Groundwater Risk Research Articles

Two-dimensional Monte Carlo simulation coupled with multilinear regression modeling of source-specific health risks from groundwater.

Effective protection of groundwater requires an accurate health risk assessment of contaminants; however, the diversity of pollution sources, variability, and uncertainties in exposure parameters present significant challenges in this assessment. In this study, groundwater risk estimates associated with NO3-, and F-, along with fourteen heavy metal(loid)s (V, Cr, Mn, Fe, Ni, Cu, As, Co, Cd, Se, Pb, Hg, Zn, and Al) in an agricultural area were optimized by implementing positive matrix factorization (PMF), multilinear regression, and two-dimensional Monte Carlo simulations to characterize source-specific health risks. Groundwater pollution was analyzed considering regional variations, including differences in elevation, land use and land cover, and soil types. Three pollution sources were identified: agricultural practices, traffic, and natural processes. Moreover, the results revealed NO3- from an agricultural source as the primary control contaminant. Additionally, both adults and children in the study area face significant non-carcinogenic health risks. To mitigate these risks, this study recommends maximum consumption levels of 1.44 L/day for adults and 0.35 L/day for children. Furthermore, adults weighing > 68.1 kg and children weighing > 15.9 kg are likely to be at reduced risk of experiencing adverse health effects. Compared to deterministic health risk assessment and one-dimensional Monte Carlo simulation of health risks, two-dimensional Monte Carlo simulation showed improved performance, providing better accuracy and higher precision in health risk assessment results. Thus, this research is expected to enhance the understanding of health risk assessment related to groundwater and to provide valuable guidance for managing groundwater pollution.

Groundwater Risk Intensity Map through Modified DRASTIC Model in the Rania Basin, Kurdistan Region of Iraq

Groundwater Risk Intensity Map through Modified DRASTIC Model in the Rania Basin, Kurdistan Region of Iraq

Hydrogeochemical characteristics, source distribution, and health risk of high-fluoride groundwater in Swabi, Pakistan.

This paper evaluated fluoride (F-) pollution in drinking groundwater sources, which causes severe fluorosis and other human health concerns in Swabi, Pakistan. We determined F- concentration, prevalence, enrichment, distribution, and health hazards from water ingestion in Swabi, Pakistan. Therefore, 126 groundwater and 18 surface water samples were collected to analyze F- and other geochemical tracers to understand groundwater enrichment and F- mobilization in aquatic systems. The range and mean values of F- in groundwater were 0.02 to 14.2 and 4.0mg/L, and those in surface water were 1.12-0.8 and 1.4mg/L. Most residents used groundwater for drinking purposes. Thus, groundwater results showed that 72.2% of samples had surpassed the WHO guidelines of F- 1.5mg/L. The fluoride pollution index (FPI) declared that 48.73% of samples showed a higher risk, 41.95% medium risk, and 9.32% lower risk. Mineral phases using PHREEQC interactive software determined mineral saturation revealing the dissolution of host rock minerals and unsaturation showed precipitation of minerals within the aquifer. The principal component analysis multilinear regression (PCA-MLR) model showed a five-factor solution: (a) geogenic processes, (b) mixed geogenic and anthropogenic inputs, (c) geochemical processes, (d) agriculture pollution, and (e) industrial effluents which would release F- in the aquifer. The health hazard due to higher F- revealed that children showed high-risk levels compared to adults in endemic areas. The spatial distribution of F- in drinking groundwater increases towards the northern side and decreases in the south to the southeastern side. Therefore, effective water management techniques would be required to safeguard groundwater resources and secure human health from dental and skeletal fluorosis and other associated problems caused by high F- groundwater with varying fluoride concentrations. This study will help the water management authority to safeguard depleted groundwater for drinking demands.

