Heavy Fraction Research Articles

Liquid-liquid equilibrium of CO2/bitumen and CO2/bitumen/ethyl acetate systems with application to diluted bitumen transportation

Bitumen transportation by pipelines requires dilution with solvents. These diluents are often expensive. Therefore, the utilization of liquid CO2 as a diluent to reduce or eliminate diluent consumption is of interest. However, there is limited data in the literature on the liquid-liquid equilibrium (LLE) of CO2 and bitumen. In this work, we report a new set of LLE data for MacKay River bitumen and liquid CO2 at ambient temperature. First, the LLE of bitumen/CO2 at various CO2 feed concentrations was studied. The density of light and heavy liquid phases, the viscosity of the heavy phase, and the heavy phase volume fraction were measured. It was shown that a CO2 feed concentration of 30 wt% is optimum for achieving maximum dissolution of CO2 in bitumen. Then, the effect of pressure on the LLE of bitumen/CO2 at a 30 wt% CO2 concentration was studied. The results revealed a significant reduction in bitumen viscosity from 300,000–1250 cP could be achieved at 21 °C. The results suggest that liquid CO2 can be utilized to reduce diluent consumption in pipeline transportation. The role of ethyl acetate (EA) as a co-solvent with CO2 was also examined. It was shown that the addition of EA to a mixture of bitumen/CO2 could further reduce the bitumen viscosity to satisfy the pipeline transportation criterion. The results reveal that CO2-assisted bitumen transportation in Canada can lead to the utilization of 0.16 Mt of CO2 daily, which is equivalent to a utilization potential of about 80 kg CO2/bbl of raw bitumen. The results also suggest a 73% reduction in fossil-based diluent usage, equivalent to ∼0.5 million barrels of crude oil.

Molecular Characterization of Hydrocarbons in Petroleum by Ultrahigh-Resolution Mass Spectrometry

The progress in ultrahigh-resolution mass spectrometry (UHRMS) and related technologies has significantly promoted the development of petroleomics. The study of petroleomics has greatly broadened our knowledge of the composition of petroleum at the molecular level, especially heavy fractions that cannot be analyzed by gas chromatography (GC)-based methods. To date, heteroatom-containing (O, N, S, and metal atoms) compounds in petroleum have been studied extensively by UHRMS. Nevertheless, the main components of petroleum, hydrocarbon compounds, have remained out of reach of petroleomics characterization for a long time because they are too difficult to be softly and efficiently ionized for UHRMS analysis. It is undoubtedly the case that petroleum hydrocarbons should not be the missing part of petroleomics characterization since they play important roles not only as feeding pools for various high value-added petroleum products but also as critical biomarkers for geochemistry studies. Here, the most recent breakthroughs in petroleomics characterization of hydrocarbon compounds using UHRMS rather than conventional methods have been reviewed. Innovations of soft ionization methods can transform non-polar hydrocarbon molecules into molecular ions or quasi-molecular ions that are reachable for UHRMS without fragmentation. The development of data processing methods has assisted the decoding of the complicated UHRMS data to visualize the molecular composition and structure of hydrocarbon compounds. These advances make it possible to see the whole picture of petroleum compositions, from light distillation fractions to heavy distillation fractions, and from small volatile molecules to large non-volatile ones. The applications of UHRMS-based methods for petroleomics characterization of hydrocarbon compounds in crude oils and various petroleum samples including fuel oil, slurry, and even asphaltene have made a great contribution to petrochemistry and geochemistry studies, especially in the fields of molecular refining and biomarker discovery.

