Characterization Of Organic Matter Research Articles

Improved Characterization of Soil Organic Matter by Integrating FT-ICR MS, Liquid Chromatography Tandem Mass Spectrometry, and Molecular Networking: A Case Study of Root Litter Decay under Drought Conditions.

Understanding of how soil organic matter (SOM) chemistry is altered in a changing climate has advanced considerably; however, most SOM components remain unidentified, impeding the ability to characterize a major fraction of organic matter and predict what types of molecules, and from which sources, will persist in soil. We present a novel approach to better characterize SOM extracts by integrating information from three types of analyses, and we deploy this method to characterize decaying root-detritus soil microcosms subjected to either drought or normal conditions. To observe broad differences in composition, we employed direct infusion Fourier-transform ion cyclotron resonance mass spectrometry (DI-FT-ICR MS). We complemented this with liquid chromatography tandem mass spectrometry (LC-MS/MS) to identify components by library matching. Since libraries contain only a small fraction of SOM components, we also used fragment spectral cosine similarity scores to relate unknowns and library matches through molecular networks. This integrated approach allowed us to corroborate DI-FT-ICR MS molecular formulas using library matches, which included fungal metabolites and related polyphenolic compounds. We also inferred structures of unknowns from molecular networks and improved LC-MS/MS annotation rates from ∼5 to 35% by considering DI-FT-ICR MS molecular formula assignments. Under drought conditions, we found greater relative amounts of lignin-like vs condensed aromatic polyphenol formulas and lower average nominal oxidation state of carbon, suggesting reduced decomposition of SOM and/or microbes under stress. Our integrated approach provides a framework for enhanced annotation of SOM components that is more comprehensive than performing individual data analyses in parallel.

Unravelling the thermodynamic properties of soil ecosystems in mature beech forests

Thermodynamics is a vast area of knowledge with a debatable role in explaining the evolution of ecosystems. In the case of soil ecosystems, this role is still unclear due to difficulties in determining the thermodynamic functions that are involved in the survival and evolution of soils as living systems. The existing knowledge is largely based on theoretical approaches and has never been applied to soils using thermodynamic functions that have been experimentally determined. In this study, we present a method for the complete experimental thermodynamic characterization of soil organic matter. This method quantifies all the thermodynamic functions for combustion and formation reactions which are involved in the thermodynamic principles governing the evolution of the universe. We applied them to track the progress of soil organic matter with soil depth in mature beech forests. Our results show that soil organic matter evolves to a higher degree of reduction as it is mineralized, yielding products with lower carbon but higher energy content than the original organic matter used as reference. These products have higher entropy than the original one, demonstrating how the soil ecosystem evolves with depth, in accordance with the second law of thermodynamics. The results were sensitive to soil organic matter transformation in forests under different management, indicating potential applicability in elucidating the energy strategies for evolution and survival of soil systems as well as in settling their evolutionary states.

Unraveling the impact of Spartina alterniflora invasion on greenhouse gas production and emissions in coastal saltmarshes: New insights from dissolved organic matter characteristics and surface-porewater interactions

Saltmarshes along the Chinese coast are threatened by the invasion of Spartina alterniflora (S. alterniflora). This study was carried out in the Andong Shoal, Hangzhou Bay, China, with the aim of comprehending the intricate impacts of S. alterniflora invasion on greenhouse gases (GHG) production and emissions. To address this issue, we thoroughly examined the chemistry of dissolved organic matter (DOM) and the rate of surface water-porewater interaction. Porewater and surface water samples were collected from farm land, S. alterniflora invaded areas, and Scirpus mariqueter (S. mariqueter) dominated areas. The findings indicated that the invasion of S. alterniflora impeded the interaction between surface water and porewater, resulting in reduced porewater exchange rates within its affected region (0.015–0.440 cm d−1), in contrast to areas dominated by S. mariqueter (9.635–18.232 cm d−1). The invasion also increased dissolved organic carbon concentration in porewater and created a stable and closed soil environment that resulted in DOM with smaller molecule sizes and higher humification levels. The presence of high tryptophan-like fluorescent DOM caused an increase in the production of methane and carbon dioxide in S. alterniflora invaded area. However, both limited surface-porewater exchange and significant differences in GHG concentrations between porewater and surface water suggested that the aerenchyma tissues of S. alterniflora may play an important role in transporting GHG from soil to the atmosphere.

