Stable Mineral Research Articles

Past, present and future global influence and technological applications of iron-bearing metastable nanominerals

Iron-bearing nanominerals such as ferrihydrite, schwertmannite, and green rust behave as metastable precursors leading to the formation of more thermodynamically stable iron mineral phases (e.g., jarosite, goethite, hematite, and magnetite). However, this transformation may last from days to tens or even hundreds of years, making them the most predominant iron-bearing minerals at environmental conditions and at the human time scale. The present review characterizes ferrihydrite, schwertmannite, and green rust nanominerals according to their main physical and chemical properties, and at both nano- and meso-scales. It also presents a comprehensive review of the multiple past and present Earth environments where these nanominerals have played, and still play, a pivotal role in the geochemistry, mineralogy and environmental nanogeosciences of these environments. Finally, the present and future technological applications of these nanominerals as well as their role in the generation of a more sustainable human-Earth relationship is discussed, with a special emphasis on their use in new circular economies and green based technologies.

Climate Effects on Subsoil Carbon Loss Mediated by Soil Chemistry.

Subsoils store at least 50% of soil organic carbon (SOC) globally, but climate change may accelerate subsoil SOC (SOCsub) decomposition and amplify SOC-climate feedbacks. The climate sensitivity of SOCsub decomposition varies across systems, but we lack the mechanistic links needed to predict system-specific SOCsub vulnerability as a function of measurable properties at larger scales. Here, we show that soil chemical properties exert significant control over SOCsub decomposition under elevated temperature and moisture in subsoils collected across terrestrial National Ecological Observatory Network sites. Compared to a suite of soil and site-level variables, a divalent base cation-to-reactive metal gradient, linked to dominant mechanisms of SOCsub mineral protection, was the best predictor of the climate sensitivity of SOC decomposition. The response was "U"-shaped, showing higher sensitivity to temperature and moisture when either extractable base cations or reactive metals were highest. However, SOCsub in base cation-dominated subsoils was more sensitive to moisture than temperature, with the opposite relationship demonstrated in reactive metal-dominated subsoils. These observations highlight the importance of system-specific mechanisms of mineral stabilization in the prediction of SOCsub vulnerability to climate drivers. Our observations also form the basis for a spatially explicit, scalable, and mechanistically grounded tool for improved prediction of SOCsub response to climate change.

Spectral reflectance properties of minerals exposed to martian surface conditions: Implications for spectroscopy-based mineral detection on Mars

Spectral reflectance properties of eight hydrated minerals including zeolites, sulfates, and silica-rich sinter were investigated under simulated Mars surface conditions. The minerals were selected based on their past detection on Mars by remote sensing data and certain minerals merited further investigations based on previous spectral studies. Long duration 763-day (∼26-month) exposure (atmosphere of 5 ​Torr CO2 with two periods of UV radiation) and 6 weeks exposure to ambient temperatures after ∼26 months was conducted to determine mineral stability on the surface of Mars by assessing changes to absorption band depths, widths, shape, center, and spectral slope. Changes in all of these spectral metrics were observed for at least one of the samples. We found longer-term changes of some spectral properties past the termination of previous published studies for certain samples and some which may extend beyond the duration of the experimental run. Some of the spectral changes were reversible when the samples were re-exposed to the ambient terrestrial environment. These spectral changes could be related to various processes, such as rapid loss and reaccumulation of adsorbed water, preferential loss of bound water versus structural OH, changes in Fe3+ bridging cations and structure, and decomposition of some phases. The changes in a wide range of spectral properties suggests that analysis of observational data for Mars should be approached with an appreciation for how exposure to Mars surface conditions can affect spectroscopy-based interpretations of mineralogy. The results are also relevant to understanding spectral changes seen in rover-exposed subsurface regolith, and for selecting samples for caching and return to Earth: i.e., stability before, during, and after sampling, caching, return to Earth, and subsequent analysis in terrestrial laboratories.

