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Kun Yu
Key Laboratory of Groundwater and Ecology in Arid and Semi-arid Areas, China Geological Survey, Xi'an 710054, China

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Journal article
Published: 27 April 2021 in Soil and Tillage Research
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The extraction of deep confined groundwater has been widely identified as the main factor leading to land subsidence. However, how soil pore characteristics and morphology may change as a result of land subsidence remains unclear. The objective of this study was to (1) quantify and compare the effects of soil compression due to deep confined aquifer exploitation on soil pore characteristics and morphology and (2) assess the relationships between pore parameters and saturated hydraulic conductivity (Ksat). Three kinds of lithology (clay, silt, and silty clay soils) from two 300-m engineering geological boreholes were investigated at natural saturated state (NSS) and complete drainage state (CDS). Seventeen undisturbed soil samples, 70 and 50-mm in diameter and height, respectively, were collected and subjected to steps of uniformly increasing loads in uniaxial confined compression tests to analyze pore characteristics, morphology, and Ksat. Keeping the samples in a strain-locked state, pore parameters were assessed after each loading step by using X-ray micro-computed tomography (CT; voxel resolution: 3-μm) images. A hundred CT images were acquired and quantified for each treatment in each soil sample. Soil pore characteristics and morphological parameters including number of pores, number of macropores (diameter (∅) > 1000-μm), number of coarse mesopores (∅ 200–1000-μm), number of fine mesopores (∅ < 200-μm), porosity, macroporosity, coarse mesoporosity, fine mesoporosity, largest pore area, average pore diameter, shape factor, structure model index, degree of anisotropy, and the Euler number were analyzed using ImageJ software. All parameters differed between NSS and CDS treatments, especially in silt and silty clay soils below 100-m depth, and the differences seemed to increase with increasing depth. However, parameter variations were not obvious for clay soil. Furthermore, Ksat differed significantly between treatments. The largest pore area, average pore diameter, and regular porosity accounted for 78.2 % of the change in Ksat. Thus, the decrease in proportion of elongated macropores favors land subsidence, particularly in silt and silty clay soils below 100-m depth. Efforts such as optimization of groundwater exploitation depth should be made to alleviate and control land subsidence.

ACS Style

Kun Yu; Luchen Wang; Yang Duan; Maosheng Zhang; Ying Dong; Wuhui Jia; Fusheng Hu. Soil pore characteristics, morphology, and soil hydraulic conductivity following land subsidence caused by extraction of deep confined groundwater in Xi'an, China: Quantitative analysis based on X-ray micro-computed tomography. Soil and Tillage Research 2021, 211, 105018 .

AMA Style

Kun Yu, Luchen Wang, Yang Duan, Maosheng Zhang, Ying Dong, Wuhui Jia, Fusheng Hu. Soil pore characteristics, morphology, and soil hydraulic conductivity following land subsidence caused by extraction of deep confined groundwater in Xi'an, China: Quantitative analysis based on X-ray micro-computed tomography. Soil and Tillage Research. 2021; 211 ():105018.

Chicago/Turabian Style

Kun Yu; Luchen Wang; Yang Duan; Maosheng Zhang; Ying Dong; Wuhui Jia; Fusheng Hu. 2021. "Soil pore characteristics, morphology, and soil hydraulic conductivity following land subsidence caused by extraction of deep confined groundwater in Xi'an, China: Quantitative analysis based on X-ray micro-computed tomography." Soil and Tillage Research 211, no. : 105018.

Journal article
Published: 08 February 2021 in Water
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Groundwater evapotranspiration (ETG) estimation is an important issue in semiarid areas for groundwater resources management and environmental protection. It is widely estimated by diurnal water table fluctuations. In this study, the ETG at four sites with different plants was estimated using both diurnal water table and soil moisture fluctuations in the northeastern Mu Us sandy region, in order to identify the groundwater utilization strategy by different dominant phreatophytes. Groundwater level was monitored by ventilatory pressure transducers (Solinst LevelVent, Solinst Canada Ltd.; accuracy ±3 mm), while soil moisture was monitored using EM50 loggers (Decagon Devices Inc., Pullman, USA) in K1 and K14 and simulated by Hydrus-1D in other observation wells. A significant spatial variation of ETG was found within a limited area, indicating a poor representativeness of site ETG for regional estimation. The mean values of ETG are 4.01 mm/d, 6.03 mm/d, 8.96 mm/d, and 12.26 mm/d at the Achnatherum splendens site, Carex stenophylla site, Salix psammophila site and Populus alba site, respectively, for the whole growing season. ETG is more sensitive to depth to water table (DWT) in the Carex stenophylla site than in the Achnatherum splendens site for grass-dominated areas and more sensitive to DWT in the Populus alba site than in Salix psammophila site for tree-dominated areas. Groundwater extinction depths are estimated at 4.1 m, 2.4 m, 7.1 m, and 2.9 m in the Achnatherum splendens site, Carex stenophylla site, Salix psammophila site and Populus alba site, respectively.