Shale gas‐bearing capacity and its controlling factors of Wufeng–Longmaxi formations in northern Guizhou, China

Great progress has been made in marine shale gas of Wufeng–Longmaxi formations in the Sichuan Basin. However, shale gas exploration in the complex structural belt around the Sichuan Basin still faces great challenges. In this study, shales of Wufeng–Longmaxi formations collected from the northern Guizhou were taken as the studied target, organic matter (OM) characteristics, mineral composition, pore structure, methane adsorption capacity and in situ desorption gas content were measured, and the controlling factors of shale gas content were further discussed. The results indicated that the sedimentary facies of Wufeng–Longmaxi formations in north Guizhou varies from shallow‐water shelf facies to deep‐water shelf facies from south to north, and organic‐rich shales are primarily distributed in Daozhen‐Xishui areas, with a maximum thickness of about 80–100 m. Organic‐rich shales are characterized by high total organic carbon (TOC) content, high thermal maturation and type I–II1 kerogens, which can be comparable with those in commercially produced shale gas field in Sichuan Basin. High‐quality shale gas reservoirs generally have a high content of brittle minerals, making them easier to be fractured. OM pores are the dominanted pore type in the studied shales, followed by intergranular pores associated with brittle minerals, dissolution pores within carbonate grains and microcracks, while clay mineral‐related pores are poorly developed. The Wufeng–Longmaxi Formation shales generally have strong methane adsorption capacities, but these vary greatly across different areas. Shale gas adsorption capacity is primarily controlled by TOC content and thermal maturation level. Similarly, total gas content, including desorption gas and lost gas, varies greatly in different areas, and it is obviously lower than that in Fuling and Luzhou shale gas field, due to the loss of shale gas and low‐pressure coefficient in the complex structural zone. It is worth explaining that shale gas is not always low in northern Guizhou, which is determined by burial depth and the distance of great fractures. Shale gas content is relatively high in LY1 well and DY1 well in Xishui‐Daozhen area, and it is extremely low in TY1 well and AY1 well in Tongzi‐Zheng'an area. Shale gas content in the same structural unit is primarily influenced by TOC content, OM pore development degree and water saturation. However, different structural units have different shale gas contents, due to the differences in preservation conditions. Shale reservoirs with good preservation conditions, that is, wide and gentle structure, far from a large fault and great burial depth, generally have high shale gas contents.

Pre-hispanic wetland irrigation and metallurgy in the South Andean Altiplano (Intersalar Region, Bolivia, XIVth and XVth century CE)

The high-altitude Andean Altiplano has been subject to abrupt climate changes during the Holocene. The resulting impact on the hydrological cycle has obliged ancient societies to adapt and develop strategies to face droughts and sustain agropastoral activities. Here, we present the results of archaeological prospections together with the biogeochemical characterization of a well-dated core collected at Saitoco wetland in the arid southern Altiplano (Intersalar Region, Bolivia). Archaeological survey allowed the mapping of a network of channels collecting water from the surrounding mountains to the wetland, and the presence of small copper mines and metallurgical installations. Traces and major element concentrations and accumulation rates, together with elemental and isotopic characterization of organic matter (OM) (i.e., Corg and δ13Corg) in the wetland core have been used to document the evolution of the landscape in relation to climatic and anthropogenic pressure. While OM, bromine (Br), selenium (Se) and mercury (Hg) data were used to assess the variability of precipitations during the Late Holocene (4.2 ka BP to the present), local and regional mining activities have been reconstructed through the variations of lead (Pb), copper (Cu), and antimony (Sb). Our results show an abrupt change in OM composition during the 14th and 15th century CE, characterized by an abrupt shift in δ13Corg synchronous with a rise in Br, Se and Hg, testifying for the waterlogging of the wetland during a known arid period in the region. This change is attributed to anthropogenic transformation of the landscape through the irrigation of the wetland by channeling streams from the surrounding mountains. At the same time, a mining pollution signal was recorded supporting local Cu mining and metallurgy. The mining signal then reached its maximum values during the Inca and Colonial periods, which matches with reported enhanced mining activities in the region. From the colonial era onward, the wetland progressively dried up, likely resulting from the abandonment of the site. Through the combination of a biogeochemical record and archaeological prospections, this study provides evidences that societies of the arid Intersalar region have transformed their landscape and developed wetland irrigation and mining during the arid 14th and 15th century CE Period.

