In geoscientific field, the essential object of all the research problems is the physical world which is derived from the crust-mantle interaction and has deeply influenced globally the environment and resources. The metallogenic geochemical theory believes that the metallogenic materials are the internal factors for the metallogenic system to influence the metallogenic process, and taking metallogenic materials as the main body to study the problems of metallogenic materials and metallogenic processes is the basic meaning of the metallogenic geochemical theory, and the core subject of the studies of metallogenic rules and theories. During the mineralization process of metallogenic system, metallogenic materials formed into metallogenic series of corresponding scale. This paper outlines several scientific topics of the metallogenic geochemical studies, among which, the topic of global metallogenic system mainly studies the metallogenic processes and relations of the series of metallogenic regions, provinces and belts formed by metallogenic materials in the context of global metallogenic process; the topic of regional metallogenic system mainly studies the metallogenic processes and relations of ore field series in the context of regional metallogenic process; the topic of ore field metallogenic system mainly studies the metallogenic processes and relations of mineral deposit series in the context of ore field metallogenic process; the topic of mineral deposit metallogenic system mainly studies the metallogenic processes and relations of ore-body series in the context of mineral deposit metallogenic process. The basic research ideas concerning above mentioned studies are discussed in this paper, including the metallogenic materials' geneses and sources, migration and evolution, differentiation and concentration, as well as the zoning relations of each level's metallogenic system and series of the world during the metallogenic processes. The purpose is to summary the metallogenic rules, explore the metallogenic mechanism and guide the mineral resources exploration. Supported by modern technologies and methods of IT(information technology), modeling and AI(artificial intelligence), the metallogenic geochemical theory uses the earth system scientific ideas to study the problems of metallogenic system and metallogenic series, construct the theoretical framework for metallogenic geochemical research, and provide a theoretical basis for the mineral resources exploration, evaluation and development technics and methods.

The Guidong plutonis a crucial part of the EW-directed Dadongshan-Guidong-Wuliting magmatic rock belt in the Nanling region of South China.The Xiazhuang uranium orefield resides in the eastern portion of the Guidong pluton. Researchers have conducted extensive chronological testing on the Guidong pluton, the Xiazhuang uranium orefield, and their veins, obtaining abundant age data. This study synthesized the advances and characteristics of chronological research in the study area. The results show that: (1) The Guidong pluton is a complex pluton formed by Caledonian-Yanshanian magma at 450~151 Ma. From east to west, it can be divided into the Caledonian (450~418 Ma),the Indosinian (246~214 Ma), and the Yanshanian (189~151 Ma) plutons, manifesting a gradually aging pattern from west to east. The Xiazhuang uranium orefield hosts NWW-, NEE-, and NNE-directedmafic veins form eddue to Yanshanian magmatism at 211~91 Ma. These veins can be categorized into five sets according to their ages: 211~185 Ma, ca. 180 Ma, 145~139 Ma, 110~100 Ma, and 93~91 Ma. The uranium mineralization in the orefield lasted from the middle Jurassic to the Miocene with an age of 175~20 Ma, involving five phases and six stages: The Middle Jurassic uranium mineralization (175~162 Ma), the late Jurassic-early Cretaceous uranium mineralization (138~123 Ma, 113~100 Ma),the late Cretaceous uranium mineralization (96~66 Ma),the Paleocene uranium mineralization (65~54 Ma), and the Eocene-Miocene uranium mineralization and modification (52~20 Ma). Among them, 138~123 Ma and 96~54 Ma constituted the primary mineralization epochs. (2) According to the chronological and geological data of the study area,the formation of the Guidong pluton and its uranium mineralization can be divided into the following eight phases and 12 stages. The first phase is the middle-late Caledonian magmatism (450~418Ma),forming subvolcanic and granitic rocks primarily in the northern and eastern peripheries of the Guidong pluton. The second phase is the Indosinian granitic magmatism (246~214 Ma), which was dominated by the granitic magmatism from the middle Triassic to the early stage of the late Triassic.The third phase is the early Yanshanian mafic magmatism and uranium mineralization (211~162 Ma),including three stages: The mafic vein activity from the late stage of the Triassic to the early Jurassic (211~200 Ma), the early Jurassic granitic magmatism(ca.180 Ma), and the middle Jurassic mafic vein activity and uraninite mineralization (179~162 Ma). The fourth phase is the Yanshanian magmatism (163~139 Ma), which formed the Yanshanian pluton in the west of the Guidong pluton, consists of the granitic magmatism during the late stage of the middle Jurassic (163~151 Ma) and the late Jurassic magmatism (145~39 Ma). The fifth phase is the late Yanshanian early Cretaceousuranium mineralization and mafic vein activity (138~100 Ma), which comprises the uranium mineralization at the early stage of the early Cretaceous (138~123 Ma) and the mafic vein activity and uraninite mineralization at the late stage of the early Cretaceous(113~100 Ma). The sixth phase is the late Yanshanian late Cretaceous uranium mineralization and mafic vein activity (96~66 Ma), serving as one primary mineralization phase. The seventh phase is the Himalayan Paleocene uranium mineralization(65~54 Ma).The eighth phase is the Himalayan Eocene-Miocene uranium mineralization and modification(52~20 Ma). 3) The pluton formation and uranium mineralization are relatively concentratedin the study area, such as the Caledonian pluton (450~418 Ma), the Indosinian granitic pluton (238~220 Ma), the Yanshanian pluton (163~151 Ma), mafic vein activity (211~91 Ma), and uranium mineralization (138~123 Ma, 96~54 Ma). There exists a certain time difference between uranium mineralization and granitic pluton formation, indicating that they are non-contemporaneous products. Each uranium mineralization was preceded by mafic vein activity, suggesting an intimate relationship between uranium mineralization and mafic vein activity.

