The incorporation of arsenate (As(V)) in the gypsum structure is an important process for arsenic (As) fixation during industrial effluent treatment and may influence the mobility and bioavailability ...of As in surface environment. However, spectroscopic evidence is still lacking for its species and local structure. The species and local structure of As(V) in a gypsum lattice were investigated using Fourier transform infrared (FTIR) spectroscopy, density functional theory (DFT) modelling, and full-potential multiple scattering (FPMS) simulations. Ascorbic acid-treated As(V)-gypsum co-precipitates were used to avoid the influence of amorphous calcium arsenate on the characterization. The lack of the FTIR band in the range of 750–860cm−1 was an indicative that no AsO43− species was incorporated into the gypsum structure. DFT calculations proved that the incorporation of AsO43− was energetically much harder than HAsO42− species. The FPMS structural refinement yielded the optimal AsO interatomic distances of 1.77, 1.67, 1.65, and 1.66Å, with an average of 1.69±0.057Å, in agreement with the DFT and EXAFS results. Our work conclusively showed that HAsO42− dominated as the species of As(V) incorporated into the gypsum lattice, with the H atom in the HAsO42− group adjacent to water layer, regardless of pH.
Calcium carbonates such as calcite are the dominant hosts of inorganic iodine in nature and are potentially important for the retention and removal of radioactive iodine isotopes (129I and 131I) in ...contaminated water. However, little is known about the structural environment of iodine in carbonates. In this study, iodate (IO3−) doped calcite and vaterite have been synthesized using the gel-diffusion method at three NaIO3 concentrations (0.002; 0.004; 0.008M) and a pH value of 9.0, under ambient temperature and pressure. Inductively coupled plasma mass spectrometry (ICP-MS) analyses show that iodine is preferentially incorporated into calcite over vaterite. Synchrotron iodine K-edge X-ray absorption near-edge structure (XANES) spectra confirm that IO3− is the dominant iodine species in synthetic calcite and vaterite. Analyses of iodine K-edge extended X-ray absorption fine structure (EXAFS) data, complemented by periodic first-principles calculations at the density functional theory (DFT) levels, demonstrate that the I5+ ion of the IO3− group in calcite and vaterite is bonded by three and two additional O atoms (i.e., coordination numbers=6 and 5), respectively, and is incorporated via the charged coupled substitution I5++Na+↔C4++Ca2+, with the Na+ cation at a nearest Ca2+ site being the most energetically favorable configuration.
Abiotic hydrocarbons and carboxylic acids are known to be formed on Earth, notably during the hydrothermal alteration of mantle rocks. Although the abiotic formation of amino acids has been predicted ...both from experimental studies and thermodynamic calculations, its occurrence has not been demonstrated in terrestrial settings. Here, using a multimodal approach that combines high-resolution imaging techniques, we obtain evidence for the occurrence of aromatic amino acids formed abiotically and subsequently preserved at depth beneath the Atlantis Massif (Mid-Atlantic Ridge). These aromatic amino acids may have been formed through Friedel-Crafts reactions catalysed by an iron-rich saponite clay during a late alteration stage of the massif serpentinites. Demonstrating the potential of fluid-rock interactions in the oceanic lithosphere to generate amino acids abiotically gives credence to the hydrothermal theory for the origin of life, and may shed light on ancient metabolisms and the functioning of the present-day deep biosphere.
Present study reports the laboratory and field scale application of different organic and inorganic amendments to immobilize cadmium (Cd) and lead (Pb) in a co-contaminated alluvial paddy soil. For ...that purpose, lime, biochar, Fe-biochar and two composite amendments (CA) composed of biochar, lime, sepiolite and zeolite (CA1: composite amendment 1) and manure, lime and sepiolite (CA2: composite amendment 2) were firstly tested in an incubation experiment to ameliorate Cd and Pb co-contaminated alluvial soil. It was observed that liming and CA2 elevated the soil pH and reduced DTPA extractable Cd and Pb in the incubated soil leading to higher metal immobilization. Therefore, efficiency of lime and CA2 was further investigated in field conditions with mid rice as the test crop to evaluate field scale immobilization and precise application rate for the tested soil type. DTPA and CaCl2 extractable Cd (46 and 51%) and Pb (68 and 70%) in field soil were decreased with applied treatments. Speciation of Cd and Pb also promoted conversion of metal exchangeable contents to less-available forms. Activated functional groups on amendments’ surface (_OH bonding, C_O and CO, -O-H, Si–O–Si, carboxylic and ester groups) sequestered metals by precipitation, adsorption, ion exchange or electro static attributes. Application of lime at 2400 kg/acre (T4) and CA2 at 1200 kg/acre was more effective in reducing rice shoot and grains metal contents. Moreover, obtained results in terms of pH, extractable content, speciation and yield, and microanalysis of amendments highlights the remarkable efficiency of lime and composite amendment to sorb Cd and Pb providing the key evidence of these amendments for metals immobilization and environmental remediation. Considering these results, lime and CA2 are potential amendments for co-contaminated rice field especially in context of alluvial soil.
