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The knowledge of soil moisture spatio-temporal variability is highly relevant for water resources management. This is especially significant in highly demanding areas of arid and semiarid regions where a sensitive ecosystem, agriculture and recreational areas can converge. This study reports an analysis of the spatial-temporal variability of soil moisture data for a small to medium-scale network in a coastal wetland of southwestern Spain. Measurements were taken from 5 sites located in the Doñana National Park, with an extension of approx. 25 × 3 km over the time-period of one hydrological year from September 2017 to September 2018. Absolute soil moisture was separated in two components: the temporal mean (time-invariant term) and the deviations from the mean or anomalies (time-variant term). The time-invariant component was generally the main contributor to the total spatial variance of absolute soil moisture data and it was mostly controlled by the groundwater levels in the area. Nevertheless, the time variant terms have a huge effect on soil moisture variability in very dry states at this site. Time-dependent patterns were found between average soil moisture state and the variance and covariance both of the time-variant and time-invariant components of soil moisture, which could be used for the up and downscaling of soil moisture from satellite data. Those patterns were only affected by heavy rainfalls giving rise to hysteretic behavior. This study shows that even though groundwater level is a time-variant variable, it significantly affects soil moisture’s time-variant and time-invariant terms.

There is an increasing need for accurate groundwater-level (GWL) prediction to support effective seasonal water management. It is desirable for forecasting tools to be not only accurate but also ac...

Dune belts are crucial for the recharge of coastal aquifers. In spite of their hydrological relevance for the maintenance of precious natural wetland and wildlife environments and a range of other ecosystemservices, only limited knowledge of soil water dynamics in dune belts is currently available. This study presents soilwater balance components measured during one hydrological year using a high precision meteo-lysimeter with lower boundary control installed in a coastal dune belt under a dry subhumid climate in southern Spain close to the Atlantic Ocean. The site is equipped with a cylindrical lysimeter of 1 m2 surface and 1.50 m height (METER Group, Inc. USA) and a weighing resolution of 10 g, 2 SC650 soil moisture sensors (Campbell Scientific, Logan, UT) and 1 automatic meteorological station. The lower boundary condition at the bottom of the lysimeter is controlled at 1.4 m depth by a bidirectional peristaltic pump to maintain field conditions. Results show a recharge rate of 64% of the precipitation measured by the lysimeter. Diurnal oscillations of the measured upper boundary flow during days without rainfall represented vapor adsorption and real evaporation rates ranging between 0.3 and 0.4 mm/day and 0.4 and 0.6 mm/day, respectively throughout the whole year summing up an annual vapor adsorption of 77mm. The measured precipitation of the lysimeter exceeded pluviometer data by 13% as a result of vapor adsorption. The presented results provide a precise balance of soilwater components in a coastal dune belt including the relevant contribution of vapor flow., Unidad de Sevilla, Instituto Geológico y Minero de España, España, Departamento de Física Aplicada, Universidad de Córdoba, España, Centro Alameda del Obispo, Investigación y Formación Agraria y Pesquera, España, Instituto Geológico y Minero de España, España

The δ2H and δ18O composition of 77 precipitation samples collected between January 2014 and April 2019 from two sites across the Guadalquivir Basin, SW Spain, were analyzed. Sampling was performed within intervals of at least 14 days basis if rain occurred but frequently intervals were longer according to the rainfall incidence. Precipitation weighted averages and local meteoric water lines are presented for use in hydrological applications. δ2H and δ18O values show a remarkably high variability attributed to the influence of Atlantic and Mediterranean vapor sources. Precipitation weighted average d-excess values of 12.5-13 ‰ confirm the Western Mediterranean influence. Temperature and amount effects were found to be weak but significant influence of secondary evaporation for single rainfall events during summer was identified by reduced d-excess values and enriched isotopic signatures plotting close or below the Global Meteoric Water line (GMWL). Isotopic signatures of both sites are very similar in general and any temperature related urban effects of Seville city compared to the rural site Doñana could not be identified with the present data

The δ2H and δ18O composition of 77 precipitation samples collected between January 2014 and April 2019 from two sites across the Guadalquivir Basin, SW Spain, were analyzed. Sampling was performed within intervals of at least 14 days basis if rain occurred but frequently intervals were longer according to the rainfall incidence. Precipitation weighted averages and local meteoric water lines are presented for use in hydrological applications. δ2H and δ18O values show a remarkably high variability attributed to the influence of Atlantic and Mediterranean vapor sources. Precipitation weighted average d-excess values of 12.5-13 ‰ confirm the Western Mediterranean influence. Temperature and amount effects were found to be weak but significant influence of secondary evaporation for single rainfall events during summer was identified by reduced d-excess values and enriched isotopic signatures plotting close or below the Global Meteoric Water line (GMWL). Isotopic signatures of both sites are very similar in general and any temperature related urban effects of Seville city compared to the rural site Donana could not be identified with the present data

