Variations In Carbon Content Research Articles

Comparison of Determination Methods Total Organic Carbon in The Soil

Objective: This research aimed to compare two methods for determining soil organic carbon, in two soils with different textures. Method: Soil samples were collected in three locations (Dourados-MS, Chapadão do Sul-MS and Cassilândia-MS), with different textures (clayey and sandy), at a depth of 0-20 cm, to determine organic carbon . The results were subjected to statistical analysis, using the SAS version 6 software and the means were compared using the t test (p < 0.05). In the correlation study, linear regression analyzes were performed. Result and conclusion: There was variation in the soil organic carbon content (SOC) between the methods studied for both soils. Measuring soil samples by volume (spectrophotometer) modifies the results, regardless of the soil texture. There is greater variation between the data obtained in soils with a higher COS content than in soils where the COS content is lower. Furthermore, the results indicate the need for new studies in which soils from agricultural areas and under native vegetation are selected by soil classes, textures and types of land use. Research implications: Research related to comparison studies of SOC determination methods is of paramount importance, as there is a lack of information regarding the definition and recommendation of the most appropriate method. Originality/value: With this study it is possible to disseminate to the scientific community methods for determining SOC that make it possible at the same time to reduce the use of chemical reagents, without this negatively interfering with the quality of soil organic carbon determination.

Comparison of Determination Methods Total Organic Carbon in The Soil

Objective: This research aimed to compare two methods for determining soil organic carbon, in two soils with different textures. Method: Soil samples were collected in three locations (Dourados-MS, Chapadão do Sul-MS and Cassilândia-MS), with different textures (clayey and sandy), at a depth of 0-20 cm, to determine organic carbon . The results were subjected to statistical analysis, using the SAS version 6 software and the means were compared using the t test (p < 0.05). In the correlation study, linear regression analyzes were performed. Result and conclusion: There was variation in the soil organic carbon content (SOC) between the methods studied for both soils. Measuring soil samples by volume (spectrophotometer) modifies the results, regardless of the soil texture. There is greater variation between the data obtained in soils with a higher COS content than in soils where the COS content is lower. Furthermore, the results indicate the need for new studies in which soils from agricultural areas and under native vegetation are selected by soil classes, textures and types of land use. Research implications: Research related to comparison studies of SOC determination methods is of paramount importance, as there is a lack of information regarding the definition and recommendation of the most appropriate method. Originality/value: With this study it is possible to disseminate to the scientific community methods for determining SOC that make it possible at the same time to reduce the use of chemical reagents, without this negatively interfering with the quality of soil organic carbon determination.

Lightweight, freestanding hybrids of graphene and hexagonal boron nitride foams

Lightweight boron carbon nitride foams which are a hybrid of graphene and hexagonal boron nitride (hBN), are produced using the nickel template method and remain freestanding after the etching of nickel without the stabilization of a polymer during etching. Chemical vapor deposition (CVD) precursors with varying carbon content were utilized, but only a 10% range of carbon atomic percentage variation is observed in the resulting boron carbon nitride foams due to the high carbon solubility of nickel. However, the cooling rate during the CVD process has a much more significant effect on the carbon content. Moreover, a 6.5-fold increase in resistivity is observed for our foams compared to a graphene foam with an overall trend of decreasing resistance with increasing carbon content. Furthermore, when the foam is infiltrated with epoxy to form a composite at 0.3% volumetric percentage concentration, there is a 27% increase in the thermal conductivity over hBN foam composites. These foams are suitable to use as a substitute for graphene foams when a lower electrical conductivity is desired and could potentially be used as a thermal interface material if a higher pore density nickel template is utilized.