Response of soil organic carbon and its fractions to natural vegetation restoration in a tropical karst area, southwest China

The dynamics of soil organic carbon (SOC) and its fractions are important for evaluating the vegetation restoration effect and carbon cycle of the ecosystem. Here, SOC fractions, including light fraction organic carbon (LFOC), heavy fraction organic carbon (HFOC), and labile organic carbon (LOC) fractions (including water-soluble organic carbon, WSOC, readily oxidizable organic carbon, ROC, particulate organic carbon, POC, and microbial biomass carbon, MBC), were investigated at four soil depths under five restoration stages in a tropical karst area in southwest China. This study showed that the content of SOC and its fractions significantly increased with vegetation restoration and decreased with increasing soil depth at each restoration stage (p < 0.05). Additionally, LFOC was more sensitive to vegetation restoration, whereas HFOC was the main storage form of SOC. The LOC fractions in the surface soil layer were significantly higher than those in the lower, and the percentages of some LOC fractions (POC/SOC and MBC/SOC) significantly decreased with increasing soil depth, indicating that SOC was more stable in the lower layer than in the surface layer. Correlation analysis showed that SOC was significantly and positively correlated with its fractions. Moreover, SOC and its fraction were positively correlated with soil chemical factors (TN, TP, AP, AK, ECa, EMg, NH4+-N, and NO3–-N) and negatively correlated with bulk density (BD) at a significant level (p < 0.05). Moreover, redundancy analysis showed that the 12 soil physicochemical factors explained 70.99% of the variation in SOC and its fractions, with AK, NH4+-N, and BD being the main factors, explaining 19.38, 17.24, and 10.52% of the variation, respectively. The structural equation mode analysis showed that soil properties, above-ground biomass, and litterfall explained most of the variation in SOC (59%), LFOC (79%), HFOC (81%), and LOC (61%). Soil properties and above-ground biomass significantly affected SOC, LFOC, and HFOC content mainly through indirect effects, while the total phosphorus content of the litterfall could directly and significantly affect SOC, LFOC, and HFOC content. NH4+-N and AK of soil factors had direct effects on LFOC and LOC accumulation, respectively. This study provides a valuable perspective for estimating carbon sink potential and constructing carbon sink models in karst areas.

The deasphalting of heavy crude oil by silicone oil is a green method of removing heavy compounds and producing bitumen

Deasphalting of heavy crude oil (HCO) with silicone oil (SO), which is immiscible with the crude oil and extracts light compounds from it, has been carried out for the first time. The yield of the extracted light fraction increases linearly with increasing SO/HCO ratio from 0.5/1 to 10/1 and then reaches a constant level of about 50%. An analysis of the composition and properties of the precipitated heavy fractions showed that they are enriched with asphaltenes and resins but contain admixtures of saturated and aromatic compounds. Compared with the original crude oil, the heavy fractions have a higher viscosity that correlates with sulfur concentration and tends to become higher as the SO/HCO ratio increases. Moreover, the viscoelastic properties of the heavy fractions are similar to those of bitumen binders, allowing their potential use in road construction. In this case, SO/HCO ratios of 15/1 and 25/1 make it possible to produce bitumens as a byproduct that meet existing standards for binder's viscosity and thermal stability. A comparative evaluation of energy consumption has shown the advantage of silicone oil usage for deasphalting of heavy oil in comparison to usual solvent deasphalting with volatile and environmentally unfriendly aliphatic hydrocarbons.

Structural characterization and transformation of nitrogen compounds in waste tire pyrolysis oils

The waste tire pyrolysis oil (WTPO) has been widely concerned because it's a promising recycling method of waste tires. However, the high content of nitrogen in WTPO is unfavorable to its application. In this work, nitrogen compounds in the full distillation range of a waste tire pyrolysis oil were characterized by gas chromatograph-nitrogen chemiluminescence detector (GC–NCD), gas chromatograph-mass spectrometry (GC–MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). In the gasoline fraction of WTPO, the most abundant nitrogen compounds were benzonitrile, aniline and small molecule nitriles. In the diesel fraction of WTPO, the most abundant nitrogen compounds were benzothiazole, quinoline derivatives, p-phthalodinitrile, benzonitrile derivatives, hexadecanenitrile and octadecanenitrile. In the heavy fraction of WTPO, significant amounts of NxOy (x = 2–3 and y = 1–2) species were discovered after the separation of solvent dissolution and solid phase extraction. The molecular structures of these NxOy species were determined as amide derivatives of diphenylamine by tandem mass spectra of FT-ICR MS. Therefore, the origin of nitriles in the light fractions of WTPO was suspected as the pyrolysis of these amides in the heavy fractions. Finally, the nitrogen transformation during the pyrolysis of waste tires was suggested based on the results of quantum chemistry simulations. These results would be helpful for the treatment and removal of these undesirable nitrogen compounds in WTPO.