The study presents daily values of inward and outward vapor flux crossing the soil-atmosphere boundary in dependence on meteorological parameters and soil moisture. Measurements of vapor flux, soil moisture and meteorological parameters were evaluated during days without rainfall between 2015 and 2019. Vapor flux data were obtained at 1 min intervals by a precision lysimeter installed in the Doñana National Park, southwest Spain. Meteorological data were measured on-site at 10-min intervals, including temperature, relative humidity, wind velocity and net radiation. After manual and automatic noise elimination of the lysimeter data, time series of a summer and winter period were generated for selected relevant parameters. Furthermore, daily cumulative data of inward and outward vapor flux were calculated for the entire period and analyzed for their control by meteorological parameters and soil moisture. Results show moderate correlations of daily outward vapor flux on the diurnal amplitudes of temperature and humidity whereas daily inward vapor indicates moderate correlations with temperature and soil moisture. A correction coefficient for potential evaporation to estimate actual evaporation was determined based on soil moisture and air temperature., Unidad de Sevilla, Instituto Geológico y Minero de España, España, Departament d'Enginyeria Civil i Ambiental, Universitat Politècnica de Catalunya, España, Grupo de Hidrogeología, Universitat Politècnica de Catalunya, España, Grupo de Hidrogeología, Consejo Superior de Investigaciones Científicas, España

The growing consumption of pharmaceuticals together with their incomplete removal in wastewater treatment plants (WWTPs) implies the occurrence of these compounds in natural water resources. To investigate the natural attenuation of selected pharmaceuticals (caffeine, acetaminophen, sulfamethoxazole, naproxen and carbamazepine) during vadose zone infiltration, unsaturated column (L 26.67 cm, Ø 7.62 cm) experiments, filled with a sandy-loamy soil, were performed using two input concentrations (100 and 1000 μg L−1). The software Hydrus 1D was used to simulate experimental data. Caffeine and acetaminophen were never detected at the column outlet indicating a low environmental concern. On the other hand, attenuation of the detected pharmaceuticals could be reproduced by a combination of retardation and removal approaches. Carbamazepine is among the selected contaminants the most persistent. A dependence of removal rates on input concentrations was detected for sulfamethoxazole (μw from 2.78 d−1 to 1.16 d−1) and naproxen (μw from 1.16 d−1 to 0.63 d−1) attributed mainly to decreased metabolism of microorganisms when a higher input concentration is applied. Two transformation products (TPs) (N4-Acetylsulfamethoxazole and epoxycarbamazepine) derived from sulfamethoxazole and carbamazepine transformation, respectively, were detected during the experiment with the highest input concentration., Institutos Madrileño de Estudios Avanzados Agua, España, Unidad de Sevilla, Instituto Geológico y Minero de España, España, Departamento de Geología, Geografía y Medio Ambiente, Universidad de Alcalá de Henares, España

Datos suplementarios en: https://doi.org/10.1016/j.jhydrol.2020.125580, Precipitation measurements are performed mostly by simple automatic rain gauges installed at a certain level above the ground surface, but these methods are often affected by significant measurement errors due to the deformation of the wind field above the rain gauge orifice. In recent years precision lysimeters have emerged, providing an efficient means to improve rainfall measurements and to check the reliability of the standard devices. This article reports comparative rainfall measurements by different devices including a precision lysimeter, two tipping bucket rain gauges and one weighing rain gauge. Rainfall and meteorological data were collected within 3–4.5 years of operation using intervals of 1, 10 and 30 min for registration providing a large data set of exclusively rainfall precipitation without snow and without the effect of freezing. Results show very good agreement of lysimeter, tipping bucket 1 and the weighing pluviometer measurements without any need of precipitation correction, whereas tipping bucket 2 rain gauge underestimated precipitation., Unidad de Sevilla, Instituto Geológico y Minero de España, España, Departament d’Enginyeria Civil i Ambiental, Universitat Politècnica de Catalunya, España

A tailing impoundment situated in the mining district of La Carolina (Spain), which stores waste resulting from the washing of Pb and Ag sulphides, was studied 30 years after it was abandoned. Fibre optic sensors were installed to record humidity, temperature, electrical conductivity and oxygen content in the pores down to a depth of 35.5 m. The oxygen profiles show an oxidised thickness of 5 m, meaning that the speed of the advancing oxidation front is estimated as 15 cm year−1. Sediment samples were obtained from different depths, and parameters such as pH, carbonates and metal(loid)s, among others, were analysed. High concentrations of As (> 500 mg kg−1), Fe (> 34,000 mg kg−1), Mn (> 900 mg kg−1), Pb (> 8000 mg kg−1) and Zn (> 5000 mg kg−1) were found. A piezometer was installed to enable the water inside the tailing pond to be sampled, and this presented high contents of SO42− (> 2400 mg L−1), Fe (> 28,000 μg L−1), Mn (> 7800 μg L−1) and Zn (> 7000 μg L−1), suggesting that the mineral leaching was related to the oscillations in the water table. The water from two drainage adits situated at the foot of the impoundment was also analysed, as well as surface water both upstream and downstream from it. The speciation-saturation models applied for these water samples indicated that in spite of the contamination potential of the impoundment, the deterioration in the quality of the river water is mainly due to the discharge from mining drains and the dissolution processes of precipitates accumulated along the riverbanks.

