Evolution Of Organic Matter Research Articles

Relating systematic compositional variability to the textural occurrence of solid bitumen in shales

This study presents Raman spectroscopic data paired with scanning electron microscopy (SEM) images to assess solid bitumen composition as a function of solid bitumen texture and association with minerals. A series of hydrous pyrolysis experiments (1–103 days, 300–370 °C) using a low maturity (0.25% solid bitumen reflectance, BRo), high total organic carbon [(TOC), 14.0 wt%] New Albany Shale sample as the starting material yielded pyrolysis residues designed to evaluate the evolution of solid bitumen aromaticity with increasing temperature and heating duration. Solid bitumen was analyzed by Raman spectroscopy wherein point data were collected from accumulations that ranged in size and degree of association with the mineral matrix. Raman spectroscopy results show that with increasing temperature and experimental duration, solid bitumen aromaticity increases and compositional variability decreases. With regards to texture and composition, coarser-grained solid bitumen (>1.3 μm from nearest mineral grain) has consistently higher, but less variable aromaticity than thinner, wispy solid bitumen which is more intimately associated with the mineral matrix. Collocated scanning electron microscope images were used to provide qualitative assessments of porosity hosted by the organic matter. These paired data sets suggest that solid bitumen porosity development and molecular composition are linked, and these parameters are related to the textural relationships of the organic matter within the whole rock. These results are discussed with perspective towards understanding how rock fabric and texture can influence organic matter evolution during thermal maturation of organic-rich marine shales and inform our broader understanding of these important energy resources.

Effects of confining pressure and microscale heterogeneity on hydrocarbon retention and pore evolution from artificial maturation of Eagle Ford Shale

Although shale heterogeneity has recently emerged as a key topic in unconventional petroleum systems, hydrocarbon (HC) retention and pore evolution in organic-rich shales still remain poorly constrained. In this study, an organic-rich Eagle Ford Shale sample (EqVRo = 0.92%) from a shale-oil prospecting well in South Texas was selected for gold-tube pyrolysis experiments to investigate organic matter (OM) -hosted pore development versus confining pressure during thermal maturation. Before heating, the OM-type heterogeneity and associated pore characteristics in the sample were examined by thin section and scanning electron microscopy imaging, combined with elemental mapping by X-ray energy-dispersive spectroscopy. Four forms of OM occurrence that are closely associated with different mineral matrix domains are distinguished, including the ductile oil-bearing primary OM and rigid primary OM in the siliceous-argillaceous seams, as well as the secondary OM in coccolith-rich lenses and in foraminifera chambers. From heating experiments, the pressure effect on pore evolution was found to be pronounced for the secondary OM in the foraminifera chambers, in which the coalescence of small pores to larger pores upon OM maturation was accelerated by increasing fluid pressure, accompanied by arrangement and densification of OM structures. However, the expulsion effect as a function of confining pressure seems to be evident only for the secondary OM in the coccolith-rich lenses. In contrast, the two types of primary OM in the siliceous-argillaceous seams do not show any apparent changes in pore development over the investigated pressure range of 10 to 120 MPa, probably due to stiffer mechanical properties of primary OM as compared to secondary OM. The discrepancies in pore evolution of different OM types as a response to the variation in confining pressure upon maturation primarily depend on the physical-chemical properties of these various OM materials.Of further importance, observed differences in OM evolution and associated pore characteristics in response to the variation in confining pressure imply that the microscale heterogeneity of shale fabric controls the extent of oil retention and pore evolution. In contrast to the intragranular pores in the foraminifera chambers, the intergranular pores in the coccolith-rich lenses from the Eagle Ford Shale sample are relatively smaller, yet more likely interconnected. Thus, these coccolith-associated pores may provide not only significant storage space but also a major flow pathway for HC production. Our investigation at the microscopic scale provides concepts indicating that HC retention and OM-hosted pore evolution occur differently in two contrasting types of mineral matrix pores, which is critical to successful unconventional shale oil and gas exploration in sedimentary basins.

