scholarly journals Exploring Methane Emission Drivers in Wetlands: The Cases of Massaciuccoli and Porta Lakes (Northern Tuscany, Italy)

2021 ◽  
Vol 11 (24) ◽  
pp. 12156
Author(s):  
Stefania Venturi ◽  
Franco Tassi ◽  
Jacopo Cabassi ◽  
Antonio Randazzo ◽  
Marta Lazzaroni ◽  
...  
Keyword(s):  
Organic Matter ◽  
Climate Models ◽  
Open Water ◽  
Environmental Drivers ◽  
Gaseous Species ◽  
Microbial Decomposition ◽  
Ch4 Emissions ◽  
Ch4 Production ◽  
Wind Exposure ◽  
Diffusive Fluxes

Wetlands are hotspots of CH4 emissions to the atmosphere, mainly sustained by microbial decomposition of organic matter in anoxic sediments. Several knowledge gaps exist on how environmental drivers shape CH4 emissions from these ecosystems, posing challenges in upscaling efforts to estimate global emissions from waterbodies. In this work, CH4 and CO2 diffusive fluxes, along with chemical and isotopic composition of dissolved ionic and gaseous species, were determined from two wetlands of Tuscany (Italy): (i) Porta Lake, a small wetland largely invaded by Phragmites australis reeds experiencing reed die-back syndrome, and (ii) Massaciuccoli Lake, a wide marsh area including open-water basins and channels affected by seawater intrusion and eutrophication. Both wetlands were recognized as net sources of CH4 to the atmosphere. Our data show that the magnitude of CH4 diffusive emission was controlled by CH4 production and consumption rates, being mostly governed by (i) water temperature and availability of labile carbon substrates and (ii) water column depth, wind exposure and dissolved O2 contents, respectively. This evidence suggests that the highest CH4 diffusive fluxes were sustained by reed beds, providing a large availability of organic matter supporting acetoclastic methanogenesis, with relevant implications for global carbon budget and future climate models.

scholarly journals A simple calculation algorithm to separate high-resolution CH<sub>4</sub> flux measurements into ebullition- and diffusion-derived components

2017 ◽  
Vol 10 (1) ◽  
pp. 109-118 ◽  
Author(s):  
Mathias Hoffmann ◽  
Maximilian Schulz-Hanke ◽  
Juana Garcia Alba ◽  
Nicole Jurisch ◽  
Ulrike Hagemann ◽  
...  
Keyword(s):  
Measurement Data ◽  
Flux Measurement ◽  
Open Water ◽  
Simple Calculation ◽  
Environmental Drivers ◽  
Calculation Algorithm ◽  
Wetland Ecosystems ◽  
Ch4 Emissions ◽  
Concentration Changes ◽  
And Diffusion

Abstract. Processes driving the production, transformation and transport of methane (CH4) in wetland ecosystems are highly complex. We present a simple calculation algorithm to separate open-water CH4 fluxes measured with automatic chambers into diffusion- and ebullition-derived components. This helps to reveal underlying dynamics, to identify potential environmental drivers and, thus, to calculate reliable CH4 emission estimates. The flux separation is based on identification of ebullition-related sudden concentration changes during single measurements. Therefore, a variable ebullition filter is applied, using the lower and upper quartile and the interquartile range (IQR). Automation of data processing is achieved by using an established R script, adjusted for the purpose of CH4 flux calculation. The algorithm was validated by performing a laboratory experiment and tested using flux measurement data (July to September 2013) from a former fen grassland site, which converted into a shallow lake as a result of rewetting. Ebullition and diffusion contributed equally (46 and 55 %) to total CH4 emissions, which is comparable to ratios given in the literature. Moreover, the separation algorithm revealed a concealed shift in the diurnal trend of diffusive fluxes throughout the measurement period. The water temperature gradient was identified as one of the major drivers of diffusive CH4 emissions, whereas no significant driver was found in the case of erratic CH4 ebullition events.

scholarly journals HIMMELI v1.0: HelsinkI Model of MEthane buiLd-up and emIssion for peatlands

2017 ◽  
Author(s):  
Maarit Raivonen ◽  
Sampo Smolander ◽  
Leif Backman ◽  
Jouni Susiluoto ◽  
Tuula Aalto ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Flux Measurement ◽  
Environmental Drivers ◽  
Co2 Production ◽  
Area Index ◽  
Carbon Cycle Model ◽  
Ch4 Emissions ◽  
Oxidation Rates ◽  
Ch4 Production ◽  
Carbon Dioxide Co2

