Humified Organic Matter Research Articles

Applying kitchen compost promoted soil chrysene degradation by optimizing microbial community structure

Chrysene, as a high molecular weight polycyclic aromatic hydrocarbon (PAH), has become an important factor in degrading soil quality and constraining the safe production of food crops. Compost has been widely used to amend contaminated soil. However, to date, the main components of kitchen compost that enhance the biodegradation of chrysene in the soil remain unidentified. Thus, in this study, the enhancing effect and mechanisms of kitchen compost (KC) and kitchen compost-derived dissolved organic matter (KCOM) on chrysene removal from soil were investigated through cultivation experiments combined with high-throughput sequencing technology. Additionally, the key components influencing the degradation of chrysene were identified. The results showed that KCOM was the main component of compost that promoted the degradation of chrysene. The average degradation rate of chrysene in 1% KC- and 1% KCOM-treated soil increased by 27.20% and 24.18%, respectively, at different levels of chrysene pollution compared with the control treatment (CK). KC and KCOM significantly increased soil nutrient content, accelerated humification of organic matter, and increased microbial activity in the chrysene-contaminated soil. Correlation analyses revealed that the application of KC and KCOM optimized the microbial community by altering soil properties and organic matter structure. This optimization enhanced the degradation of soil chrysene by increasing the abundance of chrysene-degrading functional bacteria from the genera Bacillus, Arthrobacter, Pseudomonas, Lysinibacillus, and Acinetobacter. This study provides insight into the identification of key components that promote chrysene degradation and into the microbial-enhanced remediation of chrysene-contaminated soil.

Hyperthermophilic composting coupled with vermicomposting stimulates transformation of organic matter by altering bacterial community

Hyperthermophilic composting (HTC) has been proven to be an effective strategy to recycle organic wastes, while vermicomposting (VC) has been widely applied to produce humic fertilizer. The combination of HTC with VC (HVC) is expected to integrate the advantages of both. This study showed that HTC pre-fermentation provided plentiful substances such as dissolved organic matter (DOM) for the subsequent VC enriching humic acid (HA). Compared to thermophilic composting (TC), HVC significantly stimulated the degradation of organic matter (OM) and the production of N-rich HA, and incubated higher diversity of bacterial community. SHapley Additive exPlanations (SHAP), correlation network, Mantel test and PLS-LM model were constructed to identify the potential roles of the key bacterial groups contributing to OM transformation. Firmicutes (e.g., Bacillus and Tuberibacillus) dominant in HTC may mineralize and mobilize OM, providing affluent bioavailable nutrients as part of DOM for microbial metabolism and abundant precursors for HA formation in the further VC. Actinobacteriota (e.g., Microbacterium) and Bacteroidota (e.g., Flavobacterium and Parapedobacter) prominent in VC metabolized DOM, mineralized OM and produced HA probably by enhancing the metabolic activity involved in OM degradation and amino acid generation. However, when DOM was exhausted, some members especially Proteobacteria (e.g., Ochrobactrum, Devosia and Cellvibrio) would change their roles from promoter to inhibitor of mineralization and humification. Altering the nutrient bioavailability and the composition of bacterial community can regulate the mineralization, mobilization and humification of OM. Overall, this study provides new insights into the roles of bacteria participating in transforming organic wastes into HA-rich composts.

Deciphering origins of hydrocarbon deposits by means of intramolecular carbon isotopes of propane adsorbed on sediments