Effect of molecular distillation on the anti-inflammatory activity and neurotoxicity of Asarum essential oil.

Asarum essential oil (AEO) has been shown to have good pharmacological activities for the anti-inflammatory and analgesic effects, but increasing the dose may cause toxicity. Therefore, we studied the toxic and pharmacodynamic components of AEO by molecular distillation (MD). Anti-inflammatory activity was assessed using RAW264.7 cells. Neurotoxicity was assessed in PC12 cells and the overall toxicity of AEO was evaluated in the mouse acute toxicity assay. The results showed that AEO is primarily composed of safrole, methyl eugenol, and 3,5-dimethoxytoluene. After MD, three fractions were obtained and contained different proportions of volatile compounds relative to the original oil. The heavy fraction had high concentrations of safrole and methyl eugenol, while the light fraction contained high concentrations of α-pinene and β- pinene. The original oil and all three fractions exhibited anti-inflammatory effects, but the light fraction demonstrated more excellent anti-inflammatory activity than the other fractions. Asarum virgin oil and MD products are all neurotoxic. The exposure of PC12 cells to high concentrations of AEO resulted in abnormal nuclei, an increased number of apoptotic cells, increased ROS formation, and decreased SOD levels. Moreover, the results of acute toxicity tests in mice revealed that the light fractions were less toxic than virgin oils and other fractions. In summary, the data suggest that the MD technology enables the enrichment and separation of essential oil components and contributes to the selection of safe concentrations of AEO.

Iron oxidation coupled with nitrate reduction affects the acetate-assimilating microbial community structure elucidated by stable isotope probing in flooded paddy soil

Acetate is an abundant carbon source that can trigger microbial redox processes in anoxic environments, thereby affecting the microbial community structure, function, and associated element cycling. Here, we investigated the acetate-assimilating microbial community, especially the key microorganisms involved in nitrate-dependent Fe(II) oxidation that are closely associated with soil redox processes in flooded soil. In the present study, DNA-stable isotope probing (DNA-SIP) with labeled acetate (13C) as a carbon source was applied to examine the acetate-assimilating communities associated with nitrate-dependent Fe(II) oxidation. The results showed that NO3− was rapidly reduced in the treatments with NO3− and NO3− + Fe(II). Fe(II) oxidation occurred quickly only in the presence of NO3−. In the treatments with acetate only, the predominant 13C-labeled genera such as Geobacter, Azospira, Azospirillum, Ideonella, and Desulfovibrionia were probably involved in acetate oxidation coupled with the redox processes of NO3−, Fe(III) and SO42− reduction, which are the most important electron acceptors in flooded soils. The addition of NO3− and Fe(II) significantly affected the acetate-assimilating microbial community from the original soil. The enriched genera in 13C heavy fractions were associated with Pseudogulbenkiania, Azospira, Zoogloea, Azoarcus, and Bdellovibrio dominated in the treatments with NO3− and Fe(II). In the treatments with NO3− only, Zoogloea, Azospira, Azoarcus, and Geothrix were the dominant genera. Given the different genera with enrichments in 13C-heavy fractions in different treatments, Zoogloea and Pseudogulbenkiania were identified as key microorganisms associated with NO3− reduction and nitrate-dependent Fe(II) oxidation, respectively. These findings suggest the importance of Zoogloea and Pseudogulbenkiania for C, Fe, and N biogeochemistry and indicate that Fe and N cycling have a great impact on soil biogeochemistry processes.