Abstract. Wetlands are one of the most significant natural sources of methane (CH4) to the atmosphere. They emit CH4 because decomposition of soil organic matter in waterlogged anoxic conditions produces CH4, in addition to carbon dioxide (CO2). Production of CH4 and how much of it escapes to the atmosphere depend on a multitude of environmental drivers. Models simulating the processes leading to CH4 emissions are thus needed for upscaling observations to estimate present CH4 emissions and for producing scenarios of future atmospheric CH4 concentrations. Aiming at a CH4 model that can be added to models describing peatland carbon cycling, we developed a model called HIMMELI that describes CH4 build-up in and emissions from peatland soils. It is not a full peatland carbon cycle model but it requires the rate of anoxic soil respiration as input. Driven by soil temperature, leaf area index (LAI) of aerenchymatous peatland vegetation and water table depth (WTD), it simulates the concentrations and transport of CH4, CO2 and oxygen (O2) in a layered one-dimensional peat column. Here, we present the HIMMELI model structure, results of tests on the model sensitivity to the input data and to the description of the peat column (peat depth and layer thickness), and an intercomparison of the modelled and measured CH4 fluxes at Siikaneva, a peatland flux measurement site in Southern Finland. As HIMMELI describes only the CH4-related processes, not the full carbon cycle, our analysis revealed mechanisms and dependencies that may remain hidden when testing CH4 models connected to complete peatland carbon models, which is usually the case. Our results indicated that 1) the model is flexible and robust and thus suitable for different environments; 2) the simulated CH4 emissions largely depend on the prescribed rate of anoxic respiration; 3) the sensitivity of the total CH4 emission to other input variables, LAI and WTD, is mainly mediated via the O2 concentrations that affect the CH4 production and oxidation rates; 4) with given input respiration, the peat column description does not affect significantly the simulated CH4 emissions.

scholarly journals HIMMELI v1.0: HelsinkI Model of MEthane buiLd-up and emIssion for peatlands

2017 ◽  
Vol 10 (12) ◽  
pp. 4665-4691 ◽  
Author(s):  
Maarit Raivonen ◽  
Sampo Smolander ◽  
Leif Backman ◽  
Jouni Susiluoto ◽  
Tuula Aalto ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Environmental Drivers ◽  
Co2 Production ◽  
Area Index ◽  
Carbon Cycle Model ◽  
Ch4 Emissions ◽  
Oxidation Rates ◽  
Ch4 Production ◽  
Input Variables ◽  
Carbon Dioxide Co2

Abstract. Wetlands are one of the most significant natural sources of methane (CH4) to the atmosphere. They emit CH4 because decomposition of soil organic matter in waterlogged anoxic conditions produces CH4, in addition to carbon dioxide (CO2). Production of CH4 and how much of it escapes to the atmosphere depend on a multitude of environmental drivers. Models simulating the processes leading to CH4 emissions are thus needed for upscaling observations to estimate present CH4 emissions and for producing scenarios of future atmospheric CH4 concentrations. Aiming at a CH4 model that can be added to models describing peatland carbon cycling, we composed a model called HIMMELI that describes CH4 build-up in and emissions from peatland soils. It is not a full peatland carbon cycle model but it requires the rate of anoxic soil respiration as input. Driven by soil temperature, leaf area index (LAI) of aerenchymatous peatland vegetation, and water table depth (WTD), it simulates the concentrations and transport of CH4, CO2, and oxygen (O2) in a layered one-dimensional peat column. Here, we present the HIMMELI model structure and results of tests on the model sensitivity to the input data and to the description of the peat column (peat depth and layer thickness), and demonstrate that HIMMELI outputs realistic fluxes by comparing modeled and measured fluxes at two peatland sites. As HIMMELI describes only the CH4-related processes, not the full carbon cycle, our analysis revealed mechanisms and dependencies that may remain hidden when testing CH4 models connected to complete peatland carbon models, which is usually the case. Our results indicated that (1) the model is flexible and robust and thus suitable for different environments; (2) the simulated CH4 emissions largely depend on the prescribed rate of anoxic respiration; (3) the sensitivity of the total CH4 emission to other input variables is mainly mediated via the concentrations of dissolved gases, in particular, the O2 concentrations that affect the CH4 production and oxidation rates; (4) with given input respiration, the peat column description does not significantly affect the simulated CH4 emissions in this model version.

scholarly journals Organic sediment formed during inundation of a degraded fen grassland emits large fluxes of CH<sub>4</sub> and CO<sub>2</sub>

