Search Results (34)

The delayed decomposition of rice straw in Northeast China’s cold regions (winter temperatures < −20 °C) due to insufficient accumulated temperature requires innovative solutions. This study developed a synergistic approach combining microbial decomposition with mechanical burial. Pre-experiments identified optimal parameters for the liquid decomposing agent (100 mg/mL concentration, 6 g/m application rate). A novel combined machine was engineered with adjustable parameters: knife roller speed (200–300 r/min), burial depth (15–25 cm), and ground clearance (80–120 mm). Field trials demonstrated a 91.3% straw return rate under optimized settings (220 r/min, 100 mm clearance, 1.7 m/s speed), representing a 28.5% improvement over conventional methods. Spring burial enhanced straw decomposition to 83.6% within 60 days (vs. 67.2% in autumn), significantly increasing soil organic matter and available nitrogen. The integrated technology achieved 1.5 hm²/h operational efficiency, meeting regional agronomic demands. This study provides a replicable model for cold-region straw utilization, aligning with carbon sequestration goals in black soil conservation. Full article

Terrestrial Storage of Biomass (TSB) is a Negative Emission Technology for removing CO₂ already in the atmosphere. TSB is compared to other NETs and is shown to be a natural, carbon-efficient, and low-cost option. Nature performs the work of removal by growing biomass via photosynthesis. The key to permanent sequestration is to bury the biomass in pits designed to minimize the decomposition. The chemistry of biomass formation and decomposition is reviewed to provide best practices for the TSB burial pit design. Methane formation from even a small amount of decomposition has been raised as a concern. This concern is shown to be unfounded due to a great difference in time constants for methane formation and its removal from the air by ozone oxidation. Methane has a short lifetime in air of only about 12 years. Woody biomass decomposition undergoes exponential decay spread over hundreds to thousands of years. It is inherently slow due to the cross-linking and dense packing of cellulose, which means that the attack can only occur at the surface. A model that couples the slow and exponential decay of the rate of methane formation with the fast removal by oxidation shows that methane will peak at a very small fraction of the buried biomass carbon within about 10 years and then rapidly decline towards zero. The implication is that no additional equipment needs to be added to TSB to collect and burn the methane. Certified carbon credits are listed on various exchanges. The US DOE has recently issued grants for TSB development. Full article

The carbonate fracture-cave reservoir in the Tahe oilfield, China, encounters development challenges because of its substantial burial depth (exceeding 5000 m). Its characteristics are low permeability, pronounced heterogeneity, extensive karst cavern systems, diverse connection configurations, and intricate spatial distribution. Prolonged conventional water flooding leads to predominant water channels, resulting in water channeling and limited sweep efficiency. Surfactant flooding is usually adopted in these conditions because it can mitigate water channeling and enhance sweep efficiency by lowering the interfacial tension (it refers to the force that is generated due to the unbalanced molecular attraction on the liquid surface layer and causes the liquid surface to contract) between oil and water. Nonetheless, the Tahe oilfield is a carbonate reservoir where surfactant is prone to loss near the well, thereby limiting its application. High-pressure injection flooding technology is an innovative method that utilizes injection pressure higher than the formation rupture pressure to alter reservoir permeability, specifically in low-permeability oil fields. Because of the high fluid flow rate, the contact time with the interface is decreased, enabling the ability for surfactants to reach the deep reservoir. In this article, based on the mixed adsorption mechanism of two surfactants and the hydrophilic and lipophilic equilibrium mechanisms, a set of high-temperature and high-salinity resistance surfactant systems appropriate for the Tahe oilfield is developed and its associated performance is evaluated. An oil displacement experiment is carried out to examine the effect of surfactant flooding by high-pressure injection. The results demonstrate that the ideal surfactant system can lower the interfacial tension to 10⁻² mN/m and its capacity to reduce the interfacial tension to 10⁻² mN/m after different aging periods. Besides, the surfactant system possesses excellent wettability (wetting angle changed from 135° to 42°) and certain emulsifying abilities. The oil displacement experiment shows that the oil recovery rate of surfactant flooding by high pressure reaches 26%. The effect of surfactant flooding by high-pressure injection is better than that of high-pressure injection flooding. Full article

