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Re and Os are relatively enriched in organic-enriched sedimentary rocks under an anoxic environment due to their organophilic property, and the seawater Os isotopic composition is recorded during the deposition of sedimentary rocks. Under certain geological conditions, the Re and Os in organic-enriched sedimentary rocks will transfer to oil-gas reservoir samples through the process of hydrocarbon generation. The enrichment mechanism of Re and Os in these carbon-enriched geological samples, such as organic-enriched sedimentary rocks, low-metamorphic sedimentary rocks, lacustrine sediments, coal, and oil-gas reservoir samples is the basis of wide geological applications. Re-Os isotopic system of organic-enriched sedimentary rocks has been applied to directly date deposition ages or stratigraphic boundary ages or oil-gas reservoirs, has been used to provide the occurrence time and explore the mechanism of major geological events, reconstructing paleo-environment, and deducing the evolution of petroleum, which has resulted in many achievements.The accumulation mechanism of Re and Os in organic-enriched sedimentary rocks plays an important role in understanding the geological significance of Re-Os isotopic data obtained from organic-enriched sedimentary rocks. In anoxic seawater, Re and Os are reduced to lower valence states of Re(Ⅳ) and Os(Ⅲ), respectively, and then Re and Os enter into organic-rich sedimentary rocks by combining with organic matter. Re and Os are enriched and fractionated during this process, enabling the Re-Os isotope system of organic-enriched sedimentary rocks to directly determine stratigraphic boundaries and sedimentary ages. The Re-Os isotope system has successfully provided accurate stratigraphic boundary ages of Devonian—Carboniferous, Cambrian—Ordovician, Ordovician—Silurian, Permian—Triassic, middle-upper Triassic, and Jurassic—Cretaceous. Furthermore, the Re-Os isotopic system has unique advantages for the strata lacking biological fossils or volcanic interlayers, which have provided the sedimentary age of the Niutitang Formation black shale in Guizhou province and Doushantuo Formation in South China. During the process of hydrogenous source Os into organic-enriched sedimentary rocks, the relative flux of Os from continental weathering, hydrothermal and cosmic dust was recorded, which was reflected as the initial Os isotopic ratio of sedimentary rocks. The coupling relationship between the variation of Os isotopic ratios, atmospheric oxygen level, crustal weathering degree, glaciation events, meteorite impact events, and Large Igneous Provinces can provide the occurrence time and explore the mechanism of major geological events in the history of the earth. The paleoseawater environment and paleoclimate during sedimentation can be further reduced in multiple dimensions by means of the coordinated variation between Re-Os isotopic data, organic matter accumulation, enrichment degree of redox-sensitive elements, and other geochemical proxies.The behavior of Re and Os in the oil-gas system has always been the focus and difficulty in the research of oil-gas reservoir chronology, which is an important basis for understanding the geological significance and wide application of oil-gas reservoir-related samples. The chemical behavior of Re-Os varies in different stages of hydrocarbon formation and evolution. It has been found that the Re-Os isotope system of source rocks will not be destroyed during the process of hydrocarbon generation, and Re/Os fractionation and redistribution of Re and Os will occur during the process of hydrocarbon expulsion and migration. During the process of deasphaltizing, biodegradation, thermal alteration, thermal cracking and oil-water reaction, the asphaltene in crude oil will change correspondingly, and Re and Os in crude will migrate and fractionate accordingly, which will affect the closure of Re-Os isotope system, and even reset the Re-Os isotope system in crude. The different chemical behaviors of Re and Os in the process of hydrocarbon formation and evolution determine the geological significance of Re-Os isochrones obtained from oil-gas samples.Despite the Re-Os isotope system obtaining many achievements and advances in the application of carbon-enriched geological samples, there are still many crucial problems that need to be solved, which restrict the wide application of the Re-Os isotope system. Through statistical analysis of the Re-Os data (including Re and Os contents, ages and initial Os uncertainty) of carbon-enriched geological samples from different sedimentary ages, it is found that the Re and Os contents of organic-enriched sedimentary rocks are at the level of 10-9-10-12g/g, and the error of the Re-Os isochron age and initial Os isotopic ratio of many samples exceeds 10%, especially the larger error of initial Os data. In the process of Re-Os isotope analysis, the accuracy of initial Os isotopic ratio data will not only be affected by sample content, procedural blank of chemical treatment method, error propagation and amplification during calculation, but also by geological factors in the process of sampling. The accuracy of the Re-Os data of carbon-enriched geological samples restricts the accurate identification of the paleoenvironment, the occurrence time of major geological events, the true source of seawater Os, and the degree of geological process by using the initial Os isotopic ratio and the Re-Os isochron age of organic-enriched sedimentary rocks. Moreover, the error of Re-Os isotopic data in the oil-gas system is larger