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Riverbank filtration (RBF) consists in forcing surface water to infiltrate and flow through an aquifer by means of a pumping well located near a surface water body. RBF aims to take advantage of the filtration capacity of aquifers to improve the water quality by removing a wide range of pollutants, including contaminants of emerging concern, by combining of physical, chemical and biological processes. However, the efficacy of RBF for eliminating substances that are considered persistent, mobile, and toxic (PMT), or very persistent and very mobile (vPvM), is expected to be low due to the high mobility of these substances. PMT and vPvM compounds, which are accumulated in the water cycle, are harmful to humans and the environment. For this reason, the processes affecting PMT and vPvM substances during RBF processes deserve to be deeply investigated.This study aims at investigating the processes affecting PMT and vPvM substances in a site that behaves similarly to a RBF system. The study site is located in Sant Adriá del Besòs (Barcelona, Spain), where a constant pumping to drain an underground parking lot forces the water from the Besòs river to infiltrate and travel up to 230 m through the aquifer. Groundwater samples were collected from the river, and a set of piezometers aligned along the groundwater flow line between the Besòs river, and the underground parking lot allowed monitoring of the water at different stages after its infiltration. The samples were analysed by liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS) and PMT and vPvM were determined by a suspected screening approach.This investigation provides new insights into the processes affecting PMT and vPvM substances and will have tremendous implications for determining groundwater quality in managed aquifer recharge contexts.

Water shortage is expected to exacerbate because of the increase pressure on water resources due to climate change and the growing population. It is deemed necessary to take advantage of all the available freshwater resources to cover the growing demand, especially in urban areas. However, urban aquifers are commonly contaminated by a wide range of organic contaminants of emerging concern (OCECs). OCECs, which comprise natural and synthetic compounds, are potentially hazardous to the environment and human health. Therefore, the processes controlling the behaviour of OCECs must be investigated to determine when and how the urban resources can be used safely and to design remediation strategies against them. The removal rate of OCECs depends on the temperature and redox conditions of groundwater that may be affected by anthropogenic activities like the exploitation of the geothermal potential of aquifers. The behaviour of some OCECs has been investigated in the context of managed aquifer recharge (MAR). However, the water range in MAR is lower than that expected around geothermal exploitations, and the behaviour of OCECs under similar conditions to that found around geothermal facilities should be evaluated. We have investigated the removal of 12 OCECs reported in the aquifers of Barcelona (Spain) by using batch experiments under different redox conditions and temperatures (25°C and 35°C). The results show that the removal rate of OCECs depends on the temperature, suggesting that the impact of geothermal exploitations must be considered when investigating the fate and evolution of OCECs in urban aquifers. Unexpectedly, it was observed that the removal rate could also decrease with the temperature, which may be related to the proliferation of different communities of bacteria depending on the temperature. Overall, this investigation supports the idea that it is possible to design geothermal facilities to promote the removal of OCECs.

Groundwater is the main source of freshwater in the European Union, yet freshwaters are polluted by organic contaminants if contaminants are not efficiently removed in wastewater treatment plants. Here we review the occurrence, fate, and risk assessment of organic contaminants included in the surface water watch list of the European groundwater bodies. This list includes 15 compounds: the hormones estrone, 17˗β˗estradiol and 17˗α˗ethinylestradiol; the pesticides methiocarb, metaflumizone, imidacloprid, thiacloprid, thiamethoxam, clothianidin and acetamiprid; and the antibiotics amoxicillin, ciprofloxacin, azithromycin, clarithromycin and erythromycin. We found that while contaminants commonly occur at low levels of few nanograms per L or are not detected in natural waters, there is an increasing number of reports displaying concentrations above 100 ng/L. Surface waters are commonly more contaminated than groundwater, suggesting that contaminants are removed in groundwater aquifers, e.g. by sorption or biodegradation. The estimated risk following water drinking by humans is higher for infants than for adults. Nonetheless, on the average, groundwater consumption does not pose a risk for human health at the reported groundwater concentrations. Risk assessment using fish, plants, algae, and invertebrates shows that only few species are impacted by contaminants, e.g. Americamysis bahia, Mysidopsis bahia, and Daphnia magna by pesticides; and the plant Lemna minor and the algae Microcystis aeruginosa by the antibiotics ciprofloxacin and erythromycin., This research has been supported through the Grant CEX2018-000794-S funded by MCIN/AEI/https://doi.org/10.13039/501100011033. Anna Jurado thanks the Ministry of Science, Innovation and Universities for funding the project INTEGRATE (Ref: PID2019-107945RJ-I00) under the 2019 call of the "Proyectos de I+D Retos Investigación”. Estanislao Pujades gratefully acknowledges the support received through the grant RYC2020-029225-I funded by MCIN/AEI/https://doi.org/10.13039/501100011033 and by “ESF Investing in your future”, and the Award for Scientific Research into Urban Challenges in the City of Barcelona 2020 (20S08708) from the Barcelona city council. M. Silvia Díaz˗Cruz acknowledges the Generalitat de Catalunya (Water and Soil Quality Unit 2017-SGR-1404) and the EU (LIFE20 ENV/ES/000284—LIFE REMAR project).

Most underground constructions, which are needed to improve mobility and increase available space in urban areas, require excavations that are usually deeper than the water table (e.g., for the construction of stations or underground parking lots). A frequently used technique to develop excavations under these conditions consists in combining the cut-and-cover method with a dewatering system based on deep pumping wells. Retaining walls used for the cut-and-cover method allow excavating between vertical walls and minimizes the inflow of groundwater, while deep pumping wells provide dry and stable conditions. Despite this technique is widely used, some aspects related with the presence of groundwater must be considered to avoid accidents. Dewatering systems must be properly designed to guarantee suitable conditions and to minimize the pumping settlements outside of the working area. In addition, it is required to assess the presence of defects in the retaining walls because the flow of groundwater through them may entail negative consequences. This chapter explains procedures (i) to design efficient dewatering systems considering the working conditions, the stability and the impacts generated in the vicinity of the construction, and (ii) to evaluate the state of the retaining walls by using hydrogeological tools.

Groundwater is a vital resource for the development of urban areas, where the problem focuses on the quantity and on the quality of this freshwater resource. Barcelona is a good example as because currently groundwater is used for irrigation of parks and gardens and street cleaning due to its poor quality as drinking water source. Among the pollutants found in groundwater, of special interest are contaminants of emerging concern (CEC), as they pose a high risk to the aquatic environment and human health. The behaviour, spatial distribution and processes that control them in the aquatic environment are still uncertain and most of them are unregulated. In this paper we study the inputs and processes controlling the hydrochemistry of Barcelona urban groundwater with special emphasis on the CEC. We selected 29 CEC that were detected at high concentrations of up to 1 μg L-1 (e.g. gemfibrozil, benzotriazole, among others). Towards the higher zones we identify groundwater with relative low mineralization more proximate to the natural recharge composition, while towards the urban area the anthropic inputs are evident (e.g. nitrate concentrations range from 50 to 200 mg L-1). Near the Besos river there is a clear contribution from this superficial water highly polluted, mostly from wastewater treatment plant (WWTP) discharges, and reducing conditions. The main contributor of CEC pollution in groundwater was the river-aquifer interaction (Besos river), while towards the urban area it might come from sewage seepage and probably a minor input from urban runoff. The redox state of these waters seems to control the fate and occurrence of several of these CEC. The limitations of this study are restricted to a single sampling campaign, therefore these results should be corroborated with other sampling campaigns, including the seasonal variations, which would allow establishing more robust conclusions., This research has been supported by the European Commission, the Spanish Foundation for Science and Technology (FECYT) and Spanish State Research Agency (AEI) through a collaborative international consortium (URBANWAT project), and the Ministry of Science through the UNBIASED project (Ref: RTI2018-097346-B-I00). We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).

