Abstract:Reliable Sr isotope analysis of carbonate rocks requires effective separation of non-carbonate phases that can bias both radiogenic (R(87Sr/86Sr)) and stable (δ88Sr/86SrSRM987) isotope measurements. While sequential leaching has been evaluated using the R(87Sr/86Sr), the behavior of δ88Sr/86SrSRM987 during this process remains poorly constrained. Here, we systematically investigate the evolution of both radiogenic and stable Sr isotopes across sequential leaching steps in three carbonate reference materials, JLs-1, JDo-1, and NIST SRM 1d. This study reports new δ88Sr/86SrSRM987 data for individual leaching fractions of carbonate reference materials and provides the first sequential leaching–based Sr isotope dataset for NIST SRM 1d, for which both radiogenic and stable Sr isotope data have previously been limited. Early leaching fractions are dominated by surface-adsorbed and exchangeable Sr, whereas later fractions reflect contributions from clay minerals, both of which produce isotopic signatures distinct from primary carbonate phases. Only intermediate fractions yield reproducible Sr isotope compositions representative of primary carbonate minerals. The R(87Sr/86Sr) values obtained from bulk leaching differ from those of the intermediate fractions by more than analytical precision, whereas smaller but detectable effects (~0.03‰) are observed for δ88Sr/86SrSRM987, especially in clay-rich samples. Applying the carbonate-dominated leaching range, representative values of carbonate reference materials are obtained with R(87Sr/86Sr) of 0.707783±0.000028, 0.707386±0.000028, and 0.708008±0.000028, and δ88Sr/86SrSRM987 of 0.252±0.035‰, 0.256±0.035‰, and 0.325±0.035‰ for JLs-1, JDo-1 and SRM 1d, respectively (2SD). These results demonstrate that not only R(87Sr/86Sr) but also δ88Sr/86SrSRM987 are sensitive to phase-specific Sr released during leaching and highlight the necessity of accurate pretreatment for Sr isotope analysis. The dataset and analytical framework presented here expand the application of sequential leaching from Sr isotopes and improve the utility of carbonate reference materials for high-precision isotope studies.

Abstract:Rapid and precise determination of elemental content in soil is significant for precision agriculture and saline-alkali land remediation. Although Laser-Induced Breakdown Spectroscopy (LIBS) offers advantages of rapid, multi-element simultaneous detection, it is prone to issues of insufficient quantitative accuracy and model overfitting under conditions of complex soil matrix interference and small sample modeling, thereby limiting the model's generalization capability. To overcome these limitations, this study developed a quantitative regression model based on a 1-Dimensional Convolutional Neural Network (1D-CNN). This model directly utilises raw LIBS spectra as input, automatically extracting multi-scale spectral features to predict the contents of Ca, Mg, and Na in soil. 10-fold cross-validation results demonstrate that the CNN model performs exceptionally well across both high and low concentration ranges. For high-concentration samples, R2 ≥ 0.972, while for low-concentration samples, R2 ≥ 0.98. This confirms the model's high accuracy and strong generalization capability in quantitative LIBS analysis of small samples. Its overall performance significantly outperforms comparison models such as Random Forest (RF) and Backpropagation Neural Network (BPNN). Further integration with Gradient-weighted Class Activation Mapping (Grad-CAM) enables feature visualisation, confirming that the model's focus regions align with element-specific spectral lines, indicating physical plausibility. This study provides a high-precision, interpretable modeling approach for quantitative LIBS analysis of small-sample native soils.

Abstract:Betel leaf (Piper betel L.) is highly susceptible to severe fungal and bacterial diseases such as leaf rot, collar rot, anthracnose (leaf spot), and bacterial leaf spot, which cause significant yield losses through rotting, spotting, and wilting. Its rich phytochemistry underpins various medicinal properties, while its production supports rural economies in Asia. However, diseases and perishability pose serious challenges to yield and profitability, necessitating improved agronomic practices, disease management, and post-harvest handling to sustain and enhance its global economic contribution. Effective disease management therefore requires early integration of cultural practices along with fungicidal and bactericidal treatments. In the present study, laser-induced breakdown spectroscopy (LIBS) coupled with k-nearest neighbors (KNN) modeling was employed to discriminate between healthy and diseased betel leaves. The discriminative potential of nineteen LIBS emission peaks was evaluated using an interclass distance approach. Among these, the Mg II (279 nm) and Na I (588 nm) emission peaks were identified as the most effective variables for classification. One-dimensional KNN models developed using the spectral intensities of Mg II and Na I achieved classification accuracies of 92% and 96%, respectively. This approach demonstrates a cost-effective and time-efficient alternative to conventional elemental analysis techniques, enabling rapid, field-deployable analysis with minimal sample preparation.