2010 ◽  
Vol 7 (6) ◽  
pp. 9273-9303
Author(s):  
M. Hahn-Schöfl ◽  
D. Zak ◽  
M. Minke ◽  
J. Gelbrecht ◽  
J. Augustin ◽  
...  
Keyword(s):  
Organic Matter ◽  
Plant Litter ◽  
Electron Acceptors ◽  
Sediment Layer ◽  
Organic Substrates ◽  
Peat Layer ◽  
Ch4 Emissions ◽  
Ch4 Production ◽  
Fresh Plant ◽  
Fresh Organic Matter

Abstract. Peatland restoration by inundation of drained areas can alter local greenhouse gas emissions by altering rates of CO2 and CH4 emissions. Factors that can influence these emissions include the quality and amount of substrates available for anaerobic degradation processes and the sources and availability of electron acceptors. In order to learn about possible sources of high CO2 and CH4 emissions from a rewetted degraded fen grassland, we performed incubation experiments that tested the effects of fresh plant litter in the flooded peats on pore water chemistry and CO2 and CH4 production and emission. The position in the soil profile of the pre-existing drained peat substrate affected initial rates of anaerobic CO2 production subsequent to flooding, with the uppermost peat layer producing the greatest specific rates of CO2 evolution. CH4 production rates depended on the availability of electron acceptors and was significant only when sulfate concentrations were reduced in the pore waters. Very high specific rates of both CO2 (maximum of 412 mg C d−1 kg−1 C) and CH4 production (788 mg C d−1 kg−1 C) were observed in a new sediment layer that accumulated over 2.5 years since the site was flooded. This new sediment layer was characterized by overall low C content, but represented a mixture of sand and relatively easily decomposable plant litter from reed canary grass killed by flooding. Samples that excluded this new sediment layer but included intact roots remaining from flooded grasses had specific rates of CO2 (max. 28 mg C d−1 kg−1 C) and CH4 (max. 34 mg C d−1 kg−1 C) production that were 10–20 times lower, and were comparable to those of newly flooded upper peat layer. Lowest rates of anaerobic CO2 and CH4 production (range of 4–8 mg C d−1 kg−1 C and <1 mg C d−1 kg−1 C) were observed when all fresh organic matter sources (plant litter and roots) were excluded. In conclusion, the presence of fresh organic substrates such as plant and root litter originating from plants killed by inundation has a high potential for CH4 production, whereas peat without any fresh plant-derived material is relatively inert. Anaerobic CO2 and CH4 production in peat only occurs when some labile organic matter is available, e.g. from remaining roots or root exudates.

scholarly journals Diffusive emission of methane and carbon dioxide from two hydropower reservoirs in Brazil

2015 ◽  
Vol 75 (2) ◽  
pp. 331-338 ◽  
Author(s):  
AA. Marcelino ◽  
MA. Santos ◽  
VL. Xavier ◽  
CS. Bezerra ◽  
CRO. Silva ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Greenhouse Gas ◽  
Co2 Emissions ◽  
Co2 Fluxes ◽  
Gaseous Species ◽  
Climate Conditions ◽  
Ch4 Emissions ◽  
Diffusive Fluxes ◽  
Hydropower Reservoirs ◽  
Três Marias Reservoir

The role of greenhouse gas emissions from freshwater reservoirs and their contribution to increase greenhouse gas concentrations in the atmosphere is currently under discussion in many parts of the world. We studied CO2 and CH4 diffusive fluxes from two large neotropical hydropower reservoirs with different climate conditions. We used floating closed-chambers to estimate diffusive fluxes of these gaseous species. Sampling campaigns showed that the reservoirs studied were sources of greenhouse gases to the atmosphere. In the Serra da Mesa Reservoir, the CH4 emissions ranged from 0.530 to 396.96 mg.m–2.d–1 and CO2 emissions ranged from –1,738.33 to 11,166.61 mg.m–2.d–1 and in Três Marias Reservoir the CH4 fluxes ranged 0.720 to 2,578.03 mg.m–2.d–1 and CO2 emission ranged from -3,037.80 to 11,516.64 to mg.m–2.d–1. There were no statistically significant differences of CH4 fluxes between the reservoirs, but CO2 fluxes from the two reservoirs studied were significantly different. The CO2 emissions measured over the periods studied in Serra da Mesa showed some seasonality with distinctions between the wet and dry transition season. In Três Marias Reservoir the CO2 fluxes showed no seasonal variability. In both reservoirs, CH4 emissions showed a tendency to increase during the study periods but this was not statistically significant. These results contributed to increase knowledge about the magnitude of CO2 and CH4 emission in hydroelectric reservoirs, however due to natural variability of the data future sampling campaigns will be needed to better elucidate the seasonal influences on the fluxes of greenhouse gases.