Hydrocarbons are one of the important fluids within the Earth’s crust, and different biotic and abitoic processes can generate hydrocarbon during geological periods. Tracing the sources and sinks of hydrocarbons can help us better understand the carbon cycle of the earth. In this study, an improved approach of adsorbed hydrocarbons extraction from sediments was established. The improved thermal desorption approach, compound-specific isotope analysis and position-specific isotope analysis were integrated to investigate the molecular and intramolecular isotope fractionation between trace hydrocarbon gases within sediments and geological hydrocarbon deposits. The isotopic compositions of the terminal position carbon of propane (δ13Cterminal) serves as a correlation indicator between trace hydrocarbon gases within sediments and geological hydrocarbon deposits. The tight sandstone gas from the Turpan-Hami Basin is a first case study for the application of this novel method to trace hydrocarbon origins. The results showed that the hydrocarbons in the tight sandstone gases in the study area most likely originated from humic organic matter (type III kerogen) at an early mature stage. δ13Cterminal values of the thermally desorbed propane gases from different source rocks were distinguishable and the values of the tight sandstone gases significantly overlap with those of the Lower Jurassic Sangonghe source rocks, suggesting their genetic relationship. Overall, the results provided novel position-specific carbon isotopic constraints on origins of hydrocarbons.

Old-growth Ficus trees provide soil water and carbon storage to urban greenspaces in a Brazilian metropolis

Urban flooding has been considered one of the most severe natural disasters around the world, and urban greenspaces can provide important flood regulation ecosystem services. In Belo Horizonte (Brazil), the woody vegetation, especially the old-growth Ficus trees, appears to protect an urban park against the flooding of the Arrudas river. Thus, we compared the soil water content, soil water-holding capacity, soil aggregation and porosity among a highly permeable urban park planted with herbaceous and woody species, including Ficus, a semi-permeable parking lot with only Ficus and an impermeable site without trees (Disturbed Site-DS). The soil water content and water holding capacity of the urban park did not differ from that of the Ficus site, but it was lower than DS. These results were correlated with soil organic matter (SOM) content, soil aggregation and porosity, suggesting that Ficus trees play an important role in the hydrological cycle. To understand how the Fiscus species provide such soil permeability, we compared the aboveground plant biomass, soil fertility and soil carbon sequestration (total soil carbon, soil organic matter, humic and fulvic acids and soil isotopic δ13 C) in plots with Ficus and without this species within the park as well as in a preserved urban forest and a disturbed square. The outstanding plant biomass produced by Ficus species explained the high soil carbon sequestration, particularly in humic organic matter, favouring soil aggregation, porosity and water retention. Therefore, Ficus species may be considered an exceptional C-sequestering species, contributing for soil stabilization and the hydrological cycle in urban greenspaces.

Approach to the circular economy through agro-livestock waste composting with heat recovery and agricultural use of the resulting compost

In this work, plant waste and cow manure were co-composted to recover the heat generated during the thermophilic stage of composting by heating water through conducting heat exchangers buried in the pile. The parameters associated with the degradation and humification of organic matter during composting and the agronomic and economic value of the final compost were also determined. Furthermore, the effects of adding the obtained compost on soil agronomic characteristics and alfalfa yield and production profitability were compared with those of mineral fertilisation, cow manure and a control without amendment. The total energy recovered from composting was 14,528W or 0.105 MJ kg−1 dry matter of the initial waste mixture. Extracting heat from composting did not negatively affect the quality of the compost since this material had an adequate level of organic matter stability and maturity, notable nutrient content, low concentrations of potentially toxic elements and an absence of phytotoxicity. Moreover, applying compost to the soil increased its organic matter and nutrient content, contributing to greater alfalfa production. Increased alfalfa production led to a higher net income from using compost as an organic fertiliser (16,488 USD ha−1). Therefore, composting agricultural and livestock wastes is a viable method for managing these wastes, obtaining sustainable thermal energy and producing compost with adequate agricultural quality. This contributes to closing agricultural and livestock production cycles with notable economic benefits within a circular economy framework.

Organic Matter Enrichment in Jurassic Hydrocarbon Source Rocks from the Turpan-Hami Basin: Insights from Organic and Elemental Geochemistry.

