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Ortuno F.,Water Agency Agencia Catalana Of Laigua | Molinero J.,Amphos XXI Consulting S.L. | Garrido T.,Water Agency Agencia Catalana Of Laigua | Custodio E.,University of Barcelona
Water Science and Technology | Year: 2012

The main aquifer of the Llobregat delta (Barcelona, Spain) has been affected by seawater intrusion since the 1960s. The Catalan Water Agency (ACA) has sponsored the construction of a positive hydraulic barrier in order to stop the progress of seawater intrusion advance due to the intensive aquifer development. The hydraulic barrier consists of 15 wells into which highly treated reclaimed water from the waste water treatment plant of the Baix Llobregat is injected. Water is subjected, prior to the distribution to the injection wells, to secondary and tertiary treatments, and later to ultrafiltration, UV disinfection without chlorination, and salinity reduction through reverse osmosis. A preliminary pilot phase of the project was started in late 2007, with highly positive results, and the second phase started in mid 2010. Hydrogeological and hydrochemical monitoring data indicate an efficient performance and aquifer improvement. The evaluation of such efficiency and operational costs has been analyzed and discussed. © IWA Publishing 2012.


Ramos M.E.,University of Granada | Emiroglu C.,Giresun University | Garcia D.,Amphos XXI Consulting S.L. | Sainz-Diaz C.I.,University of Granada | Huertas F.J.,University of Granada
Langmuir | Year: 2015

In this work, a multiscale modeling of the interaction of oxalate with clay mineral surfaces from macroscale thermodynamic equilibria simulations to atomistic calculations is presented. Previous results from macroscopic adsorption data of oxalate on montmorillonite in 0.01 M KNO3 media at 25 °C within the pH range from 2.5 to 9 have been used to develop a surface complexation model. The experimental adsorption edge data were fitted using the triple-layer model (TLM) with the aid of the FITEQL 4.0 computer program. Surface complexation of oxalate is described by two reactions: >AlOH + Ox2- + 2H+ = >AlOxH + H2O (log K = 14.39) and >AlOH + Ox2- + H+ = >AlOx- + H2O (log K = 10.39). The monodentate complex >AlOxH dominated adsorption below pH 4, and the bidentate complex >AlOx- was predominant at higher pH values. Both of the proposed inner-sphere oxalate species are qualitatively consistent with previously published diffuse reflectance FTIR spectroscopic results for oxalate on montmorillonite edge surface (Chem. Geol. 2014, 363, 283-292). Atomistic computational studies have been performed to understand the interactions at the molecular level between adsorbates and mineral surface, showing the atomic structures and IR frequency shifts of the adsorption complexes of oxalate with the edge surface of a periodic montmorillonite model. © 2015 American Chemical Society.


PubMed | University of Granada, Amphos XXI Consulting S.L. and Giresun University
Type: Journal Article | Journal: Langmuir : the ACS journal of surfaces and colloids | Year: 2015

In this work, a multiscale modeling of the interaction of oxalate with clay mineral surfaces from macroscale thermodynamic equilibria simulations to atomistic calculations is presented. Previous results from macroscopic adsorption data of oxalate on montmorillonite in 0.01 M KNO3 media at 25 C within the pH range from 2.5 to 9 have been used to develop a surface complexation model. The experimental adsorption edge data were fitted using the triple-layer model (TLM) with the aid of the FITEQL 4.0 computer program. Surface complexation of oxalate is described by two reactions: >AlOH + Ox(2-) + 2H(+) = >AlOxH + H2O (log K = 14.39) and >AlOH + Ox(2-) + H(+) = >AlOx(-) + H2O (log K = 10.39). The monodentate complex >AlOxH dominated adsorption below pH 4, and the bidentate complex >AlOx(-) was predominant at higher pH values. Both of the proposed inner-sphere oxalate species are qualitatively consistent with previously published diffuse reflectance FTIR spectroscopic results for oxalate on montmorillonite edge surface (Chem. Geol. 2014, 363, 283-292). Atomistic computational studies have been performed to understand the interactions at the molecular level between adsorbates and mineral surface, showing the atomic structures and IR frequency shifts of the adsorption complexes of oxalate with the edge surface of a periodic montmorillonite model.