Multi-Phases Fluid Activity Characteristics of Longmaxi Formation and Its Impact on Resistivity in the Changning Area, Southern Sichuan Basin, Southwest China

Wells with low gas content and low resistivity in the Changning area, southern Sichuan Basin were selected for this study. The burial-thermal history was reconstructed and the characteristics of multi-phase fluid activity were clarified using microscopic observation and testing of fluid inclusions in the Longmaxi shale fracture veins. Compared with wells with a high gas content and high resistivity, the influence of fluid activity on resistivity was analyzed. The results showed that the thermal evolution of the bituminous inclusions trapped in the veins has reached the stage of carbonaceous-metamorphic bitumen, and the organic matter is fully cracked for gas generation, with some organic matter exhibiting the phenomenon of “graphitization.” The synchronous fluid with bitumen was existed due to shallow burial with a middle-low maturity stage of about 280 and 292 Ma. Two phases of fluids existed in the deep burial stage, thus maturing for about 103 Ma, and the uplift stage at about 28 and 32 Ma, with high homogenization temperatures (Th) (varying from 185 to 195°C and 165–180°C). The corresponding pressure coefficients varied between 1.67 and 2.09, 1.56 and 1.92 in a moderate-strong high-pressure state. The last two phases of fluid formation in the late uplift stage for about 4 to 19 Ma and 6 to 10 Ma were characterized by low salinity at medium-low Th (varied from 140 to 155°C and 120–135°C), with pressures of 57.47–74.50 MPa and 51.44–59.41 MPa (pressure coefficients of 1.09–1.41 and 1.18–1.37), in an atmospheric-weak overpressure state. In the initial uplift stage after deep burial, the fluid closure in the Changning area was good. In contrast, the wells are filled with low gas content because of the strong tectonic forces causing the shale gas to be released and the multi-phase fluid activity that happens during the late uplift stage. New evidence indicates that the emergence of low resistance in the localized Changning area is not only related to the high degree of evolution of organic matter but is also affected by the multi-phase fluid modification in the late uplift stage.

Response model of fluid–rock ratio to reservoir space in primary formation of shale oil during hydrous pyrolysis

ABSTRACT Due to the presence of geological fluid under actual geological conditions, water–rock interaction will occur between the fluid and reservoir. Thus, to analyse the influence of the water–rock interaction on storage space during the organic matter evolution stages, this study conducted a series of simulation experiments on shales by using a closed autoclave: four temperatures, 250°C, 300°C, 350°C, 400°C, and five fluid–rock ratios (FRRs), 0:20, 4:20, 10:20, 15:20, and 20:20. Low pressure N2 adsorption measurement was conducted on the solid residues. The experimental results show that the effect of temperature on the yield and pore structure of oil shale was the same as the result when the FRR was = 0:20, 4:20 and = 10:20, 15:20, 20:20, respectively. This result showed that temperature remained the main factor that affected the thermal evolution of hydrocarbon generation. Additionally, temperature was beneficial to the generation and storage of shale oil within a certain range, but only occupied the storage space of shale oils or connected a certain storage space beyond a certain range. The variation trend of shale oil yield with increasing FRR under the same simulated temperatures, 250°C and 400°C, was most affected by the FRR, but little change occurred at 300°C and 350°C. This further proved that the ratio of fluid to rock was an indirect acting factor, which affected the evolution of organic matters and then the development of pore structures. Before the oil window (350°C), the lower evolution degree, the higher water content and the more significant effect. In the higher evolution stage, the higher the water content, and the more complete the kerogen reaction, which was also more conducive to the development of pore structures. Therefore, this study promotes the establishment of linear equations on FRR to the gas adsorption capacity, which further provides a theoretical basis and guidance for the exploration and development of shale oil.

Origin of Dolomite in Lacustrine Organic-Rich Shale: A Case Study in the Shahejie Formation of the Dongying Sag, Bohai Bay Basin