The light oil wells within the Neogene Shawan Formation have been extensively drilled in the Chepaizi Uplift, reflecting an increase that provides new targets for unconventional resources in the Junggar Basin of northwestern China. However, the original sources of light oil remain controversial, as several source rocks could potentially generate the oil. For this study, we collected light oils and sandstone cores for biomarker detection using gas chromatography–mass spectrometry (GC-MS). Additionally, fluid inclusions were observed and described, and the homogenization temperatures of saltwater inclusions were measured to confirm the oil charging history in conjunction with well burial and thermal history analysis. Based on these geochemical characteristics and carbon isotopic analysis, the results indicate that light oil in the Chepaizi Uplift zone primarily originates from Jurassic hydrocarbon source rocks in the Sikeshu depression, with some contribution from Cretaceous hydrocarbon source rocks. Jurassic hydrocarbon source rocks reached a peak of hydrocarbon generation in the middle to late Neogene. The resulting crude oil predominantly migrated along unconformities or faults to accumulate at the bottom of the Cretaceous or Tertiary Shawan Formation, forming anticlinal or lithologic oil reservoirs. Some oil reservoirs contain mixtures of Cretaceous immature crude oil. During the Neogene light oil accumulation process, the burial rate of reservoirs was high, and the efficiency of charging and hydrocarbon supply was relatively high as well. Minimal loss occurred during the migration of light oil, which significantly contributed to its rapid accumulation. Full article

Carbonate formation is the key reservoir in Sichuan Basin for natural gas development. Compared with the early stage of development, the burial depth of targeted formation becomes deeper, and the formation temperature gets higher. So, the characteristics of acidizing effectiveness in high-temperature carbonate formations make this evaluation slightly difficult. Currently, it is common that a single parameter is considered to study acidizing effectiveness by simulation and experiment methods. In this paper, for a more accurate investigation of acidizing effectiveness, multiple parameters, including permeability change rate, fracture conductivity, and surface roughness, were introduced by a series of experiments. It is revealed that the permeability change rate is more than 57% when using gelled acid. As the amount of diverting agent increases in diverting acid, the viscosity of the acid grows to its peak with the reaction, making it easier to block the high permeability core temporarily and divert to acidify the low permeability core, where the permeability change rate of the low permeability core goes from 51.6% to 64.2%, which shows well acidizing effectiveness. In addition, the short-term and long-term conductivity of the samples from the three different formations are more than 200 mD∙m under high closure stress. The conductivity of Maokou Formation is the largest due to its high content of carbonate minerals and high dissolution rate. And the results of long-term conductivity are consistent with those of surface roughness, making the evaluation results more reliable for acidizing effectiveness. It is worth noting that temperature is a factor that cannot be ignored in the evaluation of acidizing effectiveness because it has a great influence on the performance of the acid system, such as viscosity and the reaction-reduced rate, leading to an acidizing effectiveness affect. So, the temperature resistance of an acid system is important as well. Full article

This study employed 1D numerical pseudo models to examine the Upper Jurassic carbonate succession, focusing on the Mikulov Formation in the Vienna Basin region. It addresses the protracted and complex history of the Jurassic source rock play, revealing a transition from rapid syn-rift (>200 m/Ma) to slower post-rift sedimentation/subsidence of the overlying layers during extensional deformation (up to 120 m/Ma with a thickness of 1300 m). This provides valuable insights into the rift-to-drift stage of the central Alpine Tethys margin. The Mikulov marls exhibit characteristics of a post-rift passive margin with slow sedimentation rates. However, a crustal stretching analysis using syn-rift heat flow sensitivity suggested that thermal extension of the basement alone cannot fully explain the mid-Jurassic syn-rift stage in this segment of the Alpine Tethys. The sensitivity analysis showed that the mid-late Jurassic differential syn-rift sequences were exposed to slightly cooler temperatures than the crustal stretching model predicted. Heat flow values below 120 mW/m² aligned with measurements from deeply settled Mesozoic successions, suggesting cold but short gravity-driven subsidence. This may account for the relatively low thermal maturation of the primary source rock interval identified by the time-chart analysis, despite the complex tectonic history and considerable sedimentary burial. The post-Mesozoic changes in the compaction trend are possibly linked to the compressional thrusting of the Alpine foreland and postdating listric faulting across the Vienna Basin. Full article

