Microbes are known to show a great spatiotemporal distribution, and exert extensive and intensive geological agents in both modern days and Earth history. These features make the microbes play important roles on great changes of Earth environments, enabling important and wide applications in geoengineering including the pollutant remediation, decrease of atmospheric CO₂, geohazards prevention, as well as toxicity decrease. This necessitates the cross-disciplinary construction from microbial Earth to microbial geoengineering.It is well known that microbes, the engineer of elemental geochemical cycles, have played the key roles in the geoengineering fields including carbon sink, ecological remediation and the agriculture practice. The carbon pump and the microbial carbon pump, the important mechanisms to transport the atmospheric CO₂ into the sediments or seawater, are documented to mainly regulate by the microbial communities either in the sea or on the land. Microbes are widely involved into, and known as the engineer of, the geochemical cycles of greenhouse gases including CH₄, CO₂ and N₂O. These microbial processes could be exploited in the geoengineering to promote the carbon sink or decrease the carbon release. Microbial transformation of a series of metal ions as well as the degradation on organics has been widely used in the ecological remediation of polluted environments. Microbial release of elements including carbon, nitrogen, phosphor etc., from a variety of minerals is applied in agriculture practice. The artificial microbial mixtures on the basis of natural communities could be used as the nature-based fertilizers in the farming practice. Microbial roles, played on the precipitation and erosion of minerals, could also be applied into rocks and soils engineering, deep Earth engineering and mining industry. The microbial application to these geoengineerings will greatly save the costs, remarkably promote efficiency and noticeably protect the natural environments. Microbial transformation of the expansive clay minerals into no-expansive ones could be applied into the oil recovery by water flooding as well as the rocks and soils geotechnical engineering. Carbonate factory is known to be primarily induced by microbial communities via the precipitation of calcium carbonate from the fluids which could be introduced into the building of artificial islands in the sea, the filling and repairing of rock cracks, cementation of coarse grains in a variety of geoengineering. Microbial erosion of minerals could be exploited into the mining industry via the release of metals of economic significance from ores. The presence of the so-called deep biosphere, featured by the dominance of extreme environment microbes, will exert positive and negative effects on the underground storage of dangerous materials including the nuclear wastes, CO₂ and hydrogen gas. The investigations on the microbial roles on these materials as well as the storage containers are of in particular importance.Whilst most microbial geoengineering has been conducted to prevent and control the geohazards that have come into being in natural environments, microbes could further provide the early warning of some geohazards including the biotic or ecological crisis, climatic and environmental disasters, as well as landslides due to their sensitive response to minor environmental changes. To construct the early warning geoengineering via the on-site filed observatory network is of importance so that we could take some measures to prevent the occurrence of the geohazards, or make the positive use of the microbial roles but suppress the negative roles.

The sequestration of Soil Organic Carbon (SOC) constitutes a pivotal component of global climate change mitigation strategies. While the “microbial carbon pump” and biotic anabolism have traditionally dominated conceptual paradigms of humification, emerging evidence suggests that this biocentric view may underestimate the contribution of abiotic geochemical pathways. This review systematically delineates the role of the non-enzymatic Maillard reaction as a critical geochemical bridge linking mineral weathering processes to long-term SOC persistence.We propose a mechanistic framework of “mineral interfacial catalysis-melanoidin formation-organo-mineral complexation”to elucidate this abiotic stabilization trajectory. Specifically, soil minerals, particularly Fe/Mn oxides and phyllosilicates, act as natural catalysts by providing Lewis acid sites that lower the apparent activation energy for the condensation and polymerization of reducing sugars and amino compounds. This process transforms labile precursors into chemically recalcitrant, aromatic-rich polymers commonly referred to as melanoidin-like substances. These reactions are thermodynamically and kinetically favored under conditions of elevated temperature, alkaline to neutral pH, and intermediate to fluctuating moisture regimes, potentially representing a dominant stabilization pathway in subsurface horizons or anaerobic environments where microbial activity is energetically or kinetically constrained.The resulting melanoidin-type products exhibit a pronounced dual-protection capacity, beyond their inherent structural heterogeneity and low biological accessibility, they form robust associations with mineral matrices through physical confinement, ligand exchange, and polyvalent cation bridging. By acting as a non-enzymatic hub that integrates plant-derived carbon inputs and microbial metabolites into persistent organo-mineral complexes, the Maillard reaction challenges conventional theories of humic substance formation and provides a mechanistic framework for an underexplored abiotic pathway of carbon stabilization.Despite growing recognition of its potential importance, current understanding remains constrained by a reliance on simplified laboratory proxies, a scarcity of in situ field evidence, and the absence of diagnostic molecular biomarkers capable of distinguishing abiotic melanoidins from microbially derived necromass. Consequently, the quantitative contribution of this abiotic module to long-term SOC persistence remains poorly constrained. Future research should prioritize resolving environmental controls, multi-factor interactions, and identifying the molecular fingerprints of soil Maillard products in natural ecosystems. Incorporating mineral-mediated, non-enzymatic stabilization processes into terrestrial carbon cycle models will be essential for accurately capturing the coupled “climate change-rock weathering-carbon stability”continuum and for informing strategies that integrate geological and ecological carbon sequestration.

The farming-pastoral zone in Naiman Banner is located in the hinterland of Horqin Sandy Land. The research on the formation mechanism and background values of groundwater hydrochemistry supports the allocation of water resources and the green development of agriculture and animal husbandry. Based on hydrogeological survey and hydrogeochemical analysis, combined with self-organizing map neural network (SOM) and K-means clustering hybrid algorithm, this study revealed the characteristics of groundwater chemical composition, main controlling factors, and environmental background values. Results indicated significant spatial heterogeneity in groundwater chemistry, with HCO₃-Ca·Mg as the predominant hydrochemical type and weakly alkaline characteristics. Groundwater chemical evolution is primarily driven by dissolution-precipitation of carbonate minerals and weathering of silicate minerals, and controlled by alternating positive cation adsorption. The apparent background values of Total Fe (TFe), F^-, TDS and NO₃-N, key indicators affecting the quality of groundwater in Naiman Banner, were 0.42~0.56 mg/L, 0.34~0.38 mg/L, 181~188 mg/L and 0.22~1.58 mg/L, respectively, which were estimated by using a coupled approach of hydrogeochemical graphic method, Grubbs test and SOM. The high background of TFe may be related to siderite dissolution, while the F^- enrichment is controlled by fluorite dissolution and alternating positive cation adsorption. This research elucidates the groundwater background values and hydrochemical formation mechanisms in the farming-pastoral zone of Naiman Banner, providing scientific support for the optimization management of regional water resources, pollution prevention, and ecological conservation.

The Naiman Sag is located in the southwestern part of the Songliao Basin. It remains underexplored, and the conditions for hydrocarbon accumulation and the main controlling factors are not yet well understood. This study based on a comprehensive review of previous studies and integrates data from drilling, seismic profiles, reservoir lithology and petrophysics. It analyzes the petroleum geological characteristics, controlling factors for hydrocarbon accumulation, and resource potential of the Naiman Sag. The results indicate the primary hydrocarbon source rocks in the region are the Shahai, lower Jiufotang, and Yixian formations. These are mainly concentrated in the northern part of the sag and are generally at a low-to-mature stage (R_O<1.0%). Among them, the lower Jiufotang Formation, developed in semi-deep lake to deep lake facies, contains high-quality source rocks with high organic matter abundance (average TOC of 2.79%) and predominantly of Type I and Type II₁ kerogen. These source rocks are the primary contributors to hydrocarbons in the region. Biomarker characteristics indicate that the source rocks formed in a high-salinity, strongly reducing lacustrine environment, with mixed contributions from lower aquatic organisms and higher terrestrial plants. The hydrocarbons in the region are primarily heavy oil and wet gas, with heavy oils not undergoing significant biodegradation and mainly controlled by low maturity. The natural gas is characterized as sapropelic kerogen-derived gas in the low-to-mature stage, directly resulting from kerogen cracking. Hydrocarbon accumulation is primarily controlled by favorable source-reservoir configurations, dominant depositional facies, and advantageous lithology, demonstrating a trinity of “facies-lithology-structure” coupling. Additionally, deep fluid activities may play an important role in the accumulation process by not only promoting secondary hydrocarbon generation but also contributing to the enrichment of associated noble gases such as hydrogen and helium. Overall, the central and deeper “sweet-spot” zones of the sag, with abundant hydrocarbon supply, proximal traps, and active fluid movement, show significant exploration potential. Future studies should focus on the unconventional accumulation mechanisms under multi-factor coupling. This will deepen the understanding of the petroleum system in the Naiman Sag.