Petroleum can be generated by thermal cracking of organic matter within sediments, and the organic matter within sediments plays the dominant role in determining oil and gas generation. Organic matter within sediments is characterized by various sources, such as sapropelic organic matter from algal, microbial, and planktonic organisms and humic organic matter from higher plants. Paleo-productivity, terrestrial influx, and depositional environments could obviously influence the enrichment processes of the organic matter within sediments. Organic and elemental geochemical proxies can investigate the sedimentary process and reflect the enrichment characteristics of organic matter. In this study, hydrocarbon source rocks from the Shuixigou Group were collected from the Taibei Sag of the Turpan-Hami Basin, rock-eval pyrolysis was conducted, and stable carbon isotope composition of organic carbon and major and trace element distributions were measured. Based on this, the type and maturation of organic matter, paleo-productivity, terrestrial influx, and depositional paleo-environments were investigated. The results show that the Jurassic hydrocarbon source rocks are characterized by type III kerogen and are in the oil-window stage of maturation. The depositional paleo-environments of hydrocarbon source rocks in different formations are not remarkably different. The water bodies have freshwater oxidizing environments, and the paleo-climatic characteristics are warm and humid. However, the paleo-productivity of samples from the lower Jurassic Sangonghe Formation is higher than samples from other formations. Overall, the organic matter enrichment in Jurassic hydrocarbon source rocks of the Turpan-Hami Basin could be mutually controlled by the paleo-productivity and depositional paleo-environments. The results of this study could provide theoretical insight into deep petroleum exploration and resource evaluation in the Turpan-Hami Basin.

Effects and Mechanisms of Different Types of Biochar on Heavy Metal Passivation during Sludge Composting.

The effects and mechanisms of the different types of biochar on heavy metal passivation are still not fully understood. This study compared the effects of three types of biochar on heavy metal passivation during sludge composting. Compared with composting without biochar, rice husk biochar was most effective for the passivation of Zn and Pb, with increased passivation rates of 1.90% and 20.43%, respectively. In contrast, sludge biochar was the most effective for the passivation of Cr and Hg, with increased passivation rates of 28.30% and 3.09%, respectively. Coconut shell biochar showed the best performance for the passivation of Cu, Ni, As, and Cd, and was enriched with micropore structures, which possibly led to the adsorption and reaction of heavy metals, organic matter, and microorganisms. The improved passivation effect of the rice husk and sludge biochar on heavy metals can be attributed to the improved humification of organic matter. This study suggests that specific types of biochar should be considered for the passivation of different types of heavy metals for practical applications.

Indicators of humus state of virgin and irigated gray-brown soils of khorezm vilayat of Uzbekistan

The humus content, elemental composition and optical density of humic acids in virgin and irrigated soils of the Tashsakinsky massif of the Khorezm region of Uzbekistan were estimated. The studied desert virgin and irrigated soils have characterized by light and medium loamy granulometric composition, dusty-granular structure and slightly alkaline reaction. Carbonates present in small quantities - 3.10-10.60%. The total humus content in the upper horizons varies from 0.19% to 0.76%. In virgin grey-brown soils the humus type is humate-fulvate, agriculture soils are humate. The degree of humification of organic matter in newly irrigated gray-brown-meadow and meadow-marsh soils is higher than in virgin gray-brown soils and decreases down the profile. It was revealed that the optical density of humic acids of virgin gray-brown, irrigated meadow and meadow-marsh soils is characterized by high values. The percentage of the sum of humic acid elements differs little from virgin soils to old-irrigated meadow soils. In the lower horizons, oxidation increases by 1.02 times compared to other studied soils. For the first time, the elemental composition of humic acids in virgin and irrigated soils of the desert zone of the Tashsakinsky massif of the Khorezm region was determined. The elemental composition of humic acids showed the oxidizability of humic acids, which decreases from top to bottom along the profile, which is associated with the features of the genesis of the studied soils, the age of irrigation and the degree of cultivation of these soils.