In most organic-rich shale reservoirs, dolomite is widely distributed and has different types and crystal sizes. However, the characteristics and formation mechanism of the dolomites in organic-rich shale are still poorly understood. Petrographic and geochemical analyses were performed to interpret the formation of dolomite in the lacustrine organic-rich shale of the Shahejie Formation, Dongying Sag, Bohai Bay Basin. Four types of dolomites, which represent episodic recrystallization, were classified based on crystal size and shape: 1) micritic dolomite (Dol-1), 2) sub-to euhedral (cloudy cores with clear rims) dolomite (planar-e) (Dol-2), 3) anhedral dolomite (coarse planar-s to nonplanar crystals) in phosphatic particles (Dol-3), and 4) fracture-filling anhedral dolomite (Dol-4). Dol-1 has nonplanar mosaic micritic crystals with irregular intercrystalline boundaries and dull cathodoluminescence (CL), suggesting dolomitization during the early burial stage. Dol-1 tends to occur under high paleosalinity and warm conditions. Furthermore, the syngenetic relationship, with abundant framboidal pyrite and gypsum, suggests that bacterial sulfate reduction (BSR) may influence the formation of Dol-1. The high content of Sr and low content of Mn/Sr also indicate less influence on burial. The Dol-2 crystals show cloudy cores with clear rims attributed to progressive dolomitization during burial. Dol-2 is always associated with the organic matter within the organic matter-rich lamina. The anhedral crystals and undulate (sweeping) extinction of Dol-3, which is usually encased by phosphatic particles in the organic-rich lamina, reflect the recrystallization affected by bacteria and the subsequent thermal evolution of organic matter. Dol-4 fulfills the abnormal pressure fractures crosscutting the earlier phases (Dol-1 and Dol-2) with undulate (sweeping) extinction and different rare earth element (REE) patterns. Dol-4 may be affected by hydrothermal fluids, which are influenced by the thermal evolution of organic matter. The 87Sr/86Sr values of the four types of dolomites similarly demonstrate the same dolomitizing fluids. Dol-1 to Dol-3 have similar REE patterns but are different from Dol-4, suggesting that Dol-4 likely resulted from circulation through basinal sediments instead of different fluids. Focusing on the origin of dolomite has been instrumental in understanding the diagenetic evolution, fluid flow, and organic-inorganic interactions in organic-rich shale and, hence, the reservoir formation of shale oil.

Effect of Volcanic Events on Hydrocarbon Generation of Lacustrine Organic-Rich Shale: An Example of the Upper Triassic Galedesi Formation in the Hala Lake Depression, South Qilian Basin, China

The thermal evolution process of organic matter is associated with the complete hydrocarbon generation and expulsion process in shale, however, the thermal evolution of organic matter is a long process and cannot be realized without experimental simulations. Although several scholars have substantially studied the thermal evolution of organic matter, it remains a challenging and much debated issue in the studies of organic geochemistry. Volcanic events are crucial in the enrichment of organic matter, and appropriate heating accelerates the thermal evolution of organic matter. However, how strong-rock baking restricts the evolution of organic matter in shale has not been specifically studied. The South Qilian Basin in China is a typical superimposed basin where complex tectonic movements have induced multiple volcanic events, which makes it a favorable location to perform the aforementioned research. This study used the Galedesi Formation shale in the Hala Lake Depression of the South Qilian Basin as an example for investigating the constraints of the volcanic events related to the thermal evolution of organic matter by integrating the results obtained using the geochemical and petrological methods. Our results demonstrate that the lacustrine Galedesi Formation shale of the Hala Lake Depression in the Late Triassic is a typical deep-lake facies deposit with good hydrocarbon generation potential. However, because of the influence of regional tectonic evolution, the burial depth of shale is not deep and the thermal evolution of organic matter is insufficient. Due to the influence of multiple volcanic thermal events in the later stages, the thermal maturity of organic matter in the Galedesi Formation shale generally exceeds 3.0%, which is abnormally high. The apparent carbonization of organic matter can be observed via scanning electron microscopy. Rapid magma baking typically cannot effectively promote the hydrocarbon generation of shale organic matter. Finally, the burial depth of lacustrine shale of the Galedesi Formation in the Hala Lake Depression of South Qilian Basin is too shallow. Organic matter hydrocarbon generation and later shale preservation conditions are not conducive to the enrichment, accumulation, exploration, and development of shale gas.