Groundwaters from shallow aquifers and surface water from rivers of the southern part of Poopo Lake basin within the Bolivian Altiplano have significant quality problems such as high salinity and high concentrations of arsenic (As). The extent of As contamination is observed in the studied groundwater over large parts of the study area. Surface-waters are generally alkaline (pH 8.2–8.7) and oxidizing with dissolved oxygen (DO) concentrations in a range of 2.5–6.6 mg/L The water chemistry is predominantly of Na–Cl–HCO 3 –type, with concentrations of dissolved As in the range of 8.6–117 µg/L with As(V) as the main aqueous species. The concentration of Li varies in the range of 1.1–4.4 mg/L, while other trace elements occur in low concentrations. Groundwaters have a very large range of chemical compositions and the spatial variability of As concentrations is considerable over distances of a few km; dissolved As in groundwater spans over 4 orders of magnitude (3–3497 µg/L), while concentrations of Li have a range of 0.05–31.6 mg/L. Among the investigated drinking-water wells, 90% exceed the WHO guideline value of 10 µg As/L. Electrical conductivity ranges between 295 and 20,900 µS/cm; high salinity is resulting from evaporation under ambient semi-arid climatic conditions. The pH values of the groundwaters are generally slightly alkaline (5.5–8.7) and universally oxidizing, under these conditions As(V) is the prevalent specie. Groundwater As correlates positively with pH, electrical conductivity, Cl − , Na + , HCO 3 − , Ca 2+ and SO 4 2 − . Weathering/dissolution of carbonates, evaporites, halite and plagioclase minerals incorporate Na + and HCO 3 − in solution with consequent pH and alkalinity increase; these are favorable conditions for high mobility of As species. Stable isotopic signatures indicate recharge at the Altiplano with seasonal effects. All surface water and some groundwater samples are enriched due to evaporation, which probably increased concentration of dissolved As.

Geochemical and geophysical techniques have been applied to investigate the potential environmental impact of the abandoned La Aquisgrana mine tailings, one of the most important sulfide-bearing tailings ponds of the Linares-La Carolina mining district (Spain). The geometry of the pile has been defined through geological field work and electrical resistivity imaging (ERI) surveys. The ERI profiles revealed the position of the bedrock surface below the tailings central area (more than 40 m in thickness) and helped in placing drill core sampling for geochemical analysis and a piezometer installation. In the 21 extracted samples, the total content of Pb, Zn, Cu, Fe, Mn, Sr, Rb and As were determined, with significant values being found for Pb and Zn (> 2000 mg kg − 1 ), Mn (> 700 mg kg − 1 ) and As (> 170 mg kg − 1 ). Although AMD has not been identified, water samples from the saturated zone of the tailings are characterized by elevated dissolved sulfate (2495 mg L − 1 ), Fe (20 mg L − 1 ), Mn (16 mg L − 1 ) and Zn (7 mg L − 1 ) contents, with an E.C. value of 3.3 mS cm − 1 and pH from 5.6 to 6.9, suggesting a process of metal mobilization. Physical and chemical data obtained from drill core and groundwater samples were combined with the electrical resistivity profile of the tailings to characterize areas with higher metal concentrations. A central low resistivity area (

Summary Many density-dependent groundwater flow simulations rely on a linear equation of state that relates the fluid density to the total dissolved solute content (TDS). This approach ignores non-linear volume of mixing effects, as well as the impact of any chemical reactions. These effects can be considered by using geochemical codes that implement algorithms that calculate the density of a fluid based on the concentration of individual solute species. While in principle such algorithms could be used in-lieu of a linear equation of state in a groundwater model, the computational overhead is such that the use of a more simplified equation of state is preferred. This requires that the assumption of linearity as well as the appropriate value of the linear slope have to be determined. Here, published density measurements of 7 chemically-distinct salt lake brines are compared with densities calculated by PHREEQC-3, confirming the applicability of PHREEQC’s algorithm to salt lake brines, as well as to seawater brines and artificial brines from laboratory experiments. Further, calculations with PHREEQC-3 are used to assess the impact of mineral precipitation reactions during evaporative concentration. Results show that the density–TDS relationship is essentially linear over a wide concentration range, and that slopes range between 0.64 and 0.75, with the upper end of the range applying to Na–CO 3 –Cl brines and the lower end to Na–Cl brines. Mineral precipitation of highly-soluble evaporate minerals such as halite and trona limit TDS, and may lead to considerable errors in coupled flow simulations based on a linear equation of state at high concentrations. Misrepresentation of the slope may lead to an error of up to 20% in the calculated length of the brine nose bordering a salt lake, or of the Rayleigh number, which indicates if a density stratification is stable or not.

In the southern part of the Cenozoic Duero Basin (Spain), naturally occurring arsenic and uranium in groundwater sometimes occur in concentrations exceeding the limits for potable water. Usually, concentrations of these elements are only slightly above the limit, but this is sufficient to invalidate its use as drinking water. Hydrogeotoxic risk or hydrogeotoxicity (HGT) is defined as the quotient between the observed concentration of an element and the limit set by health regulations (such as by the World Health Organization, WHO). Areas at risk of HGT from a given Potentially Toxic Geogenic Trace Element (PTGTE) are defined a quotient of > 1. Hydrogeotoxicity of arsenic and uranium (HGTAs and HGTU) were calculated for water samples and 34% returned HGTAs above 1. For uranium, different HGT indexes were considered against a variety of thresholds for drinking water established by different countries and organizations (10 μg/L, Germany; 15 μg/L, WHO, 2004; 30 μg/L, WHO, 2011/US-EPA, 2011): 48% samples returned HGTU10 > 1; 29% samples, HGTU15 > 1 and 7% had HGTU30 > 1. In the water samples analyzed, the highest arsenic content were usually associated with the highest uranium concentrations. However sometimes these two hydrogeotoxicities do not coincide and the HGTAs and HGTU10 distributions show different patterns. Hydrogeotoxicity due to more than one element (HGTAs and HGTU10) was also considered; 17% samples showed a potentially hydrogeotoxic risk linked to both PTGTEs, leading to the delimitation of these zones as especially vulnerable to a combined hydrogeotoxic hazard. The linear distribution of HGTAs seems to be related to the structure of the Cenozoic Duero Basin and to deep water inflows that are enriched in As and U, which are associated with its fissured basement. The HGTU can be partly linked to these deep flows with a significant hydrothermal component, but they are also linked to secondary processes occurring in the sedimentary basin, which could explain the scattered distribution of HGTU in some areas. As well as the HGT values, which are based on total concentrations, bioavailability of arsenic and uranium species was also considered in order to provide a comprehensive assessment of hydrogeotoxic risk over the study area. In all samples with HGTAs > 1, arsenic was present as As(V) inorganic form. Likewise, in samples with HGTU10 > 1, uranium appears as U(VI). This hydrogeotoxic anomaly must be related to both the chemical and radiological hazards., Unidad de Salamanca, Instituto Geológico y Minero de España, España, Unidad de Sevilla, Instituto Geológico y Minero de España, España

