Groundwater Degradation Research Articles

Hydrochemical Characteristics, Controlling Factors and Water Quality Evaluation of Groundwater Quality in Kono, Sierra Leone

Groundwater is a major source of drinking water and is considered an imperative component of the accessible water assets across Sierra Leone and many parts of the world. The degradation of groundwater can jeopardize drinking water availability and human health. 29 groundwater monitoring samples with 16 water quality parameters were analyzed. Descriptive statistics, Piper plots, Arc GIS spatial interpolation, Gibbs plots, ion ratio analysis, Wilcox diagram, water quality index (WQI), and entropy-weighted water quality index (EWQI) were used to investigate the hydrochemical characteristics, controlling factors and evaluate the groundwater quality in the study area. The results revealed that the groundwater mean concentration of NO3− in the mining concession was 34.00 mg/L which was above the permissible limit, Ca2+ and HCO3− are higher in the Koidu community compared to the mining concession water, indicating weakly alkaline with dominant anions and cations of HCO3− and Na+ + K+ respectively, and the hydrochemical types were mainly HCO3−·Ca2+ and HCO3− ·Na+. The order of anion concentration in groundwater was HCO3− > NO3− > SO42− > Cl− and HCO3− > SO42− > NO3− > Cl− in the mining concession and the Koidu community respectively. Cations were Ca2+ > Na+, K+ > Mg2+ > Fe²⁺, and Ca2+ > Na+ > Mg2+ > K+ > Fe²⁺ in the mining concession and the Koidu community respectively. The interpretation of WQI and EWQI analysis exhibits 55.17% excellent, 17.24% good, 20.69% medium, 6.90% very poor, and 27.59% excellent, 24.14% good, 34.48% medium, 3.45% poor, and 10.34% very poor water respectively. Most of the sampling sites display similar trends to the WQI and EWQI. The solute source of groundwater was mainly controlled by water-rock interaction, cation exchange and the weathering of silicate and carbonate rocks were jointly the main contributors to the formation of the chemical components of groundwater in the study area, among which the main controlling factors of the groundwater were leaching, precipitate concentration and anthropogenic activities, and sulfate rock and carbonate rock dissolution. The overall water quality in the study area was suitable for human consumption but was polluted to an insignificant extent by mining activities. This study provides theoretical support and a decision-making basis for developing, utilizing, and protecting water resources in the study area.

Degradation of PFOA solutions and PFAS-contaminated groundwater using atmospheric non-thermal plasma treatment

ABSTRACT Per- and polyfluoroalkyl substances (PFASs) can be found ubiquitously in the environment due to their large-scale use, and they pose risks to both ecosystems and human health. These pollutants are highly persistent, making them difficult or impossible to break down with standard processing methods. Therefore, the focus of this research is to explore an alternative approach to reduce PFAS-contaminated water by investigating the breakdown of these pollutants using atmospheric non-thermal plasma (NTP) technology. The experiments tested PFOA standard solutions with varying parameters, including different oxygen and nitrogen ratios as feeding air, with or without a cooling system, and at different time exposures. The process showed energy efficiency being ranged from 0.31 to 15.31 mg/kWh. Chemical analysis of treated samples confirmed the reactor's suitability for PFAS degradation, achieving a 63.75% reduction in initial PFOA concentration after 2 h of plasma treatment. Furthermore, degradation products such as PFHpA, PFHxA, PFPeA, and PFBA were identified after plasma treatment. Overall, these results suggest that plasma-based technology is a promising approach for treating PFAS-contaminated water.

Evaluating The Potential of Hibiscus Rosa-Sinensis in Floating Wetland for The Remediation of Water Bodies Polluted with Domestic Sewage