Fast and Efficient Removal of Uranium onto a Magnetic Hydroxyapatite Composite: Mechanism and Process Evaluation

The exploration and rational design of easily separable and highly efficient sorbents with satisfactory capability of extracting radioactive uranium (U)-containing compound(s) are of paramount significance. In this study, a novel magnetic hydroxyapatite (HAP) composite (HAP@ CoFe2O4), which was coupled with cobalt ferrite (CoFe2O4), was rationally designed for uranium(VI) removal through a facile hydrothermal process. The U(VI) ions were rapidly removed using HAP@ CoFe2O4 within a short time (i.e., 10 min), and a maximum U(VI) removal efficiency of 93.7% was achieved. The maximum adsorption capacity (Qmax) of the HAP@CoFe2O4 was 338 mg/g, which demonstrated the potential of as-prepared HAP@CoFe2O4 in the purification of U(VI) ions from nuclear effluents. Autunite [Ca(UO2)2(PO4)2(H2O)6] was the main crystalline phase to retain uranium, wherein U(VI) was effectively extracted and immobilized in terms of a relatively stable mineral. Furthermore, the reacted HAP@CoFe2O4 can be magnetically recycled. The results of this study reveal that the suggested process using HAP@CoFe2O4 is a promising approach for the removal and immobilization of U(VI) released from nuclear effluents.

Types and Micromorphology of Authigenic Carbonates in the Kolyma Yedoma Ice Complex, Northeast Siberia

The study focuses on authigenic carbonates that are widespread in different deposition environments and are a component part of the terrestrial biogeochemical cycle of carbon. Samples from the Kolyma Yedoma Ice Complex that formed during the Sartan Cryochrone (MIS 2), the coldest period of the Late Pleistocene, in the northeastern Siberian lowlands, have been studied utilizing scanning electron microscopy and energy-dispersive spectroscopy with replica technique. The samples bear signatures of irreversible multistage cryogenic changes in structure and composition, with the formation of authigenic minerals. Authigenic carbonates as secondary phases in the Ice Complex deposits are remarkable by local changes in chemical, physical, and other properties, which induce gradual changes in the lattice and conversion of one mineral species to another. As a result, the sediments may contain stable and metastable minerals. Crystalline species like calcite or aragonite precipitate from aqueous solutions and their presence are restricted to free pore space in segregation ice. Metastable phases may be produced as an initial reaction product between the CO2 and the aqueous phase, while mineral surfaces and small pores act as possible nucleation sites. Organic matter is also an important agent in the cryometamorphism of sediments, including precipitation of authigenic phases due to the freezing of colloids and high-molecular compounds.

One-step removal of high-concentration arsenic from wastewater to form Johnbaumite using arsenic-bearing gypsum

High-level arsenic-containing wastewater (HAW) causes serious environmental pollution. Chemical precipitation is the most widely used technology for treating HAW. However, chemical precipitation generates huge amounts of hazardous solid wastes, which leads to secondary pollution. In this work, an efficient method, producing no secondary pollution was developed for one-step complete removal of As(V) from HAW using a hazardous solid waste namely arsenic-bearing gypsum (ABG). After the treatment, ABG was transformed into highly stable and environment-friendly mineral Johnbaumite. Meanwhile, the arsenic concentration in the wastewater decreased from 10,000 mg L−1 to 0.22 mg L−1 under optimized hydrothermal conditions (ABG dosage of 50 g L−1, solution pH of 13.5, temperature of 150 °C for 12 h). The mechanism mainly included the following processes: (i) The phase transformation of ABG resulted in the release of calcium and hydrogen arsenate ions in ABG, (ii) Hydrogen arsenate ions transformed into arsenate ions in alkaline environment, and (iii) Under alkaline conditions, calcium ions combined with arsenate ions to form Johnbaumite, whereas the hydrothermal conditions accelerated the crystal growth of Johnbaumite. This study provides a new idea for the synchronous treatment of toxic heavy metal-containing wastewaters and hazardous solid wastes.

