Natural and anthropogenic factors driving groundwater resources salinization for agriculture use in the Campania plains (Southern Italy)

Integrated approach to understand the multiple natural and anthropogenic stresses on intensively irrigated coastal aquifer in the Mediterranean region

Understanding the major factors influencing groundwater chemistry and its evolution in irrigation areas is crucial for efficient irrigation management. Major ions and isotopes (δD-H2O together with δ18O-H2O) were used to identify the natural and anthropogenic factors contributing to groundwater salinization in the shallow aquifer of the Wadi Guenniche Plain (WGP) in the Mediterranean region of Tunisia. A comprehensive geochemical investigation of groundwater was conducted during both the low irrigation season (L-IR) and the high irrigation season (H-IR). The results show that the variation range and average concentrations of almost all the ions in both the L-IR and H-IR seasons are high. The groundwater in both seasons is characterized by high electrical conductivity and CaMgCl/SO4 and NaCl types. The dissolution of halite and gypsum, the precipitation of calcite and dolomite, and Na-Ca exchange are the main chemical reactions in the geochemical evolution of groundwater in the Wadi Guenniche Shallow Aquifer (WGSA). Stable isotopes of hydrogen and oxygen (δ18O-H2O and δD-H2O) indicate that groundwater in WGSA originated from local precipitation. In the H-IR season, the δ18O-H2O and δD-H2O values indicate that the groundwater experienced noticeable evaporation. The enriched isotopic signatures reveal that the WGSA's groundwater was influenced by irrigation return flow and seawater intrusion. The proportions of mixing with seawater were found to vary between 0.12% and 5.95%, and between 0.13% and 8.42% during the L-IR and H-IR seasons, respectively. Irrigation return flow and the associated evaporation increase the dissolved solids content in groundwater during the irrigation season. The long-term human activities (fertilization, irrigation, and septic waste infiltration) are the main drives of the high nitrate-N concentrations in groundwater. In coastal irrigation areas suffering from water scarcity, these results can help planners and policy makers understand the complexities of groundwater salinization to enable more sustainable management and development.

Geochemical processes, salinity sources and utility characterization of groundwater in a semi-arid region of Iraq through geostatistical and isotopic techniques

Identifying factors contributing to water salinity is paramount in efficiently managing limited water resources in arid environments. The primary objective of this study is to enhance understanding regarding the hydrochemistry, source, and mechanism of water salinity, as well as to assess the suitability of water for various uses in southern Iraq. The groundwater samples were collected from water wells and springs and analyzed for major cations and anions along with stable isotopes (δ18O and δ2H) to accomplish the objective. The analysis of major ion chemistry, hydrochemical techniques, principal component analysis (PCA), and isotope signatures were adopted to determine the primary factors contributing to water mineralization. The study inferred that evaporation and geological processes encompassing water-rock interactions, such as dissolution precipitation and ion exchange, were key processes. The stable isotope analysis revealed that the water originated from meteoric sources and underwent significant evaporation during or before infiltration. The utility assessment of water samples indicates that most samples are not appropriate for consumption and are significantly below the established standards for potable water. In contrast, a significant portion of the groundwater samples were found to meet the criteria for irrigation suitability by adopting Wilcox and the US Salinity Laboratory criteria. The groundwater could be considered for irrigation with proper salinity control management. Overall, this study has significantly improved the understanding of the hydrogeochemical regimes and acts as a first step toward the sustainable utilization of water resources.

Salinization of shallow groundwater in the Jiaokou Irrigation District and associated secondary environmental challenges

