Vadose Research Articles

Mercury deposition in central China from the Last Glacial Maximum to the early Holocene recorded in an accurately-dated stalagmite

Characterization of transport pathways and depositional changes in Mercury (Hg) and their connection to climatic and environmental changes on various time scales are crucial for better understanding the anthropogenic impacts on the global Hg cycle in the Anthropocene epoch. In this study, we examined Hg variations recorded in a stalagmite from central China, covering the period from 25.5 to 10.9 thousand years ago. Our data show a marked increase in Hg concentrations during the late Last Glacial Maximum, which coincided with the period of highest dust deposition on the Chinese Loess Plateau. Hg concentrations were lower during Heinrich events 1 and 2 and the Younger Dryas but higher during the Bølling-Allerød and the early Holocene. We suggest that regional dust load, which enhances atmospheric dry deposition of Hg, is the primary factor influencing Hg deposition in central China on glacial-interglacial timescales. On millennial-to-centennial timescales, climate also plays a significant role. Warmer and wetter conditions increase vegetation, litterfall, and soil/rock weathering, which in turn boost mineral dissolution and soil erosion in the vadose zone. These processes collectively result in higher Hg concentrations in the stalagmite.

Controls on Oxygen Variability and Depletion in the Patuxent River Estuary

Oxygen depletion in coastal waters is increasing globally due primarily to eutrophication and warming. Hypoxia responses to nutrient loading and climate change have been extensively studied in large systems like the Chesapeake Bay and the Baltic Sea, while fewer studies have investigated smaller, shallower hypoxic zones. Thus, an improved understanding of the interactions of eutrophication and warming on hypoxia expansion (or reduction) in the wide variety of different estuarine environments is needed. We examined interannual controls on oxygen depletion in the Patuxent River estuary, a eutrophic sub-estuary of Chesapeake Bay where seasonal hypoxia develops annually. We conducted a spatial and temporal analysis of dissolved oxygen (DO) trends, timing, and several metrics of depletion over a long-term record (1985–2021). We found an internally generated hypoxic zone that initiates in the middle estuary, spreading upstream and downstream as the summer progresses, and that hypoxic volume days (HVD) have been increasing (0.11 per year, p = 0.03) over the record despite reduced watershed nitrogen loads and stable phosphorus loads. River flow and temperature have been increasing and are major drivers of increased HVD, with river flow explaining 40% of the interannual variation in HVD (temperature has increased 0.03 and 0.06 °C per year in summer and fall, respectively). Apparent oxygen utilization (AOU) is increasing in bottom waters in the fall, consistent with increasing trends of both water temperature and stratification strength. HVD was negatively related (r2 = 0.34, slope = −0.59*HVD) to the biomass of benthic invertebrates in the middle region of the estuary, suggesting that benthic forage for higher trophic levels will be limited by sustained hypoxia. These results indicate that current and future climate variability plays an important role in regulating oxygen depletion in the Patuxent River estuary, which reinforces the need to factor climate change into strategies for the restoration and management of estuaries.

A batch experiment for determining retardation factors of Ni2+, Zn2+, Cd2+, and Pb2+ in unsaturated zone of unconsolidated formation in Man Xa and Chau Khe communes, Bac Ninh province

A batch experiment for determining retardation factors of Ni2+, Zn2+, Cd2+, and Pb2+ in unsaturated zone of unconsolidated formation in Man Xa and Chau Khe communes, Bac Ninh province

Deciphering chemical and physical processes that give rise to natronization in a shallow aquifer in an arid zone