Effects of accelerated carbonation and high temperatures exposure on the properties of EAFS and BOFS pressed blocks

The accelerated carbonation of steel slag can improve its subsequent application as construction materials and can also store CO2 as stable minerals. Due to the differences in the production process, electric arc furnace slag (EAFS) and basic oxygen furnace slag (BOFS) acquire diverse physical and chemical properties, which expected to perform differently upon accelerated carbonation. Especially considering the potential use as green building material, thereby may be subject to fire risk. This research aims at comparing the influence of carbonation temperature, CO2 pressure, and carbonation time on mechanical properties and carbonation efficiencies of EAFS and BOFS pressed blocks, and emphasizing on their performances under elevated high temperatures. Results show that BOFS block has a much better performance than EAFS block, with about twice the compressive strength and CO2 uptake, owing to the higher calcium content and more reactive calcium mineral (portlandite) existed. The strengths of both two types of steel slag pressed blocks were found to increase with the increase of high temperature exposure up to 400 °C due to subsequent hydration reaction induced by elevated temperature. Although a slight decrease of compressive strength can be found after further heating at 600 °C, the residual strength was still comparably higher than that at 20 °C. However, with further increase of heating temperature up to 800 °C, a significant reduction in strength was noticed for both EAFS and BOFS blocks, associated to the decomposition of carbonates phases as the main contributor of bearing-strength within the blocks.

Developing carbon-neutral construction materials using wastes as carbon sink

Developing ecofriendly and low-carbon construction materials is essential to meet the ambitious target of global net zero emission by 2050. The concept of using wastes as carbon sink is taking advantage of alkaline solid wastes, which are rich in calcium or magnesium as a medium for absorbing carbon dioxide (CO2), and allowing manufacturing thermodynamically stable carbonate minerals for construction applications. Today, the major practical and successful applications of CO2 in the construction industry are through accelerated carbonation of granulated aggregates and precast concrete blocks manufactured with different proportions of calcium-rich waste materials. CO2 is also used as an activator in speciality nonhydraulic carbonate-binders or directly injected (in a liquid form) into fresh ready-mix concrete to produce a construction material with higher strength and lower carbon footprint. In addition, accelerated carbonation has become a promising approach to improve the quality of crushed concrete waste, and can be reused in new concrete to attain a sustainable concrete life cycle. In this paper, the progress in academic research of using CO2 in wastes and cement-based products as well as the key advantages and limitations related to the large scale application in the construction industry have been discussed in detail.

Stabilization of cadmium in contaminated sediment based on a nanoremediation strategy: Environmental impacts and mechanisms

Nanomaterials have great application potential for the remediation of heavy metal contaminated sediments, but their environmental impacts are still limited. Herein, graphene oxide-supported nanoscale zero-valent iron (GNZVI) was synthesized to explore its role in mediating the immobilization of cadmium (Cd) from contaminated river sediments, with the consideration of the potential impacts on sediment enzyme activities and bacterial community. Compared to NZVI and GO, GNZVI could more effectively promote the transformation of mobile Cd into stable speciation with a maximum residual percentage increasing by 64.82% after 56 days of treatment. The activities of urease, catalase and sucrase were gradually increased and stabilized with the prolongation of treatment time, indicating that the metabolic function of sediments was recovered. 16 S rRNA gene sequencing results confirmed that the application of GNZVI increased the abundance of some Fe(III)-reducing bacteria, further stimulating the bioavailability of organic matter. Additionally, the properties of GO were gradually changed via microbial reduction and finally showed similar properties to rGO. The critical role of rGO as an electrical conductor was to promote the electron transfer process of microbial Fe(III) mineral reduction, which redistributes part of the Fe(III) mineral-associated Cd to more stable secondary iron minerals, thereby further improving the stabilization efficiency of r-GNZVI for Cd.