The Rongcheng uplift in North China boasts abundant geothermal resources. Research indicates that the Rongcheng uplift exhibits significantly different physical properties between the bedrock surface and the overlying Cenozoic strata. Moreover, the bedrock surface serves as the primary top boundary of the geothermal reservoir in the Wumishan Formation. Investigating the fine-scale structures, burial depths, and faults of the bedrock surface in the Rongcheng uplift holds critical significance for understanding the distribution and enrichment of geothermal resources in the area and guiding their exploration and production. Through elaborative processing of the north-south reflection seismic profile data of the Rongcheng uplift, collected by the Chinese Academy of Geological Sciences in 2018, this study obtained the high-precision geometric structure of the Rongcheng uplift within a depth of 4 km. The geometric structure was calibrated using geothermal borehole data before interpretation. Key findings are as follows: (1) The Cenozoic sedimentary strata overlying the bedrock surface of the Rongcheng uplift exhibit a nearly horizontal layered distribution, serving as cap rocks of the Rongcheng geothermal field; (2) The bedrock surface of the Rongcheng uplift manifests burial depths ranging from 700 to 3 000 m, with gentle changes in the central portion, and rapidly deepening to around 3 000 m towards the periphery; (3) The Niunan and Rongdong faults converge in the deep part, constituting a fault system along with other medium and small faults, thus facilitating the conduction of water and heat; (4) The geometric structure of the Rongcheng uplift on the bedrock surface contributes to the convergence of heat flow beneath the uplift.

Thenorthern Laojunmiao gold deposit is located in the southern zone of the Beishan area, Gansu Province, and on the northeastern margin of the Tarim block. It resides in a tectonic environment of the Yaodongliang-Xiaoxigong Paleoproterozoic rift basin. This study delineated five comprehensive anomaly zones in the area through a 1∶10,000 geochemical soil survey. As verified by trenching exploration, three gold ore bodies, one gold-silver ore body, and two low-grade gold ore bodies were identified in the comprehensive anomaly zones, suggesting satisfactory prospecting results. Based on the comprehensive geological and geochemical anomaly characteristics of the deposit, this study established an integrated geological-geochemical prospecting model centering on the HT1 comprehensive anomaly zone. Moreover, it proposed the subsequent prospecting direction, providing a significant reference for the deep and peripheral prospecting in the area.

