Junming Zhou

Elevated levels of hexavalent chromium (Cr(VI)) in soil and water pose severe ecological and health risks, and clay–iron composites are promising natural reactive materials for contaminant immobilization. Yet, the combined effects of Fe loading and organic modification on Cr(VI) retention remain poorly understood. The present study aimed to clarify Cr(VI) adsorption behavior and interfacial mechanisms of montmorillonite–Fe(oxyhydr)oxide composites, and to evaluate the regulating roles of Fe/clay ratio and organic modification. Natural montmorillonite and organo-montmorillonite were composited with ferrihydrite to prepare a series of clay–iron assemblies, and their Cr(VI) adsorption performances were investigated systematically. The Fe/clay ratio dominated the adsorption capacity; the composite with the highest Fe loading exhibited optimal Cr(VI) retention performance due to favorable surface charge and abundant reactive sites. Organic modification introduced extra functional groups but reduced adsorption efficiency by occupying surface sites and altering surface physicochemical properties. The immobilization of Cr(VI) was primarily controlled by electrostatic interaction and inner-sphere complexation at Fe–OH surface sites. This work elucidates key structure–activity relationships of clay–iron composites, provides fundamental insights into Cr(VI) geochemical behavior, and offers a practical basis for developing low-cost clay-based amendments for Cr(VI) contamination remediation.

Geological evidence and paleoclimate models suggest that freeze‐thaw (FT) cycling has played a pivotal role in shaping the Martian surface composition throughout geological time. Here we show the experimental investigation of the sulfuric acid weathering of olivine under simulated FT conditions (193–293 K). Our results reveal that FT cycling enhances both mechanical and chemical weathering processes, with the lifetime of olivine decreasing 23 times compared to those under continuous freezing conditions. Cryogenic weathering promotes olivine hydroxylation and generates secondary phases (e.g., hydrated sulfates and amorphous silica) that collectively retain substantial water in the solid phase. Quantitative comparisons show these cryogenic weathering products retain approximately sevenfold higher water content per unit ion release compared to equivalent materials formed at ambient temperatures. These findings highlight FT cycling as an efficient geological mechanism for simultaneous mineral alteration and water sequestration, advancing mechanistic understanding of Martian hydrological evolution and habitability potential.

As an essential micronutrient, phosphorus plays a key role in oceanic biogeochemistry, with its cycling intimately connected to the global carbon cycle and climate change. Authigenic carbonate fluorapatite (CFA) has been suggested to represent a significant phosphorus sink in the deep ocean, but its formation mechanisms in oceanic low-productivity settings remain poorly constrained. Applying X-ray absorption near edge structure, transmission electron microscopy, and laser ablation inductively coupled plasma mass spectrometer analyses, we report a unique mineral assemblage where CFA crystals coat phillipsite in abyssal sediments of the East Mariana Basin and the Philippine Sea. This finding suggests that phillipsite provides an ideal microenvironment for CFA formation due to its ability to release calcium cations and its strong adsorption capacity for phosphate anions. The feasibility of such a mechanism was confirmed by long-term (10 mo) laboratory experiments. Furthermore, the CFA forming in the sediment of abyssal plains is found to be enriched in rare earth elements (REE). The previously unrecognized mechanism of CFA formation may therefore not only contribute to the cycling of phosphorus in oceanic low-productivity environments but may also represent a significant sink of REE.

Ferromanganese (Fe‐Mn) nodules are widely considered significant economic potential and paleoenvironmentally significant archives. Generally, submicron‐thick layers (SMLs) are basic units of the Fe‐Mn nodules and record valuable information about the environment of Fe‐Mn nodule formation, but their structural, mineralogical, and chemical features are not well resolved. Here, we investigated a typical hydrogenetic Fe‐Mn nodule from the Penrhyn Basin in the South Pacific Ocean, using various microanalytical techniques. The nodule mainly consists of a micronodule‐dominant region around the core, a crust near the surface with Mn‐ and Fe‐rich layers, and stromatolite‐like textures between them. These textures are composed of distinct and indistinct SMLs parallel to their growth front. Although the distinct and indistinct SMLs have different mineral phases, the transmission electron microscopy revealed that these layered structures are actually interstratification of SMLs with different crystal sizes of foliated phyllomanganates. Large crystals contain higher Mn oxidation states than small crystals. Such variations of Mn oxidation state with different crystal sizes along the growth direction imply the short‐term regular fluctuation in the redox condition of the Lower Circumpolar Deep Water.