EXPERIENCE IN OBTAINING PRODUCTS OF THE DELAYED COKING PROCESS USING VISBREAKING RESIDUE AND CATALYTIC CRACKING HEAVY GAS OIL AS FEEDSTOCK

The authors have analyzed the literature data on delayed coking process. There have been considered the following: feedstock bases for petroleum coke production; implementation and development of delayed coking process; the types of products obtained. It has been revealed, that the main feedstocks for the process are heavy fractions of oil: fuel oil, semihudron, tar, various heavy oil residues, etc.In order to expand the feedstock base, the authors conducted laboratory studies concerning the use of visbreaking residue and catalytic cracking heavy gas oil in the coking process. During the research: raw materials (visbreaking residue and catalytic cracking heavy gas oil) were analyzed; the coking process was carried out; the results of obtaining petroleum coke from visbreaking residue and catalytic cracking heavy gas oil were compared.It has been proved that visbreaking residue and catalytic cracking heavy gas oil can be involved in the process of delayed coking. It has been revealed that the best option for obtaining coking products is precisely catalytic cracking heavy gas oil.

Interactive Effects Determine Radiocarbon Abundance in Soil Fractions of Global Biomes

Soil organic carbon (SOC) is heterogeneous, consisting of fractions with differing turnover rates. Climate, vegetation, and soil properties can all affect the characteristics of these different soil carbon fractions. However, there has been little investigation into the interactive effects of biotic and abiotic drivers on a large spatial scale. In this study, we utilized data from the international soil radiocarbon database (ISRaD) to investigate the radiocarbon abundance (an indicator of carbon persistence) in soil fractions from several different biomes. Bulk SOC was categorized into three fractions according to the density fractionation method: a free light fraction (fLF), an occluded light fraction (oLF) and a heavy fraction (HF). In addition to the impacts of significant factors such as depth and climate, interactive effects between soil fractions and environmental factors on radiocarbon abundance were prevalent. Specifically, there were significant interactions between climate, vegetation types, soil properties, and soil fractions affecting Δ14C levels. The difference in Δ14C of the shallow depth fractions was significant in the temperate forest, and was not significant in the boreal and tropical forests. The interactive effect between mean annual temperature (MAT) and mean annual precipitation (MAP) on Δ14C was significant in the shallower depth (i.e., 0–30 cm and 30–60 cm) of the oLF and in the deeper soils (i.e., 30–60 cm and 60–100 cm) of the HF. Soil properties also interact with soil fractions in determining Δ14C. After accounting for depth effect, oxalate-extractable aluminum (Alo) accounted for 63.5% of the remaining Δ14C variation in the fLF and accounted for 35.9% of the remaining Δ14C variation in the oLF. Rather than Alo, cation exchange capacity (CEC) accounted for 46.1% of the remaining Δ14C variation in the HF. These findings suggest that the way the interactions between climate, vegetation, and soil properties affect soil carbon persistence at various fractional depths is critical for the accurate prediction of soil carbon dynamics.

Ferrocene-based catalysts for in-situ hydrothermal upgrading of heavy crude oil: Synthesis and application

In this work, the effect of synthesized Ferrocene-based ligand catalysts, including Mono-, Di- and Tri-Ferrocene, as additives for promoting the catalytic in-situ hydrothermal upgrading of Tatarstan (Russia) heavy crude oil was studied. In addition, the changes in composition of upgraded oil samples as well as the in-situ transformation and characteristics of used catalysts were evaluated in detail using comprehensive analyzing techniques. All of the catalytic and non-catalytic hydrothermal upgrading experiments were carried out under the steam stimulation conditions at 300 °C, 72 bar (1044.27 psi) and 24 h of reaction time. The results show that introducing Ferrocene-based ligand catalysts to the upgrading system promotes the in-situ upgrading of heavy crude oil and improves the physical and chemical properties of upgraded oil samples. The maximum viscosity reduction was observed in presence Tri-Ferrocene and reached around 40% compared to non-catalytic hydrothermal upgrading. In addition, the upgrading performance also reflects in increase of H/C ratio, reduction of sulfur content, increase of saturates and aromatics, and decrease of the content of resins and asphaltenes as well as a noticeable change (increase) in the light fractions of C10-C20 are observed for all upgraded oil samples. Mono-Ferrocene as an oil-soluble catalyst mainly transformed to the particles of Fe3O4 (Magnetite) and FeS, which can act as active forms of catalysts and accelerate the hydrothermal conversion of heavy crude oil and its heavy fractions including resins and asphaltenes. These transformations were confirmed using XRD, SEM-EDX and Mössbauer analyzing techniques. Generally, the good catalytic performance of used ferrocene-based ligand catalysts as well as their low cost and commercial availability makes them great potential catalysts for improving the efficiency of steam injection for heavy oil production and in-situ upgrading.

