High Organic Carbon Research Articles

Comparative Effects of Organic Nutrient Sources on Green Gram (Vigna radiata L.) Quality and Soil Properties

A field experiment was conducted during summer season of the year 2020-21 on organic certified plot A-7 at Agronomy Farm, B. A. College of Agriculture, Anand Agricultural University, Anand, Gujarat. Different sources of organic manures were tested using randomized block design with four replications. The treatment T7 (50% N through FYM followed by Seed treatment of Rhizobium) recorded significantly higher available nitrogen content (212 kg/ha) in soil and also same behaviour observed in available phosphorus content in soil. The treatment T9 (50% N through castor cake followed by Seed treatment of Rhizobium) recorded significantly higher available phosphorus content in soil. Significantly higher value of EC of soil (0.18) was found in treatment T1, which was significantly higher EC of soil (0.11) which was recorded with treatment T9. Higher organic carbon (0.65%) of soil after harvest of green gram was observed in treatment T8. Significantly higher nitrogen content in seed of green gram was obtained with application of treatments T10. Treatment T2 [Rhizobium (5.0 mL/kg seed treatment and 1.0 L/ha soil application)] recorded significantly higher Rhizobium population in soil at harvest of green gram. Subsequent, treatment T6 (100 % N through neem cake) recorded significantly higher phosphorus solubilising bacteria (PSB) population in soil as compared to control. The maximum net return 63287 INR/ha was obtained with application of treatment T10 (50% N through NC + Rhizobium seed treatment) followed by treatment T7 (50% N through FYM + Rhizobium seed treatment) with net realization of 54063 INR/ha. With respect to benefit cost ratio, the highest 3.62 BCR was achieved with Treatment T7, which closely followed by treatment T2 (Rhizobium seed treatment + 1.0 L/ha soil application) having BCR of 3.52.

Characteristics and main controlling factors for the development of shale micro pore-fracture in Tiemulike Formation, Yining Basin

Research on the type, size, structure, and other characteristics of shale micro pore-fracture and their genesis is one of the core index for Shale gas study. Based on systematically collected shale samples from outcrop profiles and well cores, the experiments of thin-section observation, scanning electron microscopy, energy-dispersive X-ray spectroscopy, whole-rock analysis, rock–eval pyrolysis and basin simulation analysis were performed to study the micro pore-fracture characteristics and its main controlling factors for the development of shale pores in Tiemulike Formation in Yining Basin. The results show that four types of micro pore-fractures were identified: organic hydrocarbon-generating micro pores, granular dissolved micro pores, intergranular micro pores, and micro-fracture. The development of micro pores in shales is influenced by the internal material composition of the shale reservoir and external temperature conditions. The high organic carbon content with a high degree of thermal evolution led to the development of numerous micro pores, and the main micro pores were produced by shrinking the hydrocarbon generation volume due to the thermal evolution of organic matter. The development of micro-fractures was found to be favoured by the high content of brittle minerals and overpressure in the formation.

Optimization of hydrogen production using a coculture of Chlamydomonas reinhardtii and activated sludge bacteria

The production of biophotolytic hydrogen (H2) relies on the effective management of oxygen (O2) levels. Coculturing bacteria with microalgae helps mitigate the excess O2 produced by algal cells. After depleting O2, the bacteria activate the enzyme hydrogenase in microalgae, leading to H2 production. In this study, Chlamydomonas reinhardtii was cocultured with indigenous bacteria from activated sludge at varying algae-to-bacteria ratios (1:1, 1:1.5, 1:2, 1:2.5, and 1:3 v/v), with an illumination intensity of 2.8 mmol/m2/s (31 × 103 lux). The 1:1.5 v/v ratio yielded the highest H2 volume (1162 mL/L) and the highest O2 concentration (153.2 mL/L) over a 6-day period. Production of all gaseous components ceased for all ratios as the pH dropped below 4 due to acetate accumulation, and the concentration of acetate reached approximately 1 g/L by the end of each experiment. Gas composition analysis after the first day of coculture revealed that H2, CO2, N2, and O2 constituted 25%–46%, 20%–40%, 5%–30%, and 1%–10% of the total gas volume, respectively. Glucose (10 g/L) was introduced as an external carbon source for all cultures. After 6 days, the coculture maintained a high total organic carbon (TOC) level of 3.1 g/L, whereas the initial TOC ranged between 3.9 and 4.3 g/L. The findings illustrated a significant correlation between H2 production, acetate accumulation levels, and O2 consumption. The algae–activated sludge coculture method substantially enhanced H2 production compared with previously published methods employing only one or two types of bacterial cultures, underscoring its potential for more efficient biophotolytic H2 production.

