Groundwater最新文献

Microplastic pollution has emerged as a critical issue within the global environmental landscape. Nevertheless, our understanding of the occurrence and distribution of microplastics in groundwater systems remains limited. In this study, we examined the contamination of microplastics in groundwater across Chengdu, located in western China. The findings revealed that the concentration of microplastics varied between 7.0 and 24.0 particles/L. Microplastics measuring less than 1000 μm in size constituted the majority, with granules and fragments being the main shapes. Furthermore, the predominant polymer types included polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polyethylene (PE), and polyamide (PA). The pollution load index showed that all groundwater monitoring stations were contaminated with microplastics. An assessment of the polymeric and pollution risks demonstrated a spectrum of variability, ranging from low- to high-risk levels. An increase in the abundance of microplastics and toxic polymers correlates with elevated potential ecological risk levels associated with these contaminants. This study provides novel insights into the contamination of microplastics in groundwater. The risk assessments establish a foundational baseline for future comprehensive evaluations and the formulation of effective strategies aimed at establishing groundwater quality criteria, as well as pollution control and management.

The Floridan Aquifer System (FAS) is a triple porosity, eogenetic karst aquifer that contains extensive phreatic cave networks embedded in a high permeability carbonate matrix. These unique characteristics create complex flow dynamics that impact residence time distributions within the FAS, which are important to constrain for implementing effective water resource strategies. The impacts of eogenetic karst characteristics on seasonal and longer term hydrological dynamics have been previously evaluated; however, stormflow remains understudied. Our study explores stormflow dynamics at a karst spring in the eogenetic FAS after major Hurricane Idalia made landfall in August 2023. We analyze data from in-situ sensors that collect NO₃-N, specific conductance, and discharge at 15-min intervals to capture potentially small changes in chemistry that could be significant. We coupled the sensor data with grab sample collection of water isotopes and major element chemistry to provide additional details on the stormflow dynamics. Our results show at least two stormflow pulses as evidenced by changes in NO₃-N and confirmed geochemically; albeit the absolute changes in NO₃-N for both stormflow pulses were small (<0.005 mmol). One stormflow pulse was diluted with respect to NO₃-N while the other mobilized NO₃-N. The stormflow pulse that is associated with mobilized NO₃-N was detected for at least 19 days after the rain began from Idalia, indicating long residence times before evacuation from the cave system. Both of the detected stormflow pulses were superimposed on seasonal trends in NO₃-N that are known to occur, whereby it appears storms could amplify NO₃-N seasonal effects. Our results have implications for understanding complex residence times in eogenetic karst aquifers and highlight the influence of the carbonate bedrock matrix on stormflow through the FAS.

Seawater intrusion can cause the freshwater-saltwater interface to move inland toward coastal freshwater aquifers. Sea level rise has become a significant driver of this phenomenon. Installing cut-off walls along coastal aquifers is an effective engineering measure to mitigate seawater intrusion. However, most analyses of groundwater flow under sea level rise, particularly with cut-off walls, primarily rely on numerical methods, with limited analytical approaches available. In this study, we developed mathematical models for groundwater flow induced by sea level rise, dividing the coastal aquifer into offshore and inland regions along the cut-off wall. An unknown flow function was introduced as a boundary condition at the shared boundary. Using homogenization and the finite Fourier transform method, we derived analytical solutions for the two regions separately. A global coupling solution, achieving hydraulic continuity between the two regions, was obtained by applying the collocation method at the shared boundary. The validity of the solution was confirmed through comparisons with finite difference numerical simulations. Furthermore, we analyzed the impacts of factors such as sea level rise amplitude and cut-off wall embedment depth on hydraulic changes. The results indicate that increases in the amplitude of sea level rise significantly amplify hydraulic head changes in the inland aquifers, while deeper embedment of the cut-off wall enhances its effectiveness in preventing seawater intrusion. However, the model does not consider density differences between freshwater and saltwater or the dynamics of the saltwater-freshwater interface.

