Guangzhou Institute of Geochemistry
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The δ<SUP>13</SUP>C composition and genetic origin of a series straight long-chain alkyl naphthalene isomer pairs in the Upper Cretaceous lacustrine sediments of Songliao Basin, China
No full textA series of straight long-chain alkyl naphthalene isomer pairs (LANs) have been detected in the Upper Cretaceous lacustrine sediments of Nenjiang Formation (K2n1+2) in the Songliao Basin, and their distribution and carbon isotopic composition were investigated. The results indicate that the composition and distribution of LANs exhibit significant variations. The relative abundance of methyl- and dimethyl-naphthalenes shows a reciprocal correlation with that of LANs, increasing and declining in tandem. The delta 13C composition of LANs varies from -24.6 %o to -32.6 %o, with an average of -28.5 %o, which is notably higher than that of n-alkanes, ranging from -31.9 %o to -34.5 %o. The delta 13C composition of methylnaphthalenes (MNs) ranges from -26.9 %o to -27.1 %o, which is generally more positive than the average delta 13C composition of LANs. Analysis of the carbon isotopic composition of n-alkanes, methylnaphthalenes, and the series of LANs, along with their distribution patterns, suggests the presence of multiple formation mechanisms. Specifically, the observed declining variation pattern of delta 13C values for LANs along with the increasing carbon number of the alkyl chain may indicate a novel formation pathway. This pathway likely involves a direct reaction between 13C-enriched naphthalene and 13C-depleted straight long-alkyl chains during diagenesis. The relative abundance ratio of total methyl-substituted naphthalenes (Sigma MNs) to the total LANs (Sigma LANs), expressed as the Sigma MNs/Sigma LANs ratio, exhibits a profile variation that correlates with the profile changes of the Pr/Ph ratio, TOC content, and HI index. This correlation indicates that specific environmental conditions or source inputs, such as reduced sedimentary conditions or specific algal contributions, may be conducive to the formation of LANs
Modulating interfacial electron transfer in hydrothermal carbon/ humboldtine to achieve superior heterogeneous Fenton reactivity and H2O2 utilization efficiency
No full textThe strategic enhancement of interfacial electron transfer dynamics between carbon and iron, coupled with the improvement of H2O2 ' s effective decomposition, is imperative for achieving significant progress in the field of iron-carbon-based heterogeneous Fenton catalysis. This study prepared a novel Fenton catalyst, namely hydrothermal carbon/humboldtine (HTC/Hum), where Fe(III) was totally reduced to Fe(II) during catalyst preparation process due to the highly effective electron transfer between carbon and iron. Consequently, HTC/Hum exhibits exceptional Fenton catalytic performance, which would achieve 100 % degradation of Bisphenol A (BPA) within 5 min, outperforming conventional carbon-iron materials by increasing BPA degradation and H2O2 utilization efficiency by 230-400 and 18-24 times, respectively. Density functional theory (DFT) calculations also indicated that the energy barrier for HO center dot escaped from HTC/Hum is significantly lower than the conventional catalysts. Xray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and electrochemical analysis all demonstrated that the electron transfer from carbon to iron also occurred continuously in the HTC/Hum system during the Fenton reaction, facilitated by electrons from defects and persistent free radicals in HTC, promoting the redox cycle of Fe(III)/Fe(II). This study presents a novel strategy enhancing electron transfer and H2O2 utilization, with promising applications in environmental remediation
Radiocarbon Fingerprinting Black Carbon Source History in the Himalayas
No full textBlack carbon (BC) is considered as an important contributor to the Himalayan glaciers melt in the past few decades. However, the long-term source apportionment of BC remains unclear. Here we present the first radiocarbon (14C)-based annual variation of BC source apportionment in an ice core spanning the period of 1959-2012 drilled from the Southeastern Tibetan Plateau, a receptor site of South Asia outflow. We find fossil fuel combustion is a major contribution (73% +/- 5%), yet the biomass burning fraction (& fnof;biomass) has grown from 24% +/- 4% to 30% +/- 4% since 1990. Intriguingly, we further find the & fnof;biomass demonstrating a robust correlation with South Asian wildfires linked to climate oscillations. Thus, for mitigating BC impacts on Himalayan glaciers, South Asia's transition from fossil fuels to clean energy is a more efficient and urgent strategy than reducing residential biomass burning
Nano-Scale Insights into Clay Minerals Regulating the Fe(II)-Catalyzed Ferrihydrite Transformation under Anoxic Conditions
No full textMetastable ferrihydrite nanoparticles and clay minerals always coexist as heteroaggregates in nature due to their abundance, opposite charge, and large interface energy. However, the impact of clay minerals on the transformation of ferrihydrite under anoxic conditions remains elusive. This study systematically investigated the effect of distinct clay minerals on the Fe(II)-catalyzed transformation of ferrihydrite and clarifying the underlying nanoscale mechanisms for the first time. Our results demonstrated that clay minerals could affect the production and recrystallization of labile Fe(III) (an active Fe(III) intermediate species formed by oxidation of Fe(II) at the ferrihydrite surface) by dispersing ferrihydrite aggregates. This modulation led to different transformation rates, higher crystallinity of formed lepidocrocite, and enhanced goethite formation in the heteroaggregates. Importantly, montmorillonite can accommodate Fe(II) and labile Fe(III) within its interlayer spaces, which further led to the inhibited crystallization of Fe(II) to magnetite and long-term preservation of labile Fe(III). Additionally, clay minerals served as templates for forming dendritic goethite and hexagonal magnetite nanoplates. Our findings provide new insights into the complicated roles of clay minerals in controlling the ferrihydrite transformation and other iron (oxyhydr)oxides formation, which is significant for predicting the bioavailability of iron and the fate of other coexisting contaminants
Biogenic emission as a potential source of atmospheric aromatic hydrocarbons: Insights from a cyanobacterial bloom-occurring eutrophic lake