Understanding groundwater salinization of irrigation areas and related secondary environmental challenges is important for ensuring sustainable development. However, the mechanism under which groundwater salinization forms under the influence of long-term anthropogenic activities remains unclear. Therefore, this study analyzed the spatiotemporal variation in groundwater salinization and the underlying mechanism, and discussed the secondary environmental challenges in an irrigation area. The Jiaokou Irrigation District, North China, was adopted as a case study. The results showed a slight downward trend in groundwater salinity over the past two decades at a rate of 0.0229 g/L/y. Higher groundwater salinity was observed in areas with shallow groundwater depth. This correlation was mainly attributed to evaporative concentration, with secondary processes including natural weathering, depth of water-table, and fertilizer leaching. Drainage ditches may reduce groundwater salinity. Groundwater was transformed from freshwater to salt water and then to brackish water during the runoff process. The former transformation is mainly related to evaporation and fertilization. The latter transformation could be related to the inverse relationship between the distance to the Wei River and sediment permeability, with sediment permeability positively related to groundwater flow and leading to the discharge of salt into the Wei River. The secondary environmental challenges related to groundwater salinization in irrigation areas, mainly manifested in deterioration of irrigation water quality, soil salinization, and increased fluorine concentration. This study can act as a theoretical and practical reference for the development and utilization of water resources, ecological protection, and soil salinization in typical irrigation districts.

Long-term trends of salinity in coastal wetlands: Effects of climate, extreme weather events, and sea water level

Coastal freshwater ecosystems play major roles as reservoirs of biodiversity and provide many ecosystem services and protection from extreme weather events. While they are of particular importance worldwide, they are affected by a large variety of anthropogenic threats, among which salinization has been less studied, particularly regarding large temporal and spatial data sets based on real case scenarios, while salinity can impact biodiversity and ecosystem functioning. In this study, we investigated the variations of salinity across long-term (1996-2020) and seasonal (monthly records) temporal scales and spatial (varying distance to the coastline) scales in water bodies of two typical temperate coastal wetlands situated on the Atlantic coast of France. We complemented our analyses with models of sea water levels computed at both sites across 2000-2020. Our detailed data set allowed for highlighting that salinity in ponds varied seasonally (higher during summer, due to decreased precipitation and higher temperature), but also spatially (higher closer to the seashore, which pattern increased through time). Over the long term, decreased precipitation but not increased temperature induced increasing salinity. We also highlighted contrasted long-term patterns of salinity changes on these two coastal wetlands, with one site were salinity decreased over time linked to the responses to marine flood, allowing to document the temporal dynamics of salinity following a massive intrusion of sea water. Complementarily, at both sites, water levels at high tides increased through time, a pattern which can induce additional salinization. To our knowledge, our study is the first to investigate long-term changes in salinity in coastal wetlands through natural processes (e.g. seaspray, seasonal variations) and ongoing climate perturbations (e.g. marine surges linked to extreme weather events, increased temperature and decreased precipitations).

Modeling stochastic saline groundwater occurrence in coastal aquifers

The issue of freshwater salinization in coastal areas has grown in importance with the increase of the demand of groundwater supply and the more frequent droughts. However, the spatial patterns of salinity contamination are not easy to be understood, as well as their numerical modeling is subject to various kinds of uncertainty. This paper offers a robust, flexible, and reliable geostatistical methodology to provide a stochastic assessment of salinity distribution in alluvial coastal areas. The methodology is applied to a coastal aquifer in Campania (Italy), where 83 monitoring wells provided depth-averaged salinity data. A Monte Carlo (MC) framework was implemented to simulate depth-averaged groundwater salinity fields. Both MC stochastic fields and the mean across MC simulations enabled to the delineation of which areas are subject to high salinity. Then, a probabilistic approach was developed setting up salinity thresholds for agricultural use to delineate the areas with unsuitable groundwater for irrigation purposes. Furthermore, steady spatial patterns of saline wedge lengths were unveiled through uncertainty estimates of seawater ingression at the Volturno River mouth. The results were compared versus a calibrated numerical model with remarkable model fit (R²=0.96) and versus an analytical solution, obtaining similar wedge lengths. The results pointed out that the high groundwater salinities found inland (more than 2 km from the coastline) could be ascribed to trapped paleo-seawater rather than to actual seawater intrusion. In fact, the inland high salinities were in correspondence of thick peaty layers, which can store trapped saline waters because of their high porosity and low permeability. Furthermore, these results are consistent with the recognition of depositional environments and the position of ancient lagoon alluvial sediments, located in the same areas where are the highest (simulated) salinity fields. This robust probabilistic approach could be applied to similar alluvial coastal areas to understand spatial patterns of present salinization, to disentangle actual from paleo-seawater intrusion, and more in general to delineate zones with unsuitable salinity for irrigation purposes.

