Anthropogenic activities and salinization are increasingly threatening groundwater resources, especially in arid and semi-arid regions. Unlike previous studies focusing on isotopes or hydrochemistry separately, this study investigates the first application of stable isotopes (water (δ18OH₂O and δ2HH₂O), dissolved nitrate (δ15NNO₃ and δ18ONO₃) and sulfate (δ34SSO₄ and δ18OSO₄)), hydrochemical and statistical integrated approach to identify salinity and pollution sources in the Zeuss-Koutine (ZK) and Mio-Plio-Quaternary (MPQ) aquifers, Southeast of Tunisia. These techniques were combined to determine the water quality, recharge origin, salinity sources and potential sources of contamination, using 46 water samples collected from 40 exploitation wells and 6 wadis. The findings reveal that groundwater salinity and pollution is mainly controlled by evaporite dissolution and anthropogenic activities. Therefore, the electrical conductivity ranging from 1875 to 7090 µS/cm at 25°C. All samples are above the WHO-recommended tolerable limits for sulfate, chloride, sodium, and fluoride. The hazard quotients (HQ) for non-carcinogenic health risk assessment indicate that children are the most vulnerable to fluoride exposure. Nitrate concentrations ranged from 1 mg/L to 120.4 mg/L and 35 Groundwater salinity is controlled by evaporite dissolution and seawater mixing. δ18OH₂O and δ2HH₂O confirm meteoric origin of ZK and MPQ groundwater. 35

Water scarcity is a significant issue in the southeastern region of Tunisia, where the sole source of water is from overexploited, salinized, and contaminated aquifers. Despite considerable advancements in studying groundwater hydrochemistry in the study area, Jeffara plain, further investigation is crucial to comprehensively assess groundwater quality in greater depth. The present study investigates the hydrochemistry of the Zeuss-Koutine (ZK) and a part of Mio-Plio-Quaternary (MPQ) groundwater of the Jeffara plain to identify groundwater quality and assess its suitability for drinking and irrigation purposes, as it serves as a vital water source for various sectors. Groundwater samples were collected from 43 exploitation wells and analyzed for temperature, pH, conductivity, major cations (Ca2+, Mg2+, K+ and Na+), major anions (Cl−, HCO3−, NO3−, SO42−), F−, trace elements and NH4+. The findings revealed that the groundwater hydrochemical type in the ZK aquifer is dominated by Na–Ca/SO4–Cl, while the MPQ samples fall under the Na–Ca–Mg/SO4–Cl category. Most of samples show too high concentrations of Na+, Ca2+, Cl−, SO42− and Fluoride. The studied groundwaters are highly affected by gypsum dissolution. The WQI indicate that 86% of samples have poor and very poor water quality and 14% are unsuitable for drinking. These findings are further supported by the TH measurements, which classify all water samples as very hard and unsuitable for drinking purposes. Irrigation water quality index indicate that samples fall in severe and high restriction, so, careful attention should be given to the high sodium and salinity content when used in intensive irrigation. The combination of water quality indices and GIS tools is performed to raise awareness among decision makers about groundwater availability and quality in the study area. Additionally, the need to develop strategies for the treatment and preservation of these valuable resources.

Study region: The Lakes Basin is located in the Main Ethiopian Rift. It covers the northern part of the rift valley basin, the Upper Awash River basin, and some sub-basins from the Omo River basin. Due to the presence of high fluoride (F-) content, natural contamination of groundwater has long been recognized as a water-related health issue in the area. Study focus: A multidisciplinary research effort, including geological, hydrogeological, hydrochemical, and geophysical investigations, was adopted to understand the 3D hydrogeological conceptual model and to evaluate F- enrichment in groundwater. New hydrological insights for the region: The 3D hydrogeological conceptual model shows a complex hydrogeological environment and a clear hydraulic interconnection between different aquifers. The geological setting has deeply influenced the geometry of the aquifers, recharge and discharge areas, and F- enrichment in groundwater. Two hydrogeological units, namely sedimentary and volcanic multi-aquifers, were identified. The analyses of groundwater circulation, flow paths, and distribution of F- concentrations in each aquifer were conducted. In groundwater, the concentration of fluoride varies from 0.1 to 68.9 mg L-1; in surface water, it ranges from 0.6 to 244.2 mg L-1. Fluoride concentration of 62 % of the water samples analyzed exceeded the 1.5 mg L-1 WHO threshold for fluoride concentration in drinking water. The proposed methodological approach has been demonstrated to be a powerful tool that could be applied in other similar areas.

