Search

Under the context of low-carbon travel, promoting the green and environmentally friendly upgrade of urban transportation and optimizing urban transportation structures are of great significance in reducing carbon emissions. Exploring the pathways and methods to achieve green and low-carbon goals in urban transportation is a key research objective. Accordingly, this study constructs a multi-objective optimization model to optimize the transportation structure of Lanzhou City and quantitatively verifies the optimization effects through carbon emission calculations and coordination evaluations. The results indicate that (1) optimizing urban transportation structures can reduce energy consumption and emission levels but cannot achieve the “carbon peaking” goal; (2) developing urban rail transit has a significant positive impact on energy saving and emission reduction; (3) the development of green transportation is closely integrated with and mutually influenced by slow-moving transportation, showing both synergy and constraints; and (4) under the comprehensive restriction scenario, despite higher energy consumption and emission values, better coordination is achieved, making it the most suitable optimization plan aligned with the green transportation development concept.

Well group layout is one of the key steps of groundwater recovery with pump and treat technology. In order to improve the remediation efficiency of pump and treat technology, a pollution field was taken as the research area, and a nonlinear-dynamic-multi-objective simulation-optimization model was established. The minimum capital cost, maximum pollutant removal rate and shortest remediation time were taken as the optimization objectives, and different extraction flows under single, double and three-well modes were set. The weighted optimization method is used to compare the well group layout scheme. The results show that: Overall, the single-well mode has poor remediation efficiency, when focusing on capital cost, the double-well pumping scheme is better overall, when focusing on the standard time, the mitsui-well pumping scheme is better overall; the single-well mode with constant flow is better than the multi-well modes, if the pumping flow is reduced appropriately in the late stage of the multi-well modes, the total amount of water pumped can be reduced and the capital cost can be saved, the dynamic management of well groups can improve the remediation efficiency. This study provides a reference for the application of weighted optimization method combined with numerical simulation method in well group layout optimization of pump and treat technology, and verifies the flexibility and practicability of weighted optimization method in well group optimization application.

Objective The Gudui-Nanliang spring basin located in southern Shanxi Province is a complex karst water system with the coexistence of deep and shallow circulation, the transformation of cold and hot water, and multistage discharge. Due to long-term unreasonable exploitation and utilization, a series of geological environment problems related to karst groundwater have emerged in the spring basin. The present study aims to propose an ecological restoration and planning scheme for the spring basin by discussing in detail the status of karst groundwater-related environmental problems and their causes. Methods Based on a hydrogeological survey, this paper comprehensively employs a variety of methods, including comparative analysis of groundwater flow field, hydrogeochemical and isotopic analysis, and evaluation of karst water resources. Results The results show that due to the superimposed effects of climate change and human activities, Gudui Spring, Nanliang spring, and Haitou spring cut off the flow in 1999, 1992, and 2002, respectively, and the average decline rate of the regional groundwater level from 2013 to 2021 reaches 2.53 m/a. The results of hydrochemical and isotopic analysis indicate that the recharge to the karst groundwater of porous groundwater from unconsolidated deposits through leakage and surface water from Sanquan Reservoir through seepage cannot be ignored. The proportion of karst water samples worse than the water quality standard of class Ⅲ in the spring basin increased from 62.5% in 2014 to 81.25% in 2021. The range of 0.904 km2 of the spring source area can be subdivided into core protection zone, general protection zone and reservoir storage zone. Ecological protection and restoration planning should be carried out considering the differences between the three zones. Conclusion The results of the study can provide a basis for the comprehensive management of groundwater overexploitation areas in Shanxi Province and the ecological restoration and protection of Gudui spring basin.

