments produce a relatively small amount of CH4, its production increases markedly as anoxia spreads in late summer. Our measurements indicate that future lake CH4 emissions will increase due to climate warming and concomitant hypoxia/anoxia.

Variations of methane fluxes and methane microbial community composition with soil depth in the riparian buffer zone of a sponge city park

Riparian buffers benefit both natural and man-made ecosystems by preventing soil erosion, retaining soil nutrients, and filtering pollutants. Nevertheless, the relationship between vertical methane fluxes, soil carbon, and methane microbial communities in riparian buffers remains unclear. This study examined vertical methane fluxes, soil carbon, and methane microbial communities in three different soil depths (0–5 cm, 5–10 cm, and 10–15 cm) within a riparian buffer of a Sponge City Park for one year. Structural equation model (SEM) results demonstrated that vertical methane fluxes varied with soil depths (λ = −0.37) and were primarily regulated by methanogenic community structure (λ = 0.78). Notably, mathematical regression results proposed that mcrA/pmoA ratio (R2 = 0.8) and methanogenic alpha diversity/methanotrophic alpha diversity ratio (R2 = 0.8) could serve as valid predictors of vertical variation in methane fluxes in the riparian buffer of urban river. These findings suggest that vertical variation of methane fluxes in riparian buffer soils is mainly influenced by carbon inputs and methane microbial abundance and community diversity. The study's results quantitatively the relationship between methane fluxes in riparian buffer soils and abiotic and biotic factors in the vertical direction, therefore contributing to the further development of mathematical models of soil methane emissions.

A method for continuous monitoring of the ebullition process and application to methane flux variations in Xiangxi Bay, Three Gorges Reservoir

A method for continuous monitoring of the ebullition process and application to methane flux variations in Xiangxi Bay, Three Gorges Reservoir

In situ flux estimates reveal large variations in methane flux across the bottom boundary layer of a eutrophic lake

AbstractMethane (CH4) produced in anoxic sediments plays a significant role in the carbon economy of many lakes and reservoirs. CH4 released from sediments first crosses the bottom boundary layer (BBL), the layer of water overlying the lakebed where currents are slowed by friction with the sediments below. Physical and biogeochemical conditions in the BBL, which can fluctuate hourly to daily with basin‐wide internal waves (seiches), likely influence CH4 transport from sediments into the hypolimnion. In this study, we estimated CH4 fluxes across the BBL of a eutrophic lake using a novel in situ flux gradient approach adapted from marine applications. For 2–6 h periods throughout the spring and summer, we estimated CH4 fluxes across the BBL using simultaneous measurements of CH4 concentrations, turbulent mixing, and thermal stratification. Sub‐daily variation in CH4 fluxes was high, and CH4 fluxes sometimes changed several‐fold within hours. These rapid shifts in BBL fluxes were likely influenced by fluctuations in seiche‐driven variations in the intensity of BBL turbulent mixing. Fluxes increased from spring to summer, concurrent with the development of lake stratification, and fueled an accumulation of CH4 below the thermocline. Throughout the summer, CH4 flux across the BBL exceeded CH4 accumulation below the thermocline, suggesting significant methanotrophy in the hypolimnion, consistent with incubation‐based oxidation rates. Our results are the first to demonstrate sub‐daily and seasonal variability in the timing and magnitude of CH4 fluxes within a lake BBL, and highlight a need to quantify such variability in other lentic systems.

Challenges Regionalizing Methane Emissions Using Aquatic Environments in the Amazon Basin as Examples

Key challenges to regionalization of methane fluxes in the Amazon basin are the large seasonal variation in inundated areas and habitats, the wide variety of aquatic ecosystems throughout the Amazon basin, and the variability in methane fluxes in time and space. Based on available measurements of methane emission and areal extent, seven types of aquatic systems are considered: streams and rivers, lakes, seasonally flooded forests, seasonally flooded savannas and other interfluvial wetlands, herbaceous plants on riverine floodplains, peatlands, and hydroelectric reservoirs. We evaluate the adequacy of sampling and of field methods plus atmospheric measurements, as applied to the Amazon basin, summarize published fluxes and regional estimates using bottom-up and top-down approaches, and discuss current understanding of biogeochemical and physical processes in Amazon aquatic environments and their incorporation into mechanistic and statistical models. Recommendations for further study in the Amazon basin and elsewhere include application of new remote sensing techniques, increased sampling frequency and duration, experimental studies to improve understanding of biogeochemical and physical processes, and development of models appropriate for hydrological and ecological conditions.

