This paper reviewed the presence of emerging organic contaminants (EOCs) that have been found in the groundwater in Spain in both, rural and urban areas. The list of compounds included pesticides, ...pharmaceutical active compounds (PhACs), selected industrial compounds, drugs of abuse (DAs), estrogens, personal care products and life-style compounds. The main sources of pollution and possible pathways have been summarised in this review. EOCs are likely to enter to the aquifer mainly through the effluents of waste water treatment plants (WWTPs) and are present in groundwater at concentrations of ng/L to μg/L. The most studied compounds in Spanish groundwater were pesticides followed by industrial compounds and PhACs. It is important to mention that compared to other water bodies, such as rivers, groundwater is considerably less contaminated, which may be indicative of the natural attenuation capacity of the aquifers. However, some EOCs have sometimes been detected at higher concentration levels in the aquifer than in the rivers, indicating the need for further research to understand their behaviour in the aquifers. For a wide array of compounds, their maximum concentrations show values above the European groundwater quality standard for individual pesticides (0.1μg/L). Therefore, to preserve groundwater quality against deterioration it is necessary to define environmental groundwater thresholds for the non-regulated compounds.
► Emerging organic contaminants (EOCs) are reviewed in groundwater in Spain. ► These include pesticides, pharmaceuticals and drugs of abuse. ► Groundwater is considerably less contaminated than other water bodies. ► There is insufficient information to assess the fate of EOCs in the aquifers. ► Establishment of environmental threshold value to protect groundwater quality.
•Rainfall is reduced in heavy isotopes from east to west in the Eastern Cordillera.•The air masses originating from different oceans mix in the Western Cordillera.•The mixture of air masses makes the ...interpretation of isotopes in rain complex.
This review concerns the knowledge of the isotopic composition of current precipitation and its association with climate, geography and orography, in the Central Andes (14–28°S and 75–63°W). This knowledge is required for the evaluation of other hydrological values, especially aquifer recharge and water resources, in environments varying from rainy to hyper-arid. Since the 1960s, oxygen (δ18O) and deuterium (δ2H) isotope composition of natural water have been used as tracers of the global hydrological cycle. In the present article, the goal is to identify the origin and trajectory of air masses that produce rainfall in the Central Andes and the isotopic composition of the precipitation, as a first step to evaluate recharge and groundwater resources.
The isotopic composition of rainfall varies spatially and temporarily, depending on the climatic phenomena that originate the movement of air masses, their moisture content and the isotope fractionation processes that occur until precipitation falls. Most of the significant and recent literature on the mechanisms of δ18O and δ2H transport and fractionation in precipitation along the Central Andes has been collected and summarized in this review. Precipitation in the eastern and central Andes comes mainly from the humidity generated in the Atlantic Ocean. Although the processes involved in isotope content variability of precipitation are well known, the processes involved in isotopic variability in the Western Cordillera remain poorly understood. This is mostly due to mixing of different moisture sources: from the Atlantic Ocean in summer and from the Pacific Ocean in winter. In general, winter rainfall is more enriched in δ18O and δ2H than summer rainfall. Looking at existing data, their distribution is far from being homogeneous and well-distributed, so spatial accuracy is poor in some areas, especially in the Altiplano. Hydrological and hydrogeological research and water resources evaluation in the Central Andes would greatly benefit from initiatives to obtain broader spatial coverage of rainfall collection to get isotope data for more accurate and continuous assessment of the local weather patterns. Groundwater isotope composition is a future tool to help in increasing the coverage in data scarce areas.
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.
► Comprehensive study of 95 pharmaceuticals in Barcelona's groundwater. ► Concentration levels found were higher than expected for groundwater. ► Transformation products significantly contributed to the overall levels.
Ninety-five pharmaceuticals and transformation products are monitored in the groundwater from Barcelona metropolitan area.
•UV filters are found for the first time in urban groundwater.•Leaks from sewage networks are the main source of UV filters in the aquifers studied.•Compounds with anionic properties are more mobile ...in aquifers.•Attenuation of UV filters in the aquifer occurs under different redox conditions.
The occurrence and fate of UV filters (UV F) in an urban aquifer in correlation with (1) the spatial distribution of UV F in Barcelona’s groundwater, (2) the depth of the groundwater sample, (3) the physicochemical properties of the target compounds, (4) the recharge sources, and (5) the redox conditions of the Barcelona aquifers, were studied for the first time. The highest groundwater concentrations and the largest number of detected UV F were observed in an aquifer recharged by a polluted river (around 55ng/L in SAP-4). In contrast, the urbanized areas had lower concentrations (around 20ng/L in MPSP-1). Two pathways can be identified for UV F to enter the aquifers: (1) leakage of row sewage from the sewage network in urbanized areas and (2) wastewater treatment plant (WWTP) effluents discharged into the river. Measured concentrations of UV F were significantly much lower than those estimated from the waste water proportion in groundwater samples suggesting that UV F might undergo transformation processes in both reducing and oxidizing conditions.
