Based on the data on the geology, minerals, exploration, and geochemistry of more than 30 fluorite deposits in the Heyu-Checun area, western Henan Province, this study summarized the types, spatial distribution, and geochemical characteristics of fluorite deposits in the area and explored the genesis and material sources of the deposits. The fluorite deposits in this area have simple types and are distributed in Yanshanian granites and along the fault zone of the external contact zone of the granites. The formation ages of the Heyu and Taishanmiao plutons are 124.7~148.2 Ma and 115~123.1 Ma, respectively. The mineralized age of fluorites is 120~126.8 Ma, indicating that the mineralization occurred in the late stage of the intrusion of the Heyu pluton and the early stage of the intrusion of the Taishanmiao pluton. The ore-forming fluids belong to the NaCl-H₂O system with a medium-low temperature, a low salinity, and a low density, indicating that the deposits in the area are medium-low-temperature supergene hydrothermal fluorite deposits. The chondrite-normalized REE patterns of fluorites in the area can be divided into slightly leftward, flat, and rightward types dominated by the rightward type. Moreover, the rightward chondrite-normalized REE patterns of fluorites are similar to those of the Yanshanian granites, both showing strongly negative Eu anomalies and weakly negative Ce anomalies. This finding indicates that the Yanshanian granites provide materials for the formation of fluorites. The metallogenic element F may mainly originate from the Heyu and Taishanmiao plutons, while the metallogenic element Ca partly comes from granites as surrounding rocks.

The primary geochemical halos, which exist in nearly all types of deposits, especially in hydrothermal deposits, serve as an essential geochemical indicator for deep prospecting. Many studies have been presently carried out on the elemental enrichment/depletion and component zoning in primary geochemical halos. However, there is a lack of reports on the spatial variations of elements and associated elements. This study collected geochemical data from 2,279 samples of the boreholes in the Zhajiatongna gold deposit and then calculated the enrichment factors and conducted a multivariate analysis to characterize the spatial variations of elements and element associations of the deposit. The element associations representing the components of surrounding rocks and mineralized components were extracted from all samples including surrounding rock samples, mineralized surrounding rock samples, and ore samples. They reflect that the deposit was formed by the superposition of mineralized components on the components of surrounding rocks in essence. Moreover, high-medium- and medium-low-temperature element associations were extracted from the ore samples, and high- and medium-low-temperature metallogenic element associations were extracted from the mineralized surrounding rock samples, indicating mineral precipitation mechanisms and the differences in the precipitation time and space. As suggested by the results, the primary geochemical halos of the Zhajiatongna deposit show the following variations from the periphery to the mineralization center: the mineralization-related elements generally exhibit an increasing trend in terms of enrichment degree and the number of enriched element types quantitatively, and the high-medium-temperature-medium-low-temperature and high-temperature-medium-low-temperature metallogenic element associations are superimposed on the surrounding rocks - mineralized element associations.

The Xiong'an New Area is located in the middle part of the Jizhong Plain.The Cenozoic strata in the underground structure of the area have a large thickness,good stratification,and relatively stable tectonic activities.To finely determine the shallow geological structures,ascertain the fault structure characteristics,and improve the shallow exploration accuracy,this study combined two-dimensional seismic surveys and high-density resistivity sounding and made the following important progress.①This study finely determined the geological structure and the spatial distribution characteristics of fault structures at a depth of less than 200 m in the Xiong'an New Area;②This study constructed a three-dimensional visualized geological structure model,which intuitively displays the stratigraphic fluctuation pattern of Cenozoic strata and the spatial distribution of main fault structures;③This study analyzed and summarized the application of geophysical methods under the background of urbanization-induced high disturbance,including their exploration depths,horizontal and vertical resolution,response characteristics of geological bodies,and applicability.This study effectively supports and serves the planning,construction,and underground-space development and utilization in the Xiong'an New Area and serves as a reference for the geophysical exploration of urban underground space in hugely thick sedimentary basins.