This study evaluates the efficacy of buried straw bioreactor (SBR) technology in enhancing soil properties, CO₂ efflux, and crop yield, specifically focusing on Indian cowpea cultivation within a greenhouse environment. Conducted at the Yuxi Demonstration Park in Fujian, China, the experiment utilized a randomized block design incorporating seven treatments with varying straw application rates (4.5, 6, and 7.5 kg m⁻²) and burial depths (20 and 30 cm) alongside a control group. The investigation revealed that SBR technology significantly increased soil temperature, CO₂ efflux, soil total nitrogen (TN), and total organic carbon (TOC), contributing to a marked improvement in the biomass of Indian cowpea roots, stems, and leaves. Notably, the optimal results were observed with 7.5 kg m⁻² straw applied at a 20 cm depth, enhancing soil temperature by 1.5–2.0 °C and multiplying cowpea biomass by 2.1–6.4 times relative to the control. This treatment also led to the highest increases in soil TOC and CO₂ efflux, demonstrating the potential of SBR technology for carbon sequestration and suggesting its application as a sustainable agricultural practice in cold regions to ameliorate the soil’s physical and nutritional characteristics, thus supporting enhanced crop production. The study underscores SBR technology’s role in addressing the challenge of agricultural waste through the effective reuse of crop straw, promoting the circular development of agriculture while safeguarding the ecological environment. Full article

Although mangrove forests occupy only 0.5% of the global coastal area, they account for 10–15% of coastal organic carbon (OC) storage, and 49–98% of OC is stored in sediments. The biogeochemistry of iron minerals and OC in marine sediments is closely related. To better reveal the role of iron minerals in OC preservation in mangrove sediments, an established dithionite–citrate–bicarbonate (DCB) extraction method was used to extract iron-bound OC (Fe-OC), and then the parameters of OC, Fe-OC, iron content, carbon isotopes, infrared spectroscopy, and XRD diffractions of sediments at a 1 m depth in four typical mangrove communities in the Gaoqiao Mangrove Reserve, Guangdong, China, were systematically measured. XRD diffractograms showed that the iron minerals in mangrove sediments may mainly exist in the form of goethite, which is consistent with the predominant types of iron minerals in marine sediments. About 10% of OC is directly bound to iron, and it is further estimated that about 2.4 × 10¹²–3.8 × 10¹² g OC is preserved in global mangrove forests each year based on the high burial rate of OC in mangrove sediments. Lower Fe-OC/OC molar ratios indicated that iron mainly binds to OC via adsorption mechanisms. More depleted δ¹³C_Fe-OC relative to δ13C_bulk indicated that iron minerals are mainly associated with terrigenous OM, and the infrared spectra also revealed that iron minerals preferentially bind to terrigenous aromatic carbon. This work supports the “giant rusty sponge” view, elucidating that iron plays an important role in the preservation of OC in mangrove sediments. Full article

In order to investigate the effect of primary productivity, organic matter dilution, and preservation on the accumulation of organic matter, geochemical data, and proxies of primary productivity, clastic influx, and redox conditions were obtained for organic-rich shales in the Cambrian Niutitang Formation. The primary productivity (total organic carbon [TOC], Mo, P, Ba, and Babio) and redox (Ni/Co, V/Cr, U/Al, and Th/U) proxies suggest the organic-rich shales were deposited in anoxic-euxinic conditions during periods of high primary productivity. Pyrite in the Niutitang Formation comprises spherical framboids, which also indicate that anoxic bottom waters were present during organic matter deposition. High primary productivity enhanced the organic C flux into the thermocline layer and bottom waters, which lead to the development of anoxic bottom waters owing to O₂ consumption by microorganisms and organic matter degradation. The anoxic bottom waters were beneficial for the preservation of organic matter. In addition, Ti/Al ratios correlate well with TOC contents throughout the Niutitang Formation, indicating that clastic input increased the burial rate and prevented organic matter degradation during deposition. Therefore, the accumulation of organic matter in the Niutitang Formation was controlled mainly by primary productivity rather than bottom-water redox conditions. Full article

