•AFT data from the Qilian Shan indicate stepwise northeastward growth of the northeastern Tibetan Plateau since the early Eocene, corresponding to India–Eurasia collision.•Rapid cooling during ...Cretaceous corresponds to the collision of the Lhasa block with the Eurasian.•Rapid cooling since early Eocene in the South Qilian Shan corresponds to India–Eurasia collision.•The study results shed light on the tectonic evolution of the Qilian Shan.
Apatite fission track (AFT) data from hinterland of the Qilian Shan at the northeastern margin of the Tibetan Plateau suggest this range has experienced northeastward propagation of surface uplift since early Eocene and that crustal shortening occurred in the Qilian Shan before the late Miocene. Thermochronometry data indicate that the Qilian Shan experienced a three-stage cooling history, including: (1) rapid initial cooling during Cretaceous; (2) a stage of slow cooling during late Cretaceous–early Eocene; and (3) rapid stepwise cooling in a southwestern–northeastern orientation since early Eocene. Cretaceous rapid cooling may be a record of the Lhasa block and Eurasian collision. Early Cretaceous denudation was followed by tectonic and quasi-isothermal quiescence that continued until early Eocene. Early Eocene rapid cooling in the South Qilian Shan may be the first far-field response in the Qilian Shan to the collision and convergence of the Indian and Eurasian continents. From late Eocene to middle Miocene, crustal shortening propagated into the Central Qilian Shan and North Qilian Shan and produced surface uplift of the entire Qilian Shan region before the late Miocene. This study provides a better understanding of the tectonic evolution of the Qilian Shan and when the far-field stress from the India–Eurasia collision into the northeastern Tibetan Plateau began.
Mariculture activities and river inputs lead to coastal seawaters with DOM levels that are comparable to or even higher than those in terrestrial water bodies. However, effects of seawater DOM, and ...especially of DOM occurring in areas impacted by mariculture, on photodegradation of organic micropollutants, are largely unknown. In this study, simulated sunlight irradiation experiments were performed to probe the effects of DOM extracted from mariculture impacted seawaters and from offshore areas, on photodegradation of three sulfonamide antibiotics (SAs). Results show that the SAs are transformed mainly by indirect photodegradation induced by triplet excited DOM (3DOM*). Compared with DOM from the more pristine coastal waters, the DOM from mariculture impacted areas undergoes less photobleaching, contains higher percentage of humic-like materials and higher proportions of aromatic and carbonyl structures. Thus, the DOM from mariculture areas exhibits higher rates of light absorption, higher formation quantum yields of 3DOM*, higher 3DOM* steady-state concentrations and higher reactivity on photodegradation of the SAs. Photochemistry of the seawater DOM is different from that reported for freshwater lake DOM. This study highlights the importance of probing the effects of DOM from coastal seawaters on photodegradation of organic micropollutants since coastal seawaters are sinks of many aquatic pollutants.
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•DOM were isolated from mariculture ponds, tidal creek waters and offshore waters.•Effects of DOM in coastal waters on photodegradation of pollutants were unveiled.•DOM from mariculture areas has higher aromaticity than those from offshore waters.•DOM from mariculture areas exhibits high reactivity on degradation of sulfonamides.