Urban aquifers are a valuable resource of freshwater for cities, however, their quality is degraded due to the presence of organic contaminants of emerging concern (CECs). The effects of organic CECs are largely unknown, but there is evidence that they pose a risk for human health, soil, plants and animals. Organic CECs are naturally degraded in aquifers and their degradation rates depend on the physico-chemical properties, i.e., redox conditions and groundwater temperature. Some anthropogenic activities, like low-enthalpy geothermal energy (LEGE), may modify subsurface physico-chemical conditions altering the behaviour of organic CECs. LEGE is a renewable and carbon-free energy that allows obtaining cooling and heating energy. The utilization of LEGE is currently growing and it is expected that in a near future the density of LEGE systems will increase. LEGE modifies the groundwater temperature and in some situations the redox state (i.e., if the dissolved oxygen increases when groundwater is returned to the aquifer as a result of a poorly design), thus, it is of paramount importance to determine the impact of LEGE related activities on the behaviour of organic CECs. The behaviour of organic CECs under the influence of LEGE is investigated by means of thermo-hydro-chemical numerical modelling. Simulation output shows that LEGE activities have the potential to modify the degradation rates of organic CECs, and thus, their concentrations in aquifers. In the simulated scenario, the concentration of the chosen CEC decreases by the 77 % at the downgradient boundary of the model. The results of this study have significant implications for predicting the behaviour of organic CECs in urban aquifers and suggest specific changes in the design of LEGE facilities aiming to improve the quality of urban groundwater by boosting in-situ attenuation mechanisms., This research has been supported by the Barcelona city council through the Award for Scientific Research into Urban Challenges in the City of Barcelona 2020 (20S08708) and by the grants PID2021-128995OA-I00 funded by MCIN/AEI/10.13039/501100011033T and FEDER “one way to make Europe”, CEX2018-000794-S funded by MCIN/AEI/10.13039/501100011033 and RYC2020-029225-I funded by MCIN/AEI/10.13039/501100011033 and “ESF Investing in your future”.​​​​​​​ We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).

Due to the fast urbanization and climate change, urban aquifers are considered as a strategic source of potable water. However, a potential limitation is the presence of contaminants, such as pharmaceuticals, which might deteriorate groundwater quality. This work investigated the occurrence of pharmaceuticals and evaluated their human health risk in an alluvial urban aquifer recharged by a polluted river that receives discharges from wastewater treatment plants (WWTPs). To this end, river and groundwater samples were collected from February to May 2021 for the analysis of 92 pharmaceuticals using a solid-phase extraction and a highpressure liquid chromatography coupled to a high resolution mass spectrometric methodology (HPLC-HRMS). Results showed that 35 pharmaceuticals, including 6 transformation products (TPs), were detected in all groundwater samples and the range of concentrations was from the low ng L-1 to 44.5 μg L-1. Moreover, the concentrations of some substances decreased along the flow path during bank filtration, suggesting the occurrence of natural attenuation processes (e.g., adsorption or oxidation-reduction). Finally, most of the measured substances did not pose a risk to human health since estimated risk quotients were low., This research has been supported by the Ministerio de Ciencia e Innovación (grant no. CEX2018-000794-S). We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).

A simple data-based advection-reaction (reactive transport) model applicable to both rivers and aquifers monitoring networks is proposed. It is built on (a) available monitoring data, and (b) graph-theoretical concepts, specifically making use of the Laplacian matrix to capture the network topology and the advection process. The method yields useful information regarding the dynamic spatial behavior of the variables monitored, expressed in terms of quantitative parameters like characteristic length, entropy, first-order decay constants, synchronization between sites, and the external inputs/outputs to the system. The model was tested in an unconfined shallow aquifer located in the lower Besòs River (Spain), in which 37 pharmaceutical compounds were monitored at 7 sites, alongside two campaigns (February and May 2021). Characteristic lengths were, on average, of the same order (24.5 m) as the mean distance between consecutive monitoring sites (33.6 m), thus reflecting an adequate monitoring network design. From an estimated mean advection velocity (0.24 m·h-1), first-order decay constants were calculated for each compound and campaign, with mean values of 0.025 h-1 (February) and 0.005 h-1 (May). Whereas entropy was generally slightly larger values in February than in May (mean values of 1.02 and 0.9 entropy units respectively), synchronization showed the opposite trend (mean values of 62.4% and 68.8% respectively). The input/output profiles were generally site-dependent, regardless of the compound, and campaign considered. • A new advection-reaction modeling approach directly based on experimental data obtained from monitoring campaigns together with the network topology is proposed. • The method yields new quantitative information regarding the dynamic behavior of the variables monitored, useful for both research and management purposes., This research has been supported through the grant CEX2018-000794-S funded by MCIN/AEI/ 10.13039/501100011033.

This study aimed to determine the effect of land-use changes on the non-carcinogenic health risk of nitrate ion exposure of underground drinking water resources in Shiraz (Iran). To this end, 175 chemical samples for the nitrate analysis were regularly taken from 35 drinking water wells of Shiraz from 2013 to 2017, and their results were zoned using GIS. Hazard quotient (HQ) induced by nitrate ion exposure was determined in four age groups: infants, children, adolescents, and adults. Area changes of four types of land-use, including residential, agricultural and green space, industrial, and bare land within a radius of 400 m of drinking water wells, were determined using the GIS and Google Earth software. Then, all data was imported to Matlab 2018 for statistical analysis. The results showed that mean nitrate concentration increased by 2.5 mg L-1 from 2013 to 2017. According to the zoning map, 5 and 11.4% of the area in 2013 and 2017, respectively, exceeded the drinking water standard set by nitrate (i.e., 50 mg/L). Air temperature and precipitation variations also influenced nitrate concentrations and HQ changes (Rtemperature = 0.67). Children's age group was the most vulnerable, and during the study period, this vulnerability was an increasing trend, so that the HQ from 0.93 in 2013 to 0.97 in 2017 has increased. The rate of land-use changes in agricultural, industrial, bare, and urban was -1.8%, 1.3%, -4.6%, and 2.1%, respectively, and the highest correlation was observed between HQ and Diff.l residential land use (Rinfant = 0.55). According to the results, the most influential factor in HQ was air temperature (R = 0.66), and urban land-use change (R > 0.44). To sum up, this study's results showed that land-use changes, especially urban and residential development, significantly affect groundwater nitrate concentration and its degree of HQ. Moreover, increasing temperature and decreasing annual precipitation can also increase the severity of this risk., The results presented in this study are from the performed research projects at Behbahan Faculty of Medical Sciences (Research Intercept Code: 98067). Availability of data and materials All data generated or analyzed during this study are included in this published article.