Thermal maturity: The controlling factor of wettability, pore structure, and oil content in the lacustrine Qingshankou shale, Songliao Basin

Shale oil resources are abundant in the Qingshankou Formation of the Songliao Basin, but there are significant production differences between wells. Although there are many factors affecting shale oil production capacity, they are all fundamentally reflected in the differences of pore structure and oil-bearing; however, research on the pore structure and oil-bearing characteristics of naturally mature shale is still rarely reported. Lacustrine shales with low to high maturity developed in the Qingshankou Formation, Songliao Basin; these shales can be used as good natural mature samples to reveal the wettability, pore structure, oil content, and evolution of shale under the control of thermal maturity. In this study, geochemistry, oil content, and mineral composition information were analyzed using total organic carbon, thermal maturity, Rock-Eval pyrolysis, and X-ray diffraction; low-temperature nitrogen adsorption–desorption (N2GA), nuclear magnetic resonance (NMR), high-pressure mercury injection, and field emission scanning electron microscopy (FE-SEM) were used to analyze the shale pore structure; and spontaneous imbibition (SI) combined with NMR and contact angle measurement (CAM) experiments were performed to reveal the shale wettability. The results indicate that with the evolution of maturity from low to high, the cracking degree of organic matter (OM) and the amount of hydrocarbon generation increases, and the scale (number, size) of OM pore development continues to increase. The porosity, pore volume, and Brunauer–Emmet–Teller specific surface area of shale increased continuously due to the increased thermal evolution of OM, and a great many of micropores formed in the shale. Therefore, the average pore size decreased with increased maturity. In addition, shale oil content also improves with the continuous hydrocarbon generation of OM in the process of thermal evolution; The wettability of the shale interior and surfaces gradually changes from water wetting to oil wetting when vitrinite reflectivity (Ro) > ∼1.20% and the degree of oil wetting continues to increase as maturity increases. The crude oil generated by kerogen continues to flow from micropores to macropores, and the pore network continues to develop with increasing oil wetting degree, which is beneficial to crude oil migration and accumulation in the shale reservoir.

Fragment ion–functional group relationships in organic aerosols using aerosol mass spectrometry and mid-infrared spectroscopy

Abstract. Aerosol mass spectrometry (AMS) and mid-infrared spectroscopy (MIR) are two analytical methods for characterizing the chemical composition of organic matter (OM). While AMS provides high-temporal-resolution bulk measurements, the extensive fragmentation during the electron ionization makes the characterization of OM components limited. The analysis of aerosols collected on polytetrafluoroethylene (PTFE) filters using MIR, on the other hand, provides functional group information with reduced sample alteration but results in a relatively low temporal resolution. In this work, we compared and combined MIR and AMS measurements for several environmental chamber experiments of combustion-related aerosols to achieve a better understanding of the AMS spectra and the OM chemical evolution with aging. Fresh emissions of wood and coal burning were injected into an environmental simulation chamber and aged with hydroxyl and nitrate radicals. A high-resolution time-of-flight AMS measured the bulk chemical composition of fine OM. Fine aerosols were also sampled on PTFE filters before and after aging for the offline MIR analysis. After comparing AMS and MIR bulk measurements, we used multivariate statistics to identify the functional groups associated the most with the AMS OM for different aerosol sources and oxidants. We also identified the key fragment ions resulting from molecules containing each functional group for the complex OM generated from biomass and fossil fuel combustion. Finally, we developed a statistical model that enables the estimation of the high-time-resolution functional group composition of OM using collocated AMS and MIR measurements. AMS spectra can be used to interpolate the functional group measurements by MIR using this approach. The latter allows us to better understand the evolution of OM during the aging process.

Process and Controlling Factors of Pore Evolution in Marine-Continental Transitional Black Shale—An Example From Permian Shanxi Formation in the Eastern Margin of Ordos Basin