Silicon, the second most abundant element in Earth’s crust, is intricately linked to the global carbon cycle through its biogeochemical processes, playing a pivotal role in regulating atmospheric CO₂ concentrations, marine primary productivity, and coastal eutrophication. Biogenic Silica (BSi), a silicon-containing compound produced by biological metabolism, serves as the primary pathway for silicon removal from the ocean via sedimentary burial. However, the lack of unified standards for BSi determination in China's offshore sediments has impeded data comparability across studies. An extensive evaluation was conducted to assess the effects of key parameters, including pretreatment methods, extractant concentration, temperature, and duration, on the measurement results of BSi. The findings demonstrate that the optimal analytical approach for determining BSi in China’s coastal marine sediments involves extraction with 0.5 mol/L Na₂CO₃ solution at 85 °C for 8 hours, without any preliminary chemical pretreatment. This research compiles BSi content and distribution data from sediments in the Bohai, Yellow, East China, and South China Seas. It calibrates data generated under different pretreatment and extraction conditions against the optimal methodology, and analyzes spatial distribution characteristics and influencing factors. Results indicate that BSi content in China’s offshore sediments ranges from 0.05% to 3.82%, with an increasing trend from north to south, alongside distinct planar and vertical distribution patterns in different sea regions. Key influencing factors include water column primary productivity (particularly diatom productivity), sediment dissolution rates (regulated by temperature, pH, specific surface area, and aluminum content), and human activities (such as nutrient input and hydrodynamic changes). This study provides an improved data foundation and methodological framework for subsequent high-precision marine silicon cycle research, carbon sink assessment, and predictive modeling of coastal ecological evolution in China’s offshore areas, while simultaneously highlighting the urgent necessity for establishing national BSi standard reference materials and standardized analytical protocols.

Differential filling characteristics of pores and fractures in karst reservoirs serve as critical indicators for the reconstruction of paleokarst hydrogeological systems. The mobility and retention degree of karst water control the dissolution and filling processes in carbonate reservoirs, ultimately governing reservoir quality. Based on the tectonic and sedimentary background of the Ordovician Majiagou Formation in the Daniudi gas field, Ordos Basin, this study integrated core observations, cast thin-section analyses, geochemical data (including elemental and isotopic compositions), and petrographic techniques to systematically investigate the vertical zonation of karst features and pore-fracture filling patterns. The implications of differential filling for tracing paleo-karst water flow pathways are discussed. Key findings are summarized as follows: First, the Majiagou Formation is divided into two vertical karst zones: a weathering crust karst zone (sub-members Ma 5_1~5) and a stratabound karst zone (sub-member Ma 5₆). Weathering crust karst zones are characterized by vertical seepage fractures and horizontal subsurface flow dissolution pores, which are strongly influenced by paleotopography. In contrast, the stratabound karst zone is dominated by downward-infiltrating karst water, forming dissolution caves and breccias. Second, the coupling between dissolution pores and fractures in the karst reservoir is evident. Four distinct filling patterns were identified: \mathrm{①} both pores and fractures were filled; \mathrm{②} pores were unfilled but fractures were filled; \mathrm{③} pores were filled but fractures were unfilled; and \mathrm{④} both pores and fractures were unfilled. These patterns reflect the differences in karst water saturation and mineral precipitation processes. Filling heterogeneity indicates variations in fluid chemistry and hydrodynamic conditions during diagenesis, and petrographic analysis revealed that fault systems act as primary conduits for karst water flow. Geochemical parameters further constrain fluid behavior; the weathering crust karst zone shows high Fe/Mn ratios (averaging 51.30) and significantly negative carbon-oxygen isotopic values, suggesting intense dissolution under oxidizing conditions. In the stratabound karst zone, Fe/Mn ratios vary widely (20.78~92.47), and strontium isotopic ratios (⁸⁷Sr/⁸⁶Sr=0.711034) exceed those of contemporaneous seawater, indicating prolonged water retention and reduced dissolution intensity during lateral flow. Fourth, the distribution of pore-fracture filling correlates with paleo-karst geomorphology. In the transition areas between karst highlands and slopes (e.g., Well S401), limited vertical seepage leads to the complete filling of pores and fractures, degrading reservoir effectiveness. In contrast, transition zones between slopes and grooves (e.g., Well D126) maintained semi-open fluid systems with minimal mineral precipitation, preserving effective storage space. This demonstrates that the differential filling features of pores and fractures, when combined with paleo-karst geomorphology, fault distribution, and geochemical proxies, can effectively reconstruct karst water flow pathways and retention states. These results provide a scientific basis for evaluating karst reservoir heterogeneity and guiding hydrocarbon exploration in similar geological settings.

Nitrogen uptake by phytoplankton and nitrification mediated by nitrifying microorganisms in the upper ocean are key processes affecting marine productivity and carbon sequestration. Understanding how these two critical nitrogen cycle processes respond to the dual stressors of ocean acidification and warming represents a pressing research frontier in marine biogeochemical cycles and global change. Elucidating this issue will provide a theoretical foundation for accurately assessing future changes in ocean productivity and the efficiency of the biological pump. However, most existing studies rely on laboratory-based pure culture experiments, which may fail to adequately reflect the complex interactions between phytoplankton and nitrifying microorganisms in natural marine ecosystems and their responses to changes in environmental factors. This study systematically summarizes the impacts and mechanisms of ocean acidification and warming on nitrogen uptake and nitrification. In addition, more attention needs to be paid to other factors, such as strengthened ocean stratification and decreased dissolved oxygen contents, induced by ocean acidification and warming, which could indirectly affect nitrogen uptake and nitrification. Existing problems such as insufficient in-situ monitoring of ecosystems, limited synergistic studies on multiple processes and stresses, and inadequate understanding of long-term adaptation processes, are highlighted. Finally, three key areas are proposed for future research: \mathrm{①} synchronous coupling analysis of nitrogen uptake and nitrification processes, and clarifying the interactive effects of acidification and warming, \mathrm{②} exploring the vertical differentiation response mechanisms of the above processes in the upper ocean, particularly in oligotrophic oceans, where critical knowledge gaps exist, and \mathrm{③} elucidating the long-term adaptation processes and nonlinear responses of phytoplankton and nitrifying microorganisms. A three-in-one research framework is constructed—encompassing the spatial dimension, temporal scale, and the experimental system—to provide a scientific basis for evaluating the evolution of key nitrogen processes and marine productivity under global change.

