Mercury evidence for volcanism driving environmental changes during the protracted Late Ordovician mass extinction and early Silurian recovery

Volcanism has been proposed as the trigger for the environmental perturbations and associated mass extinction during the Ordovician-Silurian (O-S) transition. However, the timing, duration, and intensity of volcanic eruptions during this critical period and their relationships to environmental perturbations and biotic changes remain unresolved. In this study, we use mercury (Hg) concentrations and isotopes from marine sediments in South China to reconstruct the evolution of volcanism from the Late Ordovician to early Silurian. Our results show that strong Hg enrichment coupled with generally near-zero to slightly positive Delta 199Hg values occurred before, during, and after the classically defined Late Ordovician Mass Extinction (LOME), suggesting a significant influx of volcanogenic Hg. The Hg enrichment intervals coincided with global warming, oceanic anoxia, and negative excursions in carbon and sulfur isotopes, suggesting that volcanism drove the environmental perturbations during the O-S transition. The coincidence of Hg enrichment with extinction horizons supports the hypothesis that volcanism may have contributed to LOME. Our study also suggests that volcanism persisted for approximately 3 million years after mass extinction and may have delayed the recovery of marine ecosystems during early Silurian

Biogenic emission as a potential source of atmospheric aromatic hydrocarbons: Insights from a cyanobacterial bloom-occurring eutrophic lake

As important precursors of ozone (O3 ) and secondary organic aerosol (SOA), reactive aromatic hydrocarbons (AHs) have typically been classified as anthropogenic air pollutants. However, biogenic emission can also be a potential source of atmospheric AHs. Herein, field observations in a eutrophic lake were combined with laboratory incubation experiments to investigate the biogenic AH emission. Field work showed that the water-air fluxes of AHs measured at sites with high cyanobacteria abundance could reach an order of magnitude greater than those at sites with low cyanobacteria abundance, suggesting that cyanobacteria could be the important contributor to measured AHs. Laboratory incubation experiments further confirmed the AH emission of cyanobacteria and revealed that the emission could change significantly over the lifespan of cyanobacteria and varied to their growing conditions. By combining field observations and laboratory incubation experiments, it has been suggested that the emission of different AH species from cyanobacteria could be modulated by variable biogeochemical mechanisms and that the biochemical process of toluene could be different from that of other AHs. This study investigates AH emissions from inland aquatic ecosystem and suggests that biogenic emission could be a potential source of atmospheric AHs. (c) 2024 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V

Coupling of sulfate reduction and dissolved organic carbon degradation accelerated by microplastics in blue carbon ecosystems

Microplastics have increasingly accumulated in sulfate- and organic matter-rich mangrove ecosystems, yet their effects on microbially mediated carbon and sulfur cycling in sediments remains poorly understood. In this study, we performed a 70-day anaerobic microcosm experiment to examine the effects of polylactic acid (PLA) microplastics with different sizes on sulfate reduction and dissolved organic carbon (DOC) degradation in mangrove sediments. Our results demonstrated that millimeter-scale PLA (mm-PLA) more effectively enhanced sulfate reduction, sulfur isotope fractionation, reduced sulfide production, and carbon dioxide (CO2) emission compared to micrometer-scale PLA (m-PLA). These results suggested that mm-PLA had a more pronounced impact on the carbon and sulfur cycles. Integrated 16S rRNA gene amplicon sequencing and metagenomic analyses revealed that mm-PLA preferentially enriched key functional microorganisms, including acetate-producing bacteria (e.g., Acetobacteroides), completely oxidizing sulfate-reducing bacteria (e.g., Desulfobacter), and incompletely oxidizing sulfate-reducing bacteria (e.g., Desulfobulbus). These microorganisms exhibited higher abundances and greater genetic potential for carbon metabolism and sulfate reduction under mm-PLA treatment. Their relative abundances showed positive correlations with sulfate reduction rates, sulfur isotope fractionation, and CO2 emission, identifying them as crucial drivers of coupled carbon-sulfur cycling. Furthermore, the synergistic interactions among Acetobacteroides, Desulfobacter, and Desulfobulbus facilitated the oxidation of sediment-derived DOC, highlighting significant implications for carbon sequestration in blue carbon ecosystems

Frequency of Synoptic-Scale Precipitation Events Recorded by Daily Resolved δ<SUP>18</SUP>O of Land Snail Shells

Land snails exhibit the potential for capturing synoptic-scale precipitation events through the delta O-18 records of their shells (delta(18)Oshell), but the application is hindered by the absence of a practical methodology for tracking these events. Here, we developed a statistical methodology to track the synoptic-scale precipitation events from daily resolved snail body fluid delta O-18 (delta O-18(BF)) record. We further tested and verified our approach using daily resolved delta(18)Oshell records of modern Cathaica fasciola from the Chinese Loess Plateau (CLP). The reconstructed 3-day-timescale precipitation events frequencies using first derivations of delta 18OBF and delta 18Oshell shows strong agreement with instrumental data (>85% detection accuracy). The strong correlation between precipitation days in snail-growing-season and annual precipitation amounts across the CLP also permits the reconstruction of synoptical precipitation frequency for investigating the interannual variability of precipitation. Our study paves the avenue in paleoweather study, enabling quantitative reconstructions of past synoptic-scale precipitation events

