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Regina Katsman - One of the best experts on this subject based on the ideXlab platform.
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Methane Bubble Ascent within Fine-Grained Cohesive Aquatic Sediments: Dynamics and Controlling Factors
2019Co-Authors: Shahrazad Tarboush Sirhan, Regina Katsman, Michael LazarAbstract:Methane (CH4) is a potent greenhouse gas. Its release from Aquatic Sediments to the water column and potentially to the atmosphere, is a subject of great concern. A coupled macroscopic single-bubble mechanical/reaction-transport numerical model was used to explore the ascent of a mature CH4 bubble toward the seafloor in muddy Aquatic Sediment. Two bubble ascent scenarios were demonstrated: stable and dynamic. For small effective overburden loads (≤11 kPa), stable ascent is followed by dynamic ascent (which has not been previously demonstrated to the best of the our knowledge). This ultimately leads to the bubble being released to the water column. Higher effective overburden loads induce only stable bubble ascent, which stops at the gas horizon frequently observed below the seafloor. The depth of the gas horizon increases, while bubble rise velocity decreases with an increase in the overburden load. It is shown that the bubble migration scenario is managed predominantly by inner bubble pressure, which defines a bubble solute exchange with ambient porewaters. Predicting a bubble ascent scenario in muddy Sediment will further allow estimation of CH4 emission to the atmosphere and evaluation of changes in the effective mechanical properties of Aquatic Sediment due to the ascending bubbles
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Correlation of shape and size of methane bubbles in fine-grained muddy Aquatic Sediments with Sediment fracture toughness
Journal of Structural Geology, 2015Co-Authors: Regina KatsmanAbstract:Abstract Gassy Sediments contribute to destabilization of Aquatic infrastructure, air pollution, and global warming. In the current study a precise shape and size of the buoyant mature methane bubble in fine-grained muddy Aquatic Sediment is defined by numerical and analytical modeling, their results are in a good agreement. A closed-form analytical solution defining the bubble parameters is developed. It is found that the buoyant mature bubble is elliptical in its front view and resembles an inverted tear drop in its cross-section. The size and shape of the mature bubble strongly correlate with Sediment fracture toughness. Bubbles formed in the weaker Sediments are smaller and characterized by a larger surface-to-volume ratio that induces their faster growth and may lead to their faster dissolution below the Sediment–water interface. This may prevent their release to the water column and to the atmosphere. Shapes of the bubbles in the weaker Sediments deviate further from the spherical configuration, than those in the stronger Sediments. Modeled bubble characteristics, important for the acoustic applications, are in a good agreement with field observations and lab experiments.
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methane bubble growth in fine grained muddy Aquatic Sediment insight from modeling
Earth and Planetary Science Letters, 2013Co-Authors: Regina Katsman, Ilia Ostrovsky, Yizhaq MakovskyAbstract:Abstract Methane (CH 4 ) is the most abundant hydrocarbon and one of the most important greenhouse gases in the atmosphere. CH 4 bubble growth and migration within muddy Aquatic Sediments are closely associated with Sediment fracturing. In this paper we present the modeling of buoyancy-driven CH 4 bubble growth in fine-grained muddy Aquatic Sediment prior to the beginning of its rise. We designed a coupled mechanical/reaction-transport numerical model that enables a differential fracturing over the bubble front (as it occurs in nature), when the fracturing increment stays constant at the bubble head and subsides towards bubble tail during bubble growth. We show that this differential fracturing over the bubble front controls the bubble shape and size temporal evolution, and is significantly affected by the critical stress intensity factor of the muddy Sediment. The intercalated stages of elastic expansion and fracturing during the bubble growth shorten with time as the bubble approaches its terminal size (prior to its ascent). Our simulations reveal a high asymmetry in the bubble shape growing with time, with respect to its initial symmetric penny-shaped configuration. It was found that the bubble grows allometrically, while the importance of the bubble surface area growth with time. We also confirmed the earlier predictions about the ”inverted tear-drop” bubble cross-section just prior to the beginning of its rise. Modeling of the terminal bubble characteristics will permit prediction of the delivery of gaseous methane from the Sediment to the atmosphere via the water column.