Organic matter characteristics and hydrocarbon generation potential of the Middle Jurassic–Lower Cretaceous succession in the Mesopotamian Foredeep Basin, Iraq

Organic matter characteristics and hydrocarbon generation potential of the Middle Jurassic–Lower Cretaceous succession in the Mesopotamian Foredeep Basin, Iraq

Impact of deforestation on the hydrogen, oxygen and iron isotope compositions of Amazonian streams

We examined the consequences of deforestation and pasture establishment on H, O and Fe isotope cycling in the hydrosphere, with focus on small watersheds from the central and eastern part of Brazilian Amazonia. The δ18O- δD relationships in stream water samples show that the evaporation effect is greater in pasture than in forest, thereby highlighting the impact of deforestation on atmospheric water circulation and rainfall.A clear effect of deforestation was also found on the dissolved load of these streams. Water temperature, pH, conductivity, major cations and dissolved carbon organic content are lower in forest streams compared to those from deforested areas. Dissolved (i.e., filtrate <0.45 μm) iron concentrations are typically higher in these tropical forest streams. They also show δ57Fe signatures commonly higher than that of the continental crust (i.e., > 0.1‰). In these black waters enriched in organic matter, the heavier iron isotope composition in the forested areas is related to the oxidized Fe strongly bound to colloidal organic matter. On the other hand, dissolved iron from streams draining older deforested areas shows isotopic compositions usually lighter than the continental crust (δ57Fe < 0.1‰). The negative δ57Fe signatures of these areas are likely caused by deforestation involving erosion and rejuvenation of soils in valleys, which leads to the occurrence of a partial iron reduction in the soils. These modifications increased the proportion of isotopically light, dissolved and more reduced Fe in the streams.Those effects are less obvious on more recent pastures since they display more chemical and isotopic scatter along the sampling months. In a stream flowing through an area undergoing slash and burned deforestation within the year, dissolved iron concentrations and isotopic compositions are much more scattered, with δ57Fe values varying by >10 ‰ as a result of fire or heavy rain events. This likely depicts the disruption of the iron cycling in the water-soil-plant system with strong changes in the soil mineralogy, organic matter characteristics and biomass activity resulting from the forest fire. Our results suggest that more than a decade is needed to reach a new dynamic steady state of the Fe biogeochemical cycle in pastures.Hence, the contrasted Fe isotopic compositions between the streams draining pristine tropical forests and those from deforested areas indicate that, like H and O isotopes, Fe isotopes are a sensitive indicator of the transformations affecting the biogeochemical cycling of tropical environment in response to deforestation. However, in contrast to hydrogen and oxygen isotopes that reveal the exchanges between surface waters and atmosphere, iron isotopes rather highlight the physical-chemical reactions occurring between surface waters and the soils, but with the biomass mediation for all three isotopic tracers.

Evaluation of characterization and adsorption kinetics of natural organic matter onto nitric acid modified activated carbon

