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Reservoir immersion will lead to some environmental geological problems, such as soil swamping or salinization, reduction of building foundation strength, or even overall instability. Reservoir scope of immersion is closely related to changes in groundwater levels. According to the geological and hydrogeological conditions pertaining in the Jiangxiang reservoir area, the analytical method is employed to calculate the change in groundwater levels in an unconfined aquifer when the reservoir water level rises rapidly to a constant value and changes periodically. Combined with the related functions of MATLAB™ software, the lag and immersion times are determined in different locations around the reservoir. The results show that the change of the groundwater level exhibits hysteresis relative to that of the reservoir water level owing to the low permeability of silty loam and clay. The closer to the reservoir, the faster the groundwater level rises or falls. In the Guo Xiaoxu section, when the reservoir water level rises rapidly to 42.5 m, the groundwater level near the reservoir remains lower than the reservoir water level after 50 years. If the hydraulic conductivity is increased by three orders of magnitude, the groundwater level and the reservoir water level changes are positively correlated, and the hysteresis is not obvious. In the crop areas, the scope of immersion in the Guoxiaowei section is 31 m with the immersion elevation of 43.23 m, and the corresponding immersion time is 15,766 d. In residential areas, the scope of immersion of the Qigang section is 308 m with the immersion elevation of 46.78 m, and the corresponding immersion time is 16,354 d. The calculated scope of immersion and time at different locations provide a scientific basis for the design of the reservoir water level and the range of demolition affecting local residents.

Seasonal climate variations (SCV) have a significant impact on the exchange of surface and groundwater in the reservoir area. As a crucial climatic element, temperature also has an important effect on the hydrological cycle. In the plain reservoir area, the hysteresis response of groundwater in the aquitard to reservoir level (RL) fluctuations is ever-present. To study the impacts of SCV on the hysteresis response of groundwater in the aquitard, the response of groundwater level (GL) of Jiangxiang Reservoir to the variation of the RL was examined. Considering the seasonal temperature variations (STV), the hydraulic diffusivity of the aquitard was calculated. Relying on the STV, the formula for calculating the variation of the GL with the RL was derived. The results showed that the hydraulic diffusivity is sensitive to temperature changes. The higher the temperature, the greater the hydraulic diffusivity, which results in a faster response of groundwater to changes in reservoir level. Additionally, the lag of groundwater level change in the aquitard became smaller. Considering STV, the calculated immersion scope with variable parameters was smaller than that with constant parameters.

The migration of groundwater flow and contaminants in fractured medium is complicated owing to the strong heterogeneity and anisotropy of fractured rock mass. Taking the environmental restoration and groundwater protection of the Lishui domestic waste landfill in Nanjing as the background, the groundwater environmental impact assessment and prediction are conducted for the groundwater environmental pollution that may be caused by the leakage of the landfill leachate after the closure of the domestic waste landfill. The strata of the landfill site are clay-cobble gravel, strongly and moderately weathered breccia, with obvious anisotropy and significant differences in rock mass permeability. A 3D numerical model of groundwater flow and contaminant migration in the landfill area is established by integrating the hydrogeological field tests and a conceptual model in the study area. Based on the parametric inversion method, the heterogeneous anisotropic permeability coefficient of the fractured medium is calibrated, and the temporal and spatial migration characteristics of contaminants such as ammonia nitrogen and mercury are predicted using the corrected model under the normal and failure conditions of the antiseepage curtain. The calculated results show that when the antiseepage fails, the maximum migration distances of contaminants in the horizontal direction after 100 days in the old and new landfills are 7.66 m and 15.64 m, respectively, and the maximum migration distances after 20 years are 192.5 m and 113.89 m, respectively. The migration direction and distances of contaminants are consistent with the hydrogeological conditions of the study area. The model calculation results provide a corresponding basis for the antiseepage control of contaminants.

Based on the hidden karst exposed in Jurong Pumped Storage Power Station, combined with the field exploration data, the temporal and spatial development characteristics of hidden karst in the power station area are analyzed using the methods of specific solubility and specific corrosion, water chemical composition analysis, borehole television imaging, tracer test, and water pressure test. The results show that the karst development in the study area can be divided into three periods: pre-Cretaceous, Pleistocene, and modern karst. Karst development is controlled by soluble rock, non-soluble rock, and their combination, and the development direction is basically consistent with the fault strike. Karst caves are mainly distributed below the elevation of 100 m, with different shapes and scales and randomness. Non-soluble rocks and impure carbonate rocks are widely distributed in the study area, and surface karst is not developed. The underground karst caves are filled with red clay, and the rate of groundwater circulation is slow. The existence of geological bodies such as rock veins causes the groundwater levels to have obvious double-layer characteristics, which results in weak connectivity between karst caves. Although the karst in the power station area has a certain hydraulic connection with the surface water outside the area, the hydraulic connection of karst in the power station area is generally weak. The research results provide a scientific basis for the anti-seepage measures of underground powerhouses.