The inadequate infrastructure for wastewater treatment in many regions has led to the contamination of surface water bodies and groundwater degradation. To address this issue, floating wetland treatment systems have emerged as a viable alternative for effective wastewater remediation. This study focuses exclusively on utilizing Hibiscus rosa-sinensis, a tropical ornamental plant, within the context of floating wetland treatment techniques for the remediation of domestic wastewater. The primary objective is to assess the nutrient and pollutant removal efficiency of Hibiscus rosa-sinensis in a laboratory-scale floating wetland system. Healthy Hibiscus rosa-sinensis plants were cultivated on identical floating rafts and placed in plastic tanks filled with domestic sewage for experimental investigation. Water quality analyses were conducted regularly, spanning 0, 3, 5, 10, 15, 20, and 25 days HRT. The results of this experimental investigation revealed that Hibiscus rosa-sinensis, when used in floating wetland treatment, exhibited significant removal efficiencies for various parameters, including turbidity, total suspended solids (TSS), total phosphorus (TP), ammonia, and dissolved oxygen (DO).These findings highlight the potential of Hibiscus rosa-sinensis plants as a practical component of floating wetland systems for removing nutrients and pollutants from domestic wastewater. This research underscores the viability of Hibiscus rosa-sinensis as a sustainable and environmentally friendly solution to address water pollution challenges, particularly in the context of floating wetland treatment.

Investigating the influence of thermal evaporation method on the heavy metal pollution index (HPI) of groundwater

Groundwater plays a substantial role in satisfying freshwater demand for different purposes worldwide. The degradation of groundwater by various industrial and anthropogenic activities has become a significant problem in recent times. Specifically, the intrusion of heavy metal substances into the groundwater aquifers through industrial effluents is a critical concern. Therefore, the evaluation of groundwater quality has become the need of the hour in order to guarantee the sustainable and secure utilization of freshwater for farming, commercial, and, most importantly, domestic applications. In this study, the groundwater quality and the Heavy Metal Pollution Index (HPI) of an industrial area in Tamil Nadu, India, called ‘Thoothukudi’, have been evaluated in order to determine the influence of industrial activities on the groundwater quality. In total, ten groundwater samples were accessed from the borewells located near the major industrial areas. The parameters, namely pH, total hardness (TH), electrical conductivity (EC), chromium (Cr), copper (Cu), nickel (Ni), iron (Fe), manganese (Mn), and lead (Pb) levels of the groundwater samples were evaluated. Further, the samples were treated using solar thermal-based evaporative (STBE) arrangements. The HPI values of the raw samples demonstrated that the groundwater in the studied areas was affected by heavy metal contamination. The distillation of the groundwater samples exhibited that the STBE method is an effective and energy-efficient tool to eradicate the heavy metal contamination of the groundwater. Specifically, the average day-wise yield of the STBE arrangement was reported as 2838 ml/day in the lab-scale experiments.

Evaluation of the impact of wastewater irrigation on the soil's dielectric parameters

AbstractThis study investigates the impact of wastewater irrigation on soil dielectric parameters, focusing on the often‐overlooked aspect of dielectric properties in contaminated soil. Wastewater, a significant contributor to soil and groundwater degradation, has long‐term effects on soil physical, chemical, and dielectric characteristics. Experimental measurements conducted overtime at 2.45 and 5.8 GHz frequencies reveal a correlation between wastewater irrigation and changes in dielectric properties. Emphasizing time variation as a pivotal independent variable, the study sheds light on its substantial influence on soil dielectric behavior. Notably, the research introduces an alternative methodology for the comprehensive evaluation of wastewater‐induced pollution effects on soil properties. This approach is substantiated by meticulous physicochemical analyses conducted on both pollution sources and the affected soil. The study further presents a robust response surface method‐based model, showcasing impressive accuracy with dielectric properties (ε′ and ε″) and penetration depth with R2 values of 0.9845, 0.9831, and 0.9528, respectively. Beyond unveiling crucial insights into the intricate interplay of wastewater and soil dielectric behavior, this research contributes to the development of effective strategies for pollution monitoring and management in soil ecosystems.

IMPACT OF TECHNICAL LANDFILL BOUGUERGUER ON WATER RESOURCES AND THE ENVIRONMENT (NORTH-EAST ALGERIA)