The Skhira region is an agricultural area with interesting groundwater reserves. This water is also used for domestic and industrial purposes which contribute to its contamination. The present paper evaluates the hydrogeochemical characteristics of groundwater of the Skhira zone to investigate the impact of anthropogenic and natural sources of contamination and their suitability for drinking and for crop irrigation. Groundwater samples were collected from 30 wells distributed in the agricultural areas of the Skhira region in the dry season (August 2017). In the laboratory, the cation, anion, heavy metal, and the bacteriological analyses were performed and results were compared with the WHO standard for drinkability to determine whether the water in this system is within the acceptable limit for human consumption and irrigation by using some calculated indexes. Moreover, a multi-isotopic approach was employed to identify the main sources of pollution affecting the groundwater resources of the area. Chlorinated and sulfated calcium facies (Cl-SO 4 -Ca) were found for the majority of samples except some wells that showed a sodium chloride facies (Na-Cl). The high electrical conductivity pleading for a high salinity level is related to Na-Cl dissolution or to a cation exchange process. The source of nitrate is attributed to soil-N, fertilizer overuse in agriculture and manure. In fact, most samples showed to be affected by some organic source related with fecal pollution, confirmed by bacteriological and boron isotope analyses. However, due to the location of some sampling points close to the seawater, boron from seawater or marine aerosol cannot be discarded. Also, dissolved sulfate analyses, the Cl − versus SO 4 2− , and Cl − versus Na + showed a natural geogenic origin in the majority of samples. Overall, water quality was proved unsuitable for drinking in most sampling stations and for irrigation in some of them. The high concentrations of trace elements in these drinking waters have serious effects on the health of consumers. Therefore, it is advisable to study the trace element concentrations in this water and their relationship with health risk assessment.

This study presents a multi-disciplinary approach for the hydrogeological assessment and characterization of water resources in typical arid and semi-arid areas with high anthropogenic pressure, and where environmental conditions and political context prevent extensive field surveys. The use of a three-dimensional (3D) hydrogeological conceptual model, integrating hydrochemical and multi-isotope data, is proposed for the Batna and Biskra area (NE Algeria). Geological data were assembled in 3D geological software, from which a 3D hydrogeological conceptual model was constructed, which included the delineation of groundwater flow directions. The isotopic characterization, including deuterium and oxygen isotopic composition of water (δ2H and δ18O), and tritium (3H), provided information regarding recharge sources, flow pathways and residence times of groundwaters. Hydrochemical parameters, measured on the same samples, supported the interpretation of isotope data. All data were processed in a geographic information system (GIS) environment. The effectiveness of this approach was tested on a complex system of aquifers with high hydrogeological heterogeneity. Results show the important role the tectonic setting of an area can play in the hydrogeology and hydrochemistry of its principal groundwater systems. The fault network in the study region connects different aquifers, resulting in the mixing of groundwaters. The region most influenced by geological structures is the southern part of the study area, close to Biskra city. In fact, besides a limited contribution of recharge from rain and surface water derived from flood events, the recharge of the Cenozoic aquifers seems to proceed from the ascension of deeper Cretaceous groundwaters through the fault network, as indicated by temperature, bulk chemistry and in particular δ2H, δ18O and 3H results. In contrast, results suggest that the recharge of the low mineralized Maastrichtian waters is primarily influenced by local precipitation and runoff in the mountainous northern part of the study area. Tritium content, low salinity, and bulk chemistry all suggest such waters to be a mix of pre-bomb (deeper flow-lines within the aquifer) and recent water, with no contribution from the deepest Continental Intercalaire groundwaters. The proposed approach reduces ambiguity about the studied aquifer systems, greatly improves the conceptual understanding of their behaviour, and could provide insights into the vulnerability of the aquifers to different anthropogenic pollution phenomena. The methodology used appears to be a valid tool that could be applied to other geographical areas, to inform the design and implementation of efficient management strategies aimed at improving the quality and availability of water resources. Moreover, three-dimensional modelling methods are becoming increasingly applied to different aspects of groundwater management, to obtain a detailed picture of subsurface conditions.

