TOC Content Research Articles

The H2 potential of the Colombian coals in natural conditions

Coal gasification to manufacture dihydrogen (H2) has long been known as a surface process. Recent works have also highlighted the H2 generating potential of the Organic Matter (OM). The evolution of OM generates H2 all along the process but this gas is only expected to remain as free H2 after the maturation and expulsion of the hydrocarbons (HC) which means at a high temperature of above 200 °C. In this paper we studied the potential of three different tertiary coals from Amaga, La Jagua de Ibirico and Barrancas, all located in Colombia. Their H2 yields were studied using a pyrolyser and the kinetic of the H2 generation were quantified. All the studied coals are immature to early mature as source rock (SR) with large TOC content, between 66 and 83%, and good H2 potential. The highest values were found for the Barrancas area where the potential reached 25 mg H2/g TOC. The temperature corresponding to the peak of H2 generation is between 740 and 800 °C depending of the heating rate. This corresponds to the 200–300 °C for the H2 kitchen, even if the H2 generation starts before as already observed for continental organic rich source rock. Comparison with the other coals shows that H2 potential is linear with TOC. In the Colombian coals, the H2 yield in mg H2/g of rock is around 1/4 of the TOC content. In average, these coals have so a H2 yield about 10 000 mmol H2/kg of rock, two orders of magnitude above the “best” olivines. It should nevertheless be kept in mind that the extrapolation of these laboratory data to sedimentary basins remains unconstrained and will need to be refined when well data and modelling tools are available.

Statistical estimation of the early to middle Ediacaran ocean redox architecture in the Yangtze block of South China

Early to middle Ediacaran organic-rich black shales host several famous fossil biotas and provide key evidence for understanding the coevolution of multicellular organisms and palaeoceanic environment. The water column redox states play critical roles in organic-rich shale deposition. Amongst multiple geochemical redox indexes, iron-speciation chemistry (FeHR/FeT, Fepy/FeHR) in shales constitutes a reliable proxy to reconstruct the first-order redox framework of the ocean basin. However, iron-speciation is a local marine redox proxy, and only compiled data collected from multiple different sedimentary facies record statistically significant changes of oxidation states within a depositional basin. Here we compiled the spatiotemporal distribution of iron-speciation data in early to middle Ediacaran black shales of the Yangtze block in South China. New high-resolution analysis on two outcrops and one drill-core reflects overall ferruginous condition and dominant euxinic condition locally interrupted by oxic states, respectively, generally indicating pervasive anoxic depositional environment for the Member II shales of the Ediacaran Doushantuo Formation in the Lower Yangtze block. Compilation of fourteen Ediacaran sections from shallow-, slope- and deep-water facies demonstrates frequent spatiotemporal oscillation of the redox conditions throughout the Yangtze block. Widespread ferruginous states, accompanied with euxinic zones mainly focusing in lower slope facies, are detected during the early Ediacaran period, in contrast with more widespread euxinic settings in the middle Ediacaran period. Statistical data including new high-resolution results from the Lower Yangtze block show generally low enrichment for redox sensitive elements (RSEs, e.g., Mo, V and U) in the Member II shales probably due to their contemporary low seawater concentrations. An increase of RSEs concentrations occurs in the Member IV shales, which probably reflects more oxidized Earth surface environment during middle Ediacaran period. The increasing Earth oxygenation documents the occurrence of widespread euxinic states during deposition of the Member IV shales. Compilation of spatial distribution of TOC contents in black shales demonstrates their apparent relevance to spatial distribution of the euxinic rather than ferruginous states, which is likely due to the favorable role of sulfurization process on burial and preservation of organic matters. The euxinic states may also facilitate the exceptional preservation of the soft-bodied Ediacaran fossils.

Enhanced photocatalytic degradation of Congo red dye into safe end-products over ZnO@polyaniline/coal composite as low cost catalyst under visible light: Pathways and ecotoxicity

ZnO@polyaniline/coal nanocomposite (ZnO@PANI/C) was synthesized and characterized by different analytical techniques as potential enhanced photocatalyst for the successful oxidation of Congo red dye (CR) into eco-friendly end-products. The investigated CR concentration (5 mg/L) was completely decolorized after 120 min, 100 min, 80 min, and 40 min after the incorporation of ZnO@PANI/C dosages at 0.2 g/L, 0.3 g/L, 0.4 g/L, and 0.5 g/L, respectively. The synergetic studies demonstrate a significant impact of the integrated components (coal, polyaniline (14.2 % oxidation of CR), ZnO (21.6 % oxidation of CR), 43.7 % (PANI/C oxidation of CR), and 64.3 % (ZnO/C oxidation of CR)) on the catalytic activity of ZnO@PANI/C (100 % oxidation of CR), which is higher than that of the individual components. The investigation of TOC content reflects that the complete mineralization can be detected after 100 min and validates the formation of different species of intermediates started by sodium-3-(phenyl diazenyl) naphthalene-1-sulfonate until detecting ethyl benzene. The findings of the oxidizing trapping tests demonstrate the controlling impact of the hydroxyl radicals as the oxidation in the presence of its trapping reagent (Isopropanol) declined to 8.6 %. The oxidation pathway of CR over ZnO@PANI/C involved a progressive series of decarboxylation and dihydroxylation ended by ethylbenzene, which in turn produced nontoxic products such as H2O and CO2. The eco-toxicity tests reflect the efficiency of the photo-oxidation of CR contaminants by ZnO@PANI/C in reducing acute toxicity (LC50 and EC50 > 100) and chronic (ChV > 10) toxicities of CR dye after 60 min of remediation.

