Geochemical Anomalies in Soils and Surface Waters in an Area Adjacent to a Long-Used Controlled Municipal Landfill

Municipal landfills, even when controlled, are potential sources of soil and water pollution in surrounding areas, due to the migration of pollutants through water and air. This research assesses geochemical anomalies of heavy elements and rare earth elements in soils and surface waters in an adjacent area to a controlled municipal landfill near Madrid (Central Spain), under long-term operation. Twenty soil and eighteen water samples were collected in 2017 and 2018 and analyzed for this purpose. Spatial distribution and concentrations of heavy elements (Ag, Cd, Cu, Mn, Ni, Pb, Tl, and Zn) and rare Earth elements (La, Ce, and Gd) are heterogeneous and significantly higher than soil background levels, but below the legal limits to consider intervention. Accumulation of heavy and rare Earth elements in soil nearest the landfill is attributed to occur via wind and wind-driven rain transport, while their accumulation in sediments is attributed to water transport through the creeks. Surface waters show large contamination by organic and inorganic compounds and influence geochemical anomalies in sediments. The water quality is below allowable concentrations for drinking water. The combined evaluation of the soil and water samples performed in the present work is proposed as a pilot study that may be applicable to similar surrounding landfill areas worldwideThe work has been partially financed by the Faculty of Sciences of the Autonomous University of Madrid

Ammonium concentration in stream sediments resulting from decades of discharge from a wastewater treatment plant

A study of ammonium pollution in the sediments of a stream that receives wastewater treatment plant (WWTP) discharge has been carried out. It is urgently necessary to find environmental indicators that can help prevent and detect potential contamination of water, as water is an increasingly scarce resource. To understand the behaviour of ammonium ions introduced by a historical (50-year) contamination process, vertical boreholes were drilled in the stream banks to depths between 30 and 120 cm. Moisture, pH, ammonium (soluble and exchangeable), and clay fraction content were analysed. The variation profile of these parameters was evaluated as a function of depth to determine factors related to the distribution of ammonium in several locations along the stream banks. The ammonium concentration was asymmetrically distributed among samples collected in near-surface locations, with ammonium concentrations between 0.3048 mmol/kg soil and 0.0007 mmol/kg soil. Ammonium was typically concentrated at sediment depths of 30–40 cm, which also exhibited the highest clay fraction content. High positive correlations were detected (r > 0.8; p < 0.0001) among the different ammonium variables (exchanged and dissolved species). No contamination effect was observed below 60–70 cm depth, which was due to ammonium retention in a natural barrier layer of clayey sediment. The clays in our study area (previously identified as smectite, a 2:1 sheet silicate) were able to control the contamination by retaining ammonium in the interlayers, which retarded nitrification. It is suggested that clay could serve as a geo-indicator of ammonium pollution evolutio

Geochemical interactions at the steel-bentonite interface caused by a hydrothermal gradient

Bentonites are used in deep geological disposal facilities as an engineered barrier to isolate high level radioactive waste, contained in metallic canisters. The present study, performed at laboratory scale, evaluated the behaviour of MX-80 (Na-bentonite) and FEBEX (Ca-Mg-Na-bentonite) in contact with carbon steel, subjected to a hydrothermal gradient. A dominant Na-Cl-SO4 saline solution was injected towards the compacted bentonite from the top, while a heater, located at the bottom in contact with the steel disc, maintained a constant temperature of 100 °C. The cells were studied after one and six months of interaction. Changes in the physical (water content and specific surface area) and chemical (cation exchange capacity and element distribution) properties of the bentonite were observed, as well as the formation of a corrosion layer on the steel, at the interface with bentonite, mainly composed of magnetite, maghemite and hematite. The bentonites were mainly altered at the mm scale, being enriched in iron content, and changing their ion distribution to Ca-dominant smectite (in MX-80 bentonite)This project has received funding from the European Union’s Horizon 2020 research and innovation programme 2014-2018 under grant agreement N◦84759

Lime mortar-compacted bentonite-magnetite interfaces: An experimental study focused on the understanding of the EBS long-term performance for high-level nuclear waste isolation DGR concept