While landfilling remains the most economically viable and commonly employed method of waste disposal, it poses potential risks of environmental degradation, including foul odor emission, biogas production, and the generation of leachates carrying a significant pollution load. Leachates, upon infiltrating the subsoil, contribute to a profound degradation of groundwater. This study focuses on assessing the impact of leachates from the public landfill of Bouguerguer (wilaya of Guelma) on groundwater and surface water. Two sampling campaigns were conducted, with the first involving 5 samples and the second comprising 8 samples, both carried out in 2018. Analytical results reveal that water sourced from wells, springs, and downstream surface water from the technical landfill Bouguerguer is heavily contaminated with organic matter and metallic trace elements (Cr+6, Pb+, Fe+3, and Ni). Levels of organic matter (BOD5: 50 mg/l - 10 mg/l, dissolved oxygen: 0.5-9 mg/l) are notably elevated in surface and groundwater, respectively. Additionally, concentrations of trace metal elements (Cr+6: 0.075-2.45 mg/l, Pb+: 0.03-1.16 mg/l, Fe+3: 0.006-7.07 mg/l, Ni+: 0.29-25 mg/l) significantly surpass the standards set by the World Health Organization (WHO). Consequently, these findings substantiate our hypothesis that degraded groundwater and surface water contribute significantly to the prevalence of diseases in Guelma Wilaya. This study emphasizes the urgent need for local authorities to implement preventive measures to mitigate pollution and to rehabilitate the landfill in accordance with international standards.

Chemical Characteristics and Genetic Analysis of Karst Groundwater in the Beijing Xishan Area

As an important water supply source in Beijing， karst groundwater has played an irreplaceable role in the security of urban water supply and ecological environment protection in the past 70 years. The Xishan karst groundwater system， located in the upper reaches of western Beijing， belongs to ecological conservation areas. There are several centralized water supply fields in this area. In this study， the Xishan karst groundwater system was taken as the research object. A total of 120 karst groundwater samples in this area were investigated by using statistical analysis， ion ratio， and principal component analysis （PCA） methods to explore the spatial distribution characteristics and formation mechanism of groundwater hydrochemistry. The research results showed that： ① the groundwater quality of the Xishan system was generally good， with the characteristics of neutral pH and low salinity. A total of 84.17% of the water samples were classified as hard water. The chemical type of groundwater was mainly HCO3-Ca·Mg. ② The chemical composition of groundwater was mainly affected by the water-rock interaction， and the weathering source of rock was mainly the dissolution of carbonate. ③ The results of principal component analysis showed that 34.41% of the chemistry formation of groundwater could be explained by carbonate dissolution， 27.33% by rock salt and evaporate dissolution， 11.76% by aquifer sediment dissolution， and 10.30% by domestic sewage discharge. From the recharge area to the runoff area and then to the discharge area， the TH and TDS gradually increased. Coal mining drainage and human activities were the main factors that caused groundwater degradation and variable hydrochemical types in the piedmont. In the future， it is necessary to further strengthen environmental governance， control point and non-point source pollution， and continuously monitor key areas to provide scientific support for ecological and environmental protection.

Addressing Nitrate Contamination in Groundwater: The Importance of Spatial and Temporal Understandings and Interpolation Methods

Iranian water security is threatened by groundwater (GW) degradation. The excessive use of GW for agriculture in Iran is degrading these resources. Livestock waste disposal and sewage irrigation are also major contributors. Nitrate (NO3) contamination in GW is a growing global concern, posing serious health and environmental risks. Soil can easily leach NO3 into GW, causing long-term contamination. Understanding the temporal and spatial patterns of NO3 pollution is vital in protecting human health and establishing safe drinking water limits. Choosing an appropriate interpolation method is crucial for creating a reliable spatial variability map, which is essential for environmental research and decision-making. This study used 85 GW samples collected over four periods to create interpolated maps and examine the spatial variability of NO3 levels. Spatial interpolation methods were performed using the geostatistical tool within ArcGIS Software. The results showed that Empirical Bayesian Kriging (EBK) was the most effective of the five evaluated interpolation methods, although the performance of each method varied depending on the period sampled. Therefore, the choice of interpolation method should be tailored to the study’s specific needs and the characteristics of the data being interpolated. The EBK method produced interpolation maps that illustrated the spatial distribution of NO3 concentrations, both within and exceeding the recommended guidelines. Interpolation methods can assist in creating spatial maps of NO3 concentrations, identifying pollution sources, and developing targeted management strategies. These maps demonstrate the potential impact of human activities on the observed patterns. A thorough understanding of Iran’s current GW quality is very important and valuable for management and policymakers.