The presence of chromium (Cr) in groundwater poses a significant threat to human health. However, the lack of testing in many wells suggests that the severity of this issue may be underestimated. In this study, various predictive models, including soft computing techniques such as gene expression programming (GEP), artificial neural networks (ANN), multivariate adaptive regression splines (MARS), and the M5 Tree model, along with random forest (RF) and multiple linear regression (MLR), were employed to estimate geogenic Cr concentrations in groundwater based on geological and geochemical parameters in northeastern Iran. A dataset of 676 Cr concentration measurements was used to train and evaluate the models. Among the methods tested, ANN demonstrated the highest predictive accuracy, followed closely by RF, which provided competitive results. GEP and MARS also showed reasonable performance, while MLR exhibited the weakest accuracy, highlighting the limitations of linear models in addressing complex geochemical processes. The ANN model identified over 600,000 individuals in the central and western regions of the study area as being at significant risk of geogenic Cr contamination in groundwater. The findings underscore the potential of advanced predictive models in groundwater quality management and their applicability in other regions with similar challenges.

Understanding which hydrological data types provide the most valuable information for models is crucial, given the limitations of data availability. This study applies data worth analysis to evaluate the impact of various observation types on predictive uncertainty in a coupled SWAT-MODFLOW-RT3D model simulating water flows and nitrate transport in a small headwater catchment in New Zealand. We assessed the worth of continuous nitrate concentrations, in-catchment flow measurements, and SkyTEM-derived groundwater levels for predicting stream flow and in-stream nitrate concentrations. Using PEST software for model calibration and linear uncertainty analysis, we determined the relative worth of different observation types. Results indicate that SkyTEM estimates of groundwater levels and continuously measured nitrate concentrations were particularly effective in reducing predictive uncertainty. This study highlights the value of integrating high-resolution SkyTEM data into models to enhance prediction accuracy for groundwater levels, stream flow, and nitrate pollution. It also demonstrates nitrate's utility as an environmental tracer, refining our understanding of surface water–groundwater interactions and solute transport in the Piako Headwaters Catchment.

Coastal shallow groundwater is susceptible to adverse sea-level rise (SLR) impacts. Existing research primarily focuses on SLR-induced salinization of coastal aquifers. There is limited understanding of the magnitudes and rates of water table rise in response to SLR, which could lead to groundwater flooding and associated infrastructure challenges. This study used a variable-density groundwater flow model to quantify the transient movement of the water table in response to various SLR scenarios and rates, considering a range of aquifer parameters for both fixed-head and fixed-flux inland boundary conditions. The SLR scenario based on realistic and progressive SLR projections resulted in a smaller water table rise than the instantaneous or gradual SLR scenarios at 100 years, despite a final identical SLR. Rates of water table rise were always less than SLR, decreased with distance from the coastline, and were proportional to SLR. The magnitude and rate of water table rise in response to SLR were largest for fixed-flux conditions. It also took longer for the rate of water table rise to equilibrate after the commencement of SLR for fixed-flux conditions than for fixed-head conditions. As such, fixed-flux conditions represent a greater hazard for water table rise, and the maximum impact may not be experienced for decades. This delayed response poses challenges to planners and managers of coastal groundwater systems. Introducing a drain reduced water table rise more on the inland side of the drain than on the coastal side. Subsurface infrastructure may limit SLR impacts, but further effects need to be carefully considered.

An ongoing major challenge faced in portions of the western United States is to stop the decline of aquifers that are hydraulically connected to rivers. As these aquifers decline, streamflow is depleted, resulting in impacts to agriculture, environmental flows, and hydropower production. In 2014, the Idaho Water Resource Board initiated an aquifer recharge program, and in 2015 a historic settlement agreement (hereafter referred to as the Settlement Agreement) was signed by surface water users with senior water rights and groundwater pumpers with junior water rights to stop the decline of the eastern Snake Plain Aquifer (ESPA) in southern Idaho (SWC-IGWA 2015). Here, we assess mitigation measures they have undertaken to reverse the downward trajectory of groundwater levels in the ESPA using drought indices correlated to the combined head change of a suite of groundwater monitoring wells. The results were then compared against the predictions of the Enhanced Snake Plain Aquifer Model (ESPAM), which is a MODFLOW-based aquifer model. The drought indices indicate that without the aquifer recharge program and reductions in groundwater pumping, the aquifer head would have been 1.1 to 1.3 m lower than observed in 2023, indicating implemented water management practices reduced the volumetric loss to the aquifer by 2500 million cubic meters (2,000,000 acre-feet). The result, therefore, implies that Idaho water users and managers have succeeded in changing the trajectory of ESPA water levels.