Biological indicators in the environmental monitoring of gray forest soil of agrosystems

The objective was to monitor the biological indicators to assess the ecological sustainability of gray forest soil, due to the different level of agrotechnical burden on agricultural landscapes. During 10 years of research (2011-2020) the number of bacteria using various forms of nitrogen was continuously decreasing on the background of mineral intensification. The total average pool of active microflora on organomineral and mineral backgrounds in moulboard plowing was 20.1 and 16.1 million CFU g-1 of soil, respectively, during the period of observations. In non-moldboard plowing, the same average pool was 18.8 and 15.9 million CFU g-1. The minimum pool was maintained on a high-intensity mineral background in moldboard plowing, amounting to 14.5 million CFU g-1 of soil. The decrease in the total bacterial number in the soil of mineral backgrounds indicates a deterioration in their ecological stability. The calculated ecological and trophic indices indicate less ecologically stable low-intensity mineral background in moldboard plowing. This variant showed relatively low values of humus accumulation coefficients (Ch = 0.39) and transformation of organic residues into soil organic matter (Ct = 5.4) established at the highest mineralization coefficient (Cm = 1.57). In this soil, mineralization of organic matter prevails, which reduces its fertility and environmental sustainability. On this background, the activity of the studied enzymes was lower than in other variants and in the soil deposits. A set of micromycetes has shown to grow on mineral intensification backgrounds, especially on a high-intensity mineral background, where moldboard plowing was used as the main treatment. The lowest phytotoxicity was noted on a high-intensity organic-mineral intensification background –21.4%. Both microbiological and biochemical parameters represents an informative diagnostic feature of the ecological state of agrolandscapes. They ensure an objective assessment of the efficiency and degree of agrotechnical burden, predicting a decrease in environmental sustainability on mineral intensification backgrounds.

Thermally Induced Bentonite Alterations in the SKB ABM5 Hot Bentonite Experiment

Pilot sites are currently used to test the performance of bentonite barriers for sealing high-level radioactive waste repositories, but the degree of mineral stability under enhanced thermal conditions remains a topic of debate. This study focuses on the SKB ABM5 experiment, which ran for 5 years (2012 to 2017) and locally reached a maximum temperature of 250 °C. Five bentonites were investigated using XRD with Rietveld refinement, SEM-EDX and by measuring pH, CEC and EC. Samples extracted from bentonite blocks at 0.1, 1, 4 and 7 cm away from the heating pipe showed various stages of alteration related to the horizontal thermal gradient. Bentonites close to the contact with lower CEC values showed smectite alterations in the form of tetrahedral substitution of Si4+ by Al3+ and some octahedral metal substitutions, probably related to ferric/ferrous iron derived from corrosion of the heater during oxidative boiling, with pyrite dissolution and acidity occurring in some bentonite layers. This alteration was furthermore associated with higher amounts of hematite and minor calcite dissolution. However, as none of the bentonites showed any smectite loss and only displayed stronger alterations at the heater–bentonite contact, the sealants are considered to have remained largely intact.

Quantification of Carbon Cycling in a Large Aquifer Using Reactive Transport Modelling

Continental scale aquifers can store significant amounts of carbon as a result of immense water volumes, substantial concentrations of dissolved inorganic carbon (DIC) and its reactions with a matrix, thus contributing the global carbon storage and cycle. However, concentration of dissolved solutes may vary significantly over distances, which causes interpretative challenges and difficulties in process quantification. This occurs in the Guarani Aquifer System in South America, which is a subject of extensive research due to a significant strategic role in water supply. Dissolved CO2is expected to dissociate and undergo reactions with aluminosilicate minerals, but it is unknown how much DIC may get immobilised in the aquifer. To quantify the processes, we performed reactive transport modelling which combines hydrological and geochemical information followed by global sensitivity analysis. We show that more than a half of the infiltrated CO2may be consistently precipitated as CaCO3. The DIC concentrations across the aquifer depend primarily on the input carbon concentrations and the plagioclase hydrolysis rate, while other parameters including hydraulic conductivity, recharge rate and mineral stability are of the minor importance. We present how advanced modelling techniques may be used to interpret and quantify processes controlling water quality in continental scale groundwater systems.