Diurnal landfill methane flux patterns across different seasons at a landfill in Southeastern US

Diurnal patterns of methane flux are examined at a landfill in the Southeastern US. Methane fluxes are measured by an eddy covariance (EC) tower during representative one-week periods in three seasons: summer, fall, and winter. Measured methane fluxes are compared with atmospheric pressure, temporal variation of atmospheric pressure, wind shear velocity, and air temperature. Landfill methane flux varies significantly with shear velocity and temporal changes in atmospheric pressure when the atmosphere is neutral. Under unstable atmospheric conditions, air temperature correlates best with methane flux, which is corroborated with an independent dataset of tracer correlation method (TCM) measurements for similar measurement periods. These field data support a mathematical model previously proposed to describe atmospheric effects on methane flux from landfills. The field data also indicate significant diurnal methane flux variations, with daytime fluxes up to 23 times greater than nighttime fluxes. Because the majority of historical TCM measurements of whole landfill methane flux are between 12 pm and 6 pm at this landfill, when daily emissions are highest because of atmospheric effects, average diurnal fluxes might have been overestimated by as much as 73%. Methane emissions are most representative of diurnal average emissions when atmospheric stability is near-neutral, which occurs in the late morning (∼11 am) and in the early evening (∼5 pm) at this site.

Methane fluxes in an artificial valley reservoir according to field observations and mathematical modeling

A very important problem nowadays is to assess anthropogenic impact on global warming. Increasing greenhouse gas concentrations in the atmosphere is the main reason for the rising global planet temperatures. The most important greenhouse gases (GHGs) are carbon dioxide and methane. The forcing made by carbon dioxide has been studied for a long time, while less attention has been focused on methane in this regard. However, more and more evidence indicates significant methane emissions into the atmosphere from anthropogenic sources. Less studied, but also important sources of methane are artificial reservoirs. In order to more accurately estimate methane emissions from the reservoirs, it is necessary to study the processes occurring with methane in the aquatic ecosystems in detail. For this purpose, in this study a Mozhaysk reservoir located in Moscow region is chosen. Studies of the spatial and temporal variations of methane fluxes have been carried out on this site for 6 years since 2015. In addition, this reservoir is used for validation of a well-known model, LAKE. This model can be used as an instrument for detailed estimation of methane emissions into the atmosphere from the surface of reservoirs.

Strong temporal variability in methane fluxes from natural gas well pad soils

We measured methane and carbon dioxide fluxes at natural gas well pad soils and undisturbed soils in the Rocky Mountain and Gulf Coast regions of the United States, including producing and gas storage wells. We collected both short-term (15 min) and multi-day (between 3 and 8), continuous measurements at 47 well pads and two undisturbed locations. Methane fluxes varied by more than an order of magnitude over periods as short as 30 min (e.g., 19–593 mg m−2 h−1 in one instance), and diurnal and seasonal variability was also significant (e.g., spring-to-fall change from 509 to 14174 mg m−2 h−1). We hypothesize that short-term flux variability was caused by pulsed flow of methane during its migration through the subsurface. Barometric pressure and well conditions likely impacted fluxes, but we found only weak evidence for this. Bacterial methanotrophy appeared to impact methane flux magnitude and variability. We injected methane into the subsurface at one well, and we found that, while fluxes of methane and carbon dioxide, and combustible soil gas concentrations, increased in response to the injection, the response was not uniform, and fluxes exhibited high hourly-scale variability, in spite of a constant injection rate. Methane fluxes tended to be higher at well pad soils compared to background soils (often much higher), and fluxes tended to be higher at well pad locations closer to the well head.

