Selenium (Se) is an essential micro-nutrient for humans, but can be toxic at high levels of intake. Se deficiency and Se toxicity are linked with serious diseases, with some regions worldwide experiencing Se deficiency due to Se-poor rocks and soils and other areas dealing with Se toxicity due to the presence of Se-enriched geologic materials. In addition, Se is consumed primarily through plants that take up Se from soil and through animal products that consume these plants. Hence, the soil and groundwater system play important roles in determining the effect of Se on human health. This paper reviews current understanding of Se fate and transport in soil and groundwater systems and its relation to human health, with a focus on alluvial systems, soil systems, and the interface between alluvial systems and Cretaceous shale that release Se via oxidation processes. The review focuses first on the relation between Se and human health, followed by a summary of Se distribution in soil-aquifer systems, with an emphasis on the quantitative relationship between Se content in soil and Se concentration in underlying groundwater. The physical, chemical, and microbial processes that govern Se fate and transport in subsurface systems then are presented, followed by numerical modeling techniques used to simulate these processes in study regions and available remediation strategies for either Se-deficient or Se-toxic regions. This paper can serve as a guide to any field, laboratory or modeling study aimed at assessing Se fate and transport in groundwater systems and its relation to human health.

The geomorphological evolution of a sand-dune barrier in Buenos Aires, Argentina, is analyzed as a factor regulating the fresh groundwater reserves available. The impact of geomorphological evolution and the consequences for the social and economic development of two coastal areas are assessed. This is one of the most important tourist destinations in the country; for study purposes, it was divided into a northern sector and a southern sector. In the southern sector, the exploitable groundwater is associated with the Holocene and upper Pleistocene geomorphological evolution, which generated three interrelated aquifer units, constituting a system whose useful thickness reaches at least 45 m. In contrast, the northern sector is restricted to two Holocene aquifer units, whose total thickness is on the order of 12 m. The morphological characteristics and the occurrence of the largest fresh groundwater reserves in the southern sector are indicators of better conditions for economic growth, which is mainly reflected on the expansion of real estate ventures. The relationships of transmissivity vs area of real estate ventures (Arev), and total water consumption vs Arev, are indicators for the sustainable management of the water resources. The approach chosen may be used by decision makers in other regions to assess the feasibility of future tourism projects on the basis of the availability of water resources associated with geomorphological features.

This study aims to determine the groundwater flow in a large area of the Venice (northeast Italy) lagoon that is under great anthropogenic pressure, which is influencing the regional flow in the surficial aquifer (about 30 m depth). The area presents several elements that condition the groundwater flow: extraction by means of drainage pumps and wells; tidal fluctuation; impermeable barriers that define part of the coastline, rivers and artificial channels; precipitation; recharge, etc. All the elements were studied separately, and then they were brought together in a numerical groundwater flow model to estimate the impact of each one. Identification of the impact of each element will help to optimise the characteristics of the Porto Marghera remediation systems. Longstanding industrial activity has had a strong impact on the soil and groundwater quality, and expensive and complex emergency remediation measures in problematic locations have been undertaken to ensure the continuity of industrial and maritime activities. The land reclamation and remediation works withdraw 56–74% of the water budget, while recharge from the river accounts for about 21–48% of the input. Only 21–42% of groundwater in the modelled area is derived from natural recharge sources, untouched by human activity. The drop of the piezometric level due to the realization of the upgradient impermeable barrier can be counteracted with the reduction of the pumping rate of the remediation systems.

Groundwater is typically the only water source in arid regions, and its circulation processes should be better understood for rational resource exploitation. Stable isotopes and major ions were investigated in the northeastern Tengger Desert, northern China, to gain insights into groundwater recharge and evolution. In the northern mountains, Quaternary unconsolidated sediments, exposed only in valleys between hills, form the main aquifer, which is mainly made of aeolian sand and gravel. Most of the mountain groundwater samples plot along the local meteoric water line (LMWL), with a more depleted signature compared to summer precipitation, suggesting that mountain groundwater was recharged by local precipitation during winter. Most of the groundwater was fresh, with total dissolved solids less than 1 g/L; dominant ions are Na⁺, SO₄ ²⁻ and Cl⁻, and all mineral saturation indices are less than zero. Evaporation, dissolution and cation exchange are the major hydrogeochemical processes. In the southern plains, however, the main aquifers are sandstone. The linear regression line of δD and δ ¹⁸O of groundwater parallels the LMWL but the intercept is lower, indicating that groundwater in the plains has been recharged by ancient precipitation rather than modern. Both calcite and dolomite phases in the plains groundwater are close to saturation, while gypsum and halite can still be dissolved into the groundwater. Different recharge mechanisms occur in the northern mountains and the southern plains, and the hydraulic connection between them is weak. Because of the limited recharge, groundwater exploitation should be limited as much as possible.