Diatoms play an important role in the biogeochemical cycling of aluminum (Al) in oceans. This occurs via the uptake of biological Al (Al_bio), which is incorporated into the structure of diatom‐derived biogenic silica (DBSi) and the formation of adsorbed Al (Al_ads) on the DBSi surface of post‐mortem diatoms. Al occurrence influences DBSi dissolution and thus diatom‐driven carbon sequestration. However, the mechanism of Al occurrence in DBSi remains unclear. In this study, Al_bio and Al_ads of DBSi from various diatom fossils in marine diatomaceous sediments were identified and quantified by combined focused ion beam thinning, elemental analysis, and the Al K‐edge X‐ray absorption near edge structure. Results showed the coexistence of Al_bio and Al_ads in all diatomaceous sediments and Al‐bearing DBSi thus constitutes a biological Al pool. Al_bio and Al_ads were mainly fourfold‐ and sixfold‐coordinated, respectively and Al_ads was much more abundant than Al_bio. Moreover, even at low concentrations (with an Al/Si atomic ratio of 0.0031), Al_bio can inhibit DBSi dissolution, effectively decreasing the extent of DBSi dissolution by ∼14%. Al_bio also significantly increased the mechanical strength of DBSi. The average Young's modulus (a measure of the stiffness of a material) of cribrum layers in Al‐incorporated DBSi was ∼1.4 times higher than that of Al‐free DBSi. Our results further demonstrate that diatoms play a dominant role in the biogeochemical cycling of Al in oceans, and the Al of DBSi participates in diatom‐driven Si and C coupled cycles in oceans, influencing the effectiveness of diatom‐driven carbon export by regulating the dissolution and mechanical strength of DBSi.

Ferromanganese (Fe-Mn) crusts are potential marine deposits for many high-tech metals and are exciting proxies for recording the oceanic paleoenvironment. During their growth, phosphatization generally occurs, causing the remobilization and reorganization of the elements and minerals in Fe-Mn crusts. Rare earth elements plus yttrium (REY), well-known critical metals for many new and emerging technologies, as well as valuable geological proxies, are the important critical metals in Fe-Mn crusts. The REY occurrence is closely influenced by the phosphatization processes, which still remain discursive. In this study, the textures, structures, and REY geochemistry of the growth of an Fe-Mn crust sample (MP2D32A) from the Line Islands archipelago were analyzed using multiple microanalysis methods. The analyzed Fe-Mn crust is mainly characterized by the presence of laminated and concentric colloforms. Massive fine particles and some veins of carbonate-rich fluorapatite (CFA) were observed in the old part of MP2D32A, demonstrating that this sample underwent phosphatization. The phosphatized and non-phosphatized layers, as well as the CFA veins, display distinctly different PAAS-normalized REY patterns. Higher REY contents in the phosphatized layer than those in the non-phosphatized layer suggest the positive role of phosphatization in REY enrichment. Moreover, the phosphatized layer contains higher REY contents than the CFA, implying that the REY enrichment in the phosphatized layer is not only influenced by CFA and Fe-Mn (oxyhydr)oxides but also other factors, such as the probable PO₄³⁻ complexation induced by Fe oxyhydroxides. The synergistical sorption of REY(III) and HPO₄²⁻ ions on Fe oxyhydroxides should facilitate REY enrichment during the phosphatization processes. These fundamental results provide novel insights into the influence of phosphatization in REY geochemical behaviors in the Fe-Mn crust.

Clear underwater images can help researchers detect cold seeps, gas hydrates, and biological resources. However, the quality of these images suffers from nonuniform lighting, a limited range of visibility, and unwanted signals. CycleGAN has been broadly studied in regard to underwater image enhancement, but it is difficult to apply the model for the further detection of Haima cold seeps in the South China Sea because the model can be difficult to train if the dataset used is not appropriate. In this article, we devise a new method of building a dataset using MSRCR and choose the best images based on the widely used UIQM scheme to build the dataset. The experimental results show that a good CycleGAN could be trained with the dataset using the proposed method. The model has good potential for applications in detecting the Haima cold seeps and can be applied to other cold seeps, such as the cold seeps in the North Sea. We conclude that the method used for building the dataset can be applied to train CycleGAN when enhancing images from cold seeps.

在蓝宝石衬底上生长了以AlN/GaN超晶格准AlGaN合金作为势垒的HEMT结构材料,并与传统AlGaN合金势垒样品进行了对比.在高Al组分(≥40%)情况下,超晶格势垒样品的表面形貌明显改进,电学性能特别是2DEG面电子浓度也有所改进.对超晶格势垒生长参数进行了初步优化,使得HEMT结构薄层电阻进一步降低,最后获得了251 Ω/□的薄层电阻.