A ringed molten rock mass in eastern Tianshan, Xinjiang is closely related to Au-Pb-Zn mineralization. Since the mineralization occurs in the fault fracture zone near the outer contact zone between the rock mass and strata, it is necessary to find out the spatial distribution of the rock mass and the development of the fault structure. The processing and analysis of the 1∶25 000 high-resolution airborne transient electromagnetic and aeromagnetic data yielded the following airborne electromagnetic characteristics of the rock mass. The ringed molten rock mass displayed positive and negative alternating ringed aeromagnetic fields. There were four NWW-trending banded zones with strong electromagnetic responses along the ringed molten rock mass, with a time constant of generally 0.07~0.18 ms. Seven NWW-trending faults were inferred and interpreted using the high-value band of the electromagnetic response of the 23rd trace of the dB/dt X component and the aeromagnetic anomaly zone with amplitude of 5~10 nT. By combining the airborne electromagnetic characteristics and three-dimensional inversion results of magnetic vectors, the lithology and structures of the study area were inferred and interpreted again, roughly ascertaining the three-dimensional distribution characteristics of the diorites. Based on these results as well as the known metallogenic geological conditions and the airborne electromagnetic characteristics, two prospecting favorable areas were delineated in the areas with strong electromagnetic responses to the west and southwest of the ringed molten rock mass. This study provides important information on the deep prospecting of the rock mass.

The drilling engineering for shale gas in carbonate areas in China is facing prominent carbonate karst. It is necessary to carry out near-surface geophysical prospecting before drilling and reasonably select the well locations in order to ensure the safety of the well site and reduce the drilling engineering risks. Taking the siting of Well Guirongye-1 in Rong'an County, Liuzhou City, Guangxi Province as an example, this study conducted the application research of well siting before drilling comprehensively using three geophysical prospecting methods, namely the high-density resistivity method, the audio-frequency magnetotellurics method, and radon survey, achieving satisfactory results. Well Guirongye-1 did not encounter a fault fracture zone near the surface, which is basically consistent with the interpretation results of comprehensive geophysical prospecting. This result indicates that the comprehensive geophysical prospecting method is feasible and effective in the siting of shale gas exploration wells in the carbonate areas in south China. This study will provide a certain reference for the well siting before drilling in similar areas in the future.

An application test of the broadband magnetotelluric method (BMT) was carried out in the Mandulatu area based on the construction needs of a large-scale sandstone-type uranium deposit base in the Erlian Basin. The purpose is to study the detection ability and effect of this method at a depth of 2,000 m and above, provide effective technical support for the evaluation of uranium resources in the area, and improve the effects and benefits of uranium prospecting. In this study, the data acquisition time and the lowest frequency were tested by the test area method. Given the work efficiency and benefit, it is determined that the lowest detection frequency is 0.10 Hz and the observation time is 60 min so that the prospecting depth of Erlian Basin can reach the requirement of 1,500~2,000 m. The comparative analysis of the test results with borehole and shallow seismic data shows that BMT is feasible in solving geological problems such as caprock structure, basement structure, sand body development characteristics of the target layer, and fault structure in the basin.

Geothermal measurement is the most direct method to study the distribution of geothermal field. The intensity and distribution of geothermal heat sources directly affect the distribution of the soil temperature field in the surface layer of the earth's crust, especially the existence of thermal reservoirs and thermal transport channels can cause anomalies in the distribution of the geothermal field. Geothermal measurements were carried out in 16 civil wells and 32 boreholes in the study area to analyze the distribution of geothermal field and the pattern of underground hot water activity, and the results were obvious.The results show that the geothermal field at shallow depths is laterally consistent with that at deep depths, with the temperature tending to increase toward the northeastern corner of the study area, and that the anomalous geothermal areas are distributed as a NNE-oriented strip, with a width of about 700 m, which is consistent with the NNE-oriented faults. The highest geothermal point is located at the intersection of the NW and NNE-trending faults.. The vertical geothermal distributions in the study area are distinct. The geothermal water is limited to a narrow area. The low-temperature groundwater inflows into the tectonic faults and karsts, with volumes controlled with the development degrees of them, leading to an abnormal geothermal gradient. This anomaly also indicated that the geothermal water in the Lasozi Mountain area is mainly stored in fissures and karst caves of limy dolomite or breccia rocks, with fissures and caves providing good pathways for the geothermal water to flow. The geothermal measurement method has traced the range of geothermal anomalies in the study area, which provides an important basis for further geothermal investigation.