Vertical electrical sounding was used for assessing the suitability of the drill sites in crystalline areas within a water supply project in Nampula Province in Mozambique. Many boreholes have insufficient yield (<600 L/h). Electrical resistivity tomography (ERT) was carried out over seven boreholes with sufficient yield, and five boreholes with insufficient yield, in Rapale District, in an attempt to understand the reason for the failed boreholes. Two significant hydrogeological units were identified: the altered zone (19–220 ohm-m) with disintegrated rock fragments characterized by intermediate porosity and permeability, and the fractured zone (>420 ohm-m) with low porosity and high permeability. In addition to this, there is unfractured nonpermeable intact rock with resistivity of thousands of ohm-m. The unsuccessful boreholes were drilled over a highly resistive zone corresponding to fresh crystalline rock and a narrow altered layer with lower resistivity. Successful boreholes were drilled in places where the upper layers with lower resistivity correspond to a well-developed altered layer or a well-fractured basement. There are a few exceptions with boreholes drilled in seemingly favourable locations but they were nevertheless unsuccessful boreholes for unknown reasons. Furthermore, there were boreholes drilled into very resistive zones that produced successful water wells, which may be due to narrow permeable fracture zones that are not resolved by ERT. Community involvement is proposed, in choosing between alternative borehole locations based on information acquired with a scientifically based approach, including conceptual geological models and ERT. This approach could probably lower the borehole failure rate.

Groundwater age has been used to map renewability of water resources within four groups: strong, partial, and rare renewability, and non-renewable. The Baiyang alluvial fan in NW China is a representative area for examining groundwater recharge from river infiltration and for mapping groundwater renewability, and it has been investigated using multiple isotopes and water chemistry. Systematic sampling included 52 samples for ²H and ¹⁸O analysis and 32 samples for ³H, ¹³C and ¹⁴C analysis. The δ¹³C compositions remain nearly constant throughout the basin (median −12.7‰) and indicate that carbonate dissolution does not alter ¹⁴C age. The initial ¹⁴C activity of 80 pmC, obtained by plotting ³H and ¹⁴C activity, was used to correct groundwater ¹⁴C age. The results show that areas closer to the river consist of younger groundwater ages; this suggests that river infiltration is the main recharge source to the shallow groundwater system. However, at distances far away from the river, groundwater ages become older, i.e., from modern water (less than 60 year) to pre-modern water (from 60 to 1,000 years) and paleowater (more than 1,000 yeas). The four classifications of groundwater renewability have been associated with different age ranges. The area of shallow groundwater with strong renewability accounts for 74% of the total study area. Because recharge condition (river infiltration) controls overall renewability, a groundwater renewability map is of significant importance to the management of groundwater exploitation of this area as well as other arid groundwater basins.

Urban groundwater has often been over-exploited for industrial uses. Now, this usage tends to be reduced or the resource abandoned due to pollution and/or changes in land use. The use and the subsequent disuse of groundwater has resulted in rising water tables that damage underground structures (e.g., building basements and underground car parks and tunnels), leading to the need for additional pumping in urban areas. In the case of the underground parking lot of Sant Adrià del Besòs (Barcelona, NE Spain), large amounts of urban groundwater are pumped to avoid seepage problems. Can this pumped groundwater be used for other purposes (e.g., drinking water and urban irrigation) instead of wasting this valuable resource? To answer this question, it was necessary to quantify the groundwater recharge and to assess the evolution of groundwater quality. The limiting factor at this study site is the groundwater quality because ammonium and some metals (iron and manganese) are present at high concentrations. Hence, further treatment would be needed to meet drinking water requirements. The pumped groundwater could also be used for supplementing river flow for ecological benefit and/or for mitigating seawater intrusion problems. Currently, only a small amount of this urban groundwater is used for cleaning public areas and watering public gardens. This situation highlighted the urgent need to manage this resource in a responsible and more efficient manner, especially in moments of high water demand such as drought periods.