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•Inorganic, organic and composite amendments decreased the DTPA extractable metals.•Lime addition elevates incubated and field soil pH.•Cd and Pb speciation reduced exchangeable form of metals.•Lime and CA2 were effective in reducing metal availability in alluvial soil.
Inorganic and organic additives have potential to remediate metal polluted sites but their composite application was more helpful in reducing Cd and Pb availability in co-contaminated alluvial soil.
A direct spectra‐to‐spectra method is developed for generating floor response spectra (FRS) for structures under earthquake excitations at multiple supports in terms of ground response spectra (GRS). ...Only GRS, “t‐response spectra” (tRS), and basic modal information of primary structures, which can be readily obtained from modal analyses, are needed. FRS are separated into dynamic part and quasi‐static part, which are combined by a new combination rule FRSMS‐CQC developed using random vibration theory. FRSMS‐CQC can account for the correlations between various components affecting FRS, that is, the correlation between the responses of oscillators excited by any two vibration modes, the correlation between the response of an oscillator excited by a vibration mode and the response of an oscillator mounted directly on a support, and the correlation between the responses of oscillators mounted on two different supports. In particular, two special cases, that is, excitations in the same direction at two supports being fully correlated and excitations at two supports being uncorrelated, are considered. The direct method can also be applied to generate tertiary response spectra (TRS) from FRS at multiple supports of secondary structures.
Numerical example of a piping system mounted on different buildings, which are subjected to tridirectional seismic excitations at the foundation level, is presented to demonstrate the superiority of the proposed method. It is shown that FRS/TRS determined by time‐history (TH) analysis have large variabilities, particularly at FRS/TRS peaks. The proposed direct method, which avoids the deficiencies of time history methods, is of excellent accuracy, efficiency, and simplicity.
Mercury (Hg) enrichment in stratigraphic successions is now widely used as a proxy for volcanic inputs, often for the purpose of documenting a relationship between large igneous province (LIP) ...magmatism and ecosystem perturbations. Earlier studies of Hg in Ordovician/Silurian boundary (OSB) sections in South China and Laurentia identified transient spikes in Hg/TOC ratios, on the basis of which a link between volcanism and the Late Ordovician mass extinction (LOME) was claimed. However, Hg enrichments must be tested based on normalization to their main host phase, and Hg/TOC is a suitable proxy only if Hg is mainly complexed by organic matter in the sediment. Here, we demonstrate that Hg in three OSB sections in South China (Qiliao, Yanzhi, and Jiaoye) is overwhelmingly associated with pyrite, as shown by r(Hg–TS) > 0.9 (versus r(Hg–TOC) < 0.1) and by EDS elemental mapping. This association requires that Hg concentrations be normalized to pyrite content as proxied by total sulfur TS, rather than to total organic carbon TOC. The resulting Hg/TS profiles show no significant enrichments at any level within the Upper Ordovician–lower Silurian of the study sections. Also, mercury isotope data show constant mass-independent fractionation (Δ199Hg) values (+0.11 ± 0.03‰) that are inconsistent with volcanic inputs. We therefore infer that previous reports of Hg enrichments in OSB sections were due to the presence of Hg-rich sulfides, and that Hg data from both the present and earlier studies provide no evidence of any volcanic influences on the LOME. The results of the present study highlight the need for caution in applying the Hg proxy for volcanic inputs and the importance of evaluating the main host phase of Hg in paleo-marine sediments.
•First report of pyrite (instead of organic matter) as major host for Hg in Ordovician–Silurian boundary strata.•Absence of Hg/TS (mercury/total sulfur) spikes in three Ordovician–Silurian boundary sections in South China.•Mercury isotope data show constant MIF (Δ199Hg) values that are inconsistent with volcanic inputs.•Evidence against published claims of volcanic Hg inputs and volcanic influences on Late Ordovician Mass Extinction.•Demonstrates need to identify and normalize Hg to its main host phase in marine sediments when used as a volcanic proxy.