Carbon accumulation features in different functional zones of cities in the steppe zone.

This article presents findings on the study of content, profile distribution, and reserves of various carbon forms (organic carbon (TOC) and inorganic carbon (IC)) in Urbic Technosols and Ekranic Technosols within the residential zone of the city, alongside zonal Calcic Chernozems in the recreational zone of Rostov-on-Don, Aksai, and Bataysk. It was revealed that the TOC content in the upper horizons of Urbic Technosols is significantly lower than in the chernozem horizons of fallow areas, registering at 2.59 ± 0.79% and 3.25 ± 0.94%, respectively. IC exhibits an inverse trend, with maximum content observed in the upper horizons of Ekranic Technosols. Down the soil profile, disparities in TOC and IC contents are mitigated. This specificity in TOC accumulation and profile distribution signifies a "bipartite" profile alteration in buried chernozems, affecting solely the upper stratum rather than the entire soil profile. The presence of woody vegetation in the dry-steppe zone positively influences TOC accumulation. Calcic Chernozems beneath woody vegetation showcase the highest TOC reserves within the 30-cm layer (10.61 ± 1.45kg/m2). Calcic Chernozems of fallow areas under natural steppe vegetation contain 8.94 ± 1.75kg/m2, Technosols of the residential zone 8.44 ± 2.47kg/m2. For Technosols of the residential zone, a weakening of the dependence of TOC and IC content on the depth of the soil horizon is observed.

Palynostratigraphy of the Mississippian-Pennsylvanian boundary in the Tyler Formation, Williston Basin, USA: Implications for organic matter-rich source rocks and paleoenvironmental reconstruction

The Carboniferous was a period of intense environmental perturbations, climate changes between greenhouse and icehouse, eustatic sea level change, and accumulation of organic carbon-rich sediments. At this time, the Tyler Formation was deposited in the midcontinent USA. A detailed palynological analysis of the Tyler Formation revealed a highly diverse assemblage of spores with minor pollen content, represented by 100 species belonging to 51 genera. Stratigraphically constrained spores and pollen grains were used to construct three interval zones of middle-late Chesterian (late Viséan-Serpukhovian) to early Morrowan (middle Bashkirian) ages. The stratigraphic position of the Mississippian-Pennsylvanian boundary was determined in the lower Tyler Formation based on the last appearance of typical forms of the late Chesterian, including Tripartites vetustus, Knoxisporites triradiatus, Knoxisporites stephanephorus, Densosporites diatretus, and Schopfipollenites acadiensis, compared to the first appearance of early Morrowan Crassispora kosankei, Cirratriradites saturnii, Radiizonates aligerens, and Raistrickia saetosa. Palynofacies analysis and statistical clustering of the Tyler Formation showed three palynofacies assemblages. PFA-1 showed moderate relative abundances of phytoclasts and AOM, suggesting deposition close to fluvio-deltaic and shallow marine environments, while PFA-2 exhibited high abundances of phytoclasts, mostly of opaque wood, reflecting deposition in active river-dominated delta plains. PFA-3 showed the highest abundances of AOM, suggesting deposition in a shallow marine environment. Organic petrography and geochemistry data indicate that the Tyler Formation is one of the best source rock intervals throughout the midcontinent USA. Based on organic matter richness, the Tyler Formation is subdivided into three groups. The first group has TOC contents higher than 10 wt% of kerogen Types III, mixed II/III, and II with excellent hydrocarbon generation potential. The second group has TOC content in the range of 2–10 wt% of kerogen Types III, mixed II/III, and II, and fair to excellent hydrocarbon generation potential. The third group shows organic matter richness with TOC content below 2 wt% with good organic matter richness and kerogen Types III to IV, and poor to fair hydrocarbon generation potential. The organic matter thermal maturity is evaluated based on Tmax and VRo% values, suggesting that all samples of Tyler Formation are in the early to late stages of the oil window. However, care should be considered when assessing a mature source rock because the kerogen typing and generation is based on present-day TOC, S2, and HI rather than their original values.