ACS Style

Wuhui Jia; Lihe Yin; Maosheng Zhang; Kun Yu; Luchen Wang; Fusheng Hu. Estimation of Groundwater Evapotranspiration of Different Dominant Phreatophytes in the Mu Us Sandy Region. Water 2021, 13, 440 .

AMA Style

Wuhui Jia, Lihe Yin, Maosheng Zhang, Kun Yu, Luchen Wang, Fusheng Hu. Estimation of Groundwater Evapotranspiration of Different Dominant Phreatophytes in the Mu Us Sandy Region. Water. 2021; 13 (4):440.

Chicago/Turabian Style

Wuhui Jia; Lihe Yin; Maosheng Zhang; Kun Yu; Luchen Wang; Fusheng Hu. 2021. "Estimation of Groundwater Evapotranspiration of Different Dominant Phreatophytes in the Mu Us Sandy Region." Water 13, no. 4: 440.

Journal article
Published: 19 December 2019 in Journal of Soils and Sediments
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Land subsidence has caused serious geological damage in many countries, including China. Soil pore number, size, shape, and pore size distribution affect soil deformation and thus land subsidence. Quantification of complex pore structures in different soil types and at various soil depths, however, remains cumbersome. The objective of this study was to quantify pore characteristics of three different soil types using computed tomography (CT) technique, investigate the effects of soil depth, examine the relationships between various parameters, and preliminarily determine the pore deformation pattern. Undisturbed soil samples (70 mm diameter × 50 mm height) of clay, silt, and silty clay soils were collected from two 300-m-deep engineering geological boreholes on both sides of the Xi’an D7 ground fissure. One hundred CT images were acquired for each soil sample. Soil pore characteristics and morphological parameters, including porosity, macroporosity, coarse mesoporosity, microporosity, number of pores, number of macropores (diameter > 1000 μm), number of coarse mesopores (diameter 200–1000 μm), number of micropores (diameter < 200 μm), circularity, structure model index, degree of anisotropy, and the Euler number, were analyzed. Micropores were generally regularly shaped and the main contributors to the total number of pores, whereas macropores were mostly elongated and contributed to total porosity. With increasing depth, the most noticeable changes appeared in silt soil and the least noticeable in clay soil. The alternate pore deformation pattern was significant in silt and silty clay soils. Soil depth significantly influenced all soil pore parameters, whereas soil type significantly affected the remaining parameters, except circularity and degree of anisotropy. The elongated macropores in silt and silty clay soils favor land subsidence in the Xi’an area. The present results can help optimize the groundwater exploitation layer, reducing soil compaction and land subsidence in this area.

ACS Style

Kun Yu; Yang Duan; Maosheng Zhang; Ying Dong; Luchen Wang; Ye Wang; Xu Guo; Fusheng Hu. Using micro focus industrial computed tomography to characterize the effects of soil type and soil depth on soil pore characteristics, morphology, and soil compression in Xi’an, China. Journal of Soils and Sediments 2019, 20, 1943 -1959.

AMA Style

Kun Yu, Yang Duan, Maosheng Zhang, Ying Dong, Luchen Wang, Ye Wang, Xu Guo, Fusheng Hu. Using micro focus industrial computed tomography to characterize the effects of soil type and soil depth on soil pore characteristics, morphology, and soil compression in Xi’an, China. Journal of Soils and Sediments. 2019; 20 (4):1943-1959.

Chicago/Turabian Style

Kun Yu; Yang Duan; Maosheng Zhang; Ying Dong; Luchen Wang; Ye Wang; Xu Guo; Fusheng Hu. 2019. "Using micro focus industrial computed tomography to characterize the effects of soil type and soil depth on soil pore characteristics, morphology, and soil compression in Xi’an, China." Journal of Soils and Sediments 20, no. 4: 1943-1959.

Journal article
Published: 26 October 2019 in Water
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Many irrigated plains in arid and semi-arid regions have groundwater quality issues due to both intensive human activity and natural processes. Comprehensive studies are urgently needed to explore hydrogeochemical evolutions, investigate possible pollution sources, and understand the controls on groundwater compositions in such regions. Here, we combine geostatistical techniques and hydrogeochemical assessments to characterize groundwater quality over time in the Yinchuan Plain (a typical irrigated plain in China), using 12 physicochemical variables derived from sampling in 600 and 602 wells in 2004 and 2014, respectively. Our results show that groundwater-rock interactions and evaporation are the key natural factors controlling groundwater compositions. Hydrogeochemical water types in both 2004 and 2014 were Ca-HCO3, Na-Cl, and mixed Ca·Mg-Cl. Along with the hydrogeochemical compositions, we used ionic ratios and the saturation index to delineate mineral solution reactions and weathering processes. Dissolution of gypsum, halite, fluorite, and mirabilite, along with silicate weathering and cation exchange, were identified in the study area. Our results indicated rising ion concentrations in groundwater, which could be the result of anthropogenic influences. Increasing total hardness and nitrates over the study period were most likely caused by agricultural activity and the discharge of waste water from human residential areas.