A geothermal field has been discovered in the Tianshan Sea World on the eastern margin of the Yinchuan Basin, revealing that the region has high-quality geothermal resources. The geological conditions for the formation of the geothermal field are significantly different from those of the conduction-type geothermal resources within basins, providing a new direction for the study of clean energy in the Yellow River Basin in Ningxia. This study processes and analyzes the data of 1∶50,000-scaled gravity surveys, controlled source audio-frequency magnetotellurics (CSAMT), and microtremor survey based on regional geological and geophysical characteristics. The results of the study are as follows. The uplifting zone of the Ordovician basement lies on the east side of the Lingwu Sag and spreads in an "S" shape along the Yellow River Fault. This zone reaches its highest part in the Tianshan Sea World, where it merges with the NW-trending local uplift. The Ordovician of the deep reservoirs in the geothermal field is characterized by medium-high resistance. The Carboniferous-Permian of the first cap rock at a moderate depth shows medium-low resistance and low seismic velocity. The Paleogene-Neogene of the second shallow cap rock corresponds to the formation with low resistance and low seismic velocity. Using these results, three prospective areas for developing and utilization of geothermal resources have been predicted.

The mineralization of deposits of rare metals such as tantalum and niobium in China is mostly related to granite pegmatite. The enrichment of rare metals in these deposits is accompanied by the formation of radioactive minerals, such as albite, monazite, and high-grade uranium, and these deposits have paragenetic and associated minerals uranium deposits. Therefore, radioactive prospecting has become the most convenient and effective method to explore deposits of rare metals such as REEs, Nb, and Ta. Based on the close correlation between mineralization and radioactivity of rare earth minerals, this study fully investigated the parameter characteristics of the surveyed energy spectrum data through the combination of airborne radioactivity measurement and ground gamma spectrometry measurement to determine prospecting indicators. A new niobium-tantalum-rubidium polymetallic mineralized point was discovered in the Nancha area, Yichun City using the radioactive prospecting method, which was thus proven effective.

The Lingwu depression,located in the southeastern part of the Yinchuan Faulted Basin,has a complex geological tectonic framework and serves as the turning and intersection part of structures due to the two Himalayan tectonic stresses,namely the EW-direction tensile stress of the Ordos block and the NE-direction compressive stress of the Qinghai-Tibet Plateau. Since 1970, more than 3000 earthquakes with magnitudes of greater than 2.0 have been monitored in the Yinchuan Basin and its periphery. Among them, most of the small and moderately strong earthquakes occurred in the Lingwu depression, which, therefore, has serious hidden risks of earthquake disasters. Previous studies indicate that fault structures are the cause for the earthquakes and that strata serve as the main reason for the earthquake secondary disasters in this depression. To interpret the geological structures in the basement of the Lingwu depression, this study finely characterized the basement characteristics of the Lingwu depression using the 2.5D human-computer interactive inversion technology based on the 1∶50,000 regional gravity data and the constraints of data on drill holes, seismic profiles, magnetotelluric sounding, and controlled source audio-frequency magnetotellurics (CSAMT) profiles, thus providing a basis for the prevention and control of earthquake disasters.

The Weiquan silver-copper polymetallic deposit has received extensive attention because of its unique genesis. This study analyzed the anomaly characteristics shown in the integrated gravity-magnetic-electrical geophysical planes and sections of the Weiquan silver-copper polymetallic deposit. Then, it obtained the interpretation model of geophysical anomalies through the forward and inverse calculations of the typical sections. Based on the distribution pattern of existing ore bodies and the metallogenic model summarized in previous studies, this study established the geological-geophysical prospecting mode of this area. Moreover, this study proposed the geological-geophysical prospecting model of this area, aiming to provide a basis for prospecting prediction.

