Guangzhou Institute of Geochemistry
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Polyhalogenated carbazoles in the environment: Analysis, origins, occurrence, and toxicity
No full textPolyhalogenated carbazoles are a class of emerging organic compounds characterized by the substitution of one to eight hydrogen atoms in the carbazole structure with halogen atom(s). Polyhalogenated carbazoles originate from natural and anthropogenic sources and are widely distributed in the environment. They are persistent in the environment and present a range of toxic effects, notably dioxin-like activity. This review focused on recent progress in determining their distribution, analytical methodologies, toxicity, origins, and transformation in the environment, highlighting their potential ecological and health risks. It confirmed the critical need for ongoing research regarding their environmental behavior and fate, to ensure a comprehensive understanding of the resulting environmental risks. This review also identified future research needs regarding these compounds
Identification of Hydroxylated Chlorinated Paraffins in Human Serum and Their Potential Metabolic Pathways
No full textShort- and medium-chain chlorinated paraffins (SCCPs and MCCPs) are frequently detected in humans. However, information regarding their metabolites is still very limited. Herein, target analysis and halogenation-guided nontarget and suspect screening were conducted on serum samples using UHPLC-Orbitrap-HRMS. The median concentrations of SCCPs and MCCPs were 7.76 and 4.31 ng/mL, respectively. A series of hydroxylated chlorinated paraffins (OH-CPs) were tentatively identified with an estimated average concentration of 1.80 ng/mL, which was approximately 9.9% of the total SCCPs and MCCPs. A chlorine distribution shift was observed from chlorinated paraffins (CPs) dominated by Cl6 and Cl7 to OH-CPs dominated by Cl5, Cl6, and Cl4. In human liver cytochrome P450 (CYP) enzyme incubation assays, the CPs in commercial mixtures were mainly metabolized into OH-CPs with various carbon lengths and chlorine substituents. The results obtained from human serum and in vitro experiments suggested the oxidative metabolism of SCCPs and MCCPs in humans. The metabolic pathways were then comprehensively explored using a CP monomer (1,1,1,3,10,11-hexachloroundecane) incubated with the same CYP enzymes, demonstrating that CPs can be metabolized through successive oxidative dechlorination and direct hydroxylation, with subsequent oxidation to carboxylic acids. Further studies should focus on the long-term toxicity of OH-CPs
Molybdenum isotope evidence for subduction-modified mantle beneath mid-ocean ridges
No full text"Ghost" arc geochemical signatures persistently occur in mid-oceanic ridge basalts (MORBs), yet their origin remains elusive. Here, we identified arc-like heavy Mo isotopic compositions in basalts from the St. Helena plume-influenced southern Mid-Atlantic Ridge. Their heavy Mo isotopic signature (delta 98/95Mo = -0.21 %o to +0.11 %o), along with relatively low (La/Sm)N, Nb/Zr, Ce/Pb, and Sr-Nd isotope ratios, cannot be explained by interactions of the depleted mantle with recycled crustal or lithospheric mantle materials or the influence of the St. Helena plume on their mantle source. By integrating seismic tomographic images and plate reconstruction models, we interpret these unique geochemical and heavy Mo isotopic signatures to reflect the inputs of fluidmodified mantle produced during the Mesozoic subduction beneath the southwestern Gondwana convergent margin. Our discovery provides crucial evidence for the role of the paleo-subduction-modified mantle in shaping present-day MORB-mantle heterogeneity and sheds light on the formation of ghost-arc signatures in global MORBs
Martian Smectites Formation Regulated by Environmental CO<sub>2</sub> and Si
No full textDespite the anticipated abundant carbonates due to historical atmospheric CO2 levels, Mars presents a geological puzzle with MgFe-smectites dominating the Noachian and early Hesperian terrains, contrasted by sparse carbonate deposits. To address this point, we explored the impact of CO2 on MgFe-smectite formation, emphasizing the role of variable Si concentrations within the simulated Martian environment. Hydrothermal experiments, conducted under a constant CO2 concentration (C0.5) and varying Si concentrations (Si0.5 to Si4), reveal a transformation from pyroaurite to MgFe-smectite via lizardite as an intermediary phase. This transformation underscores the crucial role of Si in this mineral sequence. Notably, experiments demonstrate that the interlayer CO32- in pyroaurite is released into aqueous environments during the mineral conversion, potentially impacting the Martian CO2 budget. These findings could explain isolated carbonate outcrops and the possibility of hydrotalcite-group minerals on Mars today. Further Mars exploration should consider identifying hydrotalcite-group minerals for their implications on the planet's climate and habitability