Spatiotemporal distributions, sources, and health risks of heavy metals in an acid mine drainage (AMD)-contaminated karst river in southwest China

Acid mine drainage (AMD), characterized by its acidity and high content of heavy metals, is a significant global environmental problem that harms human health through its impact on rivers. Therefore, this study aims to identify heavy metals in both surface and underground AMD-polluted karst rivers, focusing on the Zhijin River area which is severely affected by AMD, and assess their health risks to residents. Through the collection of 30 surface water samples and 16 groundwater samples from both wet and dry seasons, the study examines the concentration, sources of pollution, and health implications of six heavy metals (Fe, Mn, Cr, Cd, As, and Hg). The results showed that Fe and Mn levels in surface water were highly polluted during both seasons, especially during the wet season, with Fe levels reaching 20.0 mg/L and Mn levels reaching 1.9 mg/L. Further correlation and principal component analyses revealed that mining activities are the primary contributors to the contamination in this region. Health risk assessments and Monte Carlo simulation, including both deterministic and probabilistic, showed that the noncarcinogenic health risk indices for surface water and groundwater were within acceptable limits for both seasons. However, groundwater poses a higher carcinogenic risk to children, with As levels during the wet season and Cr levels during the dry season warranting close monitoring. Factors such as body weight and intake rate played a crucial role in health risk evaluations. This study underscores the need for further attention to groundwater risk, temporal heterogeneity in the Zhijin River.

Heavy metal contamination assessment and source attribution in the Vicinity of an iron slag pile in Hechi, China: Integrating multi-medium analysis

Heavy metals, such as mercury, cadmium, and nickel, may contaminate human inhabited environments, with critical consequences for human health. This study examines the health impacts of heavy metal pollution from an iron slag pile in Hechi, China, by analyzing heavy metal contamination in water, sediment, soil, and crops. Here, the Nemerow pollution index (NI) indicated severe pollution at most sampling sites, the mean NI of groundwater, and surface water had reached 594.13 and 26.79, respectively. Bioaccumulation of mercury (Hg), cadmium (Cd), and nickel (Ni) was noted in crops, cucumbers showed comparatively lower risk levels. Logarithmic surface water-sediment partition coefficient calculations indicated that heavy metals such as chromium (Cr), ferrum (Fe), zinc (Zn), copper (Cu), Ni, arsenic (As), and lead (Pb) tend to accumulate in sediments. There was a high risk in groundwater (67.48–6590.54) and surface water (13.73–2500.85). Variably influenced by rainfall, these metals can be diluted and mobilized from surface water and sediments, thereby changing the contamination levels and ecological risks. Probabilistic health risk assessments indicated that health risks were higher in children than in adults, the mean total carcinogenic risk values of soil, groundwater, and surface water, were 6.79E-04, 4.20E-06, and 1.15E-6 for children, respectively. Moderate soil pollution is the main health hazard. A Positive Matrix Factorization model attributed over 60% of the pollution to slag stacking. Biotechnologies, solidification/stabilization techniques, field management, and institutional controls, driven by principles of green, low-carbon, and economic efficiency may mitigate. These findings contribute to the management of heavy metal pollution in iron slag pile areas.

Appraisal of contamination, hydrogeochemistry, and Monte Carlo simulation of health risks of groundwater in a lithium-rich ore area.

This study incorporated hydrogeochemical facies, the entropy-weighted water quality index (EWQI), multivariate statistics, and probabilistic human exposure assessment to investigate hydrogeochemistry, analyze groundwater quality, and estimate potential risks to human health in a lithium-rich ore area (Jadar River basin, Serbia). The findings designated the Ca·Mg-HCO3 hydrogeochemical type as the predominant type of groundwater, in which rock weathering and evaporation control the major ion chemistry. Due to the weathering of a lithium-rich mineral (Jadarite), the lithium content in the groundwater was very high, up to 567mg/L, with a median value of 4.3mg/L. According to the calculated EWQI, 86.4% of the samples belong to poor and extremely poor quality water for drinking. Geospatial mapping of the studied area uncovered several hotspots of severely contaminated groundwater. The risk assessment results show that groundwater contaminants pose significant non-carcinogenic and carcinogenic human health risks to residents, with most samples exceeding the allowable limits for the hazard index (HI) and the incremental lifetime cancer risk (ILCR). The ingestion exposure pathway has been identified as a critical contaminant route. Monte Carlo risk simulation made apparent that the likelihood of developing cancerous diseases is very high for both age groups. Sensitivity analysis highlighted ingestion rate and human body weight as the two most influential exposure factors on the variability of health risk assessment outcomes.