The main idea of membrane distillation is to use a porous hydrophobic membrane as a barrier that isolates vapor from aqueous solutions. It is similar to the evaporation process from a free water ...surface but introduces solid-liquid interfaces and solid-vapor interfaces to a liquid-vapor interface. The transmembrane mass flux of a membrane-distillation process is affected by the membrane's intrinsic properties and the temperature gradient across the membrane. It is interesting and important to know whether the evaporation process of membrane distillation is faster or slower than that of a free-surface evaporation under the same conditions and know the capacity of the transmembrane mass flux of a membrane-distillation process. In this work, a set of proof-of-principle experiments with various water surface/membrane interfacial conditions is performed. The effect and mechanism of membrane-induced evaporation are investigated. Moreover, a practical engineering model is proposed based on mathematical fitting and audacious simplification, which reflects the capacity of transmembrane flux.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
To gain a better understanding of the chemical structural composition and reactivity of sedimentary organic matter in coastal environments, the properties of sedimentary humic substances (HSs) ...isolated from contrasting coastal marine environments (i.e., salt marsh estuary, continental shelf, and continental slope) in China were investigated and compared. The complementary analytical approaches employed included elemental analysis, cross polarization magic angle spinning (CP/MAS)-
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C nuclear magnetic resonance, pyrolysis-gas chromatography–mass spectrometry, and potentiometric titrations. The results indicate that HSs isolated from the salt marsh site in the Changjiang Estuary, which is strongly influenced by terrestrial river inputs, had the highest content of lignin-derived components, such as phenols and alkyl phenols, and acidic functional groups; HSs from the continental slope site in the South China Sea, which mainly originated from the inputs of marine algae and planktons, contained the highest level of aliphatic compounds, carbohydrates, and nitrogen-containing compounds; however, HSs from the continental shelf site in the East China Sea presented a mixture of both land and marine properties due to the influence of the two sources. Humic acids were found to contain comparatively more highly branched, long-chain aliphatic components but fewer oxygen-containing functional groups, such as carboxyl groups, and fewer sulfur-containing compounds than their fulvic acid counterparts. The total concentrations of proton binding sites and the structural characteristics of the studied HSs may provide insights into the migration and fate of HS-bound contaminants, such as heavy metals and organic pollutants, in coastal marine systems.
The quantity and quality of dissolved organic matter (DOM) in the brine of solar ponds influence the efficiency of mineral extraction and brine evaporation rates. Here we report a characterization ...study of DOM in solar ponds of oilfield-produced brines using different approaches. The results showed that the concentrations of dissolved organic carbon and total dissolved solids exhibited a 2–3 fold increase with exposure time in the ponds. Analyses with two-dimensional correlation spectroscopy of attenuated total reflectance Fourier transform infrared spectroscopy and proton nuclear magnetic resonance, indicated that the aromatic and carboxylic acid structures in the DOM, were more susceptible to degradation/transformation compared with aliphatics, while aliphatics exhibited a preferential decline with increasing exposure time in the solar ponds. The relative abundance of aliphatic compounds (including functionalized ones) gradually decreased by 17.1% (r = −0.94, P < 0.001), in the solar pond process, while the opposite was observed for carbohydrates, which increased by 88.7% (r = 0.93, P < 0.001). Pyrolysis–gas chromatography–mass spectrometry revealed that the DOM in oilfield-produced brine contained polymethylene chain, terpenoid-like, carbohydrate (or carbohydrate-like) and aromatic structures. Terpenoid-like compounds were depleted while isoprenoid and linear polymethylene chain compounds increased upon irradiation in solar ponds. Finally, the guidelines for removing DOM from brine, and their ecological impacts and consequences in the process of brine resource exploitation, were discussed.
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•The abundance, composition and variation of DOM in solar ponds were investigated.•Twelve classes of Py products, including 200 individual compounds were identified.•DOM in brine was composed mainly of carbohydrates, other aliphatics, and aromatics.•The variations of different groups in solar pond depended on DOM composition.•Microbiological processes were subordinate to photo-induced DOM transformations.
It has been identified that temperature polarization and concentration polarization are typical near-surface phenomena limiting the performance of membrane distillation. The module design should ...allow for effective flow, reducing the polarization effects near the membrane surfaces and avoiding high hydrostatic pressure drops across and along the membrane surfaces. A potential route to enhancing the membrane distillation performance is geometry modification on the flow channel by employing baffles as vortex generators, reducing the polarization effects. In this work, various baffles with different structures were fabricated by 3D printing and attached to the feed flow channel shell in an air gap membrane distillation module. The hydrodynamic characteristics of the modified flow channels were systematically investigated via computational fluid dynamics simulations with various conditions. The membrane distillation tests show that adding the baffles to the feed channel can effectively increase the transmembrane flux. The transmembrane flux with rectangular baffles and shield-shaped baffles increases by 21.8% and 28.1% at the feed temperature of 70 °C. Moreover, the shield-shaped baffles in the flow channel not only enhance the transmembrane flux but also maintain a low-pressure drop, making it even more significant.