than that that in the organic rich sedimentary rocks. Studies on Re-Os chemical analysis methods and sampling methods for different types of oil-gas samples are still insufficient, and the fractionation mechanism of Re-Os in the process of hydrocarbon formation and evolution is still unclear. This hinders the further understanding of the chemical behavior of Re and Os, and the geological significance of Re-Os isochron ages during oil-gas evolution. In addition, the lacustrine sediments and coal have more complex material sources, geological processes, and the impact of terrigenous detrital during the formation process that is difficult to obtain effective sedimentary ages by Re-Os isotope dating at present.On the basis of existing Re-Os isotope analysis techniques, improving the Re-Os data quality as much as possible is the key to studying the Re-Os enrichment mechanism of carbon-enriched geological samples, especially exploring the chemical behavior of Re and Os and geological significance of the Re-Os isochron age of the oil-gas system. There are four aspects that can improve the accuracy of Re-Os isotopic data of carbon-enriched geological samples.(1) Sampling methods: In addition to collecting fresh and unweathered organic-carbon geological samples, the deposition rate can be a reference as a sampling interval. This can guarantee the samples have relatively uniform initial Os isotopic value and a wide range of the Re-Os isotopic ratios and can improve the accuracy of the Re-Os isochron and initial Os values. Through different pretreatment, such as mixing for a long time, or extracting with organic reagents improvements to the homogeneity of oil-gas samples and the quality of Re-Os data can be made.(2) Dissolution methods: Except for the traditional H2SO4-CrO3 and reverse aqua regia method, researchers established two dissolution methods which were HNO3-H2O2 and H2SO4-Na2CrO4 to solve the problem of high Re blank of the traditional H2SO4-CrO3 method and improve the accuracy of Re-Os data. As the principle of choosing a suitable dissolution method, the Re and Os content of the samples especially the Os content should be considered first and the method with lower procedural blank should be selected.(3) Enrichment methods: Previous studies presumed that the 185Re/187Re data obtained by acetone-NaOH extraction method and anion resin exchange method were consistent. However, recent studies have confirmed that different enrichment methods can produce Re fractionation. The acetone-NaOH extraction method can obtain more consistent results than anion resin exchange method during Re enrichment. The acetone-NaOH extraction method is recommended for samples with Re content less than 1ng/g and for oil-gas samples.(4) Selection of reference materials: Matrix matched reference materials are very important in monitoring the process, data quality and method accuracy of Re-Os isotope analysis. At present, the main reference materials used are shale and oil shale standard samples (SBC-1, SCo-2 and SGR-1b) of the United States Geological Survey (USGS) and crude standard samples (NIST RM8505) of National Institute of Standards and Technology (NIST). There are also calcareous organic-enriched shales from the USGS and sedimentary rock samples from the Japan Geological Survey. According to the summarized Re-Os data obtained by different dissolution methods, SBC-1, SGR-1b and SCo-2 have relatively uniform Re/Os content and isotope ratio on the whole, which can be used for Re-Os data monitoring of shale and oil shale, respectively. The Re-Os data of calcareous organic-enriched shale standard samples have been reported recently and show good uniformity which have great potential in monitoring Re-Os data. NISTRM8505 has relatively uniform Re-Os isotope ratio and may be more suitable for isotope ratio monitoring.In conclusion, the Re-Os isotope system of carbon-enriched geological samples provides much key information for the determination of sedimentary age, paleomarine environment evolution, occurrence time of major geological events, and oil-gas evolution, which is significant for understanding Earth's history. It is important to improve the accuracy of Re-Os isotope data of carbon-enriched geological samples by different methods to better understand chemical behavior of Re and Os and the geological significance of Re-Os isochron age. Enriching and improving Re-Os analysis methods, databases and reference materials of carbon-enriched geological samples will provide important support for the study of Re-Os enrichment mechanism of carbon-enriched geological samples and its wide application

In order to reveal the mechanical behavior of short concrete columns reinforced with hybrid steel and glass FRP bars, 10 specimens were designed for eccentric compression tests. The effect of eccentricity and load–displacement/strain of the specimens was studied. Test results indicate that the damage process and failure mode of these hybrid RC columns was similar to those in the conventional steel-reinforced concrete columns. The mode of failure for all specimens is characterized as large eccentricity compression failure, and the ultimate bearing capacity of the columns decreases with the increase in eccentricity. However, the impact of the varying axial stiffness ratio between GFRP and steel bars on the bearing capacity can be considered negligible. In addition, based on theoretical analysis, two boundary states for distinguishing failure mode and the formulae for calculating ultimate bearing capacity in different failure modes of eccentrically loaded hybrid RC columns are proposed. The computed results agree well with test results. [ABSTRACT FROM AUTHOR]

