The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform
Xuan Zheng - One of the best experts on this subject based on the ideXlab platform.
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Studies on the sorption behaviors of phenanthrene on Marine Sediments.
Environmental Toxicology and Chemistry, 2010Co-Authors: Gui-peng Yang, Xuan ZhengAbstract:In the present study, the sorption behaviors of phenanthrene on Marine Sediments were investigated. Through the study of the adsorption kinetics and isotherms, the adsorption mechanism of phenanthrene on Marine Sediments was described. The results showed that the adsorption kinetics of phenanthrene on Marine Sediments could be described by the second-order kinetic equation. The sorption rate of phenanthrene was very rapid, and the equilibrium time was slightly longer in deionized water than in natural seawater. The adsorption isotherms of phenanthrene on all the Sediments could be very well described by Freundlich equations. The adsorption capacity of phenanthrene had a significant positive correlation with the sediment organic carbon content. Some external factors that could affect adsorption behaviors of phenanthrene were also investigated. Results of the present study showed that the adsorption capacity of phenanthrene on the sediment decreased with increasing temperature. Moreover, the adsorption amounts of phenanthrene on the sediment appeared to be lower in natural seawater than in deionized water. Finally, the presence of the surfactant of Tween20 in the system could enhance the adsorption of phenanthrene on the sediment, and the adsorbance was proportional to the concentration of Tween20. Environ. Toxicol. Chem. 2010;29:2169–2176. © 2010 SETAC
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Studies on the sorption behaviors of phenanthrene on Marine Sediments.
Environmental toxicology and chemistry, 2010Co-Authors: Gui-peng Yang, Xuan ZhengAbstract:In the present study, the sorption behaviors of phenanthrene on Marine Sediments were investigated. Through the study of the adsorption kinetics and isotherms, the adsorption mechanism of phenanthrene on Marine Sediments was described. The results showed that the adsorption kinetics of phenanthrene on Marine Sediments could be described by the second-order kinetic equation. The sorption rate of phenanthrene was very rapid, and the equilibrium time was slightly longer in deionized water than in natural seawater. The adsorption isotherms of phenanthrene on all the Sediments could be very well described by Freundlich equations. The adsorption capacity of phenanthrene had a significant positive correlation with the sediment organic carbon content. Some external factors that could affect adsorption behaviors of phenanthrene were also investigated. Results of the present study showed that the adsorption capacity of phenanthrene on the sediment decreased with increasing temperature. Moreover, the adsorption amounts of phenanthrene on the sediment appeared to be lower in natural seawater than in deionized water. Finally, the presence of the surfactant of Tween20 in the system could enhance the adsorption of phenanthrene on the sediment, and the adsorbance was proportional to the concentration of Tween20.
Gui-peng Yang - One of the best experts on this subject based on the ideXlab platform.
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Influence of coexisting contaminants on the sorption of 17β-estradiol by Marine Sediments
Journal of Environmental Science and Health Part A-toxic\ hazardous Substances & Environmental Engineering, 2010Co-Authors: Quan Li, Gui-peng YangAbstract:The adsorption behavior of 17β-estradiol (E2) on Marine Sediments treated by different methods was investigated in the presence of bisphenol A (BPA), dibutyl phthalate (DBP), cationic surfactant cetyltrimethylammonium bromide (CTAB), nonionic surfactant polyoxyethylene (80) sorbitan esters (Tween 80) and anionic surfactant sodium dodecylbenzene sulfonate (SDBS). Four sets of experiments were conducted to determine the adsorption isotherms of E2 with coexisting contaminants, to explore the effects of concentrations and types of coexisting contaminants on the E2 adsorption capacity, and to examine the influence of pH on E2 adsorption on the Sediments. The adsorption behavior of E2 to Marine Sediments without the addition of surfactant mainly related to organic carbon content of Sediments and fitted well with the Freundlich model. The presence of CTAB or Tween 80 enhanced the adsorption capacity of E2 of Marine Sediments. In contrast, the presence of BPA, DBP and SDBS inhibited the adsorption capacity of E2....