The formation of mineral deposits is generally accompanied by the superposition or transformation of different geological events, and involving varying sources (shallow and deep) of ore-forming materials. The geological significance of these ore-forming events and their corresponding geochemical fields have various implications for mineral exploration. Multistage superimposed mineralization typically manifests as a complex superimposed field comprising multiple sources in geochemical contexts. Effectively decomposing the ‘multi-source complex superimposed field’ and establishing the coupling between the geochemical field and its corresponding ore-forming geological events can greatly enhance the accuracy of geochemical evaluation in exploration. Based on this concept, this study utilized the C-A multifractal model to analyze hydrocarbon-mercury comprehensive gas measurement data from soil medium in the Woxi gold mining area of Hunan. By extensively exploring the correlations of data at different scales and combining the mineralization patterns of gold deposits in the study area, the study further investigated the mineralization mechanisms of various types of “superimposed fields” and conducted an assessment of deep-seated mineral exploration potential. The results indicate that: ① The study area exhibits two characteristic multifractal patterns of soil geochemical anomalies, formed by fitting either two (termed Model Ⅰ) or three (termed Model II) straight-line segments, respectively. This multifractal model suggests the possibility of two periods of overlapping mineralization in the study area. ② Examination of correlations between mineralization elements (Au), organic hydrocarbons (CH₄, C₂H₆, etc.), and other chemical elements in the different scaling regions of Models I and II revealed that both showed two distinct superimposed geochemical anomalies, formed by different mineralization processes. The “syngenetic superimposed anomaly” represents regional mineralization, in which shallow-source fluids (metamorphic fluids, atmospheric precipitation, etc.) only bring mineralized materials from ore-forming strata to participate in Au mineralization. This type of anomaly, limited by the source of mineralization materials, may form gold points or small gold deposits, with correspondingly low potential for discovering large deposits. The “deep-source superimposed anomaly”, on the other hand, is influenced by plate collisions, dispersion, or the upwelling of mantle heat columns and the disturbance of deep large fractures. These processed facilitate the migration of mantle fluids from depth, and their evolution through multi-level fluid mixing, which brings a substantial amount of deep ore-forming materials to further superimpose mineralization on the “syngenetic superimposed anomaly”, thus presenting considerable potential for deep mineral discovery. The results align closely with extensive engineering validation, indicating that the decomposition of complex geochemically superimposed fields based on the C-A multifractal model has achieved better application results, providing new research ideas and methods for evaluating the potential of deep mineral exploration in geochemistry.

This paper systematically analyzes the application, acceptance, evaluation, and funding of the projects managed by the Geochemistry Discipline (Application Code: D03) in the Department of Earth Sciences, National Natural Science Foundation of China in 2025, and reviews the project completion in 2024. Compared with 2024, the number of applications for the Fund for the Less Developed Regions increased in 2025, while the General Program and Young Scientists Fund (C) showed a slight decrease. For two consecutive years, the number of applications for the Young Scientists Fund (C) has been significantly lower than that of the General Program. In the past five years, the total number of host institutions applying for projects has kept increasing continuously, and Earth’s surface geochemistry (D0310) has become a new growth point of the discipline. In 2025, four projects in the Geochemistry discipline were not accepted due to failure to provide required supporting materials. The review submission rates of the General Program, Young Scientists Fund (C), and Fund for the Less Developed Regions were 154.7%, 154.7%, and 141.7%, respectively. The funding rates were 17.9%, 18.4%, and 11.1%, respectively. The average funding amounts were 531 000 yuan per project, 300 000 yuan per project, and 309 000 yuan per project, respectively. The completion outcomes of the General Program, Young Scientists Fund (C), and Fund for the Less Developed Regions in 2024, as well as the Young Scientists Fund (B) projects approved in 2021, indicate that the overall quality of funding achievements and first-labeled achievements needs further improvement. In recent years, the geochemistry discipline has remained characterized by a relatively small number of applications and slow growth. In the future, on the basis of maintaining the advantageous directions of the discipline, efforts should be made to strengthen the in-depth integration of basic research with goal orientation and national needs, and to promote interdisciplinary, cross-disciplinary, and transdisciplinary research, so as to expand both the depth and breadth of geochemistry research.

As a key active component of the black carbon continuum, Dissolved Black Carbon (DBC) exhibits markedly distinct molecular structural characteristics and environmental fate attributes compared with particulate black carbon. Originating from the incomplete combustion of biomass and fossil fuels, DBC is highly reactive and mobile, with colloidal particles facilitating its transport approximately three times faster than that of particulate black carbon. This enables extensive participation in biogeochemical cycles through interfacial complexation, redox regulation, and biological metabolism. These processes are integral to the Earth’s material cycles and energy transformations. This study systematically analyzed the structural heterogeneity of DBC derived from various sources, emphasizing its environmental behavior, such as aggregation influenced by cation valency and salinity, adsorption onto mineral surfaces, redox-mediated transformation of heavy metals, and photochemical reactions across soil-water-atmosphere interfaces. We further elucidated how DBC profoundly influences ecosystem structure and function by regulating elemental cycles (e.g., enhancing carbon sequestration and promoting nitrate reduction), mediating iron mineral transformation, facilitating contaminant transport and transformation, and exerting dual effects on microbial and plant metabolism. Its complex role is evident as it can serve as a nutrient source yet also induce oxidative stress or enhance heavy metal uptake in crops. However, current understanding is constrained by technical limitations in resolving molecular fingerprint isomers, quantifying interfacial reaction kinetics in situ, and dynamically characterizing micro interfacial processes. Overcoming these bottlenecks is essential to unravel the evolutionary mechanisms, interface dynamics, and ecological risks of DBC-pollutant/element coupling systems. This review synthesizes the current knowledge and aims to provide a theoretical foundation for accurately assessing the ecological and environmental impacts of black carbon cycling in the context of global change. This further highlights the need for advanced predictive models and in-situ techniques to support ecological conservation, pollution control, and sustainable environmental management.

In the intricate domain of marine geochemistry, barium (Ba) and its isotopes emerge as pivotal elements. Their remarkably high preservation rate in marine sediments allows them to withstand post-depositional alterations, making them ideal proxies for long-term geological records. The stable isotope fractionation behavior of barium serves as a powerful tool for reconstructing paleoproductivity with high precision. In this study, we meticulously compiled high-precision isotope analysis data from various sources, including a comprehensive review of existing literature and in-house experimental results. We then conducted an in-depth investigation into the sources and sinks of marine barium. Our findings demonstrate that terrigenous, hydrothermal, and biological inputs are not isolated contributors, but instead interact synergistically to drive the cycling of barium in the ocean. Regarding Ba isotope fractionation, within the mineral-fluid-melt system, we found that the dynamic interplay between equilibrium and kinetic fractionation mechanisms is of critical importance. Equilibrium fractionation, governed by quantum mechanical differences in bond vibrations, and kinetic fractionation, associated with non-equilibrium processes such as diffusion, jointly shape the isotopic composition of marine barium. Observed regional variations in isotope fractionation further suggest that multiple factors, including temperature, pressure, and the presence of various chemical species, jointly influence marine Ba isotope behavior. This spatial heterogeneity provides a valuable framework for tracing the evolution of the paleo-oceanic environment and reconstructing historical changes in oceanic conditions. Looking ahead, the integration of in-situ micro-area analytical techniques is not merely desirable but essential. These advanced methods will enable detailed investigations at the microscale, enhancing our understanding of the interactions among biological, mineral, and fluid components in marine systems. Ultimately, such insights will improve the accuracy of paleo-oceanic reconstructions and contribute to a more comprehensive understanding of Earth’s past oceanic ecosystems.