Effect of fixed carbon on the interfacial compatibility of coal gangue/polyethylene composites was investigated using anthracite as a model compound

AbstractCoal gangue (CG), a byproduct of coal mining, integrated with polyethylene (PE) offers potential in diverse applications. However, ensuring compatibility between CG and PE remains a challenge due to CG's complex nature. This study explores the influence of fixed carbon, represented by high‐carbon‐content anthracite, on the interface of CG/PE composites. Comprehensive investigations were conducted on physical, mechanical, thermal, microstructural, and chemical aspects. Results revealed that increasing carbon content positively impacted density and hardness while enhancing bending strength and modulus, albeit at a cost of reduced tensile strength. When the C content reached 80%, the hardness and density increased from 50.5 HD and 0.93 g cm−3 to 62.4 HD and 1.18 g cm−3, which were 23.6% and 26.9% higher, respectively. Meanwhile, the bending strength and bending modulus reached 17.2 and 1582.4 MPa, which were 53.6% and 239.1% higher than those of the composites prepared from pure PE (11.2 and 466.7 MPa), respectively. However, the tensile strength decreased by 48.7% from 11.7 to 6.0 MPa. Moderate carbon content positively affected thermal stability, yet higher concentrations posed stability challenges. Microstructural analyses unveiled varied interfacial morphologies, shedding light on carbon's role in enhancing material rigidity and hardness. Surface chemical studies suggested physical entanglement between carbon and PE. Additionally, varying carbon content influenced crystallization, elevating crystallinity and impacting mechanical properties. The findings underscore carbon's potential in reinforcing composite materials. This research provides insights into optimizing CG/PE composites and addressing CG treatment challenges.Highlights Unveiled relationships between fixed carbon and properties in composites. The structure was studied qualitatively and quantitatively by XRD. The anthracite‐C substitution in composite preparation was unraveled.

Systematic Study on the Microstructures of Biomedical Co–20Cr–15W–10Ni Alloys with Carbon Contents Ranging from 0 to 0.2 mass pct

Herein, the effect of carbon content on the microstructures of Co–20Cr–15W–10Ni (mass pct, CCWN) alloys was systematically studied. For this, CCWN alloys with carbon contents of 0, 0.05, 0.10, and 0.20 mass pct, i.e., 0C, 0.05C, 0.10C, and 0.20C alloys, respectively, were prepared using an induction melting furnace. The as-cast alloys were solution treated at 1523 K for 7.2 ks, followed by cold swaging and heat treatment at 1173 K–1473 K for 0.15–7.2 ks. Consequently, η-phase (M6C-M12C type, M: metallic element) precipitates were detected in the as-cast 0.10C and 0.20C alloys, whereas no precipitates were observed in the 0C and 0.05C alloys. These precipitates were dissolved via a solution treatment. After cold swaging, the ε-phase formed through a strain-induced martensitic transformation in the 0C and 0.05C alloys. Following heat treatment, a single γ-phase matrix was observed in all the alloys, and μ-phase (Co7W6-type) and η-phase precipitates were observed in the 0C and carbon-added alloys, respectively. The precipitation temperature range of the η-phase increased with increasing carbon content. The stability of the precipitates qualitatively conformed with that of the calculated phase diagram. This is the first paper that reports the microstructural changes in CCWN alloys with varying carbon contents.

Soil Aggregate Stability and Organic Carbon Content among Different Forest Types in Temperate Ecosystems in Northeastern China

Soil aggregates play a crucial role in substance and energy cycles in soil systems. The fixation of soil organic carbon (SOC) is closely tied to the safeguarding mechanisms of soil aggregates. Carbon fixation involves the conversion of atmospheric carbon dioxide into organic molecules by autotrophic organisms. Soil aggregates play a significant role in carbon stabilization, allowing for the physical occlusion of SOC. This study focuses on five forest types, Betula platyphylla, Betula dahurica, Quercus mongolica, Larix gmelinii, and mixed forests comprised of Larix gmelinii and Quercus mongolica, in the Heilongjiang Central Station Black-billed Capercaillie National Nature Reserve, northeast of China. This study investigated the soil aggregate stability (SAS) (water sieving) and aggregate-associated organic carbon (AAOC) at different soil depths in five forest types. Our findings demonstrated that fine macro-aggregates (0.25–2 mm) were the main types of soil aggregates among all the forest types. The SAS gradually decreased with increasing soil depth. Notably, broad-leaved forests exhibited relatively high soil stability. The fine macro-aggregates (0.25–2 mm) had the highest AAOC content, and the AAOC level was highest in the topsoil layer. The SAS and AOCC levels of the Betula platyphylla forest and Betula dahurica forest were higher than those of other forest types and were significantly affected by the forest type, soil depth, and soil physicochemical properties. Collectively, our findings reveal the key factors influencing aggregate stability and the variations in soil organic carbon content in different forest types. These observations provide a basis for studying the mechanisms of soil aggregate carbon sequestration, as well as for the sustainable development of forest soil carbon sequestration and emission reduction.