Carbon export from mangrove forests to the oceans partly acts as a sink for atmospheric CO₂, exceeding the rate of carbon burial in mangrove soils. Primary production in ecosystems adjacent to mangroves may prevent degassing and enhance further carbon export from mangroves to the oceans. In this study, we continuously monitored carbonate chemistry parameters (pCO₂, dissolved inorganic carbon (DIC), total alkalinity (TA)) and dissolved organic carbon (DOC) in a tidal flat adjacent to a fringe mangrove forest over a spring-neap tidal cycle. Mean pCO₂ during the entire period was 923 ± 318 μatm, and the export of TA, DIC, and DOC from the mangroves to the ocean was 36 ± 26 mmol m⁻² d⁻¹, 42 ± 39 mmol m⁻² d⁻¹, and 10 ± 9 mmol m⁻² d⁻¹, respectively. Semi-monthly pCO₂ variations in the mangrove front were controlled by the tidal level during spring tide and by photosynthesis and respiration on the tidal flat during neap tide. This means that during neap tide, photosynthesis on the tidal flat offset the increase in pCO₂ caused by the porewater export from the mangrove soil. The DIC/TA export ratio in this study was 1.17 ± 0.08, which was lower than the global average of 1.41 ± 1.39, indicating that the tidal flat adjacent to the mangrove forest may act as a buffer zone to mitigate the increase in pCO₂, resulting in much of the exported DIC being stored in the ocean. Full article

The Total Organic Carbon (TOC) content plays a crucial role in gas hydrate exploration because a higher TOC content signifies a greater potential for buried gas hydrates. The regulatory mechanisms governing organic matter in sediment are intricate and influenced by various predominant factors unique to different regions. Notably, the Shenhu area in the South China Sea stands as a pioneering region for methane hydrate research. Despite its significance, limited research has focused on the burial patterns of TOC, resulting in an insufficient dataset to draw definitive conclusions. Consequently, a comprehensive understanding of the burial patterns and controlling factors of TOC within this area remains elusive. This study examines the pore-water characteristics, mineral composition, geochemistry, and sedimentary factors of four distinct sites within the Shenhu region of the South China Sea. The current depths of the Sulfate-Methane Interface (SMI) for sites CL54, CL56, CL57, and CL60 are identified as 28.6, 8.5, 31.9, and 8.1 m below the seafloor (mbsf), respectively. It’s noteworthy that these SMI depths align with locations known to harbor underlying gas hydrates. Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) analyses reveal that the primary sediment sources within this region encompass microbial shells (such as foraminifera and diatoms), clay, and terrestrial detritus. In addition, marine productivity exhibits a reverse correlation with TOC content, and both TOC content and Ce/Ce* ratios exhibit synchronous fluctuations with sedimentation rate. Drawing from the sedimentation rate, TOC content, as well as indicators of redox conditions (Mo_EF, Ce/Ce*, Mo/U) and productivity proxies (Ba/Al, P/Al) within the sampled sites, it becomes apparent that high sedimentation rate coupled with ‘anaerobic’ conditions foster favorable conditions for TOC accumulation. This comprehensive investigation not only provides valuable datasets but also offers insights into the intricate processes governing TOC accumulation. Full article

The mechanism of the influence of soil water repellency (SWR) and agglomeration stability on soil organic carbon (SOC) mineralization has not been thoroughly studied following different methods of returning straw to the field. The research background in this study was ordinary black soil, and the addition of straw was accomplished via straw mixing (CT), straw mulching (CM), straw deep burying (CD), and straw tripling deep burial (CE). A 120-day long-term incubation test was used to measure the contact angle between water droplets and soil, the particle size distribution of aggregates and their organic carbon (OC) content, organic carbon pool (OCP) content, OC contribution, and soil CO₂-C release, the extent of SWR and the direct effect of agglomerates on SOC mineralization were assessed under different straw return methods. The results revealed that the water-droplet–soil contact angle (CA) was much greater and the rate of CA decline was significantly lower in the CD treatment compared to the CT, CM, and CE treatments, the rate of water droplet penetration on the soil surface was slower, and the SWR was improved. The CD treatment significantly increased the content of macroaggregates and their OCP content, and also significantly increased the content of microaggregates’ OC. The CO₂-C emission rate and cumulative emissions were enhanced by adding the same amount of straw, with the most significant enhancement in the deep straw treatment. The cumulative CO₂-C emission rate and SOC mineralization significantly increased with increases in SWR, macroaggregates content, and microaggregates OC content, but significantly decreased with increases in macroaggregates’ OC content, according to principal component analysis and Pearson’s correlation analysis. These results highlight the extent of SWR and the direct effect of agglomerate particle size distribution and OC content on SOC mineralization under different straw return methods. This will help to consolidate soil structural stability and nutrient management to support productivity and SOC sequestration in different agricultural systems. Full article

