Driven by glacio-eustatic processes, the Earth has experienced a phase of large-amplitude sea-level change as intensive as any during its history since the Quaternary (Rohling et al., 2014), which has branded profound imprints in marine sediments. For example, with regard to deep-sea sediments, a remarkable feature is the variations in the oxygen isotope records of benthic foraminifera (BF), such as the well-known "LR04 stack" (Lisiecki & Raymo, 2005). Likewise, for sedimentary records on continental shelves, which serve as a link between the land and the deep ocean, sea-level fluctuations over glacial-interglacial timescales (e.g., the cycles in the Earth's orbital eccentricity of ∼100-kyr) are generally expressed as transgression-regression cycles (Shi et al., 2016). Due to their wide and gentle landforms, as well as relatively shallow water depths, continental shelves are much more sensitive to sea-level changes than abyssal regions; even trifling fluctuations in sea-level can give rise to considerable shoreline migration (Yao et al., 2020). Nevertheless, besides the easily identified transgression-regression cycles, it is difficult to trace changes in sea-level over much shorter timescales, which, however, is of great significance to human activities in coastal areas (Yang et al., 2015). This problem is more prominent in relation to sedimentary units with homogenous lithologies, especially for fine-grained sediments which are relatively poor in BF due to high sedimentation rates and

No abstract

Rationale Quantifications of quadruple sulfur isotopic compositions (δ34S, Δ33S, and Δ36S) of sulfur‐bearing compounds in nature are valuable for providing new insights into the Earth's evolution such as the crust–mantle cycle, oxygenation of atmosphere and oceans, and the origin and evolution of early life. SF6‐based isotope ratio mass spectrometry is the most widely used method of quantification, but Δ36S measurements at high precision and accuracy have always been technically difficult due to the low abundance of 36S (~0.01%). In this paper, we identify a major source of isobaric interferences (i.e., contamination in helium carrier gas in the gas chromatography purification step) and propose a simple strategy to solve this problem. Methods An SF6 fluorination and purification system was built. Laboratory SF6 reference gas and international Ag2S standard (IAEA‐S1) were used as reference materials to test our method. Contamination from helium carrier gas (99.999%) was purified by a simple two‐step cryogenic method to allow for accurate and precise measurements of Δ36S using the SF6‐based isotope ratio mass spectrometry method. Results Without proper purification of helium carrier gas, large errors in Δ36S measurements were found. Measured Δ36S values of SF6 with trace contamination from helium were >10‰ higher than expected values. Using a newly developed purification strategy, the difference in Δ36S values of SF6 before and after passing through the gas chromatography is less than instrumental errors (<0.2‰). Our improved method yielded an overall Δ36S precision for IAEA‐S1 of 0.12‰ (n = 6). This precision is comparable to that found by other laboratories around the world. Conclusion Our simple two‐step cryogenic method significantly improved the accuracy and precision of Δ36S measurements and is therefore recommended for future determination of quadruple sulfur isotopic compositions in natural samples.

Emotional research in foreign language learning has bloomed recently, and yet there has been a call for attention to a broader spectrum of emotions experienced by learners of English as a foreign language (EFL). Whilst emotions and self-regulated learning (SRL) are both believed to play important roles in EFL learning, little is known about their interplay. To fill the void, the study intends to map out an overall status quo of Chinese university EFL students’ academic emotions and SRL strategy use and sophisticated interrelationships between them using structural equation modelling (SEM). Findings showed that the Chinese participants demonstrated a medium level of positive emotions, a low level of anger, a medium level of shame and anxiety, and a low to medium frequency use of SRL strategies in English learning. ANOVA results detected gender differences in SRL strategy use, with females outperforming males in using self-evaluation and persistence strategy types, together with grade level influences in anxiety level with seniors feeling less anxious than juniors and sophomores. Furthermore, SEM results suggested that enjoyment had positive relationships with SRL strategy use; anger and shame had negative relationships while anxiety had ambivalent relationships with SRL strategy use. Important implications are discussed.