At present,the targets of oil and gas exploration have transformed from simple structural oil and gas reservoirs into deep complex structural oil and gas reservoirs.The small thickness,wide distribution,and hidden occurrence state of the reservoirs pose great challenges to seismic migration imaging technology.Compared with ground seismic,the seismic sources of the borehole seismic are located in wells and close to target layers.Meanwhile,the times that wave field induced by the borehole seismic passes through the low-velocity zone reduce by one.Therefore,the borehole seismic has the advantages of high signal-to-noise ratio (SNR) of data and strong reservoir identification in theory and thus can serve the purpose of the fine imaging of the reservoirs around wells.However,the special observation method makes it difficult to directly apply mature ground seismic imaging technology to the borehole seismic.In addition,due to the weak source energy of the borehole seismic,the formation absorption attenuation effect produces stronger impacts on the borehole seismic than on the ground seismic.Therefore,it is necessary to develop a targeted migration imaging method for borehole seismic.This study applied the visco-acoustic reverse-time migration imaging method to the borehole seismic and discussed the influence of various factors on the migration imaging effect of borehole seismic through model calculation,aiming to provide theoretical and technical support for the practical application of borehole seismic technology.

This study proposed the variational problem of 2.5D finite element forward modeling of the complex resistivity method and detailed the process of solving stiff matrix of finite equations. The Fractal model was introduced as a research model for studying the equivalent induced polarization anomalies of spectra. Furthermore, the complex conductivity and complex potential of a grid unit were linearly interpolated. Then, to obtain anomalous complex potential, finite element linear equations were solved using the biconjugate gradient stabilized method with incomplete LU decomposition. The results of three typical geoelectric models validated the correctness and accuracy of the algorithm proposed in this study. Furthermore, this study analyzed the abnormal response characteristics of 2.5D complex resistivity under different frequencies.

Due to the strong attenuation effect of loess cover on seismic and electromagnetic waves, the successful application of seismic reflection wave method and electromagnetic wave method in loess covered area is limited.In view of the characteristics of large thickness and fine stratification of loess cover, the active source and passive source surface wave methods are combined in this paper, so that the advantages of the two surface wave methods are complementary and the geological stratification of loess covered area can be accurately detected.The study area is located in the suburb of Fengxiang County,Weihe Basin.It is a typical loess covered area, and the thickness of loess cover is 80~120 m.By processing the measured data of active and passive surface waves in the study area, the positions of the main strata on the 2D shear wave velocity profile are basically consistent with the actual borehole test results, and the 3D stratum structure in the study area is also obtained.The results of joint imaging show that it is feasible and effective to use passive and active surface wave joint exploration for stratification of loess covered area, which provides technical support and beneficial idea for geological mapping of loess covered area.

Turbidite reservoirs have always been an important exploration type in the Jiyang depression.After years of exploration and development,the turbidites are mainly of the heterogeneous isomorphic type.The sandstone reservoirs of this type of turbidites have similar velocity,density,and seismic waveforms to those of non-reservoirs and thus are difficult to identify using conventional seismic attributes and poststack impedance.Therefore,a reservoir description method based on prestack multi-parameter sensitivity factor fusion was established.This method mainly included three steps.Firstly,major factors affecting the accuracy of shear wave estimation were analyzed,and then the multi-mineral-component shear wave prediction technology based on a modified xu-white model was established to improve the accuracy of shear wave prediction and lay a foundation for the accurate prediction of elastic parameters. Secondly,a quantitative evaluation method of sensitivity factors was proposed based on reflection coefficient ratios to obtain three sensitive elastic parameters,namely Murho,Lambrho,and POIS.The fusion index F of sensitivity factors was constructed by using the three elastic parameters.The purpose is to reduce the strong multiplicity of solutions of a single parameter and accurately identify rock properties.Thirdly,the prestack inversion technology was used for the inversion of sensitive elastic parameters.The three sensitivity parameters of sandstone information were fused using the fusion model of the RGB primary color information to realize a fine-scale prediction of lithology.This method was applied to the exploration of a deep-water turbidite reservoir around well-Tuo-71 in the Jiyang depression.The distribution of deep-water turbidite fan reservoirs in the study area was accurately predicted.The coincidence degree between the prediction results and the actual drilling reached 85%,indicating the improved accuracy of reservoir identification and description.The results of this study have contributed to an interpreted favorable sand body area of 9.5 km² and the deployment of more than 10 exploration and development wells.Among these wells,five have yielded industrial oil flow after competition and being put into operation,and their new production capacity is expected to be 2×10⁴ t。