Yizhaq Makovsky - One of the best experts on this subject based on the ideXlab platform.
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methane bubble growth in fine grained muddy Aquatic Sediment insight from modeling
Earth and Planetary Science Letters, 2013Co-Authors: Regina Katsman, Ilia Ostrovsky, Yizhaq MakovskyAbstract:Abstract Methane (CH 4 ) is the most abundant hydrocarbon and one of the most important greenhouse gases in the atmosphere. CH 4 bubble growth and migration within muddy Aquatic Sediments are closely associated with Sediment fracturing. In this paper we present the modeling of buoyancy-driven CH 4 bubble growth in fine-grained muddy Aquatic Sediment prior to the beginning of its rise. We designed a coupled mechanical/reaction-transport numerical model that enables a differential fracturing over the bubble front (as it occurs in nature), when the fracturing increment stays constant at the bubble head and subsides towards bubble tail during bubble growth. We show that this differential fracturing over the bubble front controls the bubble shape and size temporal evolution, and is significantly affected by the critical stress intensity factor of the muddy Sediment. The intercalated stages of elastic expansion and fracturing during the bubble growth shorten with time as the bubble approaches its terminal size (prior to its ascent). Our simulations reveal a high asymmetry in the bubble shape growing with time, with respect to its initial symmetric penny-shaped configuration. It was found that the bubble grows allometrically, while the importance of the bubble surface area growth with time. We also confirmed the earlier predictions about the ”inverted tear-drop” bubble cross-section just prior to the beginning of its rise. Modeling of the terminal bubble characteristics will permit prediction of the delivery of gaseous methane from the Sediment to the atmosphere via the water column.
Daryl F Dwyer - One of the best experts on this subject based on the ideXlab platform.
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survival and function of a genetically engineered pseudomonad in Aquatic Sediment microcosms
Applied and Environmental Microbiology, 1992Co-Authors: R Pipke, Irene Wagnerdobler, K N Timmis, Daryl F DwyerAbstract:Pseudomonas sp. strain B13 FR1(pFRC20P) is a genetically engineered microorganism (GEM) which is able to degrade chloro- and methylaromatics through a constructed ortho cleavage pathway. The fate of the GEM and its ability to degrade substituted aromatic compounds in two different Aquatic Sediments was investigated by using a microcosm system which consisted of intact layered Sediment cores with an overlying water column. The GEM survived in Lake Plussee and in Rhine river Sediments at densities of approximately 10(5) bacteria per g (dry weight) (1 to 5% of the total CFU) throughout a 4-week period of investigation. According to several criteria, the microcosm system was stable and healthy throughout the experiment and the addition of the GEM did not affect the total number of extractable CFU (I. Wagner-Dobler, R. Pipke, K. N. Timmis, and D. F. Dwyer, Appl. Environ. Microbiol. 58:1249-1258, 1992). When compared with uninoculated controls, the presence of the GEM enhanced the rate of degradation of a mixture of 3-chlorobenzoate and 4-methylbenzoate (25 microns each) which had been added to the water column of the Sediment cores.
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evaluation of Aquatic Sediment microcosms and their use in assessing possible effects of introduced microorganisms on ecosystem parameters
Applied and Environmental Microbiology, 1992Co-Authors: Irene Wagnerdobler, R Pipke, K N Timmis, Daryl F DwyerAbstract:In this paper we describe a Sediment microcosm system consisting of 20 undisturbed, layered Sediment cores with overlying site water which are incubated under identical conditions of temperature, light, stirring rate of overlying water, and water exchange rate. Ecosystem parameters (nutrient level, photosynthetic potential, community structure of heterotrophic bacteria, thymidine incorporation rate, and oxygen microgradients) of the laboratory microcosms and the source ecosystem were compared and shown to be indistinguishable for the first 2 weeks. In weeks 3 and 4, small differences were detectable in the nutrient level, community structure of heterotrophic bacteria, and thymidine incorporation rate. However, the photosynthetic potential, depth profiles of heterotrophic bacterial community structure, and oxygen microgradients were maintained throughout the incubation period and did not differ between laboratory microcosms and the source ecosystem. The microcosm system described here would thus appear to be a valid model of Aquatic Sediments for up to 4 weeks; the actual period would depend on the Sediment source and incubation temperature. The validated systems were used with Rhine river Sediment to assess possible effects on ecosystem parameters of Pseudomonas sp. strain B13 FR1(pFRC20P), a genetically engineered microorganism (GEM) that had been constructed to degrade mixtures of halo- and alkylbenzoates and -phenols. The GEM survived in the surface Sediment at densities of 5 x 10(4) to 5 x 10(5)/g (dry weight) for 4 weeks and degraded added chloro- and methylaromatics. The GEM did not measurably influence ecosystem parameters such as photosynthesis, densities of selected heterotrophic bacteria, thymidine incorporation rate, and oxygen microgradients. Thus, the microcosm system described here would seem to be useful for the study of the ecology of biodegradation and the fate and effect of microorganisms introduced into the environment.