The expected growth of urban areas requires the construction of underground infrastructures, especially for improving transportation and mobility. These new infrastructures are commonly constructed below the water table because they must be deeper than previous underground structures. In addition, many urban areas are located near surface water bodies (i.e., seas, rivers and/or lakes) that induce a shallow water table. The “cut and cover” method combined with dewatering wells is a frequently used procedure under these conditions for the construction of underground infrastructures. The main concerns of this procedure are related to the stability of the excavation bottom, the behavior of the retaining walls and/or the impacts induced by the dewatering actions. These issues must be evaluated, and new solutions must be proposed to improve its weak points. This paper compiles the main publications focused on the construction of underground infrastructures below the water table and in urban areas by using the cut and cover method combined with pumping. This review reveals that, despite many published studies, more research is needed to address some relevant issues such as: (1) the mitigation of dewatering impacts by using artificial recharge, (2) the adaptation of methods for characterizing retaining walls to be used under heterogeneous conditions, (3) the improvement of the prediction of surface settlements produced by pumping, and (4) the consideration of non-Darcy flows in the design of dewatering systems.

Trabajo presentado en la EGU General Assembly 2022 , celebrada en Viena (Austria), del 22 al 27 de mayo de 2022., Pressure over water resources is increasing rapidly as a result of climate change and growing population. In this context, urban aquifers emerge as a valuable resource of fresh-water for cities. However, the quality of urban groundwater is degraded due to the presence of contaminants of emerging concern (CECs) that reach continuously urban aquifers from different recharge sources. The effects of CECs are largely unknown, but it is expected that they pose a risk for human health, soil, plants and animals. CECs are naturally degraded in aquifers and their degradation rates depend on the physico-chemical conditions (i.e., redox conditions and water temperature) of the groundwater, which may vary as a result of anthropogenic activities. Therefore, it is needed to establish the impact of anthropogenic activities on CECs to determine their behaviour under modified and variable physico-chemical conditions and allow the safely use of urban groundwater. One of these anthropogenic activities that potentially modify the physico-chemical conditions is the use of the subsurface to obtain cooling and heating energy through low-enthalpy geothermal energy (LEGE) systems. LEGE is a renewable and carbon-free energy whose utilization is currently growing. Thus, it is expected that in a near future the density of LEGE systems will increase over most cities. Then, our objective is to determine the impact of LEGE systems on the behaviour of CECs. We have investigated the behaviour of CECs under the influence of LEGE by means of numerical models and considering different representative scenarios. The results show that the physico-chemical variations induced by LEGE systems modify notably the degradation rates of CECs, and thus, their concentrations on the downgradient side. Our results have significant implications for predicting the behaviour of CECs in urban aquifers and suggest the possibility of specifically design LEGE systems to improve in a passive way the quality of urban groundwater by eliminating CECs.

Sustaining healthy living conditions in urban areas is a tremendous challenge in the European Union, and central to this mission is the supplying of freshwater resources. However, rapid urban growth and climate change will negatively impact water resources. Therefore, water shortage is encouraging research into potential alternative freshwater resources such as urban groundwater. Sometimes, urban groundwater is pumped to prevent damage to underground structures. This is the case of the underground parking lot of Sant Adrià del Besòs (Barcelona, NE Spain), where large amounts of urban groundwater are pumped to avoid seepage problems, which are directly poured to the sewage system. This consideration ponders if this urban groundwater might be used as safe drinking-water because urban aquifers contain a vast array of pollutants such as pharmaceuticals.This work investigated the occurrence and fate of more than 100 pharmaceuticals in the shallow aquifer of the Besòs Delta River, which main contamination source is a polluted river that receives discharges from wastewater treatment plants. To this end, river and groundwater samples were collected from February to May 2021 for the analysis of pharmaceuticals using a solid-phase extraction and high pressure liquid chromatography coupled to high resolution mass spectrometric methodology (HPLC-HRMS). Preliminary results showed that, in more than 70% of the samples, several pharmaceuticals such as anticonvulsants, antihypertensives, antibiotics, and antivirals were detected. More precisely, 38 substances were detected in all river samples and 15 were ubiquitous in groundwater samples. The range of concentrations for all the compounds was between 2 ng/L and up to 880 ng/L. Moreover, the behavior of the compounds along the bank filtration until reach the pumping site, close to the parking lot, suggested that the natural attenuation of the pharmaceuticals likely to adsorption or oxidation-reduction processes occurred, as groundwater sampling points located close to the river presented the highest concentrations for the detected substances. This observation allows inferring that the pumped urban groundwater could be used for different purposes including drinking water but further studies are required to quantify the coupled processes that control their fate in urban aquifers.

This research presents the occurrence and fate of 121 contaminants of emerging concern (CECs) in an urban aquifer polluted by river recharge through a data-base modelling. Afterwards, risk quotients (RQs) are computed to determine the risk posed by CECs to human health. To this end, groundwater and river water samples were collected in four campaigns conducted from February to May 2021. Results show that 46 CECs are ubiquitous in groundwater and their concentrations vary several orders of magnitude, ranging from below the limit of quantification to 44.5·103 ng/L for iopamidol. Transformation products (TPs) are usually detected at lower concentrations than those of the parent substances but there are some exceptions (i.e., fipronil sulphide, fipronil sulfone and O-desmethylvenlafaxine). River concentrations are higher than those detected in groundwater for some CECs, indicating the occurrence of natural attenuation processes when river water infiltrates the aquifer. A data-based advection-reaction modelling is proposed and tested for ca. 40 substances with detection frequencies higher than 90%. It provides useful quantitative information regarding the dynamic behaviour of the variables monitored, expressed in terms of characteristic length, entropy and synchronized state contribution. Finally, risk quotients (RQs) are used to assess the human health risk posed by the ubiquitous CECs in groundwater. Most CECs do not pose any risk to the different life stages considered, as the RQs evaluated are lower than 0.01. However, the pharmaceuticals valsartan and its TP valsartan acid show RQs higher than 1, indicating that these substances might be harmful to human beings., This research has been supported through the grant CEX2018-000794-S funded by MCIN/AEI/10.13039/501100011033 and the UrbanWat project (JPI-JC-2018_16) from the “Agencia Estatal de Investigación” from the Spanish Ministry of Science and Innovation.

Aquifers under agricultural areas are considered to be an indirect source of nitrous oxide emission (N2O) to the atmosphere, which is the greenhouse gas (GHGs) characterized with the highest global warning potential and acts as a stratospheric ozone depletion agent. Previous investigations performed in the Cretaceous Hesbaye chalk aquifer in Eastern Belgium suggested that the dynamics of N2O in the aquifer is controlled by overlapping biochemical processes such as nitrification and denitrification. The current study aims to obtain better insight concerning the factors controlling the distribution of N2O concentration along a vertical dimension in the aquifer, and to capture and quantify the occurrence of nitrification and denitrification processes in the groundwater system. Low-flow groundwater sampling technique was undertaken at different depths in the aquifer to collect groundwater samples aiming at obtaining information about ambient aquifer hydrogeochemical conditions and their effect on the accumulation of GHGs. Afterwards, laboratory stable isotope experiments, using NO3- and NH4+ compounds labeled with heavy 15N isotope, were applied to quantify the rates of nitrification and denitrification processes. Ambient studies suggest that the occurrence of N transformation was related to denitrification while laboratory incubation experiments did not detect it. Such controversial results might be explained by the discrepancy between real aquifer conditions and lab design studies. Thus, additional in situ tracer experiments should be carried out in areas where natural groundwater fluxes do not flush the injected tracer too rapidly. In addition, it would be useful to conduct microbiological studies to obtain better insight into the nature of subsurface biofilm biotope., This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 675120. Los Gatos Research OA-ICOS was funded by the Fonds National de la Rechecherche Scientifique (FNRS) (22547486). AVB is a Research Director at the FNRS.