The relative abundance of tricyclic terpanes is an important indicator of organic matter origin, depositional environment, and thermal evolution. While traditional coal-measure source rocks typically exhibit low tricyclic terpane contents, anomalously high abundances (relative to hopanes) have been observed in source rocks from the Ordos and Tarim Basins. Therefore, detailed investigations into their distribution patterns, compositional characteristics, and formation mechanisms are of substantial significance. This study employed conventional geochemical analysis methods and gas chromatography-mass spectrometry (GC-MS) to systematically characterize the molecular geochemical features of 30 coal-measure source rock samples from the study area. The results show that tricyclic terpanes in coal-measure source rocks exhibit two distinct abundance patterns: low abundance (∑TT/C₃₀H<2) and high abundance (∑TT/C₃₀H>2). The low-abundance tricyclic terpane samples exhibit a decreasing C_19-21TT distribution, formed in freshwater, oxidizing environments, with hydrocarbon-generating parent material primarily derived from higher plants under low thermal maturity conditions. The high-abundance tricyclic terpane samples showed distribution patterns with C₂₃TT or C₂₁TT as the dominant peak, formed in saline, sulfur-rich depositional environments. The hydrocarbon-generating parent material was mainly derived from bacteria and lower aquatic organisms, reaching mature to highly mature thermal evolution stages. Correlation analysis of maturity, depositional environment, and parent material input parameters with ∑TT/C₃₀H values revealed that depositional environment and source material characteristics had a stronger correlation with tricyclic terpane abundance than thermal maturity. The findings suggest that brackish, high-sulfur coal-forming environments and increased contributions of secondary products from microbial transformation of higher plants are the primary controlling factors for high tricyclic terpane abundance in coal-measure source rock extracts, whereas thermal maturity is a secondary factor. The molecular compositions and formation mechanisms of high-abundance tricyclic terpanes provide crucial geochemical evidence for identifying coal-forming environments, characterizing hydrocarbon-generating organic matter, and evaluating thermal maturity, thereby offering theoretical and practical guidance for coal-measure hydrocarbon exploration.

Hydrocarbon compounds in herbaceous plants play an important role in assessing ecological and environmental changes in cold, arid, high altitude regions. The alkanes and olefins in Festuca brachyphylla Schult. & Schult. f. From high-altitude, cold and arid region of the Tianshan Mountain was analyzed using organic geochemical methods to determine their geochemical characteristics and environmental responses. The results showed that, for alkanes, the carbon numbers ranged from C₁₆ to C₂₉. The Average carbon Chain Length (ACL_Alk) ranged from 17.91 to 24.49, with C₁₆, C₁₈ and C₂₉ as the main peak carbon numbers. For olefins, the carbon number ranged from C₁₆ to C₃₁, the Average carbon Chain Length (ACL_Ole) ranged from 22.19 to 26.23 and the main peak carbon numbers were C₁₆ and C₂₀. Overall, alkanes and olefins in the herbaceous plants showed relatively higher contents of low carbon number components (≤23 for alkanes and <27 for olefins), with an even-to-odd predominance among lower carbon numbers and a significant odd-to-even predominance at higher carbon numbers. Comparative analysis with hot, humid, and drought-prone environments revealed that Festuca brachyphylla Schult. & Schult. f. from the high-altitude, cold, and arid Tianshan Mountains exhibits unique geochemical characteristics, including higher contents of low-carbon alkanes and olefins, lower Average carbon Chain Length (ACL) values, and notable differences in the Odd-Even Predominance (OEP) index between lower- and higher-carbon hydrocarbons. The Average carbon Chain Length of the Olefin (ACL_Ole) in herbaceous plants with sufficient water supply was relatively long. A strong positive correlation was observed between the Average carbon Chain Lengths of alkanes (ACL_Alk) and Olefins (ACL_Ole) in Festuca brachyphylla Schult. & Schult. f. These results provide insights into the ecological adaptation mechanisms of herbaceous plants in high-altitude, cold, and arid environments and help evaluate the ecological impacts of environmental changes.

As one of the most significant cryospheric landforms that respond to climate warming in permafrost regions, thermokarst lakes profoundly influence ecological changes, regional hydrological cycles, and biogeochemical processes while compromising the stability of permafrost engineering. This study reviews recent advances in the formation and evolution of thermokarst lakes, their hydrological cycles, heat transfer, ecological and environmental effects, and engineering impacts across northern hemisphere permafrost regions. Research indicates that in the discontinuous permafrost zones of the Arctic, lake and pond areas show a predominantly decreasing trend, whereas, in continuous permafrost zones, both expansion and shrinkage are observed. On the Qinghai-Tibet Plateau, climate warming and increased precipitation have led to the rapid formation and expansion of thermokarst lakes. The evolution of these lakes, coupled with hydrological cycling and thermal effects, alters the physicochemical properties of the surrounding soils, influences hydrothermal dynamics in alpine ecosystems, and reduces the stability of adjacent permafrost engineering structures. Furthermore, the development of thermokarst lakes accelerates the decomposition of permafrost carbon stocks, releasing greenhouse gases such as CO₂, CH₄, and N₂O, which further feedback into the climate system. Currently, coupled water-heat-carbon cycling processes and their environmental implications represent a key research focus in permafrost science. Future studies should comprehensively consider the interactive effects of climate change and human activities and, based on coupled water-heat-carbon cycling processes, develop high-precision land surface process models to investigate ecological succession, water resource dynamics, and carbon cycling in permafrost regions under changing environmental conditions, thereby advancing cryospheric science.

Carbon and oxygen isotopes of benthic foraminifera are widely used for paleoenvironmental reconstructions. However, large benthic foraminifera (LBF) shells, as the predominant sediment type in coral reef areas, exhibit isotope values influenced by many factors, especially the “vital effect”, which limits their application. Therefore, this study systematically categorizes the main factors contributing to deviations in the carbon and oxygen isotope values of LBF, including symbiotic algae, the calcification process, individual development, and seasonal variation. Furthermore, the mechanisms underlying these factors are thoroughly examined. Additionally, the potential applications of LBF carbon and oxygen isotope indices are analyzed. Despite the influence of vital effects, these indicators can still serve as powerful tools for paleoenvironmental reconstruction in coral reef areas by selecting suitable species, employing micro-area analysis, and integrating these indices with other paleoenvironmental proxies.

This paper systematically analyzes the application, acceptance, evaluation, and funding of the projects managed by the Geochemistry Discipline (Application Code: D03) of the Earth Sciences Department of National Natural Science Foundation of China in 2024, and analyzes the project completion and precautions in 2023. In 2024, the total number of applications for geochemical projects increased by 21% compared to 2023, among which the number of general projects increased by 45.5%. In the past four years, the total number of supporting units applying for projects has kept increasing continuously, and Earth’s surface geochemistry (D0310) has become a new growth point of the discipline. The general projects and youth projects are mainly based on “free-exploration basic research”, while the key projects in the field of “resource and energy formation theory and supply potential” are mainly based on “goal-oriented basic research”. In recent years, geochemistry discipline has remained characterized by a relatively small number of applications and slow growth. In the future, in-depth research and discussions should be conducted on how to maintain the inherent strengths in isotopic theories and technologies within the geochemistry discipline, guide the deep integration of basic research with target orientation and national needs, and promote the deep intersection and integration of geochemistry discipline with other disciplines. While expanding the direction of the field, efforts should be made to create high-quality and advantageous disciplinary directions in geochemistry.

