The alluvial plain (Anqing section) of the lower reaches of the Yangtze River basin is facing increasing groundwater pollution, not only threatening the safety of drinking water for local residents and the sustainable development and utilization of groundwater resources but also the ecological security of the Yangtze River Basin. Therefore, it is necessary to conduct a preliminary analysis on the hydrochemical characteristics and evolution law of groundwater in this area. This study aimed to evaluate potential hydrogeochemical processes affecting the groundwater quality of this area by analyzing major ions in groundwater samples collected in 2019. Compositional relationships were determined to assess the origin of solutes and confirm the predominant hydrogeochemical processes controlling various ions in groundwater. Moreover, factors influencing groundwater quality were evaluated through the factor analysis method, and the control range of each influencing factor was analyzed using the distribution characteristics of factor scores. Finally, reverse hydrogeochemical simulation was carried out on typical profiles to quantitatively analyze the hydrochemical evolution process along flow paths. The Piper trilinear diagram revealed two prevalent hydrochemical facies, Ca-HCO₃ type (phreatic water) and Ca-Na-HCO₃ type (confined water) water. Based on the compositional relationships, the ions could be attributed to leaching (dissolution of rock salt, carbonate, and sulfate), evaporation and condensation, and cation exchange. Four influencing factors of phreatic water and confined water were extracted. The results of this study are expected to help understand the hydrochemical characteristics and evolution law of groundwater in the alluvial plain (Anqing section) of the lower Yangtze River basin for effective management and utilization of groundwater resources, and provide basic support for the ecological restoration of the Yangtze River Basin.

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.

Anhui Province is rich in geothermal water resources, making the study of its hydrochemical evolution and genetic models essential for scientific development and sustainable utilization. This study combines hydrochemical and hydrogen–oxygen isotopic data from different regions of Anhui Province to analyze the hydrogeochemical evolution characteristics and recharge mechanisms of basin-type and mountainous-type geothermal waters. The results show that basin-type geothermal water is predominantly of the Cl–Na type, with water–rock interactions mainly including halite dissolution, gypsum dissolution, dedolomitization, and silicate hydrolysis. The groundwater system is relatively closed off, with slow flow rates. In contrast, mountainous geothermal water is mainly of the HCO₃–Na·Ca, SO₄–Na·Ca, and SO₄–Na types, with water–rock interactions primarily involving calcite dissolution, dolomite dissolution, and gypsum dissolution. Enhanced precipitation infiltration due to fault structures leads to stronger recharge and an open-system characteristic. The genetic models of the two types of geothermal water reveal the structural and recharge mechanisms of thermal reservoirs under different geological settings, highlighting the significant control of geological background on geothermal water formation.

Coastal engineering construction suitability evaluation methods are too empirical and difficult to quantify. Considering these weaknesses, in order to determine the weight of each factor reasonably, and to analyze the suitability of coastal zone construction comprehensively, the theory of establishing a coastal zone construction suitability evaluation model based on a Rough Set (RS) and an Analytic Hierarchy Process (AHP) is proposed. In total, 20 typical coastal areas of Putian are selected, and the main impact factors are determined according to a port dock, pollution-prone industry, and an electric power plant. The contribution rate and weight of each factor for the construction of a coastal zone are analyzed by the combination evaluation model, and the final evaluation result is consistent with the actual investigation situation. Finally, 52 evaluation units of the Putian coastal zone are evaluated by Neural Networks (NNs). The weight of the impact factors is made more objective by using the training sample set of the combination evaluation model as the sample set of the neural network. The learning speed and accuracy of the network are improved, and the and the evaluation result is consistent with the actual investigation situation. In a word, it is effective to perform the suitability evaluation of the coastal zone construction using the RS-AHP-NN proposed model, and it can be applied in practical engineering.

Karst structures significantly impact the environment and engineering projects. The presence of water-bearing karst structures alters the shallow stratigraphic temperature field. The shallow temperature measurement method offers a simple and efficient approach to obtain shallow ground temperature data, enabling the inference of karst structure distribution through temperature anomalies. In this study, the feasibility of using shallow thermometry to detect karst pipeline structures was investigated via numerical simulation at the Hongsheng Coal Coking Plant and its surrounding sites in Panzhou City, Guizhou Province, China. The results indicate that variations in the burial depth of karst structures markedly influence shallow stratum temperatures. For a single karst conduit with an equivalent diameter of 0.5 m and water temperature of 12 °C, the detectable depth limit is approximately 66 m. Although an increase in the effective flow cross-sectional area affects shallow stratigraphic temperatures, changes in equivalent diameter under the site-specific conditions alter the temperature at 2 m depth by less than 0.02 °C, making it difficult to identify the effective flow cross-sectional area using shallow thermometry. Variations in fluid temperature within a certain range (12–18 °C) also affect shallow ground temperatures, with the influence of lower-temperature fluids being more pronounced. This study provides a rapid, cost-effective, and relatively accurate method for investigating subsurface karst structures, offering important implications for related engineering applications.