The aim of this study was to obtain evidences regarding the physical and geochemical processes occurring as a result of the combined effects of cementitious materials from the concrete degradation and magnetite from steel corrosion on the bentonite barrier during disposal of high-level radioactive waste.A series of six experiments were done that attempt to reproduce the repository conditions prevailing from 1000 to 3000 years after emplacement of wastes. A lime mortar was used as the source of calcium and alkalinity as this is the presumed reactive product produced during concrete degradation at long-term. Magnetite powder was used to simulate the final corrosion product of cast iron and C-steel under anaerobic conditions. Either a natural FEBEX bentonite or a pretreated "aged" sample, depleted in exchangeable Mg and enriched in K, were used as the swelling clay component. Experiments, with both types of bentonite, were performed simultaneously in cylindrical specimens (50 mm diameter, 25 mm length), confined in a Teflon® sleeve/steel case cells. These specimens were composed of cement mortar in contact with compacted bentonite, which was in turn in contact with compressed magnetite powder. They were hydrated with an artificial Na+-Ca2+×SO42-type Spanish reference clayey formation water for 18 months at 60 °C and constant hydraulic pressure applied through the base of the mortar.After dismantling and sampling the specimens, distribution of soluble ions, exchangeable cations and mineralogy were studied in the bentonite by different instrumental techniques. Iron migration or any impact of the corrosion products in the bentonite was not noticeable in the clay. Both, mortar and magnetite acted as sinks of chloride and sulfate. Small quantities of Ca-Al-sulfates and carboaluminates, which can allocate chlorides, were determined near the mortar-bentonite interface. Portlandite dissolved near the bentonite interface and induced the formation of calcium silicates hydrates (C-S-H) phases cementing the clay interface characterizing a calcium front that was developed from the mortar towards the bentonite. Magnesium silicate hydrates (M-S-H) phases were also concentrated at the interface with mortar in the natural bentonite. It was also determined that natural bentonite has potentially higher buffering capacity attenuating the calcium alkaline front than the pretreated clay. In both cases, a low porosity bentonite-mortar zone was experimentally created at the interface. This type of material should be carefully studied in order to predict the potential for further development of a diffusive alkaline alteration, the radionuclides retention and the consequences in the hydration rate of the unaffected bentonite bufferThe research leading to these results has received funding from the European Atomic Energy Community's Seventh Framework Program (FP7/2007–2011) under grant agreement no. 249681

Reactive transport models of the geochemical interactions at the iron/bentonite interface in laboratory corrosion tests

Carbon steel and compacted bentonite have been proposed as candidate materials for the overpack and buffer, respectively, of the multi-barrier system of a geological high-level radioactive waste repository. Carbon steel corrosion may impair bentonite properties. The interactions of corrosion products and bentonite are analyzed with laboratory corrosion tests. Here coupled thermo-hydro-chemical-mechanical (THCM) models of two types of heating and hydration tests performed on compacted bentonite in contact with Fe powder are presented to study the iron-bentonite interactions at representative repository conditions. Tests on small cells (SC) were performed under unsaturated non-isothermal conditions in 25 mm long columns containing 21 mm of bentonite and 4 mm of Fe powder. Tests on medium-size cells (FB) were performed under unsaturated non-isothermal conditions in 99.8 mm long columns containing 86.8 mm of bentonite and 13 mm of Fe powder. Model results for the SC tests showed that magnetite and Fe(OH)2(s) were the main corrosion products which compete for Fe2+ precipitation. Computed corrosion products precipitate mainly in the Fe powder, penetrate a few mm into the bentonite and reproduce the measured iron weight data. Model results of the FB tests showed that magnetite precipitates throughout the Fe powder interface and reproduce the main trends of the corrosion products. Model results of these corrosion tests will be of great relevance for the performance assessment of engineered barriers of radioactive waste repositoriesThe research leading to these results was funded by ENRESA within the Work Package ACED of EURAD (European Joint Programme on Radioactive Waste Management of the European Union, grant agreement nº 847593), the Spanish Ministry of Science and Innovation (PID2019-109544RB-I00) and the Galician Regional Government (Grant ED431C2021/54). The comments and corrections of the special editor and the two anonymous reviewers are greatly appreciate

Bentonite powder XRD quantitative analysis using Rietveld refinement: Revisiting and updating bulk semiquantitative mineralogical compositions

Bentonite is a claystone formed by a complex mineralogical mixture, composed of mont-morillonite, illite, and accessory minerals like quartz, cristobalite, feldspars, carbonates, and minor amounts of iron oxy-hydroxides. Bentonite presents complexity at various scales: (1): a single mineral may present different chemical composition within the same quarry (e.g., feldspars solid solu-tions); (2): montmorillonite presents variability in the cation-exchange distribution while illite may be presented as mixed-layer with smectite sheets; and (3): hardness and crystal size are larger in accessory minerals than in clay minerals, preventing uniform grinding of bentonite. The FEBEX bentonite used is originally from Almería (Spain), and it is a predominantly calcium, magnesium, and sodium bentonite. This Spanish FEBEX bentonite has been hydrothermally altered at laboratory scale for 7–14 years. A thermal gradient was generated by heating a disk of pressed iron powder, simulating the metal waste canister, in contact with the compacted bentonite sample. Hydration was forced from the opposite direction. XRD recorded patterns were very similar. In order to min-imize the bias of XRD semi-quantitative determination methods, Rietveld refinement was per-formed using BGMN software and different structural models. Confidence in the quantification of the main phases allows us to convincingly detect other subtle changes such as the presence of calcite in the hydration front, right at the interface between the saturated and unsaturated bentonite, or the presence of goethite, and not hematite, in the saturated bentonite, near the source of hydration. Smectite component was 72 ± 3% and the refinement was consistent with the presence of ~10% illite, comparable with previous characterization

Las arcillas en sociedad: reconstruyendo el pasado y modelando el futuro. La Sociedad Española de Arcillas (SEA)