Fungi play a crucial role in sustaining microbial networks and accelerating organic matter mineralization and humification during thermophilic phase of composting

Fungi play an important role in the mineralization and humification of refractory organic matter such as lignocellulose during composting. However, limited research on the ecological role of fungi in composting system hindered the development of efficient microbial agents. In this study, six groups of lab-scale composting experiments were conducted to reveal the role of fungal community in composting ecosystems by comparing them with bacterial community. The findings showed that the thermophilic phase was crucial for organic matter degradation and humic acid formation. The Richness index of the fungal community peaked at 1165 during this phase. PCoA analysis revealed a robust thermal stability in the fungal community. Despite temperature fluctuations, the community structure, predominantly governed by Pichia and Candida, remained largely unaltered. The stability of fungal community and the complexity of ecological networks were 1.26 times and 5.15 times higher than those observed in bacterial community, respectively. Fungi-bacteria interdomain interaction markedly enhanced network complexity, contributing to maintain microbial ecological functions. The core fungal species belonging to the family Saccharomycetaceae drove interdomain interaction during thermophilic phase. This study demonstrated the key role of fungi in the composting system, which would provide theoretical guidance for the development of high efficiency composting agents to strengthen the mineralization and humification of organic matter.

Role of the molecular structure of humified organic matter in rice plant response to environmental lead pollution.

Humified organic matter has been shown to decrease Pb toxicity in plants. However, there are still gaps in our understanding of the mechanism by which this phenomenon occurs. In this study, we aimed to assess the ability of humic substances (HSs), humic acids (HAs), and fulvic acids (FAs) to enhance defense mechanisms in rice plants under lead (Pb)-stressed conditions. HS fractions were isolated from vermicompost using the chemical fractionation methodology established by the International Humic Substances Society. These fractions were characterized by solid-state NMR and FTIR. Chemometric analysis was used to compare humic structures and correlate them with bioactivity. Three treatments were tested to evaluate the protective effect of humic fractions on rice plants. The first experiment involved the application of humic fractions along with Pb. The second comprised pretreatment with humic fractions followed by subsequent exposure to Pb stress. The third experiment involved Pb stress and subsequent treatment with humic fractions. The root morphology and components of the antioxidative defense system were evaluated and quantified. The results showed that HS + Pb, HA + Pb, and FA + Pb treatment preserved root growth and reduced the levels of O2- and malondialdehyde (MDA) in the roots by up to 5% and 2%, respectively. Pretreatment of the plants with humic fractions promoted the maintenance of root growth and reduced the contents of O2-, H2O2, and MDA by up to 48%, 22%, and 20%, respectively. Combined application of humic fractions and Pb reduced the Pb content in plant tissues by up to 60%, while pretreatment reduced it by up to 80%. The protective capacity of humic fractions is related to the presence of peptides, lignin, and carbohydrate fragments in their molecular structures. These results suggest that products could be developed that can mitigate the adverse effects of heavy metals on agricultural crops.

Enhancing bioavailable carbon sources and minimizing ammonia emissions in distillery sludge and distiller's grains waste co-composting through deep eutectic solvent addition

This study introduced two deep eutectic solvents, ChCl/oxalic acid (CO) and ChCl/ethylene glycol (CE), into a 34-day co-composting process of distillery sludge and distiller's grains waste to address challenges related to NH3 emissions. The addition of DES increased dissolved organic carbon by 68% to 92%, offering more utilizable carbon for microorganisms. SYTO9/PI staining and enzyme activity tests showed the CE group had higher bacterial activity and metabolic levels during the thermophilic phase than the control. Bacterial community analysis revealed that early dominance of Lactobacillus and Lysinibacillus in CE accelerated the onset of the thermophilic phase, reduced pile pH, and significantly decreased urease production by reducing Ureibacillus. Consequently, CE treatment substantially dropped NH3 emissions by 73% and nitrogen loss by 54%. Besides, CE fostered a more abundant functional microbial community during the cooling and maturation phases, enhancing deep degradation and humification of organic matter.