Groundwater provides a reliable and stable alternative to surface water resources in arid and semiarid regions to meet human and environmental needs. However, excessive exploitation in the last decades has led to significant salinization of groundwater and soils in many parts of the world. In the highlands of central-north Mexico, a number of agriculturally used aquifers show increasing salinization effects. Tierra Nueva is a case where salt precipitations in recent years have made land mostly unsuitable for agriculture. It is assumed that the intensive irrigation under dry climatic conditions, together with the presence of argillaceous horizons at shallow depth and the alteration of Na-rich volcanic rocks, determine the occurrence of specific salinization processes producing evaporite minerals in excess. This investigation provides physical and chemical evidence of groundwater processes explaining the accumulation of solutes in groundwater and soils. It shows that the principal evolutionary processes in the studied aquifer were water-rock interactions and evaporation, while ionic exchange processes dominated the water circulating through the clay-sandy materials of the valley. Geochemical models show that recharging water dissolved CO2 from the unsaturated zone, and reacted with silicates (i.e. hydrolysis of albite, K-feldspar, and biotite), underwent cation exchange, and precipitated kaolinite. In the discharge area, the mineral natron was dissolved, while thermonatrite, natrolite (Na-natrolite), nontronite (Ca-nontronite, K-nontronite, Mg-nontronite, Na-nontronite) were formed, among other reactions. This salinization process eventually leads to soils which are unsuitable for agricultural activities. The study of this phenomenon represents an important contribution to the understanding of the implications of the expansion of arid and semiarid lands.

Reconstructing 273 Years of Potential Groundwater Recharge Dynamics in a Near-Humid Monsoon Loess Unsaturated Zone Using Chloride Profiling

Understanding the historical groundwater recharge process and its influencing factors is crucial for effectively managing regional groundwater resources amidst future climate change. However, the availability of high-resolution hydroclimate archives remains severely limited. In this study, we used a 59 m chloride profile within the unsaturated loess zone to reconstruct the potential groundwater recharge (PGR) records spanning 273 years in a near-humid area on the Loess Plateau. Spectral analysis was employed to identify the principal influencing factors on PGR across various time scales. The reconstructed hydrological records revealed three wet periods and four dry periods from 1745 to 2007 AD, with PGR rates ranging from 66.7 to 222.4 mm yr−1 during wet periods and 20.0 to 66.7 mm yr−1 during dry periods. In addition, spectral analysis indicated multiple cycles, ranging from 2.1 to 50.0 years, within the PGR history. Temperature, precipitation, and sunspot activity emerged as the key factors governing the rate of PGR over the 3-year, 7-year, and 11-year time scales, respectively, highlighting the combined influence of solar activity and climate on the PGR process. These findings enhance our understanding of groundwater recharge and environmental climate dynamics in the near-humid loess unsaturated zone and other regions exhibiting similar hydroclimatic conditions.

Characterization and stable isotopic fingerprinting of mine seepage in hyperarid environments: An example of the Namib Lead & Zinc mine, Namibia

Mine drainage at the Namib Lead & Zinc mine in the hyperarid environment of the Namib Desert close to Swakopmund, Namibia, has been investigated using mineralogical, hydrochemical, and isotopic methods. The principal ore minerals are galena and sphalerite. Mine drainage is neutral due to the reactions with the marble gangue rock. Mine water seepage is of the Na-Ca-Cl-SO4 type and sources of dissolved ions are likely halite and gypsum in the unsaturated zone above the mine. Concentrations of dissolved metals are relatively low, and the principal attenuation mechanism of metals is probably their adsorption on ferric minerals because equilibrium of the seepage water with secondary minerals that host the metals is not attained. Based on strongly enriched δ2H (up to 13.27 ‰) and δ18O (up to 4.5 ‰) values, seepage water originates from advective fog and is strongly evaporated after the fog deposition. The high δ13C(DIC) values indicate equilibrium with carbonates and CO2 de-gassing. The δ34S(SO4) values are enriched in shallower depths, probably because of pedogenic gypsum dissolution and then the δ34S values decrease with depth, probably due to the increasing input of sulfur from sulfides. Mine drainage at the Namib Lead & Zinc mine does not represent any risk for the environment due to its neutral character and relatively low seepage water volumes caused by high degree of aridity.