Underground pumped hydropower storage (UPHS) using abandoned mines is an alternative to store and produce electricity in flat regions. Excess of electricity is stored in form of potential energy by pumping mine water to a surface reservoir. When the demand of electricity increases, water is discharged into the mine (i.e., underground reservoir) through turbines producing electricity. During the complete operational process of UPHS plants, hydrochemical characteristics of water evolve continuously to be in equilibrium successively with the atmosphere (in the surface reservoir) and the surrounding porous medium (in the underground reservoir). It may lead to precipitation and/or dissolution of minerals and their associated consequences, such as pH variations. Induced hydrochemical changes may have an impact on the environment and/or the efficiency (e.g., corrosions and incrustations affect facilities) of UPHS plants. The nature of the hydrochemical changes is controlled by the specific chemical characteristics of the surrounding porous medium. However, the magnitude of the changes also depends on other variables, such as hydraulic parameters. The role of these parameters is established to define screening criteria and improve the selection procedure of abandoned mines for constructing UPHS plants. This work evaluates the role of the main hydrogeological factors for three different chemical composition of the porous medium. Results are obtained by means of numerical reactive transport modeling. Potential impacts on the environment (mainly on groundwater and surface water bodies) and on the efficiency of the UPHS plants vary considerably from a hydraulic parameter to another showing the need for a detailed characterization before choosing locations of future UPHS plants.

Groundwater is the main source of water supply in the European Union and therefore, the conservation and protection of this freshwater resource against pollution are key issues. Organic micropollutants have raised concern as wastewater treatment plants partly remove them and thus, they continuously enter the aquifers, threatening groundwater quality.

Pharmaceuticals, such as non-steroidal anti-inflammatory drugs (NSAIDs) and their metabolites, have become a major concern due to their increasing consumption and their widespread occurrence in the environment. In this paper, we investigate the occurrence of NSAIDs and their metabolites in an urban aquifer, which may serve as a potential resource for drinking water, and propose a methodology to assess the removal of these substances in the river–groundwater interface. Then, risk quotients (RQs) are computed, in order to determine the risk posed by the single NSAIDs and their mixture to human health. To this end, six NSAIDs and two metabolites were collected from an urban aquifer located in the metropolitan area of Barcelona (NE, Spain), in which the major pollution source is a contaminated river. All of the target NSAIDs were detected in groundwater samples, where the concentrations in the aquifer were higher than those found in the river water (except for ibuprofen). Diclofenac, ketoprofen, propyphenazone and salicylic acid were detected at high mean concentrations (ranging from 91.8 ng/L to 225.2 ng/L) in the aquifer. In contrast, phenazone and mefenamic acid were found at low mean concentrations (i.e., lower than 25 ng/L) in the aquifer. According to the proposed approach, the mixing of river water recharge into the aquifer seemed to some extent to promote the removal of the NSAIDs under the sub-oxic to denitrifying conditions found in the groundwater. The NSAIDs that presented higher mean removal values were 4OH diclofenac (0.8), ibuprofen (0.78), salicylic acid (0.35) and diclofenac (0.28), which are likely to be naturally attenuated under the aforementioned redox conditions. Concerning human health risk assessment, the NSAIDs detected in groundwater and their mixture do not pose any risk for all age intervals considered, as the associated RQs were all less than 0.05. Nevertheless, this value must be taken with caution, as many pharmaceuticals might occur simultaneously in the groundwater., IDAEA-CSIC is a Centre of Excellence Severo Ochoa (Spanish Ministry of Science and Innovation, Project CEX2018-000794-S). A. J gratefully acknowledges the support from the Secretary for Universities and Research of the Ministry of Economy and Knowledge of the Government of Catalonia and the Marie Sklodowska-Curie COFUND of the programme H2020 (BP3, contract number 801370). The authors would like to thank the European Commission, the Spanish Foundation for Science & Technology (FECYT) and State Research Agency (AEI)) for funding in the frame of the collaborative international consortium (URBANWAT) financed under the 2018 Joint call of the WaterWorks2017 ERA-NET Cofund. This ERA-NET is an integral part of the activities developed by the Water JPI. Additionally, authors would also thank the Ministry of Science, Innovation and Universities, for funding the projects UNBIASED (Ref: RTI2018-097346-B-I00) under the 2018 call of the “Proyectos de I+D Retos Investigación” and INTEGRATE (Ref: PID2019-107945RJ-I00) under the 2019 call of the “Proyectos de I+D Retos Investigación”.

An extensive survey of groundwater quality was performed at the regional scale in peri-urban and industrial contexts of the Walloon Region (Belgium). To this end, 243 sampling locations from 8 areas located in different geological contexts and different peri-urban areas of the region were sampled outside pollution hotspots related to contaminated sites. Each groundwater sample was analyzed for 19 inorganic trace elements, 59 organic micro-pollutants and 8 major and minor elements. Five physico-chemical parameters were measured in the field, at the time of sampling to determine the environmental conditions prevailing in groundwater. Existing groundwater chemical data available outside such peri-urban and industrial areas were also compiled from existing groundwater quality databases for comparison. Most of the organic and inorganic pollutants are detected and their levels of occurrence are described statistically. Cumulative distribution function plots allow comparing the distributions of inorganic trace elements in and outside the urbanized and industrialized areas and among the different prevailing geological contexts. Two indicators are introduced, one quantifying the impact on inorganic trace elements of diffuse pollution in urban and industrial areas, the other reflecting the influence of lithology on concentrations in groundwater. Results show that the composition of groundwater is altered in peri-urban and industrial areas with increased concentrations for several organic pollutants and for most inorganic trace elements. However, the results clearly indicate that for the inorganic trace elements, anthropogenic influence is not limited to increased discharge of pollutants in the urban and industrial areas but also to significant changes in environmental conditions, with more reducing and acidic conditions observed in groundwater. The influence of lithology is also marked in the data set. From a more pragmatic point of view, the data set has been also used to derive upper limits of pollutant background concentrations to be used in decision-making related to the management of contaminated groundwater in urban and industrial environments in the Walloon Region., This study is a contribution to the project POLLUSOL2. This project was supported by SPAQuE (Belgium) including news piezometers and new samples and analyses. We also thank the Service Public de Wallonie - DGO3 Département de l'Eau et l'Environnement – Direction des Eaux Souterraines for the databases provided.

Underground constructions in urban environments are more and more frequent, and usually, they are undertaken below the water table. The interaction between groundwater and underground constructions is a relevant topic that has to be carefully considered because unforeseen incidents may appear during these constructions. This paper shows the methodology used to design the dewatering system of a large excavation below the water table in a high populated urban area. The excavation was required for the construction of the assembly shaft of the tunnel boring machine that was used to excavate the high speed train tunnel below Barcelona (Spain). This methodology was useful to design an efficient dewatering systems that allowed constructing the assembly shaft in safe conditions and without producing appreciable impacts around the construction site. The most important step of the proposed method was the hydrogeological characterization of the soil because this allowed building a realistic and representative numerical model. This work shows the importance of interdisciplinary approach because the dewatering system was designed combining field work, classical analytical solutions and numerical methods.