Estimation of Polycyclic Aromatic Hydrocarbons in Groundwater from Campania Plain: Spatial Distribution, Source Attribution and Health Cancer Risk Evaluation

The aim of this study was to evaluate the concentrations of polycyclic aromatic hydrocarbons (PAHs) in 1168 groundwater samples of the Campania Plain (Southern Italy), taken using a municipal environmental pressure index (MIEP), and to analyze the distribution of these compounds to determine source PAHs using ratios of isomers diagnostic. Lastly, this study also aimed to estimate the potential health cancer risk in groundwaters. The data indicated that the highest concentration of PAHs was found in groundwater from Caserta Province and the contents of BghiP, Phe, and Nap were detected in the samples. The spatial distribution of these pollutants was evaluated using the Jenks method; moreover, the data indicated that incremental lifetime cancer risk ILCR_ingestion ranged from 7.31 × 10^-20 to 4.96 × 10^-19, while ILCR_dermal ranged from 4.32 × 10^-11 to 2.93 × 10^-10. These research findings may provide information about the Campania Plain's groundwater quality and aid in the development of preventative measures to lessen PAH contamination in groundwater.

Hydrogeochemical characteristics and health risk assessment of potentially toxic elements in groundwater and their relationship with the ecosystem: case study in Tunisia

Sidi Bouzid basin knows for several decades a fast-growing anthropogenic activity and, consequently, an increase in groundwater pollution which attracted researcher attention. For this task, we performed an exhaustive study to evaluate groundwater geochemical evolution. Our research begins with analyzing the geochemical process, then determining the water quality indices and their impact on the ecosystem, and after that correlating between different compartments, and ends with the assessment of the human health risk toward NO₃^-, Fe, Mn, Zn, Cd, and Pb. The dominant facies of the groundwater in the study area are Ca-Mg-SO₄ and Ca-Mg-HCO₃ and are mainly influenced by evaporite deposits (CaSO₄, CaSO₄·2H₂O, and NaCl). The pollution index of groundwater (PIG) displays values ranging between 0.5 and 4.5 indicating four classes of pollution (insignificant, low, moderate, and high). More than half of the samples (55%) belong to the low and moderate PIG classes. However, the results show elevated values of NO₃^- concentration; 76% of samples exceed 30 mg/L. Among the studied contaminants, the highest carcinogenic and non-carcinogenic risks in study areas were related to NO₃^-. For all water samples, the risk levels for children were greater than those for adults. Lastly, the partial least square-structural equation modelling (PLS-SEM) shows that the chemical elements do not have a short-term potential impact of pollutants on ecosystems.

Hydrogeochemical and isotopic characterization of the Gioia Tauro coastal Plain (Calabria - southern Italy): A multidisciplinary approach for a focused management of vulnerable strategic systems

This work pursues the hydro-geochemical and isotopic characterization of the complex groundwater system of the Gioia Tauro Plain, one of the most important industrialized and agricultural coastal areas of southern Italy. The anthropic pressure exposes the water resources at risk of depletion and quality degradation making the plain groundwater a system of high scientific and social interest. The plain is characterized by a shallow aquifer, mostly recharged by local rains and a deep aquifer apparently less influenced by local precipitation. Both aquifers are mainly Ca-HCO₃ waters except for localized sectors where Na-HCO₃, Na-Cl and Ca-SO₄ waters are present. In deep aquifer, both prolonged interaction with sedimentary rocks, mainly deriving from the erosion of crystalline rocks, and direct cation exchange represent the primary factors controlling the formation of Na-HCO₃ waters. Mixing processes between these waters and either connate brine and/or deep thermal waters contribute to the formation of isolated high salinity Na-Cl-rich waters. In shallow aquifer, inputs of N-rich sewage and agriculture-related contaminants, and SOx emissions in proximity of the harbor are responsible of the increasing nitrate and sulphate concentrations, respectively. The Cl/Br and NO₃/Cl ratios highlight contamination mainly linked to agricultural activities and contribution of wastewater. Along the northern boundary, the warmest groundwater (Na-Cl[SO₄]) were found close to a bend of the main strike-slip fault system, locally favouring the rising of B- and Li-rich deep waters, testifying the influence of geological-structural features on deep water circulation. Despite the high-water demand, a direct marine intrusion is localized in a very restricted area, where we observed an incipient groundwater-seawater mixing (seawater contribution ≤7 %). The qualitative and quantitative conditions of the shallow aquifer still have acceptable levels because of the relatively high recharge inflow. A reliable hydrogeochemical conceptual model, able to explain the compositional variability of the studied waters, is proposed.