Fluoride represents one of the most severe natural contaminant that affects groundwater as well as rivers and soils. More than 200 million people worldwide consume water with fluoride concentration exceeding the WHO guideline of 1.5 mg L-1 (WHO, 2008). Besides dental fluorosis, an excess of fluoride may cause skeletal fluorosis, a bone disease of severe pain. In the East African Rift Valley System (EARS) about 90% of the population exhibit varying degrees of fluorosis symptoms (Yoder et al. 1998) corresponding to over 80 million people (Smedley et al. 2002). FLOWERED (deFLuoridation technologies for imprOving quality of WatEr and agRo-animal products along the East African Rift Valley in the context of aDaptation to climate change, http://www.floweredproject.org) is an H2020 European project whose overall objective is to contribute to the development of a sustainable water management system. The study focus on areas affected by fluoride contamination in water, soils and food in Ethiopia, Kenya and Tanzania, with the aim of improving the living standards for local population. Here we present the study of representative rocks and soils samples with the aim to identify what minerals bear F and what is their alterability and capacity in releasing it to the water.

Groundwater vulnerability mapping is largely used as a modeling tool to delineate areas susceptible to pollution and to protect groundwater resources from this threat. The Zeuss-Koutine aquifer, which constitutes an important source of drinking water in the Southeastern Tunisia, is subjected to an intensive exploitation and threatened by pollution due mainly to the industrial zone of Koutine. The groundwater circulates in fissured and karstified limestone. Aquifer vulnerability has been assessed using the SINTACS method. The different parameters of the SINTACS model were collected from several sources and converted into thematic maps using ArcGis. Each SINTACS parameter was assigned a weight and rating based on a range of information within the parameter. The weight of each parameter depends on the impact of potential pollution. The analysis of vulnerability map to pollution shows that the Southeastern part of the aquifer and the Wadis beds are more susceptible to pollution. The measured nitrate concentrations of two sampling campaigns carried out in high and dry water seasons are coherent with the SINTACS model results.

1 Department of Chemical and Geological Sciences, University of Cagliari, Via Trentino 51-09127 Cagliari, Italy, acarletti@uniss.it 2 Desertification Research Centre (NRD), University of Sassari, Viale Italia 39-07100 Sassari, Italy 3 Grup de Mineralogia Aplicada i Geoquímica de Fluids, Dpt. Mineralogia, Petrologia i Geologia Aplicada, Fac. Ciències de la Terra, Universitat de Barcelona (UB), Martí Franquès s/n-08028 Barcelona, Spain 4 Institutes des Région AridesIRA, Route du Djorf Km 22.5-Médenine, Tunisie

Artificial recharge improves several water quality parameters, but has only minor effects on recalcitrant pollutants. To improve the removal of these pollutants, we added a reactive barrier at the bottom of an infiltration basin. This barrier contained aquifer sand, vegetable compost, and clay and was covered with iron oxide dust. The goal of the compost was to sorb neutral compounds and release dissolved organic carbon. The release of dissolved organic carbon should generate a broad range of redox conditions to promote the transformation of emerging trace organic contaminants (EOCs). Iron oxides and clay increase the range of sorption site types. In the present study, we examined the effectiveness of this barrier by analyzing the fate of nine EOCs. Water quality was monitored before and after constructing the reactive barrier. Installation of the reactive barrier led to nitrate-, iron-, and manganese-reducing conditions in the unsaturated zone below the basin and within the first few meters of the saturated zone. Thus, the behavior of most EOCs changed after installing the reactive barrier. The reactive barrier enhanced the removal of some EOCs, either markedly (sulfamethoxazole, caffeine, benzoylecgonine) or slightly (trimethoprim) and decreased the removal rates of compounds that are easily degradable under aerobic conditions (ibuprofen, paracetamol). The barrier had no remarkable effect on 1H-benzotriazole and tolyltriazole.