Mechanistic insights into the co-transport of microplastic degradation products in saturated porous media: The key role of microplastics-derived DOM

Microplastic-derived dissolved organic matter (MP-DOM) forms from the aging of microplastics (MPs), but the co-transport behavior of MP-DOM and aged MPs (AMPs) remains poorly understood. This study investigates the co-transport of AMPs and MP-DOM generated from original MPs (OMPs) over a wide range of environmentally relevant conditions. The transport of AMPs and MP-DOM changes as the degree of aging increases, specifically related to changes in their physicochemical characteristics. Results showed that the order of migration ability was MP-DOM > AMPs > OMPs under almost all tested conditions. The change of hydrophobicity of MP-DOM and AMPs, as well as small molecular weight of MP-DOM, was primarily responsible for this order. The role of MP-DOM as a degradation product in the co-transport process is notably significant under various environmental conditions because of its high mobility and organic carbon fraction within the system. Furthermore, it is important to note that MP-DOM affected the transport of MPs through a combination of positive and negative effects. Key mechanisms include electrostatic repulsion caused by protonation reactions triggered by the acidic pH of MP-DOM, steric hindrance, and competition for retention sites on media surfaces. This study contributes to a deeper understanding of the transformation and fate of MPs in complex environmental systems.

Environmental degradation and recovery after termination of whaling in sub-Antarctic fjord, South Georgia

Polar ecosystems are considered very fragile, however, due to the short observation record it is hard to assess the recovery processes of the coastal and fjord environments after a major disturbance. Here, we provide a unique case study from South Georgia (sub-Antarctic), an area seriously affected by the whaling industry. The study focuses on King Edward Cove, serving as a sheltered harbor for the former whaling station at Grytviken, as well as other parts of Cumberland Bay considered to represent generally pristine areas. We studied 210Pb dated sediment cores, which were subjected to analysis of sediment geochemical composition, concentrations of anthropogenic organic markers and biomarkers, foraminiferal assemblage changes, as well as sedimentary ancient DNA. Three distinct phases have been identified. The oldest one, predating ca. 1970, recorded the whaling period, and was characterized by anoxic conditions, high organic carbon content, contamination with heavy metals, organic markers, distinct DNA signature and lack of foraminiferal microfossils. It took only a few years to establish a new ecosystem with a fully developed foraminiferal assemblage and decreased contamination characteristic for the middle phase (ca. 1970–2000). Ancient DNA suggests macro-zoobenthic recovery being delayed by a several years in comparison to benthic foraminifera. In the youngest period, around Cumberland Bay, the increase of iceberg rafted debris from rapidly retreating tidewater glaciers was noted, while the improved oxygen availability in bottom waters in King Edward Cove can be likely ascribed to frequent water mixing due to increasing traffic of large cruise vessels. The recorded pace of ecosystem recovery from major anthropogenic disturbance appears similar to that observed in the temperate fjords from the Northern Hemisphere, however, the effects of new anthropogenic threat and the ongoing climate change are already resulting in the new ecosystem disturbance.

The Pyrolysis of Biosolids in a Novel Closed Coupled Pyrolysis and Gasification Technology: Pilot Plant Trials, Aspen Plus Modelling, and a Techno-Economic Analysis