Based on the geological and hydrogeological conditions of the Jurong Pumped Storage Hydroelectric Power Station (JPSHP), a 3D groundwater flow model was developed in the power station area, which took into account the heterogeneity and anisotropy of fractured rocks. A control inversion method for fractured rock structural planes was proposed, where larger-scale fractures were used as water-conducting media and the relatively intact rock matrix was used as water-storage media. A statistical method was used to obtain the geometric parameter values of the structural planes, so as to obtain the hydraulic conductivity tensor of the fractured rocks. Combining the impermeable drainage systems of the upper storage reservoir, underground powerhouse and lower storage reservoir, the 3D groundwater seepage field in the study area was predicted using the calibrated model. The leakage amounts of the upper storage reservoir, powerhouse and lower storage reservoir were 710.48 m3/d, 969.95 m3/d and 1657.55 m3/d, respectively. The leakage changes of the upper storage reservoir, powerhouse and lower storage reservoir were discussed under the partial and full failure of the anti-seepage system. The research results provide a scientific basis for the seepage control of the power station, and it is recommended to strengthen the seepage control of the upper and lower storage reservoirs and the underground powerhouse to avoid excessive leakage and affect the efficiency of the reservoir operation.

In areas with complex hydrogeological conditions, the tracer test method is often used as an effective means in hydrogeological surveys. According to the results of tracer tests, hydrogeological parameters, including hydraulic gradient and permeability coefficient, fracture network leakage passages and their scale, and groundwater flow rate and direction can be quantitatively determined. This paper takes the upper reservoir of Yongxin Pumped Storage Power Station in Jiangxi Province as the research object, and focuses on the complex hydrogeological conditions of the upper reservoir. Three sets of tracer tests and multiple sets of single-hole flow rate and direction tests were conducted on the left and right banks of the reservoir and near surface gullies. The results showed that ZKS18 received tracers in all three tests, which indicates a close hydraulic connection between ZKS18 and the left bank, right bank, and surface gullies within the reservoir. Based on the single or multiple peak values of the tracer, it was determined that there are 1–6 leakage passages in the fractured rocks, with leakage passage sizes of 0.1–0.4 mm. According to the single-hole flow rate and flow direction tests, a self-developed instrument was used to determine the groundwater flow rate and flow direction at different depths in the test holes, which yielded results that were basically consistent with the results of the three-hole method. These results provide a basis for the use of tracer tests in hydrogeological surveys for water conservancy and hydropower engineering, and anti-seepage design of upper reservoirs.

With the increasing requirement of international energy security, oil storage projects have been constructed in large numbers, but leaking petroleum-based contaminants are threatening the soil and groundwater environment. In order to assess the environmental risk of petroleum-based contaminants, an experimental apparatus was designed and developed to monitor the concentration and pressure variations of light non-aqueous phase liquid (LNAPL) in filled fractured network media. The mobilization mechanism of LNAPL was investigated by theoretical analysis and laboratory experiments; the pressure balance relationships at different interfaces were investigated. When the experimental model was unsaturated, the dynamic processes of concentration and pressure at different locations in filled fractures were explored. When the groundwater level was raised to 35 cm, the cumulative height of LNAPL ( H L ) was a function of the density of LNAPL, interfacial tension, interfacial contact angle, aperture of fracture, porosity, and particle diameter of filling and H L 21  >  H L 22 . The final concentrations of H21, H22, H25, H26, and H27 were 0.467, 0.458, 0.026, 0.062, and 0.041 mg/mL, respectively. Subsequently, the effect of the particle diameter of filling sand on LNAPL mobilization was further discussed, the concentration of each point in the fractures increased with the increase of the particle diameter of filling sand, and its peak decreased with the increase of the burial depth. The response time of pressure at each point was advanced and the peak of pressure dynamic curve increased as the particle diameter of filling sand increased. The peak pressure heads of H12 and H13 were 22.360 cm and 25.332 cm respectively when the particle diameter of filling was 0.5–1.0 mm. The Spearman analysis results between LNAPL concentration and time showed a significant correlation (≥ 0.879, α = 0.05 ). Research results characterized the existence and mobilization of LNAPL in filled fractured network media from the perspectives of concentration and pressure, which could provide a reference for the study of the leakage and migration mechanism of LNAPL.

