Guangzhou Institute of Geochemistry
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Distribution, occurrence and identification of dibenzofuran, benzo[b] naphthofurans and their alkyl derivatives in Gippsland Basin source rocks
No full textDibenzofuran, benzo[b]naphthofurans and a series of their alkylated isomers were identified in coal, coaly shale, and shale extracts from the Gippsland Basin (Victoria, Australia). The dibenzofuran series include C0-C4 dibenzofurans, and the benzo[b]naphthofuran series are composed of benzo[b]naphthofuran, methylbenzo[b] naphthofurans, and possible dimethylbenzo[b]naphthofurans. Seventeen C2 dibenzofurans isomers (including six new isomers) were tentatively identified in rock extracts from the Gippsland Basin. The distribution and contents of C0-C4 dibenzofurans are different for Eocene and Paleocene rocks, providing a source rock age diagnostic correlation tool. Biological origin is the main factor that controls the abundance and distribution of dibenzofuran, benzo[b]naphthofuran and their alkylated isomers, based on investigation of source-, environment- and maturity-derived parameters. Variations in the C1 dibenzofurans/dibenzofuran ratio and the benzo[b]naphtho [2,1-d]furan/benzo[b]naphtho[1,2-d]furan ratio may reflect local paleoclimate changes in the Gippsland Basin
Position-specific carbon isotopes of propane in coal systems in China
No full textEvaluating the origin and fate of hydrocarbons holds significance in many fields, such as energy, geology, astrobiology, biosphere, and environment. However, challenges arise in many cases owing to the limitations of conventional methods. Intramolecular isotope analysis of propane is a new technique that offers the potential to provide insights into gas formation mechanisms; however, a comprehensive understanding of the method remains limited. Specifically, there is little knowledge about its ability to distinguish gases generated by source rocks deposited in similar sedimentary environments such as coal and coaly mudstone. Therefore, this study was undertaken to investigate position-specific carbon isotopes of 40 propane samples from 15 coal-type gas accumulations across four basins in China (Sichuan, Ordos, Qaidam, and Songliao); additionally, clumped isotopologues of methane samples were also analyzed. These coal systems cover a wide range of thermal maturity (from marginally mature to over-mature) at various age strata from the Permian, Triassic, and Jurassic periods, to the Cretaceous period. Our results revealed that propane generated from coal and coaly mudstone differed greatly in intramolecular isotope compositions despite having similar bulk delta 13C3 values. Propane generated from coaly mudstone at a wide range of maturity had relatively more stable delta 13C values in both the central (delta 13Ccental) and terminal carbons (delta 13Cterminal), near the theory generation line of chain-alkane cracking in the plot of delta 13Cterminal vs. delta 13Ccental. However, propane generated from coal had higher stable delta 13Cterminal values and lower delta 13Ccentral values that progressively increased with maturity. Under cooling-down conditions, propane from overmature natural gases became extremely 13C-depleted in both the terminal and central positions, with Delta 13Ccentral (delta 13Ccentral minus delta 13Cterminal) values being as low as -10 parts per thousand, suggesting a partial origin of methane polymerization. Two propane samples from Cretaceous brown sandstone in the Songliao Basin exhibited an increase in both central and terminal carbons, suggesting that they may have surpassed chemical oxidation owing to highvalence Fe(Mn) oxides. These results indicate that intramolecular isotopes of propane can effectively differentiate dominant gas sources in a coal system with coal or coaly mudstone, as well as easily identify isotopic fractionation caused by post-generation processes, such as methane polymerization, mixing and chemical oxidation
Molecular-level transformations of biomass burning-derived water-soluble organic carbon during dark aqueous OH oxidation: Insights from absorption, fluorescence, high-performance size exclusion chromatography and high-resolution mass spectrometry analysis