Compounding effects of human activities and climatic changes on coexistence of oasis-desert ecosystems: Prioritizing resilient decision-making for a riskier world

Water-salt balance is critical for the stable coexistence of salt-affected and groundwater-fed oasis-desert ecosystems. Yet, a comprehensive investigation of how soil salinization and groundwater degradation threaten the coexistence of oasis-desert ecosystems is still scarce, especially under the compounding effects of human activities and climatic changes. Here, we assessed the impacts of irrigated agriculture on hydrological regimes in oasis-desert systems, investigated the spatio-temporal variations of soil salinization in irrigated cropland, and evaluated the implications of the interplays of soil salinization and groundwater degradation on the coexistence of oasis-desert ecosystems in northwestern China, based on meaningful modelling approaches and comprehensive measurements over 1995–2020. The results showed that the irrigation return flow coefficient decreased sharply from 0.21 ± 0.09 in the traditional irrigation period to 0.09 ± 0.01 in the water-saving irrigation period. The continuous drop in groundwater tables and significant degradation of groundwater quality are occurring throughout this watershed. The eco-environmental flows are reaching to their limit with watershed closures (i.e., the drainage from the oasis region into the desert region is being weakened or even eliminated), although these progressions were largely hidden by regional precipitation and streamflow variability. The process of salt migration and accumulation across different landscapes in oasis-desert system is being reshaped, and soil salinization in water-saving agricultural irrigated lands is accelerating with a regional average annual growth rate of 18%. The vegetation in this watershed is degrading, and anthropogenic disturbance accelerates this trend. Our results highlight that environmental stress adaptation strategies must account for resilience maintenance to avoid accelerating catastrophic transitions in oasis-desert ecosystems. Determining the optimal oasis scales and formulating the best irrigation management plans are effective and resilient decision-making ways to maintain the coexistence relationship of oasis-desert ecosystem in drylands.

Performance analysis of decentralized sewage solutions for multifamily residential condominiums in Aracaju

The adoption of decentralized sewage treatment systems appears as an alternative for regions lacking sanitary infrastructure. Regarding Brazilian municipalities, they presented, in 2020, a sewage collection service rate for the urban population equal to 63.2%. Also, according to data from the National Sanitation Information System, in the municipality of Aracaju, capital of the state of Sergipe, the rate of collection of generated sewage is only 53.5%. Due this reality, investment in individual effluent treatment systems becomes a valuable alternative for areas that lack of sanitary infrastructure. In this work, the performance of domestic sewage treatment systems, used as individual treatment solutions in two multifamily condominiums in the capital of Sergipe, was evaluated. Physical-chemical monitoring of the individual sewage treatment systems was carried out, and the results indicated negative efficiencies in most of the analyzed parameters. As for the requirements of the current environmental legislation for the release of effluents, there was non-compliance with the legislation in almost all the time of observation. The lack of systems operation supervision by public agencies leads to failures that cause degradation of groundwater and surface water. Moreover, there is a lack of commitment to inspections and maintenance of the systems by those responsible for the condominiums. According to the types of solutions adopted, treated sewage with higher quality should be achieved and, thus, effluents with high loads of pollutants would not be released into water bodies.

Impact of various anthropogenic disturbances on water availability in the entire Mongolian basins towards effective utilization of water resources

In Mongolia, overuse and degradation of groundwater is a serious issue. The authors have recently applied a process-based eco-hydrology model, NICE (National Integrated Catchment-based Eco-hydrology) to urban and mining hubs to explicitly quantify spatio-temporal variations in water availability. In this study, NICE was scaled up to the total of 29 river basins in the entire country. The model simulated the effect of past climatic change and human activity on water resources during 1980-2018 there. The model reasonably reproduced observed river discharge with a maximal value during summer rainfall seasons. The simulation also revealed heterogeneous distributions of hydrologic budget and its response to climatic and anthropogenic disturbances. In addition, the authors detected hot spots of groundwater degradation by anthropogenic activity in the national scale. Analysis of relative contribution of environmental factors further clarified the characteristics in these areas and quantified spatio-temporal trends in groundwater level due to the effects of changes in precipitation and various water uses. Generally, the result showed changes in precipitation had a large effect on changes in groundwater levels until 2000. In contrast, the model clarified human activities have recently had a large impact on groundwater level changes. This trend was particularly conspicuous in river basins with urbanization and mining development such as Orkhon, Kharaa, Tuul, Galba, Ongi, Altain Uvur Govi, and Taats River Basins. This methodology is powerful to resolve future competition for water resources in areas with fewer inventory data that could potentially trigger conflicts between urban, mining, industry, herders and local communities.