Assessments of hydrogeochemical characteristics, water quality, and health risk of groundwater of Chapi-Nawabganj District of Bangladesh

ABSTRACT A total of 60 groundwater samples were collected over three seasons, aiming to assess hydrochemical characteristics, water quality, pollution level, and health risk. The concentration of Fe, Mn, and Pb exceeded almost 100% of samples in three seasons. The groundwater was found to be highly contaminated with Cd and Cr in the pre-monsoon and Ni in the monsoon. The order of major ion and trace metal concentrations is as follows: Ca2+ > Na+ > Mg2+ > K+; HCO3− > Cl− > SO42− > NO3− > PO43−, and Fe > Mn > Pb > Cd in three seasons. The groundwater was Ca-Mg-HCO3− type. The study suggests that the contamination sources are mostly geogenic as well as slightly anthropogenic. The water–rock interactions are the dissolution of calcite and dolomite, along with silicate weathering, which controls the hydrochemistry of the groundwater. The indices, including the Water Quality Index (WQI), and the Canadian Council of Ministers of the Environment (CCMEWQI), revealed that the groundwater quality in the area was moderately polluted. The Heavy Metal Pollution Index (HMPI) and human health risk assessment (HRA) illustrated that groundwater is a significant health hazard, indicating it is unsuitable for human consumption and suggesting treatment before drinking.

Simulation of bench-scale CO2 injection using a coupled continuum-discrete approach

Unintended releases of CO2 from carbon capture and storage operations presents the risk of atmospheric emissions and groundwater or surface water quality impacts. Given the potential impacts, it is valuable to have tools capable of predicting groundwater concentrations and likely pathways of CO2 migration in the subsurface. Traditional multiphase flow models struggle to simulate the discontinuous flow expected at leakage sites. This work applied a coupled continuum-discrete model, ET-MIP, to simulate a bench-scale injection of CO2. Results demonstrate the capability of ET-MIP to accurately capture gas fingering behaviour, and the complexity of multicomponent mass transfer observed in the experiment. Simulations were computationally efficient, allowing for the use of multiple displacement pressure realizations. CO2 migration in the subsurface was shown to be sensitive to mass transfer, as i) increased groundwater velocity can dissolve leaked CO2 prior to reaching the surface and ii) background dissolved gases in the subsurface can impact the rate of upwards gas movement, gas distribution, and the composition and persistence of the gas phase. The sensitivity to mass transfer suggests it may be preferable to monitor for low-solubility gases in the source mixture rather than CO2. These findings are applicable to other gases in the subsurface, such as hydrogen or methane migrating from geoenergy wells.

Radioactivity Levels, Spatial Distribution, and Radiological Risk Assessment of 226Ra, 228Ra, 40K, and 3H in Water Samples from Dhaka City and Savar, Bangladesh.

This investigation was conducted to measure the radioactivity levels of 226Ra, 228Ra, 40K, and 3H in the 13 most popular branded bottled mineral water (BMW), 12 groundwater sources consumed in Dhaka city, Bangladesh, and six water samples collected from the nuclear object site at Savar, adjacent to Dhaka. The activity of 3H was measured by using a liquid scintillation counter, and a gamma-ray spectrometer with an HPGe detector was used to measure the activity of other radionuclides. The average activity concentrations of 226Ra, 228Ra, 40K, and 3H in BMW samples and groundwater were found to be 1.81 ± 0.43, 1.74 ± 0.40, 43.08 ± 6.23, 2.42 ± 0.16, and 1.61 ± 0.51, 1.69 ± 0.45, 57.42 ± 3.16, and 3.02 ± 0.19 Bq/L, respectively. In addition, the activity concentrations of identified radionuclides in water samples collected from Savar were found to be 1.59 ± 0.43, 1.53 ± 0.50, 99.83 ± 3.05, and 2.95 ± 0.20 Bq/L. With the exception of 3H, the activity concentration and the annual effective dose of 40K, 226Ra, and 228Ra surpassed the acceptable thresholds of the WHO. The combined activity of radium (Rac) also exceeds the USEPA recommended maximum permissible limit of 0.185 Bq/L. The excess lifetime cancer risk results were below the permissible threshold of 10-3 for radiological risks. Groundwater was subjected to an AAS analysis for common metals (Na, Mg, and Ca) and heavy metals (Fe, Cr, Cu, and Pb). The results showed that the heavy metals were below the detection limit. Radionuclide contents in groundwater of Dhaka city were mapped spatially using a GIS technique. Statistical analyses such as one-way ANOVA, one sample t test, and Pearson's correlation analysis were also performed. According to Pearson's correlation analysis, 228Ra is mostly responsible for radiation risk in BMW and groundwater.