Empirical relationship between vadose zone properties and diesel attenuation capacity: A complement for intrinsic vulnerability models

Evaluating and predicting the natural attenuation capacity (AC) of a vadose zone is essential for determining groundwater vulnerability to contamination from upper sources. However, it remains unclear how the physicochemical properties of vadose zone soils affect AC owing to their complexity and spatial heterogeneity. In this study, we developed a regression model for estimating the AC of a vadose zone against diesel using datasets from different soils with a wide range of physicochemical properties. Among the 17 properties, six (i.e., organic matter (OM), total phosphorous (TP), coefficient of uniformity, particle size (D30), van Genuchten’s n, saturation degree (SD)) were selected as primary regressors. The results indicate that biogeochemical factors, including OM and TP, have decisive effects on the AC. Finally, the regression model was expanded to a GIS-based spatial model and applied to Namyangju, Korea using the index-overlay method. The produced AC map showed a nonmonotonic decrease along the depth, and the areas closer to the water bodies generally represented low AC values, most likely due to the lower OM, TP, and higher SD. This study provides an empirical basis for future research initiatives for spatial and temporal AC dynamics, which complements conventional intrinsic groundwater vulnerability models such as DRASTIC.

Groundwater Vulnerability Assessment—Case Study: Tirana–Ishmi Aquifer, Albania

This paper discusses the groundwater vulnerability to pollution assessment for the Tirana–Ishmi alluvium aquifer, Albania. Economic activities, municipal wastewater discharged into rivers and groundwater overexploitation threaten to pollute the groundwater. Based on the aquifer characteristics and the available data, SINTACS was selected as the most realistic assessment model. The SINTACS parameters’ rates assigned to the aquifer’s characteristics (water table depth, infiltration, unsaturated zone, soil media, aquifer media, hydraulic conductivity, topography) were adapted to the local features, followed by GIS vulnerability mapping. Statistical analysis indicates that the unsaturated zone, hydraulic conductivity and aquifer media have the highest influence on groundwater vulnerability, whereas topography has the lowest influence. Validation through sensitivity analysis and nitrates content confirms the rational selection of the SINTACS model and the reliability of the study’s outputs. The most vulnerable areas to pollution are the recharge zones, followed by the highly urbanized Tirana City area, characterized by high levels of groundwater extraction rate and wastewater discharged into the rivers. The paper, being the first completed groundwater vulnerability assessment of the study area, could serve as a basis for a scientific–based groundwater management that should be considered in local territory planning.

Distribution and soil threshold of selenium in the cropland of southwest mountainous areas in China

To investigate the distribution characteristics of selenium (Se) in mountainous soil-crop systems and examine the threshold value of Se-rich soil, 275 soil samples and 153 associated crop samples (rice, maize, tea, nuts, konjac, mushrooms, buckwheat, and coffee) were collected in Ximeng County, a typical mountainous area in southwest China. The total Se, available Se, organic matter, pH, sampling point elevation, and crop Se content were analyzed to examine the distribution characteristics of soil Se and the ability of primary crops to enrich Se in Ximeng County. Random forest and multiple regression models were established to identify the factors influencing the available soil Se and the crop Se enrichment coefficient. Finally, the Se-rich soil threshold was examined based on the total Se, available Se, and Se content in primary crops (rice, maize, and tea). The results showed soil Se resource abundance in the study region, with high Se soil accounting for 64.72% of the entire area. The soil Se content displayed significant spatial autocorrelation. The average Se enrichment coefficient of the main cultivated crops included mushrooms > nuts > rice > coffee > tea > maize > buckwheat > konjac. The total Se content in the soil had the highest impact on the available Se content in the soil and the Se enrichment coefficient of crops. A Se-rich soil threshold of 0.3 mg·kg−1 was used for rice and maize, while that of tea was 0.4 mg·kg−1. This result provided a theoretical basis for developing and utilizing Se resources in mountainous soil in southwestern China and dividing the Se-rich soil threshold.