Effects of Seawater Intrusion on the Groundwater Quality of Multi-Layered Aquifers in Eastern Saudi Arabia

The degradation of groundwater (GW) quality due to seawater intrusion (SWI) is a major water security issue in water-scarce regions. This study aims to delineate the impact of SWI on the GW quality of a multilayered aquifer system in the eastern coastal region of Saudi Arabia. The physical and chemical properties of the GW were determined via field investigations and laboratory analyses. Irrigation indices (electrical conductivity (EC), potential salinity (PS), sodium adsorption ratio (SAR), Na%, Kelly's ratio (KR), magnesium adsorption ratio (MAR), and permeability index (PI)) and a SWI index (fsea) were obtained to assess the suitability of GW for irrigation. K-mean clustering, correlation analysis, and principal component analysis (PCA) were used to determine the relationship between irrigation hazard indices and the degree of SWI. The tested GW samples were grouped into four clusters (C1, C2, C3, and C4), with average SWI degrees of 15%, 8%, 5%, and 2%, respectively. The results showed that the tested GW was unsuitable for irrigation due to salinity hazards. However, a noticeable increase in sodium and magnesium hazards was also observed. Moreover, increasing the degree of SWI (fsea) was associated with increasing salinity, sodium, and magnesium, with higher values observed in the GW samples in cluster C1, followed by clusters C2, C3, and C4. The correlation analysis and PCA results illustrated that the irrigation indices, including EC, PS, SAR, and MAR, were grouped with the SWI index (fsea), indicating the possibility of using them as primary irrigation indices to reflect the impact of SWI on GW quality in coastal regions. The results of this study will help guide decision-makers toward proper management practices for SWI mitigation and enhancing GW quality for irrigation.

Degradation of sulfolane-contaminated groundwater in a tubular microbial fuel cell-based electro-Fenton system: Performance, external resistance effects and microbial community

A tubular bio-electro Fenton (BEF) system is designed in a field-scale groundwater application. An Fe-graphite felt (Fe@GF) cathode with optimal iron loading was used to prevent the generation of iron sludge. The Fe@GF cathode generates H2O2 through the 2-electron oxygen reduction reaction, facilitating the removal of sulfolane. For Fe@GF with an iron loading of 0.3 g/L, the reduction peak current reached −1.20 mA, which was 9.3 times that for GF. To optimize the performance of the BEF system, various external resistances were studied, and 10 Ω was found to yield the highest current density of 1034 mA/m2 and the highest H2O2 concentration of 8.9 mg/L. The presence of OH∙ was confirmed following the Fenton reaction, with 100 % removal of 50 mg/L of sulfolane. Microbial community analysis at an external resistance of 10 Ω revealed that electrochemically active bacteria (Clostridiaceae and Dysgonomonadaceae) were the dominant species. Low external resistance was found to favor in activation of the BEF process.

Assessing the Impact of Land Cover on Groundwater Quality in a Smart City Using GIS and Machine Learning Algorithms

The present study aimed to assess the impacts of land cover on groundwater quality by integrating physico-chemical data and satellite imageries. Initially, fourteen groundwater parameters of both pre-monsoon and post-monsoon were collected from nineteen sampled stations and water quality index (WQI) was calculated. Consequently, Google earth, Landsat-8, and Sentinel-2A imageries were considered for land cover mapping including the concentration of settlement and urban built-up, greenery coverage, and micro-level land use. Two machine learning models such as artificial neural network (ANN) and random forest (RF) were used for pixel-based classification and establish spatial relation between water quality and land cover. This study trained and tested the models for the whole study area as well as 500m buffers from each sampled station. The result of model’s validation including mean absolute error (MAE), root mean squared error (RMSE), Kappa statistic (K), overall accuracy of model (OAC), and receiver operating characteristic (ROC), indicated that random forest classifier has better performance than the artificial neural network. The results show that the testing dataset of pre-monsoon season has higher accuracy with MAE 0.343, RMSE 0.397, K value 0.55, and ROC value 0.838 to envisage the impact of land cover on groundwater quality in comparison to post-monsoon season. The results also reveal that the classification accuracy is greater within 500m buffer areas in comparison to the whole study area with a close to 0 values of MAE and RMSE, and absolutely 1 value of K and ROC. Based on the above findings, the present study suggested considering a large scale for determining the controlling factors of groundwater degradation.