Natural organic substances (NOM) found in drinking water are a major contributor to disinfectant by-product formation and are potentially toxic to humans. Traditional water treatment techniques may not always effectively treat NOMs. Therefore, an advanced treatment method such as adsorption can be inexpensive, simple and efficient. The selected adsorbent's and the NOMs properties both affect the removal effectiveness of the adsorption method. Activated carbon (AC), which is widely used in real-scale water treatment plants, has been modified and used in recent years In order to oxidize the porous carbon surface, raise its acidic qualities, eliminate mineral components, and enhance the surface's hydrophilic qualities. In this research, AC was modified with nitric acid (M-PAC) and NOM removal was investigated. In addition, it is discussed how the modification with nitric acid changes the adsorbent structure and chemistry. A morphology with smooth and irregular voids was observed as a result of nitric acid modification of the original AC by SEM analysis. The particle size increased from 387.65 nm to 502.07 nm for the M-PAC adsorbent. The FTIR spectrum indicates that structures connected to aromatic rings get formed in the M-PAC adsorbent as a result of the modification. The highest NOM removal for the original powdered activated carbon (PAC), 47%, was observed at 36 hours of contact time. On the other hand, M-PAC adsorbent achieved 40% NOM removal at contact times of 72 hours and above. It was concluded that the pseudo-second order kinetic model better represented NOM adsorption for both adsorbents.

Hydrocarbon composition and properties of oils of the Apsheron Peninsula and their connection with geological mode of occurrence

Hydrocarbon accumulations in the Lower Pliocene Productive Series of Apsheron Peninsula have formed owing to subvertical hydrocarbon migration from the underlying Maykop and Diatom source formations. This concept has been substantiated by the recent studies based on the molecular-isotopic characteristics of organic matter, oil and gas. The most notable feature of the Apsheron oils is the stable predominance of paraffin-naphthene HCs in all oil fractions, and this is true for all the fields considered. Meanwhile two geological features had major influence on formation of the composition and properties of Lower Pliocene oils in Apsheron Peninsula. In structures unaffected by tectonic erosion more mobile light components of oils happened accumulated in upper stratigrafically younger horizons due to natural fractionation of hydrocarbons on their upward migration routes. In anticlinal folds with washed out crestal part physical and biochemical degradation has caused the loss of light hydrocarbons, first of all of methane fraction, and in this way weighting up of oils. From top to bottom, towards the basal PS suites the distillate fractions show reduction in the light ends (gasoline and naphtha), which is predictably accompanied by an increase in the amount of bottoms. Compositional variation in oil hydrocarbons laterally and through the section of the peninsula is graphically demonstrated on the basis of gasoline, ligroin, kerosene and diesel cuts of oil. In terms of elemental composition, the deeper the stratigraphic occurrence of the reservoir, the more the whole oil is enriched in sulphur- and nitrogen-containing polar compounds. Keywords: oil; hydrocarbon composition; Apsheron Peninsula; the Productive Series; Lower Pliocene.

A Comparative Study on Soil-Crop Selenium Characteristics in High-Incidence Areas of Keshan Disease in Chinese Loess and Black Soil

With the gradual emphasis on health by people, the research on the pathogenesis of endemic diseases has become increasingly in-depth. Through analyzing the environmental selenium characteristics and conducting a comparative study in typical areas of Chinese loess and black soil in this paper, it is concluded that the environmental selenium in the two regions has different characteristics. The soil in the loess area has the characteristics of high alkalinity, low selenium, and relatively high selenium availability, and the crops are selenium-deficient, while the soil in the black soil area has the characteristics of high organic matter, low selenium availability, and relatively high selenium in crops. The research concluded that the environmental occurrence mechanism of Keshan disease in the loess area and the black soil area is different. Keshan disease can be induced in both low-selenium and sufficient-selenium environments, and environmental selenium should be one of the inducing factors of Keshan disease. This research provides a reference for predicting the areas where Keshan disease occurs and for disease prevention, and it can also serve in the prevention and control of endemic diseases.

Characterization of natural organic matter in Wyoming-type bentonites irradiated at varied moisture levels