Facile transformation of heavy oil residues into carbon composites used for high-performance supercapacitors

Asphaltene, an otherwise undesirable waste from the oil industry, was refined from heavy oil fractions and processed under different conditions to obtain carbonaceous materials with large surface area to be used in supercapacitors. Carbon electrode materials were successfully fabricated by a facile thermal process using melamine foam as template and KOH activation. The effect of different synthesis parameters on morphological and electrochemical performance is reported, namely, the weight ratio KOH:asphaltene, homogenization time, temperature and duration of thermal treatment. The materials were characterized by Raman, BET, SEM/EDS, and XPS; and their performance, in terms of specific capacitance and stability, was assessed by different electrochemical methodologies. Results show that an optimized material, using specific capacitance and active material recovery as optimization targets, was obtained by using a KOH: asphaltene weight ratio of (3:1), homogenization time of 1 h and thermal treatment at 700°C for 0.5 h. This material had a specific energy of 8.6 W h kg−1, specific power of 645 W kg−1 and a specific capacitance of 112 F g−1 at 0.4 A g−1 current density.

Applying synchronous fluorescence spectroscopy combined with Gaussian band fitting and two-dimensional correlation to characterize interactions of copper (II) with dissolved organic matter from urban river sediments

Dissolved organic matter (DOM) and heavy metals can form strong complexes, which might determine distribution, toxicity, bioavailability, and environmental trend of heavy metals in aquatic environment. Synchronous fluorescence spectroscopy combined with Gaussian band fitting and two-dimensional correlation (2DCOS) was applied to characterize Cu2+ interactions with DOM fractions from sediments in Xihe River. DOM from four layers was mainly associated with tyrosine-like (TYLF), tryptophan-like (TRLF), microbial humic-like (MHLF), fulvic-like (FLF), and humic-like fluorescence (HLF) substances based on Gaussian band fitting. At the first layer, the f value of FLF was the highest among five components, while TRLF at the second and third layers represented the highest f values. Besides, at the fourth layer, the f value of TYLF was the highest. According to 2DCOS and moving window 2DCOS, the decreasing binding sensitivities were HLF→MHLF→TYLF→TRLF→FLF in the first layer, which almost represented high efficiencies at 40 μM Cu2+. The binding order was MHLF→HLF→FLF→TRLF→TYLF in the second layer, where TYLF and TRLF shared the identical efficiencies at 120 μM Cu2+. For the third layer, the varying order was TYLF→FLF→TRLF→MHLF→HLF, whose high efficiencies occurred at 10 μM Cu2+. In the fourth layer, the order was TYLF→FLF→MHLF→TRLF→HLF, whose efficiencies almost covered whole titrate concentrations. At a given layer, structural equation model showed Cu2+ concentration negatively affected the fluorescence intensity of DOM components except FLF at the substrate layer. This study might provide an effective method to illustrate the interaction mechanism of the heavy metals and DOM fractions.

The high ventricular function in the shortfin mako shark (Isurus oxyrinchus)