No full textBiomass burning (BB) releases large amounts of water-soluble organic carbon (WSOC), which would undergo heterogenous oxidation processes that induce transformations in both molecular structures and compositions within BB WSOC. This study designed an aqueous oxidation initiated by OH radicals in the absence of light for WSOC extracted from smoke particles generated by burning of corn straw and fir wood. The BB WSOC was comprehensively characterized using a combination of UV-visible spectra, excitation-emission matrix fluorescence in conjunction with parallel factor analysis (EEM-PARAFAC), high-performance size exclusion chroma-tography (HPSEC), and high-resolution mass spectrometry (HRMS) analyses. Over the course of oxidation, both chromophores and fluorophores exhibited gradual decreases. Moreover, EEM-PARAFAC revealed a preferential degradation of larger-sized protein-like/phenol-like organic matters, accompanied by the accumulation and/or formation of humic-like substances in aged BB WSOC. HPSEC analysis showed notable changes in molecular weight (MW) distributions for both types of BB WSOC during oxidation. Specifically, high MW species (>1 kDa) displayed a tendency to form along with oxidation, possibly attributed to the formation of assemblies via intermolecular weak forces. After oxidation, evidence of CHO compound degradation and enrichment/formation of CHON compounds was observed for both types of BB WSOC. Remarkably, the resistant, degraded and produced molecules for BB WSOC were dominated by CHO (38-73 %) and lignin-like molecules (41-47 %), suggesting diverse responses to oxidation within these two groups. Furthermore, polyphenols experienced selective degradation, while CHON, aliphatic and poly-aromatic molecules tended to form during the oxidation process for both types of BB WSOC. In summary, this study provides a comprehensive understanding of the molecular-level transformations undergone by BB WSOC during dark aqueous OH oxidation. The findings significantly contribute to our insights into atmospheric evolution of BB WSOC, thereby playing a crucial role in accurately assessing their effects within climate models and informing policy decisions
Unveiling the synergistic mechanism of autochthonous fungal bioaugmentation and ammonium nitrogen biostimulation for enhanced phenanthrene degradation in oil-contaminated soils
No full textAutochthonous bioaugmentation and nutrient biostimulation are promising bioremediation methods for poly-cyclic aromatic hydrocarbons (PAHs) in contaminated agricultural soils, but little is known about their combined working mechanism. In this study, a microcosm trial was conducted to explore the combined mechanism of autochthonous fungal bioaugmentation and ammonium nitrogen biostimulation, using DNA stable-isotope-probing (DNA-SIP) and microbial network analysis. Both treatments significantly improved phenanthrene (PHE) removal, with their combined application producing the best results. The microbial community compo-sition was notably altered by all bioremediation treatments, particularly the PHE-degrading bacterial and fungal taxa. Fungal bioaugmentation removed PAHs through extracellular enzyme secretion but reduced soil microbial diversity and ecological stability, while nitrogen biostimulation promoted PAH dissipation by stimulating indigenous soil degrading microbes, including fungi and key bacteria in the soil co-occurrence networks, ensuring the ecological diversity of soil microorganisms. The combination of both approaches proved to be the most effective strategy, maintaining a high degradation efficiency and relatively stable soil biodiversity through the secretion of lignin hydrolytic enzymes by fungi, and stimulating the reproduction of soil native degrading microbes, especially the key degraders in the co-occurrence networks. Our findings provide a fresh perspective of the synergy between fungal bioaugmentation and nitrogen biostimulation, highlighting the potential of this combined bioremediation approach for in situ PAH-contaminated soils
Rare earth element enrichment in sedimentary phosphorites formed during the Precambrian-Cambrian transition, Southwest China