Soil-aquifer processes have proven to work as a natural treatment for the attenuation of numerous contaminants during artificial recharge of groundwater. Nowadays, significant scientific effort is being devoted to understanding the fate of pharmaceuticals in subsurface environments, and to verify if such semipersistent organic micropollutants could also be efficiently removed from water. In this context we carried out a series of batch experiments involving aquifer material, selected drugs (initial concentration of 1 μg/L and 1 mg/L), and denitrifying conditions. Diclofenac and sulfamethoxazole exhibited an unreported and peculiar behavior. Their concentrations consistently dropped in the middle of the tests but recovered toward the end, which suggest a complex effect of denitrifying conditions on aromatic amines. The transformation products Nitro-Diclofenac and 4-Nitro-Sulfamethoxazole were detected in the biotic experiments, while nitrite was present in the water. Their concentrations developed almost opposite to those of their respective parent compounds. We conjecture that this temporal and reversible effect of denitrifying conditions on the studied aromatic amines could have significant environmental implications, and could explain at least partially the wide range of removals in subsurface environments reported in literature for DCF and SMX, as well as some apparent discrepancies on SMX behavior.

The fate of the three environmentally relevant β-blockers atenolol, metoprolol and propranolol has been studied in batch experiments involving aquifer material and nitrate reducing conditions. Results from the about 90d long tests indicate that abiotic processes, most likely sorption, jointly with biotransformation to atenololic acid were responsible for the 65% overall removal observed for atenolol. Zero order kinetics, typical of enzyme-limited reactions, controlled the transformation of this beta blocker to its corresponding carboxylic acid. The mass balance evidences that no mineralization of atenolol occurs in the biotic experiment and that atenololic acid is more stable than its parent compound under the studied conditions. This finding stresses the importance of considering atenololic acid as target compound in the environmental studies on the fate of atenolol. For metoprolol and propranolol the results from the experiment suggest a slower sorption to be the dominant removal process, which led to final decreases in concentrations of 25–30% and 40–45%, respectively. Overall, the removals observed in the experiments suggest that subsurface processes potentially constitute an alternative water treatment for the target beta-blockers, when compared to the removals reported for conventional wastewater treatment plants.

The antibiotic sulfonamide drug sulfamethoxazole (SMX) is extensively used in both human and veterinary medicine. Since it cannot be completely eliminated by the typical state-of-the-art wastewater treatment technology, it is frequently detected in the water cycle. SMX, as aromatic amine, can undergo abiotic transformations with the under denitrifying conditions produced nitrogen species nitric oxide (NO) and nitrite (NO2-). NO and aromatic amines are commonly known to form diazonium cations. Depending on the reaction conditions the diazonium cation disintegrates under cleavage of elementary nitrogen and substitutes its diazo-group by an NO(2)(-)group or by hydrogen. Following this approach, two transformation products (TPs) of the persistent SMX under denitrifying conditions were hypothesized and synthesized: 4-nitro-N-(5-methylisoxazol-3-yl)-benzenesulfonamide (4-nitro-SMX) and N-(5-methylisoxazol-3-yl)-benzenesulfonamide (desamino-SMX). The synthesized compounds were identified by Nuclear Magnetic Resonance (NMR) spectroscopy and used as reference standards for their confirmation and quantification in denitrifying water/sediment batch experiments and in environmental samples. During the denitrifying degradation experiment SMX was no longer detected after 10 days whereas increasing concentrations of the two TPs were observed. However, at day 87 the SMX concentration recovered to 53 +/- 16% of the initial concentration after most of the nitrate was consumed. A retransformation of 4-nitro-SMX to SMX was postulated and confirmed by another anoxic water/sediment test in the absence of nitrate as electron acceptor. Both TPs were also detected in karst spring samples, highlighting the need and benefit of focusing on transformation products in environmental studies. Furthermore, the consideration of the retransformation potential of 4-nitro-SMX can substantially improve the understanding of SMX behavior during processes such as bank filtration and artificial recharge. (C) 2012 Elsevier Ltd. All rights reserved.

