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Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG [Abstract:] We have designed and built a versatile testing device to perform hydraulic fracturing experiments under true triaxial conditions. The device, based on a stiff biaxial frame that can be installed in a servocontrolled press, can accommodate cube rock samples of up to 150 mm-edge. Using a low-permeability rock known as Blanco Mera granite, we have performed a series of tests across a range of confining pressures including hydrostatic, normal, and strike-slip regimes. We have verified the applicability of two simple fracture mechanics-based models for the interpretation of experimental results, and we have determined the value of tensile strength of the rock from the injection curves recorded. The orientation of the hydraulically-triggered fractures with respect to the applied stress has also been analyzed. Although the models proposed by Rummel and Abou-Sayed provided reasonably satisfactory results, especially for hydrostatic and strike-slip tests, the presence of heterogeneities and defects in the rock matrix may have a strong influence on the fracture behavior and, therefore, affect the interpretation of hydrofracturing tests. This work was funded by REPSOL S.A. and the support of the Spanish Ministry of Science and Innovation (PID2021-126419NB-I00). A. Muñoz-Ibáñez also acknowledges the Margarita Salas grant from the Spanish Ministry of Universities, funded by the European Union – Next Generation EU. Funding for open access charge: Universidade da Coruña/CISUG.

Mode I fracture toughness (KIC) quantifies the ability of a material to withstand crack initiation and propagation due to tensile loads. The International Society for Rock Mechanics (ISRM) has proposed four suggested methods for determining KIC. However, these methods present some drawbacks such as insufficient post-peak control, complex sample preparation and considerable material requirements. Here we present an alternative approach, called the pseudo-compact tension (pCT) method, to measure KIC in rocks using disc-shaped specimens loaded in pure tension. The pCT specimen has favourable features such as a simple geometry, small sample volume and minimal machining requirement. The tensile load is transmitted to the specimen through two high-strength, high-stiffness steel jaws that fit into a U-shaped groove cut in the specimen. An additional thin straight notch is introduced to act as a stress concentrator. The crack propagates from the notch tip along the ligament plane, splitting the specimen into two halves. The effects of specimen size and notch length on KIC are determined by testing specimens 100, 50 and 38 mm in diameter with different notch length ratios (0.1 ≤ a/b ≤ 0.4). Tests were performed under ambient conditions and a slow loading rate (0.1 mm/min). Our results show that the pCT method is convenient for the assessment of KIC of both fragile and ductile rocks. The method offers good control even beyond the maximum load, making it possible to study the post-peak behaviour of the material.

The safety of groundwater has been a great concern for irrigation and drinking purposes in recent decades due to the increasing impacts of anthropogenic activities. There are several standards to evaluate the groundwater quality for different utilization purposes. In this paper, 804 samples covering the entire Ordos Basin across five provinces were used to evaluate the irrigation suitability and human health risks. The results showed that the sequence of cationic concentration was Na+ > Ca2+ > Mg2+ > K+ > NH4 +, and the anion concentration was HCO3 − > SO4 2− > Cl− > NO3 − > F− > NO2 −. For drinking purposes, TDS, Na+, SO4 2−, F−, TH and NO3 − exceed seriously the regulated standard in the study area. For irrigating purposes, 80% of the water in the study area belongs to “good water” according to the evaluation of salinity and alkalinity. Saline water which is not suitable for irrigation accounts for about 9%. High health risks of fluoride ions are mainly observed to the samples representing the western part of the study area, while the health risks of nitrates spread throughout the study area. Health risk is not only related to location, but also varies with age, and it is found that children suffer more threats than adults.

Antimony (Sb) contamination in soil has become a major environmental issue due to its adverse effects on ecosystems and human health. In this paper, 1255 soil samples were analyzed to investigate the distribution, speciation, in vitro oral bioaccessibility (8 soil samples) and human health risk of Sb in contaminated soils and its impacts on groundwater. The results showed that 4.38 % of the soil samples within the depth of 0-31 m exceeded the Risk Screening Values (RSV). Sb mainly existed in the residual fraction (38.05 % ∼ 94.22 %), Fe/Mn oxides (0.01 % ∼ 31.80 %) and the organic fraction (0.32 % ∼ 21.55 %) with poor mobility. The bioaccessibility of Sb was approximately31 %. The total concentration of Sb (TSb) in soil was the dominant factor influencing the bioaccessible concentration of Sb (Sb

Toxic heavy metals pollution in urban soil has become a major global issue due to its adverse effects on the environment and human health. In this paper, 26 soil samples were analyzed to assess the speciation, bioavailability and human health risk of Arsenic (As), Mercury (Hg), Lead (Pb) and Cadmium (Cd) in urban soils of a heavy industrial city in NE China by using a Monte Carlo simulation approach. The results showed that As, Hg, Pb and Cd concentrations in the soil all exceed the corresponding background value of study area. Mercury displays the highest value of geo-accumulation index (Igeo), followed by Cd, Pb and As. The pollution load index (PLI) value (2) indicates a moderate pollution level in the study area. The chemical speciation of HMs mainly exists in residual fraction except Cd. The probabilistic health risk assessment demonstrated that the mean values of Total Carcinogenic Risk (TCR) and Hazard Index (HI) calculated with total concentration are at the unacceptable level, with a higher risk to children than adults. However, the mean values calculated with bioavailable fraction are all within the acceptable level. The mean value of TCR and HI obtained by bioavailable fraction is about 96% and 95% lower than that obtained by total concentration, respectively. Thus, this study suggested that the bioavailable fraction of HMs is a more reliable parameter for health risk assessment, while the total concentration of HMs can overestimate the true risk. The results of this study provide some insight into the speciation, bioavailability and health risks of toxic heavy metals in urban soils in those heavy industrial cities.

