Recurrent freeze–thaw cycling is a powerful weathering process that subjects soil to frost heave and thaw settlement. The cycling significantly changes the soil structure and leads to particle recombination, ultimately causing deterioration of the soil's properties. Herein, we investigated the effect of freeze–thaw cycles on loess-like soil in seasonally frozen regions; specifically with respect to the engineering geological properties, such as changes in grain-size distribution, liquid–plastic limit and collapse behaviour. The results indicate that over the course of 20 freeze–thaw cycles, the soil samples’ dry density decreased, the particle diameter of each soil fraction changed in a bi-directional manner (large particles were broken into finer sizes and fine particles agglomerated into larger particles), and the liquid limit and plasticity index first increased and then decreased. An increase in the initial water content resulted in more significant changes. In contrast to the undisturbed soil samples, the freeze–thaw cycles caused non-collapsible remoulded loess-like soil to collapse. Furthermore, microscopic evaluation allowed us to determine the collapse mechanism. Essentially, after the freeze–thaw cycles, the quantity of micropores in the soil decreased, whereas that of medium pores and macropores significantly increased. In addition, a trellis structure, similar to the typical loess structure, was generated.

An investigation of the distribution and control factors of groundwater is significant for the rational exploitation and utilization of groundwater resources. This study analyzes the hydrogeochemical processes and control factors of shallow groundwater in the Guohe River Basin. A hydrogeological survey was conducted, and hydrochemical and hydrogen–oxygen isotopic data of 125 samples of surface water and groundwater were analyzed. The results showed that the total dissolved solid (TDS) content in shallow groundwater was 138–2967 mg/L, with an average of 831 mg/L. A decline in the TDS was observed from the upper to the lower reaches. The contents of the anions and cations in the shallow groundwater were in the order HCO₃⁻ > Cl⁻ > SO₄²⁻ and Na⁺ and K⁺ > Mg²⁺ > Ca²⁺, respectively. The cation exchange increased the aqueous concentrations of Na⁺ and K⁺, and the TDS content was highly correlated with the contents of Na⁺, Cl⁻, and SO₄²⁻ ions. The δD and δ¹⁸O values in shallow groundwater increased from the upper to the lower reaches, with the mean δD values being −59.72‰, −53.58‰, and −47.17‰ and the mean δ¹⁸O values being −8.33‰, −7.37‰, and −6.43‰. The contribution rates of the recharge source, evaporation, and water–rock interaction to the groundwater TDS concentration were 20.4%, 29.5%, and 50.1%, respectively. The water–rock interaction dominated the formation of shallow groundwater in the Guohe River Basin. The dissolution of salt rock and gypsum contributed to ion formation in shallow groundwater. The research findings can be used to improve the groundwater quality in the Guohe River Basin.

The ground‐coupled ground‐source heat pump (GSHP) system is a common method for shallow geothermal energy exploitation and utilization. GSHP has a great heat exchange rate and wide application range. In order to effectively exploit shallow geothermal energy in the central urban area of Danyang City, Jiangsu Province, based on finite volume method, it is adopted to simulate the amount of recoverable shallow geothermal energy in the study area through ground‐coupled heat exchange. The simulation is conducted on the development trend of thermal transport and thermal balance in the study area from early June 2015 to the end of May 2025 to obtain the temperature distribution at different times. Under the presupposed working conditions, with the operation of a ground‐coupled GSHP, thermal accumulation occurs in parts of the study area. To mitigate the problem of thermal accumulation, two schemes are proposed: (1) adding auxiliary cooling towers and (2) increasing the amount heated domestic water in spring and autumn. Both schemes mitigate thermal accumulation. For Scheme 1, the total heat supply for shallow geothermal energy in the central urban area of Danyang City in winter is 2.91 × 10⁶ kW, and the total heat release in summer is 3.53 × 10⁶ kW. For Scheme 2, the total heat release in summer is 3.52 × 10⁶ kW and the total heat supply in winter is 2.90 × 10⁶ kW. A ground‐coupled GSHP system has significant applicability in the central urban area of Danyang City, where shallow geothermal energy has good exploitation prospects.

To reduce downstream ecological damage, it is crucial to analyze water and salt sources in saline–alkali farmland drainage and optimize soil salt discharge. This study employs statistical, hydrochemical, and isotope methods to identify controlling factors and characteristics in water bodies during winter irrigation. The results show average TDS values of 0.59, 6.40, and 4.14 g/L for irrigation, phreatic, and drainage water. Irrigation and phreatic water mainly belong to the HCO₃-Ca·Mg·Na and Cl·SO₄-Na·Mg types. Na⁺/(Na⁺ + Ca²⁺) and Cl⁻/(Cl⁻ + HCO₃⁻) values suggest the rock–water interaction and evaporation influences in irrigation water, while evaporation primarily controls phreatic water. The main salt types include NaCl, MgSO₄, Na₂CO₃, and CaCO₃ for irrigation water and NaCl, MgSO₄, Na₂SO₄, and CaCO₃ for phreatic water. These findings lay a research basis for analyzing water and salt sources in farmland drainage during winter irrigation in saline–alkali land.

Geothermal heating is gaining attention as a low-carbon energy solution with potential for sustainable systems. This article investigates the feasibility of utilizing medium to deep geothermal energy for heating in southern China, particularly in Anguo Town, Pei County, Jiangsu Province. Using TOUGH2 software, we developed a dual-vertical-well geothermal extraction model to simulate various operational scenarios and identify effective heating strategies. Our findings show that the extraction and injection processes enhance groundwater convection, overshadowing the natural flow effects. The reservoir's pressure dynamics allow it to self-regulate, returning to equilibrium after each injection-extraction cycle, while the temperature field can experience thermal breakthroughs due to cooling over time. Key factors influencing outcomes included the injection fluid rate, which greatly impacted produced water temperature and its fluctuations, while the height difference between wells and well spacing primarily affected long-term changes in production temperature. The optimized parameters for the geothermal system in Anguo Town were identified as an injection flow rate of q _inj   = 50 kg/s, a well spacing of d  = 400 m, and a perforation section height difference of Δh  = 168.8 m. Under these conditions, the geothermal system can operate continuously over 50 extraction cycles, providing stable heat supply ranging from 4567.5 to 7492.2 kW each cycle. This research provides valuable insights for effectively harnessing medium to deep geothermal resources for supply heating in southern China, contributing to a more sustainable energy landscape.