La recarrega artificial de les aigües subterrànies consisteix en infiltrar aigua als aqüífers per mitjà de les instal·lacions dissenyades per a tal fi i representa una eina important en la gestió dels recursos. A més de l’augment dels recursos d'aigües subterrànies, la recàrrega pot suposar una millora natural de la seva qualitat durant el seu pas pel subsòl. Els processos que tenen lloc en el sistema sòl-aqüífer (filtració, adsorció, reaccions de mescla , redox, biodegradació, etc) han demostrat produir una millora integral de la qualitat de l'aigua, eliminant també de manera efectiva una sèrie de contaminants orgànics. En l'actualitat, la qüestió és saber si la contaminació pels microcontaminants orgànics emergents, és a dir, productes farmacèutics, cosmètics, hormones, drogues il·lícites, pesticides i tensioactius, també es poden atenuar de forma natural. Alguns d’aquests compostos no són completament eliminats pels tractaments d'aigua residual convencionals, essent introduïts contínuament en els cursos d’aigua superficials pels efluents de les plantes de tractament. Malgrat la baixa concentració (ng/L i μg/L), la seva presència en el medi ambient és actualment un problema per a la vida aquàtica i la salut humana. En aquest context, la recàrrega artificial pot esdevenir una alternativa potencial o un tractament complementari per a l'eliminació de microcontaminants orgànics de l’aigua. Hi ha evidències que les condicions redox predominants podrien influir en el comportament d’aquests productes en l'aqüífer. No obstant, en el cas dels microcontaminants emergents, el coneixement sobre aquest tema és encara molt limitat. L’objectiu principal d’aquesta tesi és doncs investigar el possible efecte de les condicions redox sobre el destí de microcontaminants orgànics, la majoria dels quals són contaminants emergents. El treball està motivat pels projectes de recàrrega artificial amb aigua del riu Llobregat (Barcelona, Espanya). L’estudi es basa en experiments de laboratori (batch) utilitzant materials naturals de l'aqüífer, microcontaminants en concentracions ambientals (1 μg/L de cada compost), i unes condicions ambientals similars als llocs de recàrrega artificial. Afegint les quantitats adequades d’acceptors i donadors d’electrons s’han obtingut i mantingut les diferents condicions redox anaeròbies en cada conjunt de microcosmos. Els experiments inclouen sèries biòtiques i abiòtiques per separar la biodegradació de contaminants de l’adsorció a la superfície dels sòlids i altres processos abiòtics. També s’ha dut a terme un experiment amb una major concentració de contaminants (1 mg/L de cada compost), per comprovar la representativitat dels estudis convencionals. Els objectius finals del treball són: 1) identificar les condicions redox més favorables per eliminar de l'aigua els compostos seleccionats, a fi de ser promogudes en l’assaig de camp; i 2) mesurar les velocitats de les reaccions de degradació per tal de preveure el comportament dels micrcontaminants en el aqüífer. La recarga artificial de acuíferos, que consiste en la infiltración de agua subterránea en instalaciones diseñadas para tal fin, constituye una importante herramienta en la gestión de recursos hídricos. Más allá de aumentar los recursos de aguas subterráneas, suscita gran interés la capacidad de tratamiento natural que confiere el tránsito sub-superficial a las aguas. Los procesos que tienen lugar en el sistema suelo-acuífero (filtración, adsorción, mezcla, reacciones redox, biodegradación, etc.) permiten una mejora general de la calidad del agua, eliminando incluso diversos contaminantes orgánicos. En la actualidad, el reto es entender si los microcontaminantes orgánicos emergentes, es decir farmacéuticos, productos de cuidado personal, hormonas, drogas ilícitas, plaguicidas y tensioactivos, puedan también ser atenuados. Muchos de ellos no son completamente eliminados en tratamientos de agua convencionales, siendo introducidos constantemente en aguas superficiales por los efluentes de las plantas de tratamiento de aguas residuales. A pesar de sus baja concentraciones (ng/L and μg/L), su omnipresencia en el medioambiente es actualmente causa de preocupación para la vida acuática y la salud humana. En este contexto, la recarga artificial puede representar un tratamiento alternativo o complementario para la eliminación de microcontaminantes orgánicos de las aguas. Hay evidencias de que las condiciones redox dominantes pueden influenciar el comportamiento de contaminantes orgánicos convencionales en los acuíferos. Sin embargo, en el caso de los microcontaminantes