Integrated Analysis of the Eocene Sakesar Formation: Depositional Environment, Microfacies, Geochemistry, and Reservoir Characteristics in the Potwar Basin, Pakistan

The current study aimed to evaluate the petroleum generation potential of the Sakesar Formation. This study interprets and presents a depositional environment model, microfacies, and geochemical and petrophysical data of the Eocene Sakesar Formation in the Potwar Basin, Pakistan. Twenty well-cutting samples from two wells and six fresh outcrop samples were thoroughly studied. Results of total organic carbon and Rock-Eval pyrolysis of Sakesar Formation sediments show fair to good TOC contents ranging from 1.2-1.67 wt%. S2 values of samples showed fair to good generation potential. Sediments appear mature, having primarily mixed Type II-III kerogen with good oil/gas-generation potential. Three microfacies have been identified in the Sakesar Formation at the Tatral section: Bioclastic wacke-packstone, Lockhartia-rich mud-wackestone, and benthic foraminiferal wackestone. The microfacies of the Sakesar Limestone depict the deposition of the Sakesar Limestone from the distal middle ramp to restricted inner ramp settings. Petrophysical well logs analysis of the Sakesar Formation showed an average porosity of ~9.12%; the lithology was identified as limestone, having an average water saturation of ~22.32% and an average hydrocarbon saturation of ~77.68%. Thus indicating average to good reservoir properties with very good hydrocarbon saturation. Sakesar Formation sediments characteristics interpretation showed that it can act as both source rock and reservoir rock in the Potwar Basin.

Controlling Factors of Organic Matter Enrichment in Marine–Continental Transitional Shale: A Case Study of the Upper Permian Longtan Formation, Northern Guizhou, China

The marine–continental transitional shale of the Upper Permian Longtan Formation in northern Guizhou is an important source rock in the upper Yangtze region of China, and it holds significant potential for the exploration of shale gas. To investigate the correlation between sedimentary conditions and the accumulation of organic matters in marine–continental transitional shale, this paper performed an extensive analysis using organic geochemical testing, organic petrology examination, a cross-section polisher–scanning electron microscope (CP-SEM), and geochemical analysis. The Jinsha and Dafang drilling cores were selected as the research subjects. The results showed that the TOC of the Longtan Formation in the study area was relatively high, and the TOC content of the tidal flat–lagoon environment (average of 8.37%) was significantly higher than that of the delta samples (average of 2.77%). The high content of Al2O3 (average of 17.41% in DC-1, average of 16.53% in JC-1) indicated strong terrigenous detrital input. The proxies indicated that the Longtan Formation shale in northern Guizhou was deposited in a climate that was both warm and humid, with oxic–dysoxic sedimentary water characterized by high biological productivity and a rapid sedimentation rate. The organic-rich shales during the marine and continental transitional phases were affected by various factors, including the paleo-climate, water redox properties, paleo-productivity, sedimentation rate, and other variables, which directly or indirectly impacted the availability, burial, and preservation of organic matter.

Correlation and response of astronomical forcing in lacustrine deposits of the middle jurassic, sichuan basin, southwest China

The astronomical cycle characteristics of Mesozoic lacustrine fine-grained sedimentary rocks play a crucial role in understanding the formation environment of such sediments. The fine-grained sedimentary rocks of the Middle Jurassic Lianggaoshan Formation in the Sichuan Basin, China, constitute a significant lacustrine deposit. Previous research has primarily focused on its reservoir characteristics, with limited understanding of the relationship between lithofacies changes and astronomical cycles. To fill this knowledge void, we provide a continuous lacustrine core record of approximately 260 m from the XY-4 well, spanning the Lianggaoshan Formation in the Eastern Sichuan Basin. Initially, we categorized it into eight lithofacies types and established a lithologic ranking sequence based on this classification. Through time-series analysis, we identified the 405 Kyr long eccentricity cyc lecycle, 125 Kyr short eccentricity cycle, obliquity, and precession cycle. We emphasize the significance of the 125 Kyr short eccentricity cycle as the primary controlling factor during the deposition of the Lianggaoshan Formation. Subsequently, based on the 405 Kyr long eccentricity cycle, we established an age model for astronomical tuning, creating an astronomical age scale. The calculated sedimentation interval for the Lianggaoshan Formation ranges from 170.00 Ma to 172.74 Ma, spanning a total duration of 2.74 Ma. Meanwhile, the sedimentation interval for the Lower Liang 2 Submember is determined to be from 171.54 Ma to 172.52 Ma, lasting 0.98 Ma. Further comparison of TOC content and mineral composition with the orbital cycles reveals that TOC content and clay mineral content exhibit in-phase variations with the 125 Kyr short eccentricity. This characteristic contradicts the features of Cenozoic continental basins but aligns consistently with the characteristics of the Middle Triassic in North China. In contrast, silica minerals and carbonate minerals display anti-phase variations with the 125 Kyr short eccentricity. Different lithofacies demonstrate distinct responses to orbital cycles. Lithofacies characterized by higher organic matter content generally develop during the half-period with the maximum eccentricity. In contrast, lithofacies with lower organic matter content tend to occur during the half-cycle associated with the minimum eccentricity. Finally, based on the integrated analysis of lithological characteristics and astronomical cycles, we established two sedimentary modes: “Seasonally Pronounced Type” corresponding to the maximum eccentricity and “Seasonally Obscure Type” corresponding to the minimum eccentricity.