Ilona Fekete - One of the best experts on this subject based on the ideXlab platform.
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sequential extraction studies on Aquatic Sediment and biofilm samples for the assessment of heavy metal mobility
Microchemical Journal, 2013Co-Authors: Mark Horvath, Gabor J Halasz, Eva Kucanova, Beata Kucikova, Ilona FeketeAbstract:Abstract Aquatic Sediment samples and biofilms from two sampling sites representing different environmental situations (Kosice, Slovakia and Godollő, Hungary) were studied on their heavy metal content. Fractionation of the metallic content of the samples was done by the improved three-step BCR sequential extraction procedure supplemented with microwave-assisted HNO3/H2O2 digestion and another three-step method using supercritical CO2, subcritical H2O and their mixture, pseudototal element content was gained by microwave-assisted HNO3/H2O2 digestion of the original samples. Influence of the sample–extractant ratio on the extracted elements' concentration in the BCR procedure was also studied. The sum of concentrations for Zn, Pb, Ni and Cu in the biofilm extracts of the (3 + 1)-step BCR procedure was in most cases higher than the pseudototal concentrations, so that the sequential extraction may be more effective than the single-step HNO3/H2O2 digestion. Lower sample–extractant ratios may increase the efficiency of the BCR method. The estimated easily mobilizable element content provided by the two sequential procedures (first step of the BCR with 0.11 mol dm− 3 acetic acid and second and third steps of the alternative method with H2O and H2O + CO2, respectively) was similar in case of Cd, Ni and Cu in both biofilm and Sediment samples.
Ilia Ostrovsky - One of the best experts on this subject based on the ideXlab platform.
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methane bubble growth in fine grained muddy Aquatic Sediment insight from modeling
Earth and Planetary Science Letters, 2013Co-Authors: Regina Katsman, Ilia Ostrovsky, Yizhaq MakovskyAbstract:Abstract Methane (CH 4 ) is the most abundant hydrocarbon and one of the most important greenhouse gases in the atmosphere. CH 4 bubble growth and migration within muddy Aquatic Sediments are closely associated with Sediment fracturing. In this paper we present the modeling of buoyancy-driven CH 4 bubble growth in fine-grained muddy Aquatic Sediment prior to the beginning of its rise. We designed a coupled mechanical/reaction-transport numerical model that enables a differential fracturing over the bubble front (as it occurs in nature), when the fracturing increment stays constant at the bubble head and subsides towards bubble tail during bubble growth. We show that this differential fracturing over the bubble front controls the bubble shape and size temporal evolution, and is significantly affected by the critical stress intensity factor of the muddy Sediment. The intercalated stages of elastic expansion and fracturing during the bubble growth shorten with time as the bubble approaches its terminal size (prior to its ascent). Our simulations reveal a high asymmetry in the bubble shape growing with time, with respect to its initial symmetric penny-shaped configuration. It was found that the bubble grows allometrically, while the importance of the bubble surface area growth with time. We also confirmed the earlier predictions about the ”inverted tear-drop” bubble cross-section just prior to the beginning of its rise. Modeling of the terminal bubble characteristics will permit prediction of the delivery of gaseous methane from the Sediment to the atmosphere via the water column.