Pore and pore network evolution of shale is critical for the evaluation the pore system in shale gas reservoirs. Thermal maturation effect acts as an indispensable role in porosity evolution. In this paper, high-temperature and high-pressure in-situ thermal simulation experiments were conducted to investigate the process and controlling factors of pore evolution in marine-continental transitional shale. Multiple methods, including scanning electron microscopy (SEM), X-ray diffraction, helium porosimetry and low-pressure N2 and CO2 adsorption were used to investigate the evolution of mineral composition and pore structure at different stages of thermal maturity. The results showed that type III organic matter (OM) generated petroleum with the thermal maturity increasing. The total organic carbon (TOC) decreased by 13.3% when temperature reached 607°C. At the same time, it produced numerous organic and mineral pores during hydrocarbon generation. Besides, some changes in mineral composition have occurred, especially in illite (from 11% to 31%) and kaolinite (from 89% to 69%). In general, it can divide into 3 stages (maturity, high maturity and over maturity) for shale pore system evolution with the thermal maturity increasing. In the low maturity period, large amounts of pyrolytic bitumen and oil generated to fill the pores, causing the pore system to diminish; in the high maturity period, a large number of pores were generated when oil is cracked into gas, resulting in a rapid expansion of the pore system; in the over-maturity period, the cracking of pyrolysis and hydrocarbon slowed down, allowing the pore system to stabilize. Shale pore evolution is primarily controlled by the thermal evolution of OM, and the conversion of inorganic minerals contributes less to pore evolution compared to organic matter. The high maturity period (1.2% < Ro < 2.0%) was the period when extensive pyrolysis and hydrocarbon generated in the Shanxi Formation shale, which contributed mostly for the pores generation and accumulation of shale gas.

New insights into the role of system sealing capacity in shale evolution under conditions analogous to geology: Implications for organic matter evolution and petroleum generation

Closed and semi-closed pyrolysis of a lacustrine shale sample were conducted using the same instrument characterized by lithostatic pressure and limited reactive space in order to unravel the impacts of system sealing capacity on organic matter evolution and hydrocarbon generation in shales under conditions analogous to natural processes. The products and solid residues were subjected to chemical composition determination, gaseous carbon isotopic composition analysis, solvent extraction, and Rock-Eval pyrolysis. Higher organic matter transformation and oil retention contents were obtained at 300–500 °C in the closed pyrolysis system compared to those in the semi-closed system at the same temperature ranges. However, lower yields of hydrocarbons except for methane were obtained in the closed system at this temperature range, while the iso-/n-C4,5 as well as C1/C1-5 values were significantly higher in this system. Stronger recombined reactions between kerogen and hydrocarbons were proposed to occur at 300–500 °C during the closed pyrolysis process, leading to the consumption of oil and hydrocarbon gases. Ultimately, positive deviations of initially more negative δ13C2∼3 values were occurred in the closed system, resulting in similar δ13C2∼3 values from the two systems before secondary cracking of hydrocarbon gases commences, but the δ13C1 value from the closed system was overall more negative. Different water retention ratios and hydrocarbon expulsion efficiencies induced by system sealing capacity are the predominant factor controlling organic matter evolution and petroleum generation during the pyrolysis processes. This highlights that the different gas contents of the Cambrian and Silurian shales in South China may be associated with the differences in the system sealing capacities of shales, although the sedimentary environment of the studied sample is lacustrine, and the lower methane content of the Cambrian shale gas is probably ascribed to semi-closed system. Finally, a higher ratio of oil cracking gas may be an important signal for natural gas systems that have better exploration potential.

Thermal history of the Sabinas - Piedras Negras Basin (Northeastern Mexico): Insights from 1D modelling

The thermal and burial history of the Sabinas-Piedras Negras basin was studied by 1D modelling using vitrinite reflectance values measured on core samples from nine wells. Three heat flow scenarios led to model calibrations, including a simple one and a complex one integrating a thermal anomaly following the maximal burial phase. The differences in hydrocarbon generation curves due to these two scenarios were studied.The studied thermal anomaly induces two distinct phases of primary cracking of kerogen. The first phase is clearly due to burial, whereas the second seems to be due to the thermal event. The increase in the proportion of converted organic matter attributed to this second phase varies depending on the source rocks considered, e.g., for the La Casita source rock, there is a 10% TR increase, whereas that of the La Peña and Eagle Ford source rocks, is 35 and 15% respectively.The thermal evolution of organic matter in the Sabinas-Piedras Negras Basin is mainly due to the burial phase. In contrast, the thermal event considered only causes a temporal shift of hydrocarbon generation. This hydrocarbon generation, primordially gas, occurred mainly before and during the compressive phase (“late Laramide” time step 40-35 Ma [middle-late Eocene]) that affected the Sabinas-Piedras Negras Basin.