Enrichment mechanism of organic matter and silicon in lower Cambrian shale of the Yangtze Platform

Early Cambrian time witnessed accumulation of high-quality organic-rich siliceous shale deposits that comprise an especially promising shale gas exploration target, especially in China. The present study of the Cambrian Niutitang Formation of the shelf area of the Upper Yangtze Platform utilizes mineralogical and elemental geochemical data to aide in the paleoenvironment reconstruction of these organic-rich deposits. We are especially interested in elucidating organic carbon and silicon enrichment mechanisms of the Niutitang Formation that will benefit shale gas exploration and development of these deposits. The Niutitang Formation can be subdivided into three intervals based on lithology, gamma ray (GR) signature, and TOC abundance. Enriched TOC (average = 6.7%) and nano-size authigenic microcrystalline quartz (Qn) contents of Interval I deposits likely reflect deposition in an environment that experienced persistent euxinic and elevated organic matter delivery associated with enhanced paleoproductivity driven by hydrothermal activity. Interval II shale is interpreted to have accumulated under euxinic-ferruginous conditions that experienced the effects of robust paleoproductivity and diminished terrigenous input related to persistently warm, humid climatic conditions. Enriched TOC (average = 4.9%) and moderate microcrystalline quartz content of these deposits were likely the result of redox conditions and elevated paleoproductivity. Interval III strata appears to have accumulated under oxygenated bottom conditions that experienced moderate paleoproductivity, brackish water and elevated terrigenous detritus input driven by the establishment of cold, dry climatic conditions. The combined results of these conditions are diminished TOC content (average = 0.7%) and enrichment of the sediment in terrestrial quartz. The elevated content of authigenic quartz appears to have diminished the reservoir capacity of Niutitang Formation shale. Interval II organic-rich siliceous shale deposits of Upper Yangtze Platform shelf areas, which have the comparable authigenic microcrystalline quartz content, reservoir performance, and greater organic matter abundance as the rift trough, appear to comprise the stratigraphic horizon with the greatest exploration and development potential. Results of the present study offer theoretical guidance for future shale gas exploration and development efforts in geologically similar regions.

Investigation of Seasonal Dynamism of Peroxidase from Strains of Aspergillus sp.

Peroxidases A and B production were carried out from Aspergillus tamari and fumigates respectively isolated from petroleum hydrocarbon spilled soil. Physicochemical properties of the respective soil showed pH of 4.45 and 6.5 for soils from point 1 and II respectively and higher conductivity of 613 and 1013 (Ω-1 Cm-1), respectively when compared with the control sample. Dissolved mineral of Cl-, SO4, K, Ca, Mg in the respective soil samples from the petroleum spilled sites was significantly high when compared with the control experiment except for soil sample I which showed a relative low phosphate concentration of 1,23 in the presence of the control experiment, respectively. TOC and TOM contents were 87.91, 119.04; 108.13 and 146.42 mg/g for soil sample I, and III, respectively. In all the tested parameters, the experimented soils were significantly high than the control soil sample. Molecular tests (18S rDNA.) were used to identify the pure isolates of Aspergillia. Studies on the effect of the incubation period on the production of peroxidase from strains of ofAspergillus tamarrii sp. and Aspergillusshowed that the highest peroxidase (A and B) activity representing peroxidase from dry and wet conditions were obtained on the day 6th and 5th of the fermentation time figure peroxidase A activity peaked at pH 5 while that of peroxidase B peaked at pH 6.0; proteins with highest peroxidase activity was peak precipitated at 60% and 80% saturation of the salt for peroxidase A and B, respectively. The gel chromatogram showed single almost superimposed peaks of enzyme activity for peroxidase A and B respectively. Peroxidase A and B activity peaked at pH 4.5 and 5.0. Optimum temperature for the enzyme activity was at 50 and 60°C respectively. Km and V max of 3.45mM and 280 μmole/min; 2.44mM and 305μmole/min were extrapolated from the reciprocal curve of Lineweaver-burke at various concentrations of 2,6 DMP for peroxidase A. Fe, Ca, Co and Mn selected as their notable impact in the active site of peroxidase guided the selected were assayed in the presence of the enzymes, respectively. The stability curve obtained for the peroxidases was single biphasic which represents the first order; Peroxidase B maintained greater stability than A at its optimum pH and pH 7. The enzymes maintained greater than 50% of their activity after 30 min of incubation as activity progressively decreased up to 40% after 60 min of incubation. Thermal stability of peroxidase A and B at their respective optimum temperatures (50 and 60°C) and at 70°C showed a biphasic stability curve of peroxidase A but single phase in peroxidase B. Peroxidase B maintained greater stability than A at its optimum temperature and at 70°C. The enzymes maintained greater than 50% of their activity after 60 min of incubation. Stability curve of peroxidase A and B at 70°C showed a maximum activity of the enzymes after 30 min of incubation. However, Peroxidase B maintained greater stability than A after 60 min of incubation. Peroxidase B maintained 57.89% of its activity after 60 min while peroxidase A from fig 19 showed a residual activity of 41.2%.