Although precise weighing lysimeters are mostly installed for agricultural purposes in crop-producing areas, these instruments are also useful in areas of ecological interest where soil and aquifer recharge-discharge processes need to be better understood. In September 2015 a high precision meteo-lysimeter was installed in a coastal dune of the Donana Natural Reserve to quantify the recharge in dune belts, and to estimate its dependence on regional climate trends. In addition to the lysimeter, also six soil moisture sensors (model CS650) and 2 meteorological stations were installed. The first results show recharge rates of natural precipitation ranging from 19 to 97%, depending on the meteorological conditions and the initial soil moisture. The lysimeter-measured rainfall generally exceeded the measurements of the tipping bucket. Also the contribution of the dew was detected by the lysimeter. A soil water model is currently being set up to simulate recharge, soil water movement, evaporation and percolation, as well as to quantify uncertainty and noise effects.

Oxygen measurements of soil air were carried out to determine daily variations and seasonality of oxygen in soil air and their dependence on ambient parameters such as groundwater chemistry, hydrodynamics and physico-chemical sediment characteristics. Two field sites in the Donana National Park were equipped with fibre-optic oxygen- and temperature sensors down to 6 m below the groundsurface, and oxygen was sampled from November 2010 until July 2012. One of the sites lies in the saltmarshes and the other in the dune belt, so providing coverage of contrasting hydrogeochemical conditions. Sediments from both locations were analyzed for physico-chemical parameters. Furthermore, groundwater levels were measured and samples taken for hydrochemical analysis. Soil gas in the salt marsh ranged from anaerobic conditions during the wet season to aerobic conditions in the dry period, which is related to the anaerobic groundwater and the high amount of electron donors in the sediment. The location in the dune belt yielded aerobic conditions throughout the year due to the minor amount of organic carbon in the sediments and the high oxygen content of the groundwater. The oxygen time series exhibits daily oscillations related to microbiological activity in the root zone of the Juniperus Sabina tree.

This study reports column tests and modelling results to assess the impact of hardpands and cemented layers on oxygen supply in mine waste sediments. The analysed sediment samples were obtained from a low-sulphide and low-carbonate polymetallic mine waste tailings impoundment located in the Freiberg mining district in Germany. The three samples were characterised by different degrees and types of cementation. After physical and mineralogical properties of the samples had been determined, breakthrough curves of oxygen were measured in column studies at different degrees of water saturation, and the diffusivities were assessed using a numerical modelling approach. Results demonstrate that cemented layers and hardpans in undisturbed sediments associated with fine-grained material operate as preferential pathways for diffusive gas transport during rewetting, leading to higher oxygen diffusivities compared to disturbed sediments. Under air-dry conditions, the disturbed samples show higher diffusivities than the undisturbed sample, indicating clogging of the porosity by precipitation of secondary minerals such as trivalent Fe oxyhydroxides acting as a barrier and thereby decreasing the diffusivity of the undisturbed sample. In contrast to sediments without cementation, diffusion experiments of sediments with cemented layers used in this study yield similar tortuosities in spite of their different grain size distributions, pointing to the important role of these heterogeneities for gas diffusion., Unidad de Sevilla, Instituto Geológico y Minero de España, España, Bundesanstalt für Geowissenschaften und Rohstoffe, Alemania, Fachbereich Geowissenschaften, Freie Universität Berlin, Alemania

This research aims to improve the current knowledge of groundwater salinisation processes in coastal aquifers using combined hydrochemical and isotopic parameters and inverse hydrochemical modelling. Field investigations were conducted in Laizhou Bay, which is the area most seriously affected by seawater intrusion in north China. During three sampling campaigns along a vertical transect in the ChangyiLiutuan area, 95 ground- and surface-water samples were collected for major ion and isotope analysis