Abstract:Apatite is a common accessory mineral in U–Pb geochronology and provides valuable constraints on magmatic evolution, orogenic processes, and basin thermal histories. However, its generally low U concentrations and high common Pb contents have limited its broader application. The long-term stability of matrix-matched reference materials and the reliability of common Pb correction are critical factors controlling data quality. Here, we present in situ U–Pb data obtained by LA–SF–ICP–MS for a suite of widely used apatite reference materials, including NW-1, McClure Mountain, Emerald, Durango, Otter Lake, MAD, AP1 and AP2, covering an age range from ~1157 to 32 Ma. Their long-term stability and homogeneity are evaluated based on analytical results over the past five years. Using real reference materials with contrasting common Pb contents, we further assess the influence of common Pb correction using anchored initial Pb compositions with propagated uncertainties. The results show that U–Pb ages for most reference materials are consistent with ID–TIMS certified values or previously published data, with deviations ≤2%, demonstrating their long-term analytical stability. NW-1, characterized by high U concentrations and the lowest common Pb, is recommended as primary reference material, whereas AP1 and AP2 are better suited as secondary reference materials. This study confirms the robustness of the established analytical protocol, clarifies the appropriate application of different apatite reference materials, and provides a practical framework for matrix matching and multi–reference material cross-calibration in in situ apatite U–Pb geochronology.

Abstract:Stibnite is the principal sulfide mineral and the most important ore mineral in antimony deposits worldwide. In situ S and Sb isotope analyses of stibnite are crucial for investigating the genesis of antimony deposits and for deciphering detailed mineralization processes. To obtain reliable in-situ isotopic data, matrix-matched reference materials are essential for correcting instrumental mass fractionation. In this study, two natural stibnite samples (WX34-80 and KKY) were characterized on the basis of their elemental and isotopic compositions. The results demonstrate that both samples are homogeneous in terms of S and Sb contents, as well as their isotopic signatures, and exhibit significantly distinct sulfur isotopic compositions, rendering them highly suitable reference standards for in situ Sb and S isotope analyse using LA-MC-ICP-MS. Based on IRMS measurements, the recommended δ3?SV-CDT values are ?2.17 ± 0.29‰ (2SD, n = 18) for WX34-80 and 10.63 ± 0.38‰ (2SD, n = 18) for KKY. Correspondingly, SN-MC-ICP-MS analyses yield recommended δ123Sbspex values of ?0.33 ± 0.07‰ (2SD, n = 8) for WX34-80 and ?0.29 ± 0.05‰ (2SD, n = 8) for KKY.

Abstract:The Fo content of olivine is a key parameter for understanding the processes of lunar magmatic evolution. However, limited by detection methods, obtaining the Fo content of olivine on the lunar surface has long been confronted with numerous challenges. Traditional methods such as Electron Probe Microanalysis (EPMA) require polishing and sample preparation, making them unsuitable for future in-situ exploration missions. This study employed microscopic infrared spectroscopy, microscopic Raman spectroscopy, and Energy Dispersive Spectroscopy (EDS) to conduct compositional analysis on olivine grains in Chang'e-5 (CE-5) lunar soil samples. We verified the reliability of the infrared spectroscopy Reststrahlen Band (RB) characteristic peak position method and the Raman spectroscopy main peak shift method for the quantitative inversion of olivine Fo content by comparative analysis. Furthermore, the Fo contents derived from the three analytical techniques exhibit systematic deviations, reflecting differences in their respective technical principles and information depths. The low Fo contents suggest that the basalts at the CE-5 landing site have undergone intense crystallization differentiation, while the coexistence of olivines with distinct compositions may stem from magma mixing events. Not only does this study deepen the understanding of the magmatic history of CE-5 samples, but the spectroscopic methods validated herein also enable the systematic acquisition of olivine Fo contents on the lunar surface during the future Chang'e-7 mission, through a combination of orbiter-based infrared surveys and lander-based high-precision Raman detection, thereby providing a novel approach for in-depth studies of lunar magmatic evolution.

