Search

Purpose: This paper draws on data from a research project that examined the professional relationships that existed between teachers of different generations within an educational setting, including both those inside and outside school. Design/methodology/approach: A qualitative approach was adopted to better understand participants' intergenerational relationships. Data were collected via semi-structured interviews conducted online. Data analysis was carried out using Atlas.ti 22 software. This focused on participants' professional relationships, generationally-inflected professional relationships, links to the school and connections with their environment. Findings: The paper shows that commitment to the profession and work climate were among the key aspects referred to by the interviewees. The different age groups agreed that they had experienced intergenerational feedback and that there was closer contact between peers of the same generation, which led to greater levels of affinity. The shared responsibility that comes with teaching and the sense of belonging were essential links to the school. The generational groups underlined the importance of building bridges and participating in collaborative networks to form connections with their environment. Originality/value: Although several studies have considered various factors influencing professional relationships from an intergenerational perspective, this paper adds value to the existing literature by providing new data and analyzing the barriers and opportunities experienced by teachers of different generations (novice, veteran and retired) in their professional work within and beyond the educational setting.

The aqueous oxidation of sulphide minerals leads to the generation of acid mine drainage (AMD), one of the main causes of water pollution worldwide. Mineral reactivity is greatly enhanced as a result of extraction and processes such as blasting, crushing, and grinding that increase rock surface area. The exposition of sulphide mine wastes to atmospheric conditions enhances AMD generation. However, a large number of processes and factors (e.g., pH, redox conditions, aqueous and surface complexation reactions) may control the mobility of elements in solution. In particular, the formation of soluble secondary minerals may act as transient storage of metals and acidity during AMD generation, leading however to their release upon rainfalls. To study the influence of mineralogy and grain size on the metal release from a variety of sulphide mine wastes collected in the Iberian Pyrite Belt, different grain size samples were treated with distilled water (S:L ratio 1:10) for 24 h simulating rainfall weathering. Results reveal that grain size plays a major role on metal mobility from sulphide mine wastes. However, mineralogical and geochemical evidence points at the partitioning of highly soluble secondary minerals among grain size fractions as the key factor controlling the metal release rate from these wastes. The results obtained show the importance of grain size on the reliability of the different leaching test procedures, and thus encourage standardizing these procedures worldwide.

Earth analogs are indispensable to investigate mineral assemblages on Mars because they enable detailed analysis of spectroscopic data from Mars and aid environmental interpretation. Samples from four sites in the Iberian Pyrite Belt (El Villar, Calañas, Quebrantahuesos, and Tharsis) were investigated using mineralogical, chemical, and spectroscopic techniques, with a focus on clay minerals and alteration environments. They represent Earth analogs of areas on Mars that underwent acidic alteration. X‑ray diffraction and transmittance mid-infrared data indicate that the rocks were subjected to several degrees of acid alteration corresponding to assemblages characterized by the following mixtures: (1) illite, chlorite, interstratified chlorite-vermiculite, kaolinite-smectite, and kaolinite; (2) illite, kaolinite, and alunite; and (3) jarosite and goethite. According to mineral stability data, these three assemblages correspond to pH values 7–5, 5–3, and <3, respectively. The lack of goethite in the illite-kaolinitealunite assemblage suggests an alteration in reducing conditions. Illite was progressively dissolved by acidic alteration but is sufficiently resilient not to be diagnostic of the intensity of the alteration. Illite and kaolinite were the two most abundant phyllosilicate minerals observed, and the main reaction involving phyllosilicates was the alteration of illite to kaolinite. Mixed-layer phases appeared mainly in the mildest degree of acid alteration, with few exceptions. This suggests a transition from a mechanism dominated by transformation to a mechanism dominated by dissolution-precipitation as the intensity of the acid alteration increases. Our results highlight the sparse kaolinite–alunite occurrences on Mars as worthy of specific investigation. Acid alteration on Mars is expected to be patchy and/or consisting of fine alteration rims. Alunite occurrences on Mars in the absence of goethite may indicate an acid alteration in reducing conditions. Kaolinite produced through acid alteration on Mars is expected to exist mainly as an end-member phase of low crystallinity, which would enhance IR absorption and increase its visibility.