Wyoming-type bentonite clay (MX-80; Wyoming, USA) will be used in a deep geological repository (DGR) for the long-term storage of used nuclear fuel in Canada. The natural organic matter (NOM) found in bentonite may serve as a microbial nutrient source and potentially compromise the performance of the used fuel containers. Previous investigations indicate that NOM is present in low concentrations in MX-80 and has undergone extensive diagenetic alteration, though limited knowledge is available regarding NOM chemistry under simulated DGR conditions. Of particular concern is the possibility for gamma-radiation to alter NOM dissolution and reactivity due to the presence of reactive species generated by water radiolysis in Wyoming-type bentonites. In this study, NOM chemistry was investigated using complementary molecular-level techniques following exposure to a total gamma-radiation dose of 100 kGy (1.08 kGy/h for 93 h) at varied moisture levels (20%, 40%, 60% and 80%) and room temperature. Treated samples exhibited relatively low total organic carbon concentrations (0.074–0.232%), with no evidence of any major changes in total, organic, and inorganic carbon concentrations. Solid-state 13C NMR spectroscopy detected no changes in solid-phase NOM chemistry after irradiation. Solubilization of NOM increased significantly with radiation exposure at 80% moisture, suggesting higher levels of water saturation may enhance dissolved organic matter (DOM) production. Solution-state 1H nuclear magnetic resonance (NMR), and UV–Vis analyses did not identify any significant differences in DOM composition. More sensitive, targeted compound analysis revealed significant decreases in total n-alkanol concentration at lower moisture content levels (20% and 40%). Several individual compound concentrations also differed significantly at the nanogram-level, including n-octacosanol and several n-alkanoic acids at elevated moisture levels (60% and 80%). These findings suggest the majority of NOM in MX-80 remains chemically stable under the anticipated initial conditions of the proposed DGR.

Exploring the molecular characteristics of organic matter in low-rank coals using GC×GC/TOF-MS plus data mining

In-depth understanding the form of organic matter in low-rank coals contributes to the clean and efficient utilization of coals. Two low-rank coals were successively dissolved with cyclohexane, acetone and methanol at 300 °C, respectively. Six thermal dissolution (TD) extracts were comparatively analyzed using comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC×GC/TOF-MS). Cyclohexane tends to extract low-polar compounds inherent in coal, such as aliphatic hydrocarbons, arenes and phenols. Acetone can extract monocyclic aromatic hydrocarbons containing alkyl side chains. Meanwhile, acetone can form N-H⋯O hydrogen bonds with nitrogen-containing organic compounds (NCOCs), facilitating the extraction of a greater quantity of NCOCs. Methanol breaks the ArCH2OArR structural unit within coal molecules and forms the dominant alkyl-substituted phenol. It was revealed that sequentially TD at 300 °C using different solvents only breaks intermolecular forces and weak covalent bonds. Additionally, a series of isomers of tricyclic aromatic hydrocarbons and alkylphenols were authenticated by GC×GC/TOF-MS. Principal component analysis and hierarchical clustering analysis were applied to mine effective molecular information from the extensive MS data. The statistical results indicate that solvent had a significant impact on the structure and composition of the TD extracts, more so than the variations in coal species. Thus, the conjunction of GC×GC/TOF-MS and chemometrics provided methodological guidance for an enhanced comprehension of the molecular structure of coals.

Size-resolved molecular characterization of water-soluble organic matter in atmospheric particulate matter from northern China

Atmospheric particulate matter (PM) affects visibility, climate, biogeochemical cycles and human health. Water-soluble organic matter (WSOM) is an important component of PM. In this study, PM samples with size-resolved measurements at aerodynamic cut-point diameters (Dp) of 0.01–18 μm were collected in the rural area of Baoding and the urban area of Dalian, Northern China. Non-targeted analysis was adopted for the characterization of the molecule constitutes of WSOM in different sized particles using Fourier transform-ion cyclotron resonance mass spectrometry. Regardless of the location, the composition of WSOM in Aitken mode particles (aerodynamic diameter <0.05 μm) was similar. The WSOM in accumulation mode particles (0.05–2 μm) in Baoding was predominantly composed of CHO compounds (84.9%), which were mainly recognized as lignins and lipids species. However, S-containing compounds (64.2%), especially protein and carbohydrates species, accounted for most of the WSOM in the accumulation mode particles in Dalian. The CHO compounds (67.6%–79.7%) contributed the most to the WSOM in coarse mode particles (>2 μm) from both sites. Potential sources analysis indicated the WSOM in Baoding were mainly derived from biomass burning and oxidation reactions, while the WSOM in Dalian arose from coal combustion, oxidation reactions, and regional transport.