With the advantages of flexible configuration,convenience,high efficiency,and resolution,the single-channel seismic detection technology has been widely used in marine geological surveys and offshore engineering geophysical prospecting.However,there are few cases of the application of this technology in inland rivers and lakes.Therefore,an experimental study on the high-resolution single-channel seismic detection technology targeting the inland shallow waters of Baiyangdian Lake,Xiongan New Area,Hebei Province was conducted.The application effects using key acquisition parameters,including excitation energy,excitation interval,sailing speed,and the number of receiving units,were compared to determine the optimal parameter combination.A set of single-channel seismic data processing processes and methods for inland shallow waters were developed to gradually attenuate all kinds of noises and improve the signal-to-noise ratio and resolution to the greatest extent.The experimental results show that the single-channel seismic detection technology for inland shallow waters can finely divide the shallow stratigraphic structure in the waters.Moreover,the division effects agree well with drilling data.Therefore,this technology can effectively support the investigations of environment,geology,and geologic hazards in inland rivers and lakes.

Denoising is an important part of magnetotelluric data processing. To enrich and develop the denoising method of magnetotelluric time series, this study introduced the LSTM network-one of the recurrent neural networks-into the square wave noise processing of the magnetotelluric time series. Different from previous studies, the measured magnetotelluric time series without human interference superimposed on simulated square wave noise were used as the input of the LSTM network, and the noise-free original time series were used as the target output of the network. After training for 1,500 epochs, the normalized cross-correlation coefficient between the time series extracted from the simulated noise signals by the network and the original time series reached 0.9718, indicating that the network has effectively learned the characteristics of the noise-free magnetotelluric time series. Finally, the denoising test results of measured square wave noise signals show that the proposed method can effectively suppress the interference of square wave noise and improve the estimation quality of impedance. This study provides a new idea for the processing of magnetotelluric time series based on deep learning.

In the shallow or mine prospecting using the transient electromagnetic method (TEM), the transmitting magnetic moment is limited by the limited supply voltage of the transmitting system, and the stray inductance of the transmitter loop causes a long turn-off time. To solve these problems, this study designed a parallel transmitter loop of ultra-small coils used in TEM. Using these coils, the transmitting magnetic moment can be increased by the parallel connection of the coils, and the turn-off time can be reduced by additional resistance. The equivalent circuit models of the conventional transmitter coils and the parallel transmitter coils were established and analyzed theoretically. Moreover, the comparative test between the parallel transmitter coils and the conventional transmitter coils were carried out. The results show that the parallel transmitter coils can effectively increase the magnetic moment and reduce the turn-off time. Therefore, this design is greatly significant for reducing the blind area and increasing the prospecting depth in shallow or mine prospecting using TEM.

Deeply concealed iron ores cause relatively weak geophysical anomalies on the ground surface in the Qihe-Yucheng area, Shandong Province, a typical thickly covered area. Therefore, it is the key to the ore prospecting in this area to extract local weak anomalies caused by iron ores. Autocorrelation filtering can extract local weak anomalies by reducing the influence of a regional field using a high-pass filter of a certain wavelenth. The steps of the method are as follows. First, establish a model of incline plutons generating background field and models of iron ores of different scales and depths. Based on this, obtain the superimposed magnetic field through forward modeling. Then carry out autocorrelation filtering processing of the superimposed magnetic field to effectively extract the weak anomalies of iron ores. The autocorrelation filtering method was used to process the measured data in the Qihe-Yucheng area and the processing results were compared to the borehole data, verifying that the autocorrelation filtering method is effective. The extraction of weak anomalies using the autocorrelation filtering method allows for the ore prospecting scope to be reduced, which can provide guidance on the determination of prospecting favorable locations and drilling verification.