The Xinzhao gas zone of the Dongsheng gas field resides at the junction of three first-order tectonic units:Yishan slope,Yimeng uplift,and Tianhuan depression.Due to the influence of paleogeomorphology and provenance,different channel sediments vary significantly in this zone.The main target layer is the first member of the Shihezi Formation,which hosts a braided river sedimentary system,with tight reservoirs characterized by typical low porosities and permeabilities.The effective sandstone reservoir exhibits a small thickness,pronounced heterogeneity in gas content,and low-resolution seismic data,complicating sweet spot prediction.Hence,this study delved into the critical seismic prediction techniques for sweet spots in braided-river tight sandstone reservoirs.Firstly,the stratigraphic framework was established based on the three-dimensional seismic relative isochronous surface,characterizing the spatial distributions of channel sand bodies at different stages using the relative-spatial-resolution stratal slicing technique.Then,the seismic data were transformed from the time domain to the frequency domain using the wavelet transform time-frequency analysis technique.Based on the analysis of instantaneous spectrum differences in seismic data of different channels,the qualitative gas content prediction was achieved using the low-frequency energy ratio and the ABV absorption attribute,effectively supporting well deployment.Finally,the facies-controlled geostatistical inversion in the depth domain combining logs and seismic data was conducted for quantitative reservoir prediction, guiding the accurate design and optimization of horizontal well trajectories.The application of these techniques has increased the probability of penetration of gas reservoirs in the study area by seven percentage points, demonstrating satisfactory application effects.

In the context of the goals of both peak carbon dioxide emissions and carbon neutrality, scientific and efficient exploration and exploitation of geothermal resources are criticalfor the geothermal industry. To address the commonly concernedtechnical challenges in the exploration of moderately deep geothermal resources, this study investigated the effectiveness of comprehensive geophysical prospecting in the exploration of geothermal resources inthe Linjiadi area, Aohan Banner, Inner Mongolia. Based on the analysis ofthe geological and hydrogeological conditions, this studypreliminarilyascertainedthe geothermal field characteristicsand the hydrochemicalcharacteristics of groundwater in the Linjiadi area. By comprehensively employingcontrolled source audio-frequency magnetotellurics (CSAMT), CSAMT; microtremor survey; radioactive radon survey; this study roughly determined the distribution of strata, magmatic rocks, and fault structures in the study area, inferring the factors controllinggeothermal anomaly areas and hot-water migration.Accordingly, exploration boreholes were arranged, allowing for drilling verificationwith a total length of 960 m. The results show that the comprehensiveapplication of CSAMT and microtremor survey, combined with radioactive radon survey for auxiliary verification, is effective in exploringmoderately deep geothermal resources. This study will provide a methodological reference for geothermal resource exploration in other areas.

This study conducted magnetotelluric profiling in the Bengbu-Huaibei area of Anhui Province. Combined with gravity and magnetic anomalies, it obtained the deep electrical structure, the distribution of primary strata, and the properties of faults in the area, particularly the morphology of the Xuzhou-Suzhouarcuate nappe structure and the development of deep coal-measure strata. The results indicate that: (1) The Upper Paleozoic strataare primarily distributed under the high-resistivity nappe on the surface of the Xuzhou-Suzhouarcuate nappe structure. Theymanifest low-resistivity and low-densityphysical properties and high continuity, suggesting high exploration potential for coal beneath the nappe structure;(2)On the profile, early-stage faulting was dominated by reverse faults, resulting in local Lower Paleozoic and Proterozoicstrata overlying the Upper Paleozoic strata. In the later stage, normal faults predominated, controlling the Cenozoic deposition;(3) The Xuzhou-Suzhouarcuate nappe structure exhibits a 'high-low' double-layer electrical structure at burial depths shallower than 4 km, withthe dominant thrust fault plane composed of F5 and F6 faults. The leading edge of the high-resistivity nappe on the surface extends northwestward to Xiaoxian County and southward to northern Guzhen County, experiencing significant denudation in the Zhahe area. The above results provide critical geophysical information for the basic geological research and mineral exploration in the study area.

The Xilin fault zone,intimately associated with gold and polymetallic mineralization,exhibits high potential for gold resources.In deep exploration,identifying the deep structural characteristics of ore-controlling faults plays a critical role in achieving breakthroughs in gold exploration.Through the analysis of gold metallization regularity and the reflection seismic methods,this study clarified the seismic response to the changes in the attitude of the dominant ore-controlling fault zone in the Jiaodong area.It posited that the changes in energy intensity of the seismic event on the seismic time profile,as well as large continuity deterioration zones,can indicate the changes in the fault attitude,demonstrating high mineralization potential.Moreover,this study predicted and verified the metallization targets in the area.