太湖流域农田稻季CH4通量特征及影响因子

PDF HTML阅读 XML下载 导出引用 引用提醒 太湖流域农田稻季CH4通量特征及影响因子 DOI: 10.5846/stxb201911062340 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金面上项目（41771571）；中科院南京地理与湖泊研究所前沿探索与基础性研究（NIGLAS2016QY02）；江苏省自然资源科技项目（KJXM2019007） Characteristics and impact factors of methane flux in the paddy fields of Taihu Lake Basin Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:开展太湖流域农田稻季CH4排放研究，深入了解稻田CH4排放规律，为稻田CH4减排、制定合理稻田管理措施提供科学依据。以太湖流域稻麦轮作农田为研究区域，运用涡度相关法观测其稻季CH4通量变化，分析其通量变化特征及影响因子。结果表明：太湖流域典型稻麦轮作区稻季为CH4的源，CH4排放总量为28.95 g/m2，稻季CH4通量日变化表现为无规则型与单峰型两种模式；稻季CH4排放整体集中在水稻生长前期（81.61%）及中期（16.16%）、后期排放相对较弱（2.23%），返青期排放量较低（日均0.102 μmol m-2 s-1），分蘖期较强（日均0.451 μmol m-2 s-1），成熟期最低（日均0.006 μmol m-2 s-1）；模型所模拟的累计CH4排放通量比累计测量CH4通量低6.69%，较好地模拟了太湖流域稻田CH4的排放，土壤温度、土壤水分、土壤电导率、摩擦风速可确认为太湖流域农田稻季CH4排放的主要驱动因子。 Abstract:Methane emissions play a key role in global warming and climate change. The mechanism of methane emission in the paddy fields of the Taihu Lake Basin-a typical rice-wheat rotation region of China and also an area with one of the highest rates of land use change in the country-is still unclear, largely due to limited observation and the spatial heterogeneity of the environment. Eddy covariance, one of most popular approaches to observing methane flux, has many advantages, including long-term continuous observation, high frequency, and large monitoring range, without destruction of the original soil environment. We utilized the eddy covariance method to observe the methane flux in rice-wheat rotation paddy fields in the Taihu Lake Basin. The missing flux values were interpolated with the GA-BPNN model. The characteristics and influencing factors of methane flux were then analyzed, and a semi-empirical multiplicative model was built. The results showed that the rice-wheat rotation paddy fields were the main source of methane in the Taihu Lake Basin. During the observation period, the total amount of emitted methane was 28.95 g/m2, and methane flux values varied in the range of 0-0.861 μmol m-2 s-1. The diurnal variation in methane flux during the rice season appears under two modes:irregular and unimodal. In the irregular mode, methane flux was unstable throughout the day, and in the unimodal mode, the emissions during the day were significantly higher than that at night. The emission of methane in the rice season is concentrated in the early and middle stages of rice growth, relatively weak in the later stage, relatively low in the green stage (0.102 μmol m-2 s-1 per day), strong in the tillering stage (0.451 μmol m-2 s-1 per day), and lowest in the maturity stage (0.006 μmol m-2 s-1 per day). The results of the analysis of various impact factors are as follows:The methane flux in the rice season increased exponential with air temperature and soil temperature at 10/20/40 cm depth (R2=0.589, 0.584, 0.521, 0.459, P<0.0001). Methane flux increased with increasing temperature. Methane flux showed a weak exponential relationship with soil moisture at 10/20 cm depth (R2=0.362, 0.372, P<0.0001). With the rise in soil moisture, methane flux increased. Methane flux has a quadratic relationship with soil moisture at a depth of 40 cm (R2=0.378, P<0.0001). When the soil moisture is less than 0.41 m3 m-3, methane flux decreases with the increase in soil moisture, and when the soil moisture is greater than 0.41 m3 m-3, methane flux increased with the rise in soil moisture. Methane flux showed a power relationship with soil conductivity at 10/20/40 cm depth (R2=0.309, 0.54, 0.439, P<0.0001). As the soil conductivity increases, the methane flux increases. Methane flux and friction wind speed are only significantly correlated on a half-hour scale. The methane flux estimated by the model 2 is 6.69% lower than measured flux. The model 2 well simulates the methane emission from paddy fields in the Taihu Lake Basin. The main driving factors of methane emission from paddy fields in the Taihu Lake Basin include soil temperature, soil moisture, soil conductivity, and friction wind speed. 参考文献 相似文献 引证文献

Reasons and patterns of spatio-temporal variability of methane emission from the Mozhaysk reservoir in summer period

