Magnetite is a relevant mineral component of asteroids as it has been identified in carbonaceous chondrites, on the surface of asteroid Bennu through remote sensing observations, and in samples ...returned from asteroid Ryugu. However, the effects of space weathering processes on magnetite have not yet been explored. To investigate how this mineral phase responds to space weathering, here we simulate micrometeoroid bombardment and solar wind irradiation of magnetite using pulsed laser and ion irradiation experiments. We performed X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and visible to near-infrared (VNIR) reflectance spectroscopy analyses to characterize the chemical, microstructural, and spectral response of magnetite to simulated space weathering. In addition, we carried out ion impact simulations using the SDTrimSP software to evaluate the calculated response of magnetite to 1 keV H+ and 4 keV He+ ions and compared these results to our XPS and TEM results. Ion irradiation simulated ∼750 years on the surface of asteroid Bennu, with a solar-wind appropriate total H:He fluence ratio (∼24). Within this time, depletion of O was observed with H+ and He+ ion irradiation, with significantly greater change via protons due to the larger fluence, where preferential sputtering promotes the formation of a metallic iron layer at the magnetite surface. This suggests that solar wind ions act as reducing agents on Fe oxides, with a fraction remaining implanted in these phases. Indeed, we observe elongated defects contained in a crystalline rim created by He+ implanted ions in the TEM. Pulsed laser irradiation, analogous to micrometeoroid impacts, generates melts on the surface of the magnetite grains. The impact melts and H+-generated metallic iron rims both result in increased VNIR spectral reflectance, but lower fluence He+ implantation has no significant spectral effect. These results suggest that space weathered magnetite could contribute to bright regions detected in remote sensing analyses of the Ryugu and Bennu surfaces by the Hayabusa2 and OSIRIS-REx missions and will contribute to the identification and interpretation of space weathered magnetite in returned samples retrieved from both asteroids.
•Surface melts formed as result of pulsed laser irradiation.•1 keV H+ irradiation produced a ∼35 nm thick Fe-metallic rim on magnetite.•Elongated defects were developed in the magnetite irradiated with 4 keV He+ ions.
Ultrahot Jupiters are a type of gaseous exoplanet that orbit extremely close to their host star, resulting in significantly high equilibrium temperatures. In recent years, high-resolution emission ...spectroscopy has been broadly employed in observing the atmospheres of ultrahot Jupiters. We used the CARMENES spectrograph to observe the high-resolution spectra of the dayside hemisphere of MASCARA-1b in both visible and near-infrared. Through cross-correlation analysis, we detected signals of Fe I and Ti I . Based on these detections, we conducted an atmospheric retrieval and discovered the presence of a strong inversion layer in the planet’s atmosphere. The retrieved Ti and Fe abundances are broadly consistent with solar abundances. In particular, we obtained a relative abundance of Ti/Fe as −1.0 ± 0.8 under the free retrieval and −0.4 −0.8 +0.5 under the chemical equilibrium retrieval, suggesting the absence of significant titanium depletion on this planet. Furthermore, we considered the influence of planetary rotation on spectral line profiles. The resulting equatorial rotation speed was determined to be 4.4 −2.0 +1.6 km s −1 , which agrees with the rotation speed induced by tidal locking.
The effective mineral absorption and bioreduction were considered as two preferred processes to alleviate the bioavailability and toxicity of toxic trace metals. In this study, the bioreduction of ...hexavalent chromium (Cr(VI)) on goethite (FeOOH) in the presence of Pseudomonas aeruginosa (P. aeruginosa) was investigated with different environmental factors, including carbon source concentrations, pH, temperature and initial Cr(VI) concentrations. The characterization of FeOOH–P. aeruginosa indicated that P. aeruginosa was surrounded by FeOOH, which could provide the essential iron for bacterial growth and reduce Cr(VI) to Cr(III). The optimal experimental conditions for Cr(VI) (initial concentration: 35 mg L−1) absorption (∼46%) and bioreduction (∼54%) involved a temperature of 45 °C and pH of 5.5. Meanwhile, extracellular polymeric substances (EPS) secreted by P. aeruginosa and its functional groups played important roles in the reduction of Cr(VI). They could reduce Cr(VI) to Cr(III) and transform to Cr(OH)3 or Fex-Cr(1-x)(OH)3 precipitation. These results of this study are of significant importance to better understand the environmental geochemical behavior of Cr(VI) with the interactions between soil minerals and microorganisms.
