As a strategic mineral and energy resource, the enrichment and metallogenic mechanism of sandstone-hosted uranium deposits are highly dependent on hydrogeological conditions. However, the relationship between sandstone uranium mineralization and hydrogeological conditions has not received sufficient attention yet. The pumping test, hydrogeological parameters and hydrochemical characteristics were employed to analyze the change characteristics of hydrogeological conditions and evaluate the suitability of in situ leaching (ISL). The results showed that the study area in the Inner Mongolia Autonomous Region could be divided into two groundwater subsystems, namely Quanzha-Engeriyin and Luhai-Zhendai. The latter with relatively high water richness is confined and a main ore-bearing aquifer, which consists of four orebodies. The well discharge (Q) and hydraulic conductivity (K) of Orebody II ranged from 98.40 to 867.36 m³/d and 0.25 to 5.64 m/d, respectively, indicating the aquifer is suitable for the migration, enrichment and mineralization of uranium due to relatively high permeability and fast flow rate. The water storage of Orebodies III-IV gradually deteriorated from east to west in a stepped pattern. And the highest values of Q and K in Orebodies III-IV decreased from 1200 m³/d to 120 m³/d and 1.75 m/d to 0.035 m/d, respectively, suggesting these were conducive to a reduction in and accumulation of uranium under poor hydrodynamic conditions. Additionally, the study area would be defined as three grades, including favorable, relatively favorable and unfavorable areas of ISL according to a comprehensive evaluation. This study provided a scientific basis for evaluating the possibility of in situ leaching for sandstone-hosted uranium deposit.

Xilinhot City is a significant pastoral city in China where groundwater serves as the primary water source for the cold and arid pastoral regions. The formation and evolution of material components in groundwater, as well as groundwater quality, are directly linked to the health of pastoral residents. This study is based on the physical and chemical test results of 22 groundwater samples collected from the Xilinhot River Basin in Inner Mongolia. Various statistical analyses, including Piper and Chadha diagrams, as well as hydrogeochemical simulation methods, were employed to assess the hydrogeochemical characteristics and material composition sources of groundwater, evaluate groundwater quality and non-carcinogenic risks, and comprehensively discuss the impact of macro- and microelements on human health. The findings indicate that igneous rocks containing minerals such as potassium feldspar, plagioclase, and pyroxene contribute Na⁺, Cl⁻, and K⁺ to the groundwater, while sedimentary rocks containing minerals like dolomite and calcite supply ions such as Ca²⁺, Mg²⁺, and HCO₃⁻. The groundwater quality is primarily classified as Class II–V, with F⁻ and NO₃⁻ exhibiting varying hazard quotients for children and adults in the study area, though they do not pose a non-carcinogenic risk. Additionally, the enrichment of hardness, Ca²⁺, Mg²⁺, Na⁺, SO₄²⁻, and other indicators in localized areas exceeds the recommended values for drinking water, potentially impacting the digestive and urinary systems of the human body. There is a risk of excessive fluoride in areas where F levels exceed 1 mg/L. Furthermore, the content of beneficial micronutrients such as selenium (Se), zinc (Zn), boron (B), and germanium (Ge) is relatively low. Based on the elemental abundance characteristics and a comparative analysis of the chemical properties of groundwater across five regions of China, this comparison facilitates a discussion on the definition of healthy groundwater, particularly in relation to safe consumption in cold and arid regions. This study aims to highlight the health issues associated with drinking groundwater in the cold and arid regions of Mongolia. The findings serve as a valuable reference for efforts aimed at reducing the incidence of endemic diseases and enhancing human lifespan.

As an important drinking water source for Beijing, the capital of China, the water inflow of Miyun Reservoir has been decreasing year by year, which has affected the urban water supply security. To understand the variation trend of the inflow and analyze the main factors influencing the runoff change, this research focused on the watershed of Miyun Reservoir as the target. Based on the runoff data from 1984 to 2020 at the outlet of the basin, as well as the precipitation, potential evaporation intensity, NDVI (normalized difference vegetation index), population, and GDP (Gross Domestic Product) data, combined with correlation analysis methods, empirical statistical methods, the SCRCQ (Slope Change Ratio of Cumulative Quantity) method, and the GIS, the interannual variation characteristics of various elements in the basin were analyzed, the correlation between runoff and other factors was studied, and the influencing degrees of precipitation, water surface evaporation intensity, human activities, and other factors on the runoff change in the basin were quantitatively separated. The research results showed that the runoff exhibited a distinct decreasing trend, and there were two mutation points in the basin runoff from 1984 to 2020, which were 1995 and 2014, respectively. The runoff change was divided into three stages: 1984–1995 (upward trend in T1), 1995–2014 (downward trend in T2), and 2014–2020 (stable trend in T3). Runoff was significantly correlated with four indicators: the summer leaf area index of the Chaohe River and Baihe River, the regional GDP and population, among which the correlation of the summer leaf area index was the largest. Compared with the period T1, the contribution rates of climate change to the runoff reduction in T2 and T3 were 6.38% and 5.73%, and the contribution rates of human activities to the runoff reduction were 93.62% and 94.27%, respectively. Therefore, the change in annual runoff in the Miyun Reservoir watershed is mainly affected by human activities, and the contribution of climate change to the runoff attenuation is weak. This study is significant in the maintenance and enhancement of runoff in typical watershed.