Guangzhou Institute of Geochemistry
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Unveiling the role of oxygen vacancies on different crystal planes of ceria in catalytic toluene oxidation: Evidence from molecular dynamics and in situ DRIFTS
No full textOxygen vacancy defect engineering is an efficient tactic in metal oxide catalysts for the oxidation of volatile organic compounds (VOCs). Herein, a series of CeO2 catalysts with different dominant crystal planes ((111), (220), (311), and (200)) were successfully synthesized via a facile one-step hydrothermal method. The catalytic oxidation performance for toluene followed the order: (111) > (220) > (311) > (200). Molecular dynamics simulation directly demonstrated that toluene molecule was more readily adsorbed on the (111) crystal planes of CeO2 at actual reaction temperature. The characterization results revealed the local microenvironment of oxygen vacancy could be tailored by different exposed crystal planes, in which (111) crystal planes could induce more coordinative unsaturated sites and then generate more Ce3+-V-O-Ce4+ sites. The in-situ DRIFT spectra further elucidated the catalytic toluene oxidation pathways over these CeO2 catalysts. For the NC-CeO2 (200) catalyst, the insufficient oxygen vacancies made it difficult for gaseous oxygen to backfill onto the surface of catalyst, which induced dehydrogenation of methyl group was the rate-determining step. While the toluene on the surface of NP-CeO2 (111) could be immediately transformed into benzyl alcohol. With the assistance of electrophilic oxygen species, the benzyl alcohol was further oxidized into benzaldehyde, benzoic acid, maleic anhydride, H2O, and CO2. This work provides valuable insights into the design of efficient CeO2 catalysts for VOCs degradation and advances the understanding of their catalytic mechanisms
Microstructural and Seismic Characteristics of Mantle Xenoliths From Damaping Area, and Their Geodynamic Implications of North China Craton Destruction
No full textThe large-volume lithospheric mantle xenoliths around the Damaping area provides valuable insights into the detailed destruction progression of the North China Craton (NCC). This paper presents a quantitative analysis of the microstructural and seismic properties of oriented mantle xenoliths (with distinct foliation and lineation). The selected peridotites all have coarse-grained textures. The olivine crystallographic preferred orientations (CPOs) are predominantly axial-[010] type (or AG-type), with all xenoliths have girdled [100]OL and [001]OL characteristics. B-type olivine CPO is newly discovered in the research area. Analysis of crystallographic vorticity axis (CVA) projections indicates that more than half of Damaping xenoliths have CVA maxima (sub)parallel to the lineation. These microstructure characteristics suggest that B-type CPOs were formed before the onset of pure shear-dominated transpression and pyroxene restriction, which significantly influenced the lithospheric mantle evolution. The upwelling asthenosphere beneath Eastern Block of the NCC not only delaminated its lithospheric mantle but also experienced rollback and flowed along the WNW-SEE direction. This progression likely serves as the primary driving force of transpression. If foliation were vertical and lineation were horizontal, the valid S-wave anisotropies range is 5%-12%. All selected samples are spinel facies, resulting in a maximum in situ depth of 90 km, and the calculated SKS splitting delay times (0.5-1.3 s) align with previous seismological observations. The SKS direction in the research area is predominantly oriented perpendicular (NNE-SSW) to the flow direction of nearby asthenosphere. These characteristics are likely attributed to transpression. Therefore, the "fossil" anisotropy may have developed after the cessation of transpression
Hydrothermal pretreatment for enhanced thermochemical or biochemical conversion of pharmaceutical biowastes into fuels, fertilizers, and carbon materials
No full textPharmaceutical biowastes, rich in organic matter and high in moisture, are typical light industry byproducts with waste and renewable attributes. Thermochemical and biochemical conversion technologies transform these residues into value-added bioproducts, including biofuels, biofertilizers, and bio-carbon materials. Hydrothermal pretreatment effectively removes toxic substances and enhances feedstock for these processes. This review comprehensively examines its role in improving the formation of bioproducts from pharmaceutical biowastes, focusing on (i) upgrading and denitrogenating solid biofuels with better combustion performance; (ii) enhancing biodegradability and gaseous biofuel production via organic matter decomposition; (iii) enriching soluble carbon and nitrogen for liquid biofertilizer; (iv) eliminating antibiotic residues and reducing antibiotic resistance in solid biofertilizers; and (v) stabilizing carbon and nitrogen structures and optimizing pore characteristics for functionalized carbon materials. The review recommends a potential staged thermochemical approach to co-produce nitrogen-enriched liquid biofertilizers and porous carbon materials from pharmaceutical biowastes. Hydrothermal pretreatment emerges as a key technique for facilitating the migration and conversion of essential elements like carbon and nitrogen. This study reveals the potential of hydrothermal pretreatment to address the limitations of pharmaceutical biowastes and offers insights into their valorization
A Novel Land Surface Temperature Retrieval Algorithm for SDGSAT-1 Images