Jimenez-Martinez J.,University of Barcelona | Candela L.,University of Barcelona | Molinero J.,University of Barcelona | Molinero J.,Amphos XXI Consulting S.L | Tamoh K.,University of Barcelona
Hydrogeology Journal | Year: 2010

For semi-arid regions, methods of assessing aquifer recharge usually consider the potential evapotranspiration. Actual evapotranspiration rates can be below potential rates for long periods of time, even in irrigated systems. Accurate estimations of aquifer recharge in semiarid areas under irrigated agriculture are essential for sustainable water-resources management. A method to estimate aquifer recharge from irrigated farmland has been tested. The water-balance-modelling approach was based on VisualBALAN v. 2.0, a computer code that simulates water balance in the soil, vadose zone and aquifer. The study was carried out in the Campo de Cartagena (SE Spain) in the period 1999-2008 for three different groups of crops: annual row crops (lettuce and melon), perennial vegetables (artichoke) and fruit trees (citrus). Computed mean-annual-recharge values (from irrigation +precipitation) during the study period were 397mm for annual row crops, 201mm for perennial vegetables and 194mm for fruit trees: 31.4, 20.7 and 20.5% of the total applied water, respectively. The effects of rainfall events on the final recharge were clearly observed, due to the continuously high water content in soil which facilitated the infiltration process. A sensitivity analysis to assess the reliability and uncertainty of recharge estimations was carried out.


Candela L.,University of Barcelona | Elorza F.J.,Technical University of Madrid | Jimenez-Martinez J.,University of Barcelona | von Igel W.,University of Barcelona | von Igel W.,Amphos XXI Consulting S.L.
Computers and Electronics in Agriculture | Year: 2012

According to the general circulation models (CGMs) for future climate projections, a temperature increase, precipitation decrease, and an increase in the variability of extreme events may be expected in the future, likely reducing available water resources. For the western Mediterranean, future climate change projections indicate that temperature increase may range from 1.5 °C to 3.6 °C, and the precipitation decline will reach between 10% and 20%, which may result in a significant reduction of natural groundwater recharge. With the use of modelling tools, the amount of groundwater recharge under different climate change scenarios and varying agricultural management practices can be predicted, and water budget attributes can be estimated, which may allow for quantifying impacts, and assist in defining adaptation strategies. For the Inca-Sa Pobla basin (Balearic Islands, Spain), under future climate change projections, agricultural management alternatives of crop type distribution and irrigation demands are required for planned adaptation strategies. In the area, where irrigation water for agricultural practices originates from groundwater resources, adaptation measures based on a change from mixed crops to potatoes and a 20% decrease of agricultural land cultivation have proven to be efficient for the hydrologic system and associated wetland sustainability. © 2011 Elsevier B.V.


Grandia F.,Amphos XXI Consulting S.L. | Sena C.,Amphos XXI Consulting S.L. | Sena C.,University of Aveiro | Arcos D.,Amphos XXI Consulting S.L. | And 3 more authors.
Applied Geochemistry | Year: 2011

The Quaternary sediments representing the interface between the granite host rock and the Earth surface are of paramount importance when determining the potential cycling of anthropogenic and natural radionuclides in near-surface systems. This is particularly true in the case of high-level nuclear waste (HLNW) repositories placed in granite. In this work a modelling procedure is presented to quantitatively determine the retention capacity of a Quaternary till in the Forsmark area, which has been recently selected to host the deep geologic storage of HLNW in Sweden. Reactive transport numerical models have been used to simulate the intrusion of a deep groundwater carrying radionuclides potentially released from a repository into a Quaternary till. Four radionuclides (235U, 135Cs, 226Ra and 90Sr) have been selected according to their different geochemical behaviour and potential dose relevance to surface ecosystems. Numerical results indicate that repository-derived: (i) U will have a minor impact in the till, mainly due to the high natural concentration of U and its adsorption on ferrihydrite; (ii) Cs will be efficiently retained by cation exchange on illite; (iii) Ra will be retained via co-precipitation with barite; and although (iv) Sr will be retained via co-precipitation with calcite and cation exchange on illite, the retention capacity of the Quaternary till for Sr is limited. © 2011 Elsevier Ltd.