Environmental isotope techniques, hydrogeochemical analysis and hydraulic data are employed to identify the main recharge areas of the Mt. Vulture hydrogeological basin, one of the most important aquifers of southern Italy. The groundwaters are derived from seepage of rainwater, flowing from the highest to the lowest elevations through the shallow volcanic weathered host-rock fracture zones. Samples of shallow and deep groundwater were collected at 48 locations with elevations ranging from 352 to 1,100m above sea level (a.s.l.), for stable isotope (δ18O, δD) and major ion analyses. A complete dataset of available hydraulic information has been integrated with measurements carried out in the present study. Inferred recharge elevations, estimated on the basis of the local vertical isotopic gradient of δ18O, range between 550 and 1,200m a.s.l. The isotope pattern of the Quaternary aquifer reflects the spatial separation of different recharge sources. Knowledge of the local hydrogeological setting was the starting point for a detailed hydrogeochemical and isotopic study to define the recharge and discharge patterns identifying the groundwater flow pathways of the Mt. Vulture basin. The integration of all the data allowed for the tracing of the groundwater flows of the Mt. Vulture basin. Se emplearon técnicas isotópicas ambientales, análisis hidrogeoquímicos y datos hidráulicos para identificar las principales áreas de recarga de la cuenca hidrogeológica del Mt. Vulture, uno de los más importantes acuíferos del sur de Italia. Las aguas subterráneas provienen de la infiltración del agua de lluvia, flujo desde las elevaciones más altas a las más bajas a través de zonas de fracturas someras de rocas reservorio volcánicas meteorizadas. Se recolectaron muestras de aguas subterráneas someras y profundas en 48 sitios con alturas en el intervalo que va de 352 a 1,100 m por sobre el nivel del mar (m s.n.m), para análisis de isótopos estables (δ18O, δD) e iones mayoritarios. Se integró una completa base de datos de la información hidráulica disponible con las mediciones llevadas a cabo en el estudio presente. Las alturas de recarga deducidas, estimadas sobre la base de gradiente isotópico vertical local de δ18O, oscilaron entre 550 y 1,200 m s.NM El patrón isotópico del acuífero Cuaternario refleja la separación espacial de diferentes fuentes de recarga. El conocimiento de la configuración hidrogeológica local fue el punto de partida para un estudio isotópico e hidrogeoquímico detallada para definir el esquema de la recarga y descarga identificando las trayectorias de flujo subterráneo de la cuenca del Mt. Vulture. La integración de todos los datos permitió el seguimiento de los flujos de las aguas subterráneas de la cuenca del Mt. Vulture., Department of Geological Sciences, University of Basilicata, Italia, Department of Chemistry, University of Basilicata, Italia, Unidad de Sevilla, Instituto Geológico y Minero de España, España, Institute of Geological Sciences, Freie Universität Berlin, Alemania, Unit Potsdam, Isotope Laboratory, Alfred Wegener Institute for Polar and Marine Research, Alemania, Department of Structural Engineering, Geotechnical Engineering, Engineering Geology, University of Basilicata, Italia

A finite element model was set-up to determine degradation rate constants for p-TSA during rapid sand filtration (RSF). Data used for the model originated from a column experiment carried out in the filter hall of a drinking water treatment plant in Berlin (Germany). Aerated abstracted groundwater was passed through a 1.6m long column-shaped experimental sand filter applying infiltration rates from 2 to 6mh(-1). Model results were fitted to measured profiles and breakthrough curves of p-TSA for different infiltration rates using both first-order reaction kinetics and Michaelis-Menten kinetics. Both approaches showed that degradation rates varied both in space and time. Higher degradation rates were observed in the upper part of the column, probably related to higher microbial activity in this zone. Measured and simulated breakthrough curves revealed an adaption phase with lower degradation rates after infiltration rates were changed, followed by an adapted phase with more elevated degradation rates. Irrespective of the mathematical approach and the infiltration rate, degradation rates were very high, probably owing to the fact that filter sands have been in operation for decades, receiving high p-TSA concentrations with the raw water.

This study reports the impact of hydrological conditions on salinisation and nitrate concentrations of a coastal aquifer located at the Mediterranean Sea, southern Spain. Eighty-two samples of ground- and surface water taken during two extreme hydrological events between 1994 and 1996 at 25 different wells were evaluated with regard to hydrochemistry, focusing on nitrate concentrations and salinisation, which constitute the main hazard of this aquifer. Furthermore, hydrochemical data were analysed by principal component analysis (PCA). Additionally, in 2007 13 ground- and surface water samples taken at 12 different locations were analysed for stable isotopes of D/18O, and one sample was analysed for 15N. Since 1993 until present saltwater intrusion was observed only during dry hydrological conditions in 1994; it showed an irregular salinisation pattern probably related to locally elevated hydraulic conductivities. Nitrate concentrations increase significantly during wet hydrologic conditions owing to uptake of nitrate by rising groundwater. Stable isotopes of groundwater reveal an Atlantic origin of the precipitation that recharges the aquifer and a minor amount of groundwater recharge by the water coming from the La Viñuela reservoir, which is used for irrigation over the aquifer. 15N isotopes point to a considerable input of nitrates derived from organic fertilisers., Institute of Geological Sciences, Freie Universitát Berlin, Alemania, Instituto del Agua, Universidad de Granada, España, Unidad de Murcia, Instituto Geológico y Minero de España, España, Departmento de Geología, Universidad de Málaga, España, Alfred Wegener Institute, Alemania

The objective of this study was to investigate the impact of flow, transport and geochemical parameters in the unsaturated and saturated zones on the release of SO4 from overburden lignite spoil piles into the adjacent lake. A vertical one-dimensional model was set up using the reactive transport simulator SULFIDOX in order to account for the unsaturated zone. The SULFIDOX model was calibrated for effective diffusion using measured O2 in the gas phase and SO4 concentrations in the liquid phase from the unsaturated zone of the heap. The results show high sensitivity to O2 supply and initially present gypsum, but the inclusion of secondary mineral precipitation in equilibrium is of minor importance for the results. To account for the transport of released SO4 from the saturated zone into the surface water, scenarios were performed by using SULFIDOX results as input concentration for a two-dimensional vertical model set up with PROCESSING MODFLOW and MT3D. These scenarios indicate a rising discharge of SO4 into the adjacent lake due to continued pyrite weathering for 80 a. Results are highly sensitive to dispersivity, whereas the spatial variability of pyrite distribution did not show any influence on the results. The consideration of initially present gypsum shows a major effect on the modelled SO4 release.