Zearalenone (ZEN) and Its Metabolite Levels in Tissues of Wild Boar (Sus scrofa) from Southern Italy: A Pilot Study

Zearalenone (ZEN) is a non-steroidal estrogenic mycotoxin produced by the fungi of the Fusarium genera, and is a contaminant of cereals and plant products. ZEN and its metabolites are considered endocrine disruptors, and could have various toxic effects on animals and humans. In recent years, there has been a significant demographic increase in wild boar (Sus scrofa) in many mountainous and hilly areas of Italy, including the Campania region, mainly due to global climate change. The wild boar can be defined as a generalist and omnivorous species capable of varying its diet; therefore, it can play a role as an environmental bioindicator towards contaminants such as mycotoxins. This study was conducted to evaluate, for the first time, the concentrations of ZEN and its metabolites in the liver, kidney, and muscle of 82 wild boars shot in their habitat by hunters with hunting permits in different localities of Avellino province (Campania region, Southern Italy) from 2021 to 2022. The samples were collected and analyzed with an SPE clean-up and high-pressure liquid chromatography method with fluorescence detection. The results indicated that ZEN and α-Zearalenol were present in most of the samples, suggesting that a plan to monitor these mycoestrogens is essential to achieve the goals of "One Health".

Hydrochemical evaluation of groundwater quality and human health risk assessment of trace elements in the largest mining district of South Khorasan, Eastern Iran

The groundwater resources of mining areas have been in a challenging condition in terms of metal pollution and human health. Therefore, this study investigated the concentration of cobalt (Co), molybdenum (Mo), selenium (Se), tin (Sn), and antimony (Sb) in groundwater samples (wells, qanats, and springs) in a heavily contaminated mining district, South Khorasan, Eastern Iran. Human health risk of the studied metals to target groups was assessed, and water quality of the studied groundwater was investigated in the study area. A total of 367 sampling sites (279 wells, 74 qanats, and 14 springs) in South Khorasan Province were selected to collect the groundwater samples from June to July 2020. Sampling was performed thrice for each sampling point, and hydrochemical parameters were evaluated using a portable multiparameter. Inductively coupled plasma mass spectrometry (ICP-MS) was used to detect the metal concentrations. Results showed an order of Se > Mo > Sn > Co > Sb, and hazard index (HI) demonstrated a warning condition for south of South Khorasan (drinking application), southwest of South Khorasan (Irrigation application), and east and center of South Khorasan (drinking-irrigation application). Hydrochemical parameters showed a classification of "Na + K type" and "Mixed Ca-Mg-Cl type" with an overall group of "Na-Cl-HCO3" for sampled waters. Ficklin-Caboi diagram depicted a classification of "near-neutral low metal," and Schoeller diagram classified studied groundwater as "good" for drinking and irrigation consumptions and "Na-Cl" type based on ion balance diagram. Based on the correlation analysis, positive relationships were recorded among EC, TDS, Cl-, Na+, sulfate, Ca2+, salt, total hardness, Mg2+, ammonia, and K+ measured in the water samples. In essence, arid regions of the world greatly rely upon groundwater resources for drinking and irrigation consumptions, and mining districts with a heavy load of active mines can be a serious threat to the groundwater quality and human health.