Groundwater resources are increasingly exploited for industrial and agricultural purposes in many arid/semi-arid regions globally. In order to gain a harmonious development among groundwater resources and economic benefits, urgent investigation of the impacts of anthropogenic activities on the groundwater chemistry is required. Understanding hydrochemical mechanism of groundwater in Yinchuan Plain, arid and semi-arid area in Northwestern China, plays a significant role in water resources planning in this ecologically sensitive area. In this paper, a total of 460 phreatic water samples were collected, including 58 water samples containing isotopic data (D and 2 H). Results demonstrate that water chemistry type and isotopic data of phreatic water presents a zonation characteristic from west to east and from south to north. In the eastern part of the Helan Mountain (A 1 zone), the type of hydrochemistry is mainly HCO 3 ·SO 4 -Ca·Mg, SO 4 ·HCO 3 -Ca·Mg, which is mainly recharged by the bedrock fissure water of Helan Mountain. However, in the southern Qingtongxia (A 2 zone) are HCO 3 -Na HCO 3 -Ca·Mg, which receives irrigation and spring water recharge. Phreatic aquifer in Multi-layered structure zone (A 3 zone) reflect multiple recharge sources to the aquifer, the water chemistry demonstrates diverse variations. The anion was dominated by the HCO 3 , while the cation is dominated by sodium. The predominant controlling factors of phreatic water hydrochemistry are divided into anthropogenic activities and natural conditions. Natural conditions mainly include the existence form and lithology of the aquifer, sources of groundwater recharge, soil salinity, and evaporation, mineral dissolution, ion exchange and adsorption and mixing effect. Meanwhile, among natural factors, minerals dissolution in groundwater is the main process dominating the hydrochemical evolution of the groundwater. The other is anthropogenic activities which can be classified as groundwater pollution, excessive exploitation or excretion of groundwater, and excessive groundwater recharge.

precipitation and evaporation are two vital components of water cycle, and Hydrogen and oxygen stable isotopes are important tracers in water, which are very sensitive to changes in the climate and the water cycle. Rayleigh Fractionation equation is usually applied to calculate isotope distributions in order to quantify the precipitation and evaporation processes. It is reasonable to explain the evaporation process using the Rayleigh fractionation equation. However, the composition of hydrogen and oxygen stable isotopes in the precipitation will change due to the effects of dynamic fractionation and dilution during raindrop fall. In this case, it is not feasible to rely entirely on the Rayleigh fractionation equation. In this paper, atmospheric precipitation isotopes data recorded during 1996–2016 in Hong Kong from the Global Network of Isotopes in Precipitation (GNIP) are analyzed, including local meteoric water line (LMWL), deuterium-excess (d), temperature effect and rainfall amount effect. The results indicate that precipitation is affected by secondary evaporation and dilution effects. In addition, the stable isotope composition in precipitation is the result of temperature and precipitation. Due to the effects of these two effects, changes of isotope composition in precipitation are not always consistent. When the rainfall density is very large, the temperature effect is covered up and the temperature is inversely related to the isotope composition of precipitation. In contrast, when the rainfall density is small, the temperature is positively related to the isotope composition of precipitation. Therefore, it is suggested to consider the rainfall density while studying the relationship between the isotope composition of precipitation and the local climate. These finds can provide some enlightenments and references on how to investigate the changing pattern of isotope composition in precipitation.

Regional sustainable development is a critical requirement for natural resources management and socio-economic sustainability, in which water resource is one of the most important supports. The present study proposed a method to calculate water resources carrying capacity (WRCC) and water environmental carrying capacity (WECC) to assess the scale of economy and population that the local water resources can support in Yinchuan City, a semi-arid area in Northwest China. Carrying population and gross domestic product (GDP) were selected as the characteristic indices of carrying capacity. The urban water demand and supply data were used to calculate the WRCC, NH3–N and chemical oxygen demand with K2Cr2O7 as the oxidizing agent (CODCr) were used to calculate the WECC. Carrying index was employed to assess the carrying status and risk of water resources and environment in 2010, 2015 and 2020, respectively. The results show that the environmental capacity of Yinchuan in terms of NH3–N in different years ...

The authors acknowledge COST Action ES 1105 "CYANOCOST Cyanobacterial blooms and toxins in water resources: Occurrence impacts and management" and COST Action Global Change Biology ES 1201 NETLAKE -Networking Lake Observatories in Europe" for contributing to this study through networking and knowledge sharing with European experts in the field. We acknowledge the members of the Global Lake Ecological Observatory Network (GLEON) for their collaborative spirit and enthusiasm that inspired the grassroots effort of the EMLS. E.M. was supported by a grant from the Swiss State Secretariat for Education, Research and Innovation to Bas Ibelings and by supplementary funding from University of Geneva. We thank Wendy Beekman for the nutrient analysis. We thank Pieter Slot for assisting with the pigment analysis. We thank Dr. Ian Jones for valuable feedback on an earlier version of the manuscript. We thank the Leibniz Institute of Freshwater Ecology and the Aquatic Microbial Ecology Group for logistic and technical support of J. Fonvielle and H.-P. Grossart, and the Leibniz Association for financial support. H.P. was supported by the US National Science Foundation (1840715, 1831096). A.C.'s work was funded by the Spanish Agencia Estatal de Investigacion and EU funds through the project CLIMAWET (CGL2015-69557-R). The collection of data for Lough Erne and Lough Neagh were funded by the Department of Agriculture, Environment and Rural Affairs, Northern Ireland. We are grateful to Kristiina Vuorio from the Freshwater Centre of the Finnish Environment institute for her help in organizing, collecting and analysing samples by the University of Jyvaskyla and to Gerald Dorflinger from the Water Development Department of Cyprus for his assistance with the sampling in Cyprus and for granting the CUT team permission to use WDD's equipment. Finally, we would like to thank the numerous other assistants that helped realizing each local survey. Open access funding provided by Universite de Geneve., To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L-1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a (Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl a than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4 degrees C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient-rich lakes than nutrient concentrations and surface temperature., European Cooperation in Science and Technology (COST) ES 1105 ES 1201, Swiss State Secretariat for Education, Research and Innovation, University of Geneva, Leibniz Association, National Science Foundation (NSF) 1840715 1831096, Spanish Agencia Estatal de Investigacion, European Commission CGL2015-69557-R, Department of Agriculture, Environment and Rural Affairs, Northern Ireland