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Influence of coexisting contaminants on the sorption of 17β-estradiol by Marine Sediments
Journal of environmental science and health. Part A Toxic hazardous substances & environmental engineering, 2010Co-Authors: Gui-peng YangAbstract:The adsorption behavior of 17β-estradiol (E2) on Marine Sediments treated by different methods was investigated in the presence of bisphenol A (BPA), dibutyl phthalate (DBP), cationic surfactant cetyltrimethylammonium bromide (CTAB), nonionic surfactant polyoxyethylene (80) sorbitan esters (Tween 80) and anionic surfactant sodium dodecylbenzene sulfonate (SDBS). Four sets of experiments were conducted to determine the adsorption isotherms of E2 with coexisting contaminants, to explore the effects of concentrations and types of coexisting contaminants on the E2 adsorption capacity, and to examine the influence of pH on E2 adsorption on the Sediments. The adsorption behavior of E2 to Marine Sediments without the addition of surfactant mainly related to organic carbon content of Sediments and fitted well with the Freundlich model. The presence of CTAB or Tween 80 enhanced the adsorption capacity of E2 of Marine Sediments. In contrast, the presence of BPA, DBP and SDBS inhibited the adsorption capacity of E2. The pH value of the solution could influence the adsorption behavior of E2 of the Marine Sediments. A decline in pH values was beneficial to the adsorption of E2 with the addition of surfactants.
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Studies on the sorption behaviors of phenanthrene on Marine Sediments.
Environmental Toxicology and Chemistry, 2010Co-Authors: Gui-peng Yang, Xuan ZhengAbstract:In the present study, the sorption behaviors of phenanthrene on Marine Sediments were investigated. Through the study of the adsorption kinetics and isotherms, the adsorption mechanism of phenanthrene on Marine Sediments was described. The results showed that the adsorption kinetics of phenanthrene on Marine Sediments could be described by the second-order kinetic equation. The sorption rate of phenanthrene was very rapid, and the equilibrium time was slightly longer in deionized water than in natural seawater. The adsorption isotherms of phenanthrene on all the Sediments could be very well described by Freundlich equations. The adsorption capacity of phenanthrene had a significant positive correlation with the sediment organic carbon content. Some external factors that could affect adsorption behaviors of phenanthrene were also investigated. Results of the present study showed that the adsorption capacity of phenanthrene on the sediment decreased with increasing temperature. Moreover, the adsorption amounts of phenanthrene on the sediment appeared to be lower in natural seawater than in deionized water. Finally, the presence of the surfactant of Tween20 in the system could enhance the adsorption of phenanthrene on the sediment, and the adsorbance was proportional to the concentration of Tween20. Environ. Toxicol. Chem. 2010;29:2169–2176. © 2010 SETAC
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Studies on the sorption behaviors of phenanthrene on Marine Sediments.
Environmental toxicology and chemistry, 2010Co-Authors: Gui-peng Yang, Xuan ZhengAbstract:In the present study, the sorption behaviors of phenanthrene on Marine Sediments were investigated. Through the study of the adsorption kinetics and isotherms, the adsorption mechanism of phenanthrene on Marine Sediments was described. The results showed that the adsorption kinetics of phenanthrene on Marine Sediments could be described by the second-order kinetic equation. The sorption rate of phenanthrene was very rapid, and the equilibrium time was slightly longer in deionized water than in natural seawater. The adsorption isotherms of phenanthrene on all the Sediments could be very well described by Freundlich equations. The adsorption capacity of phenanthrene had a significant positive correlation with the sediment organic carbon content. Some external factors that could affect adsorption behaviors of phenanthrene were also investigated. Results of the present study showed that the adsorption capacity of phenanthrene on the sediment decreased with increasing temperature. Moreover, the adsorption amounts of phenanthrene on the sediment appeared to be lower in natural seawater than in deionized water. Finally, the presence of the surfactant of Tween20 in the system could enhance the adsorption of phenanthrene on the sediment, and the adsorbance was proportional to the concentration of Tween20.