This study investigates the occurrence of greenhouse gases (GHGs) and the role of groundwater as an indirect pathway of GHG emissions into surface waters in a gaining stretch of the Triffoy River agricultural catchment (Belgium). To this end, nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) concentrations, the stable isotopes of nitrate, and major ions were monitored in river and groundwater over 8 months. Results indicated that groundwater was strongly oversaturated in N2O and CO2 with respect to atmospheric equilibrium (50.1 vs. 0.55 μg L−1 for N2O and 14,569 vs. 400 ppm for CO2), but only marginally for CH4 (0.45 vs. 0.056 μg L−1), suggesting that groundwater can be a source of these GHGs to the atmosphere. Nitrification seemed to be the main process for the accumulation of N2O in groundwater. Oxic conditions prevailing in the aquifer were not prone for the accumulation of CH4. In fact, the emissions of CH4 from the river were one to two orders of magnitude higher than the inputs from groundwater, meaning that CH4 emissions from the river were due to CH4 in-situ production in riverbed or riparian zone sediments. For CO2 and N2O, average emissions from groundwater were 1.5 × 105 kg CO2 ha−1 year−1 and 207 kg N2O ha−1 year−1, respectively. Groundwater is probably an important source of N2O and CO2 in gaining streams but when the measures are scaled at catchment scale, these fluxes are probably relatively modest. Nevertheless, their quantification would better constrain nitrogen and carbon budgets in natural systems.

Underground pumped storage hydropower (UPSH) using abandoned mines is an alternative system to manage electricity production in flat regions. Water from an underground reservoir is pumped to a surface reservoir to store electricity in the form of potential energy. Later, water is discharged through turbines into the underground reservoir to produce electricity when demand increases. During this operation, the water hydrochemistry continuously evolves. It varies in order to reach chemical equilibrium with the atmosphere (in the surface reservoir) and with the surrounding porous medium and groundwater (in the underground reservoir). The hydrochemical variations may lead to reactions in the reservoirs and in the surrounding porous medium, causing potentially negative consequences for the environment and the system efficiency, especially when pyrite is present in the surrounding porous medium. In this case, pyrite oxidation leads to a decrease in pH and the precipitation of goethite or schwertmannite in the surface reservoir. The decrease in pH is mitigated when calcite is present in the porous medium. However, other concerns may arise, such as slight increases in pH, the precipitation of ferrihydrite and calcite in the surface reservoir, and the oxidation of pyrite and dissolution of calcite in the surrounding porous medium. Understanding the pH variations and the precipitation/dissolution of minerals is of paramount importance in terms of the environmental impacts and system efficiency. For this reason, this work investigates the main hydrochemical changes and their associated consequences when abandoned deep mines are used for UPSH by means of numerical modelling. The main objective is to highlight the importance of considering hydrochemical aspects when designing future UPSH plants.

We report a data-set of CO2, CH4, and N2O concentrations in the surface waters of the Meuse river network in Belgium, obtained during four surveys covering 50 stations (summer 2013 and late winter 2013, 2014 and 2015), from yearly cycles in four rivers of variable size and catchment land cover, and from 111 groundwater samples. Surface waters of the Meuse river network were over-saturated in CO2, CH4, N2O with respect to atmospheric equilibrium, acting as sources of these greenhouse gases to the atmosphere, although the dissolved gases also showed marked seasonal and spatial variations. Seasonal variations were related to changes in freshwater discharge following the hydrological cycle, with highest concentrations of CO2, CH4, N2O during low water owing to a longer water residence time and lower currents (i.e. lower gas transfer velocities), both contributing to the accumulation of gases in the water column, combined with higher temperatures favourable to microbial processes. Inter-annual differences of discharge also led to differences in CH4 and N2O that were higher in years with prolonged low water periods. Spatial variations were mostly due to differences in land cover over the catchments, with systems dominated by agriculture (croplands and pastures) having higher CO2, CH4, N2O levels than forested systems. This seemed to be related to higher levels of dissolved and particulate organic matter, as well as dissolved inorganic nitrogen in agriculture dominated systems compared to forested ones. Groundwater had very low CH4 concentrations in the shallow and unconfined aquifers (mostly fractured limestones) of the Meuse basin, hence, should not contribute significantly to the high CH4 levels in surface riverine waters. Owing to high dissolved concentrations, groundwater could potentially transfer important quantities of CO2 and N2O to surface waters of the Meuse basin, although this hypothesis remains to be tested.

The impacts induced by the interaction between underground constructions and groundwater should be minimised by implementing corrective measures. These impacts are twofold, which means that underground constructions affect groundwater, and vice versa. Two common situations resulting from this interaction are the barrier effect (impact of an underground construction on groundwater) and groundwater pressure on the bottom slab (impact of groundwater on an underground construction). In the literature, there are examples and designs of mitigation measures to minimise both impacts. However, to the best of the authors’ knowledge, there are not any designs that combine corrective measures to minimise these simultaneously. This paper proposes an innovative groundwater by-pass design to mitigate the barrier effect and to alleviate the groundwater pressure on the bottom slab. The proposed integrated design was applied to the largest underground infrastructure in Barcelona: the Sagrera railway station. The design was tested and compared numerically with a solution initially designed (not integrated). The numerical comparison was undertaken with three different hydrogeological scenarios. The proposed integrated design mitigated the barrier effect and optimised the bottom slab. It considerably reduced costs and increased safety during the construction phase.

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 Adria del Besos (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.

This work presents the occurrence and fate of selected personal care products (PCPs) in the urban river-groundwater interface. To this end, urban river and groundwater samples were collected in Sant Adrià del Besòs (NE of Spain) and a total of 16 PCPs were analyzed including benzophenone derivatives, camphor derivatives, p-aminobenzoic acid derivatives, triazoles and parabens in three different campaigns (from May 2010 to July 2014). These compounds reach the aquifer through the recharge of Besòs River that receives large amounts of effluents from waste water treatment plants. Results have shown that most of the compounds were not or barely detected (maximum concentrations around 200ng/L) in groundwater samples during the different sampling campaigns. Only two triazoles, namely benzotriazole (BZT) and methyl benzotriazol (MeBZT) were found at high concentrations in groundwater samples (maximum concentration around 2000ng/L). The fate of PCPs in the aquifer was assessed using mixing analysis considering the seasonal variability of the Besòs River. Overall, measured groundwater concentrations were significantly much lower than those estimated by the mixing of the river water. This observation suggested that most of the PCPs are naturally removed when river water infiltrates the aquifer. However, some compounds were more persistent in the aquifer. These compounds were in descending order: the triazoles BZT and MeBZT followed by the camphor derivative 4MBC and the paraben MePB. The measured concentrations allowed us to assess the environmental risk posed by the selected UV-filters and parabens in the river and groundwater samples. Hazard Quotients (HQs) for different aquatic species were calculated in order to characterize the ecotoxicity potential of the studied compounds in the river-groundwater interface. HQ values were always below 1 indicating that at the concentrations observed in the surface or aquifer water of Besòs River these compounds pose no risk to the selected aquatic organisms.

One of the main causes of problems during the construction of tunnels with tunnel boring machines (TBMs) is a lack of characterization of the soil. Both geological and hydrogeological characterizations are essential to avoid unexpected events. The advance of TBMs produces groundwater oscillations due to hydraulic and mechanical effects. The magnitude of these oscillations depends on the characteristics of the soil and on the “parameters” of the TBM (e.g., earth pressures, penetration). Given that the impact caused in the groundwater could be estimated numerically, this paper proposes to use hydrogeological models based on the parameters of the TBM to validate or improve the previous geological characterization. This procedure was tested by modelling the advance of a TBM-type earth pressure balance (EPB) at a real site. This study arose during the construction of the tunnel for the high speed train in Barcelona. The previous geological characterization revealed a vertical fault whose exact position was unknown. The advance of the EPB was modelled to validate the previous characterization and to locate the fault. The numerical model included a detailed geology and hydrogeology of the study site and the parameters of the EPB. Note that the parameters of the EPB used in the model were more related to the groundwater response. These were determined statistically from all of the measures taken by the machine. Given the results obtained, hydrogeological modelling of EPBs was revealed to be a useful tool to validate previous characterizations, both the geological and the hydrogeological, and to determine the position of some geological structures, such as faults.