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•Goethite can reduce the toxicity of Cr(VI) to Pseudomonas aeruginosa; .•Extracellular Polymeric Substances play an important role in Cr(VI) reduction.•The reduction products of Cr(VI) by goethite-Pseudomonas aeruginosa complexes mainly exist as metal complexes.
Abstract
Asuka (A) 12325 is the first poikilitic shergottite having a depleted pattern in light rare earth elements (REE). Compared with known poikilitic shergottites, A 12325 has smaller but more ...abundant pyroxene oikocrysts with remarkable Fe‐rich pigeonite rims, indicating that A 12325 cooled relatively faster at a shallower part of the crust. The redox condition (log
f
O
2
= IW + 0.6‐IW + 1.7) and Fe‐rich chemical compositions of each mineral in A 12325 are close to enriched shergottites. The intermediate shergottites could not form by a simple mixing between parent magmas of A 12325 and enriched shergottites. Although A 12325 contains various high‐pressure minerals such as majorite and ringwoodite, plagioclase is only partly maskelynitized. Therefore, the maximum shock pressure may be within 17–22 GPa. Thermal conduction and ringwoodite growth calculation around a shock vein revealed that the shock dwell time of A 12325 is at least 40 ms. The weaker shock pressure and longer shock dwell time in A 12325 may be attained by an impact event similar to those of nakhlites and Northwest Africa (NWA) 8159. Such a weak shock ejection event may be as common on Mars as a severe shock event recorded in shergottites. Alteration of sulfide observed in A 12325 may imply the presence of magmatic fluid in its reservoir on Mars. A 12325 expands a chemical variety of Martian rocks and has a unique shock history among poikilitic shergottites while A 12325 also implies that poikilitic shergottites are common rocks on Mars regardless of their sources.
Data for the solubility of CuS (reacting to Cu2S), Cu, and bornite + chalcopyrite + pyrite (reacting to Cu-Fe-S solid solution) in H2O + NaCl fluids were determined in situ using ...synchrotron-radiation X-ray fluorescence (SR-XRF) spectroscopy. The aqueous Cu concentrations ranged between 25 ppm at 500 °C, 320 MPa, 0.5 m NaCl and 760 ppm at 500 °C, 310 MPa, 4.78 m NaCl, increased with temperature along an isochore and with NaCl molality, and decreased with pressure. The X-ray absorption near edge structure (XANES) spectra of the fluid from dissolution of CuS or Cu in H2O + NaCl at 500 °C are nearly identical with published spectra of CuCl2−(aq), but differ significantly from reported spectra of Cu(I) in Cl-free hydrosulfide solutions.
Raman spectra of H2O + HCl ± NaCl fluids reacted with CuS or, for comparison, metallic Cu were measured at temperatures to 600 °C and pressures to 2 GPa to test if this technique can provide additional information on the complexation of Cu(I) and on the solubility of copper in hydrothermal fluids. These spectra showed that CuCl2−(aq) was the most abundant Cu(I) species at all conditions. In addition, CuCl32−(aq) was observed at high HCl concentrations, but the Raman spectra provided no convincing evidence for Cu(I) complexation with H2S or S3− (HS−(aq) was below detection in these acidic fluids). Generally, there was an increase in the sum of the integrated intensities of the bands assigned to Cu complexes with increasing HCl concentration, and a decrease if sulfide was present. At all fluid compositions, the intensity of the Raman bands from CuCl stretching vibrations decreased with increasing pressure at constant temperature for single-phase fluids, without formation of additional bands. Based on ab initio modeling, the complexes CuCl2−(aq), Cu(HS)2−(aq), and Cu(HS)Cl−(aq) are not distinguishable by Raman spectroscopy, but the stretching vibration of Cu(I) complexes with H2S should occur at significantly lower wavenumbers.