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Notice of Retraction Sorption of nonylphenol on Marine Sediments
2010 The 2nd Conference on Environmental Science and Information Application Technology, 2010Co-Authors: Hai-yan Ding, Gui-peng Yang, Qiong-yao DingAbstract:Sorption of nonylphenol (NP), a toxic endocrine disruptor, on Marine Sediments was studied through series of experiments. The sorption isotherms can be described by three models: linear model, Freundlich model and Langmuir model. The sorption amount of NP on the three sediment samples was in proportion to the organic carbon content of Sediments. The adsorption ability of Sediments with different grain sizes had positive correlation with organic carbon content. Moreover, the sorption of NP on Marine Sediments increased with the increase of salinity and the decline of temperature.
Stefan Schouten - One of the best experts on this subject based on the ideXlab platform.
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Constraints on the sources of branched tetraether membrane lipids in distal Marine Sediments
Organic Geochemistry, 2014Co-Authors: Johan W.h. Weijers, Enno Schefuß, Jung-hyun Kim, Jaap S. Sinninghe Damsté, Stefan SchoutenAbstract:Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are membrane lipids produced by soil bacteria and occur in near coastal Marine Sediments as a result of soil organic matter input. Their abundance relative to Marine-derived crenarchaeol, quantified in the BIT index, generally decreases offshore. However, in distal Marine Sediments, low relative amounts of brGDGTs can often still be observed. Sedimentary in situ production as well as dust input have been suggested as potential, though as yet not well constrained, sources. In this study brGDGT distributions in dust were examined and compared with those in distal Marine Sediments. Dust was sampled along the equatorial West African coast and brGDGTs were detected in most of the samples, albeit in low abundance. Their degree of methylation and cyclisation, expressed in the MBT' (methylation index of branched tetraethers) and DC (degree of cyclisation) indices, respectively, were comparable with those for African soils, their presumed source. Comparison of DC index values for brGDGTS in global soils, Congo deep-sea river fan Sediments and dust with those of distal Marine Sediments clearly showed, however, that distal Marine Sediments had significantly higher values. This distinctive distribution is suggestive of sedimentary in situ production as a source of brGDGTs in Marine Sediments, rather than dust input. The presence of in situ produced brGDGTs in Marine Sediments means that caution should be exercised when applying the MBT'–CBT palaeothermometer to Sediments with low BIT index values, i.e. < 0.1, based on our dataset.
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Constraints on the sources of branched tetraether membrane lipids in distal Marine Sediments
Organic Geochemistry, 2014Co-Authors: Johan W.h. Weijers, Enno Schefuß, Jung-hyun Kim, Jaap S. Sinninghe Damsté, Stefan SchoutenAbstract:Abstract Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are membrane lipids produced by soil bacteria and occur in near coastal Marine Sediments as a result of soil organic matter input. Their abundance relative to Marine-derived crenarchaeol, quantified in the BIT index, generally decreases offshore. However, in distal Marine Sediments, low relative amounts of brGDGTs can often still be observed. Sedimentary in situ production as well as dust input have been suggested as potential, though as yet not well constrained, sources. In this study brGDGT distributions in dust were examined and compared with those in distal Marine Sediments. Dust was sampled along the equatorial West African coast and brGDGTs were detected in most of the samples, albeit in low abundance. Their degree of methylation and cyclisation, expressed in the MBT′ (methylation index of branched tetraethers) and DC (degree of cyclisation) indices, respectively, were comparable with those for African soils, their presumed source. Comparison of DC index values for brGDGTS in global soils, Congo deep-sea river fan Sediments and dust with those of distal Marine Sediments clearly showed, however, that distal Marine Sediments had significantly higher values. This distinctive distribution is suggestive of sedimentary in situ production as a source of brGDGTs in Marine Sediments, rather than dust input. The presence of in situ produced brGDGTs in Marine Sediments means that caution should be exercised when applying the MBT′–CBT palaeothermometer to Sediments with low BIT index values, i.e.
Kefeng Yan - One of the best experts on this subject based on the ideXlab platform.
