Shuangbao Han

The ecological environment of the northwest inland basin is fragile. The groundwater environment is a crucial influencing factor for the harmonious and sustainable development of the local social economy and the ecological environment. It is significant to investigate the groundwater chemical characteristics, water quality, and the factors that influence groundwater chemistry for groundwater resources development and construction of the ecological environment. In this study, the Jinta Basin (JB), Gansu Province, was the selected study area. Three hundred and fifty groups of shallow groundwater samples in the JB were collected and analyzed, and the characteristics and controlling factors of groundwater were determined by using Piper diagram, Gibbs plot, ion ratio relationship, and factor analysis. Single index evaluation method, comprehensive evaluation method, and entropy-weighted water quality index method were used to evaluate the water quality of the groundwater. The results indicated that the shallow pore water in the JB was alkaline as a whole; the ranges of total dissolved solids (TDS) in the Beidahe River impact area (BIA), the transition area (TA) and the Heihe River impact area (HIA) were 328.4–12,400 mg·L⁻¹, 372.70–3774.0 mg·L⁻¹, and 366.30–75,200.0 mg·L⁻¹, respectively; the major anions and cations of the shallow pore water were SO₄²⁻/Cl⁻ and Mg²⁺/Na⁺, respectively. The Piper diagram illustrated that the hydrochemical type of groundwater in the JB were mainly HCO₃·SO₄-Mg type, SO₄·HCO₃-Mg type, SO₄-Mg·Na type, SO₄·Cl-Na·Mg type, and Cl-Na type. The overall water quality of the shallow groundwater in the JB was relatively poor, mainly falling into Class IV-V water quality. Sulfate, total hardness (TH), TDS, chloride and sodium were the main influencing factors of water quality. The chemical characteristics of groundwater in the JB were controlled by a variety of natural factors, including rock weathering, evaporative concentration, and cation exchange, among which the main controlling factors of shallow pore water were leaching, evaporative concentration and anthropogenic activities (contribution rate of 73.94%), and sulfate rock and carbonate rock dissolution (contribution rate of 14.91%).

The Fengfeng mining area is in the transition zone between the North China Plain and the Taihang Mountains, and groundwater is the main source of water supply in the district. Under the combined influence of human activities and natural geological conditions, the quality of different types of groundwater varies greatly, posing a potential threat to the safety of drinking water. In this study, hydrogeochemical processes in different types of groundwater were analyzed using multivariate statistical analysis methods with ion–ratio relationships, and a groundwater quality and health risk assessment model was developed. The research findings show that the main chemical components and TDS in the groundwater have obvious spatial distribution characteristics, i.e., the content of deep karst water (DKW) in the west is significantly lower than that of shallow pore water (SPW) in the east, and the hydrochemical type has changed from HCO₃–Ca to SO₄–Ca. The chemical components of SPW and DKW are mainly derived from silicates and carbonates, accompanied by weathering dissolution of sulphidic minerals, especially SPW. The chemical components of the groundwater was also influenced by the cation exchange reaction and human activities. The quality of the SPW was significantly worse than that of the DKW, and the nitrates in SPW carry a high non-carcinogenic risk, especially to children. The shallow pore water is not suitable for drinking water. This study can provide guidance on the safety of drinking water in the Fengfeng coal mining area and other areas with intensive industrial, mining, and agricultural activities.

Groundwater plays an irreplaceable role in all aspects of the Loess Plateau. In this study, the loess phreatic water (LPW) and bedrock phreatic water (BPW) in the Ning County area (NCA) were sampled and analyzed, and the characteristics and controlling factors of groundwater were determined by using statistical analysis, hydrochemical methods, and hydrogeochemical simulation. The results indicated that the groundwater in the NCA was alkaline as a whole, and the average pH values of LPW and BPW were 8.1 and 7.8, respectively. The mean values of TDS concentrations of LPW and BPW were 314.9 mg/L and 675.3 mg/L, and the mean values of TH contents were 194.6 mg/L and 286.6 mg/L, respectively, which were mainly divided into hard fresh water. The Piper diagram illustrated that the hydrochemical type of groundwater in the NCA was mainly the HCO₃·Ca type. The main recharge source of groundwater was atmospheric precipitation, and it was affected by evaporation to a certain extent. The linear relationships of δ¹⁸O and δ²H of LPW and BPW were δ²H = 6.998δ¹⁸O − 3.802 (R² = 0.98) and δ²H = 6.283δ¹⁸O − 10.536 (R² = 0.96), respectively. Hydrochemical analysis indicated that the groundwater in the NCA was mainly controlled by rock weathering and cation exchange. BPW was affected by the dissolution of gypsum. The possible mineral phases were identified on the basis of the main soluble minerals in the aquifer, and hydrogeochemical reverse simulations were performed. The dissolution of calcite, illite, and hornblende, and the precipitation of dolomite, plagioclase, and microcline occurred on both the LPW and BPW pathways.

The fresh groundwater in the Loess Plateau serves as a major source of water required for the production and livelihood of local residents and is greatly significant for regional economic and social development and ecological protection. This paper analyzes the hydrogeological conditions and groundwater characteristics in the Loess Plateau, expatiates on the types and distribution characteristics of the fresh groundwater in the plateau, and analyzes the influencing factors and mechanisms in the formation of the fresh groundwater in the plateau as a priority. Based on this, it summarizes the impacts of human activities and climatic change on the regional fresh groundwater. The groundwater in Loess Plateau features uneven temporal-spatial distribution, with the distribution space of the fresh groundwater closely relating to precipitation. The groundwater shows a distinct zoning pattern of hydrochemical types. It is fresh water in shallow parts and is salt water in deep parts overall, while the fresh water of exploration value is distributed only in a small range. The storage space and migration pathways of fresh groundwater in the loess area feature dual voids, vertical multilayers, variable structure, poor renewability, complex recharge processes, and distinct spatial differences. In general, the total dissolved solids (TDS) of the same type of groundwater tends to gradually increase from recharge areas to discharge areas. Conditions favorable for the formation of fresh groundwater in loess tablelands include the low content of soluble salts in strata, weak evaporation, and special hydrodynamic conditions. Owing to climate change and human activities, the resource quantity of regional fresh water tends to decrease overall, and the groundwater dynamic field and the recharge-discharge relationships between groundwater and surface water have changed in local areas. Human activities have a small impact on the water quality but slightly affect the water quantity of the groundwater in loess.