Study region: As part of the active Xianshuihe Fault system, the Kangding geothermal field is a representative high-temperature hydrothermal system in the southeastern Tibetan Plateau, China. The strong tectonic and hydrothermal activity serves as a unique location to study the interaction between earthquakes and geothermal fluids. Study focus: We have collected water samples taken from thermal springs and boreholes in the geothermal field to identify fluid composition and reservoir temperature of the deep granite and shallow metamorphic rock using geochemical analysis and the Integrated Multicomponent Geothermometry (IMG) method. Two typical thermal springs that offer long-term hydrochemical data were selected to investigate the effect of earthquakes on the shallow and deep reservoir temperatures. New hydrological insights for the region: The deep reservoir temperature in the Kangding geothermal field is in the range 222 ℃ to 256 ℃, while the shallow reservoir temperature ranges from 128 ℃ to 171 ℃. Both thermal springs show changes in reservoir temperature following the 2008 Wenchuan, the 2013 Lushan, and the 2014 Kangding earthquakes. The temperature changes are similar in the deep reservoir of the two springs but different in the case of the shallow reservoir. We propose that the changes in reservoir temperature, steam fraction, and dilution factor indicate that the deep reservoir is more sensitive to earthquake-induced permeability changes than the shallow reservoir.

Significance As a tectonic phenomenon with important hydrogeological significance, fault zones mostly show a significant impact on groundwater migration. Progress It is important to include fault zones in water resource management and evaluation. This paper focuses on the permeability of the fault zone, the quantitative characterization and the evolution of the hydraulic characteristics of the fault zone, the dynamic evolution of the hydraulic characteristics of fault zones and the simulation of groundwater flow in the fault zone. The permeability of the fault zone is the key to the current study, and different permeability characterization methods have different representative scales. The permeability of the fault zone has complex spatiotemporal distribution characteristics, which challenges the description of groundwater migration in the fault zone. The selection of appropriate numerical simulation methods is an important way to quantitatively describe the groundwater movement in the fault zone and verify the suitability of the other methods. How to consider the complexity of the hydraulic characteristics of the fault zone at the spatiotemporal scale in the simulation process is the premise of accurately characterizing the groundwater flow in the fault zone. Conclusions and Prospects We suggest that a special hydrogeological observation base for the fault zone is the key to further improve the level of fault zone groundwater study, and data from geological, hydrogeological, heat flow, geophysical and remote sensing should be integrated, and interdisciplinary cooperation should be strengthened.

Objective In order to understand groundwater systems, it is useful to study the changing characteristics and mechanisms of hydrogeological parameters with time. Responses of groundwater level microfluctuations to natural periodic loadings, such as earth tides and barometric pressure, serve as low-cost and effective investigation technique to calculate aquifer hydrogeological parameters. Methods In this paper, we systematically reviewed theoretical methods of hydrogeological parameters estimation based on groundwater level response to earth tides, barometric pressure, and their combination. We presented earthquake-related and mining-related parameters change with time in well-aquifer system. The barometric pressure response method also applies to the assessment of aquifer vulnerability. Results We conclude that studying the microfluctuation of groundwater level may provide insight into the interaction among hydrogeological processes, tectonic activities, and artificial influences in the shallow crust at spatial and temporal scales. Conclusion This paper also proposes three scientific problems to be solved in the future: the application of skin and wellbore storage effects, the improvement of computation accuracy of hydrogeological parameters by combining multiple methods for determining basic geological parameters, and the investigation of other artificial influences such as groundwater overdraft and subsidence to regional aquifer systems.

AbstractSeveral meters of rise in groundwater level with significant changes in groundwater temperature were observed near the epicenter of the 1976 Tangshan earthquake—an intraplate earthquake with a magnitude of MS=7.8 that occurred in northern China. The origin of the groundwater level rise, however, remains a mystery. Studying the groundwater level rise can provide insight into the faulting process and has implications for water resources. In this study, we analyze the indications of the groundwater temperature data on the characteristics of the rising groundwater. The results show that the upward flow was maintained for approximately 5 days, and the depth of the rising groundwater was about 1–2 km. We then examine the groundwater level and temperature data with several reported models in order to explain the cause of the groundwater level rise. The results indicate that the groundwater level rise is attributable to the earthquake-induced enhancement of vertical hydraulic connection between the shallow and deep aquifers, leading to the upwelling of deep fluids that causes the groundwater levels to rise.