Slates are metamorphic rocks characterized by the pervasive occurrence of cleavage or foliation producing a highly anisotropic mechanical behavior characterized by fissility. Deformability and strength of these rocks are therefore dependent on the cleavage plane orientations relative to the principal stresses. In this study, the failure and deformability of these rocks are experimentally investigated by means of a set of standard uniaxial and triaxial compression tests on samples cut with the cleavage forming different angles. Propagation velocity measurements have also been taken in a good number of specimens. Compression tests show that deformability and strength are clearly anisotropic for this rock and that failure through the cleavage plane is observed in the range of dip angles from 15 to 75°. Transversely isotropic elastic parameters are fit based on improved existing approaches. Moreover, the strength of tested samples cut normal and parallel to foliation relevantly differ, something noted qualitatively in the past by some authors in some metamorphic anisotropic rocks. However, this difference has neither been explicitly reported for the case of other foliated sedimentary rocks such as shales, nor formalized in theoretical strength approaches. The triaxial compression experimental data on slates were fit with the Jaeger's plane of weakness (JPW) model. Strength criteria differentiating the strength in directions normal and parallel to foliation are proposed to adapt the JPW model to the observations in slate strength behavior. Other model improvement is proposed, the use of a non-linear strength criterion for the intact rock (Hoek-Brown), which shows to better represent observed strength laboratory results. The experimental part of this work was funded by REPSOL S.A. The three first authors acknowledge the Spanish Ministry of Universities for funding of the project, awarded under Contract Reference No. RTI2018-093563-B-I00, partially financed by means of ERDF funds from the EU, which permitted to complete the interpretative part of this study. The fourth author acknowledges the CSC scholarship (No. 201706260240) for financing his stay at the University of Vigo, where he was involved in part of this work. Funding for open access charge: Universidade de Vigo/CISUG.

This article belongs to the Special Issue She Maps (https://www.mdpi.com/journal/remotesensing/special_issues/shemaps) [Abstract] A multi-sensor and multi-scale monitoring tool for the spatially explicit and periodic monitoring of eutrophication in a small drinking water reservoir is presented. The tool was built with freely available satellite and in situ data combined with Unmanned Aerial Vehicle (UAV)-based technology. The goal is to evaluate the performance of a multi-platform approach for the trophic state monitoring with images obtained with MultiSpectral Sensors on board satellites Sentinel 2 (S2A and S2B), Landsat 8 (L8) and UAV. We assessed the performance of three different sensors (MultiSpectral Instrument (MSI), Operational Land Imager (OLI) and Rededge Micasense) for retrieving the pigment chlorophyll-a (chl-a), as a quantitative descriptor of phytoplankton biomass and trophic level. The study was conducted in a waterbody affected by cyanobacterial blooms, one of the most important eutrophication-derived risks for human health. Different empirical models and band indices were evaluated. Spectral band combinations using red and near-infrared (NIR) bands were the most suitable for retrieving chl-a concentration (especially 2 band algorithm (2BDA), the Surface Algal Bloom Index (SABI) and 3 band algorithm (3BDA)) even though blue and green bands were useful to classify UAV images into two chl-a ranges. The results show a moderately good agreement among the three sensors at different spatial resolutions (10 m., 30 m. and 8 cm.), indicating a high potential for the development of a multi-platform and multi-sensor approach for the eutrophication monitoring of small reservoirs. This research was co-funded by the Spanish Ministry of Research, Innovation and Universities through the Torres Quevedo Sub-Program, grant number PTQ-15-07685 https://www.mdpi.com/journal/remotesensing/special_issues/shemaps

Granular materials submitted to uniaxial compression undergo pore space reduction due to mechanisms such as particle rearrangement and grain crushing. These changes in the internal structure of the material release energy in the form of elastic waves that can be detected by sensors sensitive to acoustic emission. In this study, Acoustic emission monitoring with a wavelet‐based signal processing technique is used to identify the various mechanisms occurring during high‐pressure sand compaction. Particle movement, grain failure, friction between grains and the surface of the compression cell and intergranular friction are studied. Acoustic emission data recorded during these simplified tests are used to characterize each phenomenon. Wavelet transform analyses allow the identification of useful features, making possible frequency discrimination among sliding, rolling, friction and grain fragmentation processes. For instance, we observe that at low stress, grain flow is characterized by the lowest centroid and peak frequencies, while at greater stresses, intergranular friction and grain fragmentation have the higher values. In the tests performed, the stress–strain evolution and final condition of the tested sand are broadly consistent, irrespective of the condition employed: continuous, stepwise or even variable loading rate or temperature. However, Acoustic emission data manifest much more complex behaviour (including thermal, load‐rate dependency and delayed fragmentation phenomena) than that suggested by stress–strain relationships. At low stress levels, grain flow (sliding/rolling) is a relevant strain‐accommodation mechanism, but so is crushing due to the effect of concentrated forces at the grain contact level. At high stresses, when crushing is generalized, intergranular friction is also a relevant phenomenon due to the increase in the coordination number produced by previous fragmentation.