Mechanistic insights into highly efficient oxygenation of 5-hydroxyme-thylfurfural to 2,5-furandicarboxylic acid over natural sepiolite-supported bimetallic PdAu catalysts
No full textThe oxygenation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is an important reaction for the production of value-added chemicals from biomass. However, developing highly efficient and stable catalysts for this process remains challenging. Sepiolite (Sep)-supported bimetallic PdAu catalysts were prepared for the selective oxygenation of HMF to FDCA. 1Pd1Au4/Sep catalyst exhibited the highest catalytic activity, reaching 100 % HMF conversion and 97 % FDCA yield after 10 min, with outstanding formation rate of FDCA of 2560.72 mmol center dot g- 1 center dot h- 1. This excellent catalytic performance is attributable to rich surface active sites on PdAu/Sep. High specific surface area and special porous structure of Sep can enable its unique adsorption capacities for reactants. Importantly, there are oxygen vacancies (Ov) on surface of Sep, which promotes the activation of O2. What's more, the metal catalytically active sites of PdAu alloy nanoparticles efficiently facilitated the oxygenation of HMF to FDCA. In particular, the kinetic results further reveal that the synergistic effects between Pd and Au accelerated the oxidation of 5-hydroxymethyl-2-furancarboxylic acid (HMFCA). Additionally, the 1Pd1Au4/Sep catalyst had high stability and reusability, without loss of activity after five runs. This study reveals the catalytic mechanisms of the Sep-supported PdAu catalysts for the efficient oxygenation of HMF to FDCA
Microwave Digestion for Re-Os Isotope Measurements in Geological Samples
No full textIn this study, we present the novel use of a microwave digestion system (CEM BLADE) to digest geological materials for Re-Os isotopic analysis. This technique employs quartz digestion vessels that are easy to clean and reusable, avoid the complicated steps of opening and sealing, and enable complete digestion of the samples within 30 min at high temperature (max. 310 degrees C) and pressure (max. 700 psi). The microwave digestion system was used to digest samples of four ultramafic rock reference materials (GBW07101, GBW07102, GBW07291, and WPR-1a), one basalt reference material (BIR-1a), and one black shale reference material (SGR-1b). The Re-Os isotope measurement results for GBW07291, BIR-1a, and SGR-1b were in agreement with previously published values, and we are the first to report Re-Os isotopes for GBW07101, GBW07102, and WPR-1a. Therefore, this new microwave digestion system is a simple, efficient, reliable, and safe sample digestion method for prospective applications in Re-Os isotopic analysis
Organosulfur Compounds: A Non-Negligible Component Affecting the Light Absorption of Brown Carbon During North China Haze Events
No full textThe roles of organosulfur compounds (OSCs), an important component in organic matter, in brown carbon (BrC) aerosol absorption is often overlooked. Here, the molecular composition of OSCs and its associations with methanol-soluble BrC (MS-BrC) absorption during a haze event in North China were revealed using a Fourier transform ion cyclotron resonance mass spectrometry analysis. By combining aggregated boosted tree model and partial least squares regression estimation, our results suggested that OSCs were mainly composed of potential aromatic structures, and the MS-BrC absorption was closely related to OSCs. Specifically, OSCs contribute a notable 26% of the total potential BrC molecular number and an upper limit of 10.4% of total MS-BrC absorption. Furthermore, we found that OSCs were mainly influenced by coal combustion, and the potential desulfurization reactions showed associations with the variations of MS-BrC absorption. Since the residential coal combustion (an important primary source of OSs) was the major energy in North China, our research underscores the potential of aromatic OSCs as tracers for assessing the impact of fossil fuel combustion on BrC and highlights the important atmospheric influences of OSCs (e.g., light absorption and health), which need more works to uncover the origins, fates, and environmental effects of OSCs
Polycyclic Andean-type orogenic evolution of the Dunhuang block in NW China: A result of Paleozoic reconfiguration of oceanic subduction systems