Excavations below the water table are usually undertaken by combining the protection of retaining walls with dewatering by pumping wells. Severe difficulties may arise if the retaining walls have defects. Therefore, their state must be determined and, if needed, the defects repaired or the dewatering system redesigned. The state of underground retaining walls can be evaluated using hydrogeological methods, but these methods are well-established only for linear excavations. The objective of this work is to propose a procedure to evaluate the state of non-linear underground enclosures by analysing the groundwater response to pumping inside the enclosure. The proposed method, which is based on diagnostic plots (derivative of drawdown with respect to the logarithm of time), allows (1) determining if an underground non-linear enclosure has isolated openings or numerous defects and (2) computing its effective conductance or effective hydraulic conductivity. The methodology is tested with data collected during the excavation of a shaft required for the construction of the high speed train (HST) tunnel in Barcelona, Spain. The procedure can be applied using the wells drilled for dewatering. Although a test before the excavation is recommended to evaluate the underground retaining walls (Watertightness Assessment Test), the method can be applied using data collected at the beginning of the dewatering stage.

Antibiotics, such as sulfonamides (SAs), have recently raised concern as wastewater treatment plants (WWTPs) partly remove them, and thus, SAs continuously enter the aquifers. In this context, the aims of this work are to (1) investigate the temporal evolution of SAs and metabolites in an urban aquifer recharged by a polluted river; (2) identify the potential geochemical processes that might affect SAs in the river-groundwater interface and (3) evaluate the ecological and human health risk assessment of SAs. To this end, 14 SAs and 4 metabolites were analyzed in river and urban groundwater from the metropolitan area of Barcelona (NE, Spain) in three different sampling campaigns. These substances had a distinct behavior when river water, which is the main recharge source, infiltrates the aquifer. Mixing of the river water recharge into the aquifer drives several redox reactions such as aerobic respiration and denitrification. This reducing character of the aquifer seemed to favor the natural attenuation of some SAs as sulfamethoxazole, sulfapyridine, and sulfamethizole. However, most of the SAs detected were not likely to undergo degradation and adsorption because their concentrations were constant along groundwater flow path. In fact, the intensity of SAs adsorption is low as the retardation factors are close to 1 at average groundwater pH of 7.2 for most SAs. Finally, risk quotients (RQs) are used to evaluate the ecological and human health risks posed by single and mixture of SAs in river water and groundwater, respectively. Life-stage RQs of the SAs detected in groundwater for the 8 age intervals were low, indicating that SAs and their mixture do not pose any risk to human beings. Concerning the environmental risk assessment, SAs do not pose any risk for algae, fish and crustaceans as the RQs evaluated are further lower than 0.1., A.J acknowledges the support from the Secretary for Universities and Research of the Ministry of Economy and Knowledge of the Government of Catalonia and the Marie Sklodowska-Curie COFUND of the programme H2020 (BP3, contract number 801370). M.S.D.C acknowledges the Generalitat de Catalunya (Water and Soil Quality Unit, 2017-SGR-1404) and the Spanish Ministry of Science and Innovation (Project CEX 2018-000794-S). E.V.S would like to thank the European Commission, the Spanish Foundation for Science & Technology (FECYT) and State Research Agency (AEI)) for funding in the frame of the collaborative international consortium (URBANWAT) financed under the 2018 Joint call of the WaterWorks2017 ERA-NET Cofund. This ERA-NET is an integral part of the activities developed by the Water JPI. Additionally E.V.S also thank the Ministry of Science, Innovation and Universities, for funding the project UNBIASED (Ref: RTI 2018-097346-B-I00) under the 2018 call of the “Proyectos de I + D Retos Investigación.

AkvaGIS is a novel, free and open source module included in the FREEWAT plugin for QGIS that supplies a standardized and easy-to-use workflow for the storage, management, visualization and analysis of hydrochemical and hydrogeological data. The main application is devised to simplify the characterization of groundwater bodies for the purpose of building rigorous and data-based environmental conceptual models (as required in Europe by the Water Framework Directive). For data-based groundwater management, AkvaGIS can be used to prepare input files for most groundwater flow numerical models in all of the available formats in QGIS. AkvaGIS is applied in the Walloon Region (Belgium) to demonstrate its functionalities. The results support a better understanding of the hydrochemical relationship among aquifers in the region and can be used as a baseline for the development of new analyses, e.g., further delineation of nitrate vulnerable zones and management of the monitoring network to control chemical spatial and temporal evolution. AkvaGIS can be expanded and adapted for further environmental applications as the FREEWAT community grows. © 2018 The Authors, Funding text This paper is presented within the framework of the project FREEWAT , which received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement n. 642224 . R. Criollo thanks the financial support from the Catalan Industrial Doctorates Plan of the Secretariat for Universities and Research , Ministry of Economy and Knowledge of the Generalitat de Catalunya . A. Jurado and E. Pujades gratefully acknowledge the financial support from the University of Liège and the EU through the Marie Curie BeIPD-COFUND postdoctoral fellowship programme (2015–2017 and 2014–2016 fellows from FP7-MSCA-COFUND , 600405 ).

Water scarcity periods will increase in frequency and magnitude in the near future, especially in Mediterranean regions, and proper groundwater management has been recognized as a key issue to mitigate possible impacts. In this context, numerical models acquire a special relevance to quantify the availability of water resources and predict their behavior under changing climate conditions. This work shows the procedure followed to model a mountainous fractured aquifer located in the northern Apennines (Italy) using an open source code. This aquifer feeds springs with an average discharge of about 96.8 L/s. Even though they are not exploited at the moment, these springs might represent a relevant resource of freshwater for public water supply and are essential for ecosystem sustainment. The main limitation faced to model the aquifer in a realistic way is the lack of data, which hinders the calibration of the model. A nonconventional procedure was followed to obtain information on the hydraulic parameters. The hydraulic conductivity is computed from a steady-state calibration for which a limited number of groundwater head observations are available, whilst information concerning the storage coefficient is obtained analytically from the spring discharge recession curve. Finally, the model is used for predicting the system behavior under different groundwater recharge scenarios. Numerical simulations and analytical approximations reveal that the studied aquifer can provide fresh water under different groundwater recharge conditions and has the capacity to smooth the effects of short drought periods, representing an option for water management strategies in the region.