A series of mode I fracture toughness tests employing the semi-circular bend (SCB) and the pseudo-compact tension (pCT) methodologies have been performed with two sandstone types and specimens of 50 and 100 mm in diameter. The tests were complemented with the concurrent monitoring of acoustic emission (AE) activity using a multi-sensor array. With the obtained data, we compare and analyse the two testing methods, the mechanical evolution along experiments and the significance of different acoustic emission parameters. The hypocenter location of the AE events allows a better understanding of the processes occurring in the tests and the analysis of properties like amplitude or peak frequencies are valuable complements. Crack modes are assessed using a parameter-based strategy (comparison of the average frequency, AF, and rise angle, RA), and the potential of the Ib-value to discriminate cracking processes in fracture toughness tests is explored. Results show that the pCT method provides more comprehensive and detailed results, both in terms of mechanical information and acoustic emission data. We discuss the applicability of the generally accepted models of small-strain brittle material failure typically applied to compressive tests (including or not including AE data) and further methodological questions of interest when considering AE monitoring in fracture toughness tests.

The pseudo-compact tension (pCT) method recently proposed by Muñoz-Ibáñez et al. (2020) is a satisfactory approach to measure mode I fracture toughness (KIC) in rocks and other materials using disc-shaped samples loaded under pure tensile conditions. In contrast to other methods, such as the semi-circular bend (SCB) suggested by the ISRM (2014), the pCT test provides with good control after peak load, making it possible to further characterize the processes involved in fracture propagation. In this work we assess the influence of the testing configuration at the onset of unstable crack propagation. In order to extend the pCT concept to complementary geometries with potential interest we studied an alternative to the SCB specimen, which we call pseudo-SCB (pSCB). To compute KIC in this configuration we have derived the corresponding dimensionless stress intensity factor function (Y’) based on the finite element method. The results show that the pSCB test provides with consistent values of KIC and it also allows to control the propagation of the crack beyond peak load, which reinforces the idea that the loading conditions may be a more determinant factor than the sample geometry in controlling post-peak behaviour. In addition, an expression of Y’ is presented for cubic samples tested using the pCT approach. This configuration may be useful for testing other materials amenable of moulding such as mortar, concrete, ceramics, etc.

We present a series of tests performed on granite samples using a true triaxial device designed and built at the Rock Mechanics Laboratory (University of A Coruña). The experiments were performed using cubic rock samples of 150 mm-edge, which were loaded to different stress conditions (σh < σh < σy < 45 MPa) on each loading axis. The device is based on a stiff steel frame that can be coupled to a servo-hydraulic testing machine that provides de vertical stress (av), while two high-pressure pumps are used to deliver the lateral stress (σh and ah). An additional high-pressure pump is used to inject the fluid (mineral oil) into the rock sample at a low constant-flow rate. The aluminium loading platens, which are bevelled at the edges to avoid interaction among adjacent faces, have holes and grooves to introduce acoustic emission sensors that allow the location of fracture propagation. The specimens were drilled using a 6 mm drill bit until reaching the geometrical centre. Then, a 1/8” (~3.18 mm) stainless steel tube is glued to the samples with epoxy. Strain measurements during the experiments were conducted using four strain gages attached to the orthogonal faces of the specimens. The system was further equipped with three LVDTs to account for the bulk displacement on each axis. Our results suggest a linear relationship between the breakdown pressure and the confining stress under hydrostatic conditions but no clear correlation in non-hydrostatic stress regime.

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG [Abstract] Mode I fracture toughness (KIC) is an intrinsic material property that quantifies its resistance to tensile fracture propagation. The International Society for Rock Mechanics has endorsed four methods to determine the KIC of rock, namely, the short rod, chevron bend, cracked chevron notched Brazilian disc, and semi-circular bend (SCB) methods. In this study, we compare the results of the SCB technique with those of the recently proposed pseudo-compact tension (pCT) test, which has proven to be convenient for the assessment of KIC in both fragile and ductile rocks. We select the SCB as a benchmark method due to its popularity, simplicity, and straightforward testing configuration. We discuss the results of 146 tests performed with different lithologies (Arcera, Pinacas and Corvio sandstones, and Blanco Mera granite), different sample sizes (100, 50 and 38 mm diameter), and a range of notch lengths. We also assess test repeatability and intercomparability of the results obtained using the two techniques. Compared with the SCB test, the pCT test allows for improved control of the specimen behaviour after the peak load, which provides a greater wealth of fracture mechanics information. pCT specimens yield results with higher repeatability than SCB samples. Although we observe that KIC tends to decrease with an increase in the notch length ratio, this effect appears to be non-significant based on statistical assessments. Accordingly, the corresponding mean KIC values are comparable for medium- and large specimens. The influence of specimen size is more pronounced in the SCB tests, while the pCT tests show less dependence for harder lithologies. Therefore, to set up minimum specimen requirements for fracture toughness testing, in addition to geometrical constraints, some key lithology-dependent properties (strength, mineralogy, grain size, etc.) should also be considered. Further methodological considerations related to test execution are also discussed. This work was funded by Repsol S.A. and supported by the Xunta de Galicia, the European Union (European Social Fund - ESF) and the MINECO/AEI/FEDER EU project BIA2017-87066-R. Funding for open access charge: Universidade da Coruña/CISUG.

Insufficient understanding of the hydrogeochemistry of aquifers makes it necessary to conduct a preliminary water quality assessment in the southern region of Ordos Basin, an arid area in the world. In this paper, the major ions of groundwater have been studied aiming at evaluating the hydrogeochemical processes that probably affect the groundwater quality using 150 samples collected in 2015. The two prevalent hydrochemical facies, HCO3Mg·Na·Ca and HCO3Mg·Ca·Na type water, have been identified based on the hydrochemical analysis from Piper trilinear diagram. Compositional relations have been used to assess the origin of solutes and confirm the predominant hydrogeochemical processes responsible for the various ions in the groundwater. The results show that the ions are derived from leaching effect, evaporation and condensation, cation exchange, mixing effect and human activities. Finally groundwater quality was assessed with single factor and set pair methods, the results indicate that groundwater quality in the study region is generally poor in terms of standard of national groundwater quality. The results obtained in this study will be useful to understand the groundwater quality status for effective management and utilization of the groundwater resource.