The purpose of the research was to determine the content of Cr, Cd and Pb, the main metals used in the manufacture of pesticides frequently used in potato and carrot crops; these compounds remain in the solid waste of wastewater, since they do not degrade quickly or if they make parts of the molecule adhere to soil particles or organic matter molecules; in this situation they were subjected to the composting process, mixed with organic materials (Feathers, manure, wood sawdust). The study was composed of 5 treatments with 3 repetitions, together pH and Tº measurements were made during the course of the process, after composting, samples were taken from each pile to be analyzed in the laboratory, the results showed that the behavior of Tº has meaningful differences between treatments, regarding the behavior of pH and the presence of heavy metals, the test did not report significant differences, although all reported heavy metals, their values are very low compared to INCONTEC standard 5167, therefore it is considered a harmless compost for its use as an organic amendment. | La investigación tuvo como finalidad determinar el contenido de Cr, Cd y Pb, principales metales utilizados en la fabricación de pesticidas empleados&nbsp; recuentemente en los cultivos de papa y zanahoria; estos compuestos permanecen en los desechos sólidos del agua residual, dado que no se degradan rápidamente o si lo hacen partes de la molécula quedan adheridas a las partículas de suelo o moléculas de materia orgánica; ante esta situación fueron sometidas al proceso de compostaje, mezcladas con materiales orgánicos (plumas, estiércoles, aserrín de madera). El estudio estuvo compuesto de 5 tratamientos con 3 repeticiones, conjuntamente se realizaron mediciones de pH y Tº durante el transcurso del proceso. Culminado el compostaje, se tomaron muestras de cada pila para ser analizadas en laboratorio; los resultados arrojaron que el comportamiento de la Tº tiene diferencias significativas entre tratamientos, con respecto al comportamiento del pH y presencia de metales pesados. El ensayo no reportó diferencias significativas. Aunque todos reportaron metales pesados, sus valores son muy bajos respecto a la norma 5167 del ICONTEC, por consiguiente se considera un compost inocuo para su utilización como enmienda orgánica. | L’objectif de la recherche avait comme but de déterminer la présence de Cr, Cd et Pb, les principaux métaux utilisés dans la fabrication des pesticides qui sont fréquemment utilisés dans les cultures de pommes de terre et carottes ; ces composés restent dans les déchets solides des eaux usées, étant donné que leur dégradation ne s’effectue pas rapidement et que, si des particules du sol ou de la matière organique se forment, dans ce cas, ils sont alors soumis au processus du compost, en mélange avec les matières organiques (plumes, lisier et sciure de bois). L’étude était composée de 5 traitements avec 3 répétitions, des mesures de pH et de Tº ont été effectuées au cours du processus, après compostage, des échantillons ont été collectés sur chaque tas pour être analysés dans le laboratoire, les résultats montrent que le comportement du Tº est différent de façon significative en fonction du pH et la présence des métaux lourds, le test ne fait état de différences significatives, mais les métaux lourds déclarés sont très faibles en comparaison des normes INCONTEC 5167, leur contenu est donc considéré comme un compost non dangereux pour une application organique en amendement. &nbsp; | O objetivo da pesquisa foi determinar o teor de Cr, Cd e Pb, os principais metais utilizados na fabricação de pesticidas frequentemente utilizados em lavouras de batata e cenoura; estes compostos permanecem nos resíduos sólidos das águas residuais, já que eles não se degradam rapidamente ou se o fazem, partes da molécula permanecem ligadas a partículas do solo ou moléculas de matéria orgânica; antes desta situação, eles foram submetidos ao processo de compostagem, misturado com materiais orgânicos (penas, esterco, serragem de madeira). O estudo consistiu de 5 tratamentos com 3 repetições, foram feitas as medições de pH e T durante o processo, a compostagem foi concluída, amostras foram retiradas de cada pilha para serem analisadas em laboratório, os resultados mostraram que o comportamento do T apresenta diferenças significativas entre os tratamentos, no que diz respeito ao comportamento do pH e presença de metais pesados, o ensaio não relatou diferenças significativas; Embora todos relatem metais pesados, seus valores são muito baixos em relação à norma 5167 do INCONTEC, portanto, é considerado um composto inofensivo para seu uso como uma emenda orgânica.

A coupled groundwater-flow-modelling and vulnerability-mapping methodology for the management of karst aquifers with spatial variability is developed. The methodology takes into consideration the duality of flow and recharge in karst and introduces a simple method to integrate the effect of temporal storage in the unsaturated zone. In order to investigate the applicability of the developed methodology, simulation results are validated against available field measurement data. The criteria maps from the PaPRIKa vulnerability-mapping method are used to document the groundwater flow model. The FEFLOW model is employed for the simulation of the saturated zone of Palaikastro-Chochlakies karst aquifer, in the island of Crete, Greece, for the hydrological years 2010–2012. The simulated water table reproduces typical karst characteristics, such as steep slopes and preferred drain axes, and is in good agreement with field observations. Selected calculated error indicators—Nash-Sutcliffe efficiency (NSE), root mean squared error (RMSE) and model efficiency (E′)—are within acceptable value ranges. Results indicate that different storage processes take place in different parts of the aquifer. The north-central part seems to be more sensitive to diffuse recharge, while the southern part is affected primarily by precipitation events. Sensitivity analysis is performed on the parameters of hydraulic conductivity and specific yield. The methodology is used to estimate the feasibility of artificial aquifer recharge (AAR) at the study area. Based on the developed methodology, guidelines were provided for the selection of the appropriate AAR scenario that has positive impact on the water table.