Pyrolysis is gaining recognition as a sustainable solution for biosolid management, though scaling it commercially presents challenges. To address this, RMIT developed a novel integrated pyrolysis and gasification technology called PYROCO™, which was successfully tested in pilot-scale trials. This study introduces PYROCO™ and its application to produce biochar, highlighting the biochar properties of the results of the initial trials. In addition, an energy analysis using semi-empirical Aspen Plus modelling, paired with a preliminary techno-economic assessment, was carried out to evaluate the feasibility of this technology. The results show that the PYROCO™ pilot plant produced biochar with a ~30 wt% yield, featuring beneficial agronomic properties such as high organic carbon (210–220 g/kg) and nutrient contents (total P: 36–42 g/kg and total N: 16–18 g/kg). The system also effectively removed contaminants such as PFASs, PAHs, pharmaceuticals, and microplastics from the biochar and scrubber water and stack gas emissions. An energy analysis and Aspen Plus modelling showed that a commercial-scale PYROCO™ plant could operate energy self-sufficiently with biosolids containing >30% solids and with a minimum calorific value of 11 MJ/kg. The process generates excess energy for drying biosolids and for electricity generation. Profitability is sensitive to biochar price; prices rise from AUD 300 to AUD 1000 per tonne, the NPV improves from AUD 0.24 million to AUD 4.31 million, and the payback period shortens from 26 to 12 years. The low NPV and high payback period reflect the use of a relatively high discount rate of 8%, chosen to be on the conservative side given the novel nature of the technology.

Co-application of glucose and phosphorus with recalcitrant high-carbon soil amendments improves N retention in a reclaimed soil: a long-term incubation study

ABSTRACT Incorporation of soil amendments with high organic carbon content (HCA) can reduce losses of mineral nitrogen (N) from agricultural soils. The magnitude of N immobilization and remobilization is strongly controlled by the availability of carbon (C) and phosphorus (P). However, the exact mechanisms and interactions between C, N, and P availability are poorly understood. An eight-month incubation experiment was conducted on recultivated mine soil with low organic C, mineral N and P background concentrations to investigate the effects of HCA in combination with 13C-labelled glucose and mineral P fertilization on greenhouse gas emissions, soil nutrient status (dissolved organic C (DOC), nitrate (NO3 –), extractable P), and microbial biomass growth. The experiment had a factorial design of one N level × two P levels × six C treatments (control, wheat straw, poplar sawdust, glucose, and combinations of wheat straw or sawdust with glucose). The HCA increased the cumulative CO2 and CH4 emissions but decreased N2O emission, except for wheat straw. Addition of 13C-labelled glucose decreased the cumulative CH4 emission by 59 and 85 % in the sawdust and sawdust + P treatment, respectively. Glucose application reduced the NO3 – content in the HCA-amended soil by 26–64 %, while P fertilizer further decreased the NO3 – content in the wheat straw and sawdust treatments by 20 and 24 %, respectively. Both HCA and glucose treatments promoted microbial biomass growth and reduced the soil mineral N content. The δ13C of microbial biomass (δ13CMB) showed an increasing trend during the whole experiment, although 13C-labelled glucose was added only once at the beginning of the experiment. Addition of HCA decreased δ13CMB, while P addition had the opposite effect. In conclusion, adding a readily available C source to HCA may increase the efficacy of retaining N in post-harvest soils, particularly of more recalcitrant types of HCA like sawdust.

Enhanced Organics Removal Using 3D/GAC/O3 for N-Containing Organic Pharmaceutical Wastewater: Accounting for Improved Biodegradability and Optimization of Operating Parameters by Response Surface Methodology

Pharmaceutical industry effluents often contain high concentrations of refractory organic solvents, chemical oxygen demand (COD), and total dissolved solids (TDSs). These wastewaters, including N-containing organic solvents known for their persistence and toxicity, pose significant environmental challenges. The study evaluated the efficacy of 3D/Granular Activated Carbon (GAC)/O3 treatment compared to linear process additions when treating real pharmaceutical wastewater, and revealed a 2.73-fold enhancement in COD mineralization. The process primarily involves the direct oxidation of monoprotic organic acids found in real pharmaceutical effluents, such as acetic and formic acid, crucially influencing mineralization rates. Optimal conditions determined via the response surface methodology were 125 g/L GAC, 30 mA/cm2, and 75 mg/L O3, achieving high total organic carbon (TOC) and COD removal efficiencies of 87.19 ± 0.19% and 89.67 ± 0.32%, respectively (R2 > 0.9), during verification runs. Current density emerged as the key parameter for organic abatement, aligning with the emphasis on direct oxidation at the anode surface. This integrated approach enhances biodegradability (BOD5/COD) and reduces acute toxicity associated with persistent N-containing solvents, demonstrating promising applications in pharmaceutical wastewater treatment.