Basaluminite is a poorly crystalline aluminum hydroxysulfate that precipitates in waters affected by acid mine drainage (AMD) and in acid sulfate soils (ASS). Its ability to sequester potentially toxic elements, such as Cu and As, makes it an important component of these systems, with strong environmental implications. Although it was initially described as a mineral, basaluminite is now considered a nanoscale variety of felsöbányaite, a rare mineral. In the present study, chemical analyses of natural and synthetic basaluminites are combined with data from advanced nanoscale characterization techniques such as high-energy X-ray diffraction (HEXD) and their corresponding pair distribution function (PDF) analyses, extended X-ray absorption fine structure (EXAFS), and solid-state nuclear magnetic resonance (ssNMR) spectroscopy. X-ray scattering data are analyzed with reverse Monte Carlo (RMC) modeling to obtain an atomistic representation of the disorder presents in this nanomineral. Sulfur K-edge EXAFS results show that sulfate is coordinated to the aluminum-octahedral framework of basaluminite mainly through outer-sphere ligands, though the existence of inner-sphere ligands seems to be significant in synthetic samples. PDF analyses show that both synthetic and natural basaluminites have identical short-range order, with ~1.2 nm coherent domain size, and share structural characteristics with felsöbányaite. Interestingly, 27Al ssNMR reveals the presence of, respectively, ~1 and 5% of tetrahedral and pentahedral coordinations. RMC models of basaluminite highlight the presence of structural point defects. The understanding of this nanocrystalline character has important implications in terms of the reactivity of this nanomineral in AMD and ASS. The lack of correlation between the spatial and temporal occurrence of basaluminite and felsöbányaite suggests that the similarities between both mineral structures could be fortuitous, and highlights the need for a re-evaluation of the status of basaluminite as a nanomineral.

Acid mine drainage remediation is an unresolved matter in abandoned mining districts around the world. Development and implementation of passive treatment systems in these areas are commonly focused on engineering and water quality aspects. Neoformed mineral phases precipitated within the reactive material of these passive treatments account for the removal of pollutants but also can cause clogging and passivation of the reactive substrate. After 20 months of operation and monitoring, the limestone-based passive treatment system implemented in Mina Esperanza (SW Spain) was sampled to study the relationship between water chemistry, mineral composition of the neoformed precipitates, and treatment performance. Water chemical profiles show the existence of three precipitation zones controlled by Fe, Al, and Zn hydrochemistry and also a migration with time of precipitation zones downward into the reactive material. These precipitation zones were also confirmed by a mineral study performed on the solid samples where either schwertmannite and goethite or hydrobasaluminite and Zn-rich green rust were the mineral phases that controlled the metal removal in the three precipation (Fe, Al, or Zn) zones. Iron and Al precipitates were observed to play a critical role in the time evolution of the reactive material hydraulic conductivity. Furthermore, Al precipitates passivated to some extent the limestone grains by armoring, although migration of the Fe precipitation zone and Al redissolution later activated the limestone grains. A higher proportion of limestone in the reactive mixture and the addition of new reagents to the bottom section of the reactive material (to enhance the reducing environment and to promote divalent metal removal) are proposed on the basis of this hydrochemical and mineralogical study for a future design for the Mina Esperanza passive treatment system.

Iron and Al precipitates play very important hydrochemical and environmental roles in aquatic environments affected by acid mine drainage. Despite their great importance, reliable characterization of these precipitates is problematic due to the high proportion of amorphous or poorly ordered mineral phases comprising these precipitates and because of their coexistence with intermediate to highly crystalline phases. To facilitate and improve the characterization of poorly ordered Fe and Al phases, a coupled differential X-ray diffraction (DXRD) and sequential extraction (SE) study was performed on a set of samples from an acid mine water passive treatment system. The results of these techniques indicate the presence of schwertmannite and goethite in the upper 5 cm of the passive treatment reactive material. Furthermore, a progressive decrease of the SO42-adsorbed to the schwertmannite surface is suggested by one of the SE steps. The presence of hydrobasaluminite and amorphous Al(OH)3is suggested on the basis of SE and thermodynamic modeling analysis. These techniques also allow a quantitative estimation of the proportion of each mineral present. As a result, a complete study of the distribution of each mineral throughout the reactive material profile and the role of each phase in removing metals from the mine water can be obtained. This information is useful, not only to improve the reactive material design, but also to understand the natural processes taking place in aquatic systems affected by mining.

In the present study, experiments in non-saturated leaching columns were conducted to characterize the neoformed phases that precipitate at the interface between two waste residues having different chemical characteristics: an acid mine drainage producer residue (i.e., pyritic sludge) and an acidity neutralizer residue (i.e., coal combustion fly ash). A heating source was placed on top of one of the columns to accelerate oxidation and precipitation of newly formed phases, and thus, to observe longer-scale processes. When both residues are deposited together, the resulting leachates are characterized by alkaline pH, and low sulfate and metal concentrations. Two mechanisms help to improve the quality of the leachates. Over short-time scales, the leaching of pyrite at high pH (as a consequence of fly ash addition) favors the precipitation of ferrihydrite, encapsulating the pyrite grains and attenuating the oxidation process. Over longer time scales, a hardpan is promoted at the interface between both residues due to the precipitation of ferrihydrite, jarosite, and a Ca phase-gypsum or aragonite, depending on carbonate ion activity. Geochemical modeling of leachates using PHREEQC software predicted supersaturation in the observed minerals. The development of a relatively rigid crust at the interface favors the isolation of the mining waste from weathering processes, helped by the cementation of fly ash owing to aragonite precipitation, which ensures total isolation and neutralization of the mine residues.