Hydrogeological, hydrodynamic and anthropogenic factors affecting the spread of pharmaceuticals and pesticides in water resources of the Granada plain (Spain)

The anthropogenic organic contaminants contemplated in the environmental legislation, as well as those of emerging concern, threaten the quality of water resources to a degree that remains largely unknown. Contaminant exposure in the aquatic environment is a crucial element if a full understanding of the risk is pursued. There are still many uncertainties about the occurrence of organic pollutants and behavior in the hydro(geo)logical media in large scale areas. The case study of the unconfined aquifer of the Granada Plain (approximately 200 km2) is presented here. Two surface and groundwater monitoring campaigns were conducted (March 2017 and June 2018). In total, 41 out of 171 target organic pollutants were detected, at least once: 17 pharmaceuticals or drugs of abuse, 21 pesticides or their metabolites and three polyaromatic hydrocarbons. In addition, physico-chemical parameters were measured during the monitoring campaigns and hydrochemical parameters and stable isotopes (δ2H, δ18O, δ13C) were analyzed. Statistical tests confirmed the significance of seasonal changes for some of these parameters (e.g., EC, Cl-, F-, δ18O, δ13C), revealing the influence from snowmelt water input on streams and the intensification of irrigation. In March 2017, the group of pesticides (largely represented by triazines) predominated, whereas the frequency of detection of pharmaceuticals increased substantially in June 2018. Results suggest four main factors affecting the spatial and seasonal variation of organic pollutants in the aquifer: the anthropogenic factor determining the period of contaminant release throughout the year (pesticide application period and growth of tourism) along with irrigation practices that include reclaimed wastewater; unsaturated zone thickness; [...]This article is a contribution to the Research Groups RNM-308 and RNM 128 of the “Junta de Andalucía” and the project “Study, detection and behavior of emerging contaminants in anthropized watersheds in Andalusia-EMAN (P20_397)”. We are grateful to technical translation specialists GeoTranslations for proofreading the English version. We would also like to thank the Associate Editor, and the anonymous reviewers, who largely contributed to the improvement of the manuscript. Funding for open access charge: Universidad de Málaga / CBU

Climatic and geologic controls on the piezometry of the Querença-Silves karst aquifer, Algarve (Portugal)

Karst aquifers in semi-arid regions, like Queren double dagger a-Silves (Portugal), are particularly vulnerable to climate variability. For the first time in this region, the temporal structure of a groundwater-level time series (1985-2010) was explored using the continuous wavelet transform. The investigation focused on a set of four piezometers, two at each side of the S. Marcos-Quarteira fault, to demonstrate how each of the two sectors of the aquifer respond to climate-induced patterns. Singular spectral analysis applied to an extended set of piezometers enabled identification of several quasi-periodic modes of variability, with periods of 6.5, 4.3, 3.2 and 2.6 years, which can be explained by low-frequency climate patterns. The geologic forcing accounts for similar to 15 % of the differential variability between the eastern and western sectors of the aquifer. The western sector displays spatially homogenous piezometric variations, large memory effects and low-pass filtering characteristics, which are consistent with relatively large and uniform values of water storage capacity and transmissivity properties. In this sector, the 6.5-year mode of variability accounts for similar to 70 % of the total variance of the groundwater levels. The eastern sector shows larger spatial and temporal heterogeneity, is more reactive to short-term variations, and is less influenced by the low-frequency components related to climate patterns

New Insights on Betic Cordillera Structure From Gas Geochemistry

International audienceThe current lithospheric structure of the Betic Cordillera results from active geodynamic system related to slab retreat slowdown in western Mediterranean. A sharp change in lithospheric thickness has been imaged beneath the Betic Cordillera, potentially resulting from a near-vertical subduction-transform-edge-propagator fault toward the surface with possible mantle influx. In this study, we use helium isotopic composition of bubbling and dissolved gases in groundwater samples of the central part of the Betic Cordillera to evaluate the origin of gases and to set constraints on its lithospheric structure. We found that helium isotopic composition have a dominant radiogenic component with a mantle-derived He contribution reaching mainly 1% for the investigated area. Estimation of He diffusion within the ductile crust indicates that this process is potentially to slow to explain the low mantle-derived He contribution measured at the surface. A new analysis of the available data of the crustal metamorphic complexes allows us to suggest that the crust could be dissociated from the mantle with no evidence of asthenospheric influx. The weak mantle He signature could reflect a mantle material earlier incorporated in the crustal metamorphic complexes of the Betic Cordillera during their exhumation. In light of mass balance calculations, we propose that the slight 3 He excess observed in the present-day fluids might result from a fossil mantle signature diluted by local radiogenic production over time

A parsimonious distributed model for simulating transient water flow in a high-relief karst aquifer