Four short sediment cores were collected to explore the impacts of bay scallop farming on the composition and accumulation of sedimentary organic matter (SOM). The results revealed that SOM was mainly composed of relatively easily biodegradable substances as evidenced by the high contribution rate of biopolymeric carbon (77.8–94.4%). The sediment accumulation rate in the scallop farming area (SFA) was 28.6% higher than that in the non-scallop farming area (NSFA). The total organic carbon (TOC) and total nitrogen (TN) burial fluxes in the SFA were 33.1 and 36.6% higher than those in the NSFA, respectively. A rough estimate showed that the burial fluxes of TOC, TN, scallop-derived OC, and marine algal-derived OC in the ~150 km² SFA could increase by 1.08, 0.11, 0.39, and 0.68 g m⁻² yr⁻¹, respectively, with annual scallop production increasing 10⁴ t. This study highlights the significant effects of scallop farming on the biogeochemistry of SOM in coastal waters, which provides a direct reference for future research on the carbon cycle in shellfish culture areas. Full article

Carbon burial in lake sediments has a profound impact on the global carbon cycle. In this study, the burial characteristics of organic carbon (OC) in typical sediments from the Poyang basin over the past hundred years were investigated and the influencing factors and driving mechanism were determined. The results showed that carbon burial in the Poyang basin sediments was mainly driven by human activities, whereas the change in the OC accumulation rate was related to precipitation, forest land area, water area, construction land area, urbanization rate, application of agricultural fertilizers, per capita GDP and population. Full article

As one of the main interfaces of the Earth system, estuaries show the strongest land–sea interaction in the carbon cycle, which links terrestrial ecosystems to the marginal sea. Furthermore, estuaries are considered as one of the most active intermediate reservoirs for both terrestrial and marine matter due to complex hydrodynamic processes regulated by the river runoff, wave and tide. Processing of organic matter (OM) in tidal estuaries modifies its transfer and transformation from the river to the sea, so studies of on the source and distributions of estuarine OM can help us understand the behavior of production, exchange, transport and burial of diverse OM within this transition zone before entering the marginal sea. In this paper, we took the Minjiang River Estuary (MRE) as a typical system in which there is strong influence of the tide. The source, composition and spatial distribution of OM in surface sediments of MRE were deciphered based on multiple organic geochemical properties for source-specific biomarkers (n-alkanes, n-alkanols, sterols) and bulk OM. Results show that sedimentary organic components were negatively correlated with sediment grain size, which indicates fine particles such as silt and clay are the major carriers of the OM signals in tidal estuaries. Source-specific biomarker proxies indicate that in terms of source diversity the sedimentary OM in the MRE shows mixed signals of terrestrial and marine sources, and the proportion of terrestrial OM decreases with the increase in distance from the land. The fractional contributions of OM from the riverine (i.e., terrestrial), marine and deltaic sources were quantitatively estimated using a Monte Carlo (MC) three-end-member mixing model based on C/N and δ¹³C values, and the average contributions of the three sources are 40 ± 10%, 48 ± 10% and 12 ± 4%, respectively, with little contribution from deltaic sources. The dispersion of sedimentary OM from different sources in the MRE is primarily controlled by the depositional environment determined by dynamic conditions and tidal processes play a significant role in the redistribution of sedimentary OM dispersion patterns. Compared with other large estuaries in southeast China, the OM accumulation contribution in the tide dominated small and medium-sized estuaries such as the MRE which is largely dependent on riverine and marine deliveries. The MRE has a high potential for both terrestrial and marine organic carbon (OC) burial, with an accumulation rate of 3.39 ± 1.83 mg cm⁻² yr⁻¹ for terrestrial OC, and an accumulation rate of 3.18 ± 0.68 mg cm⁻² yr⁻¹ for marine OC in muddy sediment, making it an important contributor to the sedimentary carbon sink of the marginal sea. Full article