A Paleoenvironmental Reconstruction of Lake Vrana on the Island of Cres (Croatia) Based on the Geochemistry and Mineralogy of the Late Pleistocene and Holocene Sediments

A 7.4 m long sediment core has been retrieved from the central part of Lake Vrana on the island of Cres to reconstruct the paleoenvironmental conditions. Lake Vrana is the deepest freshwater lake in Croatia, located in the karst region of the eastern Adriatic coast. A dated sediment sequence in Lake Vrana of 4.4 m has spanned the past 16.4 kyr, and it featured a dynamic sediment deposition until the beginning of the Holocene, including strong sediment input and supply to the lake by runoff sediments of dolomitic origin from the catchment in the period 16.4–14.4 cal kyr BP. High organic carbon content, which originates from mixed terrestrial and aquatic origins in the periods 14.4–13.3 cal kyr BP and 12.7–11.7 cal kyr BP, indicates fluctuating lake levels in shallow water environments during the Late Glacial to Holocene transition. The Holocene sequence indicates the development of more stable conditions and continuous sediment deposition, characterized by an increasing trend of siliciclastic sediments delivered into the lake during the early Holocene (11.7–10 cal kyr BP) and dominantly from 8 to 4.4 cal kyr BP, indicating enhanced input and erosion, which coincides with the humid and pluvial period recorded in the central Mediterranean region. It is followed by sediments with high organic carbon content between 4.4 and 1.6 cal kyr BP, which points to higher lake productivity. Calcite sedimentation prevailed between 1.6 to 0.4 cal kyr BP, indicating stable deeper-lake conditions. Predominantly, siliciclastic sediments from 0.4 to 0.1 cal kyr BP pointed to erosion during the Little Ice Age (LIA), with enhanced precipitation and sediment discharge from the catchment. The re-establishment of calcite sedimentation has been observed over the last 100 years.

Organic carbon decomposition temperature sensitivity positively correlates with the relative abundance of copiotrophic microbial taxa in cropland soils

Revealing the relationships between the temperature sensitivity of soil organic matter decomposition (Q10) and microbial communities is critical to predict ecosystem feedbacks to global warming. However, the relationships are still far from well understood, especially within the low latitude regions. To address this knowledge gap, soil samples were collected from >100 cropland sites in Southwest China, a region with highly diverse climatic and environmental conditions. The results showed that Q10 values substantially varied across the region, ranging from 1.85 to 6.81, with an average value of 3.27. They were significantly positively correlated with the contents of soil organic carbon, while negatively correlated with the ratios of soil dissolved organic carbon to total organic carbon content. This indicates that soils with high organic carbon contents are more vulnerable to global warming. Further analysis suggested that Q10 values were positively correlated with soil microbial respiration rates, fungal abundance, prokaryotic diversity, and the relative abundance of copiotrophic microbial lineages, but negatively correlated with the proportions of oligotrophic microbes and microbial co-occurrence network degree. The structural equation modeling analysis suggested that soil organic carbon and its quality, as well as microbial attributes were the main factors explaining the variation in Q10 values. The findings in this study highlight the crucial and complex roles of soil microbiome in determining ecosystem feedbacks to global warming.

Impact of gas adsorption of nitrogen, argon, methane, and CO2 on gas permeability in nanoporous rocks

Gas adsorption on the surface of nanoporous rocks is an important process that occurs in many applied scenarios such as shale gas production or CO2 enhanced gas recovery or storage. While there are few theoretical considerations on the effect of gas adsorption on permeability, a systematic laboratory investigation of the impact of gas adsorption on gas flow and permeability is still lacking. In this paper, permeability of four adsorptive gases, i.e., nitrogen, argon, methane, and carbon dioxide, was measured, along with helium permeability, for two nanoporous rock samples that have high and low total organic carbon (TOC) content, respectively. The measurements were conducted at a range of pore pressures from 150 to 1500 psi (1.03–10.34 MPa). Gas adsorption isotherms were also measured at the same conditions. A mathematical model that considers adsorption with specific boundary conditions for the experimental setup was used for data analysis. The results show that gas adsorption causes larger drop in pressure decay and greater retardation in pressure equilibrium. However, the reduction of permeability relative to helium (25%–46%) is similar for gases with different levels of adsorption, indicating the occurrence of single-layer adsorption for these gases. Comparison between the two samples further supports the concept of single-layer adsorption and signifies the impact of pore size on the permeability reduction due to adsorption. These new findings deepen the fundamental understanding and provide important clarification on the effect of gas adsorption on gas flow and permeability in nanoporous rocks.