Tillage Long-Term Effects on Soil Organic Matter Humification and Humic Acids Structural Changes in Regosol Profiles Typical of an Arid Region

Tillage Long-Term Effects on Soil Organic Matter Humification and Humic Acids Structural Changes in Regosol Profiles Typical of an Arid Region

Change in the humus state of typical chernozem with various methods of tillage

Relevance. The article is devoted to the influence of various methods of tillage on the humus state of typical chernozem (Haplic Chernozems).Methods. Tillage options: plowing with a formation turnover (20–22 cm); combined processing (disking 8–10 cm + chisel 20–22 cm); surface treatment (disking) up to 8 cm; direct sowing. The object of the study was a typical powerful heavy loamy chernozem.Results. According to the results of the group and fractional composition of typical chernozem humus (regardless of the method of processing and the studied soil layer), the following patterns were established: the predominance of a group of humic acids (HA — 45–55% of organic carbon (Sorg.), a high proportion of humic acids associated with calcium (HA-2 — 29–41% of Sorg.), low content of non-hydrolyzable residue (NO — 29–36% of Sorg.), humate type of humus (Sgc:Sfk > 2), a very high degree of humification of organic matter (>4.5). With an increase in the depth of the arable layer (regardless of the method of tillage), there is an increase in Sgc, Sgc-2 and a decrease in carbon of humic acids free and associated with mobile oneand-a-half R2O3 (Sgc-1), carbon of humic acids associated with stable R2O3 (Sgc-3), and carbon of fulvic acids (Sfk). In the 0-20 cm layer, the predominance of Sgc-1 (5.5%) is noted, and their content decreases depending on the method of tillage in the series “combined (5.08%) → surface treatment → direct sowing (4.91)”. When applying an extreme degree of minimization (direct sowing) in a layer of 0–20 cm in relation to other methods of tillage, the largest amount of Sgk-2 is noted. The content of Sgk-3 and Sfk was highest with surface and combined treatment.

Bioorganic Mineral Fertilizer on the Basis of Black Manage, Phosphorite Raw Materials and Biopreparts of Microorganisms

This article presents the results of studies on the production of bioorganic mineral fertilizers by treating a mixture based on black manure and phosphorite raw materials with a solution that accelerates the humification of organic matter, binds molecular nitrogen and enriches it with physiologically active substances, as well as microorganisms that play an important role in soil fertility. Based on the results of the study, it was found that treatment of a mixture based on black manure and phosphorite raw materials with a solution containing beneficial microorganisms accelerates the humification of organic matter, increases the conversion of phosphorus and reduces the release of nitrogen and organic matter into the gas phase.

Insight into bacterial role attribution in dissolved organic matter humification during rice straw composting with microbial inoculation

This study aims to investigate the effect of microbial role distribution in microbial carbon pumps on dissolved organic matter (DOM) humification during rice straw composting with microbial inoculation. Three composting groups were designed, named CK (control), B4 (with Bacillus subtilis, OR058594) and Z1 (with Aspergillus fumigatus, AF202956.1). As a result of inoculation, the composition of microbial communities was changed, so that the microorganisms that promoted DOM humification were concentrated in the responders in the microbial carbon pump. DOM was divided into three components in three composting treatments: C1, C2 and C3. After inoculation with Bacillus subtilis, the C2 component was significantly affected, while after inoculation with Aspergillus fumigatus, the C3 component was significantly affected. The results of physicochemical factors affecting the transformation of DOM fluorescence components indicated that C1, C2 and C3 were related to the abundance of the cellulose-degrading enzyme-encoding gene GH7 in CK and B4 composting. However, the C2 was susceptible to organic matter in Z1 composting. This study explored the distribution of microbial communities from a new perspective, which provided new information for analyzing DOM humification and treating agricultural straws to achieve clean conditions for environmental friendliness.