Groundwater quality assessment is important for understanding the suitability of groundwater resources for various purposes. Although many different methods have been proposed for this purpose, few methods have considered the spatial variation of groundwater components during the assessments. In this study, we proposed to combine the self-organizing map (SOM) and entropy-based weight determining method to assess groundwater quality. Totally, 955 water samples taken from 58 wells during 2010–2017 were used in the study. 22 hydrochemical components (K+, Na+, Ca2+, Mg2+, NH4+, Cl−, SO42-, F−, NO3−, Fe2+, Fe3+, Al, etc.) were used in the assessment for each sample. These sampling points can be classified into five clusters, which may be affected by four different sources: landfill sources (cluster 3), industrial and agricultural sources (cluster 5), and domestic sewage discharge sources (clusters 1, 2, and 4). The scores of the water quality of the five clusters that were calculated by the entropy method are 0.2658, 0.2634, 0.5737, 0.2608, and 0.5718, indicating that the groundwater affected by domestic sewage discharge sources (clusters 1, 2, and 4) are better than other two sources (clusters 3 and 5) in the study area. The results of this study provide insights for the protection of groundwater resources and the treatment of groundwater pollution in the future.

Groundwater evolution and circulation in coal mining areas will be significantly affected by natural processes and human activities. However, the impacts of large-scale mining drainage on groundwater hydrochemistry are unclear in the semi-arid and arid inland coalfields in northwest China. In particular, for shallow buried areas, the spontaneous combustion of coal seam outcrops forms burnt rock that is rich in fractures. Being a strong water-yield aquifer after receiving recharge, burnt rock has become a potential source of mine water inrush hazards. Therefore, drainage from this aquifer is necessary to eliminate potential hazards, which also leads to the deterioration of the local ecological diversity and sustainability. The hydrogeochemical method is an effective way to study the source and evolution of groundwater in mining areas and to determine the long-term cumulative effect of mining and drainage on the hydrogeochemical evolution of burnt rock areas. It is, however, still poorly understood. In this study, we employed the hydrochemical and isotope (2H, 3H, and 18O) to investigate the long-term effects of drainage on the hydrogeochemical evolution in the coalfield of southern Xinjiang, China. The results showed that the hydrochemical environment became more complex as the effect of recharge of different tritium-based groundwater ages in multiple-layered aquifer system and leads to the changes in the concentration of the chemical components. Before large-scale mining drainage, groundwater flowed from west to east and was finally discharged into the Kuqa River. The major water–rock interactions that occurred were the dissolution of halite, carbonate and gypsum dissolution, cation exchange, and dedolomitization. After large-scale and long-term mining drainage from the burnt rock aquifer, the groundwater flow field had changed, and the Kuqa river turned to recharge into the burn rock aquifer, the hydrochemical evolution also changed from water–rock interaction to mixture. This was caused by the significant decline in the groundwater level and changes in groundwater circulation in the mining area, which further led to the loss of valuable surface water resources in this arid area. Based on the characteristics and recharge conditions of burnt rock, we suggested that grouting can effectively cut off the hydraulic connection between the river and burnt rock and thus protect water resources.

We have examined the water level data from 16 wells in Sichuan province, China, recorded before the Wenchuan Ms8.0 earthquake occurred in 2008. We found that the data of 5 among these wells exhibit possible precursory anomalies, which are respectively named the Chuan No.08 well in Deyang, Chuan No.11 well in Pujiang, Chuan No.13 well in Luzhou, Chuan No.22 well in Qionglai and Beichuan. In time durations, these anomalies are of long-, intermediate- and short-term signals which are primarily distributed on the northeast (NE) trending Longmenshan fault zone as well as the parallel Huayingshan fault zone. It seems that the variations of the well levels on the Huayingshan fault zone imply compression while those on the Longmenshan fault zone reflect extension. These anomalies occurred first in the areas outside the epicenter region of the Wenchuan Ms8.0 earthquake, then migrated to the seismogenic fault zone. And they migrated from southwest to northeast in agreement with the rupture process of the main shock. Keywords: Wenchuan earthquake, Precursory anomalies, Ground water level, Temporal–spatial distribution, Sichuan province