MP33-14 EFFICACY OF LOW INTENSITY ULTRASOUND-EXPOSED MAGNETOSOMES IN THE TREATMENT OF PROSTATE CANCER IN A XENOGRAFT MURINE MODEL

You have accessJournal of UrologyProstate Cancer: Basic Research & Pathophysiology I (MP33)1 Sep 2021MP33-14 EFFICACY OF LOW INTENSITY ULTRASOUND-EXPOSED MAGNETOSOMES IN THE TREATMENT OF PROSTATE CANCER IN A XENOGRAFT MURINE MODEL Cynthia El Hedjaj, Eric Barret, Imene Chebbi, and Edouard Alphandery Cynthia El HedjajCynthia El Hedjaj More articles by this author , Eric BarretEric Barret More articles by this author , Imene ChebbiImene Chebbi More articles by this author , and Edouard AlphanderyEdouard Alphandery More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002042.14AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: To ablate prostate tumors by intra-tumoral injection of magnetosomes and moderate ultrasound heating in a preclinical setting. METHODS: Nanoparticles used in this study were magnetosomes extracted and purified from magnetotactic bacteria. The resulting pure endotoxin free iron oxide minerals were coated with carboxy-methyl-dextran to yield stable coated magnetosome minerals (M-CMD). Treatment efficacy was tested on 4 groups of 10 mice each, bearing PC3-Luc tumours of ∼100 mm3. In vivo experiments followed the Charles Darwin ethical guidelines. Mice received intra-tumoral injection of isotonic solution (group 1), 3 µg per mm3 of tumour of M-CMD (group 2), the same injection of magnetosome as in group 2 followed by 10 sessions of 10 min (3 sessions per week), using a power of 1 W/cm2 and a frequency of 1 MHz (group 3), isotonic solution followed by the same sessions as in group 3 (group 4). Tumour growth after treatments was monitored by measurements of tumour volumes with a calliper and of tumour bioluminescence intensity (BLI). Histological analysis was carried out using Hematoxylin & Eosin/Pearl staining on tissues located in the region of the initial tumour following the various treatments. RESULTS: In group 3 mice, each session of ultrasound application led to an average tumour temperature of 45 °C during 8 minutes. The tumour volume decreased to 0 mm3, becoming un-palpable, and tumour BLI was undetectable 15 days following M-CMD administration. No tumour re-growth was observed during the 45 following days, suggesting full disappearance of the treated primary tumour. Histological analysis of collected tissues after the hyperthermia sessions revealed magnetosome cellular internalization, tumour cell apoptosis and necrosis, and an increase in the percentage of dead tumour cells with increasing number of hyperthermia sessions. In groups 1 and 2 not exposed to ultrasounds, tumours grew rapidly and mice had to be euthanized within one month following isotonic solution/M-CMD injection. In group 4 mice that had the same ultrasound sessions as in group 3 mice without M-CMD injection, a partial anti-tumour activity was observed. The treatment could not prevent tumour re-growth as in group 3. No major side effects were noted in the 4 groups. CONCLUSIONS: Intra-tumoral magnetosomes injection heated to a moderate temperature (45°) by low intensity ultrasounds is a safe and effective treatment of prostate cancer in a murine model. This technique appears promising for clinical applications since it is efficient on mice, relies on cheap and easy to use ultrasound device without a high level of focalisation. Source of Funding: Nanobacterie- 36 boulevard Flandrin, 75016 PARIS © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e612-e612 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information Cynthia El Hedjaj More articles by this author Eric Barret More articles by this author Imene Chebbi More articles by this author Edouard Alphandery More articles by this author Expand All Advertisement Loading ...