Influence of Rock Fabric on Physical Properties of Shale Oil Reservoir Under Effective Pressure Conditions

Abstract The physical properties of shale oil reservoirs under overburden pressure are of great significance for reservoir prediction and evaluation during exploration and development. Based on core, thin section, and SEM observations, as well as test data such as XRD, TOC, and porosity and permeability under pressure conditions, this study systematically analyzes the variation of physical properties of different lithofacies shales in the Jiyang depression and the influence of rock fabric on the physical variation under pressure. The porosity and permeability of shale samples significantly decrease under pressure. According to the phased reduction in porosity and permeability, the pressurization process is divided into three pressure stages: low pressure (<8 MPa), medium pressure (8–15 MPa), and high pressure (>15 MPa). The reduction of porosity is fastest in the low-pressure stage and slowest in the medium-pressure stage. The reduction of permeability is fastest in the low-pressure stage and the slowest in the high-pressure stage. The rock fabric has a significant impact on porosity and permeability under pressure conditions. The permeability of laminated shale and bedded shale is higher than that of massive shale under pressure, and the permeability loss rate is lower than that of massive shales. Especially under lower pressure, the difference can be 10–20 times. In addition, the reduction rate of porosity and permeability under pressure is negatively correlated with felsic minerals content, which is positively correlated with carbonate minerals content and clay minerals content. The contribution of clay minerals to the porosity reduction rate is dominant, followed by carbonate minerals. The contribution of carbonate minerals to the permeability reduction rate is dominant, followed by clay minerals. The TOC content has no significant impact on the porosity and permeability of shales under pressure in the study due to the low maturity.

From Residue to Resource: A Physicochemical and Microbiological Analysis of Soil Microbial Communities through Film Mulch-Enhanced Rice Straw Return Strategies

Promoting rice straw in situ return is an important strategy for improving soil quality. From 2018 to 2021, we investigated the effects of rice straw return with microbial agents and film covering technology on soil physical and chemical properties at different layer depths, as well as the soil microbial community structure, in Hunan, southern China. This study was designed to evaluate the effects of microbial agents (T1), film mulch covering (T2), and the application of microbial agents combined with film mulch (T3) on the soil physicochemical properties and microbial community after rice straw in situ return. The results show that, after three years of continuous treatment, T3 significantly increased the soil temperature by 17.76–22.97%, T2 significantly increased the water content by 34.27–46.23%, and T1 and T3 significantly increased the soil pH. The addition of microbial agents combined with film mulch resulted in a notable increase in both the number of OTUs and the Chao1 index of soil microorganisms. Additionally, the model of promoting rice straw in situ return (the application of a microbial agent combined with film mulch) was shown to promote the growth of beneficial soil microorganisms. RDA was used for the investigation, and the findings showed that soil microorganisms were significantly influenced by the TOC content, pH, and water content. These findings provide evidence of an effective method for accelerating the decomposition of late rice straw and guiding soil improvement in tobacco–rice rotation regions.

Volcanically Driven Terrestrial Environmental Perturbations during the Carnian Pluvial Episode in the Eastern Tethys

AbstractThe Carnian Pluvial Episode (CPE) fingerprints global environmental perturbations and biological extinction on land and oceans and is potentially linked to the Wrangellia Large Igneous Province (LIP). However, the correlation between terrestrial environmental changes and Wrangellia volcanism in the Ordos Basin during the CPE remains poorly understood. Records of negative carbon isotopic excursions (NCIEs), mercury (Hg), Hg/TOC, and Hg enrichment factor (HgEF) from oil shales in a large‐scale terrestrial Ordos Basin in the Eastern Tethys were correlated with marine and other terrestrial successions. The three significant NCIEs in the study section were consistently correlated with those in the CPE successions of Europe, the UK, and South and North China. The U‐Pb geochronology indicates a Ladinian–Carnian age for the Chang 7 Member. A comprehensive overview of the geochronology, NCIE correlation, and previous bio‐ and chronostratigraphic frameworks shows that the Ladinian–Carnian boundary is located in the lower part of Chang 7 in the Yishicun section. HgEF may be a more reliable proxy for tracing volcanic eruptions than the Hg/TOC ratio because the accumulation rates of TOC content largely vary in terrestrial and marine successions. The records of Hg, Hg/TOC, HgEF, and NCIEs in the Ordos Basin aligned with Carnian successions worldwide and were marked by similar anomalies, indicating a global response to the Wrangellia LIP during the CPE. Anoxia, a warm‐humid climate, enhancement of detrital input, and NCIEs are synchronous with the CPE interval in the Ordos Basin, which suggests that the CPE combined with the regional Qinling Orogeny should dominate the enhanced rate of terrigenous input and paleoenvironmental evolution in the Ordos Basin.