No full textNumerous sedimentary phosphorites in Southwest China were formed around the Precambrian-Cambrian transition (PC-C), including the upper Ediacaran Doushantuo Formation and lower Cambrian Gezhongwu Formation. The Gezhongwu phosphorites in Zhijin exhibit marked rare earth element (REE) enrichment (>1000 ppm), and may represent new REE resources. Although the main characteristics of the Gezhongwu phosphorites have been well constrained, the REE enrichment mechanisms remain unclear. We undertook a comparative study of three typical sedimentary phosphorites with variable REE contents formed at the PC-C transition in central Guizhou Province, Southwest China. These include sections A and B of the Doushantuo phosphorites (560 +/- 8 Ma) from the Weng'an area (i.e., WA-A and WA-B), and the Gezhongwu phosphorites (527 +/- 24 Ma) from the Zhijin area (ZJ). The phosphorites were investigated with state-of-the-art macroscale to nanoscale analytical techniques. In contrast to the extraordinary REE enrichment in the ZJ phosphorites (average Sigma REE = 1157 ppm), the phosphorites in WA-A (average Sigma REE = 234 ppm) and WA-B (average Sigma REE = 114 ppm) are REE-poor. Elemental mapping by laser ablation-inductively coupled plasma-mass spectrometry, along with transmission electron microscopy analyses, showed the REEs in the studied phosphorites are hosted in nanoscale francolites. The Sr-87/Sr-86 and Y/Ho ratios of the francolite grains indicate that greater terrigenous input may have led to more REE enrichment in the WA-A than WA-B phosphorites, but this cannot explain the extraordinary REE enrichment in the ZJ phosphorites. The F/P2O5 values of the francolite grains in the ZJ phosphorites (similar to 0.097) are higher than those in the WA-A (similar to 0.084) and WA-B (similar to 0.084) phosphorites, and the grain size of the francolite in the ZJ phosphorites (similar to 89.9 nm) is larger than those in the WA-A (similar to 56.6 nm) and WA-B (similar to 57.4 nm) phosphorites, indicative of more intense reworking of the ZJ than WA phosphorites during early diagenesis. A plot of Nd concentration versus Ce/Ce* reveals that lower sedimentation rates characterized the ZJ phosphorites. Therefore, intense sedimentary reworking during early diagenesis resulted in more REEs being sequestered by the marine phosphates from seawater and pore waters at a lower sedimentation rate, which resulted in the extraordinary REE enrichment in the ZJ phosphorites. Our findings highlight the multiple factors that controlled formation of sedimentary phosphorites around the PC-C transition (especially the intense reworking and redox conditions of the overlying seawater), and provide further insights into REE enrichment in sedimentary phosphorites worldwide.(c) 2023 China University of Geosciences (Beijing) and Peking University. Published by Elsevier B.V. on behalf of China University of Geosciences (Beijing). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Holocene provenance variations and palaeofloods response to ENSO-driven monsoon precipitation in the subalpine peatland in southern China
No full textThere have been few investigation of the provenance of sediments and hydrological response to past climatic change in the subalpine peatland in southern China. The source of sediments and regional climatic variations during the Holocene have been deduced from Rare Earth Elements (REEs), Sr-Nd isotopic data and grain size end-member modeling analysis (EMMA) derived from peat sediments from the southwestern mountainous region of Hunan Province, China. From the distinctive Sr-Nd isotopes patterns, LREEs enrichment, and the Eu anomaly observed in these sediments, it can be concluded that local weathering residues have been the primary sedimentary source throughout the Holocene. Based on the method of EMMA, four distinct end members were identified. EM2, signifying weathering products of moderate particle size, is sensitive to climate variations. This sensitivity makes it an effective marker to track the historical evolution of the East Asian summer monsoon (EASM) intensity. The results suggest that the prevalence of the relatively weak EASM during the interval 11,600-9000 cal yr BP, followed by an overall weakening trend during the past 9000 years. EM3 + EM4, the coarsest component in the peat sediments, indicate strong runoff typically caused by the extreme weather events. Notably, the occurrence of relatively high EM3 + EM4 component during the interval 5400-4500 cal yr BP and 3500-2600 cal yr BP is consistent with the previous reported palaeoflood events in the Yangtze River basin. We suggest that the regional flood patterns are predominantly controlled by the East Asian monsoon system, which in turn, is driven by ENSO activities. For a comprehensive understanding of regional flood patterns, it is imperative to extend research into high-altitude areas