Soil organic mater management – a decisive measure in climate change mitigation and adaptation

Global warming requires the implementation of both immediate and long-term mitigation and adaptation measures in agriculture, which is affected by greenhouse gas emissions through the use of practices from the industrial model arsenal of agricultural intensification (oversaturation of planting areas with arable crops and lack of crop rotations with a greater diversity of arable and successive crops; excessive tillage; irrigation; application of mineral fertilizers, especially nitrogen etc.). Data from the long-term field experiments at Research Institute of Field Crops ”Selecția” (Bălți, Republic of Moldova) are proving the dominance of mineralization over humification of soil organic matter with the emissions of CO2 and oxides of nitrogen in the atmosphere. Chernozem soils have a high potential for carbon sequestration and consequently for mitigation and adaptation to climate change. Sustainable and resilient management of soil organic matter is one of the key issues for the transition to a more sustainable agriculture, capable to supply ecosystem and social services.

Supraglacial Soils and Soil-Like Bodies: Diversity, Genesis, Functioning (Review)

In the 21st century, glaciers are percepted as a distinct biome that has taken on special significance in today’s world of retreating ice. Here we review the results of recent studies of organomineral formations on glaciers, their diversity, processes, functioning and the role in the biosphere. The question is raised about the possibility of involving supraglacial organomineral formations in the range of objects of soil science. We review the supraglacial zone as an area of soils and soil-like bodies, which biogeochemical processes affect the glacial biome and its surrounding landscapes. Interpretation of supraglacial organomineral formations from a soil scientist point of view revealed the following processes: accumulation and stabilization of organic matter (OM), its heterotrophic transformation, formation of dark-colored humified OM and accumulation of residual solid-phase products of functioning in situ, fine earth aggregation, and biochemical weathering. Among supraglacial formations, we distinguish pre-soils and soil-like bodies in ice and snow, metastable soil-like bodies on cryoconite and soils with microprofiles under moss communities on ice, as well as relatively stable soils with macroprofiles on fine-earth-detrital deposits with underlying glaciers and dead ice. Labile water-soluble OM, accumulated and transformed in supraglacial soils and soil-like bodies, has a significant impact on the periglacial zone, leading to the reservoir and priming effects. The studies of supraglacial organomineral systems are of fundamental importance for understanding the evolution of ecosystems on Earth as well as for modeling supraglacial formations of extraterrestrial bodies with a vast cryosphere. Supraglacial soil formation is also a model object for studying common soils under conditions of a constant external input of organic and mineral components, which contribution outside the glaciers is no less significant, but is masked by the polymineral substrate of soils and parent rocks.

Gas source of the Middle Jurassic Shaximiao Formation in the Zhongjiang large gas field of Western Sichuan Depression: Constraints from geochemical characteristics of light hydrocarbons

The Zhongjiang gas field is a typical large gas field in terrigenous strata of the Western Sichuan Depression. It remains debatable which member of the Upper Triassic Xujiahe Formation served as the source rocks and how significant the member contributed to the gas accumulations in the Zhongjiang gas field. In this study, we analyzed the essential characteristics of the Lower Jurassic source rocks and the geochemical features of light hydrocarbons in natural gas from the 2nd (T3x2) and 4th members (T3x4) of the Upper Triassic Xujiahe Formation (T3x), as well as the Middle Jurassic Shaximiao (J2s) and Qianfoya (J2q) formations. Based on this, we explored the sources of the natural gas in the Zhongjiang gas field and determined the natural gas migration patterns and their effects on the properties of light hydrocarbons in the natural gas. The results indicate that the Lower Jurassic lacustrine source rocks of the Zhongjiang gas field contain humic organic matter, with vitrinite reflectance (Ro) values ranging from 0.86% to 0.98%. Samples meeting the criterion for effective source rocks [total organic carbon (TOC) content ≥0.75%] exhibited an average TOC content of merely 1.02%, suggesting significantly lower hydrocarbon generation potential than source rocks in the underlying T3x, which show higher thermal maturity and TOC contents. For natural gas samples from T3x2, T3x4, J2s, and J2q reservoirs, their C5–7 iso-alkane content was significantly higher than their n-alkane content, and their methylcyclohexane (MCH) index ranged from 59.0% to 77.3%, indicating the predominance of methylcyclohexane in C7 light hydrocarbons. As indicated by the origin identification and gas-source correlation based on the geochemical features of light hydrocarbons, the natural gas in the Zhongjiang gas field is typical coal-derived gas. The gas from the primary pay zone of the Shaximiao Formation, with significantly high K1, (P2 + N2)/C7, and P3/C7 values, predominantly originated from the 5th member of the T3x and migrated in the free phase, with a small amount possibly sourced from the Lower Jurassic source rocks. The dissolution and adsorption during gas migration led to a decrease in the aromatic content in C6–7 light hydrocarbons and an increase in the iso-heptane values. Therefore, their effects must be considered when determining the gas origin and thermal maturity based on the aromatic content in C6–7 light hydrocarbons and iso-heptane values.