No full textLand surface temperature (LST) is a crucial parameter influencing Earth-atmosphere interactions and energy balance processes. The Sustainable Development Goals Science Satellite 1 (SDGSAT-1) was recently launched to support the realization of the United Nations Sustainable Development Goals (SDGs), which provides worldwide three-spectrum wide-swath, high-resolution, and high-sensitivity thermal infrared (TIR) images. The objective of this study is to develop a modified three-channel split-window algorithm incorporating atmospheric water vapor content (W-TCSW) for LST retrieval from SDGSAT-1 images. This algorithm was developed from the existing split-window (SW) form. The parameters of the algorithm were determined based on the MODerate resolution atmospheric TRANsmission (MODTRAN) simulation results of 946 Thermodynamic Initial-Guess Retrieval (TIGR) atmospheric profiles. The W-TCSW algorithm was comprehensively compared with the SW and three-channel SW (TCSW) algorithms. The retrieval results of the three algorithms were validated with simulated datasets and in situ measurements from the Heihe Watershed Allied Telemetry Experimental Research (HiWATER) sites in China and the Surface Radiation Budget Network (SURFRAD) sites in USA. The SDGSAT-1 data retrieved by the W-TCSW algorithm was also intercompared with Landsat and ECOSTRESS LST products. The W-TCSW algorithm demonstrated the highest accuracy among the three retrieval algorithms (SW, TCSW, and W-TCSW). The influences of atmospheric water vapor content (AWVC) and land surface emissivity (LSE) as well as land use and land cover (LULC) on retrieval algorithms were discussed in a long-term time series. This study introduces a novel LST retrieval algorithm considering AWVC for SDGSAT-1 images and elucidates comprehensive validation and comparative assessment, expanding the application of high-spatial resolution TIR remote sensing data
A preliminary investigation of pore development mechanisms in highly matured solid bitumen: Implications from the Ediacaran Dengying Formation solid bitumen in the central Sichuan Basin, Southwest China
No full textAlthough pores in solid bitumen are crucial for shale reservoirs, their development mechanisms have not been fully understood partly due to the small size of solid bitumen in shales and the difficulty in its discrimination from residual kerogen. However, solid bitumen in conventional reservoirs generally has a larger size and definite origin, and therefore the examination of their pores can provide some insights into the mechanisms of pore formation in shale solid bitumen. In this study, solid bitumen samples from conventional reservoirs of the Ediacaran Dengying Formation in the central Sichuan Basin were collected for petrographic and geochemical analyses to investigate their pore characteristics and formation mechanisms. The results indicate that pores are commonly identified in solid bitumen grains that are derived from the cracking of tar pads and in solid bitumen grains that have experienced gravity-driven component separation during their formation. The development of pores in solid bitumen is controlled by the combined effect of gas expulsion and the viscosity of solid bitumen during its movable stage. The gas expulsion from movable bitumen creates pores, and they can be preserved or healed depending on the component-controlled viscosity of movable bitumen. The enrichment of sulfur- and oxygen-containing compounds and heavy components such as asphaltenes in movable bitumen can enhance its viscosity and thus inhibit the healing of pores, ultimately facilitating pore development in the present overmature solid bitumen grains
Iron isotopic fractionation during seafloor hydrothermal alteration of oceanic upper crust, as recorded in Geotimes lavas of Semail ophiolite, Oman
No full textThe Semail ophiolite in Oman features a crustal stratigraphy akin to a fast-spreading modern oceanic lithosphere. Its Geotimes pillow lavas, the stratigraphically oldest extrusive sequence at the bottom, share geochemical traits with contemporary mid-ocean ridge basalts, offering a unique opportunity to examine iron (Fe) isotopic fractionation during hydrothermal alteration under varied redox conditions. Significant alteration transformed primary minerals, evidenced by the dissolution of clinopyroxene, plagioclase, and ilmenite, alongside the precipitation of chlorite, albite, and magnetite-hematite. The 87Sr/88Sr ratios of 18 basalt subsamples from altered pillow lava range from 0.705110 to 0.705680, indicating extensive seawater interaction. The delta 56Fe values show systematic variations at a centimeter scale (0.037-0.291 parts per thousand), primarily resulting from hydrothermal processes rather than source inheritance. Notably, the pillow lava's core displays higher delta 56Fe values, suggesting the initial dissolution of Fe-bearing minerals under reduced conditions. In contrast, the edges show lower delta 56Fe values akin to mean mid-ocean ridge basalt, indicating that strong oxidation conditions minimally affected these isotopic values. In conclusion, this study reveals the complex variations of the Fe concentrations and Fe isotopic compositions of altered basalt that suffered hydrothermal alteration during the various redox conditions
Monitoring of linear alkyl benzenes (LABs) in riverine and estuarine sediments in Malaysia (vol 44, pg 3687, 2022)
No full textPaired mass-dependent and mass-independent Hg isotope excursions through non-euxinic intervals: Signals of post-depositional Hg isotope fractionation?