Degassing of CO₂ from the solid Earth significantly influences the surface carbon cycle. In addition to volcanic activity, various types of active faults in nonvolcanic regions serve as crucial pathways for the migration and release of deep carbon to the surface. The continental collision zone, exemplified by the Tibetan Plateau and its surroundings, is one of the most tectonically active regions in the world. However, general research on deep carbon origins and outgassing rates of active faults remains limited. Southwestern Yunnan lies on the southeastern margin of the Tibetan Plateau and is characterized by a network of left- and right-lateral strike-slip faults. The area experiences frequent seismic events and abundant hydrothermal activity. The hydrochemical, hydrogen, and oxygen isotope compositions of 12 hot springs in the Lancang fault zone of southwestern Yunnan indicate that the hot spring water exhibits an HCO₃-Na type composition, primarily sourced from atmospheric precipitation, and shows no significant contamination from magmatic or metamorphic fluids. During subsurface fluid circulation, it undergoes mineral dissolution and ion exchange reactions with the surrounding rock minerals, which are influenced by the dissolution of minerals, such as silicates, carbonates, and evaporites. A mass balance model based on the concentrations of Dissolved Inorganic Carbon (DIC) and its carbon isotopic compositions shows that the contribution of deep carbon to DIC is approximately 46.9%~78.0%, which, together with the flow rates of thermal spring water, yield an estimated deep carbon outflux of approximately 440 t/a for the Lancang fault zone. The total deep carbon outflux of the thermal springs in southwestern Yunnan was estimated to be approximately 3×10⁴ t/a. The higher deep carbon fluxes and contributions observed in the thermal springs near the Lancang fault zone demonstrate the predominant influence of strike-slip faults on the origin and release of deeply sourced carbon-bearing fluids. Considering the tectonic context of the strike-slip movement, we suggest that the deformation and fracturing of deep rocks within the Lancang fault zone facilitated the migration of a significant volume of metamorphic CO₂ and a minor portion of mantle-derived carbon to the shallow geothermal system. This process might have resulted in the formation of a reservoir enriched in CO₂ fluids that could transfer carbon to the surface. These findings provide observational evidence that enhances our understanding of the mechanisms of deep carbon release in the active fault zones of southwestern Yunnan.

The bioclastic limestone of the Mi4 section of the Mishrif Formation has undergone multiple phases of dissolution and cementation in oilfield A in Iraq. To investigate the impact of multiphase dissolution and cementation on the physical properties of bioclastic limestone and analyze the primary controlling factors during the dissolution and cementation of the early stages of the process. Based on qualitative and semi-quantitative analysis methods, including core observation, thin-section identification, image analysis, petrographic characteristics, carbon and oxygen isotopes, cathodoluminescence, and fluid inclusion homogenization temperature data, the dissolution and cementation periods of Mi4 bioclastic limestone were divided. These results indicate that the bioclastic limestone in the Mi4 section underwent diagenetic transformation during the eogenetic-early and mesodiagenetic stages, resulting in five phases of dissolution cementation. Eogenetic fabric selective dissolution, eogenetic-early diagenetic karstification, mesogenetic dissolution, eogenetic-early diagenetic cementation, and eogenetic-early diagenesis superimposed with mesodiagenetic cementation. The physical properties significantly evolve during eogenetic-early diagenetic due to solution-cementation processes with permeability ranging from 6.96~27.73×10^-3 μm². Dissolution was found to be controlled by bioclastic types during both the eogenetic-early stages, with algae-rich pelitic limestone exhibiting the highest degree, followed by the Mi4-3 and Mi4-4 layers with low algae-debris content. Furthermore, it was observed that the paleo-geomorphology and distance between reservoirs influenced the cementation process during the eogenetic-early stage, with the Mi4-1 layer showing the highest degree under the quaternary sequence interface.

Seafloor methane seepage is an important source of methane affecting the global carbon cycle and extreme environmental biogeochemical cycles. Therefore, identifying modern and ancient seafloor methane seepage is of great scientific significance. During methane leakage, Sulfate-Driven Anaerobic Oxidation of Methane (SD-AOM) commonly occurs, changing the geochemical characteristics of pore water and forming of authigenic minerals. Authigenic pyrite is a typical authigenic mineral in SD-AOM and can be used as a good indicator for recording methane leakage. This study summarizes the geochemical and morphological characteristics of SD-AOM-derived authigenic pyrite and evaluates its potential for tracing and reconstructing seabed (paleo) methane leakage. The results show that the sulfur and Fe isotopes, as well as in situ trace elements and isotopes of authigenic pyrite, can effectively identify the SD-AOM process. In addition, significant differences are observed in the morphology and content of authigenic pyrite in sediments in these environments compared with normal marine sediments, highlighting the great potential of authigenic pyrite for tracing and reconstructing seabed (paleo-) methane leakage events.

Since the inception of the (U-Th)/He thermochronometer at the turn of the last century, it has assumed an increasingly pivotal role in geology and related disciplines, notably in the dating of apatite and zircon. However, the occurrence of apatite and zircon is relatively restricted in nature, significantly constraining the advancement and application of (U-Th)/He dating. Through ongoing, comprehensive investigations into He diffusion kinetics and advancements in analytical technology, alongside apatite and zircon, other minerals (U-Th)/He thermochronologies have also made significant strides, progressively refining and broadening their applications, thereby opening new avenues for the (U-Th)/He thermochronometer. Moreover, different minerals record distinct geological information; hence, employing (U-Th)/He dating across multiple minerals enhances our comprehension of geological processes. This paper provides a concise overview of the progress in (U-Th)/He dating of hematite, goethite, magnetite, carbonate minerals, conodont, fluorite, perovskite, spinel, rutile, and garnet, with a focus on the advanced research in hematite, goethite, magnetite, carbonate minerals, and conodont (U-Th)/He dating, which are relatively mature. Presently, these novel methodologies have found applications in diverse fields such as ore deposits, sedimentology, tectonic geology, geodynamics, and environmental science, particularly in determining mineralization age, reconstructing paleoenvironments and paleoclimates, elucidating processes of oceanic crust alteration, subduction, and exhumation, understanding the functioning of hydrothermal systems, investigating fault deformation, and conducting paleoseismic research, wherein they are poised to play a pivotal role. However, several challenges persist, including multiple diffusion domains, the impact of radiation damage and chemical composition on helium diffusion, loss of parent isotopes during heating and degassing, and open behavior within the (U-Th)/He system, often resulting in dispersed thermochronological (U-Th)/He dates. Thus, further investigations into He diffusion behavior in these minerals, enhancements in experimental methodologies, and improvements in instrument accuracy are imperative to ensure the precision of (U-Th)/He data, thereby furnishing a more dependable framework for understanding geological processes.

The Yangtze River is the largest river system in Asia, and its formation and evolution are of great significance for understanding the topography, climate change, biological evolution, and material cycles of East Asia. The Three Gorges lie in the central Yangtze Block, and its formation connects the drainage in the Sichuan Basin and the Jianghan Basin; therefore, it is regarded as one of the most critical events in the history of the Yangtze River. However, the debate over how and when the Three Gorges were formed has been ongoing for over a century. This study reviews the century-long debate, especially regarding the formation mechanism and age of the Three Gorges, to clarify the formation of the Yangtze Three Gorges. A comparison highlighted a conflict between the erosion time of the Three Gorges and the provenance analysis in the downstream basin, stemming from limitations in research ideas, objects, and methods. Determining the formation time of the Three Gorges necessitates a comprehensive approach that integrates gorge erosion and provenance analysis in the Jianghan Basin. Methods such as monazite fission track, cosmogenic nuclide dating, and geochemical analysis of single-grain minerals offer precise constraints on gorge erosion and aid in establishing a source-sink system between the Jianghan Basin and Sichuan Basin. Drawing on the principles of Earth system science and source-sink systems, this study proposes an analysis of tectonics, landforms, and climatic evolution to understand the evolution of large drainage systems such as the Yangtze River. In particular, a comprehensive analysis of the geochemical characteristics and exhumation histories of the Qinghai-Xizang Plateau, basin development, and geochemical characteristics of detritus minerals is required to investigate the evolutionary processes of large rivers such as the Yangtze River.