Natural and anthropogenically driven change of organic carbon burial rate in two alpine lakes from the southeastern margin of the Tibetan Plateau

The rate of organic carbon (OC) burial in lakes depends considerably on natural and anthropogenic factors. Delineating how and to what extent potential drivers shape a lake’s OC burial rate is crucial for anticipating OC sequestration under future environmental change scenarios. Alpine lakes provide valuable opportunities for studying the influence of climate warming and atmospheric nitrogen (N) deposition on OC burial in lakes, owing to the lack of human activities in their catchments; however, this aspect has not been sufficiently documented. Here, the OC burial rate was reconstructed in two alpine lakes (Heihai and Jiren) from the southeastern margin of the Tibetan Plateau over the past ∼ 160 years, and the associated drivers were identified by resolving the temporal trends in organic matter (OM) input from specific sources to lake sediments via paleolimnological methods. The results demonstrated a consistently low OC burial rate (6.21–10.86 g m−2 yr−1) in Lake Heihai. The low hydrogen index (HI), moderate Paq, and high long-chain n-alkane flux revealed that submerged macrophytes and terrestrial plants are major contributors to the sequestrated OC. The notable decrease in the OC burial rate after 1980 was hypothesized to be caused by regional climate warming during this period because a greater export of terrestrial materials under such a climate can inhibit light penetration, diminishing submerged macrophyte productivity and OM input. In contrast, the synchronous input of higher amounts of terrestrial plant OM was largely degraded owing to the increased water temperature and the intensification of water column stratification. In Lake Jiren, a notably high OC burial rate (13.82–46.75g m−2 yr−1) was observed. The high HI, Paq, and short-chain n-alkane flux showed that phytoplankton and submerged macrophytes were the major contributors to the sequestrated OC. The two-phase increase in the OC burial rate in this lake, including a slow increase after 1947 and a rapid increase after 1983, might have resulted from strengthening aquatic primary productivity and OM input, driven by anthropogenic intensification of nutrient emissions, especially reactive N, from highly urbanized areas and the subsequent long-term atmospheric transport and deposition of these materials over the lake basin. A comparative analysis of the results between the two lakes suggested that atmospheric N deposition has a stronger influence on the OC burial than climate warming. These drivers affect the OC burial rate by altering aquatic productivity rather than the terrestrial OM input. This study provides a basic for predicting future OC burial scenarios in warmer climates with more intense anthropogenic N emissions.

Amelioration of Soil Fertility by the Application of Different Fruit Waste Composts

The soil health status of Bangladesh decreased day by day, particularly organic matter and major nutrient content. The organic matter content in most of the agricultural soil in Bangladesh is <2%, which indicates poor soil health condition. In Bangladesh, almost every day, an enormous amount of waste material is produced from different kinds of seasonal and unseasonal fruit’s peels. Lack of proper recycling methods, most of these wastes are thrown away in drains, cannels, rivers, etc. which indicates a major threat to environmental safety. Composts derived from the wastes of different fruit’s peels can be an excellent source of organic matter and essential nutrients for soil health improvement. Therefore, the present study was carried out to evaluate the changes in physicochemical properties and nutrient contents of experimental soil treated with compost prepared from different types of fruit’s waste. The compost was prepared accordingly using different types of fruits waste and then the collected compost was thoroughly mixed with the soil and kept for six months. The experimental treatment consisted of three organic composts (jackfruit peel compost, mango peel compost, and banana peel compost) and three rates of application (1000, 1500, and 2000 kg ha-1). The experiment was arranged in a factorial completely randomized design and replicated thrice. The analyzed data showed that, the physicochemical properties and nutrient contents of experimental soil varied significantly with the use of different types of fruit’s wastes compared to no waste added soil, except in the case of particle size. Soil mixed with mango peel compost at a rate of 2000 kg ha-1 resulted in a higher available N content (2520 mg kg-1) and available P content (42.56 mg kg-1), whereas the available K content (219.88 mg kg-1), EC (1.55 dS m-1) and CEC (1209.56 meq 100g-1) were found higher in soil treated with banana peel compost of 2000 kg ha-1. On the other hand, soil treated with jackfruit peel compost of 1500 kg ha-1 showed the higher available Ca content (1533.33 mg kg-1) and the jackfruit peel compost of 2000 kg ha-1 resulted in the higher organic carbon (1.98%) and organic matter (3.41%). The findings of this experiment revealed that, compost prepared from different types of fruit peels can be an excellent source of organic matter and nutrients and among the tested composts, mango peel compost was better to improve the physiochemical properties of soil and supply sufficient nutrients for plant growth.