No full textDespite numerous studies of metamorphic and magmatic rocks from the Dunhuang block, its protracted Cambrian to Permian geodynamic evolution as well as its role in the final amalgamation of the Tarim-North- China Craton Collage during the Pangea assembly, remain controversial. In order to understand the evolution of the Dunhuang block in the frame of Paleozoic plate tectonics, we review and synthetize recently published P-T data along with geochronological and geochemical data for its northern, central and southern mountain ranges, which we placed in the context of structural observations. Zircon and monazite U-Pb ages combined with P-T constraints determined for Ordovician to Devonian metamorphic rocks reveal that M1 and M2 metamorphic events define a clockwise P-T evolution and distinctly hot metamorphic gradients. Ordovician to Devonian protracted garnet growth evidenced by low (Yb/Gd)N ratios in metamorphic zircon and monazite, together with low Th/U ratios, negative epsilon Hf(t) and Eu anomalies in magmatic and metamorphic zircon, mark a period of continuous metamorphism accompanied by crustal reworking during thickening of a previously thermally softened crust. Zircon and monazite U-Pb ages suggest that the early Paleozoic D1-M1 and D2-M2 events started ca. 10 m.y. earlier and lasted longer in the northern and central ranges compared to the southern range consisting of significantly older crustal basement components. In all three mountain ranges, the formation of an E-W trending steep cleavage related to D3-M3 event was concomitant with emplacement of numerous late Devonian to Carboniferous diorites and I-type granitoids. The negative epsilon Hf(t) of magmatic zircon and high (Yb/Gd)N ratios in metamorphic zircon and monazite show that a magma-assisted N-S-directed shortening event responsible for further crustal reworking started in the late Devonian and lasted over 60 m.y. The latest Permian M4 metamorphic event, restricted mainly to the southern range, defines anticlockwise P-T paths associated with the emplacement of high-K calc-alkaline granitoids. This event is characterized by the increasing from negative to positive zircon epsilon Hf(t) values, suggesting input of juvenile crustal and mantle-derived material. High metamorphic gradients and the petrogenesis of magmatic arc-related rocks intruding a Precambrian basement suggest that the Dunhuang block developed as a supra-subduction continental hot orogenic system formed above subducting oceanic plates similar to the northern and southern margins of the American Cordillera. Our data show that its evolution was related to two kinematically independent early to middle and late Paleozoic orogenic cycles. In the context of plate tectonic reconstructions, the revised chronology of events points to the kinematic interplay between the continental blocks moving within the Proto-Tethys oceanic domain in association with the south- dipping Panthalassa, Paleo-Asian, and north-dipping Paleo-Tethys oceanic subduction systems
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
Mantle induced hydration and oxidation of intracontinental granite sources in the North China Craton
No full textArc magmatism is typically highly oxidized, due to the influx of oxidizing aqueous fluids released from the subducting plate. The observation that some intracontinental A- and I-type granites also exhibit high oxidation presents a significant challenge in igneous petrology and geodynamics. This is particularly true for regions such as the North China Craton (NCC), situated over 1000 km from the trench. In this study, we measured water content, oxygen fugacity (fO2), and O-Hf isotopes in zircons from the late Mesozoic granites from the NCC. The results reveal positive correlations between water content and f O 2 , and between water content and epsilon Hf(t), indicating the predominant control of primary magma composition, rather than magmatic differentiation, on water content andfO2 of zircon. The Early Cretaceous A-type and I-type granites, which involved greater amount of mantle-derived melts, exhibit more elevated water, Nb, Ta, and f O 2 than the Jurassic granites. This suggests that the hydration and oxidization of intracontinental granitoids of the NCC are strongly influenced by the ingress of mantle-derived oxidized hydrous melts/aqueous fluids to the granitoid source, which were likely released from the Paleo-Pacific plate at a greater depth than the sub-arc mantle. The proposed model involves significant water in intracontinental crustal melting, thereby challenging the paradigm of intraplate A- and I-type granite genesis and shedding light on the crustal and mantle processes during cratonic destruction