Anthropogenic reservoirs are not only sources of clean energy, flow regulators, recreational and food resources, but also sources of greenhouse gases such as methane. The studies presented in this work, done on a well-studied low-flowing valley reservoir mainly in the summer, when the greatest variability of methane fluxes was observe. Depending on synoptic conditions, the temporal variability of methane fluxes varies greatly. Methane fluxes increase during the summer period and huge methane emissions observed before the autumn mixing stage. Emissions can occur during the destruction of temperature stratification, as a result of stormy weather. With such emissions, methane fluxes into the atmosphere can reach about 20 mgC*m-2*d-1, which is higher than the emission during convection. Revealing the patterns of spatio-temporal distribution of methane fluxes will help to determine the contribution of water bodies (in particular reservoirs) to the total methane budget of the atmosphere more accurately.

Interseasonal variability in methane concentrations and its fluxes on water-atmosphere border in the western part of the Sea of Okhotsk

For the first time subannual variability of methane fluxes on the water-atmosphere border in the water area of the Sea of Okhotsk, located eastward to Sakhalin Island, is shown. Variability of methane fluxes is determined by the presence and activity of submarine methane sources and is connected to the seasonal changes in hydrological and hydrochemical parameters of the sea water and the structure of of currents in the region under study. In spring and autumn the average fluxes are higher, than in the summer period. Within the summer modification of water and increase of stratification, the methane flux from the sea surface is reduced. In autumn, as a result of the autumnal convection of water and high average wind speed, methane, accumulated in transitional waters, is emitted into the atmosphere.

Interseasonal Variability in Methane Concentrations and Fluxes at the Water–Atmosphere Boundary in the Western Sea of Okhotsk

Intra-annual variability in methane fluxes at the water–atmosphere boundary was shown for the first time in the water area of the Sea of Okhotsk east of Sakhalin Island. The variability in methane fluxes is determined by the presence and activity of submarine methane sources and is related to seasonal changes in the hydrological and hydrochemical parameters of seawater and current structure in this region. In spring and autumn, the average fluxes are higher than in those in summer. The methane flux from the sea surface decreases during summer water modification and the increase in stratification. In autumn, methane accumulated in transitional waters is emitted into the atmosphere due to seasonal water convection and high average wind speed.

Interplay of Subduction Tectonics, Sedimentation, and Carbon Cycling

AbstractDistinct differences were observed in geochemical signatures in sediments from two sites drilled in the upper plate of the Costa Rica margin during Integrated Ocean Drilling Program (IODP) Expedition 334. The upper 80 m at Site U1379, located on the outer shelf, shows pore water non‐steady state conditions characteristic of a declining methane flux. These contrast with analyses of the upper sediment layers at the middle slope site (U1378) that reflect steady state conditions. Distinct carbonate‐rich horizons up to 11 meters thick were recovered between 63 and 310 meters below seafloor at Site U1379 but were not found at Site U1378. The carbonates and dissolved inorganic carbon from Site U1379 have a depleted carbon stable isotope signal (up to −25‰) that indicates anaerobic methane oxidation. This inference is further supported by distinct δ34S‐pyrite and magnetic susceptibility records that reveal fluctuations of the sulfate‐methane transition in response to methane flux variations. Tectonic reconstructions of this margin document a marked subsidence event after arrival of the Cocos Ridge, 2.2 ± 0.2 million years ago (Ma), followed by increased sedimentation rates and uplift. As the seafloor at Site U1379 rose from ~2,000 m to the present water depth of ~126 m, the site moved out of the gas hydrate stability zone at ~1.1 Ma, triggering upward methane advection, methane oxidation, and the onset of massive carbonate formation. Younger carbonate occurrences and the non‐steady state pore water profiles at Site U1379 reflect continued episodic venting likely modulated by changes in the underlying methane reservoir.

Seasonal variation of methane flux from Mozhaisk reservoir

The paper present the results of methane flux measuring from the surface of valley type reservoir with a long water residence time. The factors of its spatio-time variations are revealed. The results of calculation and measurements of diffusive flux are compared.