Restoration of organic-matter-impoverished arable soils through the application of soil conditioner prepared via short-time hydrothermal fermentation.

The diversity and stability of critical microbial communities are of great importance for ensuring soil fertility. From the perspective of stimulating microbial diversity in organic-matter-impoverished arable soils, soil conditioner with a certain proportion of labile organic carbon was prepared by short-time hydrothermal fermentation (SHF). The effects of applying SHF, along with soil conditioner derived from traditional aerobic fermentation (TF) and heterogeneous fertilizer (HF), on soil texture, dissolved organic matter evolution, the structure of humic acid, and the succession of dominant microbial taxa were evaluated. SHF enhanced the storage capacity of soil organic carbon and nitrogen retention, and increased the relative abundance of Proteobacteria, Firmicutes and Nitrospirae in organic-matter-impoverished arable soil, with Lysobacter as its significant difference species. In conclusion, the proposed soil conditioner and the positive effects observed in this study indicate that it could be used to solve dual problems of food waste recycling and arable soil improvement.

Indicative significance of biomarker parameters on crude oil cracking rate from the Dongpu Depression, Bohai Bay basin of North China

Molecular markers have a strong ability to maintain their own structure. The side chain fracture, isomerization and aromatization show regular response characteristics for the organic matter evolution process, which can measure oil maturity and identify oil cracking degree. In this research, 43 crude oil samples were collected for geochemical investigation in the Dongpu Depression from Bohai Bay Basin of North China. By the gas chromatography (GC) experiments of saturated hydrocarbon and aromatic hydrocarbon, a variety of molecular marker parameters were selected for quantitative evaluation of crude oil maturity and cracking rate, including pristane isomerization index (PIR), C29 sterane parameters, monoaromatic sterane, rearranged sterane (20 S/(20 S + 20 R)), hopane (Ts/(Tm + Ts)), methyl phenanthrene ratio (MPR), Methyl phenanthrene index (MPI), alkyl naphthalene, and alkyl dibenzothiophenes (DBTs). Thus, the crude oil cracking rate in the different regions of Dongpu Depression were calculated quantitatively. The results show that the increase of temperature, the pressure (<40Mpa) and thermochemical sulfate reduction (TSR) action promotes crude oil cracking, whereas the pressure (>40 MPa) generally inhibits the crude oil cracking. In addition, well Wei 20 does not experience prominent thermal history temperature and burial history pressure, but its oil cracking rate is higher than the average cracking rate curve value, suggesting other factors also have an important impact on crude oil cracking, which needs to be further discussed.

Sedimentary environment and organic matter enrichment of black mudstones from the upper Triassic Chang-7 member in the Ordos Basin, Northern China

The black mudstone of the Chang-7 Member is the most important source rock in the Ordos Basin. In order to understand the paleo-climate, weathering, redox conditions, salinity, water temperature, water depth, and primary productivity under which black mudstone of the Chang-7 Member was deposited, we have analyzed total organic carbon (TOC), rock pyrolysis parameters, major elements, and trace elements of 60 black mudstone samples from the Chang-7 Member of the Yanchang Formation in the Ordos Basin. Geochemical indicators such as TOC, volatile hydrocarbon and residual hydrocarbon (S1 + S2), hydrogen index (HI), chloroform asphalt “A”, maximum pyrolysis peak temperature (Tmax), Vitrinite reflectance (Ro), kerogen macerals, and other organic indicators, show that the kerogen type of the Chang-7 Member was type I–II1, the thermal evolution of organic matter was in the mature stage, and it has good hydrocarbon generation potential. The major and trace element characteristics, such as C-value, Sr/Cu, Rb/Sr and Mg/Ca ratios, chemical alteration index(CIA), Sr/Ba, B, Ga-B-Rb trace element triangle, B/Ga, 1000 × Rb/K2O, V/(V + Ni), pristane/phytane ratio (Pr/Ph), foraminiferal Mg/Ca, and Co values indicate that the sedimentary environment of the Chang-7 Member was semi-arid and semi-humid, with continental freshwater, a reductive sedimentary environment, and an average paleotemperature of 16 °C. Based on the analysis of Baxs and Ba/Al ratio, the Chang-7 Member has medium–high primary productivity, which together with the sedimentary environment, played an important role in the enrichment and preservation of organic matter.