We present a comprehensive characterisation of the physical, mineralogical, geomechanical, geophysical, and hydrodynamic properties of Corvio sandstone. This information, together with a detailed assessment of anisotropy, is needed to establish Corvio sandstone as a useful laboratory rock-testing standard for well-constrained studies of thermo–hydro–mechanical–chemical coupled phenomena associated with CO2 storage practices and for geological reservoir studies in general. More than 200 core plugs of Corvio sandstone (38.1 and 50 mm diameters, 2:1 length-to-diameter ratio) were used in this characterisation study, with a rock porosity of 21.7 ± 1.2%, dry density 2036 ± 32 kg m?3, and unconfined compressive and tensile strengths of 41 ± 3.28 and 2.3 ± 0.14 MPa, respectively. Geomechanical tests show that the rock behaves elastically between ?10 and ?18 MPa under unconfined conditions with associated Young's modulus and Poisson's ratio of 11.8 ± 2.8 GPa and 0.34 ± 0.01 GPa, respectively. Permeability abruptly decreases with confining pressure up to ?10 MPa and then stabilises at ?1 mD. Ultrasonic P- and S-wave velocities vary from about 2.8–3.8 km s?1 and 1.5–2.4 km s?1, respectively, over confining and differential pressures between 0.1 and 35 MPa, allowing derivation of associated dynamic elastic moduli. Anisotropy was investigated using oriented core plugs for electrical resistivity, elastic wave velocity and attenuation, permeability, and tracer injection tests. Corvio sandstone shows weak transverse isotropy (symmetry axis normal to bedding) of

Groundwater is a prominent resource of drinking and domestic water in the world. In this context, a feasible water resources management plan necessitates acceptable predictions of groundwater table depth fluctuations, which can help ensure the sustainable use of a watershed’s aquifers for urban and rural water supply. Due to the difficulties of identifying non-linear model structure and estimating the associated parameters, in this study radial basis function neural network (RBFNN) and GM (1, 1) models are used for the prediction of monthly groundwater level fluctuations in the city of Longyan, Fujian Province (South China). The monthly groundwater level data monitored from January 2003 to December 2011 are used in both models. The error criteria are estimated using the coefficient of determination (R 2), mean absolute error (E) and root mean squared error (RMSE). The results show that both the models can forecast the groundwater level with fairly high accuracy, but the RBFN network model can be a promising tool to simulate and forecast groundwater level since it has a relatively smaller RMSE and MAE.

Ordos Basin is located in an arid and semi-arid region of northwestern China, which is the most important energy source bases in China. Salawusu Formation (Q3 s) is one of the most important aquifer systems of Ordos Basin, which is adjacent to Jurassic coalfield areas. A large-scale exploitation of Jurassic coal resources over ten years results in series of influences to the coal minerals, such as exposed to the oxidation process and dissolution into the groundwater due to the precipitation infiltration. Therefore, how these processes impact groundwater quality is of great concerns. In this paper, the descriptive statistical method, Piper trilinear diagram, ratios of major ions and canonical correspondence analysis are employed to investigate the hydrochemical evolution, determine the possible sources of pollution processes, and assess the controls on groundwater compositions using the monitored data in 2004 and 2014 (before and after large-scale coal mining). Results showed that long-term exploration of coal resources do not result in serious groundwater pollution. The hydrochemical types changed from HCO 3 − - CO 3 2 − facies to SO 4 2 − -Cl facies during 10 years. Groundwater hardness, nitrate and sulfate pollution were identified in 2014, which was most likely caused by agricultural activities.

Groundwater quality relating closely to human health has become a great concern to the whole society, especially in heavily polluted areas. Yinchuan Plain, located in the arid and semi-arid region of Northwestern China, where people rely heavily on groundwater resource. However, due to the improper groundwater exploitation and negative effect of human activities in recent years, groundwater quality in Yinchuan plain become deteriorated. For the sustainable utilization and protection of groundwater resources, health risk assessment (HRA) of phreatic water is conducted in this paper. On the basis of model recommended by EPA, triangular fuzzy number is applied to establish risk assessment model for health risk assessment of adults and children in wet and dry seasons, respectively. Results of HRA indicate that carcinogenic risk of arsenic is highest among the risk from components in phreatic water, and the highest risk from arsenic to adults and children in wet and dry season are 6.48 × 10−6a−1 and 9.56 × 10−6a−1, 1.08 × 10−5a−1 and 1.59 × 10−5a−1, respectively. This study also states that in Yinchuan Plain carcinogenic risk from drinking groundwater can be 3–4 times magnitude higher than the noncarcinogenic risk. Also it is found that the health risk to children is as 1.5–2 times as to adults, while the uncertainties of adults’ health risk are higher than that of children.

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains. © 2018 by the authors. Licensee MDPI, Basel, Switzerland., The authors acknowledge COST Action ES 1105 “CYANOCOST—Cyanobacterial blooms and toxins in water resources: Occurrence impacts and management” and COST Action ES 1201 “NETLAKE—Networking Lake Observatories in Europe” for contributing to this study through networking and knowledge sharing with European experts in the field. Evanthia Mantzouki was supported by a grant from the Swiss State Secretariat for Education, Research and Innovation (SERI) to Bas Ibelings and by supplementary funding from the University of Geneva. We thank Clare Ahnlund, Ena Suarez and Irene Gallego for helping out with the Swiss survey. We thank Wendy Beekman and Els J. Faassen for the nutrient and toxin analysis.

Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The European Multi Lake Survey (EMLS) in summer 2015 was an initiative among scientists from 27 countries to collect and analyse lake physical, chemical and biological variables in a fully standardized manner. This database includes in-situ lake variables along with nutrient, pigment and cyanotoxin data of 369 lakes in Europe, which were centrally analysed in dedicated laboratories. Publishing the EMLS methods and dataset might inspire similar initiatives to study across large geographic areas that will contribute to better understanding lake responses in a changing environment., The authors acknowledge COST Action ES 1105 “CYANOCOST – Cyanobacterial blooms and toxins in water resources: Occurrence impacts and management” and COST Action ES 1201 “NETLAKE – Networking Lake Observatories in Europe” for contributing to this study through networking and knowledge sharing with European experts in the field. Evanthia Mantzouki was supported by a grant from the Swiss State Secretariat for Education, Research and Innovation (SERI) to Bas Ibelings and by supplementary funding from University of Geneva. We thank Wendy Beekman for the nutrient analysis and the University of Wageningen for covering the costs of this analysis from the personal funding of dr. Miquel Lürling. We thank Pieter Slot for assisting with the pigment analysis and the University of Amsterdam for covering the costs of the analysis through funding from the group of Prof. Jef Huisman and dr. Petra Visser (IBED). We would like to thank the Environmental Data Initiative for covering the cost of archiving the EMLS dataset. We would like to thank the Leibniz Institute of Freshwater Ecology and Inland Fisheries, Dept. of Experimental Limnology and the Aquatic Microbial Ecology Group for logistic and technical support of J. Fonvielle and H.-P. Grossart; and the Leibniz Association for financial support. The collection of data for Lough Erne and Lough Neagh were funded by the Department of Agriculture, Environment and Rural Affairs, Northern Ireland.

Accurate and reliable prediction of groundwater level is a critical component in coastal water management. It is important to find a suitable model with acceptable accuracy. This paper presents a comparative study with seasonal decomposition method of time series analysis and GM (1,1) method, which are applied to test the model accuracy by simulating groundwater levels of two representative wells located at a coastal aquifer in Fujian Province, South China. The average monthly groundwater level was monitored during 2006–2011, the data set from 2006–2010 was used for model establishment, and that of 2011 used for predicting the dynamic change of groundwater level. The results indicate that the multiplicative model fits better than the additive model for seasonal decomposition method. Finally, the effectiveness of the model and prediction accuracy was evaluated based on root mean square error (RMSE) and regression coefficient ( R2 ). From the obtained results, it is concluded that the GM (1,1) method can be a promising tool to simulate and forecast groundwater level and serve as an alternative physically based model.

Water quality models are important tools to test the effectiveness of alternative management plans on the water quality of water bodies. The main aim of this study was to develop and demonstrate use of a water quality model as a tool for evaluation of alternative water management scenarios for the river basin of Beijing, China. Considering Lao Hewan river landscape water circulation patterns and water quality protection programme, hydrodynamic module, structure operation module, advection/dispersion module and ECOlab module in the MIKE 11 model system, the circulating water drainage system and water quality model have been developed for water protection measures. Modelled results indicate the simulated biochemical oxygen demand, chemical oxygen demand, ammonia and total phosphorus concentration evolve in a general increasing trend for the first scenario since there are no water purification measures taken in this scenario; for the second scenario, the simulated water quality showed a slight decreasing trend in both sites, and better than that of scenario I due to considering the water circulation with a volume of 40,000 m 3 /d in both sites and the purification function of the wetlands of the Centre Lake. Simulated concentrations of pollutants in scenario III are lower than in scenarios I and II, due to the strengthened purification measures (horizontal subsurface flow wetland and surface flow wetland) implemented.

A column experiment has been performed in order to derive hydrodynamic data from pore water sampling using Rhizon soil moisture sampler (SMS) devices. The column was filled with dry granite fines (a fine grained material of well-known properties), saturated with tap water and the evolution of saturation was monitored with the aid of X-ray absorption scans. Once saturation was completed, seven equally-spaced Rhizon samplers were introduced in the column and a 4-stage sequential pore water extraction process conducted. For each Rhizon sampler, flow was carefully recorded in each stage and the data obtained has been interpreted considering the sampling device as being analog to a slotted-casing low-diameter piezometer and the extraction a bail-down type hydraulic test. A modified Hvorslev's and the Gilg-Gavard's methods have been used to assess the hydraulic conductivity during extractions. Experimental results, including unsaturated parameters based on the MVG model, show a good agreement with literature reported data for granite fines, at least up to a hydraulic conductivity of ~ 10− 8 m s− 1. Although further tests are needed to check the applicability of the methodology described to materials with different granulometry and/or with concentrated pore solutions the available results show that Rhizon samplers are good candidates for the hydrodynamic assessment of sediments.

Soil and water conservation ecological compensation can be simply defined as a monetary payment to offset the environmental loss. An illustration is given in this study describing the payment compensation to water resource conservation and soil losses in Erlongshan reservoir catchment, China. A semi-distributed hydrological SWAT model was applied to establish compensation standard considering six scenarios of land use changes by combined application of remote sensing and geographic information systems. Cost-benefit analysis (CBA) method is applied to evaluate the function of soil and water conservation, of which marginal opportunity cost and market value methods have been explored calculate the cost and benefit of water and soil conservation ecological function from provider and beneficiaries. Finally the ecological compensation of soil and water conservation for different land-use scenarios is calculated incorporating benefit apportion coefficient. The results provide an economically evaluated and market-oriented standard for the study of eco-compensation of environmental services and will be of great benefit to the implementation of soil and water conservation at a mesoscale catchment scale.