No full textAs 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
A comparative study on the formation of nitrogen-containing organic compounds in cloudd roplets and aerosolp articles
No full textNitrogen-containing organic compounds (NOCs)maypotentiallycontributetoaqueoussec-ondaryorganicaerosols,yet the different formationofNOCsinaerosolparticlesand clouddropletsremainsunclear. With the in-situmeasurementsperformedatamountainsite(1690ma.s.l.)in southernChina,weinvestigatedtheformationofNOCsintheclouddropletsandthecloud-freeparticles,basedontheirmixingstateinformationofNOCs-containingparticlesbysingleparticlemassspectrometry.TherelativeabundanceofNOCsinthecloud-freeparticleswassignificantlyhigherthanthoseincloudresidual(cloudRES)particles.NOCswerehighlycorrelatedwithcarbonylcompounds(includingglyoxalateandmethylglyoxal)inthecloud-freeparticles,however,limitedcorrelationwasobservedforcloudRESparticles.AnalysisoftheirmixingstateandtemporalvariationshighlightsthatNOCswasmainlyformedfromthecarbonylcompoundsandammoniuminthecloud-freeparticles,ratherthaninthecloud RES particles.Theresultssupportthattheformation of NOCsfromcarbonylcompoundsisfacilitatedinconcentratedsolutionsinwetaerosols,ratherthanclouddroplets.In addition,we have identified the transport of biomass burnin
A water probe for direct pH measurement of individual particles via micro-Raman spectroscopy
No full textThe acidity of atmospheric aerosols influences fundamental physicochemical processes that affect climate and human health. We recently developed a novel and facile water-probebased method for directly measuring of the pH for micrometer-size droplets, providing a promising technique to better understand aerosol acidity in the atmosphere. The complex chemical composition of fine particles in the ambient air, however, poses certain challenges to using a water-probe for pH measurement, including interference from interactions between compositions and the influence of similar compositions on water structure. To explore the universality of our method, it was employed to measure the pH of ammonium, nitrate, carbonate, sulfate, and chloride particles. The pH of particles covering a broad range (0-14) were accurately determined, thereby demonstrating that our method can be generally applied, even to alkaline particles. Furthermore, a standard spectral library was developed by integrating the standard spectra of common hydrated ions extracted through the waterprobe. The library can be employed to identify particle composition and overcome the spectral overlap problem resulting from similar effects. Using the spectral library, all ions were identified and their concentrations were determined, in tum allowing successful pH measurement of multicomponent (ammonium-sulfate-nitrate-chloride) particles. Insights into the synergistic effect of Cl-, NO3 -, and NH4 + depletion obtained with our approach revealed the interplay between pH and volatile partitioning. Given the ubiquity of component partitioning and pH variation in particles, the water probe may provide a new perspective on the underlying mechanisms of aerosol aging and aerosol-cloud interaction. (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
No full textMicroplastics 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
A preliminary investigation of pore development mechanisms in highly matured solid bitumen: Implications from the Ediacaran Dengying Formation solid bitumen in the central Sichuan Basin, Southwest China
No full textAlthough pores in solid bitumen are crucial for shale reservoirs, their development mechanisms have not been fully understood partly due to the small size of solid bitumen in shales and the difficulty in its discrimination from residual kerogen. However, solid bitumen in conventional reservoirs generally has a larger size and definite origin, and therefore the examination of their pores can provide some insights into the mechanisms of pore formation in shale solid bitumen. In this study, solid bitumen samples from conventional reservoirs of the Ediacaran Dengying Formation in the central Sichuan Basin were collected for petrographic and geochemical analyses to investigate their pore characteristics and formation mechanisms. The results indicate that pores are commonly identified in solid bitumen grains that are derived from the cracking of tar pads and in solid bitumen grains that have experienced gravity-driven component separation during their formation. The development of pores in solid bitumen is controlled by the combined effect of gas expulsion and the viscosity of solid bitumen during its movable stage. The gas expulsion from movable bitumen creates pores, and they can be preserved or healed depending on the component-controlled viscosity of movable bitumen. The enrichment of sulfur- and oxygen-containing compounds and heavy components such as asphaltenes in movable bitumen can enhance its viscosity and thus inhibit the healing of pores, ultimately facilitating pore development in the present overmature solid bitumen grains
Zirconia on acid-treated halloysite as an efficient catalyst for conversion of mono-saccharides to 5-hydroxymethylfurfural
No full textAn acidic catalyst was designed for catalyzing conversion of fructose into 5-hydroxymethylfurfural through a two-step approach. First, the textural features and acidity of halloysite nano clay were improved via acidtreatment. Secondly, zirconia, an acidic catalytic species, was synthesized through a simple procedure and immobilized on the acid-treated halloysite, resulting in an effective catalyst with increased acidity. Analysis of the catalyst confirmed that both acid-treatment and the incorporation of zirconia enhanced the acidity of the catalyst and improved its activity. To optimize the yield of the product, Response Surface Method was used and the effects of various reaction variables were studied. According to the results, yield of 93 % of the product was achieved within 60 min at 80 degrees C by using 25 wt% of the catalyst. The kinetic study showed that the activation energy was 61.6 kJ/mol. Thermodynamic parameters were determined to be 70 kJ/mol for enthalpy, -60 J/mol for entropy, and 91.5 kJ/mol for Gibbs free energy, respectively. Notably, the catalyst demonstrated high recyclability with minimal leaching of zirconia. In addition to its effectiveness in catalyzing the conversion of fructose, the catalyst exhibited efficient performance in the conversion of other monosaccharides