Overall, the results indicate that Cu(I) is transported predominantly as CuCl2−(aq) in reducing sulfur-free or H2S ± S3−-bearing chloridic hydrothermal fluids. The decrease in the Cu solubility in H2O + HCl ± NaCl ± H2S fluids with increasing pressure without a detectable change in speciation is caused by decrease in the formation constant of CuCl2−(aq) with pressure. Changes in the copper speciation and depressurization can be ruled out as causes for hydrothermal copper ore formation at high fluid densities above the critical density. At this condition, copper ore may precipitate by dilution, cooling in the presence of H2S, increase in pH, and/or an increase in the H2S activity.
•Determined solubility of Cu(I) in H2O + NaCl in situ to 600 °C using XRF spectroscopy.•Isothermal Cu(I) solubility decreases with pressure above critical density of fluid.•Raman spectra show decrease in Cu(I) solubility in presence of H2S.•CuCl2−(aq) is predominating Cu(I) species based on XANES and Raman spectra.•CuCl32−(aq) observed only at very high HCl concentration.
Because ferromanganese oxides can host significant amounts of Ni during the weathering, the Fe- and Mn-oxide are resultantly considered as the important Ni-bearing minerals. However, little is known ...about the role of Mn species to influence the Ni behavior during this process. In this study, we employed the techniques of ICP-MS, XRF, XRD, XAFS (XANES and EXAFS), and μ-XRF to interpret the Ni behavior along a laterite profile in Myanmar. Nickel concentrations in the saprolite developed on peridotites can reach up to 11 wt% Ni mainly because of Ni precipitation as fracture-fillings and thin coatings on joints, which produce a promisingly and importantly economic mineral resource of this territory. In the peridotites, Fe and Mn species predominantly consisted of olivine (96%) and biotite (74%), respectively. Nickel XANES spectra indicated that Ni was primarily hosted by olivine (86%) in the protolith under reduction condition, lizardite (90%) and Ni-bearing goethite (10%) in the lower garnierite vein under strong oxidation condition, and lizardite (37%) and Ni-bearing goethite (63%) in the upper saprolite under medium oxidation condition. Accordingly, minerals of Fe and Mn were progressively oxidized toward Fe3+ and Mn4+, which occurred primarily as Fe3+-bearing goethite and Mn4+-bearing birnessite. The occurrence of Fe- and Mn-oxide plays an important role in Ni species and suggests that birnessite maybe facilitate the formation of Fe oxide precipitations by means of the oxidation of Fe2+ in the olivine to Fe3+ in the goethite. The results are of relevant importance, as it fills a gap in the knowledge of ore-formation processes occurring in Myanmar
Reflectance spectroscopy has great potential to monitor and evaluate soils at large scale; however, its effectiveness in predicting properties from tropical soils still needs to be tested since their ...mineralogy, organic matter levels, and charge and ion adsorption dynamics are different from temperate soils. Also, it is important to assess the most appropriate spectral range for quantification of specific soil property. Therefore, this study aimed to predict physical, chemical, and mineralogical soil properties using vis–NIR (350–2500nm) and mid-IR (4000–400cm−1) spectral libraries and statistically compare their modeling performances. We used 1259 soil samples distributed along four Brazilian States. Soil particle size, chemical analyses including macro and micronutrients, and oxides from sulfuric acid digestion were performed. Vis–NIR reflectance data were obtained by the FieldSpec Pro sensor while mid-IR data were collected using the Nicolet 6700 FT-IR sensor. Support Vector Machine was used as multiple regression algorithm and modeling performance was evaluated by R2, RMSE