Mechanisms of Reservoir Space Preservation in Ultra-Deep Shales: Insights from the Ordovician–Silurian Wufeng–Longmaxi Formation, Eastern Sichuan Basin

This study aims to explore the reservoir characteristics and formation mechanisms of ultra-deep shale gas in the Ordovician–Silurian Wufeng–Longmaxi Formation in the Sichuan Basin in order to provide theoretical support and practical guidance for the exploration and development of ultra-deep shale gas. With recent breakthroughs in ultra-deep shale gas exploration, understanding its organic matter development, mineral composition, and reservoir space characteristics has become particularly important. The background of this research lies in the significant potential of ultra-deep shale gas, which remains inadequately understood, necessitating an in-depth analysis of its pore structure and reservoir quality. Through a systematic study of the ultra-deep shale in well FS1 of Sichuan Basin, that the following was found: (i) The ultra-deep shale in the Wufeng–Longmaxi Formation is mainly composed of quartz and clay minerals, exhibiting high total organic carbon (TOC) and high porosity characteristics, indicating it is in an overmature thermal evolution stage. (ii) Organic pores and microcracks in the ultra-deep shale are more developed compared to middle-shallow and deep shale, forming a complex pore structure that is conducive to gas storage. (iii) In the diagenesis process, the dissolution and recrystallization of the biogenic skeleton promote the cementation between autogenetic quartz particles, forming a rigid skeleton that effectively inhibits the impact of mechanical compaction. (iv) The overpressure environment created by the hydrocarbon generation process, along with gas production from hydrocarbon cracking, can effectively offset the mechanical compaction of overburden pressure on micropores, and this overpressure environment also promotes the further development of microfractures, which is beneficial for the development and preservation of ultra-deep shale pores. In summary, this study not only reveals the reservoir characteristics and formation mechanisms of ultra-deep shale but also provides essential references for the exploration and development of ultra-deep shale gas in the Sichuan Basin and similar regions, emphasizing the ongoing significance of research in this field.

Proximity to inlet channel drives spatial variation in sediment carbon across a lagoonal seagrass meadow

Seagrass meadows can be sinks for organic carbon, but estimates of global organic carbon stocks are complicated by substantial spatial variability in organic carbon burial observed within meadows. To improve estimates of organic carbon burial in seagrass meadows, it is necessary to understand the causes of the spatial heterogeneity. This study investigated relationships between spatial patterns in sediment organic carbon storage and accretion rates, hydrodynamics, and proximity to sources of organic carbon in a current-dominated Zostera marina Linnaeus meadow in Menemsha Pond, Massachusetts, USA. Sediment and velocity measurements were conducted at six stations along a 150-m transect across the meadow oriented perpendicular to the pond's unvegetated inlet channel. The meadow's edge near the channel had higher organic carbon than the channel as well as the highest organic carbon within the meadow. With increasing distance from the meadow's edge, all of the following decreased: sediment organic and total carbon, sediment accretion rates, peak tidal velocity, sediment trap mass deposition rate, and the relative contribution of non-seagrass sources to sediment organic carbon. Lower tidal velocities farther from the inlet channel reduced sediment resuspension, consistent with lower sediment trap mass deposition, which should enhance organic carbon content and organic carbon accretion rates. However, the opposite trend of decreasing organic carbon content (>50 % across the transect) and decreasing accretion rates with distance from channel was observed. This suggested that the local hydrodynamic intensity was not controlling organic carbon accretion, which was instead constrained by supply limitation and controlled by the lagoon-scale flow circulation.