Development of a coupled surface water–groundwater model for the spatiotemporal simulation of river–aquifer interactions

AbstractIntegrating surface and groundwater use is a crucial part of water management. When one type of water is depleted, the other follows suit because of the constant movement and interaction between them. Therefore, the primary objective of this research is to establish a method by which the water evaluation and planning system (WEAP) surface water model and the MODFLOW groundwater model can communicate with one another. This article aims to demonstrate the interdependence of groundwater and surface water. Here, we use MODFLOW to model the saturated soil region and the soil moisture method to model the unsaturated soil region. The interaction between surface water and groundwater will affect the region's water resources and how they will operate under the continuance of existing practices. The simulation of saturated and unsaturated soil zones using a connected model of surface and groundwater employing all the hydroclimatology balance components is one of the most significant accomplishments of this research. The findings show that the (Iran) Sonqor Plain's maximum aquifer recharge throughout the months of November to May during a period of 30 years (October 1991 to September 2020) ranges between 1.5 and 2.6 million m³. A lack of recharge from irrigation water infiltration occurs in some of these months in addition to rain. The highest rate of groundwater level increase in this area is 4.5 m yr⁻¹ as a result of the distribution of irrigation water provided from the dam in the north‐western region.

Spatiotemporal Analysis of Sonar Detection Range in Luzon Strait

Sonar serves as a critical submarine detection apparatus for naval vessels, with its detection range forming the foundation of its overall performance in underwater surveillance. The Luzon Strait, in the eastern part of the South China Sea, presents a complex hydrographic setting that profoundly influences sonar performance, necessitating mastery of the detection range variation for enhanced anti-submarine operational efficiency. This study employs the Bellhop acoustic propagation model to estimate the transmission loss. Subsequently, a detection probability integration approach is applied to determine the sonar detection range in the Luzon Strait from 2019 to 2023, which is then subjected to statistical analysis. The findings indicate the following. (1) During the summer and autumn, the shallow mixed layer fails to generate a surface duct, resulting in shorter detection ranges that are primarily dependent on the water depth. In the Shallow Water Zone (<150 m), frequent interactions between sound waves and the sea boundaries lead to considerable acoustic energy attenuation, maintaining a short detection range. In the Intermediate Depth Zone (150–2500 m), sound rays retain adequate energy post-seabed reflection, extending the sonar detection to 5–8 km. Beyond 2500 m, the diminishing reflective energy restricts the range to 2–5 km. (2) Conversely, in the winter and spring, the formation of a surface duct becomes the predominant determinant of the detection range, capable of exceeding 10 km, overshadowing the influence of the water depth.

Drivers of Daily Water Level Fluctuation of Shallow Groundwater in the Inner Delta of the River Danube

Groundwater flow systems are influenced by the changes in surface waters as well as climatic factors. These teleconnections significantly increase in cases of extreme weather conditions. To prepare and mitigate the effect of such phenomena, the background factors that create and influence natural processes must be recognized. In the present study, 94 shallow groundwater (SGW) wells’ water level time series were analyzed in the inner delta of the River Danube (Europe) the Szigetköz region to explore which factors contribute to the development of diurnal periodicity of SGW and what its drivers are. The relationship between surface meteorological processes and SGW dynamics in the Szigetköz region was investigated using hourly data from monitoring wells. Hourly water temperature data exhibited weak correlations with meteorological parameters. However, daily averaged data revealed stronger correlations, particularly between SGW levels and air temperature and potential evapotranspiration. Diurnal periodicity in SGW fluctuations correlated strongly with potential evapotranspiration. The study also demonstrated the role of capillary fringe dynamics in linking surface evapotranspiration with SGW fluctuations. Changes in groundwater levels, even small, can significantly affect soil moisture, vegetation, and ecosystem functioning, highlighting the sensitivity of the unsaturated zone to SGW fluctuations driven by surface processes.