MP33-19 TREATMENT OF PROSTATE CANCER USING LASER-IRRADIATED MAGNETOSOMES: A PRE-CLINICAL STUDY

You have accessJournal of UrologyProstate Cancer: Basic Research & Pathophysiology I (MP33)1 Sep 2021MP33-19 TREATMENT OF PROSTATE CANCER USING LASER-IRRADIATED MAGNETOSOMES: A PRE-CLINICAL STUDY Cynthia El Hedjaj, Eric Barret, Imene Chebbi, and Edouard Alphandery Cynthia El HedjajCynthia El Hedjaj More articles by this author , Eric BarretEric Barret More articles by this author , Imene ChebbiImene Chebbi More articles by this author , and Edouard AlphanderyEdouard Alphandery More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002042.19AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: To develop a prostate cancer treatment using laser irradiated bio-synthesized coated iron oxide minerals. METHODS: Nanoparticles used in this study were magnetosomes synthesized by magnetotactic bacteria, extracted and purified from these bacteria. The resulting pure endotoxin free iron oxide minerals were coated with carboxy-methyl-dextran to yield stable coated magnetosome minerals (M-CMD). In vivo experiments followed the Charles Darwin ethical guidelines. Treatment efficacy was tested on 4 groups of 10 mice bearing PC3-Luc tumours of∼100 mm3. Mice received isotonic solution (group 1), 30 µg per mm3 of tumour of M-CMD (group 2), the same condition as in group 2 followed by 10 sessions of 10 minutes of laser radiation of intensity 1.5 W/cm2 and excitation wavelength 808 nm (group 3), isotonic solution followed by the same irradiation as in group 3 (group 4). The evolution of the tumour following treatments was followed by measurements of tumour volumes with a calliper and of tumour Bioluminescence intensity (BLI). Histological studies were carried out using Hematoxylin-Eosin/Pearl staining on tissues located in the region of the initial tumour following the various treatments. RESULTS: In group 3, each session led to a temperature of 45°C for 10 minutes. In 50% of mice belonging to group 3, tumour volume decreased to 0mm3, tumour became un-palpable, and tumour BLI signal was undetectable 12 days following M-CMD administration. No tumour re-growth was observed during the 48 following days, suggesting full disappearance of the treated primary tumour for 50% of the mice in group 3. Histological analysis of tissues collected after the different hyperthermia sessions revealed magnetosome cellular internalization, tumour cell apoptosis and necrosis, and an increase in the percentage of dead tumour cells with increasing number of hyperthermia sessions. By contrast, in all other groups, tumours grew rapidly, and mice had to be euthanized within one month following isotonic solution/M-CMD injection. CONCLUSIONS: We present an efficient and safe method of prostate tumour treatment, which yields full tumour disappearance by exposing natural coated iron oxide minerals called magnetosomes to moderate tumour heating under laser radiation. Magnetosomes were selectively heated due to a coupling between magnetosome surface plasmon waves and laser light, hence minimizing laser heating outside of the magnetosome region, i.e. within the healthy tissues surrounding the tumour, limiting the risk of side effects. Source of Funding: Nanobacterie 36 bd Flandrin- 75016 PARIS © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e614-e614 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information Cynthia El Hedjaj More articles by this author Eric Barret More articles by this author Imene Chebbi More articles by this author Edouard Alphandery More articles by this author Expand All Advertisement Loading ...

Partial Deoxygenation and Dehydration of Ferric Oxyhydroxide in Earth's Subducting Slabs

AbstractThe thermal stability of hydrous minerals in Earth's deep interior is key to understanding the evolution and physicochemical states of the planet. The recently discovered pyrite‐type (Py) FeO2Hx (x ≤ 1) phase, which can be transformed from α/ε‐FeOOH at ∼80 GPa, is believed to be a crucial candidate in transporting water and hydrogen to the lowermost mantle through subducting slabs. Here, we examined the stability and decomposition behavior of FeOOH through a set of shock‐recovery experiments up to ∼70 GPa and ∼2,750 K. Our results show that FeOOH partially decomposes to iron oxides Fe2O3 and Fe3O4 at 35–70 GPa and 1,150–2,750 K, which indicates that H2O and O2 are released during the decomposition of FeOOH in subducting slabs. The released H2O and O2 may have altered the physical and chemical properties of the surrounding mantle and contributed to the oxidation of surface Earth.

Surface Charge Measurements with Scanning Ion Conductance Microscopy Provide Insights into Nitrous Acid Speciation at the Kaolin Mineral-Air Interface.