Credoz A.,French Atomic Energy Commission | Credoz A.,AMPHOS XXI Consulting S.L. | Bildstein O.,French Atomic Energy Commission | Jullien M.,French Atomic Energy Commission | And 3 more authors.
Applied Clay Science | Year: 2011

The reactivity of mixed-layer illite-smectite was investigated in batch and mixed-flow reactors in the presence of K-bearing mineral impurities (K-feldspar) in order to determine the reaction pathways and the kinetic rate of the reactions in a range of pH conditions pertinent to the context of CO2 geological storage.The mixed-layered illite-smectite (I-S) mineral was extracted from a natural clayey caprock and was studied at 80 °C, with a solution salinity of 0.1. M NaCl and over a pH range from 3 to 8.5. The experimental results show that the most important process taking place is illitization of the initial I-S. In the most acidic conditions, an intense illitization is observed, which was interpreted as a new proton-promoted illitization process. At neutral pH, illitization is less intense and is attributed to a classical thermal effect.In terms of the overall reaction rate (I/S and K-feldspar dissolution in a mixed flow experiment), the values calculated from the evolution of SiO2 concentrations fall in the range of the experimental values reported in the literature for smectites and illites.Implications of illitization processes on CO2 storage and clayey caprock integrity are also discussed. © 2011 Elsevier B.V.


Galindez J.M.,University of Santiago de Compostela | Molinero J.,Amphos XXI Consulting S.L.
Cement and Concrete Research | Year: 2010

Cement-based grout plays a significant role in the design and performance of nuclear waste repositories: used correctly, it can enhance their safety. However, the high water-to-binder ratios, which are required to meet the desired workability and injection ability at early age, lead to high porosity that may affect the durability of this material and undermine its long-term geochemical performance. In this paper, a new methodology is presented in order to help the process of mix design which best meets the compromise between these two conflicting requirements. It involves the combined use of the computer programs CEMHYD3D for the generation of digital-image-based microstructures and CrunchFlow, for the reactive transport calculations affecting the materials so simulated. This approach is exemplified with two grout types, namely, the so-called Standard mix 5/5, used in the upper parts of the structure, and the "low-pH" P308B, to be injected at higher depths. The results of the digital reconstruction of the mineralogical composition of the hardened paste are entirely logical, as the microstructures display high degrees of hydration, large porosities and low or nil contents of aluminium compounds. Diffusion of solutes in the pore solution was considered to be the dominant transport process. A single scenario was studied for both mix designs and their performances were compared. The reactive transport model adequately reproduces the process of decalcification of the C-S-H and the precipitation of calcite, which is corroborated by empirical observations. It was found that the evolution of the deterioration process is sensitive to the chemical composition of groundwater, its effects being more severe when grout is set under continuous exposure to poorly mineralized groundwater. Results obtained appear to indicate that a correct conceptualization of the problem was accomplished and support the assumption that, in absence of more reliable empirical data, it might constitute a useful tool to estimate the durability of cement-based structures. © 2009 Elsevier Ltd. All rights reserved.


Galindez J.M.,University of Santiago de Compostela | Molinero J.,Amphos XXI Consulting S.L.
Cement and Concrete Composites | Year: 2010

Reactive solute transport models have been broadly used over the last years to evaluate the durability of cementitious materials because they provide a mechanistic approach to cope with the complex diffusion-reaction phenomena involved in cement and concrete degradation processes. However, most of the numerical models published in the scientific literature use Fick's law as the constitutive equation for the diffusive transport of dissolved ions, neglecting the electrochemical constraints imposed by the various ionic fluxes, which conspire against the local electroneutrality of the system. In this work, the relevance of electrochemical diffusion and its impact on the nonlinear coupled phenomena concerned by cement degradation were evaluated, on the basis of its influence on the simulation of deterioration of concrete exposed to weak sulfate solutions. Results obtained show that diffusive approaches based on Fick's law may not be accurate enough for modeling the degradation of cementitious materials since, for the case considered, when ignored, electrochemical interactions in the diffusion process may lead to the inability of reactive transport models to reproduce key phenomena such as gypsum precipitation near the exposed cement surface. © 2010 Elsevier Ltd. All rights reserved.

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