Aromatic Content Research Articles

The influence mechanism of bitumen components on its macroscopic and microscopic properties: Analysis based on polyphosphoric acid modification

In order to investigate the impact of bitumen components on its overall properties, various modified bitumen with 1.0 %PPA or 2.0 %SBS/SBR + 0.6 %PPA were prepared. The influence of PPA dosage on bitumen’s physical properties were evaluated, and the macroscopic and microscopic properties of each bitumen sample were characterized by DSR, BBR and atomic force microscopy observation. The components of bitumen were separated through SARA test, and the infrared spectroscopy of asphaltenes was further analyzed. The findings suggest a significant impact on bitumen with PPA incorporation, the elastic recovery properties of bitumen at high temperatures were enhanced due to a more stable colloidal structure was formed by the dispersion and interaction of macromolecular asphaltenes. However, the low-temperature rheological properties of bitumen were impaired by reason of a relatively reduced flowable lightweight component. Specifically, the large asphaltenes clusters were dispersed cause PPA reacted with the –OH bonds of alcohols in bitumen by phosphorylation. By modeling the correlation between bitumen component contents and its microscopic surface parameters, the asphaltenes decomposition was demonstrated to be an important factor on the microscopic morphology, which was also related to the content of saturates and aromatics. Thus, a method for deconstructing bitumen from a compositional perspective is proposed.

Catalytic pyrolysis of torrefied biomass with molecular sieve catalysts to produce hydrocarbon rich biocrude

AbstractThe downstream processing of biocrudes obtained from direct biomass pyrolysis poses significant challenges due to stability issues, necessitating costly upgrading for further coprocessing with refinery feeds. This study examines the impact of torrefaction pretreatment on pyrolysis product distribution and biocrude composition using sawdust (SD) and groundnut shell (GS) feeds. Torrefaction was conducted at varying temperatures (200, 250 and 300°C) for 30 min under different reactor conditions. Increasing the severity of torrefaction resulted in decreased biocrude yields with reduced water content and gas formation, particularly evident with GS. A torrefaction temperature of 250°C and 30 min of pretreatment yielded higher phenolics and hydrocarbons. This increase in phenolics can be attributed to lignin enrichment during torrefaction, which, in the presence of a catalyst, undergoes deoxygenation leading to hydrocarbon formation. The influence of feed particle size, whether in powder or pellet form, on biocrude yield and composition was found to be minimal. Catalytic pyrolysis of SD using molecular sieve catalysts yielded the highest hydrocarbon (42%) and aromatic content (44%) at catalyst to biomass ratios of 1:1 and 2:3. The combination of torrefaction and pyrolysis was shown to enhance the quality of biocrude by increasing its hydrocarbon content, but at the expense of lower liquid yields. Experimental observations were supported by statistical analysis tools such as principal component analysis, which assessed pyrolysis product yields and composition.

Recent Advances in Sample Preparation and Chromatographic/Mass Spectrometric Techniques for Detecting Polycyclic Aromatic Hydrocarbons in Edible Oils: 2010 to Present.

Polycyclic aromatic hydrocarbons are considered to be potentially genotoxic and carcinogenic to humans. For non-smoking populations, food is the main source of polycyclic aromatic hydrocarbons exposure. Due to their lipophilic nature, oils and fats rank among the food items with the highest polycyclic aromatic hydrocarbon content. Consequently, the detection of polycyclic aromatic hydrocarbons in edible oils is critical for the promotion of human health. This paper reviews sample pretreatment methods, such as liquid-phase-based extraction methods, adsorbent-based extraction methods, and the QuEChERS (quick, easy, cheap, effective, rugged, and safe) method, combined with detection techniques like mass spectrometry and chromatography-based techniques for accurate quantification of polycyclic aromatic hydrocarbons in edible oils since 2010. An overview on the advances of the methods discussed herein, along with a commentary addition of current challenges and prospects, will guide researchers to focus on developing more effective detection methods and control measures to reduce the potential risks and hazards posed by polycyclic aromatic hydrocarbons.