From laboratory to pilot-scale: Assessing dissolved organic matter, biological stability and per- and polyfluoroalkyl substances removal on managed aquifer recharge performance

Managed aquifer recharge (MAR) is a promising technique for enhancing groundwater resources and addressing water scarcity. Particularly, this research highlights the novelty and urgent need for MAR facilities in the Chungcheongnam-do region of South Korea as a solution to augment groundwater resources and combat water scarcity. This research encompasses a comprehensive assessment, ranging from laboratory-scale column experiments to pilot-scale tests, focusing on dissolved organic matter (DOM) characterization, natural organic matter (NOM) removal, and water quality improvement, including biological stability. In the laboratory, DOM characteristics of source water and recharged groundwater were analyzed using advanced dissolved organic characteristic tools, and their potential impacts on water quality, as well as per- and polyfluoroalkyl substances (PFASs) were assessed. DOM, total cell counts, and several PFASs with molecular weights >450 Da (particularly long-chain PFASs showing >99.9 % reduction) were effectively reduced in a laboratory-scale experiment. A laboratory-scale column study revealed that most selected PFASs were not effectively removed. Moving to the pilot-scale, a series of experiments were conducted to assess NOM removal during soil passage. Similar to the results of the laboratory-scale experiment, MAR demonstrated significant potential for reducing NOM concentrations, thus improving water quality. Regarding biological stability, assimilable organic carbon in production well (i.e., final produced water by MAR process) was lower than both two sources of surface water (e.g., SW1 and SW2). This suggests that water derived from PW (i.e., production well) exhibited biological stability, undergoing effective biodegradation by aerobic bacteria during soil passage. The findings from this study highlight the critical importance of implementing MAR techniques in regions facing water scarcity, emphasizing its potential to significantly enhance future water security initiatives.

Regional differences in lead (Pb) and tetracycline (TC) binding behavior of sediment dissolved organic matter (SDOM): Effects of DOM heterogeneity and microbial degradation

Lake Nansi, primarily dominated by macrophytes, faces threats from heavy metals and antibiotics due to human activity. This study investigated sediment dissolved organic matter (SDOM) characteristics and complexation of lead (Pb) and tetracycline (TC) in barren zone (BZ) and submerged macrophytes zone (PZ). Additionally, a microbial degradation experiment was conducted to examine its impact on the regional variations in complexation. SDOM abundance and protein-like materials in PZ was significantly greater than in BZ, indicating a probable contribution from the metabolism and decomposition of submerged macrophytes. Both zones exhibited a higher affinity of SDOM for Pb compared to TC, with all four components participating in Pb complexation. Protein-like materials in PZ had a higher binding ability (LogKPb=4.19 ± 1.07, LogKTC=3.89 ± 0.67) than in BZ (LogKPb=3.98 ± 0.61, LogKTC=3.69 ± 0.13), suggesting a potential presence of organically bound Pb and TC due to the higher abundance of protein-like materials in PZ. Although microbial communities differed noticeably, the degradation patterns of SDOM were similar in both zones, affecting the binding ability of SDOM in each. Notably, the fulvic-like component C4 emerged as the dominant binding material for both Pb and TC in both zones. Degradation might increase the amount of organically bound TC due to the increase in the LogKTC.

Effects of UV/Cl2 and UV/PDS advanced oxidation on chemical characteristics of typical organic matter in reclaimed water

In this research, humic acid was selected as a typical organic substance in reclaimed water, and the effects of higher oxidation of UV/Cl2 and UV/PDS on its chemical composition, including aromaticity, molecular weight and fluorescence characteristics were investigated. Results showed that under the same oxidation conditions, the UVA254 removal rate of UV/Cl2 was higher than that of UV/PDS, but with the increase of pH, the UVA254 removal rate of both decreased. Increasing the oxidant concentration could improve the UVA254 removal rate, but UVA254 would not continue to decrease after a certain concentration (Cl2 0.5mM, PDS 0.75mM). After oxidation, organics whose molecular weight &gt;6520 Da significantly decreased, molecular weight 350-1690 Da significantly increased, with increasing UV dose, the molecular weight of 350-1690 Da decreased in UV/Cl2, but continued to increase in UV/PDS. The fluorescent regions of fulic acids under different treatments were effectively degraded after oxidation. The degradation efficiency of UV/Cl2 and UV/PDS reached 87.6% and 83.3% respectively with 0.75mM oxidant and 1500 mJ/cm2 UV light.