The shortfin mako sharks ( Isurus oxyrinchus) belongs to the family Lamnidae, which is a group of high performance regional endothermic elasmobranch fishes that has metabolic rates (47.4±8 ml/kg/min) higher than ectothermic elasmobranchs, and also rivals that of mammals. As in all elasmobranchs, the mako sharks do not possess direct cardiac sympathetic innervation to elevate cardiac performance, but it still retains an ancient design of a capacious semi-rigid pericardium (5.4±0.6 ml/kg) likely to accommodate its large atrial diastolic volume. This study test the hypothesis that the increase in cardiac output in the mako is influenced by a strong positive lusitrophic effect that serves to increase stroke volume, which in turn invokes the Frank-Starling’s effects. The objectives is to show differences in the physiology and biochemical properties between mako (Is) and an ectothermic blue shark ( Prioance glauca, Pg), both are oceanic species and share similar life history. Echocardiography showed a higher early to late filling velocity ratio (p=0.036) in the Is (0.92±0.16, [n=15]) than in Pg (0.45±0.04, [9]). The early time velocity integral is also greater in Is (8.8±2.4 cm, [15]) vs Pg (6.8±0.8 cm [9]) indicating a stronger conduit filling imparted by the energy from previous systole in Is. However, basal cAMP (Is: 31±12 [7] vs Pg: 31±1 [3] fmol/min/μg) and stimulated cAMP with isoproterenol+GTPγS (Is: 65±21 [7] vs Pg: 59±7 [3] fmol/min/μg) activity are similar in both groups. This suggests that the differences in ventricular contractility are not through the classic adrenergic signaling pathway involving adenylyl cyclases, but likely through the mechanical stretching of the myofibrils from diastole. Caveolin distribution of the ventricular tissues following sucrose density gradient shows a higher degree of Caveolin-1/3 in the buoyant fraction and little in the in the heavy fraction in both shark species indicating an absence of t-tubules. However, Is shows a remarkably high amount of buoyant Cav-1/3 fraction compared to Pg. We posit that the high fraction abundance of Cav-1/3 provides a gateway for corticotropin-releasing factor, such as urotensin I or possibly an ancestral precursor of urocortin, which has been shown to elevate heart function in mammals. The study is supported by NSF IBN93-16621. No disclosure. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Controlling Diels-Alder reactions in catalytic pyrolysis of sawdust and polypropylene by coupling CO2 atmosphere and Fe-modified zeolite for enhanced light aromatics production

Producing value-added light aromatics (BTEX) from solid waste streams holds excellent promise for resource recovery. Here we present a thermochemical conversion approach that enhanced BTEX production by coupling CO2 atmosphere and Fe-modified HZSM-5 zeolite to facilitate the Diels-Alder reactions in catalytic pyrolysis of sawdust and polypropylene. The Diels-Alder reactions between sawdust-derived furans and polypropylene-derived olefins could be controlled by tuning CO2 concentration and Fe loading amount. Sufficient CO2 (≥50%) with moderate Fe loading (10 wt%) were observed to produce more BTEX and fewer heavy fractions (C9+aromatics). To deepen the mechanistic understanding, quantification of polycyclic aromatic hydrocarbons (PAHs) and catalyst coke was further conducted. The co-use of CO2 atmosphere and Fe modification suppressed the appearance of low-, medium-, and high-membered ring PAHs by over 40%, decreased pyrolysis oil toxicity from 42.1 to 12.8 μg/goil TEQ, and transformed coke from "hard" to "soft". Based on the characterization of CO2 adsorption behavior, it was deduced that the introduced CO2 was activated by loaded Fe and reacted in situ with H2 generated during aromatization to expedite H-transfer. Meanwhile, BTEX recondensation was prevented through the Boudouard reactions of CO2 and water-gas reactions between the resulting water and carbon deposits. These synergistically enhanced the production of BTEX and suppressed the formation of heavy species, including PAHs and catalyst coke.

Changes in structural parameters of SARA fractions during heavy oil hydrocracking using dispersed catalysts