Sulfur isotope mass-independent fractionation signatures (S-MIF) have been widely found in modern sulfate aerosols. Their mechanistic origins and potential implications for atmospheric sulfate formation chemistry are however poorly understood. Of particular importance is that the mystery of modern sulfate S-MIF hinders precise interpretations of S-MIF in geological sediment and meteorite samples. Here, we examine several proposed origins of modern sulfate S-MIF using a multiple-tracer approach. Quadruple sulfur isotopes of sulfate aerosols collected from Guangzhou, a megacity in South China, were measured along with various chemical and isotopic tracers for high-altitude air masses, biomass burning, and mineral dusts in the same samples. Similar to previous studies, we found that negative Δ36S values in modern sulfate aerosols are linked to combustions, and to a larger extent, to high-temperature processes that may involve symmetry-dependent recombination reactions of sulfur. The origins of Δ33S anomalies widely observed in modern sulfate aerosols remain elusive and require further investigation before we can unambiguously use this proxy to quantify sulfur emission and transformation pathways in the modern atmosphere. From a comparative planetology perspective, we highlight that a complete understanding of S-MIF in modern aerosols is crucial for tracking paleo- and planetary atmospheres by multiple sulfur isotope measurements in Phanerozoic sediments and Martian meteorites because their S-MIF magnitudes are similar.

Pusa village is located in the karst mountain area of Nayong County, Guizhou Province, China. Laoyingyan mountain rock is gently dipping, the upper part consists of hard rock formations, and the lower part is made up of soft rock composed of 3 coal seams. On August 28, 2017, a massive landslide occurred in this area, resulting in 82,3000 m3 of debris, which resulted in significant casualties and brought up the malaise in society. In this paper, the geological conditions and long-term mining activities in the study area are analyzed by field investigation. The base friction tests and numerical models are used to simulate and analyze the failure and deformation process of Pusa collapse to accommodate the research on the deformation and failure mechanism of the slope and provide better prevention and treatment suggestions. The results show that the Pusa collapse can mainly be attributed to unique geological conditions, underground mining activities, and the topography of the slope. The intensified mining activities promoted the development of fractures and cracks in the slope, resulting in unstable upper slopes. The failure process of the Pusa collapse can be summarized into four-stage: the development of goaves roof deformation, the crest of the slope cracks, intensification of deformation, and occurrence of collapse. The upper slope with high strength rock developed crack-toppling failure. Meanwhile, the upper slope with low strength rock developed subside-crack-sliding failure, and those two failures together contributed to the mechanism of Pusa collapse. Slope deformation and failure mechanism can be summarized as subside-crack-toppling-shear sliding type.

No abstract

High-sensitivity measurements of radiosulfur (cosmogenic 35S; half-life: 87.4 days) at natural abundance using ultra-low-level liquid scintillation counter (LSC) methods have been developed and optimized in the last decade, providing new details in space, atmospheric, and hydrological sciences. These LSC methods heavily rely on instruments conventionally equipped with 650 kg lead blocks that passively shield cosmic and environmental background radiation, but this type of instrument is not commercially available anymore, hindering further applications of 35S. To solve this problem, we extended the methods to a new-type LSC equipped with new mathematics-based active shielding techniques (Guard Compensation Technology; GCT). The counting efficiency of the new-type LSC for low-35S activity samples (e.g., natural samples) is low and highly variable because a portion of true signals from 35S decay events was undesirably removed by GCT. We therefore developed a new data processing protocol to determine 35S activities accurately and precisely in the range between ∼1 and ∼13 disintegrations per minute, and its validity was tested by working standards with known 35S activities. As an application example, we measured concentrations of 35S in sulfate aerosols collected in Guangzhou, a megacity in subtropical South China. The obtained values are within the range of previously reported data from various mid-latitude sampling sites. Based on these results, we conclude that our protocol allows the continuing utility of 35S measurements using a new-type LSC for a deeper understanding of the atmospheric sulfur cycle and its influences on the environment, climate, and public health.