The effects of roots and earthworms on aggregate size distribution and their associated carbon under contrasting soil types and soil moisture conditions

Soil’s potential as a carbon sink is uncertain due to biotic and abiotic interactions. Soil aggregates are important carriers of organic carbon (OC), and clarifying the response of aggregates and their associated OC to plant roots and earthworms can better understand the carbon cycle in terrestrial ecosystems. Herein, we determined the regulatory role of plant roots (Lolium perenne) and earthworms (Metaphire tschiliensis) in isolation and in combination on aggregate size distribution and their associated OC and readily oxidizable OC (ROOC) under contrasting soil types (Phaeozems and Anthrosols) and soil moisture conditions (constant wetting, CW; wetting–drying cycle repeated four times, 4WD) by a laboratory microcosm experiment. Results showed that earthworm presence significantly increased plant biomass by 30 % and 221 % in Phaeozems and Anthrosols, respectively (p < 0.05). For Phaeozems, plant alone (P) and plant and earthworm in combination (PE) had lower proportion of large aggregate (5–8 and 2–5 mm) than bare soil (CK) under 4WD condition (p < 0.05). For Anthrosols, the PE treatment decreased the proportion of 5–8 and 2–5 mm aggregate by 45 % and 25 %, respectively, under CW condition, and decreased the proportion of 5–8 mm aggregate by 37 % under 4WD condition (p < 0.05). Moreover, the proportion of 5–8 and 2–5 mm aggregate in P treatment was lower under CW condition (6.92 % and 22.13 %) but was higher under 4WD condition (11.49 % and 32.55 %) than those in CK (14.69 % and 29.91 %; 8.85 % and 20.56 %) (p < 0.05). Our results further indicated that the PE treatment had relatively higher OC and ROOC contents, especially for small aggregates in Anthrosols. The study indicates that plant roots and earthworms significantly influence aggregate turnover and the carbon cycle, with soil type and moisture playing a crucial role.

Sedimentary factors controlling the organic matter enrichment in oil shale, Seyitömer Lacustrine Basin, Western Anatolia: New implications from organic and inorganic geochemistry

AbstractWestern Anatolia, an important segment of the Alp‐Himalayan Belt, hosts numerous Neogene lacustrine basins with potential oil shale reserves surpassing 1.6 billion tonnes. Among these basins, the Seyitömer Basin (Kütahya) stands out, containing oil shales that are intercalated with claystone, marl, limestone and coal layers. This study presents a comprehensive dataset of organic and inorganic chemistry to gain insight into the palaeoclimate and palaeoenvironmental factors that control the enrichment of organic matter. The studied samples exhibit high total organic carbon contents, averaging 12.85% (ranging from 2.22 to 36.21%), high hydrogen indices (486–812 mgHC/g rock) and low oxygen indices (33–70 mgCO2/g total organic carbon), indicating their substantial hydrocarbon‐source potential. These characteristics indicate predominantly ‘excellent’ to occasionally ‘very good’ source rock qualities and very high oil potential. Their pyrolysis, gas chromatography and gas chromatography–mass spectrometer parameters indicate an immature‐early mature characteristic for Seyitömer oil shale samples. They comprise dominantly Type‐I kerogen with minor Type‐II kerogen and lacustrine algal organic matter. Their sedimentological characteristics, along with various geochemical values, such as total organic carbon versus S, B versus Ga and dibenzothiophene/phenanthrene, reveal a moderately deep fresh/brackish to saline lacustrine environment. The Ga/Rb, K/Al and Sr/Cu ratios suggest dominantly humid and warm climate conditions, occasionally interrupted by periods of less humidity. The prevalence of warm and humid climate conditions leads to intense chemical weathering processes, supported by high Chemical Index of Alteration and low Rb/Sr ratios in the associated oil shale samples. Intense chemical weathering and high runoff resulted in dissolved nutrient enrichment, promoting ecological dynamics favourable to increased productivity. Their low Pr/Ph and Mo/total organic carbon ratios, high Ni/Co ratio and, relatively low MoEF/UEF ratio, along with well‐developed lamination of the oil shales, indicate the presence of anoxic conditions in the bottom water. These anoxic conditions would have facilitated the preservation potential of organic matter in the samples. Thus, the palaeoclimate conditions integrated with sedimentary factors have an important role in the ecological dynamic and physical–chemical environmental conditions, ultimately contributing to the organic matter enrichment of the studied samples. This work provides a case study to better understand the sedimentary factors controlling organic matter enrichment in the lacustrine basins of the Alp‐orogenic belt.