Se hace referencia a la historia de la Sociedad Española de Arcillas (SEA), una de las Sociedades científicas más veteranas de España, a la ciencia en torno a la que se proyecta, y a las perspectivas y objetivos que acompañan a la misma. El comienzo de esta sociedad científica se sitúa en 1959 con la fundación del grupo español de Minerales de la Arcilla (GEMA), que dio lugar a la SEA en 1971, la cual va camino de cumplir 64 años

Synthesis and characterization of nano Fe and Mn (hydr)oxides to be used as natural sorbents and micronutrient fertilizers

Fe and Mn (hydr)oxides are widely used as contaminant sorbents in water/wastewater systems but their potential use as micronutrient fertilizers is still poorly known. In this research, four nano-metal (hydr)oxides (amorphous Mn oxide (AMO), Fe-Mn binary oxide (FMBO), two-line ferrihydrite (2L-Fh) and goethite) were successfully synthesized and completely characterized (infrared and Mössbauer spectroscopy, X-ray diffraction particle size, specific surface area, point of zero charge). AMO, FMBO and 2L-Fh were introduced to interact with AgNO3 (20.0 µM) and TlNO3 (100.0 µM) diluted solutions for three days to check their potential capability as potential Ag+ and Tl+ adsorbents. AMO and FMBO (4% w/w) were tested as nanofertilizers by arranging a hydroponic bioassay for 35 days on white lupin culture as a Mn-hyperaccumulator plant model. AMO structure was identified as an amorphous mixture of Mn oxides while FMBO was an Fe dopped birnessite. Both materials were efficient in extracting Ag+ and Tl+ although large Mn concentration was released from FMBO to the solutions. AMO and FMBO promoted Fe and Mn nutrition in plants. Synthetic iron chelate (Fe-EDDHA), present in the nutrient dissolution, could be adsorbed onto AMO surface by producing Fe and Mn accumulation in roots and increasing Mn uptake rate without toxicity symptoms. Therefore, AMO and FMBO not only demonstrated their efficiency as adsorbents, but also displayed they would be promising nanomaterials as micronutrient fertilizer

Evaluation of the sorption potential of mineral materials using tetracycline as a model pollutant

Tetracycline (TC) is among the most used antibiotics in animal feedstock in the EU. Antibiotics’ persistence as emerging pollutants in the environment is evidenced by their long half-life in residual organic-mineral sediments and waters. The risk associated with this persistence favours antibiotic-resistant microbiota, affecting human health and ecosystems. The purpose of the present work is to assess the adsorption of TC into natural clay minerals, synthetic iron hydroxides and calcined sewage sludge. TC adsorption isotherms were performed in three replicated batch tests at three di erent pH values (4, 6, 8) and TC concentrations (33–1176 mg.L−1). X-Ray di raction (XRD) mineralogy, cation exchange capacity (CEC), Brunauer, Emmett and Teller specific surface area (BET-SSA) and point of zero charge salt effect (PZSE) were determined for the characterization of materials. Sorption was analysed by means of fitting Langmuir and Freundlich adsorption models, which showed good fitting parameters for the studied materials. Low-charge montmorillonite (LC Mnt) is displays the best sorption capacity for TC at maximum TC concentration (350–300 mgTC.g−1) in the whole range of pH (4–8). Sepiolite and smectites adsorbed 200–250 mgTC.g−1, while illite, calcined sludge or iron hydroxides present the lowest adsorption capacity (<100 mgTC.g−1). Nevertheless, illite, sepiolite and ferrihydrite display high adsorption intensities at low to medium TC concentrations (<300 mg.L−1), even at pH 8, as is expected in wastewater environmental conditionsThis work has been economically supported by the Ministry of Economy and Competitiveness of Spain (CTM2013-47874-C2-2-R and AGL2016-78490-R)

Biogeofilter with hydrothermal treated stevensite clay and laccase enzymes for retention and degradation of tetracycline

The concentration of antibiotics in surface water is an issue of high concern. The present study aims to manufacture and evaluate a biogeofilter, with stevensite clay and enzymes immobilized on it, for the adsorption and degradation of tetracycline-based antibiotics. To retain the small particle aggregates of the clay in the filter, a hydrothermal treatment was applied to the stevensite, prior to compaction in pellets and its insertion into a cylindric cell, mixed with sand. The structure of the pellets avoids the loss of the clay material during the fluid transport through the porous medium. Several temperature treatments were applied to the pellets, but the treatment at 300 °C was revealed as the best option. Laccase enzymes were immobilized on the stevensite surface. Reactive transport experiments of tetracycline solutions were performed through the transport cells. The biogeofilter has a relevant adsorption capacity with a significant degradation factor. By modelling with STANMOD software, the hydrodynamic characteristics of the transport were determined and, therefore, the behaviour of a large-scale filter and transports of low tetracycline concentrations could be predicted. The results obtained are promising for irrigation systems at medium scale, as well as for the perspective of wastewater treatment plants at large scaleThis work was supported by the Spanish State Research Agency (Project PDC2021-120744-I00). Adrien Saphy’s stay in Madrid was funded by an Erasmus gran