In order to carry out deep excavations under the water table in urban environments, the safety of the work site and of the adjacent buildings is a major cause for concern. One of the most common and ...effective methods of undertaking these excavations involves combining the cut and cover method with a dewatering system. The success of a construction depends on the stability of the excavation bottom, the effects produced outside the excavation by dewatering (soil movements) and/or the state of the enclosure (defects in the diaphragm walls). This study proposes a realistic multidisciplinary procedure to address these issues. The work emphasizes the importance of soil characterisation and underlines the need to perform a Watertightness Assessment Test (WTAT) before the excavation stage. The procedure was applied to the excavation of a deep shaft of the High Speed Train (HST) tunnel in Barcelona. An earlier geological characterisation at large scale ruled out the use of deep pumping wells. However, a subsequent hydrogeological characterisation, which involved borehole logging, grain size analyses, Natural Gamma Ray and pumping tests, revealed the presence of thin transmissive layers inside the low hydraulic conductivity materials. The dewatering system was designed by considering different model scenarios and the safest design was selected for the excavation. Depths of the enclosure and of the pumping wells differed in accordance with the scenarios. The impacts (settlements due to pumping) and the stability in each scenario were computed. The state of the enclosure underwent a WTAT before the start of the excavation, but after constructing the enclosure, to verify its low permeability. The test consisted in pumping inside the enclosure and monitoring the groundwater behaviour outside the enclosure. Numerical interpretation of this test showed a defect in the diaphragm walls below the excavation bottom. Since this defect was not repaired because of its location (below the bottom of the excavation), the dewatering system had to be redesigned to ensure safety. Surface settlements, which were also a source of concern, were small. They were computed using coupled hydro-mechanical models.
•Hydrogeological characterisation is crucial to design suitable dewatering systems.•Combining the cut and cover method with deep wells is efficient to deep excavations.•Defects in underground enclosures are relatively common.•Underground enclosures must be assessed before the excavation.•Watertightness Assessment Tests (WTAT) should be performed to assess enclosures.
•Pumping settlements rarely agree with the measured ones.•Mechanical boundary conditions must be considered to estimate pumping settlements.•Pumping settlements are not proportional to the drawdown ...near the pumping well.•Poorly conductive layers mitigate pumping settlements towards the surface.•An analytical solution is proposed to compute pumping settlements.
Estimated and measured settlements caused by pumping rarely agree. Several reasons could explain this mismatch, including the influence of layering, the mechanical parameters used in the predictions, or the relationship between settlements and drawdown. We analyze the influence of the above issues by investigating the mechanical response of pumped elastic porous media under different conditions. A radially symmetric conceptual model is considered and several hydro-mechanical simulations are performed varying the boundary conditions, the size of the modeled domain and the presence or not of an overlying layer. The simplicity of the considered problem allows us to compare our results with existing analytical solutions, to identify the role of each variable on pumping settlements and to generalize the results. The most relevant results are as follows: (1) settlements are proportional to drawdown only outside a circle of radius equal to 0.7 times the thickness of the pumped porous medium; inside, they are virtually constant, which leads to two simple procedures for computing pumping settlements. (2) Poorly conductive layers located above (or below) a pumped porous medium (with higher hydraulic conductivity) reduce and smooth settlements. (3) Boundary constraints affect the local specific storage coefficient and the displacements occurred. (4) The specific storage coefficient evaluated by interpreting pumping tests with the Cooper and Jacob method (1946) leads to overestimation of the actual Young’s Modulus of the soil. The main conclusion is that settlements are less differential than expected near pumping wells. Still, they must always be evaluated acknowledging the nature of layering, the boundary constraints and carefully selecting the mechanical parameters of the soil.
Groundwater management in urban areas requires a detailed knowledge of the hydrogeological system as well as the adequate tools for predicting the amount of groundwater and water quality evolution. ...In that context, a key difference between urban and natural areas lies in recharge evaluation. A large number of studies have been published since the 1990s that evaluate recharge in urban areas, with no specific methodology. Most of these methods show that there are generally higher rates of recharge in urban settings than in natural settings. Methods such as mixing ratios or groundwater modeling can be used to better estimate the relative importance of different sources of recharge and may prove to be a good tool for total recharge evaluation. However, accurate evaluation of this input is difficult. The objective is to present a methodology to help overcome those difficulties, and which will allow us to quantify the variability in space and time of the recharge into aquifers in urban areas. Recharge calculations have been initially performed by defining and applying some analytical equations, and validation has been assessed based on groundwater flow and solute transport modeling. This methodology is applicable to complex systems by considering temporal variability of all water sources. This allows managers of urban groundwater to evaluate the relative contribution of different recharge sources at a city scale by considering quantity and quality factors. The methodology is applied to the assessment of recharge sources in the Barcelona city aquifers.