Unique surface properties of aluminosilicate clay minerals arise from anisotropic distribution of surface charge across their layered structures. Yet, a molecular-level understanding of clay mineral surfaces has been hampered by the lack of analytical techniques capable of measuring surface charges at the nanoscale. This is important for understanding the reactivity, colloidal stability, and ion-exchange capacity properties of clay minerals, which constitute a major fraction of global soils. In this work, scanning ion conductance microscopy (SICM) is used for the first time to visualize the surface charge and topography of dickite, a well-ordered member of the kaolin subgroup of clay minerals. Dickite displayed a pH-independent negative charge on basal surfaces whereas the positive charge on edges increased from pH 6 to 3. Surface charges responded to malonate addition, which promoted dissolution/precipitation reactions. Results from SICM were used to interpret heterogeneous reactivity studies showing that gas-phase nitrous acid (HONO) is released from the protonation of nitrite at Al-OH2+ groups on dickite edges at pH well above the aqueous pKa of HONO. This study provides nanoscale insights into mineral surface processes that affect environmental processes on the local and global scale.

The Effects of Storage on Nutrient Composition and Mycoflora of Stored Guinea Corn (Sorghum bicolor) Grains

Aims: This research work aims to determine the changes in nutritional (proximate, mineral) composition and mycoflora of Sorghum bicolor grains stored for 5 months in order to determine its fitness in meeting nutritional demand. 
 Study Design: Experimental study design was carried out
 Place and Duration of Study: Department of Microbiology, Ekiti State University, Ado-Ekiti, from February 2017 to August 2018.
 Methodology: The grain was procured from Usi market in Usi-Ekiti. It was further sundried for seven days and stored in an airtight container in the laboratory at room temperature. They were visually examined for external changes on the caryopsis and cultured to determine the spoilage fungi. Mineral and proximate analyses were routinely carried out to determine the changes in nutrient composition. These analyses were carried out monthly for five months to determine the changes in physicochemical properties and mycoflora associated with Sorghum bicolor on storage. Results: During storage, spoilage such as external mouldiness, discoloration, musty odour and progressive depletion of external caryopsis were observed on the grain. Seven species of fungi namely Penicillium glabrum, Aspergillus flavus, Penicillium spp., Fusarium spp., Alternaria spp., Aspergillus niger and Saccharomyces cerevisiae were isolated using a combination of direct plating, dilution and washing method. The colony count of the mycoflora population increased from 6 to 16 spore-forming units per gram. The proximate component comprising ash, moisture, crude protein, fat and fiber content decreased but an increase in carbohydrate content was recorded. A negative Pearson correlation (r = - .990) between crude protein and carbohydrate content was recorded. This was attributed to the presence of resistant starch in Sorghum bicolor and the use of alternative source(s) of carbon for energy by the fungi. The entire mineral component decreased during storage. Copper was the barest mineral while magnesium was the most stable mineral in the stored grain.
 Conclusion: Sorghum bicolor grains contain vital minerals and nutrients. Prolonged storage of Sorghum bicolor increased the mycoflora population and consequently decreased the nutrient composition excluding the carbohydrate component. Some minerals and proximate components of the grain were relatively stable while others experienced pronounced depletion. Nutritionally deficient grains may lead to malnutrition especially in growing animals and human populations were adequate minerals and nutrients are required for rapid growth.

Spatiotemporal variability in groundwater chemistry of a mountainous catchment with complex geologic and climate gradients in south west India

Mountainous catchments are one of the world’s important water sources that sustains a major portion of global population and a rich biodiversity. The groundwater quantity and quality of mountainous watersheds depend generally on the geologic characteristics and climate gradients. Although many groundwater studies have been carried out in the midlands and lowlands of many river basins, not enough focus has been paid to the mountainous catchments of tropical watersheds. Here we report a case study on groundwater quality and controlling factors of a mountainous catchments of the Western Ghats mountain ranges of peninsular India—the Bhavani river basin, which is identified as a testbed for long-term monitoring of the Critical Zone process. A total of 88 water samples were collected seasonally for assessing various physico-chemical parameters, solute contents and scaling properties. Standard methods were followed for the estimation of various hydrochemical parameters in the open and borewell samples. The results of the study revealed that higher pH and Total Dissolved Solids (TDS) are noticed in the talc-tremolite dominated central zone whereas low values are recorded in the charnockite dominated areas. The major cations in the water samples are of the order Ca2+ > Mg2+ > Na+ > K+ and the anions are of the order HCO3− > Cl− > SO42−. The content of Cl− shows higher values in areas close to agricultural/settlement areas. An overall evaluation shows that the hydrochemistry of groundwater in the study area is influenced by both silicate and carbonate weathering. Mineral stability indices computed for the groundwater reveal that about 52% of the samples are supersaturated with carbonate minerals and often exhibit scaling due to solute overloading. Saturation Index and mineral stability diagram also support that the incongruent dissolution of aluminosilicate minerals (silicate weathering) is an important hydrochemical process controlling the chemistry of groundwater. Langelier saturation index (LSI) and Puckorius scaling index (PSI) show that a significant number of open well and borewell samples exhibit scaling tendency. Among the contributing factors that determine water quality of groundwaters, chemical weathering and anthropogenic activities play a significant role.