Groundwater in Southern Vietnam: Understanding geochemical processes to better preserve the critical water resource

A thorough understanding of groundwater geochemical characteristics and dominant hydro(bio)geochemical processes in the aquifers is valuable for sustainable groundwater protection. With this respect, this study provides a comprehensive assessment of hydrogeochemical characteristics of groundwater in sedimentary aquifers of the Southern region of Vietnam. The dataset comprised 291 water samples collected in rainy and dry seasons from 155 wells, and their chemical compositions of dissolved ions (Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃^-, Cl^-, SO₄^2-, NO₃^-, NH₄⁺, Fe, total dissolved solids) and pH. We calculated the groundwater quality index to determine the suitability of groundwater for drinking purposes. Accordingly, about 47% of groundwater samples range from poor to unsuitable quality for drinking purposes, in which total dissolved solid (TDS) and high iron concentrations are primary factors. We also examined hydrogeochemical characteristics by multivariate statistical analyses (Hierarchical Cluster Analysis and Principal Component Analysis). The results demonstrated four groups of water: fresh groundwater (TDS < 1 g/L) in the highland (Group 1), lowland fresh-to-saline groundwater (2a), lowland saline groundwater (2b), and lowland saline/acidic groundwater (2c). Although the highland area is currently not impacted by salinization, the contamination by nitrate and chloride associated with a dense urban population and agricultural practices is deteriorating its fresh groundwater resources. On the other hand, the lowland area of Southern Vietnam is highly vulnerable to seawater intrusion (groups 2b and 2c). Only 34% out of 191 samples collected in the lowland area of southern Vietnam remained fresh. In this light, this study depicted the specific geographical location for various groundwater groups in Southern Vietnam. This finding is significant to assist water scientists and decision-makers in implementing targetted groundwater management measures as prevention and protection strategies should be tailored to groundwater geochemical characteristics and the dominant hydro(bio)geochemical processes.

Actual and Forecasted Vulnerability Assessment to Seawater Intrusion via GALDIT-SUSI in the Volturno River Mouth (Italy)

Coastal areas have become increasingly vulnerable to groundwater salinization, especially in the last century, due to the combined effects of climate change and growing anthropization. In this study, a novel methodology named GALDIT-SUSI was applied in the floodplain of the Volturno River mouth for the current (2018) and future (2050) evaluation of seawater intrusion accounting for the expected subsidence and groundwater salinization rates. Several input variables such as digital surface model, land use classification, subsidence rate and drainage system have been mapped via remote sensing resources. The current assessment highlights how areas affected by salinization coincide with the semiperennial lagoons and inland depressed areas where paleosaline groundwaters are present. The future assessment (2050) shows a marked increase of salinization vulnerability in the coastal strip and in the most depressed areas. The results highlight that the main vulnerability driver is the Revelle index, while predicted subsidence and recharge rates will only slightly affect groundwater salinization. This case study indicates that GALDIT-SUSI is a reliable and easy-to-use tool for the assessment of groundwater salinization in many coastal regions of the world.

Hydrochemistry, quality and potential health risk appraisal of nitrate enriched groundwater in the Nanchong area, southwestern China

Assessments for groundwater quality and potential health risk are significant for better utilization and exploitation. In the present study, seventy groundwater samples were collected from domestic tube wells and public water-supply wells in the Nanchong area, southwestern China. The integration of statistical analysis, ion correlation, geomodelling analysis, entropy water quality index and health risks assessment were compiled in this study. Statistical analysis indicated the cations followed the concentration order as Ca²⁺ > Na⁺ > Mg²⁺ > K⁺, while anions' concentrations were HCO₃^- > SO₄^2- > Cl^- > NO₃^- > F^- based on Box and Whisker plot. Piper triangle diagram proposed the hydrochemical type was characterized as Ca-HCO₃. Correlations of ions and geomodelling revealed the concentrations of major ions were mainly determined by calcite dissolution and ion exchange process and NO₃^- concentrations were controlled by agriculture activities. Entropy water quality index computation demonstrated that 96% of groundwater samples possessed the EWQI values of 29-95, and thus were suitable for drinking purpose. The HI_Total values for 66% groundwater samples exceeded the acceptable limit for non-carcinogenic risk (HI =1) for infants, followed by 41% for children, 37% for adult males, and 30% for adult females. The non-carcinogenic human health risk of different population groups followed the order of infants > children > adult males > adult females. In future, targeted measures for human health risks of NO₃^- will focus on the improvements for agricultural activities, including reducing the use of nitrogenous fertilizer, changing irrigation pattern, etc. Our study provides the vital knowledge for groundwater management in the Nanchong and development of the Cheng -Yu Economic Circle.