Early stages of Type I-S kerogen formation revealed by Rock-Eval® 7S analysis of sediment from a modern halo-alkaline lake (Dziani Dzaha, Mayotte)

The Dziani Dzaha (Mayotte Islands, Indian Ocean) is a small, shallow, saline and hyperalkaline maar lake. Its surface waters are characterized by intense primary production, inducing the waters below 2 m depth to remain aphotic and anoxic all year round, at least until 2017, when a ∼5 m-long core was taken from the center of the lake. The recovered sediments were described and sampled at high resolution. They consist of laminated microbial mats, mixed with carbonate lenses or nodular beds, and rare silty detrital facies. The inorganic and organic carbon contents of 160 samples were analyzed using the Rock-Eval® method, including the Rock-Eval® 7S device which quantifies both total organic sulfur and total sulfur content, in addition to conventional Rock-Eval parameters. The Dziani Dzaha sediments are characterized by high TOC content (8.5 wt% on average and up to 27.9 wt%) and variable inorganic carbon content. HI values average 630 mg HC/g TOC and reach up to 834 mg HC/g TOC. TS content varies from 0.3 to 3.6 wt%, with TSorg/TOC ratios close to 0.01 at the top of the core and fluctuating downcore between 0.02 and 0.05. Interestingly, the pyrolysis thermal stability of sulfurized organic matter increases with depth, and the highest HI values are associated with highest Sorg content, sulfurization of organic matter being generally accompanied by reductive processes. The hydrogen- and organic-sulfur-rich sediments of Dziani Dzaha can be considered modern analogues of Type I and I-S petroleum source rock deposits, such as the Eocene Green River shales and Kimmeridgian Orbagnoux laminites, with remarkable facies and geochemical similarities. (258 words)

Biological and paleoceanographic controls on the postglacial sulfur isotope records in Arctic shelf sediments

The Arctic Ocean has experienced environmental fluctuations during the Pleistocene glacial-interglacial cycles. Since the last deglaciation, the reinundation of the Bering Strait and regional transgression have led to dramatic changes in the western Arctic Ocean, affecting coastal landscapes, depositional processes, marine ecosystem, and, inherently, biogeochemical element cycles. Here, we investigate the records of sulfur, carbon, and iron cycles in the Chukchi Sea of the western Arctic, with a primary focus on microbial sulfate reduction and subsequent pyrite formation. Variations in the pyrite abundance and sulfur isotopic composition, derived from a 10-m sediment core, demonstrate that dynamic changes in the factors governing pyrite formation – organic electron donor, reactive iron, and sulfate – are closely linked to the regional environmental conditions. In the early Holocene sediment, pyrite precipitation was impeded by the lack of organic matter, even in the presence of abundant sulfate and reactive iron. In the overlying sediment, pyrite contents increased due to vigorous microbial sulfate reduction fueled by enhanced availability of organic substrate and additional methane from the sulfate-methane transition zone. In general, the increased supply of organic matter to the Chukchi Shelf sediments can be attributed to the resumed inflow of nutrient-rich Pacific Water through the flooded Bering Strait. The increase in pyrite content, however, does not correlate exactly with either the increase in TOC or the opening of the Bering Strait, both of which precede the increased pyrite formation. These lags reflect the balance between marine primary production and terrestrial carbon sources, as well as the balance between the Pacific Inflow and the Beaufort Gyre. While a comparable increase in pyrite and TOC contents during the Holocene deglaciation has also been reported in the Black and Baltic Sea sediments, their distinct sulfur isotope records, contingent upon the availability of sulfate and reactive iron, highlight that pyrite can serve as a valuable proxy for tracking past climate and environmental change, especially in barren sedimentary records such as those found in the Arctic Ocean.