Surface waves and guided P-waves,as two boundary-related wave phenomena,are a crucial part of the near-surface seismic wave field.This study investigated their generation mechanism and propagation regularity using the high-order staggered-grid finite-difference algorithm.First,it solved the problems like numerical dispersion and boundary conditions in numerical simulation.Based on this,it designed medium models under different thicknesses and elastic parameters for forward modeling.Furthermore,it extracted dispersion profiles and amplitude versus offset curves for analysis.In the case of a low-velocity thin layer on the surface,guided P-waves can be generated when the phase velocities of P and SV waves from the same source exceed the S-wave velocity but are less than the P-wave velocity of the underlying high-velocity layer.In media with high Poisson's ratios(>0.4),the phase velocities of surface waves and guided P-waves are sensitive to the S- and P-wave velocities,respectively.Surface waves and guided P-waves usually contain near-surface information that is unavailable in refracted and reflected waves.The appropriate acquisition,analysis,and inversion of near-surface information enable the establishment of a high-resolution near-surface model.This study generalized the generation conditions and wave field characteristics of surface waves and guided P-waves under the same source and deepened the understanding of their propagation regularity,laying a foundation for inversion and denoising research.

The exploitation of thin-bedded and thin-interbedded hydrocarbon reservoirs has garnered increasing attention.However,seismic data of thin-bedded reservoirs exhibit low resolution,and conventional convolution models fail to simulate the complex wave field propagation phenomena in thin-bedded reservoirs,complicating the seismic prediction of such reservoirs.Hence,based on the transfer matrix method for layered media,this study developed a normal-incidence reflectance method.Using the new method,it conducted forward modeling on several typical thin-interbedded reservoir models.Then,the forward modeling results were analyzed through frequency spectrum analysis to explore the filtering effects of thin-interbedded reservoirs on seismic reflection waves.Compared to the transfer matrix method for layered media,the normal-incidence reflectance method is more applicable to the investigation of thin-interbedded reservoirs under longitudinal wave incidence,significantly enhancing the forward modeling efficiency.Moreover,studying the reflection filtering effects of thin-interbedded reservoirs in the frequency domain somewhat eliminates the shortcomings of insufficient resolution in the time domain.The frequency spectrum analysis of thin-interbedded reservoir models shows that the normal-incidence reflectance method can effectively preserve the interbed information of thin-interbedded reservoirs.As revealed by the frequency spectrum analysis of the forward modeling results based on this method,the changes in the amplitudes and notch points of frequency spectrum curves can reflect the changes in the number of interbeds and sandstone-mudstone ratios in thin-interbedded reservoirs.This finding is critical for determining the spatial distributions and properties of thin-bedded reservoirs in the fine-scale exploration of oilfields.

The extensively applied audio magnetotellurics (AMT) has become a primary method for deep geophysical exploration of solid mineral resources. However, its data processing and interpretation often only consider electromagnetic effects but ignore induced polarization (IP) effects, which is inconsistent with actual geological conditions. Based on the two-dimensional AMT finite-element forward modeling with IP effects, this study simulated the magnitude and regularity of the influence of various parameters of IP effects on the two-dimensional forward response. Moreover, this study conducted a numerical simulation on the geoelectric model of sandstone uranium deposits in the Erlian Basin. The results show that: (1) With an increase in the values of polarizability, frequency correlation coefficient, and time constant, the two-dimensional AMT forward modeling with IP effects based on the Cole-Cole model primarily reduced the abnormal response value of two-dimensional forward modeling apparent resistivity and increased the abnormal response value of impedance phase. This is beneficial for detecting low-resistivity targets rather than high-resistivity targets; (2) The zero-frequency resistivity and polarizability in IP effects exhibit a significant influence on the two-dimensional forward response. The influence of both frequency correlation coefficient and time constant on the forward response primarily depends on the polarizability. High polarizability suggests their significant influence on the forward response; (3) In the case of disseminated and sulfide-bearing lithologies in the sand bodies of sandstone uranium deposits, greater IP effects will significantly influence the detection of target sand bodies using frequency-domain AMT. Therefore, forward modeling is necessary before detection to determine the magnitude of IP effects.

The performance of marine gravimeters directly determines the quality of measured data, while their stability serves as a critical indicator reflecting their performance. Based on the static test conducted using a DGS-AT1M marine gravimeter, this study analyzed the dominant factors affecting the measured results in the static test. It explored the method and process for stability assessment in the static test, analyzing and assessing the stability of this marine gravimeter.First, this study calculated the changes in the theoretical gravity value of earth tide, correcting the earth tide effect on static measurement results. Then, this study analyzed the single-day data and the overall data. Finally, based on the stability assessment process, this study calculated the zero-drift rate, monthly drift, and accuracy of the marine gravimeter using the residual measured values after earth tide correction. The calculation results show that this marine gravimeter yielded a monthly drift value of -1.020 mGal, and high zero drift linearity at a drift rate of -0.034 mGal/day. This marine gravimeter exhibited a measurement accuracy of 0.085 mGal, aligning with the gravity survey specifications.Therefore, it can be applied to high-precision marine gravity surveys.