and RPIQ. This research presented a complete prediction analysis of soil properties important for survey, classification, and fertility management. Models fit very well (0.76≤R2≤0.90 and 2.81≤RPIQ≤5.62) for sand, clay, Al3+, H + Al3+, CEC, clay activity, Fe2O3, and TiO2 predictions, and showed reasonable performance (0.50≤R2≤0.73 and 1.83≤RPIQ≤3.78) for OC, Ca, Mg, SB, V%, m%, pH in H2O, oxides (Si, Al, and Mn), and Cu and Mn (micronutrients). Phosphorus, potassium and some micronutrients (Fe and B) were not reliably quantified (R2≤0.47 and RPIQ≤1.83). For both spectral ranges, performance indices were kept in testing steps, and no atypical distribution pattern was identified by residual analysis. Statistically, mid-IR spectral models showed better performance for 60% of the studied properties. For some oxides (Al, Fe, Ti, and Mn), vis–NIR models were better. Models developed from vis–NIR and mid-IR spectral libraries are effective and useful to quantify properties suggesting soil mineralogy, reactivity, fertility and acidity of tropical Brazilian soils; however, mid-IR is the greatest potential spectral range. The excellent results of clay (0.85≤R2≤0.88 and 3.88≤RPIQ≤5.56) and sand (0.85≤R2≤0.90 and 4.85≤RPIQ≤5.62) modeling prove that at least soil particle size analyses can be efficiently replaced by the reflectance spectroscopy methods.
•Vis–NIR and mid-IR spectroscopy are effective in analyses of tropical Brazilian soils.•Mid-IR data are better than vis–NIR data to model reactivity and acidity of soils.•Properties for soil survey and fertility management are better modeled by mid-IR.•Al, Fe, Ti, and Mn oxides from soil mineralogy are better predicted by vis–NIR data.•Soil particle size analyses can be efficiently replaced by reflectance spectroscopy.
Microplastics (MPs) are an uncontrolled contaminant affecting marine ecosystems. Studying their undesirable effects has been an attractive field for scientists in recent years. This study is the ...first to investigate the uptake and distribution of small microplastics (≤3 μm) from several sites in the Southern Mediterranean coasts. This work primarilyaims to provide a qualitative and quantitative analysis of microplastics in sediments as well as in the seaworms (Hediste diversicolor) from eight sites from the Tunisian coasts using Fourier transform infrared spectroscopy and Raman microspectroscopy. The second aim is to evaluate the potential toxic effects of environmental microplastics using a set of biomarkers such as Catalase, Glutathione-S-Transferase, Malondialdehyde and Acetylcholinesterase. Our findings showed that microplastics (1 mm–1.2 μm) were present in all sediments with its abundance ranging from 129 to 606 items kg−1. Microplastic accumulation in seaworms (3 μm–0.22 μm) was 0.5–3.7 items g−1. The predominant polymer was polyethylene. Results also revealed a significant variation among sites in the parameters associated with oxidative stress. Thus, size abundance of microplastics in seaworms was mainly correlated with oxidative stress biomarkers. Our data should be carefully considered in view of the microplastic presence with several types and sizes in Tunisian coastal sites, their potential toxic effects, and their transfer into food web.
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•Microplastics (<3 μm) were detected in sediment and seaworm from Tunisian coasts.•The majority of microplastics were with size 3-1.2 μm.•Plastic sizes of have a significant impact on their consumption and effects.
•Determining soil CEC is usually cost- and time- consuming.•We explored the potential of fused sensor data (PXRF and Vis-NIR) to predict soil CEC.•Support vector machine regression with a fused ...sensor dataset was the best.•Single sensor data are insufficient to comprehensively characterize soil CEC.