The correlation between dissolved cadmium (Cd) and phosphate (PO₄) in the ocean is often used to reconstruct paleoproductivity. Based on the intermediate data product IDP2021v2 released by GEOTRACES (an international study of the marine biogeochemical cycles of trace elements and isotopes) in 2023 and related literature published in the past 40 years, this paper reviews the latest research progress regarding the correlation between Cd and PO₄ in the ocean. It summarizes the Cd-PO₄ relationship in various ocean basins and identifies their major influencing factors. The controlling factors affecting the oceanic Cd-PO₄ relationship differ from surface to deep water and generally exhibit a bilinear correlation. In this study, the key processes controlling the correlation in different water layers are summarized, including the absorption of phytoplankton in the upper water (<200 m), remineralization of particulate Cd and P, mixing of water masses in the intermediate water mass (500~1 000 m), and mixing of different water masses in deep water (>1 500 m). The northward migration of Antarctic intermediate and bottom water from the Southern Ocean is vital in shaping the global ocean Cd-PO₄ relationship.

Research on the Anthropocene—a newly determined geological chronological unit—requires higher temporal resolution, which necessitates the identification of appropriate dating methods. Currently, the main dating methods involve ¹³⁷Cs, ²¹⁰Pb, and ^{239, 240}Pu isotopes. Compared with ¹³⁷Cs and ^{239, 240}Pu dating, ²¹⁰Pb dating has a wider application range, relatively stable geochemical behavior and distribution in the environment, and relatively high dating reliability. It can be used to estimate sedimentation rates in Anthropocene estuaries, lakes, oceans, and other sedimentary environments. This paper summarizes the ²¹⁰Pb dating method, dating principle, and model, and expounds the application of ²¹⁰Pb dating for the establishment of the Anthropocene age scale and acquisition of sedimentary rates in different sedimentary environments, such as estuaries, lakes, and oceans. It also discusses its influencing factors, and indicates that there are certain error sources in the ²¹⁰Pb dating method, such as changes in sedimentary rates, which require further study. Future research should combine ²¹⁰Pb dating with other dating methods to obtain a more comprehensive and accurate Anthropocene chronological framework. ²¹⁰Pb will continue to play an important role in the study of the Anthropocene, helping us to better understand the history and future of Earth.

Based on a global comparison of geological records, the International Anthropocene Working Group (AWG) determined that the onset of the Anthropocene was sometime in the mid-twentieth century (~1950 CE), and the Sihailongwan Maar Lake has been included as one of the candidate sites for the Global boundary Stratotype Section and Point (GSSP) of the Anthropocene. However, humans had a profound impact on the environment of the areas around Sihailongwan Maar Lake even before 1950 CE. Historical sequences of TOC contents, C/N ratios, δ¹³C_org values, Ca/Ti ratios, and concentrations of silicate major elements, such as Si, Al, and K, since 900 CE were reconstructed, with the average resolution being ~10 a, to explore the history of human activities in this region under the background of climate change. Human activities have significantly increased since 1850 CE, and changes in the measured proxies during the Medieval Warm Period and Little Ice Age before 1850 CE generally follow natural laws. The changes in the measured proxies during 1850-1950 CE indicate a rapid population growth, which damaged vegetation and resulted in intensified weathering and deviation of the surface environment evolution from the natural state. Hence, humans had started to be an important force for the geological environment; nevertheless, the changes during this period resulted in mostly local signals. After 1950 CE, the C/N ratios and δ¹³C_org values decreased continuously, indicating that the environmental status of the area around Sihailongwan Maar Lake changed once again under the new government and advanced productivity. This was in sync with the Great Acceleration of the global geological environment and supports the conclusion of the AWG that the onset of the Anthropocene was sometime in the mid-twentieth century.

We analyzed the 2023 funding schemes managed by the Division of Geochemistry (application code: D03), Department of Earth Sciences, National Natural Science Foundation of China, with the goal of understanding the challenges faced by the foundation and finding solutions. Data from the past five years related to the number and type of applications, rate of acceptance, peer review process, and funding status were included in our analysis. The summarized results show that: \mathrm{①} the total number of applications received by the Division of Geochemistry has decreased by 5.1% compared with the number received in 2022; \mathrm{②} in terms of research field, the group of applications coded as “surface geochemistry” was the fastest growing group, entering the top three codes in the Division of Geochemistry; and \mathrm{③} the applicants and principals of projects in the Division of Geochemistry are all more than one year younger than the average age of all applicants under the Department of Earth Sciences. Overall, the Division of Geochemistry faces the challenges of small quantity of projects and slow growth; however, it has the advantage of relatively young research teams. To strengthen future development in the field of applied geochemical research, continued support of basic research (including theoretical and methodological studies) is needed on theories and methods. The research advances presented in project reports completed in 2023 are also discussed.

The Paleoproterozoic Great Oxidation Event (GOE, approximately 2.43~2.06 Ga) is the first significant atmospheric oxygen increase and fundamentally changed the environment and habitability of the Earth. This study summarizes the research progress on the GOE and related carbon cycle perturbation events in the early and middle Paleoproterozoic, focusing on the time frame, initiation process, and mechanism of the GOE, extremely δ¹³C_carb-positive excursion event (Lomagundi-Jatuli event), and carbon cycle perturbation events after the GOE. The initiation of the GOE was intermittent, and research on the initiation mechanism presents diverse viewpoints. The atmosphere-ocean system experienced oxidation and deoxygenation processes during the Lomagundi-Jatuli event, in which the initiation mechanism may have been caused by the increase in ocean primary productivity during this period, but the influence of other mechanisms (such as the deep carbon cycle of the Earth) cannot be ruled out. After the Lomagundi-Jatuli event, global organic carbon burial increased significantly and lasted until approximately 1.7 Ga (Shunga event), during which there was a δ¹³C_carb-negative excursion event (Shunga-Francevillian event). The mechanism of the Shunga and Shunga-Francevillian events remains to be studied.

Reef-building coral, as a biological carbonate and the main body of coral reef ecosystems, is sensitive to environmental changes, has a clear annual growth layer of aragonite skeleton, a large annual growth rate, is easy to date accurately, and can record changes in their growth environment reliably; hence, it is considered an essential carrier for studying environmental changes. Coral has been degraded worldwide in recent decades due to human overexploitation of the coast. Nitrogen is one of the major nutritional elements used to understand coral growth. Nitrogen isotopes can reflect variations in nitrogen sources and biogeochemical cycles, such as recording nearshore nitrogen loading and nitrogen cycles. Many studies on nitrogen isotopes in coral skeletons have been published worldwide; however, relevant reviews are still lacking. In this study, we focused on coral nitrogen source tracing, the nitrogen cycle, and nitrogen isotope analysis. Currently, most studies have been conducted on the history of variations in coral nitrogen sources and have mainly focused on the impact of human activities on coral ecosystems. In the future, coral skeleton δ¹⁵N should be utilized to conduct more research on coral skeleton δ¹⁵N in different seas and at different time scales and to explore new analytical techniques to distinguish the overlap of physiological and environmental signals in combination with other geochemical indicators, which is of great significance for the reconstruction of the paleoceanographic environment and research on current environmental pollution problems.

Groundwater dating is one of the key links in the study of water cycles, especially in hydrogeology. However, the proposed concept of groundwater age and its dating methods are complex and difficult to distinguish, which hinders practical application and further development. This study systematically examines the concept of groundwater age and resident time that often appear in academic circles, simultaneously differentiating and analyzing the derived idealized age, tracer age, apparent age, age distribution, and model age, and comprehensively analyzes and draws a relationship diagram among the definitions. Data of the sample collection and analysis methods, advantages, and disadvantages of the natural isotopes of groundwater dating (including the radionuclide decay method and stable nuclide linear calculation method), and the methods for detecting radionuclides produced by human activities and greenhouse gas tracers are summarized and reviewed. There are two perspectives of groundwater dating methods: water sample points and water systems. The model interpretation methods of multi-tracer combination and age data from the perspective of the water body system (dynamic) are reviewed. Furthermore, we synthetically state that the groundwater dating method should be determined comprehensively according to the research objectives and range of application of tracers, with more attention paid to the study of age distribution characterizing the spatiotemporal dynamics of groundwater systems. Future studies should strengthen the integration and model research of multidisciplinary data, such as geology, hydrology, and hydrochemistry, to establish a numerical model of groundwater flow to describe age distribution and model research.