scholarly journals Impacts of temperature and soil characteristics on methane production and oxidation in Arctic tundra

2018 ◽  
Vol 15 (21) ◽  
pp. 6621-6635 ◽  
Author(s):  
Jianqiu Zheng ◽  
Taniya RoyChowdhury ◽  
Ziming Yang ◽  
Baohua Gu ◽  
Stan D. Wullschleger ◽  
...  
Keyword(s):  
Transition Layer ◽  
Electron Flow ◽  
Oxidation Potential ◽  
Organic Soils ◽  
Ch4 Oxidation ◽  
Microbial Decomposition ◽  
Ch4 Emissions ◽  
Oxidation Rates ◽  
Ch4 Production ◽  
Oxidation Potentials

Abstract. Rapid warming of Arctic ecosystems accelerates microbial decomposition of soil organic matter and leads to increased production of carbon dioxide (CO2) and methane (CH4). CH4 oxidation potentially mitigates CH4 emissions from permafrost regions, but it is still highly uncertain whether soils in high-latitude ecosystems will function as a net source or sink for CH4 in response to rising temperature and associated hydrological changes. We investigated CH4 production and oxidation potential in permafrost-affected soils from degraded ice-wedge polygons on the Barrow Environmental Observatory, Utqiaġvik (Barrow), Alaska, USA. Frozen soil cores from flat and high-centered polygons were sectioned into organic, transitional, and permafrost layers, and incubated at −2, +4 and +8 ∘C to determine potential CH4 production and oxidation rates. Significant CH4 production was only observed from the suboxic transition layer and permafrost of flat-centered polygon soil. These two soil sections also exhibited highest CH4 oxidation potentials. Organic soils from relatively dry surface layers had the lowest CH4 oxidation potential compared to saturated transition layer and permafrost, contradicting our original assumptions. Low methanogenesis rates are due to low overall microbial activities measured as total anaerobic respiration and the competing iron-reduction process. Our results suggest that CH4 oxidation could offset CH4 production and limit surface CH4 emissions, in response to elevated temperature, and thus must be considered in model predictions of net CH4 fluxes in Arctic polygonal tundra. Future changes in temperature and soil saturation conditions are likely to divert electron flow to alternative electron acceptors and significantly alter CH4 production, which should also be considered in CH4 models.

scholarly journals What is recalcitrant soil organic matter?

2010 ◽  
Vol 7 (4) ◽  
pp. 320 ◽  
Author(s):  
Markus Kleber
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Microbial Ecology ◽  
Organic Molecules ◽  
Global Scale ◽  
Critical Discussion ◽  
Environmental Drivers ◽  
Microbial Decomposition ◽  
Decomposition Of Organic Matter ◽  
Logistical Problem

Environmental context.On a global scale, soils store more carbon than plants or the atmosphere. The cycling of this vast reservoir of reduced carbon is closely tied to variations in environmental conditions, but robust predictions of climate–carbon cycle feedbacks are hampered by a lack of mechanistic knowledge regarding the sensitivity of organic matter decomposition to rising temperatures. This text provides a critical discussion of the practice to conceptualise parts of soil organic matter as intrinsically resistant to decomposition or ‘recalcitrant’. Abstract.The understanding that some natural organic molecules can resist microbial decomposition because of certain molecular properties forms the basis of the biogeochemical paradigm of ‘intrinsic recalcitrance’. In this concept paper I argue that recalcitrance is an indeterminate abstraction whose semantic vagueness encumbers research on terrestrial carbon cycling. Consequently, it appears to be advantageous to view the perceived ‘inherent resistance’ to decomposition of some forms of organic matter not as a material property, but as a logistical problem constrained by (i) microbial ecology; (ii) enzyme kinetics; (iii) environmental drivers; and (iv) matrix protection. A consequence of this view would be that the frequently observed temperature sensitivity of the decomposition of organic matter must result from factors other than intrinsic molecular recalcitrance.

scholarly journals A simple calculation algorithm to separate high-resolution CH<sub>4</sub> flux measurements into ebullition and diffusion-derived components

2016 ◽  
Author(s):  
Mathias Hoffmann ◽  
Maximilian Schulz-Hanke ◽  
Juana Garcia Alba ◽  
Nicole Jurisch ◽  
Ulrike Hagemann ◽  
...  
Keyword(s):  
Measurement Data ◽  
Flux Measurement ◽  
Open Water ◽  
Simple Calculation ◽  
Environmental Drivers ◽  
Calculation Algorithm ◽  
Wetland Ecosystems ◽  
Ch4 Emissions ◽  
Concentration Changes ◽  
And Diffusion