Deciphering dissolved organic matter characteristics and its fate in a glacier-fed desert river—the Tarim river, China

The bioavailable diverse dissolved organic matter (DOM) present in glacial meltwater significantly contributes to downstream carbon cycling in mountainous regions. However, the comprehension of molecular-level characteristics of riverine DOM, from tributary to downstream and their fate in glacier-fed desert rivers remains limited. Herein, we employed spectroscopic and high-resolution mass spectrometry techniques to study both optical and molecular-level characteristics of DOM in the Tarim River catchment, northwest China. The results revealed that the DOC values in the downstream were higher than those in the tributaries, yet they remained comparable to those found in other glacier-fed streams worldwide. Five distinct components were identified using EEM-PARAFAC analysis in both tributary and downstream samples. The dominance of three protein-like components in tributary samples, contrasting with a higher presence of humic-like components in downstream samples, which implied that the dilution and alterations of the glacier DOM signature and overprinting with terrestrial-derived DOM. Molecular composition revealed that thousands of compounds with higher molecular weight and increased aromaticity were transformed, generated and introduced from terrestrial inputs during downstream transportation. The twofold rise in polycyclic aromatic and polyphenolic compounds observed downstream compared to tributaries indicated a greater influx of terrestrial organic matter introduced into the downstream during water transportation. The study suggests that the glacier-sourced DOM experienced minimal photodegradations, with limited influence from human activities, while also being shaped by terrestrial inputs during its transit in the alpine-arid region. This unique scenario offers valuable insights into comprehending the fate of DOM originating from glacial meltwater in arid mountainous regions.

Experimental Open Air Burning of Vegetation Enhances Organic Matter Chemical Heterogeneity Compared to Laboratory Burns.

Wildfires produce solid residuals that have unique chemical and physical properties compared to unburned materials, which influence their cycling and fate in the natural environment. Visual burn severity assessment is used to evaluate post-fire alterations to the landscape in field-based studies, yet muffle furnace methods are commonly used in laboratory studies to assess molecular scale alterations along a temperature continuum. Here, we examined solid and leachable organic matter characteristics from chars visually characterized as low burn severity that were created either on an open air burn table or from low-temperature muffle furnace burns. We assessed how the different combustion conditions influence solid and dissolved organic matter chemistries and explored the potential influence of these results on the environmental fate and reactivity. Notably, muffle furnace chars produced less leachable carbon and nitrogen than open air chars across land cover types. Organic matter produced from muffle furnace burns was more homogeneous than open air chars. This work highlights chemical heterogeneities that exist within a single burn severity category, potentially influencing our conceptual understanding of pyrogenic organic matter cycling in the natural environment, including transport and processing in watersheds. Therefore, we suggest that open air burn studies are needed to further advance our understanding of pyrogenic organic matter's environmental reactivity and fate.

Source rock assessment and organic matter characterization of the Oligocene upper Shahejie and Dongying formations in the Nanpu depression of the saline lacustrine Bohai Bay basin, China: Geochemical, palynological, and mineralogical perspectives