The microbial degradation of pharmaceuticals found in surface water used for artificial recharge is strongly dependent on redox conditions of the subsurface. Furthermore the durability of production wells may decrease considerably with the presence of oxygen and ferrous iron due to the precipitation of trivalent iron oxides and subsequent clogging. Field measurements are presented for oxygen at a bank filtration site in Berlin, Germany, along with simplified calculations of different oxygen pathways into the groundwater. For a two-dimensional vertical cross-section, oxygen input has been calculated for six scenarios related to different water management strategies. Calculations were carried out in order to assess the amount of oxygen input due to (1) the infiltration of oxic lake water, (2) air entrapment as a result of water table oscillations, (3) diffusive oxygen flux from soil air and (4) infiltrating rainwater. The results show that air entrapment and infiltrating lake water during winter constitute by far the most important mechanism of oxygen input. Oxygen input by percolating rainwater and by diffusive delivery of oxygen in the gas phase is negligible. The results exemplify the importance of well management as a determining factor for water oscillations and redox conditions during artificial recharge.

Summary This research reports the characterisation of ground- and surface-water interaction in the Fuente de Piedra Salt lake basin in southern Spain by a combined approach using hydraulic, hydrogeochemical and stable isotope data. During three sampling campaigns (February 2004, 2005 and October 2005) ground- and surface-water samples were collected for stable isotope studies ( 18 O, D) and for major and minor ion analysis. Hydraulic measurements at multilevel piezometers were carried out at four different locations around the lake edge. Conductivity logs were performed at four piezometers located along a profile at the northern lake border and at two deeper piezometers in the Miocene basin at a greater distance from the lake. To describe processes that control the brine evolution different hydrogeochemical simulations were performed. Hydrogeochemical data show a variety of brines related to thickness variations of lacustrine evaporites around the lake. Salinity profiles in combination with stable isotope and hydraulic data indicate the existence of convection cells and recycled brines. Furthermore restricted ground-water inflow into the lake was detected. Dedolomitisation processes were identified by hydrogeochemical simulations and different brine origins were reproduced by inverse modelling approaches.

This paper reports detailed O 2 measurements of pyrite bearing sediments in a column study and their interpretation based on a hydrogeochemical modelling approach. The research focuses on the quantitative effects of effective diffusion and microbiologic activity on pyrite weathering and acidification. A column experiment was set up and O 2 saturation and moisture contents were monitored over 100 days. The anoxic material used for the column experiment was taken from a sediment core of a mining waste dump in the southern periphery of the Lohsa storage system in the Lusatia region of Germany. The measured O 2 breakthrough curves were modelled using the simulator SAPY, a one-dimensional reactive transport code which considers the kinetics of chemical reactions and the delivery of O 2 into the sediment. The simulation yielded a strong dependence of pyrite oxidation on the moisture content which was quantified by an empirical equation. It was shown that the oxidation rate was catalysed by microbial activity exceeding the rate of diffusive O 2 delivery. In order to develop a management tool for predictive issues the results have already been applied to natural environments in another study using the adapted model.

A study has been performed to explore the origin, spatiotemporal behaviour and mobilisation mechanism of the elevated arsenic (As) concentrations found in ground water and drinking ponds of the Donana National Park, Southern Spain. At a larger scale, 13 piezometers and surface water samples of about 50 artificial drinking ponds and freshwater lagoons throughout the National Park were collected and analysed for major ions, metals and trace elements. At a smaller scale, 5 locations were equipped with piezometers and groundwater was sampled up to 4 times for ambient parameters, major ions, metals, trace elements and iron (Fe) speciation. As was analysed for inorganic and organic speciation. Undisturbed sediment samples were analysed for physical parameters, mineralogy, geochemistry as well as As species. Sediment analyses yielded total As between 0.1 and 18 mg/kg and are not correlated with As concentration in water. Results of the surface- and groundwater sampling revealed elevated concentration of As up to 302 μg/L within a restricted area of the National Park. Results of groundwater sampling reveals strong correlation of As with Fe(2+) pointing to As mobilisation due to reductive dissolution of hydroferric oxides (HFO) in areas of locally elevated amounts of organic matter within the sediments. High As concentrations in surface water ponds are correlated with elevated alkalinity and pH attributed to algae metabolism, leading to As desorption from HFO. The algae metabolism is responsible for the presence of methylated arsenic species in surface water, in contrast to ground water in which only inorganic As species was found. Temporal variations in surface water and groundwater are also related to changes in pH and alkalinity as a result of enhanced algae metabolism in surface water or related to changes in the redox level in the case of groundwater.