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•Groundwater management in urban areas requires adequate tools.•A key difference in urban and natural areas lies in recharge evaluation.•This methodology allows to quantify the recharge into aquifers in urban areas.•Recharge calculations by defining and applying some analytical equations.•Validation is assessed based on groundwater flow and solute transport modeling.
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•The meteorological variables are correlated with altitude, latitude and longitude.•Temperature, altitude, latitude and longitude control the δ18O of precipitation.•Unrecorded ...rainfall in sampling points is obtained by means of correlation models.•These models are useful if the available data are scarce and discontinuous in time.•Aquifer recharge zones are identified by estimating δ18O values with these models.
A knowledge of the evolution of isotopic composition of air masses humidity and precipitation in the Western Cordilleras of the Central Andes is still incomplete. This study contributes to a better understanding of the factors that control the δ18O and δ2H contents in precipitation water in the north of Chile, above 2000 m a.s.l.. This paper deals with: (1) the relevant effects and processes that control the spatial (longitude, latitude and altitude) distribution of stable isotope contents of precipitation events in northern Chile, (2) the influence of local meteorological variables: temperature, precipitation and relative humidity on the δ18O and δ2H of precipitation, and (3) the estimation of these meteorological and isotopic variables at specific sites. To achieve these objectives, the relationships between geospatial and meteorological values are identified and analysed, followed by the estimation with empirical models. These estimation models (linear and non-linear) are obtained after examining, validating and calibrating techniques to find the best fit. This results in models for temperature, relative humidity and precipitation for each month of the year. In the same way, three isotopic models are derived from the spatial and meteorological variables (summer, winter and annual). Temperature has been shown to be controlled to a greater extent by altitude and latitude, while relative humidity is by latitude and precipitation in summer is by altitude and latitude. Monthly meteorological variables have been estimated throughout the study area. Precipitation δ18O and δ2H are controlled mainly by temperature and altitude and to a lesser extent by latitude, longitude and precipitation. In the same way, three isotopic models are derived from the spatial and meteorological variables: summer, winter and annual. This opens a new perspective of precipitation and its isotopic contents, but also allows the calculation of runoff and aquifer recharge and the path for linking future precipitation and aquifer recharge through their isotopic composition.
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.
•Defects are common in retaining walls used to underground excavations•The state of the underground enclosure must be known prior to the excavation•Groundwater response to pumping inside the enclosure depends on its properties•Diagnostic plots are used to assess non-linear underground enclosures•The method allows assessing the effective hydraulic conductivity of underground enclosures
To reduce uncertainty in the identification of the recharge areas in the Peripheral Aquifer of the Salar de Atacama (SdA), a few studies have investigated the isotopic characteristics and moisture ...sources of precipitation in the SdA basin. In the present study, the seasonal cycle of meteorological parameters and the relationships of this cycle with sea surface temperature anomalies are shown, the sources of humidity are identified, and the types of clouds producing precipitation are defined. Finally, the isotopic compositions of precipitation, surface water and groundwater in the SdA basin and the Altiplano-Puna Plateau basins are analysed to identify the area recharging the northern, eastern and southern subbasins of the SdA. In summer, when the highest temperature, relative humidity and precipitation values of the year are recorded, the precipitation is due to deep convection. The trajectories of the arriving air masses can be classified into three groups: from the North Atlantic Ocean across the Amazon basin, from the South Atlantic Ocean across the La Plata River basin and the Gran Chaco, and from the Pacific Ocean. In winter, when the temperature, relative humidity and precipitation are lower, the moisture masses come from the Pacific Ocean. Winter precipitation is more depleted in heavy isotopes than summer precipitation. The isotopic analysis of precipitation, surface water and groundwater shows that recharge of the eastern subbasins of the SdA occurs by diffuse infiltration of precipitation and concentrated infiltration of surface water, both within the hydrographic basin of the SdA. The meteoric source of the waters in the Altiplano-Puna Plateau basins is isotopically lighter than the waters found in the side basins of the SdA, so there is no significant water quantity transfer to the peripheral aquifers of the SdA from outside the hydrographic basin.
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•In summer, the air comes from the North and South Atlantic and the Pacific Ocean.•In winter, all the air masses come from the Pacific Ocean.•Precipitation is more depleted in heavy isotopes in winter than in summer.•Recharge to peripheral aquifers originates within the hydrological basin.
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