Simultaneous purification of salt and condensate by collaborated evaporation-peroxodisulfate treatment of high salinity organic wastewater

High salinity organic wastewater is commonly treated by evaporation, which produces a large amount of waste salts and condensed water containing organic compounds. The waste salts are typical classified as hazardous waste and the condensed water often requires advanced oxidation treatment before it can be biochemically treated. In this study, a synergistic treatment process combining evaporation with thermal activation of peroxodisulfate (PDS) was developed for the treatment of wastewater containing tetrabromobisphenol S (TBBPS) and Na2SO4 to reduce the content of organics in the crystal salt and condensed water. Compared with evaporation alone, the synergistic treatment process allows the complete removal of TBBPS from the crystal salt with an increase of TOC removal from 4.48 % to 94.44 %. Meanwhile, in the condensed water, TBBPS can also be completely removed with a decrease of the average TOC content from 25.56 mg/L to 4.97 mg/L. EPR detection reveals that the dominant reactive species are •OH, SO4-•, and 1O2. Moreover, the presence of SO42- can enhance the conversion of •OH to SO4-•, thereby improving the utilization of reactive species by increasing the contribution of SO4-•. The degradation intermediates of TBBPS were detected by IC and LC-MS, based on which the possible degradation mechanism of TBBPS was proposed. The synergistic treatment process can not only promote the resource utilization of waste salt and reduce the difficulty of condensed water treatment but also improve the stability of the evaporation system.

Assessment of anthropogenic pollution in Guanabara Bay (SE Brazil) through biogeochemical data and stable isotope mixing models.

This work intends to identify pollution sources along the margins of Guanabara Bay (GB; SE Brazil) through a multiproxy approach and Bayesian stable isotopic mixture model (BSIMM). For this purpose, 33 surface sediment samples were collected and analyzed for granulometry, geochemistry (heavy metals, total organic carbon-TOC, stable isotopes of carbon and nitrogen-δ13C and δ15N, Rock-Eval pyrolysis parameters-REPP), and physicochemical parameters. Metal concentrations (E) dissolved in water (EW), adsorbed by organic matter (EOM) and by Mn hydroxides (EMn), and total extracted concentrations (ET) were analyzed. Sampling was conducted in 2018 after an oil spill from Reduc Oil Refinery. Potential Ecological risk index (PERI), based on metals, classified 85% of the analyzed stations as having moderate to considerable ecological risk. The metals with the potential to cause the highest ecological risk were CdW, CdOM, PbOM, and HgOM. The combination of BSIMM and REPP data was an effective proxy for oil spill detection by indicating the presence of polycyclic aromatic hydrocarbons (PAHs). Relatively high TOC contents suggested that the analyzed stations are eutrophicated environments. BSIMM discriminated three groups of stations with different sources of organic matter (OM), endorsing the result previously shown by the cluster analysis: (A) Niterói region, Botafogo marina, Glória marina, Fiscal and Fundão islands with diffuse sources of OM, including marine phytoplankton and material of continental origin from highly polluted rivers and domestic sewage; (B) region near Fundão and Governador islands and Mangue Channel outlet with OM (≃70%) supplied by highly polluted streams and a small contribution of PAHs; (C) Duque de Caxias and Botafogo-Urca inlet with significant contributions of PAHs, materials from C-3 plants and rivers polluted by urban sewage. Results of linear regressions in conjunction with BSIMM indicate that HgMn and PbOM mainly affect Group A's stations. Although the eastern margin of GB (Niterói; Group A) showed greater oceanic interaction than the other groups, it presented substantial concentrations of metals, potentially harmful (i.e., Hg and Pb) to marine biota and human health.

Volcanic and climatic impacts on silicon abundance in shale: Implications for the expansion of Permo-Carboniferous terrestrial plants in North China

Silicon (Si) is known as an important regulator of the global carbon cycle via its effect on silicate weathering in continents and phytoplankton productivity in the oceans. It is also beneficial to plants by improving their resistance to biotic and abiotic stresses. Detailed analysis of geological record of Si in sediments underpins our understanding of ecosystem evolution over geological time. Here, we unravel the mystery of low Si content in Permo-Carboniferous shales from the central North China and link the terrestrial Si fluxes to the thriving forest ecosystems at that time. Provenance fluctuations as indicated by Zr/TiO2 are well explained by episodic volcanic input which are identified by elevated Zr/TiO2 and lowered V/Al2O3 and Cr/Al2O3. CIA and Ga/Rb and K2O/Al2O3 ratios imply cyclic changes of climate in an overall warm and humid condition. The covariation between the volcanic indicators and climatic proxies indicates that the volcanism forced the climate cycles. Despite the felsic sources (high Zr/TiO2 and Th/Sc ratios and low Zr/Sc ratios), the Si-poor shales are universal in Permo-Carboniferous across the North China Block. The enhanced continental weathering of mineral silicates and the hydrolysis of volcanic materials released silica into the environment and led to the eventual deposition of Si-poor shales. The shales lacking in Si tend to have larger TOC contents except for the most distal shales. It implies that the sufficient supply of dissolved-Si in environments may benefit the expansion of terrestrial plants in Permo-Carboniferous and therefore the accumulation of organic matter in the shales. This work provides new insight into feedback linking volcanism, climates, terrestrial dissolved silica flux, and terrestrial ecosystems in Permo-Carboniferous North China Block.