Summary This paper reports the hydrogeochemical modelling of reactions that take place during the uptake of weathering products by a rising watertable into a partly oxidized pyrite bearing sediment. The anoxic material used for the column, which is 2 m long, was taken from a core while drilling into a pyrite bearing sediment with an average pyrite content of 0.04 wt%. After packing the column it was drained and maintained in an unsaturated state over a period of 107 days to allow oxygen supply and pyrite weathering. During this period oxygen breakthrough curves were measured. After 108 days the column was flooded with distilled anoxic water from the bottom to the top with an average water table rise of 5 cm per day. The chemical composition of the pore water in the saturated zone as well as the water saturation and the oxygen contents have been monitored over the profile of the column. The compositions of the water samples at different depths of the column were modelled with PHREEQC, defining a one-dimensional reactive transport model regarding the mixing process between the incoming flooding water and the residual pore water of the drained period. Kinetic relations were implemented to account for source terms of acids and acid generating components released during the drained period. This study showed that the evolution of the rising water table can be characterized by almost immediate uptake of gypsum and by kinetically controlled dissolution of pyrite weathering products in combination with mixing processes and dispersion.

Numerical modeling approaches with varying complexity were explored to investigate coupled groundwater flow and geochemical processes in saline basins. Long‐term model simulations of a playa system gain insights into the complex feedback mechanisms between density‐driven flow and the spatiotemporal patterns of precipitating evaporites and evolving brines. Using a reactive multicomponent transport model approach, the simulations reproduced, for the first time in a numerical study, the evaporite precipitation sequences frequently observed in saline basins (“bull's eyes”). Playa‐specific flow, evapoconcentration, and chemical divides were found to be the primary controls for the location of evaporites formed, and the resulting brine chemistry. Comparative simulations with the computationally far less demanding surrogate single‐species transport models showed that these were still able to replicate the major flow patterns obtained by the more complex reactive transport simulations. However, the simulated degree of salinization was clearly lower than in reactive multicomponent transport simulations. For example, in the late stages of the simulations, when the brine becomes halite‐saturated, the nonreactive simulation overestimated the solute mass by almost 20%. The simulations highlight the importance of the consideration of reactive transport processes for understanding and quantifying geochemical patterns, concentrations of individual dissolved solutes, and evaporite evolution., Working group Hydrogeology and Landscape Hydrology, Carl von Ossietzky Universität, Alemania, Hydrogeology group, Freie Universität, Alemania, School of the Environment, Flinders University, Australia, National Centre for Groundwater Research and Training, Flinders University, Australia, Unidad de Sevilla, Instituto Geológico y Minero de España, España, CSIRO Land and Water, Australia, School of Earth and Environment, University of Western Australia, Australia

This article reports on a field modelling study to investigate the processes controlling the plume evolution of para-toluenesulfonamide (p-TSA) in anoxic groundwater in Berlin, Germany. The organic contaminant p-TSA originates from the industrial production process of plasticisers, pesticides, antiseptics and drugs and is of general environmental concern for urban water management. Previous laboratory studies revealed that p-TSA is degradable under oxic conditions, whereas it appears to behave conservatively in the absence of oxygen (O2). p-TSA is ubiquitous in the aquatic environment of Berlin and present in high concentrations (up to 38 μg L(-1)) in an anoxic aquifer downgradient of a former sewage farm, where groundwater is partly used for drinking water production. To obtain refined knowledge of p-TSA transport and degradation in an aquifer at field scale, measurements of p-TSA were carried out at 11 locations (at different depths) between 2005 and 2010. Comparison of chloride (Cl(-)) and p-TSA field data showed that p-TSA has been retarded in the same manner as Cl(-). To verify the transport behaviour under field conditions, a two-dimensional transport model was setup, applying the dual-domain mass transfer approach in the model sector corresponding to an area of high aquifer heterogeneity. The distribution of Cl(-) and p-TSA concentrations from the site was reproduced well, confirming that both compounds behave conservatively and are subjected to retardation due to back diffusion from water stagnant zones. Predictive simulations showed that without any remediation measures, the groundwater quality near the drinking water well galleries will be affected by high p-TSA loads for about a hundred years.

The groundwater downstream of a former sewage irrigation farm in Berlin is contaminated with ammonium (NH4+) and para-toluenesulfonamide (p-TSA), besides other anthropogenic pollutants. In the field, in situ removal of NH4+ by gaseous oxygen (O2) and air injection is currently being tested. A laboratory column experiment using aquifer material and groundwater from the site was performed to determine whether this remediation technology is also feasible to reduce high p-TSA concentrations in the anoxic groundwater. First, the column was operated under anoxic conditions. Later, compressed air was introduced into the system to simulate oxic conditions. Samples were collected from the column outlet before and after the addition of compressed air. The experiment revealed that whereas p-TSA was not removed under anoxic conditions, it was almost fully eliminated under oxic conditions. Results were modelled using a transient one-dimensional solute transport model. The degradation rate constants for p-TSA increased from 2.8E-06 to 7.5E-05 s–1 as a result of microbial adaption to the change of redox conditions. Results show that O2 injection into an anoxic aquifer is a successful strategy for p-TSA remediation, Institute of Geological Sciences, Freie Universität Berlin, Alemania, Department of Biology and Environmental Sciences, Carl von Ossietzky Universität Oldenburg, Alemania, Unidad de Sevilla, Instituto Geológico y Minero de España, España, DVGW-Technologiezentrum Wasser, Alemania, Department of Laboratories, Berliner Wasser Betriebe, Alemania