Hydrogeochemical properties, source provenance, distribution, and health risk of high fluoride groundwater: Geochemical control, and source apportionment

This study evaluated high fluoride (F−) levels, source distribution, provenance, health risk, and source apportionment in the groundwater of Sargodha, Pakistan. Therefore, 48 groundwater samples were collected and analyzed by ion-chromatography (DX-120, Dionex). The lowest concentration of F− was 0.1, and the highest was 5.8 mg/L in the aquifers. In this study, 43.76% of the samples had exceeded the World Health Organization's allowable limit of 1.5 mg/L. The hydrogeochemical facies in Na-rich and Ca-poor aquifers showed NaCl (66.6%), NaHCO3 (14.5%), mixed CaNaHCO3 (8.3%), CaCl2 (8.3%), mixed CaMgCl2 (2%), and CaHCO3 (2%) type water. Alkaline pH, high Na+, HCO3− concentrations, and poor Ca-aquifers promoted F− dissolution in aquifer. The significant positive correlations between Na⁺ and F− suggested cation exchange, where elevated Na⁺ occurs in Ca-poor aquifers. The cation exchange reduces the availability of Ca2+ would lead to higher F− concentrations. Meanwhile, the correlation between HCO₃- and F− indicates that carbonate minerals dissolution helps in increasing pH and HCO₃- as a result F− triggers in aquifers. Groundwater chemistry is primarily governed by the weathering of rock, water-rock interaction, ion-exchange, and mineral dissolution significantly control groundwater compositions. Cluster analysis (CA) determined three potential clusters: less polluted (10.4%), moderately polluted (39.5%), and severely polluted (50%) revealing fluoride toxicity and vulnerability in groundwater wells. Mineral phases showed undersaturation and saturation determining dissolution of minerals and precipitation of minerals in the aquifer. PCAMLR model determined that high fluoride groundwater takes its genesis from F-bearing minerals, ion exchange, rock-water interaction, and industrial, and agricultural practices. The health risk assessment model revealed that children are at higher risk to F− toxicity than adults. Thus, groundwater of the area is unsuitable for drinking, domestic, and agricultural needs.

Geochemical Insights into Heavy Metal Contamination and Health Hazards in Palar River Basin: A Pathway to Sustainable Solutions

The pollution of groundwater by heavy metals is becoming an increasingly urgent problem due to the rapid growth of industrialization and urbanization. A detailed geochemical investigation of physicochemical properties and heavy metal contamination was conducted on 140 groundwater samples in the Vellore district around the Palar River, Tamil Nadu, India, to assess the metal index risk in groundwater. The water quality is significantly contaminated with Cr, Co, Cu, Cd, and Fe, and moderately contaminated with Mn, Ni, and Zn, according to the groundwater assessment using the heavy metal index, contamination factor, and Igeo index. This contamination is associated with various health problems, including mental illness, stomach and skin cancer, liver failure, and kidney damage. Based on contour maps created with GIS, most of the region is heavily contaminated with heavy metals, rendering the groundwater unfit for human consumption. The Health Risk Assessment Index (HRAI) rose to 9028.6, indicating an extremely high health risk. In addition to identifying the extent of contamination, the study also proposes sustainable solutions to mitigate these risks. These include the adoption of advanced water treatment technologies, the promotion of green chemistry practices in local industries, the establishment of stricter regulatory frameworks, and the implementation of community-based water management strategies. These measures are essential to ensuring safe drinking water and achieving Sustainable Development Goal 6 (SDG 6). The findings underscore the urgent need for comprehensive monitoring and proactive remediation strategies in industrially contaminated regions.