Genesis of gray sandstone within the red beds in HLJ-DL uranium deposit, southwest Songliao Basin and its relationship with uranium mineralization

The search for uranium deposits in the red beds is currently a hotspot in China's sandstone-type uranium exploration efforts. The typical occurrence of uranium deposits is within gray sandstone layers amidst the red beds, where the distribution of these gray sand bodies dictates the presence of uranium deposits. Hence, delving into the genesis of gray sandstone within the red beds proves beneficial for both uranium exploration and unraveling the ore-forming mechanisms. However, there is currently significant controversy surrounding the genesis of gray sandstone in the red beds. This paper focuses on the typical uranium deposit in the red beds—the HLJ-DL uranium deposit in the southwestern part of the Songliao Basin. It investigates the genesis of gray sandstone within uranium-bearing rock series and its relationship with uranium mineralization. The lithology of representative drill cores, including the red sandstone for comparative study, is methodically examined, along with their elemental geochemistry as well as carbon and oxygen isotope characteristics. The petrological characteristics suggest that both the gray and red sandstone share similar compositions of clastic particles, indicating minimal influence of the source rock on the sandstone color. The gray sandstone displays comparable TOC content (averaging around 0.05 %) and δ18OPDB values (averaging around −16 ‰) to the red sandstone. However, it exhibits relatively higher δ13CPDB values (averaging −0.26 ‰), whereas the average δ13CPDB value for the red beds is −1.61 ‰. The data indicate that the gray sandstone is less affected by hydrothermal or hydrocarbon fluids. Compared to the red sandstone, which has relatively higher Cu/Al values (averaging 1.09) and Fe3+/Fe2+ ratios (averaging 3.37), the gray sandstone exhibits low Cu/Al values (averaging 0.44) and a low Fe3+/Fe2+ ratio (averaging 0.36), suggesting its formation in a relatively reducing environment. The reducing conditions necessary for the formation of gray sandstone may stem from the climate becoming relatively warm and humid, irrespective of whether it originates from the original sedimentary environment or is induced by the reducing pore water discharged from dark mudstones. The chemical weathering index of fine-grained sediments indicates that, the gray sandstones were commonly configured in relatively humid-warm climate with fairly low dissolved oxygen content in the bottom water. Additionally, the deposition of the uranium-bearing rock series experienced alternating climatic changes, rather than consistently being in a humid-warm climate. This resulted in the sand bodies with low TOC content, insufficient reducing potential, and uranium mineralization primarily occurring in the interior of the basin. Organic matter has a relatively weak control over uranium mineralization, whereas uranium mineralization shows a certain correlation with iron reduction. The ore-forming fluid was uranium-rich oxygenated atmospheric water. Dark-colored mudstones, formed under humid-warm climatic condition, contain relatively high TOC contents (avg. 0.43 %) and exhibit a strong reducing capacity. The reducing pore water in dark-colored mudstones excreted into the adjacent sandstones under compaction during the early diagenesis, is able to serve as a vital reducing agent in later-stage uranium mineralization. Additionally, certain dark-colored mudstones with high uranium content (up to 944 ppm) undergo significant uranium pre-enrichment, providing a partial uranium source for uranium mineralization.

Treatment of pharmaceutical wastewater by a sequential KMnO4/CoFe2O4-mediated catalytic ozonation process

Pharmaceutical compounds, which are of utmost concern, have found their way into natural water bodies, causing numerous problems for both human health and ecosystems. In this study, an integrated system including potassium permanganate (PM) pre-oxidation, followed by a heterogeneous catalytic ozonation process (HCOP) using CoFe2O4 magnetic nanoparticles (CF MNPs), and an activated sludge-based biological treatment (BT) was employed for the first time to treat pharmaceutical wastewater (PWW). In this regard, the effluent from PM pre-oxidation process was used as a batch for the HCOP, and the effluent was used as a batch for the BT process. The results showed that PM pre-treatment of PWW (PM dose = 1264 mg/L and pH = 8.0) reduced the COD content of the PWW from 900 ± 50 to 443 ± 10 mg/L within 120 min of reaction time. The application of HCOP for further treatment of PWW dramatically enhanced COD and TOC removal compared with the single ozonation process (SOP). Under optimum conditions (pH = 10, O3 = 4.0 mg/L, and CF MNPs = 1000 mg/L), HCOP successfully reduced the COD and TOC contents of PWW by 37 % and 46.1 %, respectively, after 120 min of treatment. The consecutive combination of PM pre-treatment followed by HCOP exhibited good potential and reduced COD by over 69 %, resulting in a residual COD of less than 280 mg/L. A biodegradability ratio of over 81 % and residual COD of 54 mg/L for the PWW treated by the PM/HCOP/BT integrated system indicated that biodegradability was enhanced, and a high fraction of refractory organic compounds was effectively removed. In conclusion, the PM/HCOP/BT integrated system is an efficient, synergistic, and easy-to-operate technique for enhancing the biodegradability of PWW.