Photocatalytic reactions during the daytime, alongside aqueous-phase reactions occurring during both daytime and nighttime, are identified as the two primary processes facilitating the conversion of aerosol iron (Fe) from the insoluble state to the soluble state within the atmospheric environment. This study investigated the levels of total Fe (Fe T) and soluble Fe (Fe S) in PM 2.5 samples collected during daytime and nighttime in Qingdao, a coastal city in eastern China, evaluating the distinctive roles of these two pathways in enhancing aerosol Fe solubility (%Fe S , defined as the ratio of Fe S to Fe T). Under clean and humid conditions, characterized by prevailing sea breezes and a relative humidity (RH) typically above 80 %, an average daytime %Fe S of 8.7 % was observed, which systematically exceeded the nighttime %Fe S (6.3 %). Photochemical conversions involving oxalate contributed to the higher %Fe S observed during daytime. Conversely, in scenarios where air masses originated from inland areas and exhibited slightly polluted, daytime %Fe S (3.7 %) was noted to be lower than the nighttime %Fe S (5.8 %). This discrepancy was attributable to the variations in RH, with nighttime RH averaging around 77 %, conducive to the more efficient generation of acidic compounds, thereby accelerating Fe S production compared to the daytime, when RH was only about 62 %. Furthermore, the oxidation rates of sulfur (SOR) displayed a strong correlation with RH, particularly when RH fell below 75 %. A 10 % increase in RH corresponded to a 7.6 % rise in SOR, which served as the primary driver of the higher aerosol acidity and %Fe S at night. These findings highlight the RH-dependent activation of aqueous-phase reactions and the augmentation of daytime photocatalysis in the formation of Fe S in the coastal moist atmosphere. [ABSTRACT FROM AUTHOR]

Graphite, a nonmetallic mineral composed of carbon, relies on carbon stable isotopes for tracing the material source, growth enrichment and mineralization processes. In this study, we leverage laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) to establish an in situ analysis method with medium resolution (∼5000) for carbon stable isotopes. Two potential in-house graphite reference materials from the Lutang deposit in Hunan Province and the Changshouyuan deposit in Jiangxi Province, China, were prepared using the tableting method. Twenty measurements on each of the two samples indicate relatively homogeneous carbon stable isotope composition with a RSD of uncorrected 13C/12C ratios at approximately 0.030% (LTSM: 0.032%, CSY: 0.027%). Additionally, the laser repetition rate was gradient changed (2–20 Hz) to investigate the influence of concentration effect caused by changes in the signal-to-noise ratio (SNR) on the measurement results. When the SNR > 1.23, 13C/12C-2SE no longer drops significantly. Constructing working curves of the SNR and isotope ratio can correct the concentration effect. No matrix effect was observed between the two graphite samples. A slight matrix effect was observed between graphite and dolomite and a strong matrix effect exists between graphite and calcite. The δ13C analysis of graphite from six different mining areas was conducted, and the LA-MC-ICP-MS results, when corrected using the standard-sample-bracketing (SSB) method and LTSM samples, exhibit reasonable agreement with the δ13C values reported in previous and current studies using IRMS. This study demonstrates the feasibility of in situ measurement of carbon stable isotopes in graphite using LA-MC-ICP-MS, characterized by high efficiency, cost-effectiveness and high spatial resolution. The two types of graphite are suitable to be used as reference materials for in situ measurement of carbon stable isotopes in graphite using LA-MC-ICP-MS. [ABSTRACT FROM AUTHOR]

Photocatalysis reactions occurring during daytime and aqueous-phase reactions during both daytime and nighttime constitute the two primary processes responsible for converting aerosol iron (Fe) from insoluble to soluble forms within the atmosphere. This study investigated the composition of total Fe (FeT) and soluble Fe (FeS) in daytime and nighttime PM2.5 in Qingdao, a coastal city in eastern China, and evaluated the distinctive roles of the two pathways in enhancing the solubility of aerosol Fe (%FeS, the ratio of FeS to FeT). In clean and humid conditions characterized by sea breezes, with relative humidity (RH) prevalently exceeding 80 %, an average daytime %FeS of 8.7 % was observed, which systematically surpassed its nighttime %FeS (6.3 %). In contrast, when the air originated from land regions and was slightly polluted, the daytime %FeS (3.7 %) was noted to be lower than the nighttime %FeS (5.8 %). This discrepancy was attributable to the variations in RH, as the nighttime RH approximated to be 77 %, facilitating the more efficient formation of acidic substances and resulting in faster FeS production than during daytime, when RH was about 62 %. Furthermore, the oxidation rates of sulfur (SOR) and nitrogen (NOR) displayed strong correlations with RH, particularly when RH was below 75 %. A 10 % increase in RH resulted in a 7.6 % increase in SOR and a 7.2 % elevation in NOR, which served as the primary reason for the differences in aerosol acidity and %FeS between daytime and nighttime. These findings highlight the RH-dependent activation of aqueous-phase reactions and the augmentation of daytime photocatalysis in the formation of FeS in the coastal moisture atmosphere. [ABSTRACT FROM AUTHOR]