Multi-scale wavelet decomposition is one of the common methods for gravity potential field separation. The biggest advantage is that it breaks through the traditional concept of dichotomy gravity anomalies and achieves the multiple decomposition of gravity anomalies. However, no systematic study has been carried out on the limitations and properties of the multi-scale wavelet decomposition. To systematically investigate the multi-scale wavelet decomposition and provide guidance for its practical application, this study, starting from the definition of multi-scale wavelet decomposition of gravity potential field based on profiles and grids, expounded three important properties such as the criterion that low-order wavelet keeps details invariant. Then, it analyzed the definition and properties of multi-scale wavelet by designing simple and complex theoretical models. Afterward, this study compared the multi-scale wavelet decomposition with the interpolation cutting method using field data. The results show that multi-scale wavelet decomposition can achieve multi-layer separation of gravity potential field and estimate the burial depths of source bodies. In addition, the multi-scale wavelet decomposition can provide some ideas for solving the limitations pointed out in this study, such as abnormal scale aliasing and difficulty with the determination of scale coefficients. The above basic research can provide a certain degree of references for the processing and interpretation of gravitational potential field data.

It is difficult to set up GPS base stations for airborne gravimetry in offshore and far seas, leading to long baselines. Given this, this study analyzed the impacts of long baselines on the precision of airborne gravimetry based on the principle of airborne gravimetry and the real measurement data. Moreover, this study comprehensively analyzed the effects of long baselines on differential positioning precision and evaluated the internal coincidence precision of airborne gravity anomaly. Compared to the precision required for airborne gravimetry, it is believed that long baselines (600-800 km) have limited and almost negligible impacts on the precision of airborne gravimetry. This study can provide technical support for further development of airborne gravimetry in offshore and far seas.

Horizon characteristics are important information in pavement detection using ground penetrating radar (GPR) data.However,current horizon picking methods based on manual work or related algorithms have problems such as strong subjectivity and heavy workload and they can only track one horizon each time.Therefore,this study proposed a multi-layer auto-tracking method based on the cosine of the instantaneous phase of GPR data.The specific steps of this method are as follows.Firstly,obtain the cosine of the instantaneous phase of GPR data through complex signal analysis.Secondly,carry out the correlation analysis of wavelet cosine matrix data and then calculate the cosine of the instantaneous phase of these data,aiming to enhance the transverse continuity of phase data along the cophase axis.Thirdly,obtain the spatial positions,amplitude,and polarity of the phase data,and automatically track the transversely continuous horizon lines under a series of constraints such as signal amplitude and cophase axis characteristics.Finally,determine the horizon data and their polarity by comparing the RMS values of the amplitude of adjacent horizon lines along the depth direction,and extract the horizon line data with continuous high amplitude by setting horizon and amplitude thresholds.Numerical simulation and field case analysis have verified the effectiveness and adaptability of the method proposed in this study.

The forward modeling of wave field response characteristics of wide-azimuth seismic data shows that the reflection coefficient has apparent azimuth anisotropy when the P-waves propagate in underground geologic bodies.It has become a research hotspot at home and abroad to make a fracture prediction using azimuth anisotropy.This study analyzed the response characteristics of the changes in seismic P-waves with azimuth using forward modeling.Based on the analytical results combined with the relationship between the anisotropy parameters of fluid-bearing fractures proposed by Bakulin et al.,this study approximately simplified the Ruger formula,deduced the equation between anisotropic parameter γ that can be used to characterize fracture development and reflection coefficient,and proposed a fracture prediction method based on anisotropic parameter inversion.The validity and applicability of the method have been proven using theoretical models and practical data application.Therefore,this study provides a feasible method and technology for fracture prediction using wide-azimuth prestack seismic data.

To reduce the ill-posedness of seismic full waveform inversion,a common method is to introduce prior information to regularize the inversion problem.Traditional regularization methods still face challenges even when they contain multiple prior information.This study proposed an extended full waveform inversion formula,which includes the convex set constraints on models.Specifically,this study showed how to constrain the total variation of the slowness square while forcing the constraint to keep it within a physical reality range.To verify the applicability of the algorithm proposed in this study,numerical experiments on simple models and international standard geological models were carried out.The results show that the introduction of total variation regularization can improve the reconstruction of high-speed disturbances under smooth background models.