Source-oriented health risk assessment of groundwater based on hydrochemistry and two-dimensional Monte Carlo simulation

Accurately assessing the health risks posed by major contaminants is essential for protecting groundwater. However, the complexity of pollution sources and the uncertainty of parameters pose challenges for quantitative health risk assessment. In this study, a source-oriented groundwater risk evaluation process was improved by screening key pollutants, employing a combined hydrochemical and positive matrix factorization (PMF) approach for source apportionment, and incorporating two-dimensional Monte Carlo simulation for risk characterization. The application of this process to groundwater assessment in Central Jiangxi Province identified NO3-, F-, Se and Mn as the key pollutants. The pollution sources were anthropogenic activities, rock dissolution, regional geological processes, and ion exchange. Anthropogenic sources contributed 36.8 % and 28.8 % of the pollution during the wet season and dry season, respectively, and accounted for more than half of the health risks. NO3- from anthropogenic sources was the primary controlling pollutant. Additionally, the risk assessment indicated that children were at the highest health risk during the dry season, with ingestion rate suggested to be controlled below 1.062 L·day−1 to make the health risk within an acceptable range. The improved assessment methodology could provide more accurate results and recommended intakes.

Subchronic Effects of Tetrachloroethylene on Two Freshwater Copepod Species: Implications for Groundwater Risk Assessment.

Aliphatic chlorinated hydrocarbons, notably tetrachloroethylene (also known as perchloroethylene [PCE]), are persistent, mobile, and toxic (PMT) and/or very persistent, mobile, and toxic (vPMT) groundwater pollutants, often exceeding safe drinking water thresholds. The present study delves into the groundwater risk assessment of PCE with a novel focus on the sensitivity of stygobitic species-organisms uniquely adapted to groundwater environments. Through a comparative analysis of the subchronic effects of PCE on the locomotion behavior of two copepod species, the stygobitic Moraria sp. and the nonstygobitic Bryocamptus zschokkei, we highlighted the inadequacy of the current European predicted-no-effect concentration of PCE for groundwater ecosystems. Our findings indicate significant behavioral impairments in both species at a concentration (32 ng/L PCE) well below the threshold deemed safe, suggesting that the current European guidelines for groundwater risk assessment may not adequately protect the unique biodiversity of groundwater habitats. Importantly, B. zschokkei demonstrated sensitivity to PCE comparable to or greater than that of the target stygobitic species, suggesting its utility as a substitute species in groundwater risk assessment. The present study adds to the limited research on the ecotoxicological sensitivity of groundwater species to PMT/vPMT chemicals and highlights the need for refined groundwater risk-assessment methodologies that consider the susceptibilities of stygobitic species. Environ Toxicol Chem 2024;43:2515-2527. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Precise management and control around the landfill integrating artificial intelligence and groundwater pollution risks

The Landfill plays an important role in urban development and waste disposal. However, landfill leachate may also bring more serious pollution and health risks to the surrounding groundwater environment. Compared with other areas, the area around the landfill needs more precise management. To solve this problem, based on the “pressure-state-response” framework, a method for the identification and evaluation of groundwater pollution around the landfill was constructed. The LPI method was used to assess the contamination potential of the leachate. The comprehensive quality of groundwater was evaluated by the entropy-AHP water quality assessment method, sodium adsorption ratio and sodium percentage. The probabilistic health risks of groundwater were assessed based on a Monte Carlo algorithm. The sources of pollutants were identified by comprehensively using the PCA-APCS-MLR model and the PMF model. Finally, the self-organizing map algorithm and the Kmeans algorithm were integrated to enhance the precision of groundwater management and control measures. The results showed that the leachate of the landfill was in the mature stage, and the concentration of inorganic substances was relatively high. Leachate had the potential to contaminate surrounding groundwater. The groundwater quality of 68.14% of the study area was in the poor or lower level. The groundwater near the landfill was unsuitable not only for drinking but also for irrigation purposes. Cl− was the main non-carcinogenic risk factor. Reducing pollutant concentration and controlling exposure time are effective strategies for mitigating health risks caused by high-concentration pollutants (Cl−, NO3−) and low-concentration pollutants (F−), respectively. The groundwater around the landfill was jointly affected by six pollution sources. The PMF model has better analytical ability in mixed pollution areas. The groundwater in the study area was divided into five clusters, of which cluster Ⅰ was significantly affected by leachate, and cluster Ⅴ had the lowest pollution and health risk.