Using chemical compositions of sediments to constrain methane seepage dynamics: A case study from Haima cold seeps of the South China Sea

Cold seeps frequently occur at the seafloor along continental margins. The dominant biogeochemical processes at cold seeps are the combined anaerobic oxidation of methane and sulfate reduction, which can significantly impact the global carbon and sulfur cycles. The circulation of methane-rich fluids at margins is highly variable in time and space, and assessing past seepage activity requires the use of specific geochemical markers. In this study, we report multiple sedimentary proxy records for three piston gravity cores (QDN-14A, QDN-14B, and QDN-31) from the Haima seep of the South China Sea (SCS). By combining total organic carbon (TOC), total inorganic carbon (TIC), total nitrogen (TN), total sulfur (TS), acid insoluble carbon and sulfur isotope (δ13Corganic carbon and δ34Sacid-insoluble), and δ34S values of chromium reducibility sulfur (δ34SCRS), as well as carbon isotopes of TIC (δ13CTIC) in sediments, our aim was to provide constraints on methane seepage dynamics in this area. We identified three sediment layers at about 260–300 cm, 380–420 cm and 480–520 cm sediment depth, characterized by particular anomalies of low δ13CTIC values and high TS content, high TS and CRS contents, and high δ34Sacid-insoluble and δ34SCRS values, respectively. On this basis, we propose that these sediment horizons correspond to distinct methane release events preserved in the sediment record. While the exact mechanisms accounting for the presence (or absence) of these particular geochemical signals in the sediment are not known, we propose that they correspond to variations in methane flux and their duration through time. Overall, our results suggest that sedimentary carbon and sulfur and their isotopes are useful tracers for better understanding of methane seepage dynamics over time.

Dynamics of net ecosystem methane exchanges on temporal scale in tropical lowland rice

Net ecosystem methane exchanges (NEME) from lowland rice often show significant variations in diurnal, seasonal and yearly scales and with crop phenology. Air and soil temperatures, standing water, and radiation are believed to be primary drivers of such variations. We studied the dynamics of net ecosystem methane exchange in three consecutive years (2014–16) using eddy covariance technology. Wet season (July–October) showed higher diurnal methane flux variations than that of dry season (December–March) due to prolonged anoxic condition and higher methanogens in the former. Significant diurnal variations in NEME were also noticed during different crop growth stages. Variations were higher in flowering stage followed by ripening in 2015 and 2016. But in 2014, it was highest at panicle initiation (PI) stage. Principal component bivariate plot analysis and performance analytic correlation were performed for variables such as net ecosystem carbon dioxide exchange (NEE), NEME, sensible heat (Hs), latent heat (LE), photosynthetically active radiation (PAR), net radiation (NR), air temperature and soil temperature (5 cm depth) in order to assess their relationships. The NEME was positively correlated to air and soil temperatures in all the years. However, in year 2016, NEME also showed positive correlation to PAR and NR. These relationships could provide valuable information to partitioning and process-based simulation modelling for projecting and up scaling of NEME to regional and global scales.

Spatial-Temporal Variations of CO2 and CH4 Flux Through a Water-air Interface Under the Effect of Primary Productivity in Wulixia Reservoir

In recent years, the effect of greenhouse gas has been a focus. In order to reveal the spatial-temporal variations of CO2 and CH4 flux through a water-air interface, Wulixia reservoir was selected as a typical case for measuring CO2and CH4 flux using a floating chamber during four study periods in 2016.The primary productivity of the water was also studied. The results indicate that surface-layer water in Wulixia reservoir is a CO2 sink in summer, varying between -30.14 and -3.47 mg·(m2·h)-1. However, it is the source of CO2 in autumn and winter, varying between 15.57 mg·(m2·h)-1 and 115.06 mg·(m2·h)-1. The variation of methane flux is obvious in summer, but it is stable in autumn and winter. The spatial distribution of CO2 and CH4 show that they are higher in the typical bay area and lower in the tailing dam as well as in the drawdown zone of the reservoir. In addition, the spatial and temporal variation of CO2 and CH4 are negatively and positively correlated with primary productivity (r -0.477 and 0.771), respectively. Due to the high activity of photosynthetic micro- organisms in summer, CO2 can be sequestered, allowing the surface-layer water in Wulixia reservoir to be a CO2 sink. In addition, methanogenic bacteria can oxidize organic carbon produced by photosynthetic micro-organisms. Therefore, CH4 has a negative correlation with primary productivity. The results provide important information for the study of microorganism functions in karst water systems.