Artificial neural network modelling of natural gas dehydration process

A multi-input–multi-output artificial neuron network (MIMO-ANN) model has been developed for process monitoring and improvement on a natural gas glycol dehydration process. The MIMO-ANN model was based on a steady-state process simulation model constructed in commercial software Aspen HYSYS. A set of training data was generated with the converged simulation model for the training of the MIMO-ANN model in Python. The process input of the model includes lean glycol recirculation rate and purity along with wet gas inlet pressure. On the other hand, the process output considered includes dehydrated gas water and aromatics content, dehydrated gas hydrate formation temperature and water dew point, stripping gas flow rate as well as reboiler duty. The overall mean squared error (MSE) of the MIMO-ANN model was calculated as 1.79. The best-fit line that highly overlaps with a 45° diagonal line is constructed with a correlation coefficient (R2) score of more than 0.999 for all studied process output testing datasets. The mean absolute percentage error (MAPE) of the predicted outputs is generally less than 1%, except for dehydrated gas water dew point (16.63%) and stripping gas flow rate (11.55%), due to error predictions attempted on pseudo-zero values. This successfully displays an exceptional predictive performance of the MIMO-ANN model developed in this work which can be further deployed as an online dashboard for real-time monitoring tool.

Characterization and bio-oil analysis of microalgae and waste tires by microwave catalytic co-pyrolysis

Waste tires (WT) are difficult to degrade in natural conditions, but co-pyrolysis with other substances can release environmental pressure. Thus, microwave catalytic co-pyrolysis of WT and Chlorella vulgaris (CV) were studied. The effects of material mixing ratio, catalysts (NiO, CoO and CeO) and their addition amounts (5%, 10%, 15% and 20%) on the co-pyrolysis were analyzed. The results showed that bio-oil yield was boosted by co-pyrolysis and the maximum value (19.77%) appeared at C6W4 (CV:WT = 6:4). While adding 15%NiO, the maximum yield of bio-oil increased by 8.66%. Compared with CV pyrolysis alone, the deoxidation rate, denitrification rate, and desulfurization rate of C6W4 were as high as 44.57%, 59.82% and 52.59%, respectively. Catalysts improved the quality of bio-oil, the highest hydrocarbon content (58.3%) and denitrification rate (27.07%) were obtained at the 15%NiO. The highest aromatic hydrocarbon content (33.2%) and deoxygenation rate (10.31%) appeared in 15%CoO.

One-pot synthesis of Fe modified lignin biochar for ex-situ catalytic fast pyrolysis of enzymatic hydrolysis lignin to promote the generation of aromatic hydrocarbons

The utilization of waste lignin to produce bio-oil rich in aromatics aromatic hydrocarbons is promising and attractive for a wide range of applications. Fe-modified lignin biochar (xFe/ALC) prepared using a one-step method was utilized as catalysts to investigate their impact on product distribution, aromatic hydrocarbon generation, and pathways during ex-situ catalytic fast pyrolysis of enzymatic hydrolysis lignin. The results revealed that the addition of Fe enhanced the production of gas products such as H2, while decreasing bio-oil yield. The lowest bio-oil yield, at 12.10 wt%, was observed at a Fe loading of 25 wt%, however the relative content of aromatic hydrocarbons reached a maximum value of 16.24 area%. Compared to the pyrolysis of lignin alone, their contents increased by 2.46 times, with the content of monocyclic aromatic hydrocarbons (toluene, ethylbenzene, styrene, xylene) increasing by 1.5–3.8 times. Spent 25Fe/ALC had good stability on the production of aromatic hydrocarbons. Compared with non-catalytic pyrolysis of lignin, the aromatic hydrocarbons content for spent 25Fe/ALC after four cycles increased by 26.70%.

Production of monocyclic aromatic hydrocarbons by the catalytic pyrolysis of Moso bamboo at different ages and parts using Zn and Cr modified zeolite catalysts

Monocyclic aromatic hydrocarbons (MAHs) are important organic building blocks for the chemical industry, which can be produced by catalytic pyrolysis of biomass. The wide application of bamboo in Chinese industry generates a large amount of bamboo waste which can be utilized as the feedstock to produce MAHs. This study aimed to investigate the effect of bamboo age and bamboo part on the yield of the aromatics by using the Cr and Zn modified HZSM-5 as catalyst. The result showed that the incorporation of metals (Cr and Zn) enhanced the catalytic performance, and the incorporation of Zn was better than Cr. The highest MAHs content (38.67%) and total aromatic content (57.42%) were obtained with the catalyst of 3% Zn/HZSM-5 catalyst at temperature of 400 °C and duration time of 30 min. Younger age (1-year-old bamboo) and the outer skin of bamboo was better for the production of MAHs. This study provided a high value-added application approach for the waste Moso bamboo.