Multi-contamination groundwater risk assessment based on integrated OSPRC framework considering receptor and consequence components

This study evaluates the risks associated with geogenic and anthropogenic contaminants in the Azarshahr aquifer situated in the Lake Urmia watershed in NW Iran, an area critically affected by both natural mineral deposits and intensive agricultural activities. This region, characterized by its significant geological diversity and extensive use of pesticides and fertilizers, presents a unique opportunity to study the interaction between natural and human-induced groundwater contamination. Employing the Origin-Source-Pathway-Receptors-Consequence (OSPRC) framework, the research focuses on the linkage between these contaminants and waterborne diseases, particularly examining the less-studied “Receptor” and “Consequence” components using the Groundwater Quality Index (GQI) and health risk indices. Our approach integrates vulnerability assessments through the DRASTIC and SPECTR methods, enhanced by Sugeno fuzzy logic, to produce a detailed risk map highlighting two critical zones: Risk Cell 1, impacted predominantly by agricultural contaminants including nitrate and chlorpyrifos, and Risk Cell 2, affected by geogenic contaminants such as arsenic, lead, nickel, and chromium. This comprehensive analysis not only maps out the source and migration pathways of these contaminants but also evaluates their impact on human health. The findings underscore a strong correlation between identified risks and health impacts, emphasizing the pressing need for targeted health interventions and improved management of water resources in the region. By advancing the application of the OSPRC framework, this research fills a vital gap in our understanding of aquifer contamination dynamics and sets a new standard for future groundwater risk assessments.

Coordinated analysis of groundwater spatiotemporal chemical characteristics, water quality, and potential human health risks with sustainable development in semi-arid regions.

The emergence of large-scale time-series data and advancements in computational power have opened new avenues for analyzing the spatiotemporal evolution of groundwater chemistry, water quality, and human health risks. This paper utilizes hydrogeochemical methods to elucidate the controlling factors of water chemical components based on the test results of 124 groundwater samples collected from 31 monitoring wells in Fuxin City, Liaoning Province, China, from 2018 to 2021. By integrating the Random Forest and Enhanced Water Quality Index methods for water quality assessment and employing the Human Health Risk Assessment (HHRA) model to analyze human health risks, our findings indicate that the groundwater is mildly alkaline, with SO4·Cl-Ca·Mg and HCO3-Ca·Mg as the dominant hydrochemical types, primarily derived from the dissolution of carbonate and silicate minerals such as dolomite, limestone, and andesite, and cation exchange reactions. The EI_RF water quality evaluation model reveals that the overall water quality in the study area is poor, with Class I and II water quality zones mainly located in the northeastern and central parts of the study area, showing a gradual transition from Class I and II in the northeast to Classes IV and V in the southwest, significantly influenced by NO3-, TH, TDS, and SO42-. The HHRA model results indicate that the potential non-carcinogenic risk of groundwater nitrates has a severe impact on infants, with the spatial distribution being low in the northeast and high in the southwest. Due to industrial activities, agricultural practices, and population growth, certain areas in developing countries such as China and India exhibit nitrate concentrations significantly higher than those in most international regions, highlighting global environmental and public health challenges. This underscores the importance of enhancing groundwater monitoring and implementing measures to mitigate pollution. These research outcomes hold significant implications for the government in formulating rational protection and management measures to ensure the sustainable utilization of groundwater resources.

Assessment of groundwater vulnerability and risk to pollution in Con Dao island, Ba Ria - Vung Tau, Vietnam

Abstract The assessment of groundwater vulnerability has been widely used to manage and prevent groundwater from contamination risk. This study applied the model of GIS-based GALDIT was for groundwater vulnerability and risk assessment in a coastal district of Con Dao island, Ba Ria-Vung Tau, Vietnam. The Groundwater Risk Assessment Model (GRAM) was used to assess the risk of groundwater pollution in the study region. The GALDIT model used six hydrogeological components to generate a GALDIT Index map, which illustrates how vulnerable the local groundwater is to contamination. The platform of GIS-based GRAM was exploited to construct risk maps related to salinity intrusion, hazard release, and hazard consequences. According to the findings, more than 80% of the groundwater in Con Dao district is vulnerable to saltwater intrusion, with the greatest concentration in the district’s central section. Only 18.12% of the district, in the Co Ong region to the northeast of the Con Dao district, has low or very low susceptibility. However, after accounting for contamination barriers and the capacity to identify and detect risks, it was shown that most areas, or around 87% of the study area, had transitioned to a low-risk level of groundwater pollution. The groundwater vulnerability and risk maps created serve as baseline information for decision-makers in governance and planning to effectively monitor and protect groundwater resources from pollution.