Water stress and the expenditure in zoning violated areas of Chennai: An empirical investigation

India as the largest user of groundwater in the world faces the risk of resources depletion and degradation. The study focuses on groundwater degradation and drinking water expenditure in 45 locations of 15 Zoning Violated Areas (ZVAs) in Chennai. We collected 45 groundwater samples in each pre- and post-monsoon seasons for testing heavy metals concentration levels and compared them with the World Health Organization (WHO)/the Bureau of Indian Standards (BIS) drinking water standards. We surveyed 797 households in the 14 ZVAs and statistically analysed drinking water expenditure. Scientific analysis reveals that Cadmium and Nickel are 15 and 7 times higher than the WHO/BIS standards in Nagalkeni of Pammal area. The analysis also shows that higher levels of concentrations of Lead, Nickel, Chromium and Cadmium in the groundwater in 25, 13, 3 and 1 locations respectively. Survey analysis indicates that 3,21,102 households have incurred an aggregate expenditure of $52.72 million per year on drinking water. The analysis shows that each of the economically weaker, lower-middle and upper middle-income groups spend, on average, 11.64, 4.72 and 2.55 per cent of their daily income, respectively on drinking water. The study also informs that Pammal is the most vulnerable area in groundwater contamination and households in Ambattur area has incurred highest expenditure on drinking water. The regression analysis of the data reveals that variables, such as metro water, income and family size are statistically significant in explaining the water expenditure. The Computable General Equilibrium model for Chennai estimates shows that the increase in water resources and economic growth under the assumption that all the households will, and economically weaker sections will not, contribute to investments for drinking water resources. The study proposes a household-right-to-know legislation, adequate metro water supply and an incentive-structured compatible land-use regulation to achieve sustainable use of groundwater resources.

Farming with forages can reconnect crop and livestock operations to enhance circularity and foster ecosystem services

AbstractAgriculture has undergone dramatic technological and cultural changes over the past century. Many would argue that the changes have been unquestionably positive with huge gains in productivity, reduced labour requirements, and alleviation of food insecurity for most people. However, the adoption of increasingly specialized and separated crop and livestock enterprises has also had widespread negative consequences resulting in (a) decline in biodiversity, (b) degradation of groundwater and surface waters with agrochemical pollutants, (c) poor soil health with monoculture crop production and frequent soil disturbance, (d) intensive greenhouse gas emissions from both specialized cropping systems relying on external inputs and concentrated animal feeding operations that accumulate wastes, and (e) general lack of ecological integrity among components of these specialized systems. Diversified agricultural systems using annual and perennial forages offer opportunities to elevate ecological synergies when crop and livestock operations are integrated. Integrated crop‐livestock systems can internalize nutrient cycling, provide cultural control of weeds, insects and diseases, and share resources in a circular‐based agroecosystem. Cover crops could be transitioned into nutritious annual forages for livestock grazing on currently specialized crop production farms with appropriate local incentives. Perennial forages in ley farming or in pasture‐crop rotations have historical relevance and are a proven practice for conserving nutrients, improving soil health and enhancing biodiversity. Redesigning contemporary agriculture with mixed‐use farming techniques could greatly reduce soil erosion, improve water quality, and invigorate soil health. We suggest that incorporating different types of forages across a diverse landscape can enhance agricultural sustainability and ecological integrity.

Health risks of shallow groundwater in the five basins of Shanxi, China: Geographical, geological and human activity roles

Rapid economic development often leads to groundwater degradation, posing health risks to those who rely on it. The groundwater discharge conditions in basins are poor. The health risk of shallow groundwater in basins needs more attentions. The health risk of shallow groundwater in the five basins of Shanxi Province, China was discussed based on the hydrochemical evolution of shallow groundwater and the water quality assessment. The results showed that arsenic (As) and chromium (Cr) in the shallow groundwater of the basins caused prominent health risks followed by fluoride (F) and nitrate (NO3−). The non-carcinogenic risks of As, F and NO3- to children were higher than that to adults, and the carcinogenic risks of As and Cr were higher for adults than children. Various hydrogeochemical reactions, geological conditions, climatic factors, and human activities are closely related to groundwater health risks, and basin topography is considered as one of key factors. Water-rock interaction, dedolomitization and cation exchange are the natural processes in the evolution of groundwater hydrochemistry, while agricultural and mining activities are the anthropogenic factors causing groundwater degradation. The leaching/dilution effects of infiltration precipitation in the basin-mountain systems cause distinct temporal changes in the chemical composition and health risks of the groundwater in the basins. Differences in climate and farming practices among the basins further complicate the spatio-temporal changes. The basin-mountain system is conducive to the convergence and enrichment of water flow and solutes in the basins, which aggravates the degradation of groundwater quality. This study highlights that the combined influences of geographical and geological factors and anthropogenic activities amplify the human health risks of groundwater in the basins.