Water electrolysis for hydrogen production has garnered significant attention due to its advantages of high efficiency, environmental friendliness, and abundant resources. Developing cost-effective, efficient, and stable materials for water electrolysis is therefore crucial. In this work, we synthesized a series of highly efficient multifunctional Mn-Co1.29Ni1.71O4 electrocatalysts through an atomic doping strategy for alkaline electrocatalysts. The unique structure features and large specific surface area of these catalysts provide abundant active sites. The Mn-Co1.29Ni1.71O4 catalysts exhibit an excellent oxygen evolution reaction (OER) performance in 1.0 M KOH electrolyte, with an overpotential of 334.3 mV at a current density of 10 mA cm−2 and 373.3 mV at 30 mA cm−2. Additionally, the catalysts also demonstrate a Tafel slope of 76.7 mV dec−1 and outstanding durability. As hydrogen evolution reaction (HER) electrocatalysts, it shows an overpotential of 203.5 mV at −10 mA cm−2 and a Tafel slope of 113.6 mV dec−1. When the catalysts can be utilized for the overall water splitting, the catalyst requires a decomposition voltage of 1.96 V at 50 mA cm−2. These results indicate that the high catalytic activity and stability of Mn-Co1.29Ni1.71O4 samples make it a highly promising candidate for industrial-scale applications.

Water electrolysis for hydrogen production has garnered significant attention due to its advantages of high efficiency, environmental friendliness, and abundant resources. Developing cost-effective, efficient, and stable materials for water electrolysis is therefore crucial. In this work, we synthesized a series of highly efficient multifunctional Mn-Co[sub.1.29]Ni[sub.1.71]O[sub.4] electrocatalysts through an atomic doping strategy for alkaline electrocatalysts. The unique structure features and large specific surface area of these catalysts provide abundant active sites. The Mn-Co[sub.1.29]Ni[sub.1.71]O[sub.4] catalysts exhibit an excellent oxygen evolution reaction (OER) performance in 1.0 M KOH electrolyte, with an overpotential of 334.3 mV at a current density of 10 mA cm[sup.−2] and 373.3 mV at 30 mA cm[sup.−2]. Additionally, the catalysts also demonstrate a Tafel slope of 76.7 mV dec[sup.−1] and outstanding durability. As hydrogen evolution reaction (HER) electrocatalysts, it shows an overpotential of 203.5 mV at −10 mA cm[sup.−2] and a Tafel slope of 113.6 mV dec[sup.−1]. When the catalysts can be utilized for the overall water splitting, the catalyst requires a decomposition voltage of 1.96 V at 50 mA cm[sup.−2]. These results indicate that the high catalytic activity and stability of Mn-Co[sub.1.29]Ni[sub.1.71]O[sub.4] samples make it a highly promising candidate for industrial-scale applications.

Water electrolysis for hydrogen production has garnered significant attention due to its advantages of high efficiency, environmental friendliness, and abundant resources. Developing cost-effective, efficient, and stable materials for water electrolysis is therefore crucial. In this work, we synthesized a series of highly efficient multifunctional Mn-Co Ni O electrocatalysts through an atomic doping strategy for alkaline electrocatalysts. The unique structure features and large specific surface area of these catalysts provide abundant active sites. The Mn-Co Ni O catalysts exhibit an excellent oxygen evolution reaction (OER) performance in 1.0 M KOH electrolyte, with an overpotential of 334.3 mV at a current density of 10 mA cm and 373.3 mV at 30 mA cm . Additionally, the catalysts also demonstrate a Tafel slope of 76.7 mV dec and outstanding durability. As hydrogen evolution reaction (HER) electrocatalysts, it shows an overpotential of 203.5 mV at -10 mA cm and a Tafel slope of 113.6 mV dec . When the catalysts can be utilized for the overall water splitting, the catalyst requires a decomposition voltage of 1.96 V at 50 mA cm . These results indicate that the high catalytic activity and stability of Mn-Co Ni O samples make it a highly promising candidate for industrial-scale applications.