Analytical model for the mitigation of VOC vapor with horizontal permeable reactive barrier in the contaminated site considering non-uniform source

Volatile organic compounds (VOCs) contamination at the groundwater may cause vapor intrusion and pose significant threats to human health. As a novel low-carbon mitigation technology, a horizontal permeable reactive barrier (HPRB) is proposed to remove the VOC vapor in the vadose zone and mitigate the vapor intrusion risk. To estimate the performance of HPRB in the contaminated site with a non-uniform source, a transient two-dimensional analytical model is developed in this study to simulate the VOC vapor migration and oxidation processes in the layered soil. The analytical model is verified against the experimental results and numerical simulation first and the parameter study is then conducted. The HPRB has good performance for the contaminated sites involving factors including deep source and local soil with low effective diffusivity. To consider the vertical heterogeneity of the local soil, the traditional equivalent homogeneity method has limitations in considering the horizontal migration of VOC vapor and is not suitable for the two-dimensional model. On the contrary, the artificial layered method based on the proposed analytical model has better accuracy and is recommended to be adopted in practice. Leading to the exponential decrease in the VOC vapor concentration at the ground surface, increasing the thickness of HPRB is an effective measure to enhance the performance of HPRB. The fitting exponential function can be applied to determine the minimum design value of the thickness of HPRB in practice.

Detecting sources of water leakage in fractured limestone: Case study in Mokattam District, Egypt

ABSTRACT The paper investigates the sources of water leakage in Mokattam, Cairo, Egypt. It is considered a high-risk zone for landslides due to the presence of problematic soil, topography, and water conditions. The objective is to mitigate the negative impact of underground water on landslide disasters. The proposed methodology involves field visits, satellite image processing, Ground Penetration Radar scanning, chemical and isotope analysis of water, and evaluating the water and sanitary networks within the study area. The findings revealed that the underground water is formed because of the continuous leakage from the existing networks. Moreover, there was no evidence of any aquifers, particularly at Ain Mosa floating point. Thus, the accumulated water in the unsaturated zone is not sustainable for long-term development for its limited potential and poor quality. Consequently, immediate action plan is required to assess and upgrade the water and sanitary networks through the implementation of innovative technologies for such hydrogeologic conditions

Elucidating biogeochemical characterization of nitrogen in the vadose zone integrating geochemistry, microorganism, and numerical simulation

A thorough comprehension of nitrogen biogeochemical processes in the vadose zone is crucial for the effective prevention and remediation of soil-groundwater system contamination. Despite the growing research on this subject, the full scope of nitrogen biogeochemical characterization in different geological environments remains poorly understood. This study addresses this knowledge gap by integrating geochemical, microbiological and numerical simulation approaches to gain a deeper insight into nitrogen biogeochemistry in agriculture. Our findings indicate the biogeochemical behavior of nitrogen in the vadose zone is mediated by microorganisms, driven by hydraulics, influenced by geological conditions and environmental factors. Along the groundwater flow, NH4+-N was found to be heavily accumulated in the topsoil of 0–40 cm, while NO3−-N was transported and driven by hydrodynamics from both vertical and horizontal directions. Microbial diversity, species composition and functional microorganisms were significantly influenced by soil depth, rather than geomorphological types. Oxidation-reduction potential (ORP), total organic carbon (TOC), soil moisture (MOI), bicarbonate (HCO3−), and ferrous (Fe2+) were identified as the principal environmental factors that regulate nitrogen metabolism and the dominant biochemical processes, encompassing nitrogen fixation, nitrification, and denitrification. Driven by hydrodynamics, NH4+-N, NO2−-N and NO3−-N tend to form distinct biochemical reaction zones in the vertical vadose zone. These areas are dynamic and subject to geomorphologies. It should be noted that NO3−-N can migrate towards groundwater from the clayey sand in the Alluvial Plain, which presents a potential risk of groundwater contamination. The fissure structure of loess may serve as the major transport pathway for groundwater nitrogen contamination in the Loess Tableland. This finding highlights the importance of integrating microbiology, geochemistry and hydraulics to elucidate the biogeochemical processes of nitrogen in the vadose zone with a dynamic mindset.