Rock deformations induced by active faults is an important topic in earthquake studies. Such deformations are usually measured with crossfault measurements (CFM), which are time-consuming and labor-intensive. In this study, rock deformations induced by the famous Xianshuihe fault in Xialatuo of China were estimated by groundwater-level monitoring (GLM) and CFM for the period of January 1, 2016 to December 31, 2018. The pattern of the variations in areal strain estimated with GLM matches that from CFM well. The estimated strain by the GLM and CFM both changed from positive to negative with time, indicating that the fault plane switched from tensile to compressive. This indicates that the rate of rock deformation had slowed down during this period, which is consistent with the long-term creep rates obtained by CFM at the site, implying that the fault may have gradually entered the next relock state. The estimated strain changes using the GLM method lag slightly behind those of CFM, which is probably due to the diffusive effects of pore pressure propagation that is caused by the rock deformation under the crustal stress. This study demonstrates that GLM is a more convenient and efficient addition to traditional geophysical techniques and raises the possibility for the characterization of continuous rock deformations. The method may be used to obtain the changing regional strain field with a network of monitoring wells.

The determination of changes in hydrogeological properties (e.g., permeability and specific storage) of aquifers disturbed by mining activity is significant to groundwater resource and ecological environment protection in coal mine areas. However, such parameters are difficult to continuously measure in situ using conventional hydrogeological methods, and their temporal changes associated with coal mining are not well understood. The response of well water level to Earth tides provides a unique probe to determine the in situ hydrogeological parameters and their variations. In this study, the tidal responses of well water level were employed to characterize the changes in hydrogeological parameters of the overburden aquifer induced by longwall mining in a coalfield, northwest China. Based on the long-term hourly recorded water level data, two analytical models were used to determine the temporal changes of permeability and specific storage of the overburden aquifer. The results showed that the hydrogeological parameters changed with the longwall coal face advance. When the longwall coal face approached the wells, the aquifer permeability increased several to dozens of times, and the response distance ranged from 80 m to 300 m. The specific storage decreased before the coal face reached wells and recovered after the coal face passed. The results of this study indicate that the hydrogeological parameter changes induced by coal mining are related to the location of the well relative to the coal face and the stress distribution in the overburden aquifer. This study revealed the changes in permeability and specific storage associated with the mining disturbance which could have great significance for quantitative assessment of the impact of mining on overburden aquifer.

The geochemical and geothermal characteristics of hydrothermal systems in an area are useful information to appropriately evaluate the geothermal potential. In this paper, we investigated the chemical and isotopic composition of thermal water in an underexploited geothermal belt, Yidun-Litang area, in eastern Tibetan Plateau. 24 hot spring samples from the Yidun and Litang area were collected and analyzed. The water chemical types of the hot springs are mainly Na-HCO3-type water. Water-rock interaction and cation exchange and mixture are the dominant hydrogeochemical processes in the hydrothermal evolution. The significant shift of D and 18O isotopes from the GMWL indicates that these springs have undergone subsurface boiling before rising to the surface. Different ratios of Cl to other conservation species can be found for the springs in Litang and Yidun areas, suggesting the different heat sources of the two hydrothermal systems. The reservoir temperature in the Yidun area is around 230°C while the reservoir temperature in the Litang area is around 200°C. Both hydrothermal systems are recharged by the meteoric water and are heated by the different deep, thermally and topographically driven convection heat along faults and undergoing subsurface boiling before going back to the surface.

The eastern Tibetan Plateau geothermal belt is one of the important medium-high temperature geothermal belts in China. However, less work has been done on the hydrochemical characteristic and its geological origin. Understanding the chemical characteristics and the hydrochemical evolution processes is important in evaluating the geothermal energy potential in this area. In the present study, we discussed the hydrochemical properties and their origins of 39 hot springs located in the eastern Tibetan Plateau geothermal belt (Kangding-Litang-Batang geothermal belt). Cluster analysis and factor analysis are employed to character the hydrochemical properties of hot springs in different fault zones and the possible hydrochemical evolution processes of these hot springs. Our study shows that the hot springs can be divided into three groups based on their locations. The hot springs in the first group mainly originate from the volcanic rock and the springs in the second group originate from the metamorphic rock while the springs in the third group originate from the result of mixture of shallow water. Water-rock interaction, cation exchange, and the water environment are the three dominant factors that control the hydrochemical evolution process in the eastern Tibetan Plateau. These results are also in well agreement with the isotopic and chemical analysis.