Apatite Textures, Elemental and Isotopic Compositions Unmask the Homogenizing Process in Silicic Magma Chambers
No full textSilicic magmas are the most viscous of all magmas, however some granitic plutons display remarkably homogeneous compositions, which contradicts the hypothesis that mechanical mixing is the main homogenizing process in the magma chamber. Thus much remains controversial about the mechanisms responsible for the homogeneities of silicic plutons. Here, we present textural observations, elemental mapping, and in situ elemental and Nd-O isotopic data of apatites from the compositionally homogeneous Late Permian Yuanyang A-type granitic pluton (SW Yunnan, South China). Apatite grains display oscillatory chemical zonation and resorption-precipitation texture, suggesting incremental growth dominated by co-genetic magma batches injection. The intra-/inter-grain core to rim elemental and Nd-O isotopic variations imply crystal transfer and crystallization from different melt domains within the crystal mush. We propose that rejuvenation events associated with hotter cogenetic intermediate magma batch injection has induced crystal mush reactivation and convective stirring in silicic magma chambers, thereby homogenizing the entire reservoir.
Magma mixing between mafic and viscous felsic magmas is usually incomplete, forming heterogeneous structures and geochemical compositions in felsic magma bodies. However, some silicic magma bodies have homogeneous compositions and structures, such as the Late Permian Yuanyang A-type granites (YAGs) in southwestern South China, and the actual homogenizing process in silicic magma chamber is still unclear. Accessory apatite is ubiquitous in felsic plutons, whose growth zoning could reflect magma chamber evolution. Apatite grains collected from the YAGs show complex resorption-precipitation texture. Their core-rim oscillatory elemental and Nd-O isotopic variations suggest compositional perturbations of ambient magma, probably caused by the injection/mixing of multiple magma pulses. Accordingly, we propose that hot magma recharge could reactivate the crystal-mush, causing magma convection and stirring that gradually homogenized the silicic magma chamber.
The apatites from the compositionally homogeneous Yuanyang A-type granites are texturally and geochemically heterogeneousThe identified four apatite zoning domains documented magma replenishment, mixing and crystal mush reactivationMagma convection and stirring induced by magma batches injection are key to homogenizing the silicic magma chambe
Addition of Exogenous Organic Ameliorants Mediates Soil Bacteriome and Microbial Community Carbon Source Utilization Pattern in Coastal Saline-Alkaline Soil
No full textKnowledge regarding how abiotic and biotic environmental factors operate in soil microbiome reassembly remains rudimentary in coastal saline-alkaline soils amended by different organic ameliorants. In this study, field trials were conducted to investigate the impacts and underlying mechanisms of sewage sludge (S) and sludge-based vermicompost (V) at the application amounts of 0, 50, and 100 t ha-1 on soil physicochemical characteristics, carbon source utilization pattern, and bacteriome in coastal saline-alkaline soils. Results revealed that impacts of the organic ameliorants on soil's physicochemical and microbial attributes were highly dependent upon the carbon types and amounts applied. Unsurprisingly, applying sewage sludge and vermicompost significantly alleviated environmental constraints, such as saline-alkaline stress and nutrient deficiency, with lower pH, salinity, and higher soil organic carbon content observed in organics-amended soils. Specifically, higher microbial substrate metabolic activity, but lower diversity was observed in saline-alkaline soils amended by organic ameliorants. In addition, reassembled bacteriomes harboring distinguishable core and unique community profiles were observed in reclaimed soils as compared to unamended saline-alkaline soil. Procrustes analysis showed that the soil microbial utilization pattern of carbon sources was significantly related to the alterations in their physicochemical property and bacterial core microbiome. Additionally, Redundancy Analysis (RDA) revealed that soil core bacteriome reassembly was dominated by the integrated impacts of soil salinity, successively followed by carbohydrates, amino acids, polymers, pH, soil organic carbon (SOC), and available nitrogen (AN). Overall, this study provides a comprehensive understanding of soil abiotic and biotic determinants in bacteriome assembly in coastal saline-alkaline soil remediation mediated by organic ameliorants