The Bohai Bay Basin, located in eastern China, is a significant petroliferous, non-marine rift basin, underwent intricate tectonic activities throughout the Cenozoic. The Nanpu Depression in the Huanghua sub-basin in the northern part of the basin was controlled by Paleogene rifting and increased subsidence. These geological processes resulted in the deposition of the Shahejie and Dongying formations, which exhibited varying quantities and qualities of organic matter. Eighty drill cuttings samples of the Paleogene First Member (Es1) and the overlying Third (Ed3) and Second (Ed2) members of the Shahejie and Dongying formations, respectively, were investigated. An integrated approach including organic and inorganic geochemistry, palynology, and mineralogy was employed to assess the paleoredox and marine incursion conditions, source rock quality and levels of thermal maturity, and factors that governed organic matter accumulation. Results indicated that the Es1 Member was deposited under anoxic conditions, resulting in the accumulation of organic matter-rich mudstones in the Nanpu Depression. Abundant pollen grains and acritarchs were found in the Es1 Member yielded along with minor occurrences of dinoflagellate cysts, freshwater algae, and spores. Terrestrial palynomorph composition provided evidence of increased terrestrial runoff, while the high abundance of acritarchs, accompanied by some dinoflagellate cysts, confirmed episodes of marine incursion and deposition under hypersaline conditions in the lacustrine Bohai Bay Basin. The Ed2 Member exhibited poor to fair amounts of organic matter and a limited potential of hydrocarbon generation with a variety of kerogen Types, including IV, III, II/III, and II. The Ed3 Member shows fair to good organic matter richness and hydrocarbon potential of kerogen Types III, II/III, and II. The Es1 Member emerged as the most promising source rock within the studied interval, boasting good to excellent organic matter richness, and fair to good hydrocarbon generation potential of kerogen Types III and II/III. Evaluating the thermal maturity of organic matter, based on Tmax and VRo-Eq% and related cross-plots, revealed that the Shahejie and Dongying formations are still in the immature to the early stage of the oil window. The mineralogical composition of the Es1 Member primarily consists of clay and quartz with some carbonate and accessory minerals, such as epigenetic halite, dolomite, and plagioclase. Weak correlations observed between the total organic carbon (TOC) and mineral components indicated that the availability of organic matter was primarily controlled by enhanced production and preservation rather than limited dilution under saline lacustrine, oxygen-deprived, and well-stratified water column conditions. Regional investigations of the Es1 Member confirmed the widespread anoxia and deposition of organic-rich source rocks in the Bohai Bay Basin during the Oligocene.

Palaeodepositional environment, implications of Glossopteris flora, and organic matter characteristics from the Lower Permian, Karo Open Cast Mine, East Bokaro Coalfield, Damodar Basin, India

The present study deals with the Early Permian floral diversity, palaeoenvironment, palaeoclimate and depositional setting using a multiproxy approach that includes morphotaxonomy, palynology, and organic geochemistry of Karo OCM (Open Cast Mine), East Bokaro Coalfield, Damodar Gondwana Basin, India. The Permian sediments of Peninsular India are widely regarded as fluvial, along with some marine incursions. The macroplant fossil assemblage exhibits the presence of Glossopteridales, comprising Glossopteris, Gangamopteris, and Vertebraria, as well as Coniferales, which includes Noeggerathiopsis. The palynological assemblage encompasses the dominance of the striate bisaccate pollen Faunipollenites sp. and the sub-dominance of the non-striate bisaccate pollen Scheuringipollenites sp. with glossopterid affinities. The megafloral and palynofloral assemblage confirms the biostratigraphical age to be Late Barakar palynoflora of Kungurian affinity. The studied morphological characteristics, including small to large Glossopteris leaves exhibiting a lanceolate shape, acute apices, and acute cuneate or tapering bases, as well as entire margins with narrower lamina and narrow meshes, suggest the existence of a dense forest with the prevalence of a warm and humid climate during their deposition. The organic geochemical characterization based on functional group and biomarker analyses reveals the diagenetic effects on organic matter. Aliphatic symmetric (∼2865–2855 cm-1) and asymmetric stretching (∼2930–2910 cm-1) peaks are identifiable in coal samples, whereas they are absent in carbonaceous shale. The A-factor vs. C-factor plot suggests that the kerogen type is type III, which can generate mainly gaseous kerogen. The vitrinite reflectance studies (Rr av. 1.1%) show increased maturity of the samples, which is supported by the n-alkane distribution pattern and the absence of hopane terpenoids. The Indian floral assemblages in contemporary of southern Gondwana continents reveal a stronger inclination/affinity with the flora of Africa than that of South America, thereby supporting the age to be of Artinskian–Kungurian.