A mathematical model of a highly heterogeneous functioning karst aquifer is described. The aquifer is in a high-relief karst massif and, as is common for such locations, data are scarce and there are no borehole, piezometer or pumping-test data. The scarcity of data in this case required a parsimonious approach to ensure that the level of complexity of the model was commensurate with the amount, type and quality of the available data. Parsimony also requires the model to include the minimum essential components that account adequately for the data, which in this and similar cases are the functional dualities of the karst system: duality in recharge, flow and discharge. The model is three-dimensional (3D) in the sense that the aquifer is discretized into 3D voxels, although the flow is one-dimensional (1D) and vertical in the vadose zone, and horizontal and two-dimensional (2D) in the saturated zone. The parsimonious model was designed by coupling a 1D unsaturated gravity-driven flow along the vertical (along each column of voxels that discretize the aquifer) and a 2D unconfined Darcy flow in the saturated zone. In the context of this type of aquifer, preferential recharge through the network of karst conduits implies a rapid rise in the water table, the location and extension of which are model parameters. The karst springs are simulated by drains. The methodology, which is completely general, is illustrated by application to the karst aquifer in the Sierra de las Nieves mountains in southern Spain.Eulogio Pardo-Igúzquiza, Peter Dowd, Antonio Pulido Bosch, Juan A. Luque-Espinar, Javier Heredia, Juan J. Durán-Valser

Role of CO2 in low to medium enthalpy geothermal systems in the Central Betic Cordillera (Spain)

International audienceThere is growing interest in geothermal energy, which is considered as an efficient energy solution to mitigate rising atmospheric CO2. Besides known high enthalpy geothermal systems, increasing attention is paid to low temperature geothermal systems, as they are suitable for local use. Although geothermal production seems to be an environmentally advantageous renewable energy, it might result in significant CO2 emissions. In this study, we investigate the relationship between temperature, fugacity of CO2 (fCO2), and mineral buffers in the reservoir conditions, taking the low- to medium- enthalpy thermal waters in the Central Betic Cordillera as case study. Using geochemical modeling, three main groups of waters have been identified depending on temperature, buffering mineral assemblage, and fCO2 in their reservoir. A group of waters with a reservoir temperature ranging from 70 to 90 °C and located in the intramountain sedimentary basins shows a fCO2 in depth ranging from ~6 × 10−2 and 6 × 10−1. The reservoir chemistry of this water group seems to be mainly controlled by carbonates and evaporites displaying a fCO2 variation between depth and surface (ΔfCO2) of 10−1. Another intermediate group of waters, located in an active extension zone, displays lower temperature (50–60 °C) and fCO2 in the reservoir (from 10−3 to 10−2). Finally, the third group of waters, located on the metamorphic complexes contacts, show the highest estimated temperatures (130–140 °C) and fCO2 in the reservoir (1 to 102). The two latter groups suggest increasing buffering effect of alumino-silicates, in addition to carbonates and quartz. Therefore, we evidenced a strong relationship between temperature and fCO2 in the reservoir as well as the potential mineral buffers. We discussed the potential of geothermal systems as clean energy source based on the estimation of the CO2 emissions generated by the investigated thermal systems for a practical case of household heating

Feature selection approaches for predictive modelling of groundwater nitrate pollution: An evaluation of filters, embedded and wrapper methods

Recognising the various sources of nitrate pollution and understanding system dynamics are fundamental to tackle groundwater quality problems. A comprehensive GIS database of twenty parameters regarding hydrogeological and hydrological features and driving forces were used as inputs for predictive models of nitrate pollution. Additionally, key variables extracted from remotely sensed Normalised Difference Vegetation Index time-series (NDVI) were included in database to provide indications of agroecosystem dynamics. Many approaches can be used to evaluate feature importance related to groundwater pollution caused by nitrates. Filters, wrappers and embedded methods are used to rank feature importance according to the probability of occurrence of nitrates above a threshold value in groundwater. Machine learning algorithms (MLA) such as Classification and Regression Trees (CART), Random Forest (RF) and Support Vector Machines (SVM) are used as wrappers considering four different sequential search approaches: the sequential backward selection (SBS), the sequential forward selection (SFS), the sequential forward floating selection (SFFS) and sequential backward floating selection (SBFS). Feature importance obtained from RF and CART was used as an embedded approach. RF with SFFS had the best performance (mmce = 0.12 and AUC = 0.92) and good interpretability, where three features related to groundwater polluted areas were selected: i) industries and facilities rating according to their production capacity and total nitrogen emissions to water within a 3 km buffer, ii) livestock farms rating by manure production within a 5 km buffer and, iii) cumulated NDVI for the post-maximum month, being used as a proxy of vegetation productivity and crop yield.</p

A parsimonious distributed model for simulating transient water flow in a high-relief karst aquifer