The aim of this study is to investigate the occurrence of faecal indicator and microbial pathogens (bacteria and virus) in the shallow urban aquifer of the Besòs River Delta (NE Spain). To this end, human adenovirus (HAdV) and Norovirus of genogroups I and II (NoV GI and NoV GII) as well as the faecal indicator bacteria (FIB) Escherichia coli (EC) and faecal enterococci (FE) were monitored in groundwater and in the River Besòs in December 2013 and in July 2104. None of the targeted pathogens were detected in groundwater in December 2013 but contamination of human origin was observed in approximately 50% of the points sampled in July 2014 reaching concentrations up to 99 GC/100 mL for HAdV. Generally, microbial concentrations in river water were higher than those detected in groundwater. This observation indicates that pathogens are naturally attenuated when river water infiltrates and flows through the aquifer, however HAdV were detected at a sampling point located at 380 m from the river in the absence of FIB. The presence of human viral contamination may represent a risk for the use of groundwater as a drinking water source. Further research is needed to understand the dynamics of pathogens in river–groundwater interface over long time periods and a wide range of flow conditions (wet and dry periods) since the urban groundwater of this aquifer might be a valuable drinking water resource in Barcelona especially during drought periods. The methodology followed in this research can be applied to other urban aquifers with similar purposes since the scarcity and contamination of freshwater resources are worldwide issues. © 2019 Elsevier B.V., A. J gratefully acknowledges the financial support from the Excellence Initiative of the German Federal and State Governments through the “Open Topic Postdoc Position Fellow” at the Technische Universität Dresden. The authors would like to thank the European Commission, the Spanish Foundation for Science and Technology (FECYT) and Spanish State Research Agency (AEI) for funding in the frame of the collaborative international consortium (URBANWAT) financed under the 2018 Joint call of the WaterWorks2017 ERA-NET Cofund. This ERA-NET is an integral part of the activities developed by the Water JPI. Additionally authors would also thank the Ministry of Science, Innovation and Universities, for funding the project UNBIASED (Ref: RTI2018-097346-B-I00) under the 2018 call of the “Proyectos de I+D Retos Investigación.

This paper aims to review the existing occurrence data in Spanish groundwater (GW) for the emerging organic contaminants (EOCs) defined in the surface water Watch Lists of Decisions 2015/495/EU and 2018/840/EU since these contaminants are likely to reach GW bodies because surface waters show close interaction with GW. These two lists include 20 substances: 9 pesticides (5 neonicotinoids, 2 carbamates, 1 oxadiazole and 1 semicarbazone), 6 pharmaceuticals (diclofenac and 5 antibiotics), 3 estrogens, 1 UV filter (2-ethylhexyl-4-methoxycinnamate, EHMC) and 1 antioxidant (2,6-di-tert-butyl-4-methylphenol, BHT). Most of these substances are usually detected at low ng/L concentration range or not detected in the GW bodies of Spain. However, eventually they are reported at concentrations > 100 ng/L (e.g., imidacloprid, methiocarb, diclofenac, macrolide antibiotics, ciprofloxacin, EHMC and BHT). Consequently, it is required to set up drinking water standards, and/or GW threshold quality values because GW is a valuable water resource worldwide. Overall, GW is less contaminated than other water bodies, such as rivers, suggesting that aquifers possess a natural attenuation capacity and/or are less vulnerable than rivers to contamination. Nevertheless, the natural hydrogeochemical processes that control the fate and transformation of these substances during infiltration and in the aquifer have been barely investigated so far. The concentrations of the target EOCs are used to calculate hazard quotients (HQs) in the Spanish GW bodies as an estimation of their ecotoxicity and in order to compare somehow their chemical quality with respect to those of surface water. Due to the limited ecotoxicity data for most EOCs, HQs can only be calculated for few substances. The results pointed out the risk posed by the anti-inflammatory diclofenac towards Ceriodaphnia dubia (HQ = 21) and the medium risk associated to the antibiotic erythromycin for Brachionus calyciflorus (HQ = 0.46). © 2019 Elsevier B.V., AJ gratefully acknowledges the financial support from the Excellence Initiative of the German Federal and State Governments through the “Open Topic Postdoc Position” Fellow at the Technische Universität Dresden . MSDC acknowledges the Spanish Ministry of Science, Innovation and University and the European Commission (Project ACWAPUR PCIN 2015-245 ). Appendix A

This work is motivated by a sound understanding of the chemical processes that affect the organic pollutants in an urban aquifer. We propose an approach to quantify such processes using mixing calculations. The methodology consists of the following steps: (1) identification of the recharge sources (end-members) and selection of the species (conservative and non-conservative) to be used, (2) identification of the chemical processes and (3) evaluation of mixing ratios including the chemical processes. This methodology has been applied in the Besòs River Delta (NE Barcelona, Spain), where the River Besòs is the main aquifer recharge source. A total number of 51 groundwater samples were collected from July 2007 to May 2010 during four field campaigns. Three river end-members were necessary to explain the temporal variability of the River Besòs: one river end-member is from the wet periods (W1) and two are from dry periods (D1 and D2). This methodology has proved to be useful not only to compute the mixing ratios but also to quantify processes such as calcite and magnesite dissolution, aerobic respiration and denitrification undergone at each observation point.

This work aims to (1) identify the most conductive conditions for the generation of greenhouses gases (GHGs) in groundwater (e.g., hydrogeological contexts and geochemical processes) and (2) evaluate the indirect emissions of GHGs from groundwater at a regional scale in Wallonia (Belgium). To this end, nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) concentrations and the stable isotopes of nitrate (NO3-) and sulphate were monitored in 12 aquifers of the Walloon Region (Belgium). The concentrations of GHGs range from 0.05μg/L to 1631.2μg/L for N2O, 0μg/L to 17.1μg/L for CH4, and 1769 to 100,514ppm for the partial pressure of CO2 (pCO2). The highest average concentrations of N2O and pCO2 are found in a chalky aquifer. The coupled use of statistical techniques and stable isotopes is a useful approach to identify the geochemical conditions that control the occurrence of GHGs in the aquifers of the Walloon Region. The accumulation of N2O is most likely due to nitrification (high concentrations of dissolved oxygen and NO3- and null concentrations of ammonium) and, to a lesser extent, initial denitrification in a few sampling locations (medium concentrations of dissolved oxygen and NO3-). The oxic character found in groundwater is not prone to the accumulation of CH4 in Walloon aquifers. Nevertheless, groundwater is oversaturated with GHGs with respect to atmospheric equilibrium (especially for N2O and pCO2); the fluxes of N2O (0.32kgN2O-NHa-1y-1) and CO2 (27kgCO2Ha-1y-1) from groundwater are much lower than the direct emissions of N2O from agricultural soils and fossil-fuel-related CO2 emissions. Thus, indirect GHG emissions from the aquifers of the Walloon Region are likely to be a minor contributor to atmospheric GHG emissions, but their quantification would help to better constrain the nitrogen and carbon budgets.

This paper deals with urban groundwater contaminated with carbamazepine (CBZ) and five of its human metabolites in Barcelona. Groundwater samples were accordingly collected in the aquifers of Poble Sec and Besos River Delta. Higher concentrations and more compounds were found in the Besos River Delta aquifer, which is recharged by a river contaminated with treated effluent from numerous treatment plants. By contrast, the urban area of Poble Sec presented lower concentrations and fewer compounds. The results showed that CBZ could be attenuated in the Poble Sec aquifer since concentrations in groundwater were lower than those evaluated from mixing of the recharge sources. Conversely, CBZ and its human metabolites were not removed under the reducing conditions of the Besos River Delta aquifer probably because of the short residence time in this aquifer. (C) 2014 Elsevier Ltd. All rights reserved.

The present paper presents the occurrence of 72 pharmaceuticals and 23 transformation products (TPs) in groundwaters (GWs) underlying the city of Barcelona, Spain. Thirty-one samples were collected under different districts, and at different depths. Aquifers with different geologic features and source of recharge were included, i.e., natural bank filtration, infiltration from wastewater and water supply pipes, rainfall recharge, etc. Antibiotics were the most frequently found compounds detected at levels reaching 1000 ng L −1 . Natural bank filtration from the river that receives large amounts of effluents from waste water treatment plants (WWTPs), turned out being the most influencing source of contamination, thus GW showed high range of compounds and concentrations as high as or even higher than in the river itself. In general, TPs were found at lower concentrations than the corresponding parent compounds, with some exceptions, such as 4OH propranolol and enalaprilat.