Exploitation and Utilization of Generated Oil and Gas by Pyrolysis Simulation Modeling of Shale Source Rocks under the Condition of In Situ Conversion
No full textPrevious studies have mainly focused on the source rocks of the 7th Member of Yanchang Formation (Chang 7 Member) in the Ordos Basin, with very few studies focusing on the extracts from the source rocks. These extracts have important guiding significance for studying the in situ conversion process of shale oil. Taking the shale source rock of the Chang 7 Member as an example, this paper selected the extract of shale source rock (i.e., retained oil), which has been less studied previously, as the sample to carry out the hydrocarbon-generating pyrolysis simulation experiment of a semi-open-semi-closed system. Seven groups of parallel simulation experiments were designed with a pressure of 20 MPa. The generated oil and gas were collected and quantified, and their geochemical characteristics were researched. In addition, the generated oil and gas were investigated from aspects of cumulative yield and net increased yield, and the chromatographic and mass spectral characteristics of the generated oil were also researched. Based on this, an inductive hydrocarbon generation model of retained oil in shale source rocks was established: slow hydrocarbon generation stage (300-320 degrees C), rapid hydrocarbon generation stage (320-360 degrees C), and residual oil pyrolysis stage (0.79%Ro-1.47%Ro). This study is of important significance to guide the research on the in situ conversion process of shale source rock
Contrasting Cu isotopes in mid-ocean ridge basalts and lower oceanic crust: Insights into the oceanic crustal magma plumbing systems
No full textMagma plumbing systems exert strong controls on the formation and evolution of the oceanic crust during crust accretion. However, plumbing system dynamics based largely on mid-ocean ridge basalts (MORBs) are extremely difficult to constrain because the MORBs are aggregated melts and original information may have been blurred. Copper isotopic compositions of lower crustal gabbroic cumulates effectively archive early-stage histories because sulfides constitute the dominant Cu budget of gabbroic cumulates and are largely isolated from subsequent magma filtering processes. Here, we present Cu isotopes of a suite of gabbroic cumulates from the ultraslow-spreading Southwest Indian Ridge (Hole U1473A), and MORBs from the South Mid-Atlantic Ridge and East Pacific Rise. The delta 65Cu of the MORBs from this study (+0.04 %o to +0.19 %o) match those of previous MORB analyses, indicating uniform delta 65Cu at various spreading rates. In contrast, the delta 65Cu of gabbroic rocks vary significantly (-1.14 %o to 0.87 %o), exceeding by far the range known for peridotites. The Cu budget of these gabbroic rocks is hosted in sulfides and the mantle-like S isotopic compositions of sulfides indicate their origin of igneous processes. These results thus suggest that magma accumulation and sulfide segregation would lead to notable Cu isotopic fractionation in the lower oceanic crust. We propose that repeated recharging of primitive melts and efficient mixing of melts within the plumbing system can buffer the removal of early 63Cu-rich sulfides from sulfide-saturated MORBs. The discrepancy in delta 65Cu between lower oceanic crust and MORBs is a natural consequence of continuous replenishment that occurs concurrently with melt-rock interaction, mixing, crystallization and extraction, irrespective of the oceanic settings. The consistent delta 65Cu in MORBs (0.09 +/- 0.08 %o) and komatiites (0.06 +/- 0.06 %o) further indicates that their Cu isotopes reflect the mean mantle source composition, providing a robust delta 65Cu for bulk silicate Earth (BSE) of 0.08 +/- 0.08 %o (2sd). Accordingly, we propose that in open sub-ridge plumbing systems, other incompatible element isotopes and ratios of elements with similar incompatibility in MORBs as Cu isotopes suggest, could also represent mean mantle source compositions