Most of the characterization of SARA fractions of heavy crude oils during hydrocracking reactions is focused only on asphaltenes, and scarce works are devoted to analyze the differences in the structural parameters of all SARA fractions. In this work, a heavy crude oil is upgraded by non-catalytic and catalytic hydrocracking in a batch reactor at low severity conditions (3.9 MPa H2 pressure, 380 °C temperature, 800 rpm stirring rate, and 4 h reaction time). Three ore catalysts (hematite, magnetite and molybdenite) and one analytical grade catalyst (iron oxide) are employed. After reaction, the upgraded oils are first distilled and then separated into SARA fractions by the ASTM D86-16a and ASTM D2007-11 methods, respectively. NMR (1H and 13C), FTIR and GPC analyses are used to characterize SARA fractions before and after hydrocracking. The hydrocracking products exhibited a reduction in the average molecular weight of all SARA fractions as function of the hydrogenation capacity of each catalyst in the following order: Fe2O3 (analytical grade) > Molybdenite > Hematite > Magnetite. The structural parameters of saturates fraction remains unchanged except for the production of small length aliphatic chains from heavier fractions. For aromatics, resins and asphaltenes fractions, the number of aliphatic carbons is reduced due to dealkylation reactions increasing their aromaticity. For resins and asphaltenes fractions, hydrogenation and ring opening reactions are also carried out. Mo-based catalyst is mainly aimed at the conversion of asphaltenes, while the Fe-based catalysts focused on the conversion of resins.

THERMAL PROPERTIES OF COBALT AND MOLYBDENUM CONTAINING CITRATE SYSTEMS

Citrate complexes of transition metals, namely cobalt and molybdenum, used as active components in the synthesis of catalytic systems supported on alumina for hydrotreatment of heavy oil fractions have been studied. Cobalt nitrate hexahydrate and polyoxomolybdate (molybdenum blue) obtained by mechanical activation of molybdenum disulphide (MoS2) powder were used as initial compounds. Thermogravimetric analysis of the samples was carried out during their heating from 25 to 750°C at a rate of 15°C/min in air. Thermogravimetric analysis shows that the order in which the active components are introduced significantly affects the thermal stability of the sample. Despite the general similarity of the profiles, a shift of the temperature range of citrate complex decomposition is observed, depending on the order of active components introduction. Presumably, this may be due to the different degrees of Mo and Co availability for the formation of compounds with citrate ligands. It is shown that the most thermally stable system is the one in which the Co-containing component and citric acid are introduced first, and then the alcohol solution of molybdenum blue; the least stable system is the reverse one, in which the alcohol solution of molybdenum blue is introduced first, then citric acid and the Co-containing component are added.

A tropical soil (Lixisol) identified in the northernmost part of the Mediterranean (Istria, Croatia)

Terra rossa soils on the Istrian peninsula are generally considered polygenetic relict soils. They overlie and mark the youngest subaerial unconformity in the northwestern part of the Adriatic Carbonate Platform and are susceptible to erosional and redepositional processes. Terra rossa soils represent a valuable archive of information that can be used to understand present and past soil formation processes in the context of climate variability and landscape dynamics, especially in low-lying parts of the karst landscape where thicker deposits are typically found. We studied a 3 m thick terra rossa profile in a karst depression on the northernmost part of the southwestern Istrian planation surface and analysed the micromorphology, physical/chemical properties, geochemistry, bulk and clay mineralogy, and composition of heavy and light mineral fractions. The profile shows several signs of colluviation and polygenesis with clay distribution along the profile, clearly indicating lithic discontinuities. Kaolinisation, along with iron oxide formation, is the dominant process in the studied profile. Ferralitisation and lessivage processes were diagnosed throughout the profile, with intense clay translocation occurring despite the extremely stable soil microaggregates. In accordance with the WRB system, the profile is classified as Rhodic Lixisol (Clayic, Aric, Cutanic). This implies that some terra rossa soils, previously classified as e.g. Cambisols or Luvisols, might actually be Lixisols or other (sub-)tropical soils (e.g. Nitisols), in which relict properties are preserved in the present climate. The finding of a Lixisol in the study area indicates the old age of the surface of the karst depression and provides the first data on the burial history of the southwestern Istrian planation surface. We suggest the older Quaternary interglacials, the mid-Piacenzian Warm Period (Pliocene) and the Miocene Climatic Optimum as favourable periods for the formation of the studied soil.

