To explore the intricate interrelationship between groundwater microbial communities and hydrochemical characteristics in the Mancheng District, Baoding City, samples from karst groundwater and porous groundwater were collected. Hydrochemical analysis and the 16s RNA gene V4-V5 region sequencing method were used to detail the water environmental characteristics and microbial community distribution pattern in the study area. The hydrochemical results reveal notable differences in major ion contents and other hydrochemical indices between karst water and porous water. Microbial community analysis demonstrates that Proteobacteria, Actinobacteria, and Firmicutes are the dominant taxa in both types of water bodies, albeit with significant variations in their proportions across distinct water bodies. The observed disparities in microbial communities between karst water and porous water underscore the influence of environmental factors such as ion concentration and pH on microbial distribution. Redundancy Analysis (RDA) indicates notable associations between microbial community composition and environmental factors in both types of groundwater environments. Studying the distribution pattern of microbial communities and the connection with environmental factors in two types of groundwater lays a crucial foundation for interpreting the functional roles of microbes in groundwater ecosystems.

Strontium (Sr) is one of the essential trace elements in the human body, which has important biological significance for human physiological function. In this paper, 41 groundwater samples collected from Shengli Farm in the eastern Sanjiang Plain were used to study the hydrochemical characteristics of Sr ²⁺ enrichment and its control factors by correlation analysis, principal component analysis, and Gibbs model, which is helpful to guide the rational development and utilization of local groundwater resources and ecological environment protection.The findings indicate that the groundwater exists in a reducing environment characterized by acidity and low salinity, with predominant cations being Ca ²⁺ and Mg ²⁺ , and predominant anions being HCO ₃ ⁻ . The predominant hydrochemical type is HCO ₃ ‐Ca·Mg, secondly by SO ₄ ·Cl‐Ca·Mg type. Principal component analysis identifies three primary elements influencing the evolution of groundwater quality. The weathering and dissolution of silicate and carbonate rocks are the primary forces influencing the chemical composition of water, secondly by the dissolution of evaporites. Groundwater with a Sr content over 0.40 mg/L constituted 7.32% of the total samples. The siliceous rocks and basalts present in this region supply the foundational material for Sr ²⁺ enrichment. Sr ²⁺ is correlated and coenriched with Ca ²⁺ and Mg ²⁺ , and the liberation of Sr ²⁺ from adjacent rock during cation exchange is one of the sources of Sr ²⁺ in groundwater. Regular agricultural and livestock practices are the primary contributors to the elevation of SO ₄ ^2- levels in adjacent groundwater, as well as the enhancement of Sr ²⁺ concentrations.

To explore the interrelationship between groundwater microbial communities and hydrochemical characteristics in Mancheng district, Baoding city, samples from karst groundwater and porous groundwater were collected respectively. The hydrochemical analysis and 16s RNA gene V4-V5 region sequencing method were used to detail the water environmental characteristics and microbial community distribution pattern in the study area. The hydrochemical results reveal significant differences in major ion contents and other hydrochemical indices between karst water and porous water. Microbial community analysis demonstrates that Proteobacteria, Actinobacteria, and Firmicutes are the dominant taxa in both types of water bodies, but their proportions vary significantly in different water bodies. The difference in microbial communities between karst water and porous water reflects the influence of environmental factors such as ion concentration and pH on microbial distribution. Redundancy analysis (RDA) indicates significant associations between microbial community composition and environmental factors in both types of groundwater environments. Studying the distribution pattern of microbial communities and the connection with environmental factors in two types of groundwater provides important basis for interpreting the functional roles of microbes in groundwater ecosystems.

Introduction: As a new type of clean energy strongly supported by the state, the efficient development of hot dry rock (HDR) relies on hydraulic fracturing technology to create an effective reservoir fracture network. However, the dynamic propagation of fractures and fluid migration during the fracturing process are difficult to observe directly. The Time-Frequency Electromagnetic (TFEM) method, as an artificial source electromagnetic technique with high excitation energy, high precision, broad frequency band, and strong anti-interference capability, provides a powerful geophysical means for real-time monitoring of the fracturing process. This is based on the significant resistivity contrast between the fracturing fluid and the HDR rock mass (e.g., granite).Method: This study applied the TFEM method to monitor HDR fracturing. The monitoring network was deployed along the direction of the principal crustal stress (i.e., the main direction of fracturing stimulation and the most probable direction of fracture development) to maximize the capture of resistivity change signals induced by fluid injection. After field data acquisition, the raw data and corresponding source data were processed through organization and validation, followed by Fourier transform. Subsequent processing steps included current normalization, editing, filtering, etc. Finally, amplitude anomalies were extracted from the frequencies showing the highest anomalous response to characterize the relative changes in subsurface resistivity.Results: The basement of the study area consists of high-resistivity granite (buried at approximately 1500 m depth, resistivity 2000~100,000 Ω·m), overlain by medium-to-low resistivity sedimentary strata. The target HDR stimulation depth was 3500-4000 m. Through continuous monitoring of the entire fracturing cycle (including multiple stages such as test fracturing, high-pressure stimulation, stable high-pressure stimulation, pressure-maintained sustained stimulation, pressure-maintained flowback, and enhanced stimulation), amplitude anomaly maps for each stage were obtained (Figure 1a-f). The monitoring results indicate that the resistivity decrease caused by fracturing is clearly reflected in the amplitude anomalies of the surface-collected data. The anomaly maps can intuitively display the spatial distribution of fluid migration and accumulation during different fracturing stages and effectively indicate the preferential migration pathways of the fluid.Figure1 Plan View of Abnormal Amplitude of Fracturing Monitoring in Each StageDiscussion and Conclusion: This case study demonstrates that the TFEM method can effectively monitor the resistivity changes induced by fluid injection during HDR fracturing, successfully imaging the dynamic development of the fracture network and fluid migration pathways. This method highlights the advantage of utilizing the physical property differences between the rock mass and fluids to address engineering geological problems, providing crucial technical support for the real-time evaluation and optimization of HDR reservoir fracturing stimulation effectiveness.

The formation and exploitation of geothermal reservoirs in hot dry rock (HDR) primarily rely on microseismic methods, but seismic techniques lack sufficient sensitivity to fluids. The electromagnetic method, however, demonstrates sensitivity to fluid movements during the monitoring of fracturing processes that form geothermal reservoirs in HDR. This study examines the role of electromagnetic methods in HDR development, taking China’s first Enhanced Geothermal System (EGS) demonstration site in the Qinghai Gonghe Basin as a case study. Based on the Gonghe HDR development site, a frequency-domain 3D borehole-to-surface electromagnetic forward modeling method with unstructured-grid discretization was employed to simulate the complex electromagnetic field responses induced by fracturing fluid injection and dynamic changes in fractures during HDR reservoir development. To enhance computational efficiency, a supercomputer was employed to perform 3D borehole-to-surface electromagnetic data inversion under conditions of massive multi-source and multi-frequency data. This quantitatively revealed the electrical characteristics at different depth intervals within the study area. The research demonstrates the feasibility of borehole-to-surface electromagnetic methods for determining the spatial distribution of fracturing injection, dynamically monitoring fracture development, and tracking fluid migration, thereby providing crucial technical support for monitoring HDR resources development.