Evolution of surface acidity during smectite illitization: Implication for organic carbon cycle

The clay-organic interactions in marine sediments and mudstones have long been concerned and play key roles in preservation of organic matter (OM). As chemically active mineral, smectite could transform into illite naturally, however, how this process affects stability and cycle of OM remains unclear. Here, we find that solid acidity varies greatly in terms of amount, type, and strength during illitization. The amount and strength of Brønsted (B) acid sites are enhanced markedly and interlayer space remains expandable in randomly interstratified illite/smectite, which enables immediate contact of active acid sites and adsorbed OM. In this case, the promotion of clay minerals on OM evolution would be greatly enhanced. Different from the traditional views on the effects of clay-OM interactions on organic carbon cycle, which include adsorptive protection and desorption, a new notion of clay mineral reactor is proposed which allows in-situ decomposition or degradation of OM.

Compost Mixture and Composting Technique Influence Compost Organic Matter Evolution

Compost Mixture and Composting Technique Influence Compost Organic Matter Evolution

Source and formation process impact the chemodiversity of rainwater dissolved organic matter along the Yangtze River Basin in summer

Rainwater dissolved organic matter (DOM) plays an important role in the biogeochemical cycle and evolution of organic matter in the land-atmosphere interface. To better understand their sources and molecular composition in the atmosphere, rainwater samples were collected at six different locations along the Yangtze River Basin. Based on the application of a combined approach including excitation-emission matrix (EEM) fluorescence and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), various sources (terrestrial, anthropogenic, and autochthonous sources) of rainwater DOM were revealed. Results show that the derivatives of biogenic volatile organic compounds were widely distributed and contributed to rainwater DOM along the Yangtze River Basin. In the up-river city Batang, rainwater DOM was affected by the long-range atmospheric transport due to the Indian summer monsoon. Lijiang, a city on the southeastern edge of Tibetan plateau, was related to strong local biomass burning. The industrial cities of Panzhihua and Luzhou showed large differences in organic composition due to distinct industrial types. Fuling, a district in Chongqing Municipality, was significantly contributed by aged organics from biomass burning. While rainwater DOM in Shanghai, a coastal megacity, contained a high fraction of sea spray organics. Further, more than 70% of rainwater DOM molecules are associated with 36 typical transformation mechanisms during rainwater-scavenging processes, e.g., oxidation reactions, dealkylation and decarboxylation. Our study demonstrates that local natural and anthropogenic emissions and climatic conditions strongly shaped the chemodiversity and possible precursor-product pairs of rainwater DOM along the Yangtze River Basin, which helps to better understand the biogeochemical cycles of organic matter in a large-scale watershed under the influence of human activities.

Dominant products and reactions during organic matter radiolysis: Implications for hydrocarbon generation of uranium-rich shales

Organic-rich shales are generally characterized by high uranium (U) contents. The effects of U irradiation on evolution and hydrocarbon generation of organic matter (OM) have attracted substantial attention. However, details on the generation mechanisms of products and the identification of dominant reactions occurring during OM radiolysis remain understudied. In this study, γ ray was used to irradiate immature kerogen and bitumen, and electron beam was for decane. The contents and carbon (C) isotopic compositions of gaseous products, the liquid products of decane, and the functional groups alterations of kerogens and bitumen were detected. The results showed that, the product generation corresponded well to the structural alteration of OM during radiolysis. C–H and R–CH3 rupture contributed to H2 and CH4 generation, respectively. O-containing group cleavage caused CO2 generation, and O2 presence could enhance the oxidation of OM by joining in the structure of OM or by facilitating the formation of new oxides. H2O addition could not only provide O, enhancing the oxidation of OM, but could also provide H, thus promoting H2 generation. We identified cracking, cross-linking, and oxidation reactions during the OM radiolysis. C isotopic composition changes in solid OM could facilitate identification of dominant reactions. Non-closed geological environment of shales promoted the occurrence of cracking reaction. The substantial radiation energy generated from U decay in U-rich shales was significant for OM evolution via decrease in H/C, increasing O/C, and via enhancement of dealkylation, aromatization and unsaturation, which were similar to the thermal effects. Moreover, U irradiation could also promote conventional gas and immature gas generation and could provide exogenous H for hydrocarbon generation of OM, especially for OM in an over mature stage. It is essential to consider the effects of U irradiation on the evolution, hydrocarbon generation, and resources assessment of U-rich shales.