Mapping the Future: Revealing Habitat Preferences and Patterns of the Endangered Chilean Dolphin in Seno Skyring, Patagonia.

Species distribution modeling helps understand how environmental factors influence species distribution, creating profiles to predict presence in unexplored areas and assess ecological impacts. This study examined the habitat use and population ecology of the Chilean dolphin in Seno Skyring, Chilean Patagonia. We used three models-random forest (RF), generalized linear model (GLM), and artificial neural network (ANN)-to predict dolphin distribution based on environmental and biotic data like water temperature, salinity, and fish farm density. Our research has determined that the RF model is the most precise tool for predicting the habitat preferences of Chilean dolphins. The results indicate that these dolphins are primarily located within six kilometers of the coast, strongly correlating with areas featuring numerous fish farms, sheltered waters close to the shore with river inputs, and shallow productive zones. This suggests a potential association between dolphin presence and fish-farming activities. These findings can guide targeted conservation measures, such as regulating fish-farming practices and protecting vital coastal areas to improve the survival prospects of the Chilean dolphin. Given the extensive fish-farming industry in Chile, this research highlights the need for greater knowledge and comprehensive conservation efforts to ensure the species' long-term survival. By understanding and mitigating the impacts of fish farming and other human activities, we can better protect the habitat and well-being of Chilean dolphins.

Understanding Salinity Intrusion and Residence Times in a Small-Scale Bar-Built Estuary under Drought Scenarios: The Maipo River Estuary, Central Chile

The Maipo River estuary is a low-inflow bar-built estuary that includes a protected wetland, which harbors a rich ecosystem. The estuary and wetland have been threatened by a persistent drought for more than a decade, which has resulted in greater salinity intrusion and increased residence times. Previous studies have described salinity and pollutants in estuaries; however, almost all have focused on deeper and/or wider estuaries with dimensions much larger than those of the small-scale Maipo River estuary. In this study, we used the numerical model FVCOM to simulate the dynamics of the Maipo River estuary under drought scenarios and explored the interactions between river discharge and tides in terms of saline intrusion and particle dispersal. The model was validated against observations collected during a field campaign near the river mouth. The simulations successfully reproduced the water surface elevation but underestimated salinity values, such that the vertical salinity structure observed in the field was not captured by the model in this shallow and morphologically complex estuary. Consequently, our model results provide qualitative insight related to salinity and baroclinic dynamics. Results of maximum saline intrusion showed an exponential decay with increasing river discharge, and the analysis of salinity intrusion time series revealed that droughts may cause permanent non-zero salinity levels in the estuary, potentially affecting ecological cycles. The incorporation of passive tracers showed that decreasing river discharge increases the residence time of particles by allowing the tracers to re-enter the estuary. Model results showed the formation of accumulation zones (hotspots) in the shallower zones of the estuary.

Vapor-phase transport of per and polyfluoroalkyl substances: Processes, modeling, and implications

An increasing number of studies have demonstrated the presence of per and polyfluoroalkyl substances (PFAS) in the vapor phase. It is therefore important to consider the potential for vapor-phase transport of PFAS in soil and the vadose zone and to investigate the processes impacting the retention and transport of volatile PFAS in soil. It is also critically important to evaluate existing models and develop new models as needed for their application to PFAS vapor-phase transport. The objectives of the present work were to provide an overview of vapor-phase transport processes and modeling, with a specific focus on their relevance for PFAS, and to discuss implications for mass discharge to groundwater, vapor intrusion, and soil vapor extraction. Decades of research have been devoted to the retention and transport of legacy volatile organic contaminants in the vadose zone. This work provides an abundant source of information concerning the many factors and processes of relevance, and insights into the development and application of mathematical modeling. However, given the unique properties of PFAS, there is a need to conduct research to investigate vapor-phase transport of PFAS and to develop PFAS-specific models. We highlight with illustrative examples that vapor-phase transport can be significantly more rapid than aqueous-phase advective transport, which can result in enhanced mass discharge to groundwater.