Thermal Equations of State of Magnesite: Implication for the Complex Mid‐Lower Mantle Seismic Scatterers

AbstractMagnesite (MgCO3) entering the lower mantle together with the subducted oceanic crust is an important carbon carrier. The reaction between magnesite and mantle minerals has been documented, but its influence on the density and velocity profiles of lower mantle remains unexplored. To decipher the deep carbon transportation and its associated effect, here we determined the thermal equations of state of magnesite up to 120 GPa and 2600 K using X‐ray diffraction in laser‐heated diamond anvil cells. The obtained thermal elastic parameters of magnesite facilitated a comprehensive understanding on the influence of magnesite‐SiO2 reaction, variation of carbon and SiO2 content, and temperature on the origin of lower‐mantle scatterers at 1,000–1,800 km depth. Our modeling revealed that the depth of the lower‐mantle VS scatterers is mainly controlled by the Al2O3 content in SiO2, while its magnitude depends on the SiO2 content. Along normal geotherm, the magnesite‐SiO2 reaction would occur before the post‐stishovite transition, consuming substantial SiO2 in the subducted oceanic crust. Depending on the amount of residual SiO2, the post‐stishovite transition can produce a 2.5–5.2 (2)% VS reduction, compatible with the observed seismic scatterers in Izu‐Bonin and Mariana subduction zones. Along slab geotherm, this reaction occurs after the post‐stishovite transition, generating a greater VS reduction of 4.4–6.4 (4)%. We thus propose that the reaction between sinking MgCO3 and SiO2 in the slab is one of the potential factors influencing the magnitude of the lower‐Vs scatterers at 1,000–1,900 km depth. Our results provide new insights into the deep‐mantle carbonate transportation influencing regional geophysics.

Effect of C content on the microstructure and properties of in-situ synthesized TiC particles reinforced Ti composites

Titanium matrix composites (TMCs) have garnered substantial attention from researchers owing to their outstanding properties. Nonetheless, the strength and ductility of TMCs hardly co-exist and often show a trade-off between each other. In this study, we employ an ultra-thin graphite powder sheet as the carbon source and employ Ti/C composites with varying carbon contents, prepared via a layer-stacked laminated sintering method, to ensure a comprehensive in-situ reaction and uniform reinforcement distribution. With increasing carbon content, noticeable alterations occur in the size, concentration, and morphology of the titanium carbide (TiC) particles. The increase of TiC particle content is found to boost the ultimate tensile strength of the composite. However, this improvement comes at the expense of reduced elongation. Notably, as the carbon content reaches 1.81 wt%, the yield strength and ultimate tensile strength of the composites soar to 354.4 MPa and 575.4 MPa, respectively. These values represent a remarkable increase of 75.4% and 65.0% compared to pure titanium, while maintaining an acceptable elongation of 6.45%. This study unveils a promising approach for significantly enhancing the mechanical properties of titanium alloys.

Effect of carbon content on electronic structure of uranium carbides

The electronic structure of UC_x (x = 0.9, 1.0, 1.1, 2.0) was studied by means of x-ray absorption spectroscopy (XAS) at the C K edge and measurements in the high energy resolution fluorescence detection (HERFD) mode at the U M_4 and L_3 edges. The full-relativistic density functional theory calculations taking into account the 5f-5f Coulomb interaction U and spin-orbit coupling (DFT+U+SOC) were also performed for UC and UC_2. While the U L_3 HERFD-XAS spectra of the studied samples reveal little difference, the U M_4 HERFD-XAS spectra show certain sensitivity to the varying carbon content in uranium carbides. The observed gradual changes in the U M_4 HERFD spectra suggest an increase in the C 2p-U 5f charge transfer, which is supported by the orbital population analysis in the DFT+U+SOC calculations, indicating an increase in the U 5f occupancy in UC_2 as compared to that in UC. On the other hand, the density of states at the Fermi level were found to be significantly lower in UC_2, thus affecting the thermodynamic properties. Both the x-ray spectroscopic data (in particular, the C K XAS measurements) and results of the DFT+U+SOC calculations indicate the importance of taking into account U and SOC for the description of the electronic structure of actinide carbides.