Insight into the organic matter degradation enhancement in the bioelectrochemically-assisted sludge treatment wetland: Transformation of the organic matter and microbial community evolution

Sludge treatment wetland (STW) has been widely used to dewater and mineralize the various sludge, but the low degradation ability of organic matter can limit its application. Bioelectrochemistry has been proven to accelerate the degradation of organic compounds and recover bioenergy from the sludge. In this study, a bioelectrochemical-assisted sludge treatment wetland (BE-STW) system was constructed to determine the most common types of degraded organic matter and the functional bacterial community. It was found that the bioelectrochemistry process contributed to a further removal of the total chemical oxygen demand (TCOD) by 19% (±0.6) and the additional soluble chemical oxygen demand (SCOD) value was 64.10% (±0.63), with a voltage output of 0.961 V and a power density of 0.351 W/m3. The hydrophilic and hydrophobic acid fractions of the sludge were preferentially removed in BE-STW. The tryptophan-like protein and fulvic acid-like substances were totally removed, whereas, the hydrolysis of aromatic organic compounds in the neutral and hydrophobic acid fractions was enhanced. Also, the enrichment of Longilinea and Methylophilus improved the hydrolysis of organic matter. Moreover, the high relative abundance of Thauera, Dechloromonas, and Syntrophorhabdus could accelerate the degradation of aromatic compounds in the BE-STW system. The bacteria from the genus Geobacter was predominantly detected (2.48%) in the anodic biofilm on BE-STW. The results showed that bioelectrochemistry could improve the sludge stabilization degree in STW, accelerate the organic matter degradation and hydrolysis efficiency, and harvest bioelectricity, simultaneously. This technology can provide a new pathway to increase the efficiency of the traditional STW systems.

Coexistence and Development Model of Multi-Minerals Dominated by Multilayer Magma Intrusion

The diversity of coal measure determines the occurrence state and spatial distribution complexity of mineral resources. Abundant resources have become an important part of geological resources and have attracted more and more attention. Coal measure and their overlying and underlying strata often coexist with various mineral resource types, and there is a certain relationship between their genesis and occurrence. In order to further enrich the theory of comprehensive exploration and coordinated development of multi-mineral resources, this paper takes the Huanghebei Coalfield as an example to systematically study the genesis mechanism and occurrence law of coal seam, coalbed methane, and coal-measure shale gas in Late Paleozoic and rich iron ore in Ordovician limestone underlie coal measure. The research is that: 1) The Late Paleozoic Carboniferous-Permian Marine facies, terrestrial facies, and transitional facies all developed in the coal-bearing area in the Huanghebei Coalfield, and the coal seams and mud shales developed well in Shanxi Formation and Taiyuan Formation. 2) Yanshanian magmatic intruded into Ordovician limestone. Contact metasomatism occurred between the ore-bearing hydrothermal fluids and the surrounding rocks, which led to skarn formation. The magnetite mineralization occurred in the metasomatism alteration process, and finally, the contact metasomatic iron deposit was formed; 3) Yanshanian magma intrusion has a significant impact on the generation of coal from coalbed methane and shale gas in the coal measures of Late Paleozoic. The magma carries a lot of heat by baking the coal seam and overlying shale, which is reflected explicitly in the increasing metamorphism degree of coal. Under the action of high temperature, the secondary gas of coal seam and coalbed methane increase sharply. The maturity and thermal evolution of organic matter in shale beds increased, and the shale gas entered a favorable range. The intrusion of magma greatly enhances the thermal evolution of organic matter in coal and shale, forming a variety of coals and promoting the generation and accumulation of coalbed methane and shale gas. At the same time, Mesozoic magmatic intrusion also controlled the formation of rich iron ores. According to the characteristics of mineral development and distribution in the study area, a multi-mineral development and distribution model of “coal - coalbed methane - shale gas - rich iron ore” coexists in the Huanghebei Coalfield, which is referred to as the “Huanghebei model”.