Abstract:Despite significant advances in analytical techniques, quantitative in situ characterization of silver nanoparticles (AgNPs) in biological systems—particularly regarding the dynamic balance between ionic and particulate silver—remains a major challenge. This study reveals that the dissolution behavior of AgNPs strongly depends on particle size and the surrounding biological medium. For example, 50?nm PVP-coated AgNPs exhibited significantly greater dissolution than 75?nm particles in both aqueous solution and DMEM medium. In aqueous environments, over 95% of silver from 50?nm NPs existed as ionic silver, compared to only about 38% from 75?nm NPs. In DMEM, a dynamic equilibrium was established, characterized by the concurrent dissolution of primary particles and the formation of new particulate species, leading to continuous fluctuations in particle number and ionic silver concentration over time. After 48?h of incubation, the released ionic silver accounted for approximately 38.4% from 50?nm particles and 26.2% from 75?nm particles. Chemical speciation analysis via synchrotron radiation-based X-ray absorption near edge structure (XANES)spectroscopy further demonstrated that intracellular silver underwent progressive transformation from the original AgNPs into Ag?S nanoparticles, reaching a conversion ratio of 61.9% at 12?h, along with minor formation of AgCl. This transformation was closely linked to the acidic intracellular milieu and interactions with biological ligands. Although no marked cytotoxicity was observed within the first 24?h of exposure, the gradual intracellular accumulation of transformation products, particularly Ag?S nanoparticles, eventually led tomild cytotoxic effects. These findings collectively underscore that the biological impact of AgNPs is fundamentally governed by their intracellular chemical transformation dynamics.

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Abstract:The main analytical challenges during multi-element analysis of petroleum product are related to the difficulties of sample introduction into the excitation and ionization sources and significant spectral matrix effects. The method of analysis of samples of the petroleum products by two-jet plasma optical emission spectrometry (TJP-OES) is proposed. The innovation lies primarily in application of TJP-OES for viscous organic samples (motor oil and heavy fuel oil), associated sample preparation strategy, optimized drying protocol and the demonstration of performance for a wide range of elements in challenging matrices. The proposed approach to sample preparation and measurement is dilution of the samples by organic solvent (kerosene) with subsequent drying on the graphite powder under IR lamp and TJP-OES analysis of mixture of graphite powder and the analyzed sample. This approach allows perform analysis of the petroleum products without the use of non-standard sample injection systems into atomization sources or labor-intensive sample preparation procedures. The limits of detection (LODs) of the analytes ranged from 10-6 to 10-3 % wt for 29 trace elements are achieved. Recovery values were from 70 to 130 % are obtained during ?spike? experiment. Accuracy of proposed method was confirmed by comparison the results of analysis of the petroleum products by TJP-OES and optical emission spectrometry with inductively coupled plasma (ICP-OES). Thus, the applicability of the TJP-OES method for multi-element analysis of samples of the petroleum product is demonstrated.

Abstract:Studying the asymmetric spatial effects of LIBS is crucial for enhancing defect spectral detection accuracy in metal additive manufacturing (AM). A parallel wall cavity was used to simulate asymmetric conditions of crack defects, with the distance between the ablation point and the left wall (DAPLW) systematically varied. Experimental conditions were established for both symmetric (DAPLW = 7 mm) and asymmetric (DAPLW = 1-6 mm) configurations to study the spatiotemporal distribution of plasma under different spatial effects. Results revealed that asymmetric spatial effects significantly influenced the spatiotemporal distribution of plasma, causing more complex fluctuations in spectral intensity and changes in plasma morphology. Under asymmetric spatial effects, plasma showed enhanced spectral intensity at various acquisition delay times (e.g., 7 μs and 13 μs at DAPLW = 4 mm). However, spectral intensity fluctuations also increased, indicated by a higher relative standard deviation (RSD). Additionally, the study examined the impact of various point-wall distance constraints on the plasma’s time evolution and observed a significant shift in the core position of plasma (CPP) (10-22 μs). During this process, the near roundness ratio of plasma (NRRP) value exhibited significant changes (10-13 μs), particularly when the DAPLW was 1 mm. It decreased from a stable value of 0.8 to below 0.1, reflecting notable morphological changes. In contrast, the symmetric space effect and unconstrained plasma behavior remained stable, with spectral intensity changes showing clear regularity and only relatively small alterations in plasma morphology. This indicated that the delay time of the acquisition system is crucial for using LIBS technology to detect defects in metal AM components with asymmetric cavities. Therefore, understanding asymmetric cavity effects enhances plasma behavior knowledge and provides new guidance for improving defect detection accuracy.