Investigation of Uncertainty in Organic Carbon Stock Estimates on a Field Scale

The uncertainty sources in the assessment of organic carbon stocks were studied in a layer of 0–30 cm within the sampling site (100 × 100 m) set on soddy-podzolic cultivated soil (Albic Glossic Retisol (Aric, Loamic, Ochric)). In the experiment, two sampling methods were used – the classic sampling in pits, by 10-cm layers, and sampling with an auger to a depth of 0–30 cm. The soil bulk density was determined by the Kachinsky method and the carbon content was analyzed by the Tyurin method. Some samples were additionally analyzed at the Bryansk State Agrarian University. The uncertainties associated with natural variation, sample preparation and the analytical process proper were estimated. The analytical uncertainty of bulk density measurement did not depend on the sampling depth under the experimental conditions and amounted to about 6%. The analytical error of Tyurin’s method did not differ in two laboratories. Its contribution reached 5–9% of the total variation in soil organic carbon content at the test plot. The uncertainty of sample preparation ranged from 11 to 26%, natural variation—from 49 to 68% to the total variance, respectively. Determination of carbon content in the samples taken with an auger from the depth of 0–30 cm is preferable than layer-by-layer sampling as the number of intermediate operations is fewer, and the obtained results are comparable.

An Investigation of the Organic Carbon Stocks Estimates Uncertainty on a Fields Scale

A study of the uncertainty sources in the assessment of organic carbon stocks in a layer of 0–30 cm at the scale of the sampling area (100 × 100 m) laid on soddy-podzolic cultivated soil (Albic Glossic Retisol (Aric, Loamic, Ochric)) was carried out. In the experiment, two sampling methods were used – the classic 10-cm layers from profiles and with an auger to the depth of 0–30 cm. The soil bulk density was determined by the Kachinsky method, the carbon content was determined by the Tyurin method. Some of the samples were additionally analyzed at the Bryansk State Agrarian University. The uncertainties associated with natural variation, sample preparation and the proper analytical process are estimated. The analytical uncertainty of the bulk density under the conditions of the experiment did not depend on the sampling depth and amounted to about 6%. The analytical uncertainty of Tyurin’s method did not differ in two laboratories. Its contribution was 5–9% of the total variation of the soil organic carbon content in the area. The uncertainty of sample preparation determined from 11 to 26%, natural variation – from 49 to 68% of the total variance, respectively. Determination of the carbon content in the samples taken by the auger, when the sample is taken immediately at 0–30 cm, wins in reducing intermediate operations and gives comparable results compared to layer-by-layer sampling. The uncertainty of sample preparation determined from 11 to 26%, natural variation – from 49 to 68% of the total variance, respectively. Determination of carbon content in samples taken by auger, when the sample is taken immediately at 0–30 cm, wins in reducing intermediate operations and gives comparable results compared to layer-by-layer soil sampling.

Quantitative hardness‐carbon content‐microstructure correlation in normalized plain carbon steel

AbstractComposition (carbon content) dependent critical structural evolution in correlation to hardness attained is judiciously investigated for plain carbon steel, the most widely used cost‐effective structural material, under normalizing treatment of industrial relevance involving non‐equilibrium still air cooling. The solid state phase transformation under non‐equilibrium still air cooling is conceived in terms of a logarithmic variation of eutectoid carbon content with the gross carbon content of steel in view of maintaining fixed maximum solubility of carbon in α‐iron with an assumption of the prevailing para‐equilibrium condition. Such a unique formulation for non‐equilibrium condition together with consideration of Hall–Petch type relationship and rule of mixture for two prime microconstituents (proeutectoid α‐ferrite and pearlite) finally results in a new mathematical relationship for chemical composition‐structure‐property correlation for the non‐equilibrium normalizing treatment readily practiced in industry. Indeed, a composition dependent structural refinement effect is established that is exemplified with the rise in hardness level in plain carbon steel under conventional normalizing treatment. Most importantly, the experimentally measured overall hardness values closely follow those obtained by the developed mathematical relationship, thereby meeting an ever‐needed requirement of direct determination of steel hardness of practical relevance from microstructural parameters.