The deep parts of complex prospecting areas such as piedmont zones and ultra-deep strata are usually accompanied by anhydrite-bearing rocks,leading to great challenges to velocity modeling and affecting the final imaging quality and reliability.It is difficult for the conventional grid tomography method to adapt to the severe lateral velocity changes of special geological bodies.To this end,this study introduced a local tomographic velocity modeling method for deep anhydrite-bearing rocks.By constructing a new tomographic objective function for velocity anomalies,the local remaining residuals below the rocks were converted into the velocity update amount of the special lithologic bodies through tomography in order to further improve the accuracy of the velocity model and effectively improve the quality of imaging below the rocks.The actual data processing results have verified the effectiveness of the local tomography method,which will provide effective technical support for oil and gas prospecting in complex prospecting areas.

This study selected the Jinsha Lake and the Miersi Industry Park as key survey areas to study the distribution of heavy metals in soil in Hong’an County, Hubei Province. Samples were collected from surface soil and vertical soil profiles to assay the contents of eight heavy metals, i.e., Cu, Pb, Zn, Cr, Ni, Cd, As, and Hg. Both the single factor pollution index method and the potential ecological hazard index method were used to assess the distribution and the ecological risk of heavy metals. The study results are as follows:The average contents of the above eight heavy metals were 21.48×10^-6, 21.75×10^-6, 63.60×10^-6, 53.24×10^-6, 20.25×10^-6, 0.13×10^-6, 5.44×10^-6, and 0.04×10^-6,respectively. The cumulative Cu, Cr, Ni, and Cd are relatively enriched in the soil and their pollution is slight. The heavy metals show distinct distribution patterns. Minor pollution exists in the Gaoqiao-Yongjiahe basic-ultrabasic melange zone and around the Miershi Industrial Park, while severe pollution exists in Mn-Co mineralized points scattered in the northeastern Baliwan. Pb and Hg are enriched in the surface layer but decrease in the deep layer, Cr and Ni show an inverse trend, while other elements show indistinct distribution patterns. Cd and Hg have high potential ecological risk individually in the soil in the surveyed areas. The comprehensive ecological risk assessment based on Cd and Hg shows that the surrounding area of the Jinsha Lake Chengguan Town, the basic-ultrabasic melange zone, the surrounding area of the Miersi Industrial Park, and the Baliwan manganese-cobalt mineralization zone are areas with moderate potential ecological risks, where ecological supervision and protection should be strengthened. This study can provide a scientific basis for later ecological management in Hongan. It also serves as a good soil reference for other ecological geological surveys.

Based on the data derived from the geochemical survey of land quality in the Guyuan region, Ningxia, this study studied the background values of 30 elements (indicators) in the surface soil using mathematical statistics. This study compared the distribution and enrichment (or dilution) characteristics of elements in different parent materials (parent rocks) and land use types and further analyzed the factors restricting the distribution of the elements from the perspective of element association characteristics using the principal component analysis method. The results show that the contents of iron-philic element Ni, tungsten-philic element Mo, alkaline (earth) metal elements Na₂O, MgO, CaO, halogen elements I, F, and copper-philic element As were all higher than corresponding national background values, while the contents of the biophilic elements such as Hg, Se, organic matter, N, and Pb were lower than corresponding national background values. Parent materials (parent rocks) were the main factor controlling the characteristics of element contents in soil. In the process of soil formation, natural and man-made influences have caused the enrichment or dilution of some elements. N, Mo, I, organic matter, and S are significantly controlled by the laterite parent material and their parent rocks, and the erosion of Ca²⁺ and Na⁺ causes weathering and leaching due to hydrodynamic effects. The element contents in the soil in the river valley plain were between those of laterite and those of loess parent material. In a supergene environment, Na₂O, K₂O, and Cl, which are prone to dissolve in water, are rich in estuaries and valleys due to hydrodynamic action. P, Hg, Se, and Mo elements are locally rich due to human interference. The factor analysis shows that parent materials (parent rocks), weathering, leaching, and bioaccumulation in the process of soil formation, and human production activities all affect the background values of the surface soil in the study area. The study results will provide basic geochemical information for the assessment of the regional resources and environment.