Organic Carbon Reaction Kinetics in Bioturbated Sediments

AbstractMost organic carbon delivered to the seafloor is degraded within the bioturbated layer. Theory and empirical evidence have shown that organic carbon reactivity relates to the age of a particle. However, due to particle mixing, the age‐depth linear relation induced by sediment accretion is obfuscated. Here we combine a Lagrangian particle tracking model that resolves the age distribution of particles in the bioturbated zone and couple it to age‐dependent organic carbon degradation. Depth profiles for organic carbon concentration, reactivity and degradation rate are presented for sediments receiving low and high reactivity organic carbon in coastal, continental slope and deep‐sea environments. Our results show that a simple first‐order kinetics model suffices for well‐mixed sediments and systems receiving pre‐processed materials. A reactive continuum approach is needed for poorly mixed sediments receiving highly reactive organic carbon and for sediments below the bioturbated layer.

The impact of pore heterogeneity on pore connectivity and the controlling factors utilizing spontaneous imbibition combined with multifractal dimensions: Insight from the Longmaxi Formation in Northern Guizhou

The heterogeneity of shale pores, a crucial factor in the occurrence and migration of shale gas, exerts a significant impact on the pore connectivity. Pores exhibiting a range of structural attributes to the complexity of pore connectivity. A comprehensive study into the impact of pore heterogeneity on pore connectivity in shale is lacking. This study aims to explore the impact of pore heterogeneity on pore connectivity in shale and the primary controlling factors of pore connectivity. Shale pore connectivity, pore structures, mineral composition, and geochemical parameters were assessed using various tests, including spontaneous imbibition, adsorption, mercury intrusion capillary pressure (MICP), focus ion beam-scanning electron microscopy (FIB-SEM), sulfur and carbon analysis, vitrinite reflectivity, and X-ray diffraction (XRD). Pore heterogeneity was quantitatively analyzed using the multifractal dimensions method. Results show that the increased heterogeneity of pore structure and surface roughness facilitating the potential for increased connectivity. The presence of well-developed micro-mesopores within the organic matter, alongside numerous disconnected and independent pores, contributes to an increase in pore heterogeneity. Micro-mesopore structures have a more pronounced impact on pore heterogeneity than macropores. The heterogeneity of the pores is predominantly influenced by variations in the PV and SSA of micro-mesopores. Furthermore, the heightened heterogeneity of pore structure (D1) and surface roughness (D2) leads to a more complex pore structure with increased roughness, promoting the potential for enhanced connectivity through additional throats and facilitating the formation of secondary microfractures. Shale cores characterized by high total organic carbon (TOC) content, porosity, and clay mineral content are conducive to improved pore connectivity. Conversely, the increase of thermal evolution maturity of shale in the over-mature stage is not conducive to the increase of pore connectivity. Thermal evolution maturity, TOC content, and clay mineral are key factors that control pore heterogeneity, further affecting the connectivity of shale pores. High pore connectivity is conducive to spontaneous imbibition capacity and the formation of hydraulic microfractures, promoting the migration of shale gas.

Soil properties of overburden and topsoil in limestone mining area: A preliminary study

Limestone mining removes topsoil and produces overburden piles, which is improper for plant growth. The objectives of this study were to compare the texture, certain chemical properties, and bacterial population of overburden to the topsoil and to observe the effects of compost amendment on the growth of corn seedlings on the potted overburden. The overburden characterization was performed using a quantitative descriptive method with purposive sampling. Samples were taken from a 6-month-old overburden pile and a pine-vegetable agroforestry ecosystem. The data were further analyzed by using the Student’s t-test. A bioassay was set up in a randomized block design with various concentration compost treatments and five replications. The results showed significant differences between texture, chemical characteristics, and bacterial counts of overburden and topsoil were recorded. The topsoil was more acidic and had higher organic carbon, potential phosphorus, potential potassium, and cation exchange capacity, while the overburden had higher levels of calcium; however, the total N and Magnesium content in topsoil and overburden was similar. The bacterial population of the overburden was lower than in the topsoil. A total of 16 gram-negative and one gram-positive bacteria have been identified from both samples. Applying huge amounts of compost enhanced corn seedlings' growth in the overburden. The study suggested that overburden was more unfertile compared to the topsoil. Therefore, the improvement of overburden properties by compost amendment is needed to green the area.