Groundwater age is an important and widely used hydrogeological parameter. The environmental isotope method is the most reliable method of groundwater dating. Different environmental isotopic tracers have different dating ranges, and the determination of groundwater age from to 50~1 000 a is the “short board” of dating groundwater. The period of 50~1 000 a is a period of frequent human activity. Therefore, dating groundwater that is 50~1 000 years old is scientifically significant. Silicon-32 (³²Si) can be used to determine the age of 50~1 000 a groundwater, but application of ³²Si dating is hindered by the complex and time-consuming pretreatment. The decay of ³²Si to radiogenic ³²P, ³²Si, and ³²P will reach a radioactive balance within three months and achieve consistent radioactive activity. ³²Si and ³²P in 50~1 000 a groundwater have been in radioactive equilibrium, so direct enrichment of ³²P in groundwater can be used for age determination of 50~1 000 a groundwater. Magnesium hydroxide co-precipitation is used for the enrichment of ³²P in groundwater. This method is convenient and rapid. Therefore, ³²P is expected to solve the dating deficiency of 50~1 000 a groundwater. The results of ³²P dating of groundwater in the Jianghan Plain were roughly consistent with those of ³²Si. Therefore, radiogenic ³²P groundwater dating is feasible, convenient, and accurate.

Cherts are widely distributed in Precambrian to Cenozoic orogenic belts and sedimentary basins.The origin and depositional environment of cherts are of great importance in understanding the regional paleogeographic, paleotectonic, paleo-ocean, and paleoclimate evolutions. After summarizing the existing geochemical methods for identifying the origin and depositional environment of cherts, it is concluded that the identification of the origin of cherts should focus on authigenic siliceous minerals and use exotic interfusion materials as references. Effective proxies include Al, Ti, Fe, Th, Ge/Si, Si isotopes, Rare Earth Elements (REE), etc. The essence of the discrimination of the depositional environment of cherts is to distinguish the relative contribution of terrigenous and hydrothermal materials; although previous discrimination diagrams provide practicability, they still involve errors and need to be used carefully. As an important type, cherts outcropped in orogenic belts are closely related to the Ocean Plate Stratigraphy (OPS). Here, a correlation scheme between them has been established. According to this correlation scheme, cherts outcropped in orogenic belts can be divided into the ridge subtype, pelagic abyssal plain subtype Ⅰ, pelagic abyssal plain subtype Ⅱ, ocean island-seamount subtype, intra-oceanic arc subtype, and forearc trench subtype. The cherts-OPS correlation scheme not only provides a basis for reconstructing the original sequence of the accretionary complex in an orogenic belt using cherts, but also considers cherts as important evidence for distinguishing the main oceanic basins from the back-arc and inter-arc oceanic basins. Taking the Eocene cherty ooze obtained by oceanic drilling in the Pacific as an example, it is suggested that the main oceanic basin is characterized by deep-sea plain cherty rocks that are almost unaffected by terrigenous and hydrothermal materials. These cherty rocks have geochemical characteristics such as Fe/Ti values close to 20, Eu/Eu* values close to 1.1 and negative Ce/Ce* values. These results provide new perspectives and references for subsequent research on cherts in orogenic belts.

The early Paleogene was a typical greenhouse climate period in the Cenozoic, during which a series of rapid and short-lived warming events (termed “hyperthermals”) occurred. Hyperthermals were characterized by negative carbon isotope excursion. Among them, the Dan-C2 thermal event of the early Danian is considered to be the first to occur after the biological mass extinction at the end of the Cretaceous; thus, its environmental significance and ecological effects have received widespread attention. However, as research continues, controversies regarding the Dan-C2 event continue to grow: \mathrm{①} The global significance is controversial; in the marine records, the δ¹³C negative excursions during the Dan-C2 event were restricted to planktonic foraminifera and bulk records in parts of the Atlantic and Tethys Oceans, while benthic foraminifera rarely recorded this event, suggesting that it may only be a regional carbon perturbation event. Furthermore, the warming indicated by the oxygen isotopes (δ¹⁸O) of bulk and planktonic foraminifera during this event was limited to surface waters in parts of the North Atlantic, with evidence of warming in bottom waters generally lacking. At the same time, although evidence of the terrestrial Dan-C2 event has been discovered, the terrestrial records still have significant deficiencies in terms of quantification, chronology, and continuity compared with the marine records, which makes it difficult to conduct in-depth and effective comparisons between the terrestrial and marine records; therefore, the global significance of the Dan-C2 event is questioned. \mathrm{②} The trigger mechanism is controversial; the high-precision chronological frame shows that the Dan-C2 event occurred at the eccentricity maximum, indicating that the orbital cycle had a certain influence on the event. Simultaneously, the temporal coincidence of the Dan-C2 event with the last phase of the eruption of the Deccan Traps volcanism implies that greenhouse gas emissions from volcanic activity may have contributed to warming during the Dan-C2; however, the relative magnitudes of both contributions to the event is difficult to assess. Future research should focus on the following: \mathrm{①} Exploring the variability of the Dan-C2 event records in different areas and revealing the reasons for the absence of deep-ocean water records. \mathrm{②} Establishing more reliable terrestrial records and further exploring the global significance of the Dan-C2 event and its triggering mechanism.

Heavy metal migration and enrichment in areas affected by mining and smelting cause severe soil contamination. A thorough understanding of the sources and migration of heavy metals in the soil is the scientific basis for the efficient treatment of soil pollution. In recent years, metal stable isotopes have shown great advantages in identifying sources of soil heavy metal contamination and analyzing heavy metal migration processes, thus acting as powerful tools to trace the environmental behavior of heavy metals. In this paper, we reviewed the analysis technology, tracing principles, and tracing models of metal stable isotopes, determined the isotope fractionations caused by mineral mining and smelting processes (high-temperature smelting, electrochemical processes, and tailing weathering), and discussed the representative applications of metal stable isotopes in the traceability of soil pollution in mining- and smelting-affected areas. The V isotope system is in the initial stages of investigation, and its applications in heavy metal soil source analysis are relatively lacking. Zn, Cd, and Hg isotopes are advantageous for identifying heavy metal contamination sources associated with high-temperature smelting processes. Cu, Tl, and Ni isotopes can directly indicate the ore content of the soil. However, some problems remain, such as the difficulty in analyzing certain systems of metallic stable isotopes, limitations in the application of tracer models, and source uncertainties due to isotope fractionation. Therefore, in the future, it will be necessary to further explore and optimize metal isotope analysis methods, establish more metal stable isotope fingerprints, develop traceability models with stronger applicability and more accurate results, comprehend the characteristics and mechanisms of isotope fractionation in complex interfacial processes and reactions, and strengthen the practical application of metal stable isotopes to trace the history of soil heavy metal pollution.