The accurate lithologyidentification of volcanic rocksserves as a significant foundation for the efficient exploration and exploitation of volcanic reservoirs. However, volcanic reservoirs exhibit intricate lithologies, longitudinalmultistagesuperimposition, and fast transverse phase transition, which reduce the accuracy of crossplots in lithologyidentification ofvolcanic reservoirs. Based on the optimal parameter combination of the model determined through grid search and orthogonal experiments, this study quantitatively evaluatedthe effects of conventional log curves on the lithologyidentification of volcanic rocks. Withthe natural gamma ray, compensated neutron, sonic interval transit time, and formation resistivity as lithologic indicators, this study builtan intelligent model for the lithology identification of Carboniferous volcanic rocks in the Dixi area in the Junggar Basin using therandom forest method. This study identified the lithologies of thecored intervalswith a cumulative thickness of 870 m infive cored wells in the study area, with the coincidence ratesof the identification results with thin section identification results and core description resultsreaching 76.67% and 85.98%, respectively. This suggestssignificant identification effects. Therefore, this studysets the stagefor the fine-scale evaluation of volcanic reservoirs in the study area.

For the underground construction of coastal cities in China, there is an urgent need to accurately position unfavorable geobodies such as faults and boulders. Based on the geological characteristics of coastal cities, this study conducted 3D numerical simulations using a high-density resistivity method, determining the effects of the electrical properties and thickness of the overburden on the survey results, as well as the DC electric field characteristics varying with the sizes and burial depths of detection targets. The results show that the resistivity difference between the overburden and the targets serves as a critical factor in determining the influence of the overburden. For low-resistivity fracture zones, a higher resistivity of the overburden signifies more prominent responses from the fracture zone. Under middle- to high-resistivity overburden conditions, shallowly buried boulders can be easily found, and larger boulders exhibit more significant high-resistivity characteristics. In the exploration along the Qingdao metro line 5, the high-density resistivity method played a vital role in exploring fracture zones and boulders, verifying the effective application effects of the method. The results of this study provide a basis for selecting engineering exploration methods and determining operating parameters in coastal cities.

The fault-controlled fractured-vuggy carbonate reservoirs in the Tarim Basin exhibitconsiderable burial depths, complex structures, and highly developed faults. Faults serve asa dominant factor controlling oil and gas accumulation and possible hydrocarbon migration pathways in the study area. Hence, it is critical to predict their spatial distributions and sizes. There existvariousfault detection attributes, which characterize fault scales and features differently due totheir different calculation methods.Moreover, conventional attribute detection ignores the use and constraints of logs. For more complete and accurate fault prediction results, this study selected multiple fault detection attributes for fusion using the feedforward neural network algorithm, with logs as prior information. First of all, a sample database for fault feature identification was established using fault attributes (like AFE, likelihood, and dip angle) with distinct characteristics anddiscrimination criteria of fault types, including lost circulation data, imaging logs, and seismic event dislocations.The deep feedforward neural network was trained based on the sample database.A neural network prediction model with a minimum prediction error was obtained by comparing and testing the learning effects under different hidden layer depths. Finally, the neural network prediction model was applied to the fault prediction of the study area. The comparative analysis reveals thatthe fault prediction using deeplearning-based fused attributesyielded prediction results more consistent with the log-based interpretation results, and could synthesize the information of faults with different scale characteristics, thus effectively improving the prediction accuracy and reliability.

The anisotropy caused by fractures is ubiquitous in formation media.The inversion and prediction of fracture parameters based on anisotropy can somewhat improve the inversion accuracy and prediction reliability of fractures.This study established a reflection coefficient equation based on vertical transverse isotropy(VTI) media.Then,it improved the standard particle swarm optimization algorithm by setting the exit probability based on the Metropolis criterion of the simulated annealing algorithm.Consequently,it obtained the inversion results of compressional- and shear-wave velocities and anisotropy parameters in VTI media.By combining anisotropy-related attributes,Poisson's ratio,and Poisson's velocity, this study predicted the fillers in fractures.The improved algorithm was tested for stability and noise resistance using a two-layer model and a Marmousi2 model,demonstrating its feasibility.Furthermore,the improved algorithm was applied to predict the water-bearing property of fractures using real coal mine data,validating its effectiveness.