This article reports fibre-optic oxygen measurements on a reactive mine waste heap located in the polymetallic sulphide mine district of Freiberg in south-eastern Germany. The heaped material consists of sulphide-bearing tailings from a processing plant of a lead–zinc mine. Mine waste material was deposited in the water phase after separation of mining ores in a flotation process. The tailing impoundment is partly covered with coarse sand and topsoil. Oxygen profiles were monitored during one year at eleven locations showing different physical and mineralogical compositions. At each location a borehole was drilled where the optic sensors were installed at 2–5 different depths. After installation the oxygen profiles were monitored seven times during one year from 2006–2007 and three to five oxygen profiles at each location were obtained. Oxygen measurements were accompanied by physical, chemical and mineralogical data of the tailing material. Additionally, a detailed mineralogical profile was analysed at a location representative for the central part of the heap, where the cemented layers show lateral continuity. Results showed that cemented layers have a significant influence on natural attenuation of the toxic As and Pb species owing to their capacity of water retention. The measured oxygen profiles are controlled by the zone of active pyrite weathering as well as by the higher water content in the cemented layers which reduces gaseous atmospheric oxygen supply. In contrast, gypsum bearing hardpans detected at three other locations have no detectable influence on oxygen profiles. Furthermore, the grain size distribution was proved to have a major effect on oxygen diffusivity due to its control on the water saturation. Temporal changes of the oxygen profiles were only observed at locations with coarse sediment material indicating also an important advective part of gas flux, Unidad de Sevilla, Instituto Geológico y Minero de España, España, Bundesanstalt für Geowissenschaften und Rohstoffe, Alemania, Fachbereich Geowissenschaften, Freie Universität Berlin, Alemania

We characterize the precipitation and groundwater in a mountainous (peaks slightly above 3000 m a.s.l.), semi-arid river basin in SE Spain in terms of the isotopes 18O and 2H. This basin, with an extension of about 7000 km2, is an ideal site for such a study because fronts from the Atlantic and the Mediterranean converge here. Much of the land is farmed and irrigated both by groundwater and runoff water collected in reservoirs. A total of approximately 100 water samples from precipitation and 300 from groundwater have been analysed. To sample precipitation we set up a network of 39 stations at different altitudes (800–1700 m a.s.l.), with which we were able to collect the rain and snowfall from 29 separate events between July 2005 and April 2007 and take monthly samples during the periods of maximum recharge of the aquifers. To characterize the groundwater we set up a control network of 43 points (23 springs and 20 wells) to sample every 3 months the main aquifers and both the thermal and non-thermal groundwater. We also sampled two shallow-water sites (a reservoir and a river). The isotope composition of the precipitation forms a local meteoric water line (LMWL) characterized by the equation υD D 7Ð72υ18O C 9Ð90, with mean values for υ18O and υD of 10Ð28‰ and 69Ð33‰, respectively, and 12Ð9‰ for the d-excess value. To correlate the isotope composition of the rainfall water with groundwater we calculated the weighted local meteoric water line (WLMWL), characterized by the equation υD D 7Ð40υ18O C 7Ð24, which takes into account the quantity of water precipitated during each event. These values of (dυD/dυ18O), Instituto del Agua, Universidad de Granada, España, Oficina de Granada, Instituto Geológico y Minero de España, España, Institute of Geological Sciences, Freie Universit¨at Berlin, Alemania, Alfred Wegener Institute, Alemania

This article explores double-diffusive convective fluid motion in an aquifer above a salt dome. Aside from the ambient regional flow regime, the hydraulic conditions in an aquifer connected with a salt formation are determined by differences in salinity. Whereas density-driven flow patterns induced by the effect of salt have been studied before we focus on the additional effect of temperature. For the model setup, we select typical parameter values that are characteristic of not only the lowlands in Germany and Poland. For the computation of flow in a vertical cross-section, we use numerical modeling with COMSOL Multiphysics. The size and strength of eddies in the high salinity region above the aquifer base are strongly influenced by thermal effects. A sensitivity study shows a wide range of convection phenomena, ranging from the absence of convective motions via steady and oscillating circulation to unsteady fluctuating patterns. The flow and transport parameters show the highest sensitivity to the thermal Rayleigh number. peerReviewed

The objective of this study is to refine the understanding of recharge processes in watersheds representative for karstic semiarid areas by means of stable isotope analysis and hydrogeochemistry. The study focuses on the Granada aquifer system which is located in an intramontane basin bounded by high mountain ranges providing elevation differences of almost 2900 m. These altitude gradients lead to important temperature and precipitation gradients and provide excellent conditions for the application of stable isotopes of water whose composition depends mainly on temperature. Samples of rain, snow, surface water and groundwater were collected at 154 locations for stable isotope studies (δ18O, D) and, in the case of ground- and surface waters, also for major and minor ion analysis. Thirty-seven springs were sampled between 2 and 5 times from October 2004 to March 2005 along an altitudinal gradient from 552 masl in the Granada basin to 2156 masl in Sierra Nevada. Nine groundwater samples were taken from the discharge of operating wells in the Granada basin which are all located between 540 and 728 masl. The two main rivers were monitored every 2–3 weeks at three different altitudes. Rainfall being scarce during the sampling period, precipitation could only be sampled during four rainfall events. Calculated recharge altitudes of springs showed that source areas of mainly snowmelt recharge are generally located between 1600 and 2000 masl. The isotope compositions of spring water indicate water sources from the western Mediterranean as well as from the Atlantic without indicating a seasonal trend. The isotope pattern of the Quaternary aquifer reflects the spatial separation of different sources of recharge which occur mainly by bankfiltration of the main rivers. Isotopic signatures in the southeastern part of the aquifer indicate a considerable recharge contribution by subsurface flow discharged from the adjacent carbonate aquifer. No evaporation effects due to agricultural irrigation were detected.