Membrane distillation (MD) processes need a relatively mild temperature gradient as the driving force for desalination. In the field, it is reasonable to utilize solar energy as the heat source for ...the feed, and seawater as the infinite cold source for condensation. Solar-driven MD provides a route for the practical application of seawater desalination at a small scale. In this work, we focus on floating MD modules with a solar heating bag as the power source, and perform proof-of-principle experiments on the MD performance under various conditioning parameters, including feed flow rate, feed temperature, salinity, air gap, and sea waves. The results indicate that floating solar-driven MD modules are feasible in terms of permeate flux and salt rejection ratio, and the upward evaporation MD configuration leads to a better performance in terms of permeate flux. The simulation and experiments also show that the natural sea waves disturb the heating bag and the MD module floating on the surface of seawater, and effectively enhance the feed circulation and transport in the system.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Vanillin dehydrogenase (VDH) is a crucial enzyme involved in the degradation of lignin-derived aromatic compounds. Herein, the VDH from Corynebacterium glutamicum was characterized. The relative ...molecular mass (Mr) determined by SDS-PAGE was ~51 kDa, whereas the apparent native Mr values revealed by gel filtration chromatography were 49.5, 92.3, 159.0 and 199.2 kDa, indicating the presence of dimeric, trimeric and tetrameric forms. Moreover, the enzyme showed its highest level of activity toward vanillin at pH 7.0 and 30°C, and interestingly, it could utilize NAD(+) and NADP(+) as coenzymes with similar efficiency and showed no obvious difference toward NAD(+) and NADP(+). In addition to vanillin, this enzyme exhibited catalytic activity toward a broad range of substrates, including p-hydroxybenzaldehyde, 3,4-dihydroxybenzaldehyde, o-phthaldialdehyde, cinnamaldehyde, syringaldehyde and benzaldehyde. Conserved catalytic residues or putative cofactor interactive sites were identified based on sequence alignment and comparison with previous studies, and the function of selected residues were verified by site-directed mutagenesis analysis. Finally, the vdh deletion mutant partially lost its ability to grow on vanillin, indicating the presence of alternative VDH(s) in Corynebacterium glutamicum. Taken together, this study contributes to understanding the VDH diversity from bacteria and the aromatic metabolism pathways in C. glutamicum.
Temperature and concentration polarizations near the membrane surface zone can significantly affect the performance of membrane distillation, resulting in reduced transmembrane flux and overall ...efficiency. The fundamental approach to mitigating near-surface polarizations involves enhancing turbulence flow near the membrane surface to minimize the formation of polarization layers. This study focuses on modifying the membrane surface via surface decoration to reduce the polarization layers. The effects of membrane surface decoration on the performance of membrane distillation were systematically investigated through an air gap membrane distillation module under various operating conditions. The hydrodynamic characteristics of the flow near the membrane surface were studied using computational fluid dynamics simulations. The characteristics of both bottom-up and top-down disturbing configurations were analyzed. In addition, we investigated the influence of various flow disturbing methods on the mass transfer coefficient in membrane distillation processes. The membrane distillation test results show that at feed temperatures of 50 °C and 70 °C, there are respective increases in transmembrane flux of 30 % and 12 %. The results provide insights into optimizing the flow state near the membrane surface for enhanced membrane distillation performance.
•Mitigating near-surface polarizations through membrane surface decoration•Comparisons between bottom-up and top-down disturbing configurations•Membrane surface decoration yields a negligible increase in pressure drop.
Ohr, a bacterial protein encoded by the Organic Hydroperoxide Resistance (ohr) gene, plays a critical role in resistance to organic hydroperoxides. In the present study, we show that the Cys-based ...thiol-dependent Ohr of Corynebacterium glutamicum decomposes organic hydroperoxides more efficiently than hydrogen peroxide. Replacement of either of the two Cys residues of Ohr by a Ser residue resulted in drastic loss of activity. The electron donors supporting regeneration of the peroxidase activity of the oxidized Ohr of C. glutamicum were principally lipoylated proteins (LpdA and Lpd/SucB). A Δohr mutant exhibited significantly decreased resistance to organic hydroperoxides and marked accumulation of reactive oxygen species (ROS) in vivo; protein carbonylation was also enhanced notably. The resistance to hydrogen peroxide also decreased, but protein carbonylation did not rise to any great extent. Together, the results unequivocally show that Ohr is essential for mediation of organic hydroperoxide resistance by C. glutamicum.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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