Product regulation and kinetics for fast pyrolysis of corncob over niobium oxide modified zeolite

Catalytic fast pyrolysis is considered as a promising technology for converting biomass into biofuels. In the present research, a series of NbOx modified ZSM-5 catalysts were developed and applied for the selective fast pyrolysis of corncob into aromatics. Depolymerization and hydrodeoxygenation of lignin constituents as well as the aromatization of polysaccharide fractions were the major source of aromatics. The introduction of niobium oxide into ZSM-5 remarkably enriched the Lewis acids and improved the porous structures. The presence of synergistic effect between acid sites and porous structure of NbOx modified ZSM-5 contributed to the aromatics formation in a certain degree. Under the catalysis of 3Nb/ZSM-5, the optimum aromatic content was 86.4 % at 450 °C with a heating rate of 104 °C/s. In the meantime, 3Nb/ZSM-5 presented good stability and recyclability in the fast pyrolysis of corncob, and over 75 % aromatics was achieved even after 3 cycles. Kinetical study revealed that the Ea value for corncob pyrolysis could be lowered to ∼ 250 kJ/mol with conversion rate range of 0.4–0.7.

The Significance of Processing Techniques on the Quality of Smoked African Cat Fish (Clarias gariepinus) Using Different Energy Sources

There is unavoidable need for fish smoking as a preservative technique to reduce rampant post harvest losses in the tropical Africa. However the imperative of healthier and quality smoked products through improved processing method were however investigated. Organoleptic and chemical assessment of African catfish collected from a reputable fish farm in Ogbomoso, Oyo state Nigeria was carried out. Eviscerated and non-eviserated fish samples were smoked using four different smoke sources: Gmelina (Gmnelina arborea), Parkia (Parkia biglobosa), Neem (Azadirachita indica) and charcoal. Overall acceptability was based on 5-point Hedonic scale (excellent (5) - poor (1). Chemical test was on Polycyclic Aromatic Hydrocarbon contents (benzo(a)pyrene, Fluoranthene, Napthalene, Acenapthalene, Chrysene and Benzo(ghi) perylene). Data were subjected to one way Analysis of Variance (ANOVA) using general linear mode (GLM) of Factorial Experimental Design and means were separated by Duncan’s multiple range tests (P<0.05). Non- eviscerated smoked African catfish samples had lower scores for colour than eviscerated smoked samples for energy sources used. Eviscerated samples had mean scores of 4.64, 3.91, 3.36 and 2.82 for charcoal, Gmelina, Neem and Parkia smoked samples respectively, much better than scores of 4.36, 2.46, 2.36 and 2.27 obtained for non-eviscerated samples. Total concentrations of polycyclic aromatic hydrocarbons (PAH) were highest in samples produced using Gmelina as smoke source and Neem for eviscerated (15.25 µg/kg) and non-eviscerated (29.43 µg/kg) samples respectively. Evisceration of fish prior to smoking enhances its sensory characteristics however; concentrations of PAHs for both eviscerated and non-eviscerated fish samples were within the recommended international standard limit.

Steam gasification of lime dried sewage sludge: Effects of temperature and addition of lime