Random noise in seismic data impairs the quality of the data,thus affecting the accuracy of subsequent processing and interpretation.Conventional denoising methods,constrained by prior conditions,exhibit low efficiency.Neural networks possess a strong feature extraction ability,which can make up for these shortcomings.However,the limitations of convolution kernels in conventional neural networks may lead to the loss of global information.Hence,this study introduced a retractable attention mechanism to the convolutional neural network (CNN).This mechanism presents both dense and sparse self-attention modules in the CNN.The alternate use of the two self-attention modules can significantly enhance the performance of the CNN and expand the receptive field.The shallow and deep features of seismic data were extracted using the convolutional layer and self-attention modules.Combined with CNN's local modeling ability and Transformer's global modeling ability,they contributed to enhancing CNN's global interaction and ability to reduce noise and deal with details.As indicated by the experimental results of synthetic and field data,the method used in this study can more effectively suppress noise and retain effective information of seismic data compared to Unet and DnCNN,significantly improving the signal-to-noise ratio and thus assisting in the processing and interpretation of seismic data.

Based on the combination ofdata- and model-driven approaches, this study expanded the labels of the training set through model inversion results, and added the model inversion objective function to the deep learning algorithm. By constructing a new loss function, this study proposed a seismic impedance optimization inversion method combining model inversion with deep learning inversion. The semi-supervised deep learning network inversion under a pseudo-label was achieved using the RNN network structure. The network inversion results were used as the initial model to participate in the model inversion. The final optimization inversion was completed by continuous iterative optimization of both network and model inversion. The method proposed in this study proves to possess high inversion accuracy and practicability, as demonstrated by the synthesis of the Marmousi model and the actual data.

The reverse time migration (RTM) technique can accurately simulate the propagation of seismic waves in subsurface media and image subsurface structures.However,seismic waves can be reflected,refracted,or scattered in weakly illuminated areas,leading to locally reduced signal-to-noise ratios (SNRs) in RTM imaging results.The staining algorithm can achieve the tracking and imaging of known geobodies by generalizing the wave equation to the complex domain.It requires a conventional real velocity and an imaginary velocity field as inputs.A conventional staining algorithm requires known real subsurface structures,which is impractical in this study.Hence,this study put forward regional staining to promote the practical development of the staining algorithm.Focusing on subsalt imaging,this study proposed a staining algorithm-based RTM imaging method for subsalt structures.The salt dome model demonstrated that the method proposed in this study can significantly improve the imaging SNRs and resolution of self-selected target regions.

Both the controlled source audio-frequency magnetotellurics (CSAMT) and the microtremor survey exhibit promising application prospectsunder strong urban interference. However,single geophysical inversion methods are challenged by a multiplicity of solutions. To achieve the complementary advantages of different geophysical methods, and address the lateral discontinuity of single-point inversion, this studyexplored the quasi-two-dimensional joint inversion of the CSAMTand microtremor survey data. It enabled the joint inversionby introducing a lateral constraint matrix into the objective function for joint inversion and employing the limited-memory Broyden-Fletcher-Goldfarb-Shanno (LBFGS) algorithm. The reliability and effectiveness of the joint inversion were verified using the inversion example of synthetic data from theoretical models. The results show that compared to single data inversion, the joint inversion can effectively improve the accuracy of inversion results, with the resistivity model more consistent with theshear-wave velocity structure. Moreover,lateral constraints can effectively reduce the discontinuity of the physical parameters of adjacentsurvey points. The quasi-two-dimensional joint inversion with lateral constraints enhances the inversion reliability by obtaining more reasonable profile results of physical parameters and structures with the efficiency of single-point inversion.