Taking high-density sampling data as a dataset, the sampling spatial distribution scenarios on different scales were simulated through resampling analysis. Spatial analysis methods, such as Moran's I index, semi-variance function value, and fractal dimension FD, were used to explore the scale effects of spatial variations in soil organic matter (SOM) and soil total nitrogen (STN) and to analyze the conversion of influencing factors between different scales. The results are as follows. With an increase in scale, the spatial agglomeration decreased, and the spatial variation of SOM and STN in general increased first and then tended to be stable. By contrast, the random variation decreased gradually and the structural variation increased first and then decreased as the scales increased. The spatial variation generated on small scales consisted of a large proportion of random variation and a small proportion of structural variation, while the opposite is true on large scales. Different influencing factors had different distinguishing degrees for the spatial variations in SOM and STN. Their distinguishing degrees were in the order of height<factors such as soil type, vegetation index, annual average temperature, and humidity<precipitation. The influencing factors of the spatial variations in SOM and STN had scale effects. Specifically, with an increase in scale, the random variation caused by small-scale factors decreased gradually, while the structural variation caused by large-scale factors increased first and then weakened until the large-scale factors were transformed into relatively small-scale factors. The coordination mechanism of the effects of each factor on the SOM and STN contents was quite different between different scales, causing the random and structural variations to fluctuate between different scales. As a result, the spatial variations showed the law of decreasing first and then tending to stabilize.

This study aims to investigate the characteristics, pollution sources, and ecological risks of heavy metals in the stream sediments in Heze City, which is an important catchment area in the east route of the South-to-North Water Diversion Project. To this end, stream sediment samples were collected from 25 sites of three major river basins in Heze City, and the contents of Cu, Zn, Ni, Cr, Cd, and Pb in the samples were analyzed. Moreover, this study assessed the ecological risks of these heavy metal elements using the pollution load index (PLI), potential ecological risk index (RI), and logarithmic regression model and determined the pollution sources of these heavy metal elements through correlation and principal component analysis. The results are as follows. The contents of the six heavy metal elements in the stream sediment samples were generally higher than their background values. The Ni and Cd contents at all investigated sites exceeded their background values, especially the Cd content at 40% of the investigated sites, which was more than three times the background value. The heavy metals in the stream sediments of the three river basins are unevenly distributed. The maximum values of the six heavy metals all originated from the samples of the Zhuzhaoxin River basin, of which the PLI, RI, and toxicity ratio Y were 1.67, 123 and 0.367, respectively. These values were higher than those of the other two basins, indicating that the heavy metals in sediments of the Zhuzhaoxin River basin reach moderate pollution and have high ecological risks and potential harm to aquatic organisms. The principal component analysis shows that the petroleum refining and related chemical enterprises in industrial parks are the main contributors to the enrichment of the six heavy metal elements.

A total of 13 surface sediment samples were collected from estuaries of the Maoling, Dalan, and Qinjiang rivers for heavy metal analysis, aiming to study the distribution characteristics and ecological risk of heavy metals in the surface sediments of the Maowei Sea estuary. The results are as follows. The average contents of heavy metals As, Cd, Cr, Cu, Hg, Pb, and Zn in Maowei Sea sediments were 7.78×10^-6, 0.14×10^-6, 37.6×10^-6, 18.9×10^-6, 0.0048×10^-6, 22.5×10^-6, and 54.7×10^-6, respectively. They are all lower than the class-I standard specified in GB18668—2002. The heavy metals in the sediments show quite different spatial distribution, with high content of heavy metals concentrating in the industrial zone to the east of the Maowei Sea and near the Maoling River to the west of the Maowei Sea. The analysis of heavy metal pollution shows that most elements are at levels of no pollution to moderate pollution, and Cr is at a medium pollution level. As indicated by the ecological risk analysis, the heavy metals generally show potentially low potential risks, and Hg and Cd in the industrial zone to the east show moderate ecological risks. The sources of heavy metal pollutants were explored through correlation analysis, cluster analysis, and principal component analysis. The results show that heavy metal pollution is mainly controlled by rivers, and Hg, As and Cd are also affected by wastewater discharged from the port industrial zone. This comprehensive study shows that the Maowei Sea has a good ecological environment overall, but it is recommended to focus on the drainage of heavy metal pollution in the industrial zone to the west of the Maowei Sea.