Enhanced sulfolane-contaminated groundwater degradation and power generation by a mini tubular microbial fuel cell/electro-Fenton combined system

A tubular microbial fuel cell/electro-Fenton (MFC/EF) combined system was developed for field-scale applications. This tubular MFC/EF combined system treats groundwater containing sulfolane by driving the Fenton reaction at the cathode using bioelectricity that is generated at the anode. Proper aeration and an adequate supply of carbon were found to improve significantly the performance of a tubular MFC/EF combined system. The tubular MFC/EF combined system exhibited high voltage output (525 mV) and high power density (691 mW/m3). The generation of H2O2 from the cathode at 1 L/min aeration was 20 times that at 0.1 L/min, and achieved 100% removal efficiency of sulfolane (50 mg/L). The bicinchoninic acid assay detected an increase in the amount of bacteria by a factor of 2.2 as a result of electrical stimulation following tubular MFC/EF operation. The biotoxicity of sulfolane after tubular MFC/EF treatment revealed that the light inhibition of Vibrio fischeri was only 4% at 1 L/min aeration, owing to the by-product (SO42-). The results demonstrated that the tubular MFC/EF combined system was effective in removing sulfolane and reducing the toxicity of by-products in the purification of water.

The Importance of Prevention in Tackling Desertification: An Approach to Anticipate Risks of Degradation in Coastal Aquifers

Groundwater degradation is a major issue on an increasingly hot and thirsty planet. The problem is critical in drylands, where recharge rates are low and groundwater is the only reliable resource in a context of water scarcity and stress. Aquifer depletion and contamination is a process of desertification. Land Degradation Neutrality is regarded as the main initiative to tackle land degradation and desertification. It is embedded in target 15.3 of the Sustainable Development Goals and focused on preventing these dynamics. Within this framework, we present an approach to assess risks of degradation and desertification in coastal basins with aquifers threatened by seawater intrusion. The approach utilizes an integrated system dynamics model representing the main relationships between the aquifer and an intensively irrigated area (greenhouses) driven by short- and medium-term profitability. The study area is located in a semi-arid region in Southern Spain, the Gualchos stream basin, which contains the Castell de Ferro aquifer. We found that the risk of salinization of the aquifer is 73%, while there is a 70% risk that the system would increases its demand for surface water in the future, and the chance of doubling the current demand is almost 50%. If the current system of reservoirs in the area were not able to satisfy such an increase in demand because of climate change, the basin would be at a serious risk of desertification.

Radiocarbon Dating and Stable Isotopes Content in the Assessment of Groundwater Recharge at Santiago Island, Republic of Cape Verde

The over-exploitation of coastal aquifers has led to seawater intrusion issues in many parts of the globe; this problem, which is associated with water recharge deficit and anthropogenic pollution, represents the main source of groundwater degradation in Santiago Island in the Republic of Cape Verde’s archipelago. Brackish groundwater for agriculture and human consumption is being provided to several areas on Santiago Island as the only type of available water. Chemical and isotopic data obtained in three main groundwater systems were used in the characterization of the groundwater resources and in the identification of the main source responsible for their degradation. The obtained results indicate water–rock interaction as the major process responsible for the groundwater quality reflecting its lithological composition. Carbonatite dissolution can be partially responsible for the calcium increase along the groundwater flow path. Isotopic data (δ2H, δ18O; 3H and 14C) combined with the water chemistry provided a wide characterization of the groundwater recharge and identification of salinization processes (like seawater intrusion and marine aerosols dissolution in different sectors of the island). In the eastern part of Santiago Island, a different isotopic pattern (2H-18O) was observed in the groundwater samples, which was likely ascribed to different climate conditions. Carbon-14 determinations indicate apparent groundwater ages between 3.5 and 5.1 ka BP.