Abstract. Processes driving the production, transformation and transport of methane (CH4) in wetland ecosystems are highly complex. We present a simple calculation algorithm to separate open-water CH4 fluxes measured with automatic chambers into diffusion- and ebullition-derived components. This helps to reveal underlying dynamics, to identify potential environmental drivers, and thus, calculate reliable CH4 emission estimates. The flux separation is based on identification of ebullition-related sudden concentration changes during single measurements. Therefore, a variable ebullition filter is applied, using the lower and upper quartile and the interquartile range (IQR). Automation of data processing is achieved by using an established R-script, adjusted for the purpose of CH4 flux calculation. The algorithm was tested using flux measurement data (July to September 2013) from a former fen grassland site, converted into a shallow lake as a result of rewetting. Ebullition and diffusion contributed equally (46 % and 55 %) to total CH4 emissions, which is comparable to ratios given in literature. Moreover, the separation algorithm revealed a concealed shift in the diurnal trend of diffusive fluxes throughout the measurement period. The water temperature gradient was identified as one of the major drivers of diffusive CH4 emissions, whereas no significant driver was found in case of erratic CH4 ebullition events.

Characteristics of fouling due to clay-organic substances in potable water treatment by ultrafiltration

1996 ◽  
Vol 34 (9) ◽  
pp. 157-164 ◽  
Author(s):  
Kim C.-H. ◽  
M. Hosomi ◽  
A. Murakami ◽  
M. Okada
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Humic Acid ◽  
Fulvic Acid ◽  
Size Distribution ◽  
Ultrafiltration Membrane ◽  
Organic Substances ◽  
Decomposition Products ◽  
Microbial Decomposition ◽  
Fouling Materials

Effects of clay on fouling due to organic substances and clay were evaluated by model fouling materials and kaolin. Model fouling materials selected were protein, polysaccharide, fulvic acid, humic acid and algogenic matter (EOM:ectracellular organic matter, microbial decomposition products) and kaolin was selected as the clay material. Polysulfone membrane (MWCO(Molecular Weight Cut-Off) 10,000, 50,000 and 200,000) was used as an ultrafiltration membrane. In particular, the flux measurement of solutions containing algogenic matter used an ultrafiltration membrane of MWCO 50,000. The flux of protein and polysaccharide with coexistence of kaolin increased in the case of the ratio of MW/MWCO being greater than one, but did not increase in the case of the MW/MWCO ratio being below one. In contrast, the flux of fulvic acid and humic acid with coextence of kaolin decreased regardless of the ratio of MW/MWCO. The addition of dispersion agent and coagulant in the organic substances and kaolin mixture solution changed the size distribution of kaolin, and resulted in a change of the flux. EOM and microbial decomposition products decreased with the increase of the fraction of organic matter having molecular weight more than MWCO of membrane. The flux of the algogenic organic matter with coexistence of kaolin decreased with the increase of the amount of kaolin. It was suggested that the decline of the flux with coexistence of kaolin was due to the change of the resistance of the kaolin cake layer corresponding to the change in kaolin size distribution with charge.

scholarly journals Fire-Safe Polymer Composites: Flame-Retardant Effect of Nanofillers

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 540
Author(s):  
Yukyung Kim ◽  
Sanghyuck Lee ◽  
Hyeonseok Yoon
Keyword(s):  
Organic Matter ◽  
High Temperature ◽  
Flame Retardant ◽  
Flame Retardants ◽  
Combustion Process ◽  
Polymeric Materials ◽  
Fire Performance ◽  
Gaseous Species ◽  
Advantages And Disadvantages ◽  
Temperature Conditions

Currently, polymers are competing with metals and ceramics to realize various material characteristics, including mechanical and electrical properties. However, most polymers consist of organic matter, making them vulnerable to flames and high-temperature conditions. In addition, the combustion of polymers consisting of different types of organic matter results in various gaseous hazards. Therefore, to minimize the fire damage, there has been a significant demand for developing polymers that are fire resistant or flame retardant. From this viewpoint, it is crucial to design and synthesize thermally stable polymers that are less likely to decompose into combustible gaseous species under high-temperature conditions. Flame retardants can also be introduced to further reinforce the fire performance of polymers. In this review, the combustion process of organic matter, types of flame retardants, and common flammability testing methods are reviewed. Furthermore, the latest research trends in the use of versatile nanofillers to enhance the fire performance of polymeric materials are discussed with an emphasis on their underlying action, advantages, and disadvantages.

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