Organic Stabilization of Extracellular Elemental Sulfur in a Sulfurovum-Rich Biofilm: A New Role for Extracellular Polymeric Substances?

This work shines light on the role of extracellular polymeric substance (EPS) in the formation and preservation of elemental sulfur biominerals produced by sulfur-oxidizing bacteria. We characterized elemental sulfur particles produced within a Sulfurovum-rich biofilm in the Frasassi Cave System (Italy). The particles adopt spherical and bipyramidal morphologies, and display both stable (α-S8) and metastable (β-S8) crystal structures. Elemental sulfur is embedded within a dense matrix of EPS, and the particles are surrounded by organic envelopes rich in amide and carboxylic groups. Organic encapsulation and the presence of metastable crystal structures are consistent with elemental sulfur organomineralization, i.e., the formation and stabilization of elemental sulfur in the presence of organics, a mechanism that has previously been observed in laboratory studies. This research provides new evidence for the important role of microbial EPS in mineral formation in the environment. We hypothesize that the extracellular organics are used by sulfur-oxidizing bacteria for the stabilization of elemental sulfur minerals outside of the cell wall as a store of chemical energy. The stabilization of energy sources (in the form of a solid electron acceptor) in biofilms is a potential new role for microbial EPS that requires further investigation.

Validation and analysis of the geographical origin of Angelica sinensis (Oliv.) Diels using multi-element and stable isotopes.

BackgroundPlace of origin is an important factor when determining the quality and authenticity of Angelica sinensis for medicinal use. It is important to trace the origin and confirm the regional characteristics of medicinal products for sustainable industrial development. Effectively tracing and confirming the material’s origin may be accomplished by detecting stable isotopes and mineral elements.MethodsWe studied 25 A. sinensis samples collected from three main producing areas (Linxia, Gannan, and Dingxi) in southeastern Gansu Province, China, to better identify its origin. We used inductively coupled plasma mass spectrometry (ICP-MS) and stable isotope ratio mass spectrometry (IRMS) to determine eight mineral elements (K, Mg, Ca, Zn, Cu, Mn, Cr, Al) and three stable isotopes (δ13C, δ15N, δ18O). Principal component analysis (PCA), partial least square discriminant analysis (PLS-DA) and linear discriminant analysis (LDA) were used to verify the validity of its geographical origin.ResultsK, Ca/Al, δ13C, δ15N and δ18O are important elements to distinguish A. sinensis sampled from Linxia, Gannan and Dingxi. We used an unsupervised PCA model to determine the dimensionality reduction of mineral elements and stable isotopes, which could distinguish the A. sinensis from Linxia. However, it could not easily distinguish A. sinensis sampled from Gannan and Dingxi. The supervised PLS-DA and LDA models could effectively distinguish samples taken from all three regions and perform cross-validation. The cross-validation accuracy of PLS-DA using mineral elements and stable isotopes was 84%, which was higher than LDA using mineral elements and stable isotopes.ConclusionsThe PLS-DA and LDA models provide a theoretical basis for tracing the origin of A. sinensis in three regions (Linxia, Gannan and Dingxi). This is significant for protecting consumers’ health, rights and interests.