Aquifer vulnerability valorization via DRASTIC index-based assessment within litho-facies of a coastal environment

Determining the degree of an aquifer’s susceptibility to pollutants is an important tool for policy planning in subterranean water administration and conservation. In this work, subterranean water vulnerability was appraised with the use of DRASTIC methodology, which employs seven parameters: depth to groundwater (D); net groundwater recharge (R); aquifer media (A); soil media (S); topography (T); influence of vadose zone (I); and hydraulic conductivity (C). Different ratings were given to each parameter based on the hydro-geological and geo-electrical information obtained from the study area. Geo-electrostratigraphic data was acquired with vertical electrical soundings and electrical resistivity tomography surveys. The results demonstrated the existence of geoelectrical layers with variable resistivities ranging from high to low, with variable curve types. Longitudinal conductance measures indicated moderate subterranean water protective capacity. Analysis of DRASTIC vulnerability indices showed that the aquifer indicated moderate to high vulnerability to contamination. Vulnerability maps were generated to indicate locations of high vulnerability, the goal being to prevent indiscriminate haphazard and wildcat abstraction of groundwater in such locations. The quality category index (QCI) generated for the DRASTIC model indicated that underground water susceptivity is dependent on all 7 parameters employed in the model, with the most critical determinants being the depth to aquifer (D), net recharge (R), aquifer media (A), and impact of the vadose zone (I). The work recommends that anthropogenic activities that could contaminate groundwater resource be halted as the resource is indicated by DRASTIC models as being vulnerable.

Early Warning of Regional Groundwater Pollution： A Case Study for Plain Area of Barkol-Yiwu Basin

Groundwater pollution early warning is an effective means for regional groundwater pollution prevention. The groundwater pollution early warning model coupled with the current situation of groundwater quality, groundwater quality variation trend, and groundwater pollution risk were applied to the plain area of Barkol-Yiwu Basin, and the regional scale groundwater pollution early warning was realized by combining the early warning of groundwater quality status and trend. The TOPSIS method based on comprehensive weight was used to evaluate the current situation of groundwater quality. The variation trend of groundwater quality was analyzed by calculating the trend interpolation results of 18 in-situ groundwater quality monitoring wells. The groundwater vulnerability map, groundwater pollution load map, and groundwater function value map were superimposed using the superposition index method to evaluate groundwater pollution risk. The results showed that the groundwater quality was good and relatively good, and the poor groundwater quality in some areas was mainly affected by the shallow groundwater depth and the large porosity of the vadose zone. Groundwater quality was stable from 2011 to 2022, mainly due to the leakage of wastewater generated by industries and agriculture into groundwater, resulting in the deterioration of groundwater quality in some areas. Groundwater pollution risk was generally low, and the dual effects of high vulnerability and high pollution load of groundwater led to local areas with high pollution risk. The early warning level of groundwater pollution was generally low, and the heavy and highly heavy warning areas accounted for 16.4% and 17.5% of the study area, respectively, mainly distributed in Xiamaya Township of Yiwu County and northern Santanghu Town, Dahongliuxia Township, and Dahe Town of Barkol County. The quaternary sediments exposed were mainly sandy pebbles, with developed pores and strong water permeability. The interception and adsorption capacity of pollutants were weak. Pollutants produced by industries, agriculture, and life easily leaked into groundwater aquifers, resulting in poor groundwater quality and high risk of groundwater pollution, which ultimately led to a high early warning level of groundwater pollution in some areas. The research on early warning of groundwater pollution provided an important theoretical basis for the development of groundwater pollution remediation.