Carbon defect induced evolution of structural and mechanical properties in substoichiometric (HfMoNbZr)Cx films

Substoichiometric (HfMoNbZr)Cx films with varied carbon content were synthesized using non-reactive magnetron sputtering. Findings reveal that the (HfMoNbZr)Cx film predominantly exhibits a single-phase FCC structure, which transforms to a dual-phase structure consisting of FCC and Hex. phases at higher carbon content. This behavior arises from the segregation of group VB (Nb) and VIB (Mo) elements from the FCC lattice. The film hardness (H) and elastic modulus (E) increases with rising carbon content accompanied by a decrease of coefficient of friction (COF). However, the wear rate is not decreased despite the increased H and reduced COF of the as-deposited films. This phenomenon is explained by examining the differences in the wear mechanisms between (HfMoNbZr)Cx films with single- and dual- phase structures.

Sedimentary Environment Interpretation and Organic Matter Enrichment of the Lower Cambrian Shuijingtuo Shale in the Yichang Slope, South China: Insight from Sedimentary Geochemical Proxies with Major/Trace Elements

The vertical geochemical variations in total organic carbon (TOC) content and major and trace elements of the Lower Cambrian Shuijingtuo Formation from the Yichang Slope in the Upper Yangtze were investigated to assess the environmental conditions (redox conditions, water mass restriction, terrigenous input, relative sea-level terrestrial, and paleoproductivity) and to determine the primary controlling factors for organic matter enrichment. The Shuijingtuo Shale is divided into three intervals. The lithofacies of interval I are mainly black siliceous shale with high TOC content, and interval II is mainly black siliceous shale with moderate TOC content. Interval III consists of black, clay-rich siliceous shale and dark-gray calcareous shale and is characterized by a low TOC content. The effects of diagenesis and hydrothermal activity on the elements were evaluated prior to analyzing the environmental condition. There are good positive correlations between TOC and U/Al or Mo/Al ratios, suggesting that major/trace elements still retain the geochemical signature of the sedimentary environment. Meanwhile, the geochemical proxies consisting of Al, Fe, Mn, and Ti indicate that the study area did not experience hydrothermal deposits. The redox proxies (U/Th, Corg:Ptot, and MoEF–UEF) indicate that the interval I samples were formed under a strong reducing condition. The diagram of TOC vs. Mo indicates that the water mass was moderately restricted during the deposition of interval I shales. Proxies of terrigenous input and relative sea-level (Zr/Al and Zr/Rb) suggest that the organic-rich shales at the bottom were deposited under a relatively high sea-level and experienced minimal input of terrigenous debris from the source area. Additionally, the paleoproductivity indicated by Sibio and (Ni + Cu + Zn)/Al was high for interval I samples. During the interval II period, the relative sea-level began to decline, the seawater still remained in reducing conditions, and there was no change in the productivity, but the input of terrigenous debris increased significantly. In the interval III depositional period, the relative sea-level continued to decrease, the seawater shifted to a dysoxic condition, and the paleoproductivity was also at a lower level. The evolution of the sedimentary environment indicates that the high TOC content in the interval I samples is mainly attributed to the strong reducing condition, the preservation condition and debris dilution together control the organic matter content within the interval II samples, and the low TOC content within the interval III samples is constrained by a combination of the poor preservation conditions and lower paleoproductivity.

Enhanced Double Metal Cyanide Catalysts for Modulating the Rheological Properties of Poly(propylene carbonate) Polyols by Modifying Carbonate Contents.