Selenium (Se) is an essential micronutrient for many organisms (including soil microorganisms, plants, animals, and humans), and has dual biological effects on plants, animals, and humans. The migration, transformation, and enrichment of Se in soil-plant systems have attracted considerable attention for more than half a century. There are five forms of soil Se: soluble Se (SOL-Se), exchangeable carbonate-bound Se (EXC-Se), iron-manganese oxide-bound Se (FMO-Se), organic matter-bound Se (OM-Se), and residual Se (RES-Se), of which SOL-Se and EXC-Se are characterized by bioavailability. OM-Se can be converted into soluble Se by the decomposition of organic matter and is a potentially effective selenium source in soil. The Se content of different plants depends on the soil-available Se content and the Se absorption and enrichment levels of different plants. Therefore, the bioavailability of soil Se plays a critical role in determining the Se content in the food chain, and soil-available Se can improve plant stress resistance by regulating the rhizosphere environment and metabolic processes. Soil-plant system Se migration is a complex biogeochemical process that is dominated by coupled crustal movement, parent rock properties, climate, geomorphology, soil environment (physico-chemical properties and microbial activity) conditions, soil Se content and chemical properties, plant species and biological habits, and field management processes. For the rational utilization of soil Se resources, research needs to focus on Se migration, transformation, and enrichment in plants, especially the main food crops, vegetables, fruit trees, and Authentic Chinese herbs. This study provides basic data for Se biofortification in Se-deficient areas, and crop selection, food selection, and risk assessment in Se-rich areas.

Inland water is an important component of the global carbon （C） cycle and plays a key role in regulating climate change. The Primary Productivity （PP） of inland water is defined as the amount of organic matter produced by primary producers in inland water bodies through photosynthesis per unit time and unit area， which reflects the quantitative relationship between the organic and inorganic C pools. The assessment of inland water PP can help analyze the C cycle mechanism of photosynthesis and quantify the C absorption of aquatic ecosystems to examine the differences in the ecological environment in different regions and evaluate the importance of inland water bodies in the global ecosystem C cycle. There are many methods for estimating PP in inland water， including the light-dark bottle incubation method， the vertically generalized production model method， and the ¹³C method. Each of these have application scopes and limitations. The unreasonable use of PP restricts the understanding of its variability and driving mechanism in inland water bodies. The mechanism， advantages， disadvantages， and applicability of each method are compared by summarizing domestic and international research on PP estimation methods in recent years. Two new methods based on dissolved oxygen concentration or oxygen isotopes， namely， diel O₂ technology and ^18/16O technology， are introduced. This study serves as a reference for research on inland water metabolism， productivity， and nutrient cycles.

Continental subduction belts are usually formed following the development of oceanic subduction; therefore, information on oceanic and continental subduction should be recorded in continental orogens. The Dabie Orogen records the Triassic continent-continent collision between the South China Block and North China Block, but shows little evidence of oceanic subduction. Based on the speculation that rocks related to oceanic subduction may have been covered at the bottom of the Hefei Basin or migrated to the deep mantle during continental subduction, this study conducted detailed zircon LA-ICP-MS U-Pb dating and Lu-Hf isotope analyses for basalt and diabase samples from the central Hefei Basin. The results show that both the diabase from Dashushan and the basalt from Xiaoshushan have late Paleozoic zircon ages, with weighted average ages of 338 Ma and 270 Ma and 349 Ma and 273 Ma, respectively, while the diabase from Jimingshan mainly has Early Cretaceous zircon age. The zircon ages in these mafic igneous rocks are characterized by a continuous distribution from the Paleoproterozoic to the Cretaceous. The two smallest ages indicate the time of Cenozoic mafic magmatism, and the other zircons originate from the recycling of ancient rocks. Based on the comprehensive analysis of zircon preservation under high-temperature conditions and their source, it can be concluded that the Late Paleozoic zircon in the Cenozoic mafic igneous rocks of the Hefei Basin originated from magmatic rocks formed by the subduction of the Paleo-Tethys Ocean. During the Triassic continent-continent subduction, the Paleozoic magmatic rocks were partly transported to the mantle depth and then partially melted with the mantle during the subduction of the Cenozoic Pacific plate to form Cenozoic mafic igneous rocks. This provides direct evidence of the occurrence of late Paleozoic oceanic subduction in the Dabie Orogen.

Source-specific biomarkers are the best targets for isotope analysis and paleoclimatic applications. Compound-specific hydrogen isotope (δ²H) measurements of sterols can be applied to the reconstruction of hydroclimatic conditions and paleo-sea surface salinity. Precise measurements using gas chromatography-isotope ratio mass spectrometry require a high baseline resolution between target analyte and adjacent compounds. However, isotope analysis of sterols for paleoclimatic applications is limited due to the difficulty in purifying complex natural samples. This study aimed to review several improved purification methods of source-specific sterols using liquid chromatography and the applications of compound-specific isotope analysis of sterols in lakes or seas. In addition, we successfully purified dinosterol and brassicasterol from the Chinese marginal sea surface sediments, meeting the requirements for δ²H and carbon isotope analysis. This study provides significant insights and technical support for the paleoenvironmental reconstruction in the Chinese marginal seas.

We summarized the application, peer review, and acceptance of projects managed by the Division of Geochemistry (D03), Department of Earth Sciences, National Natural Science Foundation of China in 2022 and introduced the research advances of projects completed in 2021. The results were as follows: \mathrm{①} The number of project applications for the discipline of geochemistry remained constant in 2022; \mathrm{②} The application formats have improved, while the rates of applications passing preliminary examination were significantly higher than ever before; \mathrm{③} The submission rates in the General Program, Young Scientists Fund, and Less Developed Regions Fund exceeded 143.5%; \mathrm{④} By piloting the mechanism of "Responsibility, Credibility, Contribution" for three years, the Division of Geochemistry has recorded the attitudes, fairness, and contributions of approximately 2000 peer-review experts, in order to explore ways to better play the central role of peer-review in funding decisions; \mathrm{⑤} A significant progress has been made in Isotopic Geochemistry, Elemental Geochemistry, Geochronology, and Cosmochemistry in 2021.

Cretaceous Oceanic Anoxic Events (OAEs) have recorded significant changes in the climatic and paleoceanographic states of the planet and represent major carbon cycle perturbations. In the past two decades, analytical techniques for stable metal isotopes, such as molybdenum, zinc, uranium, chromium, cadmium, and calcium isotopes, have been developed to study OAEs. By systematically summarizing the geochemical characteristics of molybdenum isotopes (δ⁹⁸Mo), zinc isotopes (δ⁶⁶Zn), and uranium isotopes (δ²³⁸U), and research advances on Cretaceous OAEs, we found that molybdenum isotopes mainly reflect the transformation between sulfide and non-sulfide in the regional marine environment during OAEs. Zinc isotopes can reflect different responses of regional marine environments to different processes, such as primary productivity, continental weathering, and sediment burial/decomposition. Uranium isotopes can be used to estimate the global extent of seafloor euxinia. The coupled global C-P-U cycle model can simulate the response mechanism of the global ocean to different processes, such as the formation of large igneous provinces, continental weathering, and biological activities. However, the cyclic fractionation mechanism of these isotopes in marine systems is still in progress, and most research has only focused on the deposition record of OAE2. In the future, it will be necessary to conduct more systematic research on OAEs.

Foraminiferal neodymium (Nd) isotopes are powerful proxies for reconstructing past deep-water currents. Nd isotopes were differentially enriched in foraminiferal calcite and associated authigenic phases (i.e., Fe-Mn oxides). The Nd concentration in the authigenic phases was higher than that in foraminiferal calcite, indicating that authigenic phases are the main carriers of foraminiferal Nd. Authigenic phases associated with foraminifera are generally formed at the seawater-sediment interface, from where they begin to adsorb Nd from the bottom water. During the diagenesis of sediments, the redox state of the sedimentary environment can be changed, resulting in the release and re-adsorption cycling of Nd isotopes in authigenic phases and the exchange with pore fluids, which further impacts the bottom water Nd isotope record in foraminiferal authigenic phases. Therefore, when using foraminiferal Nd isotopes to trace past bottom-water mixing, it is necessary to analyze the evolution of parallel rare earth elements and Nd isotopes extracted from foraminifera and detrital fractions to eliminate the influence of diagenesis on foraminiferal Nd isotopes.