Studies on the Source and Phase Characteristics of Oil and Gas: Evidence from Hydrocarbon Geochemistry in the Pingbei Area of Xihu Sag, the East China Sea Shelf Basin, China

The Pingbei area is the main accumulation area of oil and gas in the Xihu Sag. The phase characteristics of oil and gas in this area are complex, and the understanding of their genesis is still unclear. In this paper, based upon discussions of crude oil and natural gas geochemical data, integrated with local geological features, we discuss the sources, migration, and phase state characteristics of oil and gas in the Pingbei area of the Xihu Sag. The study results show that the crude oil and natural gas in the Pingbei area are coal-derived and the oil and gas produced by the humic organic matter during the mature stage. The oil and gas source correlation showed that crude oil and natural gas have good affinity with the Eocene Pinghu Formation (PH) coal-bearing source rocks. Crude oil has the characteristics of near-source accumulation and short-distance migration while natural gas is supplied from a dual source: the coal-derived hydrocarbon rocks of PH in the deep part of the study area, supplemented by the coal-derived hydrocarbon rocks of PH on the bottom of the slope, and adjacent hydrocarbon-bearing sub sag. The distribution characteristics and geochemical migration indices of hydrocarbon show that the oil generated from the hydrocarbon source rocks of PH in the deep Pingbei area mainly migrates vertically along the fault connecting the reservoir and the source rocks to the trap, where it accumulates, while the natural gas exhibits deep and large faults that mainly migrate vertically, supplemented by its lateral migration along the composite transport system composed of faults and sandstone layers in the slope zone. The whole area presents the phase characteristics of “upper oil and lower gas, west oil and east gas”. The mechanisms of produced-exhausted and geochromatographic effects (PGE), as well as evaporative fractionation (EF) and phase-controlled migration fractionation (PMF), result in the obvious discrepancy of hydrocarbon’s properties on the vertical profiles.

Characteristics of Humic Acids in Drained Floodplain Soils in Temperate Climates: A Spectroscopic Study

This study aims to assess the characteristics of humic acids (HAs) in floodplain soils. HAs were isolated from the Fluvisols located out of the embankment in the riparian forest (unflooded riparian forest) and within the embankment (inter-embankment), in the area periodically flooded. HAs from these soils were examined for quantity, structure, and humification degree using extraction methods as well as elemental analysis, UV-Vis, FTIR, EPR, and 1HNMR spectroscopies. In the soils after drainage, a significant decrease in HAs has been observed compared to the periodically flooded areas. Obtained results showed that organic matter from periodically flooded soils is more humified and contains HAs with a more aromatic, lignin-like structure compared to the humus matter from unflooded Fluvisols. Humic acids from periodically flooded soil contained a lower amount of C and H compared to those isolated from unflooded soils located out of the embankment, which resulted in a less aliphatic or more aromatic character of their molecules. A higher H/C ratio of HAs from the Fluvisols after drainage exhibits more condensed aromatic ring or substituted ring structures in the molecules. Soils with organic matter with a higher humification index contained HAs with lower radical concentration values in comparison to soils with less humified organic matter. Results obtained show that in flooded areas with periodically reductive conditions, humic acids do not lose as many -OCH3 groups as in better oxidized soils and therefore exhibit a lignin-like aromatic structure. It has been proven that the formation and dynamics of HA transformation may vary due to the water regime in soils.