Copper and cadmium co-contamination affects soil bacterial taxonomic and functional attributes in paddy soils

Microorganisms inhabiting heavy metal-contaminated soils have evolved specific metabolic capabilities to survive, which has the potential for effective bioremediation. However, the ecological consequence of copper (Cu) and cadmium (Cd) on bacterial taxonomic and functional attributes of rice field remains unclear. Here, we selected paddy soils along a polluted river in southern China to evaluate the role of Cu and Cd contaminant fractions in regulating bacterial co-occurrence patterns. We also assessed the effects of these heavy metal fractions on the relative abundance of functional genes using shotgun metagenomic analysis. Soil Cu and Cd concentrations in paddy soils gradually decreased from upstream to downstream of the river, and had a greater impact on bacterial communities and metabolic potentials than soil general properties. Soil Cu and Cd contamination led to drastic changes in the cumulative relative abundance of ecological modules in bacterial co-occurrence networks. Bacteria associated with AD3, HSB_OF53–F07 (both belonging to Chloroflexi), Rokubacteriales, and Nitrospira were identified as tolerant to Cu and Cd contamination. The Cu and Cd contaminant fractions were positively correlated with the genes involved in metal resistance, carbon (C) fixation, nitrification, and denitrification, but negatively correlated with the genes related to nitrogen (N) fixation. These results indicated that soil Cu and Cd pollution not only enriched metal resistant genes, but also affected genes related to microbial C and N cycling. This is critical for facilitating microbiome bioremediation of metal-contaminated paddy soils.

Identification of diverse antibiotic resistant bacteria in agricultural soil with H218O stable isotope probing combined with high-throughput sequencing

BackgroundWe aimed to identify bacteria able to grow in the presence of several antibiotics including the ultra-broad-spectrum antibiotic meropenem in a British agricultural soil by combining DNA stable isotope probing (SIP) with high throughput sequencing. Soil was incubated with cefotaxime, meropenem, ciprofloxacin and trimethoprim in 18O-water. Metagenomes and the V4 region of the 16S rRNA gene from the labelled “heavy” and the unlabelled “light” SIP fractions were sequenced.ResultsAn increase of the 16S rRNA copy numbers in the “heavy” fractions of the treatments with 18O-water compared with their controls was detected. The treatments resulted in differences in the community composition of bacteria. Members of the phyla Acidobacteriota (formally Acidobacteria) were highly abundant after two days of incubation with antibiotics. Pseudomonadota (formally Proteobacteria) including Stenotrophomonas were prominent after four days of incubation. Furthermore, a metagenome-assembled genome (MAG-1) from the genus Stenotrophomonas (90.7% complete) was retrieved from the heavy fraction. Finally, 11 antimicrobial resistance genes (ARGs) were identified in the unbinned-assembled heavy fractions, and 10 ARGs were identified in MAG-1. In comparison, only two ARGs from the unbinned-assembled light fractions were identified.ConclusionsThe results indicate that both non-pathogenic soil-dwelling bacteria as well as potential clinical pathogens are present in this agricultural soil and several ARGs were identified from the labelled communities, but it is still unclear if horizontal gene transfer between these groups can occur.

Soil aggregate variation in two contrasting rice straw recycling systems for paddy soil amendment over two years

ABSTRACT Soil aggregate is important to soil quality. Straw return is beneficial for soil amendment, but the effects of straw and straw-derived biochar on aggregate formation and stability in paddy soil are unclear. This study carried out a field experiment for 2 years in Northeast China with four treatments: conventional fertilization (CF), straw (ST, 7.5 t ha−1 year−1), biochar (BC, 2.5 t ha−1 year−1), and biochar-based fertilizer (BCF, 0.75 t ha−1 year−1). Compared with the CF and BCF, BC and ST improved the macroaggregates and significantly increased soil total carbon and aggregate organic carbon, indicating a sustained positive role in promoting the formation and stability of aggregates. BC significantly improved aggregate stability. Correlation analysis showed that macroaggregates (2–0.25 mm) can be increased by increasing the heavy fraction organic carbon (HFOC), BC and ST significantly increased the HFOC, and BC had a greater effect. Scanning electron microscopy (SEM) showed that the combination of biochar and soil particles can be captured with strong water scouring. BCF showed an increasing trend in the formation and stability of soil aggregates. In comparison, biochar had a greater effect on promoting the formation of macroaggregates and the stability of soil aggregates with a significant sustainable effect.