Soil cation exchange capacity (CEC) is a critical property of soil fertility. Conventionally, it is measured using laboratory chemical methods, which involve complex sample preparation and are time-consuming and expensive. Previous studies have investigated nondestructive and rapid methods for determining soil CEC using proximal soil sensors individually, including portable X-ray fluorescence (PXRF) spectrometry and visible near-infrared reflectance (Vis-NIR) spectroscopy. In this study, we examined the potential of the fusing data from PXRF and Vis-NIR to predict soil CEC for 572 soil samples from Yunnan Province, China. The CEC of the samples ranged from 5.42 to 50.25 cmol kg−1. Both partial least-squares regression (PLSR) and support vector machine regression (SVMR) were applied to predict soil CEC with individual sensor datasets and a fused sensor dataset for comparison. The root mean squared error (RMSE), coefficients of determination (R2), and ratios of performance to interquartile range (RPIQ) were used to evaluate the performance of the models. Results showed that: (1) SVMR performed better than PLSR on single sensor datasets and the fused sensor dataset, in terms of RMSE, R2, and RPIQ; and (2) both PLSR and SVMR based on the fused sensor dataset had better predictive power (RMSE = 4.02, R2 = 0.72, and RPIQ = 2.23 in PLSR model; RMSE = 3.02, R2 = 0.82, and RPIQ = 2.31 in SVMR model) than those based on any single sensor dataset. In summary, the fused sensor data and SVMR showed great potential for estimating soil CEC efficiently.
To understand the deep cycle of water, upper mantle water content and distribution between nominally anhydrous minerals (NAMs) and hydrous minerals (e.g., amphibole) must be constrained. We need then ...to understand H behaviour during mantle melting and metasomatism. Major, minor and trace element compositions including water contents were obtained on ten xenoliths of spinel-bearing peridotites from the Ray Pic locality, in the Southern part of the Massif Central (France). The sample suite investigated here is composed of rather fertile lherzolites (89.4≤Fo≤90.8%; 11.3≤cr# in spinel≤21.1%; 0.942≤Ybcpx≤1.90ppm; cpx: clinopyroxene), which can be best explained by batch melting, with degree of melting between 3 and 10%. These xenoliths contain up to 8% modal amphibole. Three groups are defined as a function of the amphibole modal abundance (above or below 1%) and equilibrium temperature (above or below 1000°C). Results show no clear positive correlation between modal metasomatism (amphibole) and incompatible element enrichment in cpx. Trace element compositions in cpx show strong enrichments of the most incompatible elements (e.g., (La/Sm)PM as high as 15.7; PM: normalised to primitive mantle values), but strong negative anomalies of the high field strength elements (e.g., (Th/Nb)PM as high as ~680). Such trace element fractionations are usually ascribed to the so-called carbonatitic metasomatism involving the percolation of small volume melts which are enriched in volatiles. The hydrogen concentrations in cpx range from 203 to 330ppm wt. H2O, in orthopyroxene from 66 to 160ppm wt. H2O and in olivine from 2 to 6ppm wt. H2O. These values are within the common concentration range of other spinel-bearing peridotites. Amphiboles contain 1.9±0.5wt.% of H2O.
The effect of metasomatism on water abundances in NAMs is not straightforward. Hydrous metasomatism (i.e., leading to the crystallisation of OH-bearing amphibole) has no effect on the water content of the co-existing NAMs. This suggests thus that the occurrence of hydrous minerals, such as amphibole, does not systematically imply that the coexisting NAMs are water-rich (saturated). Further, the percolation of volatile-rich small volume melts, which is fingerprinted by the strong enrichment of the incompatible elements, has also no clear effect on the water content of the NAMs. These data are thus difficult to reconcile with the admitted highly incompatible behaviour of H in upper mantle minerals.
•Occurrence of OH-bearing amphibole does not warrant the water-saturation of co-existing NAMs.•Metasomatism by volatile rich melt/fluid has limited effect on the water content of NAMs.•Water content in NAMs can be explained mostly by depletion during melting.•Hydrogen behaviour during melting and metasomatism in NAMs is not similar to La or Ce, but to MREE.