The chemical composition, textures and mineral associations of pyrite provide key information that help elucidate the evolution of hydrothermal systems. However, linking the compositional and ...micro-textural features of pyrite with a specific physico-chemical process, e.g., boiling versus non-boiling, remains elusive and challenging. In this study we examine pyrite geochemical and micro-textural features and relate these results to pyrite-forming processes at the active Cerro Pabellón Geothermal System (CPGS) in the Altiplano of the northern Chile. We integrate electron microprobe analysis (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) data with micro-textural observations of pyrite and associated gangue minerals recovered from a ∼500 m long drill core that crosscuts the argillic, sub-propylitic and propylitic alteration zones of the CPGS. Additionally, we carried out a Principal Component Analysis (PCA) in order to inspect and understand the main data structure of the pyrite geochemical dataset. The concentrations of precious metals (Au and Ag), metalloids (As, Sb, Se, Bi and Tl), and base and heavy metals (Cu, Co, Ni and Pb) in pyrite from the CPGS are significant. Among the elements analyzed, As, Cu and Pb are the most abundant with concentrations that vary from a few parts per million (ppm) to wt% levels (up to 4.4 wt% of As, 0.5 wt% of Cu and 0.2 wt% of Pb). Based on contemporaneous gangue mineral associations and textures, the mechanisms of pyrite precipitation in the CPGS were inferred. Pyrite formed during vigorous boiling is characterized by relatively high concentrations of As, Cu, Pb, Ag and Au and lower concentrations of Co and Ni compared to pyrite formed under different conditions. These anhedral to euhedral pyrite grains display zones with a porous texture and abundant mineral micro- to nano-inclusions (mainly galena and chalcopyrite) indicating a formation by rapid crystallization. In contrast, pyrite formed under gentle boiling (more gradual cooling and less abrupt physico-chemical variations than in vigorous boiling) to non-boiling conditions is characterized by a higher concentration of Co and Ni, and relatively low concentrations of As, Cu, Pb, Ag and Au. Texturally, these pyrites form aggregates of euhedral and pristine pyrite crystals with scarce pores and mineral inclusions suggesting formation under steadier physico-chemical conditions. Our results show that pyrite can not only record the chemical evolution of hydrothermal fluids, but can also provide critical information related to physico-chemical process such as boiling and phase separation. Since boiling of aqueous fluids is a common phenomenon occurring in a variety of pyrite-forming environments, e.g., active continental and seafloor hydrothermal systems, and porphyry Cu-epithermal Au-Ag deposits, pyrite compositional and textural features are a valuable complement for discriminating and tracking boiling events in modern and fossil hydrothermal systems.
Raman spectroscopy is increasingly being used in biology, forensics, diagnostics, pharmaceutics and food science applications. This growth is triggered not only by improvements in the computational ...and experimental setups but also by the development of chemometric techniques. Chemometric techniques are the analytical processes used to detect and extract information from subtle differences in Raman spectra obtained from related samples. This information could be used to find out, for example, whether a mixture of bacterial cells contains different species, or whether a mammalian cell is healthy or not. Chemometric techniques include spectral processing (ensuring that the spectra used for the subsequent computational processes are as clean as possible) as well as the statistical analysis of the data required for finding the spectral differences that are most useful for differentiation between, for example, different cell types. For Raman spectra, this analysis process is not yet standardized, and there are many confounding pitfalls. This protocol provides guidance on how to perform a Raman spectral analysis: how to avoid these pitfalls, and strategies to circumvent problematic issues. The protocol is divided into four parts: experimental design, data preprocessing, data learning and model transfer. We exemplify our workflow using three example datasets where the spectra from individual cells were collected in single-cell mode, and one dataset where the data were collected from a raster scanning-based Raman spectral imaging experiment of mice tissue. Our aim is to help move Raman-based technologies from proof-of-concept studies toward real-world applications.
In this work, we report on the synthesis and characterization of nanoporous bimetallic metal-organic frameworks (FeCo-BDC). Effects of synthesis time and temperature on the structures, morphology, ...and catalytic performance of FeCo-BDC were investigated. Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) were used to reveal the morphological and textural characteristics. The crystal structure and chemical composition of FeCo-BDC were determined by means of X-ray powder diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) measurements. Interestingly, FeCo-BDC grew into the same crystal structure with different morphology in the temperature of 110–150 °C with 12–48 h. The heterogeneous catalytic activity of FeCo-BDC was tested to activate peroxydisulfate (PDS) and peroxymonosulfate (PMS) for removal of methylene blue (MB). The results found that FeCo-BDC synthesized at 150 °C with 24 h exhibited the best catalytic performance for PMS and obtained 100% of MB removal within 15 min. The abundant unsaturated metal active sites of Fe(II) and Co(II) in the skeleton of FeCo-BDC made a great contribution to the generation of sulfate (▪) and hydroxyl radicals (OH), which resulted in the excellent performance for MB degradation.
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•FeCo-BDC with mesoporous and microporous structure was facile synthesized.•The same crystal structure of FeCo-BDC had diverse morphology.•The nodes of bimetallic MOFs presented with unsaturated sites of Fe(II) and Co(II).•FeCo-BDC showed excellent performance for removal of contaminants.•▪ and OH were identified as the primary reactive species
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