ACS Style

Luchen Wang; Yi Mei; Kun Yu; Ying Li; Xuchen Meng; Fusheng Hu; Wang; Mei; Yu; Li; Meng; Hu. Anthropogenic Effects on Hydrogeochemical Characterization of the Shallow Groundwater in an Arid Irrigated Plain in Northwestern China. Water 2019, 11, 2247 .

AMA Style

Luchen Wang, Yi Mei, Kun Yu, Ying Li, Xuchen Meng, Fusheng Hu, Wang, Mei, Yu, Li, Meng, Hu. Anthropogenic Effects on Hydrogeochemical Characterization of the Shallow Groundwater in an Arid Irrigated Plain in Northwestern China. Water. 2019; 11 (11):2247.

Chicago/Turabian Style

Luchen Wang; Yi Mei; Kun Yu; Ying Li; Xuchen Meng; Fusheng Hu; Wang; Mei; Yu; Li; Meng; Hu. 2019. "Anthropogenic Effects on Hydrogeochemical Characterization of the Shallow Groundwater in an Arid Irrigated Plain in Northwestern China." Water 11, no. 11: 2247.

Research article
Published: 23 January 2018 in Geofluids
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After exploitation of groundwater had been reduced and the groundwater level of the confined aquifer had risen, land subsidence was observed to continue rather than cease for several years according to the layer-wise mark monitoring data in Xi’an. To analyze the phenomena, a numerical model of a coupled one-dimensional multilayer aquifer system is developed to represent land subsidence due to hydraulic head variation in the pumped layer. The numerical simulation results show that the pressure head in other layers does not rise immediately when the hydraulic head in the pumped layer starts to recover after pumping ceases. In addition, after the pumping is stopped, a dividing point can be found in aquitards next to the pumped layer, with the aquitards being divided into two parts: a compressed part and a rebounding part. The dividing points move toward the side and away from the pumped layer with the transferring of pore pressure in the aquitard. The results of the simulation also show that there is a transition period between land subsidence and rebound. In this transition period, land could continue to subside even though the hydraulic head in the pumped layer begins to recover.

ACS Style

Ye Wang; Mao-Sheng Zhang; Fu-Sheng Hu; Ying Dong; Kun Yu. A Coupled One-Dimensional Numerical Simulation of the Land Subsidence Process in a Multilayer Aquifer System due to Hydraulic Head Variation in the Pumped Layer. Geofluids 2018, 2018, 1 -12.

AMA Style

Ye Wang, Mao-Sheng Zhang, Fu-Sheng Hu, Ying Dong, Kun Yu. A Coupled One-Dimensional Numerical Simulation of the Land Subsidence Process in a Multilayer Aquifer System due to Hydraulic Head Variation in the Pumped Layer. Geofluids. 2018; 2018 ():1-12.

Chicago/Turabian Style

Ye Wang; Mao-Sheng Zhang; Fu-Sheng Hu; Ying Dong; Kun Yu. 2018. "A Coupled One-Dimensional Numerical Simulation of the Land Subsidence Process in a Multilayer Aquifer System due to Hydraulic Head Variation in the Pumped Layer." Geofluids 2018, no. : 1-12.

Journal article
Published: 01 September 2016 in Environmental Pollution
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Ordos Basin is located in an arid and semi-arid region of northwestern China, which is the most important energy source bases in China. Salawusu Formation (Q3 s) is one of the most important aquifer systems of Ordos Basin, which is adjacent to Jurassic coalfield areas. A large-scale exploitation of Jurassic coal resources over ten years results in series of influences to the coal minerals, such as exposed to the oxidation process and dissolution into the groundwater due to the precipitation infiltration. Therefore, how these processes impact groundwater quality is of great concerns. In this paper, the descriptive statistical method, Piper trilinear diagram, ratios of major ions and canonical correspondence analysis are employed to investigate the hydrochemical evolution, determine the possible sources of pollution processes, and assess the controls on groundwater compositions using the monitored data in 2004 and 2014 (before and after large-scale coal mining). Results showed that long-term exploration of coal resources do not result in serious groundwater pollution. The hydrochemical types changed from HCO3−-CO32− facies to SO42−-Cl facies during 10 years. Groundwater hardness, nitrate and sulfate pollution were identified in 2014, which was most likely caused by agricultural activities.

ACS Style

Qingchun Yang; Luchen Wang; Hongyun Ma; Kun Yu; Jordi Delgado Martin. Hydrochemical characterization and pollution sources identification of groundwater in Salawusu aquifer system of Ordos Basin, China. Environmental Pollution 2016, 216, 340 -349.

AMA Style

Qingchun Yang, Luchen Wang, Hongyun Ma, Kun Yu, Jordi Delgado Martin. Hydrochemical characterization and pollution sources identification of groundwater in Salawusu aquifer system of Ordos Basin, China. Environmental Pollution. 2016; 216 ():340-349.

Chicago/Turabian Style

Qingchun Yang; Luchen Wang; Hongyun Ma; Kun Yu; Jordi Delgado Martin. 2016. "Hydrochemical characterization and pollution sources identification of groundwater in Salawusu aquifer system of Ordos Basin, China." Environmental Pollution 216, no. : 340-349.