This work reviews applications of stable isotope analysis to the studies of transport and transformation of N species in groundwater under agricultural areas. It summarizes evidence regarding factors affecting the isotopic composition of NO3-, NH4+ and N2O in subsurface, and discusses the use of 11B, 18O, 13C, 34S, 87Sr/86Sr isotopes to support the analysis of δ15N values. The isotopic composition of NO3-, NH4+ and N2O varies depending on their sources and dynamics of N cycle processes. The reported δ15N-NO3- values for sources of NO3- are: soil organic N - +3‰-+8‰, mineral fertilizers - -8‰-+7‰; manure/household waste - +5‰ to +35‰. For NH4+ sources, the isotopic signature ranges are: organic matter - +2.4-+4.1‰, rainwater - -13.4-+2.3‰, mineral fertilizers - -7.4-+5.1‰, household waste - +5-+9‰; animal manure - +8-+11‰. For N2O, isotopic composition depends on isotopic signatures of substrate pools and reaction rates. δ15N values of NO3- are influenced by fractionation effects occurring during denitrification (ɛ=5-40‰), nitrification (ɛ=5-35‰) and DNRA (ɛ not reported). The isotopic signature of NH4+ is also affected by nitrification and DNRA as well as mineralization (ɛ=1‰), sorption (ɛ=1-8‰), anammox (ɛ=4.3-7.4‰) and volatilization (ɛ=25‰). As for the N2O, production of N2O leads to its depletion in 15N, whereas consumption - to enrichment in 15N. The magnitude of fractionation effects occurring during the considered processes depends on temperature, pH, DO, C/NO3- ratio, size of the substrate pool, availability of electron donors, water content in subsoil, residence time, land use, hydrogeology. While previous studies have accumulated rich data on isotopic composition of NO3- in groundwater, evidence remains scarce in the cases of NH4+ and N2O. Further research is required to consider variability of δ15N-NH4+ and δ15N-N2O in groundwater across agricultural ecosystems.

Underground Pumped Storage Hydropower (UPSH) is an alternative to manage the electricity production in flat regions. UPSH plants consist of two reservoirs of which at least one is underground. For this last reservoir, abandoned mines could be considered. UPSH related activities may induce hydrochemical variations, such as the increase of the oxygen (O2) partial pressure (pO2), which may entail negative consequences in terms of environment and efficiency, especially in coal mined areas where the presence of sulfide minerals is common. This work assesses the main expected environmental impacts that UPSH using abandoned coal mines may induce. © 2017 The Authors. Published by Elsevier Ltd., E. Pujades and A. Jurado gratefully acknowledge the financial support from the University of Liège and the EU through the Marie Curie BeIPD-COFUND postdoctoral fellowship programme (2014/16 and 2015/17 fellows from “FP7-MSCA-COFUND, 600405”). This research has been supported by the Public Service of Wallonia – Department of Energy and Sustainable Building.

This work reviews the concentrations, the dynamics and the emissions of nitrous oxide (N

This study is concerned with drugs of abuse (DAs) and their metabolites in urban groundwater at field scale in relation to (1) the spatial distribution of DAs in Barcelona's groundwater, (2) the depth of the groundwater samples, (3) the presence of DAs in recharge sources, and (4) the assessment of the fate of DAs in Barcelona aquifers. To this end, 37 urban groundwater samples were collected in the city of Barcelona and a total of 21 drugs were analyzed including cocainics, amphetamine-like compounds, opioids, lysergics and cannabinoids and the prescribed drugs benzodiazepines. Overall, the highest groundwater concentrations (around 200 ng/L in SAP-4) and the largest number of detected DAs were found in zones basically recharged by a river that receives large amounts of effluents from waste water treatment plants (WWTPs). In contrast, the urbanized areas yielded not only lower concentrations but also a much smaller number of drugs, which suggests a local origin. In fact, cocaine and its metabolite were dominant in more prosperous neighborhoods, whereas the cheaper MDMA was the dominant DA in poorer districts. Measured concentrations were consistently smaller than those estimated from the waste water fraction in groundwater samples, suggesting that DAs undergo removal processes in both reducing and oxidizing conditions.

Construction of underground structures (e.g., subway lines, railways and highway tunnels) is inherently hazardous, posing risks to both workers and machinery at the site and to surrounding buildings. The presence of groundwater may increase these risks. We develop a general probabilistic risk assessment (PRA) framework to quantify risks driven by groundwater to the safety of underground constructions. The proposed approach is fully compatible with standard PRA practices, employing well-developed risk analysis tools based on the fault tree analysis method. The novelty and computational challenges of the proposed approach stem from the reliance on a combination of approaches including extracting information from databases, solving stochastic differential equations, or relying on expert judgment to compute probabilities of basic events. The general framework is presented in a case study and used to estimate and minimize risks at a construction site of an underground station for a new subway line in the Barcelona metropolitan area.

Underground linear excavations often encounter problems when crossing aquifers. A viable option for shallow tunnels is the “cut and cover method”. Still, when enclosing diaphragm walls display open joints, even this method risks flooding, which affects construction operations, and soil dragging, which may lead to subsidence and affect nearby buildings outside the enclosure. Characterizing the state of the enclosure prior to excavation would be desirable. We propose in doing so by analysing the response to groundwater pumping during dewatering. We use numerical modelling and analytical methods. The steady state heads along the enclosure and the variations in the flow behaviour during pumping depend on the state of the diaphragm walls. Monitoring of the heads is therefore proposed during drainage of the enclosure to characterize the diaphragm walls. An analytical solution in steady state and two transient state methodologies are presented. These methodologies are implemented to evaluate the state of the diaphragm walls used in the construction of a High Speed tunnel at Bellvitge near Barcelona, where large openings caused significant sediment drag, which provoked sinkholes outside the enclosure.

In this chapter we take a look at the presence of emerging organic compounds (EOCs) in groundwater, with emphasis in sources of pollution, processes affecting the spatial and temporal concentration of these compounds as they move through the aquifer and interact with the soil. Emphasis is placed on the combination of transport mechanisms and physical and biogeochemical processes that combine for natural attenuation and the potential eventual output to the biosphere. Some considerations about risks associated to the presence of such substances are also included.

A tunnel for the High Speed Train (HST) was constructed in Barcelona with an Earth Pressure Balance (EPB) Tunnel Boring Machine (TBM). The tunnel crosses Barcelona and passes under some famous landmarks such as the Sagrada Familia and the Casa Mill Both monuments are UNESCO world heritage sites and a committee appointed by the UNESCO acted as external observers during the construction. Concerns about soil settlements and the hydrogeological impacts of the construction were raised. These concerns were addressed during the design stage to forestall any unexpected events. The methodology consisted of 1) characterising the geology in detail, 2) predicting the impacts caused in the aquifer, 3) predicting the soil displacements due to water table oscillations produced by the construction, and 4) monitoring the evolution of groundwater and soil settlements. The main estimated impact on groundwater was a moderate barrier effect. The barrier effect, the magnitude of which matched the predictions, was detected during construction. The monitoring of soil settlements revealed short and long term movements. The latter movements matched the analytical predictions of soil displacements caused by the groundwater oscillations. This paper proposes a realistic procedure to estimate impacts on groundwater during tunnel construction with an EPB. Our methodology will considerably improve the construction of tunnels in urban areas. (C) 2015 Elsevier B.V. All rights reserved.