Poly(propylene carbonate) (PPC) polyol is an environmentally sustainable material derived from abundant and renewable greenhouse gas, CO2. Optimizing their synthesis and properties is crucial to their application in the production of polyurethane products. In this study, we synthesized PPC polyols with varying carbonate contents using heterogeneous Zn/Co double metal cyanide (DMC) catalysts, which were prepared with poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123) as an effective complexing agent. Analysis of the influence of calcination temperature revealed that the DMC-P123 catalyst calcined at 100 °C exhibited superior catalytic performance owing to reduced crystallinity and enhanced formation of the monoclinic phase. Additionally, by precisely controlling the CO2 pressure, high propylene carbonate contents of up to 32.8 wt % in the polyol structure were achieved. The increased carbonate content enhanced the intermolecular attraction between polyol chains, thereby promoting hydrogen bonding and significantly modulating the rheological properties of the polyol. The novel findings of this study establish a solid foundation for the synthesis of CO2-based polyols with desirable properties, serving as alternatives to conventional petroleum-based polyols.

Characteristics and factors influencing soil organic carbon composition by vegetation type in spoil heaps.

The variation of organic carbon content in spoil heaps is closely related to improving soil structure, maintaining soil fertility, and regulating soil carbon cycling balance. Analyzing the soil organic carbon content and related driving factors during the natural vegetation restoration process of spoil heaps is of great significance for promoting the accumulation of soil organic carbon in the spoil heaps. we selected spoil heaps with the same number of years of restoration to research the variations in soil organic carbon components under different vegetation types (grassland: GL, shrubland: SL, secondary forest: SF) and compared the results with those on bare land (BL). Our results showed that vegetation type and soil depth significantly affect the content of soil organic carbon components. There was no difference in soil organic carbon components between SF and SL, but both were considerably superior to GL and BL (p<0.05), and the particulate organic carbon (POC) and light fraction organic carbon (LFOC) contents of SL were the highest. A significant positive linear correlation existed between SOC and active organic carbon components. Pearson's correlation and redundancy analysis showed that the available potassium (AK) and total nitrogen (TN) contents and gravel content (GC) in the BL soil significantly impacted soil organic carbon. When vegetation is present, TN, total phosphorus (TP), and Fine root biomass (FRB) significantly affect soil organic carbon. Structural equation modelling (SEM) shows that AK and soil moisture content (SMC) directly affect the organic carbon composition content of BL, When there is vegetation cover, fine root biomass (FRB) had the largest total effect in the SEM. Soil bulk density (BD) has a negative impact on soil organic carbon, especially in the presence of vegetation. These findings suggest that vegetation restoration can significantly increase soil organic carbon content, FRB, AK, and TN play important roles in enhancing soil organic carbon. Supplementation with nitrogen and potassium should be considered in the bare land stage, and shrubs nitrogen-fixing functions and well-developed roots are more beneficial for the accumulation of soil organic carbon.

E-SCAN: Electrochemical Scanning of Carbonates, an In Situ Approach for Screening and Quantifying Inorganic Carbon in Soil.

A modified three-electrode system was utilized with a correlated ion-capture film that is functional to changes in soil carbonate moieties to determine an understudied pool of soil carbon that is vital toward holistic carbon sequestration─carbonous soil minerals (CSM). This composite sensor was tested on soils with varying carbonate contents using cyclic voltammetry, chromatocoulometry (DC-based), and electrochemical impedance spectroscopy to determine signal output as a function of increasing dose. To determine the in-field capability, a portable potentiostat device was integrated into a probe head setup that could be inserted into soil for testing. The results from these experiments showed a linearity of R2 > 0.97 and a measurable sensing range from 0.01% (100 ppm) to 1% (10 000 ppm). Therefore, a first-of-a-kind in-soil sensor system was developed for determining carbonate content in real soil samples using electrochemistry that can be tested in-field to survey the field-deployable and point-of-use capability of the system.