On-land evidence for subduction of the proto-South China Sea beneath northern Borneo and tectonic reconstruction of Southeast Asia during the early Permian-Oligocene

The development of the Mesozoic proto- South China Sea was closely related to the tectonic evolution of the Tethys and Paleo-Pacific domains and may have been a key driving mechanism for the opening of the South China Sea. Despite its importance, direct geologic evidence for the proto-South China Sea remains limited, and its development is debated between two primary models: intraoceanic subduction and oceanic-continental subduction. Here, we present petrographic, geochronologic, and geochemical data from tuffs and Eocene-Pliocene sedimentary records in Sabah, northern Borneo. The results reveal that these tuffs, formed ca. 28 Ma, possess geochemical characteristics indicative of oceanic arc origins. Combined with changes in sediment provenance since the Oligocene and various subduction timelines around Borneo, we suggest that these tuffs resulted from the subduction of the proto-South China Sea. This oceanic arc, along with Eocene mid-ocean-ridge-like mafic rocks in Sabah, indicates that a younger oceanic basin had formed within the proto-South China Sea. This aligns with observations in Palawan, Philippines, illustrating the transition from an oceanic spreading center to a subduction zone and indicating the proto-South China Sea extended from eastern Sabah to Palawan. In addition, inherited zircons (ca. 280 Ma) in the tuffs exhibit geochemical signatures typical of continental arcs. Combined with the Permian-Cretaceous arc-related igneous rocks in Southeast Asia, this suggests that southern Sabah was part of the Paleo-Tethys Ocean before integrating into the Paleo-Pacific domain since the Triassic. By shedding light on these processes, our research provides critical insights into the existence, extent, and evolution of the proto- South China Sea and reconstructs the multiphase transitions between different tectonic domains in Southeast Asia

Electrochemically enhanced adsorption of perfluorooctanoic acid (PFOA) on CuO-CNTs composite electrodes

With the intensification of the global freshwater crisis, seawater desalination has emerged as a vital approach for obtaining freshwater resources. However, the presence of persistent pollutants in seawater poses new challenges to the desalination process. Among these, perfluorooctanoic acid (PFOA) has garnered significant attention due to its stability, bioaccumulative nature, and potential toxicity. While multi-walled carbon nanotubes (CNTs) exhibit high adsorption capacity, their effectiveness in PFOA removal remains limited. To address this, we synthesized copper oxide-modified CNTs (CuO-CNTs) and fabricated electrodes using a straightforward coating technique for electrochemically assisted PFOA adsorption. Our results demonstrate that CuO-CNTs electrodes achieved a 1.26-fold increase in the initial electrosorption rate and a 2.04-fold improvement in removal efficiency, reaching 89.25 % at 0.6 V compared to CNTs. The maximum electrosorption capacity also increased 1.69- fold at 0.6 V relative to 0 V. Furthermore, studies on adsorption mechanism and various ion strengths/ ion types/ pH provide important references for optimizing electrosorption technology in desalination. These findings contribute to improving the efficiency and effectiveness of contaminant removal during desalination, thereby enhancing the quality of desalinated water

Generation of the 2022 earthquake swarm in intersection of four geological units in the seismic experimental Site, southwest China

Three adjacent and successive earthquakes with magnitude over 6.0 in the seismic experimental site, southwest China in 2022 were investigated mainly based on multi-disciplinary observation data combined with regional geology. The abnormal variations of GPS horizontal velocity field and cross-fault baselines, seismic activity, and also fluids geochemistry presented strong cascade and pre-, post-, and co-seismic consistency, suggesting these events could belong to one sequence of earthquakes motivated by a lateral expansion of the Tibetan Plateau. Based on comprehensive analysis, the progressive regional localization of deformation and strain in the intersection of the four geological units, subjected to the lateral expansion of the Tibetan Plateau due to the remote action of the India-Eurasia collision, was unveiled to be the tectonic driver controlling the earthquake swarm, and a "south-north-south cascade" model was proposed for the generation process of the earthquake sequence. According to this model, the possible southward stain transfer in the southeastern margin of the Tibetan Plateau should be considered for potential strong earthquakes in the future. Although this study is special for the seismic experimental site, China, it could be inferred that similar processes might be probable elsewhere, thus, prospective transfer direction forecasting for coming seismic activity could be envisaged in some intersections of multiple geological units