No full textMercury (Hg) in sedimentary deposits has become a widely used proxy for reconstructing paleo-volcanic activity. However, a comprehensive understanding of Hg accumulation pattern and the isotope variation during early diagenesis is still lacking. A thorough diagenetic evaluation of sedimentary rocks is crucial prior to the interpretation of geochemical data, as diagenetic changes can lead to considerable differences between the original seawater signatures and the sedimentological records. We observed a Hg isotopic pattern characterized by a negative trend in S202Hg with a concurrent gradual positive shift in p199Hg throughout non-euxinic intervals in multiple marine sedimentary successions. We propose that the synchronous Hg mass dependent fractionation (MDF) and mass independent fractionation (MIF) were driven by diagenetic events. The release of organic-bound Hg and its subsequent diffusion downward to sites where it complexed with pyrite in early diagenetic stages may induce S202Hg shift towards more negative values in the Hg precipitate, and in turn, contribute to the concurrent positive shift of p199Hg observed in these sections
Microplastic mitigation in urban stormwater using green infrastructure: a review
No full textMicroplastic pollution in aquatic environments has emerged as a significant environmental concern, posing risks to ecosystems and human health. Urban stormwater runoff has been identified as a major source of microplastics, with microplastic concentrations reaching up to six times higher than those in wastewater treatment plant effluents. Given the increasing urbanization and inadequate waste management, effective mitigation strategies are urgently needed to prevent the discharge of microplastics into natural water systems. Green infrastructure, designed for sustainable stormwater management, has gained attention as a promising approach to reducing microplastic pollution while providing additional environmental benefits. Here, we review various green infrastructure technologies, including bioretention systems, permeable pavements, stormwater ponds, and constructed wetlands, focusing on their effectiveness in microplastic mitigation. Bioretention systems exhibit removal efficiencies ranging from 80% to over 99%, and are particularly effective for particles sized 20 mu m or above. Constructed wetlands achieve removal rates between 28 and 75%, effectively treating microplastics in the 100-500 mu m range. Permeable pavements demonstrate removal efficiencies of 89-96.6%, especially for particles less than 100 mu m. Retention ponds retain 55-98% of microplastics, with sediment retention reaching up to 85%. We found that the performance of these systems is influenced by soil amendments, vegetation, and adsorption-based mechanisms such as biochar applications, which can enhance removal to over 99% under optimized conditions. Phytoremediation with aquatic plants such as Lemna minor achieves a 76% removal rate, while biofilm-based strategies offer slower but potentially sustainable solutions. This review highlights the necessity of integrating multiple green infrastructure approaches to optimize microplastic removal
Mineralogical fingerprints of crustal silica contamination in the Bayan Obo carbonatite
No full textCarbonatites are carbonate-rich and silica-undersaturated igneous rocks. The presence of various silicates in carbonatites has sparked discussions about the source of silica. In this study, abundant fluorbritholite-(Ce) and humite group minerals are identified in the No. 1 carbonatite dike at the Bayan Obo REE-Nb-Fe deposit. These silicates are relatively rare and poorly understood in carbonatite systems. Mineral textures, in situ EPMA, and LA-ICP-MS analyses have been combined to constrain the mineral genesis in the carbonatite. Fluorbritholite-(Ce), a member of the apatite super-group, occurs as euhedral to subhedral crystals in the dike. They are characterized by remarkably high concentrations of REE2O3 (56.0-63.7 wt%), SiO2 (19.6-21.2 wt%), and F (2.47-3.47 wt%), along with relatively lower P2O5 (0.25-3.69 wt%) and CaO (10.3-14.2 wt%) contents compared to common fluorapatite species. Additionally, their high-Y (961-3435 ppm) and low-Sr/Y (0.59-2.70) values suggest a hydrothermal origin from a fluid rich in SiO2, REE, and F. Humite group minerals, mainly chondrodite and humite, display irregularmineral textures. They also exhibit elevated SiO2 (32.5-34.7 wt%) and F content (3.59-7.32 wt%) with notably low TiO2 content (0.02-0.08 wt%), indicating a hydrothermal origin induced by fenitization in the shallow crust. Our results favor a model of crustal silica contamination for the fenitization fluids enriched in F, LREE, and SiO2. More importantly, the fluid-assisted silica contamination from wall rocks within carbonatites is likely to be a critical trigger of REE deposition in the carbonatite ore-forming systems