Exploring carbon content variation in microplastics sequestrated from seawater to sediment in the Haima cold seep area

In the decades since plastic has become widely used, deep-sea areas, specifically cold seeps, have developed into plastic sinks. Cold seeps contain clean energy natural gas hydrates and act as a barrier reducing methane migration to the upper water column. However, the impacts of microplastics (MPs) on the carbon content in the cold seep remain unclear. In this study, we explored spatial changes in the MPs’ carbon content (MPC) selecting the Haima cold seep (HCS) as the study area. The main conclusions are as follows: (1) For active seepage areas, the mass abundance of the MPs increases with the methane seepage strength in all water columns and sediment of strong seepage areas. It decreases with the seepage strength in the sediment cores in other areas. (2)The MPC is positively correlated with the depth of the water column in the non-seepage area, while it is negatively correlated in the sediment core. (3) The surface roughness of the MPs was greater in the middle of the water column and the sediment core at ROV1. In the high-pressure and oligotrophic cold seep, the amount and method of microbial utilization of carbon from the MPs deserve greater attention.

Effect of forest-based biochar on maturity indices and bio-availability of heavy metals during the composting process of organic fraction of municipal solid waste (OFMSW)

The main objective of this study was to investigate the effect of biochar on the composting process of the organic fraction of municipal solid waste (OFMSW) under real conditions. Different doses of biochar (1%, 3%, and 5%) were mixed with compost piles to evaluate the variation of temperature, moisture content (MC), organic matter (OM), carbon (C), nitrogen (N), C/N ratio, and heavy metal (HM) contents in comparison with the control treatment (with 0% biochar addition). The results of this study showed that the compost piles combined with different doses of biochar had higher MC. The use of biochar as an additive, even at low doses (1%), was able to increase the compost quality through the reduction of N losses during the composting process. The highest reduction of OM during the composting process was observed in the control pile (without biochar addition) by 48.06%, whereas biochar affected the biodegradability of OM and prevented the reduction of nutrients during the composting process under real conditions. The contents of HMs (Pb, Zn, Ni, Cd, and Cu) showed a significant reduction in all of the compost piles combined with biochar in comparison with the control treatment. Considering that in terms of all compost quality indicators, the piles combined with biochar can regarded as high standard product, the composts obtained from combining the OFMSW with different biochar doses have desirable features to be used as an amendment agent to improve agricultural soil quality.

Relative Sea-Level Fluctuations during Rhuddanian–Aeronian Transition and Its Implication for Shale Gas Sweet Spot Forming: A Case Study of Luzhou Area in the Southern Sichuan Basin, SW China

Most scholars believe that transgression events can contribute positively to organic matter enrichment and shale gas sweet spot development, while whether or not regression events are conducive to shale gas sweet spot development remains to be further discussed. Variations in organic carbon content (TOC), and major and trace elements at the Rhuddanian–Aeronian stage in the Luzhou area, the southern margin of Sichuan Basin, were analyzed in this paper. We discuss differences in paleoenvironment organic matter enrichment and shale sweet spot development during transgression and regression. A transgressive system tract (TST) occurred during the early Rhuddanian stage, while early highstand system tracts (Ehst-1 and Ehst-2) occurred during the late Rhuddanian stage and Aeronian stage, and a late highstand system tract (LHST) developed during the late Aeronian stage. A rise in sea level during the TST in the upper Yangtze resulted in an anoxic environment, where a continuous upwelling current brought about a large number of nutrients in the seawater, significantly increasing paleoproductivity. Strong tectonic subsidence, weak chemical weathering, and a rising sea level together led to a low terrigenous debris supply in the catchment area. Therefore, paleoproductivity and redox conditions were the primary controlling factors of organic matter enrichment at the TST stage, with a clastic supply of secondary importance. With the advance of the Guangxi orogeny, the organic matter enrichment at the EHST-1, EHST-2, and LHST stages was mainly controlled by redox conditions and debris supply. A comparison of the key physical parameters and geochemical indicators of shale reservoirs from these four system tracts suggests that two shale sweet spot types (type I and II) were developed during the Rhuddanian–Aeronian stage, occurring in the TST and EHST-2 stages. High TOC and high microcrystalline quartz content are key to developing type I sweet spots, while enhanced anoxic conditions in the bottom water caused by ephemeral, small-scale sea level rises are the main determinant of class II sweet spots in the later EHST stage.