Attribute Reduction in a Hybrid Decision Information System Based on Fuzzy Conditional Information Entropy Using Iterative Model and Matrix Operation

Attribute reduction of hybrid decision information systems (HDISs) is a significant research area within the field of machine learning. Due to the presence of nominal attributes, it is difficult to accurately measure the distance between objects in HDISs, which often results in poor attribute reduction for these systems. Rough set theory (RST) is a crucial tool for attribute reduction, but it requires computation of upper and lower approximations, which often leads to computational difficulties. In response to the aforementioned issues, this paper proposes a fast attribute reduction algorithm for HDISs based on fuzzy conditional information entropy that utilizes an iterative model and matrix operations. Firstly, a novel measurement of the distance between nominal attribute values is defined using decision attributes. Subsequently, fuzzy conditional information entropy is calculated from the perspective of "the attribute values is fed back to the attribute set" and its properties are provided. Additionally, an iterative attribute reduction model and difference matrix are established, and two new matrix operations are introduced. Finally, an iterative attribute reduction algorithm is provided. The results of experiments and statistical tests on fifteen UCI datasets, including three large datasets, demonstrate that the proposed algorithm is more effective and efficient than nine state-of-the-art algorithms. This paper not only addresses the issue of difficulty in measuring the distance between nominal attribute values but also significantly improves the computational efficiency of attribute reduction algorithms based on RST, making it possible for them to be applied to large datasets

On-line hydropyrolysis gas chromatography-mass spectrometry (HyPy-GC-MS) for kerogen-bound biomarkers

Flash pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) is seldom used to release bound biomarkers, because its hydrogen-poor pyrolysis conditions usually result in a low yield of bound biomarkers and high concentrations of olefins. In this study, by using a Py-GC-MS system and immature kerogen/coal samples, we investigated the effects of heating rate (flash versus 30 degrees C/min), carrier/reaction gas (He versus H-2), hydrogen pressure, and catalyst [(NH4)(2)MoO2S2] on the yields and distributions of bound biomarkers. Also, the bound biomarkers obtained by different pyrolysis conditions were compared with those from catalytic offline hydropyrolysis (HyPy) and free biomarkers from extracted organic matter (EOM). We propose a new technology of hydropyrolysis-gas chromatography-mass spectrometry (HyPy-GC-MS) to be used to release bound biomarkers. HyPy-GC-MS using low-pressure H-2 at slow heating rate can increase the yield of bound biomarkers by 3-9 times, minimize the cracking of the hopanes side chain, better preserve the original sterane and terpane distributions, and have characteristics of lower maturity, compared with conventional flash Py-GC-MS without H-2. Additionally, the steroidal and terpenoid yields by HyPy-GC-MS using low-pressure H-2 at slow heating rate from immature kerogens were 3-6 times that by HyPy. Compared with EOM, biomarker maturity parameter derived from HyPy-GC-MS may not fully represent the actual maturity of samples. Higher hydrogen pressure can significantly facilitate the hydrogenation of unsaturated hydrocarbons into saturated hydrocarbons, but it can also decrease the yields of pyrolysates with higher carbon numbers (i.e., >C-25), leading to a change in the biomarker ratios related to carbon numbers (e.g., the proportion of C-27-C-28-C-29 alpha alpha alpha 20R steranes and TT23/H-30 ratio)

Deciphering the key drivers of oxidative potential during ammonium nitrate-mediated aqueous-phase photoreaction of methoxyphenols

Methoxyphenols are released in abundance from lignin pyrolysis during biomass burning. Apart from being atmospheric brown carbon components that absorb solar radiation and warm the climate, methoxyphenols also undergo photoreaction in the atmospheric aqueous phase and form secondary organic aerosols (aqSOA). While efforts have been devoted to understanding chemical evolutions and climate-related optical properties of aqSOA, their potential health impacts also require timely investigations. Herein, we used the dithiothreitol (DTT) assay to investigate oxidative potential of the aqSOA formed during the 8-h aqueous-phase photoreaction of two typical methoxyphenols, vanillin and vanillic acid, under pH 2 or 8, and with or without ammonia nitrate. The highest DTT consumption rates (RDTT) were observed for vanillin aqSOA formed in the presence of ammonia nitrate and at pH 8. At pH 2, although RDTT increased rapidly during early photoreaction, it reduced after prolonged illumination. High-resolution mass spectrometry and linear regression analyses were performed to correlate the photoreaction products with the observed RDTT. Results showed that three products that present quinone, lactone and dimer structures, respectively, should be the key drivers of elevated RDTT for aqSOA formed during photoreaction of vanillin and vanillic acid alone, whereas it shifted to the nitrogen-containing aromatic compounds during their photoreaction with ammonia nitrate. Our results have revealed the role of nitrogencontaining aromatic compounds in the oxidative potential and health effects of aqSOA from biomass burning, which was rarely recognized before and warrants immediate assessments