The spatiotemporal changes in soil organic matter (SOM) hold great significance forthe elevation of both regional soilquality and the potential of soil carbon sequestration. Based on two periods of soil data from the second soil reconnaissance surveyof Heilongjiang Province in 1980 and thesoil geochemical survey of Heilongjiang Province in 2020, this study analyzed the spatiotemporal changes in SOM content in surface soil (0~20 cm) in the Songnen and Sanjiang plains in Heilongjiang Province over 40 years through spatial analysis in GIS. Furthermore, this study summarized the distribution patterns of SOM lossof different soil types in various cities and counties. The results indicate that the average SOM content in the surface soil in the major two plains decreased by 5.68×10^-3over 40 years, generallyexhibiting a downward trend. Areas with decreased SOM are primarily distributed in Qiqihar, Daqing, western Suihua of the Songnen Plain, along with Hegang and western Jiamusi of the Sanjiang Plain, with the largest decreased amplitudeobserved in the Qiqihar Zhaoyuan area along the Nenjiang River basin. Regarding soil types, swampsoils exhibited the highestSOM loss rate (-44.68%), while grassland soilsexhibited a contribution rate for SOM of 44.14%, which established these soilsas the soil type making the most significant contribution to SOM in both plains. The SOM loss area in Wangkui County, Zhaoyuan County, and Daqing City accounted for over 72.11% of the total. This study determines the spatiotemporal changes in SOM in the major two basins in Heilongjiang Province on a scale of 40 years, providing a theoretical basis for the primary prevention and control targets of regional black soil degradation.

Based on relevant eco-geochemical survey data collected fromthe Lixiahe plain area in Jiangsu Province,this study systematically explored the geochemical characteristics of elements in Se-rich soils and the genetic mechanism through elemental distribution contrast, correlation analysis, R-type cluster analysis, and principal component analysis. This study can be referenced for the rational production and utilization of Se-rich land resources of the Quaternary sedimentary type. Key findings are as follows: (1)Se-rich soilsin the Lixiahe area are typical Quaternary sediments, and the closed lagoon facies sedimentary environment characterized by rich organic matter and slightly reducing conditions plays a foundational role in the formation of local Se-rich soils;(2) Typical element association, Se-OM-N-K-Fe-Co, in Se-rich soils is primarily located within a depth of 30 cm from the surface, with Se content ranging mostly from 0.3×10^-6 to 0.4×10^-6 in a uniform distribution; (3) Significant positive correlations between Se and some other elements can be observed in the soils, with the correlation coefficients (r)between Se and OM,and Se and CEC being 0.74 and 0.66, respectively.In contrast, Se exhibits a significant negative correlation with pH, with a correlation coefficient of -0.35; (4) The formation of Se-rich soilsmight have experienced three Se enrichment stages: the initial enrichment in soil parent materials, the re-enrichment during soil formation, and the supergene enrichment after soil formation, accompanied by interference from non-lagoon facies sediments (such as marine sediments). Organic matter adsorption, colloid adsorption, and biogeochemistry constitute the main causes of Se enrichment in the soils; (5) The Se-rich soils are also relatively enriched in heavy metal elements like Cu, Pb, Zn, Ni, Co, and V, which are within the national limit standards.

Water and soil erosion affects the distribution and partitioning of elements in soils. The distribution and partitioning patterns and bioavailability of trace beneficial elements such as selenium (Se) and zinc (Zn) in water and soil erosion areas serve as significant factors for measuring the ecological effects of water and soil erosion. Through the geochemical survey of soil and crops, this study investigated the geochemical characteristics and bioavailability of Se and Zn in the water and soil erosion area of Changting County, Fujian Province, obtaining the critical geochemical parameters of Se and Zn in soil and crops in the study area. The results are as follows: (1) The soil Se and Zn contents in the study area show median values of 0.43×10^-6 and 46×10^-6, respectively; (2) Se is enriched in the soil developed from metamorphic rocks, whereas Zn is enriched in the soil developed from metamorphic rocks and granites; (3) The soil Se and Zn contents are higher in bamboo forests compared to other land-use types; (4) The soil Se content shows a decreasing trend as the water and soil erosion intensifies; (5) The bio-concentration factors of Se and Zn are significantly positively correlated with w(Si)/w(Al) ratios, and negatively correlated with Se, Zn, and organic matter. As indicated by the results above, the distribution and partitioning of soil trace beneficial elements like Se and Zn in the study area are primarily subjected to metamorphic rocks and granites. The water and soil erosion is accompanied by a significant soil Se loss. The bioavailability of soil Se and Zn is reduced by the adsorption of clay minerals and organic matter. Additionally, there may be a large proportion of inactive Se and Zn in the soil of the water and soil erosion area.