Regional Assessment of Groundwater Contamination Risk from Crude Oil Spillages in the Niger Delta: A Novel Application of the Source-Pathway-Receptor Model

AbstractOnshore oil spills are known for their disastrous environmental impacts and potential to cause lasting damage to underlying groundwater. The Niger Delta is particularly vulnerable to widespread spillages linked to extensive oil exploration, transportation, and theft-related incidents. This research employed a geospatial approach in formulating risk equations, based on the source-pathway-receptor (S-P-R) model using multiple openly available data sets, to assess groundwater contamination risk in the Niger Delta Region (NDR), Nigeria. To develop the overall risk equation, the study combined fourteen thematic data layers including the volume of oil spilled, type of spill, slope, elevation, proximity to spill site, pipeline, oil wells and streams, drainage density, mean annual precipitation and population density. These layers were integrated into source potency, pathway transmissivity, and receptor susceptibility. The NDR was systematically categorized into low, moderate, and high groundwater risk zones. The delineation revealed that high-risk zones predominantly span the central areas, extending from southeast to northwest, effectively encircled by regions of low to medium risk located in both the northern and southern extents of the delta. The efficacy of the risk model was corroborated by existing knowledge. Moderate to high-risk zones were found to be in about 16% of the NDR, revealing previously unknown areas of risk. This spatial configuration underscores a significant gradient in contamination risk across the NDR, with the central corridor emerging as a critical focus for groundwater protection and remediation efforts. In line with UN Sustainable Development Goal (SDG) #6, this study recommends targeted strategies to ensure clean water provision in these identified high-risk areas. By leveraging the S-P-R model within this complex and sensitive ecological area, this research both advances environmental risk assessment and sets a precedent for future large-scale environmental risk assessments utilizing open-source data.

Solar-powered irrigation in Nepal: implications for fossil fuel use and groundwater extraction

In recent years, use of solar-powered irrigation pumps (SIPs) has increased significantly in the agricultural plains (terai) of Nepal. Federal and local governments there have subsidized the pumps in an effort to expand irrigated agriculture using renewable energy. We use data from a cross-sectional survey of 656 farming households in the terai to examine how SIPs affect fossil fuel use and groundwater extraction. We find that most SIP users continued to use their fossil-fuel pumps, as very few completely replaced them with solar pumps. Farmers who received SIPs operated their irrigation pumps more hours than those who did not receive SIPs. Taken together, these findings suggest that groundwater use has increased, as SIP recipients ‘stack’ their pumps. We also find that solar pumps were more likely to be owned by richer households and those with better social networks than those who were poorer and had relative social disadvantage. As Nepal expands the use of solar pumps in agriculture, policy efforts may benefit from managing expectations about the carbon-mitigation potential of this technology, managing groundwater risks as SIP use expands, and making SIPs more inclusive.

Assessment of spatiotemporal risks for nationwide groundwater nitrate contamination

National assessments of groundwater contamination risks are crucial for sustaining high-quality groundwater supplies. However, traditional methods often treat groundwater contamination risk as a steady-state indicator without considering spatiotemporal variation in risk, both geographically and over time, caused by anthropogenic and climatic factors. In this work, XGBoost, a tree-based algorithm, was applied to comprehensively analyze the drivers of groundwater contamination from nitrate, using data on 13 physical features (as used by the index-based ranking method DRASTIC) and 30 anthropogenic features from 1985 to 2010 in the contiguous United States (CONUS). The results indicate that physical features controlling the transport processes, particularly those affecting contaminant travel time from land surface to groundwater (depth to water table and transmissivity), were the dominant factors for nitrate contamination in groundwater. This was followed by features representing the potential nitrogen loading. Positive correlations between most features and the nitrogen loading time (year) were found, suggesting their growing influence on contamination risk. Based on the drivers identified for nitrate concentrations exceeding 10 mg/L in groundwater and their varying temporal contributions, this study proposes a reformulated index-based method for contamination risk assessment. With this method, an overall accuracy of around 70 % was achieved based on the validation data set. The predicted high-risk areas are mainly intensive irrigation regions, such as the High Plains, northern Midwest, and Central Valley. This new approach contributes to a more accurate and effective assessment of the contamination risks of groundwater on a regional and national scale under temporally varying environmental conditions.