emergentes los conocimientos sobre este tema es todavía limitado. El principal objetivo de esta tesis, motivada por proyectos de recarga artificial con aguas del río Llobregat (Barcelona, España), es investigar el efecto potencial de las condiciones redox sobre el comportamiento de microcontaminantes orgánicos seleccionados (la mayoría de los cuales son contaminantes emergentes) durante la recarga artificial. El estudio se basa en experimentos batch de laboratorio usando material natural del acuífero, microcontaminantes en concentraciones ambientales (1 μg/L cada compuesto), y condiciones verosímiles en enclaves de recarga artificial. Añadiendo cantidades adecuadas de aceptadores y donadores de electrones, fueron establecidas y se mantuvieron diferentes condiciones redox anaeróbicas (condiciones nitrato-, manganeso-, hierro- y sulfato-reductoras) en cada grupo de microcosmos. Se llevaron a cabo series bióticas y abióticas para separar la biodegradación de los contaminantes (mineralización biótica o transformación) de los procesos de adsorción y de otros procesos abióticos. También fue realizado un experimento para alta concentración de contaminantes (1 mg/L cada compuesto), para comprobar la representatividad de los estudios convencionales. El objetivo final de este trabajo es identificar 1) las condiciones redox más favorables para la eliminación del agua de los contaminantes seleccionados, para su posterior simulación en el sitio piloto, y 2) las tasas de eliminación de esos contaminantes, para predecir sus comportamientos en el acuífero. Artificial recharge of groundwater, consisting in infiltrating water into aquifers by means of properly designed facilities, represents an important tool in water resources management. Beside its quantitative benefits (augmentation of groundwater resources, long term underground storage, etc.), a great interest for this technique is related to the natural treatment provided to water by subsurface passage. The processes occurring in the soil-aquifer system (filtration, sorption, mixing, redox reactions, biodegradation, etc.) have indeed proven to yield an overall improvement of water quality, removing effectively also a number of organic contaminants. At present time, the issue is to understand whether emerging organic micropollutants, i.e. pharmaceuticals, personal care products, hormones, illicit drugs, pesticides and surfactants, can also be removed. A number of these compounds are not completely removed by conventional water treatments, being thus introduced continuously into surface water bodies by the discharge of wastewater treatment plants effluents. In spite of their low concentration (ng/L and μg/L), their ubiquitous presence in the environment is currently a cause of concern for aquatic life and human health. In this context, artificial recharge may represent a potential alternative or complementary treatment for the removal of organic micropollutants from water. Evidences showed that, among the factors influencing the fate of conventional organic contaminants in the aquifer, the predominant redox conditions could play an important role. Yet, in the case of emerging micropollutants the knowledge on this topic is still limited. The main objective of this thesis, motivated by artificial recharge practices using Llobregat river water (Barcelona, Spain), is to investigate on the potential effect of redox conditions on the fate of selected organic micropollutants, most of them being emerging contaminants, during artificial recharge of groundwater. The study is based on batch experiments involving natural aquifer material, micropollutants at environmental concentrations (1 μg/L each compound), and settings feasible at artificial recharge sites. Different anaerobic redox conditions (namely, nitrate-, manganese-, iron- and sulphate-reducing conditions) were promoted and sustained in each set of microcosms by adding adequate quantities of electron donors and acceptors. The experiments included biotic and abiotic series to separate contaminant’s biodegradation (i.e. biotic mineralization or transformation) from sorption and other abiotic processes. An experiment at higher pollutants concentration (1mg/L each compound) was also carried out, to check the representativeness of studies at concentrations easier to be tested and analysed. The ultimate aim of the work is to identify 1) the most favourable redox conditions for the removal of the target compounds from water, for their following stimulation in the field test site, and 2) pollutants’ removal rates, to predict their behaviour in the aquifer.