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Decomposition conditions of methane hydrate in Marine Sediments from South China Sea
Fluid Phase Equilibria, 2016Co-Authors: Yu Zhang, Yi Wang, Zhao-yang Chen, Kefeng YanAbstract:Abstract Decomposition conditions of methane hydrate in Marine Sediments from South China Sea were measured using multi-step decomposition method. Four different samples of the Marine Sediments were used in the experiments. The pore distribution, the surface area, particle size and the surface texture were measured and observed. The experimental results indicated that the final decomposition temperatures are shifted lower than those for bulk hydrates at the same pressure for different Marine Sediments and different water saturations. Temperature shifts are more negative for smaller initial water saturation. The surface textures and pore of the Sediments both affect the equilibrium condition of methane hydrate. Using the Clausius-Clapeyron equation, the enthalpy of hydrate dissociation in Marine Sediments was calculated. It was found that the enthalpy of hydrate dissociation in Marine Sediments with lower water saturation is higher than that at the bulk state.
Karen G. Lloyd - One of the best experts on this subject based on the ideXlab platform.
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predominant archaea in Marine Sediments degrade detrital proteins
Nature, 2013Co-Authors: Karen G. Lloyd, Lars Schreiber, Dorthe Groth Petersen, Kasper Urup Kjeldsen, Mark A. Lever, Andrew D. Steen, Ramunas Stepanauskas, Michael Richter, Sara KleindienstAbstract:Half of the microbial cells in the Earth’s oceans are found in Sediments 1 . Many of these cells are members of the Archaea 2 , singlecelled prokaryotes in a domain of life separate from Bacteria and Eukaryota. However, most of these archaea lack cultured representatives, leaving their physiologies and placement on the tree of life uncertain. Here we show that the uncultured miscellaneous crenarchaeotal group (MCG) and Marine benthic group-D (MBG-D) are among the most numerous archaea in the Marine sub-sea floor. Single-cell genomic sequencing of one cell of MCG and three cells of MBG-D indicated that they form new branches basal to the archaeal phyla Thaumarchaeota 3 and Aigarchaeota 4 , for MCG, and the order Thermoplasmatales, for MBG-D. All four cells encoded extracellular protein-degrading enzymes such as gingipain and clostripain that are known to be effective in environments chemically similar to Marine Sediments. Furthermore, we found these two types of peptidase to be abundant and active in Marine Sediments, indicating that uncultured archaea may have a previously undiscovered role in protein remineralization in anoxic Marine Sediments. In the cold anoxic Sediments underlying most of the Earth’s oceans, the only metabolisms known for cultured archaea are methane production from simple carbon substrates, and methane consumption 5 . Recent isotopic evidence, however, has shown that sedimentary archaea can be heterotrophic 6 , but potential carbon substrates remain
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Predominant archaea in Marine Sediments degrade detrital proteins
Nature, 2013Co-Authors: Karen G. Lloyd, Lars Schreiber, Dorthe Groth Petersen, Kasper Urup Kjeldsen, Mark A. Lever, Andrew D. Steen, Ramunas Stepanauskas, Michael Richter, Sara Kleindienst, Sabine LenkAbstract:Half of the microbial cells in the Earth's oceans are found in Sediments. Many of these cells are members of the Archaea, single-celled prokaryotes in a domain of life separate from Bacteria and Eukaryota. However, most of these archaea lack cultured representatives, leaving their physiologies and placement on the tree of life uncertain. Here we show that the uncultured miscellaneous crenarchaeotal group (MCG) and Marine benthic group-D (MBG-D) are among the most numerous archaea in the Marine sub-sea floor. Single-cell genomic sequencing of one cell of MCG and three cells of MBG-D indicated that they form new branches basal to the archaeal phyla Thaumarchaeota and Aigarchaeota, for MCG, and the order Thermoplasmatales, for MBG-D. All four cells encoded extracellular protein-degrading enzymes such as gingipain and clostripain that are known to be effective in environments chemically similar to Marine Sediments. Furthermore, we found these two types of peptidase to be abundant and active in Marine Sediments, indicating that uncultured archaea may have a previously undiscovered role in protein remineralization in anoxic Marine Sediments.