During the 1990s, groundwater overexploitation has resulted in seawater intrusion in the coastal aquifer of the Shenzhen city, China. Although water supply facilities have been improved and alleviated seawater intrusion in recent years, groundwater overexploitation is still of great concern in some local areas. In this work we present a three-dimensional density-dependent numerical model developed with the FEFLOW code, which is aimed at simulating the extent of seawater intrusion while including tidal effects and different groundwater pumping scenarios. Model calibration, using waterheads and reported chloride concentration, has been performed based on the data from 14 boreholes, which were monitored from May 2008 to December 2009. A fairly good fitness between the observed and computed values was obtained by a manual trial-and-error method. Model prediction has been carried out forward 3 years with the calibrated model taking into account high, medium and low tide levels and different groundwater exploitation schemes. The model results show that tide-induced seawater intrusion significantly affects the groundwater levels and concentrations near the estuarine of the Dasha river, which implies that an important hydraulic connection exists between this river and groundwater, even considering that some anti-seepage measures were taken in the river bed. Two pumping scenarios were considered in the calibrated model in order to predict the future changes in the water levels and chloride concentration. The numerical results reveal a decreased tendency of seawater intrusion if groundwater exploitation does not reach an upper bound of about 1.32 × 104 m3/d. The model results provide also insights for controlling seawater intrusion in such coastal aquifer systems.

Following the technical closure of the brown lignite Meirama mine (NW Spain) in April 2008, the reclamation of the mined area is being accomplished with the controlled flooding of its large pit. During the first 7 months of flooding, the sequential arrest of the ground water dewatering system led to the growth of an acidic water body of about 2 hm3. Since October 2008, the surface waters from some local streams have been diverted towards the pit so that these have become the major water input in the flooding process. Surface water has promoted a major change in the chemical composition of the lake water so that, at present, its surface has a circum neutral pH, net alkalinity, and low conductivity. At present, the lake has slightly more than one half of its final volume, and it is expected the overflow in 3 to 3.5 years. The lake is meromictic, with a sharp chemocline separating the acidic monimolimnion (pH≈3.2, acidity≈150 mg CaCO3/L, κ 25≈2.4 mS/cm) from the main water body (pH≈6.5, alkalinity≈15 mg CaCO3/L, κ 25≈0.3 mS/cm). Oxygen is being depleted at the bottom of the lake so that the monimolimnion became anoxic in January 2011. Above the chemocline, the composition of the lake is similar, but not identical, to that of the flooding stream waters. Close to the surface, some constituents (pH, metals) show strong seasonal variations in coincidence with the phytoplankton growing periods. Those parameters whose limits are legally prescribed comply with the corresponding water quality standards, and they are also consistent with the forecasting results obtained in early modeling. At present, a project considering the construction of an uptake tunnel to exploit the lake is being developed for the emergency water supply of the metropolitan area of A Coruña.

Two large-scale column experiments have been performed to test the hydrodynamic behaviour of unsaturated, compacted granite sawdust—a material produced during the dressing of dimension stone in Pontevedra (Spain). One of the columns was equipped with psychrometers and capacitance probes while, in the other, a radial array of 80 electrodes made possible a time-dependent 3D electrical resistivity survey. All these devices allowed investigating and modelling the progressive saturation of the material. The study includes a straightforward methodology developed to calibrate the resistivity signals based on standard Proctor-compacted specimens. The progressive saturation of the granite sawdust reveals different stages: initially, an uneven advance of the saturation front (fingering) occurs; later on, this feature vanishes and is replaced by a more regular advance of the saturation front. Numerical analysis of the results shows that the yield capacity of the granite sawdust is ~0.39 m3 m?3 and a saturated hydraulic conductivity ~2 × 10?6 m s?1. The latter, which corresponds to the specific standard Proctor compaction, is not sufficient to support the use of granite sawdust for compacted-single-layer capping structures. Nonetheless, increased compaction efforts or improved design criteria (multilayer systems or capillary barriers) can keep bearing when considering granite sawdust for this purpose.

Two well developed hedenbergitic, ilvaite-bearing skarns formed along the northern contact of the Maladeta batholith (Central Pyrenees, Spain) have been studied in order to determine their physico-chemical conditions of formation. The skarns formed at ~3 kbar total pressure following a classical two-stage (prograde/retrograde) evolution. Oxygen fugacity during skarn formation was buffered close to the NNO oxygen buffer while it is likely that sulfur fugacity remained nearly constant (10−8–10−10) throughout the second, retrograde stage. Fluid inclusions indicate that the hydrothermal fluid was a hypersaline brine (25–30 % NaCl eq.), sometimes halite-saturated at room temperature. Based on fluid inclusions and volatile speciation calculations, H2O was the dominating volatile while CO2 was present in low levels (X CO2 < 0.02). Thermodynamic data for ilvaite have been retrieved from published works and available experiments. These data have made possible the construction of several phase diagrams for the Ca-Fe-Si-O-H ± C system with which the stability of ilvaite with respect to a number of parameters is illustrated. The stability relationships render unlikely that ilvaite can form under pressures below 2 kbar and show that this mineral can only develop from fluids with low or very low CO2 content. With the exception of Mn, the presence of significant amounts of Al, Mg and other elements drastically reduces the stability field of ilvaite. Hence, this mineral should not be expected to occur in environments departing significantly from the 6-component system studied here.