Diurnal Patterns of Methane Flux from a Seasonal Wetland: Mechanisms and Methodology

Methane emissions from wetlands are temporally dynamic. Few chamber-based studies have explored diurnal variation in methane flux with high temporal replication. Using an automated sampling system, we measured methane flux every 2.5 to 4 h for 205 diel cycles during three growing seasons (2013–2015) from a seasonal wetland in the Prairie Pothole Region of North America. During ponded conditions, fluxes were generally positive (i.e., methanogenesis dominant, 10.1 ± 0.8 mg m−2 h−1), had extreme range of variation (from −1 to 70 mg m−2 h−1), and were highest during late day. In contrast, during dry conditions fluxes were very low and primarily negative (i.e., oxidation dominant, −0.05 ± 0.002 mg m−2 h−1), with the highest (least negative) fluxes occurring at pre-dawn. During semi-saturated conditions, methane fluxes also were very low, oscillated between positive and negative values (i.e., balanced between methanogenesis and methane oxidation), and exhibited no diel pattern. Methane flux was positively correlated with air temperature during ponded conditions (r = 0.57) and negatively during dry conditions (r = −0.42). Multiple regression analyses showed that temperature, light and water-filled pore space explained 72% of variation in methane flux. Methane fluxes are highly temporally dynamic and follow contrasting diel patterns that are dependent on dominant microbial processes influenced by saturation state.

Multi-scale temporal variation of methane flux and its controls in a subtropical tidal salt marsh in eastern China

CH4 emissions could vary with biotic and abiotic factors at different time scales. However, little is known about temporal dynamics of CH4 flux and its controls in coastal marshes. In this study, CH4 flux was continuously measured with the eddy covariance technique for 2 years in a subtropical salt marsh in eastern China. Wavelet analysis was applied to explore the multi-scale variations of CH4 flux and its controls. Additionally, partial wavelet coherence was used to disentangle confounding effects of measured variables. No consistent diurnal pattern was found in CH4 fluxes. However, the hot-moments of CH4 flux were observed after nighttime high tide on days near the spring tide. Periodic dynamics were also observed at multi-day, semilunar and seasonal scales. Tide height in summer had a negative effect on CH4 flux at the semilunar scale. Air temperature explained most variations in CH4 fluxes at the multi-day scale but CH4 flux was mainly controlled by PAR and GEP at the seasonal scale. Air temperature explained 48% and 56% of annual variations in CH4 fluxes in 2011 and 2012, respectively. In total, the salt marsh acted as a CH4 source (17.6 ± 3.0 g C–CH4 m−2 year−1), which was higher than most studies report for inland wetlands. Our results show that CH4 fluxes exhibit multiple periodicities and its controls vary with time scale; moreover, CH4 flux is strongly modified by tide. This study emphasizes the importance of ecosystem-specific measurements of CH4 fluxes, and more work is needed to estimate regional CH4 budgets.

Modelling the Diurnal Variations of Methane Emissions from the Cyperus malaccensis Tidal Marsh in the Minjiang River Estuary

Tidal marshes are important sources of atmospheric methane; however, the processes and mechanisms of diurnal methane flux variations in tidal marshes remain unclear. In this study, we modified the Walter model to simulate diurnal variations of methane fluxes in the Cyperus malaccensis tidal marsh in the Minjiang River Estuary. The sediment environmental variables, relative humidity (RH), and the tide level were considered in the modified model; the explicit difference scheme was applied for model calculation. Our simulated and observed results indicate that the methane fluxes are higher in non-inundation periods and lower in inundation periods, higher during the day and lower at night. Moreover, our simulation suggests that plant-mediated transport and ebullition are dominant pathways for methane emissions, and the diurnal variation patterns of methane fluxes are directly regulated by the tide level, sediment temperature, and RH. The model sensitivity tests suggest that methane fluxes are significantly influenced by the maximum potential methane production rate and various environmental variables. The model comparison indicates that our modifications have significantly improved the performance of the model in simulating diurnal variations of methane emissions in the C. malaccensis tidal marsh.