To investigate the migration characteristics of heavy metals in the soil-crop system of Fenghuang County, Xiangxi Tujia and Miao Autonomous Prefecture, this study systematically collected 120 groups of local staple crop and root-soil samples (50 for kiwi fruit, 36 for rice, and 34 for corn). Agricultural crop samples were tested for seven indicators, including As, Cd, Cr, Cu, Hg, Pb, and Zn. Root soil samples were tested for 18 indicators, including pH, Mn, Se, As, Cd, Cr, Cu, Hg, Ni, Pb, Zn, and physicochemical properties. The test results were used to analyze the heavy metal contents of soil and crop seeds in the study area. Furthermore, the migration and enrichment of Cd in the soil-crop system were examined through multiple linear regression and correlation analysis. The results are as follows: (1) The study area is dominated by weakly acidic soil, with Cd content higher than the background value in Hunan Province. The high-value zones of Cr, Ni, and Cu are primarily distributed in the southwestern and southeastern portions of the study area. The Cd and pH in the soil show higher values in the west and lower values in the east; (2) In crop seeds, the three heavy metals with the highest enrichment coefficients are Cd, Zn, and Cu. The migration of Cd in the soil-crop system of the study area is principally influenced by soil pH and texture. A higher pH value and finer texture correspond to weaker migration of Cd. Additionally, Cd migration is affected to some extent by the contents of Mn, CaO, and total organic carbon in the soil. The relatively low heavy metal enrichment coefficient of kiwi fruit in the study area makes kiwi fruit suitable for production promotion.

The environmental capacity of lake sediments serves as a significant indicator for assessing the environmental carrying capacity of lake systems, effectively reflecting the stability and sustainability of lake systems.This study investigated the Dongping Lake in the lower reaches of the Yellow River basin by determining 11 heavy metal elements, including As, Cd, Cr, Co, Cu, Hg, Mn, Ni, Pb, Tl, and Zn, in the sampled surface sediments. It delved into the spatial distributions of heavy metal contents and environmental carrying capacity using statistical analysis and geographical information system (GIS) technology. Moreover, it predicted the trend of environmental capacity changes of heavy metals at a centennial scale. The results indicate that: (1) The maximum content of As in the surface sediments of the study area exceededits risk screening value (allowable limit) for soil contamination, whereas those of other elements were below corresponding allowable limits;(2) The average single environmental capacity index (P_i) values of heavy metal elements decreased in the order of Hg, Pb, Cr, Ni, Zn, Cd, Cu, Co, Mn, Tl, and As. Among these heavy metal elements, As displayed overload level and warning level points, whereas Mn and Tl manifested warning level points. The composite capacity index (P_i) was calculated to be between medium and high capacity levels. The composite capacity level measured based on the inferior level of P_i suggests a medium capacity to overload level distribution in the study area;(3) The static annual capacity limits of heavy metal elements decreased in the order of Mn, Zn, Cr, Ni, Cu, Pb, As, Co, Tl, Cd, and Hg, whereas the dynamic annual capacity limits decreased in the order of Mn, Zn, Cr, Ni, Pb, Cu, Co, As, Hg, Cd, and Tl. The static and dynamic capacity limits will show a steeply to gently decreasing trend in the 5~40 years and 5~15 years, respectively, followed by a gentle and stable trend. Regardless of the number of years, the average dynamic annual capacity limit is higher than the average static one, suggesting a high environmental carrying capacity.This study reveals the current status and future trends of environmental capacity in the Dongping Lake, providing a scientific basis for the environmental quality assessment and ecological conservation and restoration of the lake.

To investigate thehydrochemical characteristics of shallow groundwater in a chemical industrial agglomeration area in Yantai City, this study collected 12 sets of groundwater samples and one set of surface water samples from the study area and its surrounding areas. It analyzed the hydrochemical characteristics ofgroundwater by integrating various methods like mathematical statistics, Piper and Gibbsdiagrams, correlation analysis,the ion ratio method, and principal component analysis. Moreover, it explored the impacts of production activities in thestudy area on the groundwater environment. The results show that:(1) The shallow groundwater in the study area was neutral to slightly alkaline, with the primary hydrochemical type being the SO₄-Ca·Na type, followed by the SO₄·HCO₃-Ca·Mg, HCO₃·SO₄-Ca·Na, SO₄·HCO₃·Cl-Ca·Na, SO₄·Cl-Ca, SO₄·HCO₃-Ca, and SO₄-Na types;(2) The chemical composition of shallow groundwater originated principally from the combined effects of evaporite and silicate dissolution; (3) Chemical enterprises contributed significantly to groundwater contamination. A nearercontamination source is associated with higher ion concentrations,suggesting more severe groundwater contamination. Along the groundwater flow direction, contaminants in upper reaches are prone to migrate and accumulate toward lower reaches,aggravating groundwater contamination in lower reaches.