The cutting operations of dimension stone at quarries produce a large amount of fines that, in turn, cause a negative environmental im- pact over local surface waters. This article presents a detailed analysis of the mobilized contamination associ- ated with runoff waters in a large granite quarry (� 200 ha) which is located in Porrino (Galicia, NW Spain), the most important produc- tion centre of dimension stone in Spain. There, an intensive monitor- ing survey was developed in order to characterize the hydrology of the system as well as the release and transport of pollutants. This was accomplished by means of different control sections for the flow and by the collection of 52 random water samples. Automatic samplers were also used to collect 192 water sam- ples associated with runoff generated by significant rain events. For each of the samples collected, a wide battery of analytic determinations was performed, including solid loads, turbidity, organic pollution, nutrient and selected metals. Upon careful examination it has been possible to obtain different parame- ters related to the contamination control, like the ''event mean con- centration'' (EMC), maximum con- centrations and specific sediment loads. Moreover, a comprehensive statistical study including parameter correlation and cumulative proba- bility analyses helped to understand the pollutant mobilization behaviour within the quarry system. It can be concluded that mobilized contami- nation shows the anomalous pres- ence of some metals, whose concentrations are in excess when compared to the natural rock. This excess metal amount must be attributed to an anthropogenic source associated to mining and cutting operations.

An asymmetric, Margules-type, solid solution model was used to model the mixing behavior of Fe-Zn sphalerites. The model is based on an analysis of experimental results from fifteen independent data sources. After a careful, stepwise, analysis of the available runs, the solid solution model was constrained using a refined experimental database of 279 experiments which were simultaneously regressed to obtain the excess parameters and a general geobarometric equation. The model indicates that, when pressures are low, the value of γFeSSph, which is always greater than one, is higher at low FeS contents and an increase in temperature causes it to decline. However, for certain compositions γFeSSph values might be slightly less at low T than at high T. This behavior is corrected when pressure increases, regardless of the composition. The excess Gibbs free energy has positive values at any P&T while it is asymmetric. Pressure increases the value of the excess free energy. On the other hand, the Gibbs free energy of mixing is always negative, with a single minimum that tends to move towards Fe-poorer compositions as the pressure goes up. An increase in temperature leads to a more negative Gibbs free energy mixing function suggesting that increasingly Fe-poorer sphalerite would be expected at high temperatures and pressures. The application of the solid solution model to a selection of case-studies provided results which are consistent with independent pressure estimates. However, the pressure determinations for sphalerite + pyrite + pyrrhotite and sphalerite + pyrrhotite assemblages are very sensitive to uncertainties in the composition of the phases involved and, to a lesser extent, to temperature. The results of the application of the model to a field case (scheelite-mineralized Hercynian veins from the Central Pyrenees) were also consistent when compared with independent pressure-constraining silicate assemblages. Thus, the solid solution model described in this paper provides a workable framework with which to compute the pressures of the formation of rocks over a wide range of geological conditions.

[ES] Con el fin de analizar la influencia de las aguas subterráneas de la escombrera exterior de la antigua mina de lignito de As Pontes (Galicia) sobre el lago minero adyacente se ha procedido a hacer una caracterización hidrogeológica de la misma. Para ello, ha sido necesario hacer diferentes ensayos hidráulicos en distintos puntos representativos de la escombrera para estimar los parámetros hidrodinámicos e identificación de las distintas unidades hidrogeológicas, las cuales se pueden describir como independientes. En el presente trabajo se concluye que la cobertera externa de la escombrera presenta valores de permeabilidad característicos de un limo arcilloso distribuidos espacialmente de manera homogénea, por lo que se minimiza la posible infiltración y su posible percolación a posiciones más profundas, y su posterior descarga al lago por los taludes contiguos. La influencia de la descarga subterránea es nula., [EN] In order to analyze the influence of groundwater from the slag heap of the lignite mine of As Pontes (Galicia) on the mining adjacent lake it has proceeded to make a hydrogeological characterization of the slag heap. For this, it was necessary to make different hydraulic tests at different points representing the dump to estimate the hydrodynamic parameters and identification of the different hydrogeological units, which can be described as independent. In this study, we conclude that external covert of dump has homogeneously distributed values of permeability of clavey silt. Therefore, the possible infiltration and possible percolation to deeper positions and later discharge to lake by adjacent slopes is minimized. So, the influence of groundwater discharge is null.., Este trabajo se ha desarrollado dentro de un Convenio de Investigación financiado por ENDESA GENERACIÓN para el desarrollo y caracterización de las aguas subterráneas y procedentes de la escombrera exterior de la mina de As Pontes, La Coruña.

Synthetic rock samples can offer advantages over natural rock samples when used for laboratory rock physical properties studies, provided their success as natural analogues is well understood. The ability of synthetic rocks to mimic the natural stress dependency of elastic wave, electrical and fluid transport properties is of primary interest. Hence, we compare a consistent set of laboratory multi‐physics measurements obtained on four quartz sandstone samples (porosity range 20–25%) comprising two synthetic and two natural (Berea and Corvio) samples, the latter used extensively as standards in rock physics research. We measured simultaneously ultrasonic (P‐ and S‐wave) velocity and attenuation, electrical resistivity, permeability and axial and radial strains over a wide range of differential pressure (confining stress 15–50 MPa; pore pressure 5–10 MPa) on the four brine saturated samples. Despite some obvious physical discrepancies caused by the synthetic manufacturing process, such as silica cementation and anisotropy, the results show only small differences in stress dependency between the synthetic and natural sandstones for all measured parameters. Stress dependency analysis of the dry samples using an isotropic effective medium model of spheroidal pores and penny‐shaped cracks, together with a granular cohesion model, provide evidence of crack closure mechanisms in the natural sandstones, seen to a much lesser extent in the synthetic sandstones. The smaller grain size, greater cement content, and cementation under oedometric conditions particularly affect the fluid transport properties of the synthetic sandstones, resulting in lower permeability and higher electrical resistivity for a similar porosity. The effective stress coefficients, determined for each parameter, are in agreement with data reported in the literature. Our results for the particular synthetic materials that were tested suggest that synthetic sandstones can serve as good proxies for natural sandstones for studies of elastic and mechanical properties, but should be used with care for transport properties studies.