A mathematical model of a highly heterogeneous functioning karst aquifer is described. The aquifer is in a high-relief karst massif and, as is common for such locations, data are scarce and there are no borehole, piezometer or pumping-test data. The scarcity of data in this case required a parsimonious approach to ensure that the level of complexity of the model was commensurate with the amount, type and quality of the available data. Parsimony also requires the model to include the minimum essential components that account adequately for the data, which in this and similar cases are the functional dualities of the karst system: duality in recharge, flow and discharge. The model is three-dimensional (3D) in the sense that the aquifer is discretized into 3D voxels, although the flow is one-dimensional (1D) and vertical in the vadose zone, and horizontal and two-dimensional (2D) in the saturated zone. The parsimonious model was designed by coupling a 1D unsaturated gravity-driven flow along the vertical (along each column of voxels that discretize the aquifer) and a 2D unconfined Darcy flow in the saturated zone. In the context of this type of aquifer, preferential recharge through the network of karst conduits implies a rapid rise in the water table, the location and extension of which are model parameters. The karst springs are simulated by drains. The methodology, which is completely general, is illustrated by application to the karst aquifer in the Sierra de las Nieves mountains in southern Spain

Epikarst mapping by remote sensing

Epikarst – the shallow, surficial part of a karstic massif – has a significant influence on the spatio-temporal variability of recharge and the hydrodynamic functioning of many karst aquifers. In the Mediterranean morphoclimatic zone, the average thickness of a well-developed epikarst is around ten metres, but the spatial patterns of its degree of development are very heterogeneous due to the complex interaction of a number of different factors such as lithology, fracturing, weathering, soil and vegetation. In addition, direct field observation is difficult because good outcropping conditions are restricted to particular locations, some areas are not accessible and the size of the study area is often too large for exhaustive field surveys. Satellite-based remote sensing, however, provides a complete coverage of an entire area with spectral resolutions that detect variability in features that can define image textures related to the development of the epikarst. This paper describes a quantitative methodology for epikarst mapping using satellite images and field data. The proposed method comprises an unsupervised classification to define the spectral signature of each of three epikarst development categories in a high-resolution satellite image followed by a supervised classification of the terrain into one of the three categories on a low spatial resolution scale. The training areas in the field are assigned to the three categories by a panel of experts using the Delphi method. Geophysical data are used for validation to overcome any bias that may be introduced by the panel. The proposed methodology has been applied to the Sierra de las Nieves karstic aquifer (Málaga, southern Spain). The outcome is a map of estimated epikarst development that is an approximation to reality and which can be improved as more experimental data become available.Eulogio Pardo-Igúzquiza, Peter A. Dowd, Ana Ruiz-Constán, Sergio Martos-Rosillo, Juan A. Luque-Espinar, Víctor Rodríguez-Galiano, Antonio Pedrer

Identifying non-stationary groundwater level response to North Atlantic ocean- atmosphere teleconnection patterns using wavelet coherence

The first comprehensive use of wavelet methods to identify non-stationary time- frequency relations between North Atlantic ocean-atmosphere teleconnection patterns and groundwater levels is described. Long-term hydrogeological time series from three boreholes within different aquifers across the UK are analysed to identify statistically significant wavelet coherence between the North Atlantic Oscillation, East Atlantic pattern, and the Scandinavia pattern and monthly groundwater-level time series. Wavelet coherence measures the cross- correlation of two time series as a function of frequency, and can be interpreted as a correlation coefficient value. Results not only indicate that there are common statistically significant periods of multiannual-to-decadal wavelet coherence between the three teleconnection indices and groundwater levels in each of the boreholes, but they also show that there are periods when groundwater levels at individual boreholes show distinctly different patterns of significant wavelet coherence with respect to the teleconnection indices. The analyses presented demonstrate the value of wave- let methods in identifying the synchronization of groundwater-level dynamics by non-stationary climate variability on time scales that range from interannual to decada

Assessment of chloride natural background levels by applying statistical approaches. Analyses of European coastal aquifers in different environments

ABSTRACT: Estimated natural background levels (NBLs) are needed to assess groundwater chemical status according to the EU Groundwater Directive. They are commonly derived for different substances by applying statistical methodologies. Due to the complexity of the sea water intrusion process, some of those methods do not always provide appropriate assessment of chloride NBLs. This paper analyzes the applicability of different NBL estimation methods in five EU coastal aquifers with significant differences in available datasets and hydrogeological set-tings. A sensitivity analysis of results to different constraints was performed to remove samples with anthro-pogenic impacts. A novel statistical approach combining different methods to identify the range of chloride NBLs is proposed. In all pilots the estimated NBLs were below 85 mg/L and fitted well with previous studies and expert judgment, except Campina del Faro aquifer (the maximum being 167.5 mg/L). Although this approach is more time consuming, it provides a more robust solution.info:eu-repo/semantics/publishedVersio