Gasification shows great potential as an alternative method for energy utilization from sewage sludge. Lime (CaO) is a cheap and commonly used dewatering conditioner for sewage sludge. The calcium hydroxide (Ca(OH)2) generated during the drying process with lime can enhance the pH level of the sludge, thereby providing disinfection properties. This paper investigated enhancement mechanism of Ca(OH)2 on hydrogen gas generation and the effect on gas product yield during the steam gasification process of lime-dried sludge. The experiments were conducted in an electrically heated reactor at 500–800 °C. The forms of calcium present in the gasified sludge char samples were analyzed using X-ray diffraction (XRD) analysis to investigate their transformation process. Fourier transform infrared spectroscopy (FTIR) was utilized to obtain information regarding the chemical structure in the gasified sludge char samples, with the aim of exploring the mechanism behind hydrogen production from lime-dried sludge. The results indicate that the CaO generated from Ca(OH)2 dehydration acts both CO2 adsorbent and catalyst during the gasification process. The addition of Ca(OH)2 during the sewage sludge gasification process leads to a reduction in the aromatic CH content in the organic matter, while significantly increasing the content of reactive CH3-chains. It also promotes the ring-opening and rearrangement reactions of aromatic hydrocarbons and nitrogen-containing heterocycles and steam reforming reaction of tar. The combined effects of these factors contribute to an overall increase in hydrogen gas yield.

Characterization and mechanism elucidation of high-quality bio-oil production from co-pyrolysis of waste low-rank coal fines and de-oiled microalgae biomass using bimetallic (Cu-Cr) ZSM-5 catalyst

The present study provides a cleaner co-pyrolysis strategy for high-quality bio-oil production by utilizing low-cost residues such as low-rank coal (CL), de-oiled microalgae (ALG), and their blends (CLALG). The heavy metal-loaded Cu-Cr-ZSM-5 catalyst is synthesized by using ion-exchange method and investigated in the CL, ALG and CLALG pyrolysis bio-oil upgradation at different catalyst feed ratios (0.5:1, 1:1, 2:1). The synthesized catalyst was characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and brunauer-emmett-teller (BET) analysis. The synthesized catalyst is nano-crystalline of average size 7 nm. The microstructure of the synthesized catalyst shows stacked nanorods packing with connected intercrystal and intracrystal mesopores. The catalytic and non-catalytic pyrolysis of CL, ALG and CLALG are performed at 600 °C, 10 °C/min for 60 min. The non-catalytic ALG pyrolysis has shown maximum bio-oil yield (35.7%). The synergistic effect of nanorod morphology, active acid sites and excess mesoporosity of catalyst facilitates efficient deoxygenation, denitrogenation and aromatization of pyrolysis bio-oil with oxygen content from 2.1⎼3.1%, nitrogen content 3.5⎼5.1% and aromatic content 49.4⎼54.4% at catalyst feed ratio of 1:1. The maximum obtained higher heating value (HHV) of bio-oil from catalytic pyrolysis of CL (40.1 MJ/kg) followed by CLALG (38.6 MJ/kg) and ALG (36.5 MJ/kg) is very close to diesel oil with HHV (42⎼46 MJ/kg). Further, a co-pyrolysis mechanism is proposed to systematically investigate possible catalytic action sites to yield high-quality bio-oil. Thus, outcomes of the present study enrich information regarding catalyst development, catalyst feed interaction, and thermocatalytic cracking as emerging efforts towards industrial-scale upgradation of bio-oil to engine fuels.

A quantitative investigation on pyrolysis behaviors of metal ion-exchanged coal macerals by interpretable machine learning algorithms

Generalizing the rules from complex processes such as catalytic pyrolysis to guide their process control is always a difficult but attractive task. The influences of ion-exchange of metal ions (Na+, K+, Ca2+, Mg2+, Co2+ and Ni2+) on the pyrolysis behavior of vitrinite and inertinite from Shendong coal were investigated by thermogravimetric analyzer-Fourier transform infrared spectrometer (TG-FTIR), fixed-bed reactor (FBR), gas chromatograph-mass spectrometer (GC-MS) and X-ray diffractometer (XRD). A set of machine learning models was successfully constructed based on random forest, support vector machine, and Gaussian process regression, to quantify the relationships between pyrolysis behaviors and the properties of metals and macerals. The leave-one-out-cross validation showed that there are considerable determination coefficients (R2 > 0.9) between predicted and experimental values for most responses (17 out of 29). By combining genetic programming-based symbolic regression with the black-box algorithm, 23 symbolic regression expressions with high confidence were successfully constructed. This work is a pioneering attempt of optimization in small-scale experiments. By utilizing the highly interpretable models, a demand-orientated (multi-)optimization coal pyrolysis can be achieved. The bi-objective optimization was conducted on the yield of tar and the content of light aromatics in tar, and the results show that Co is the optimal loading metal.

A novel coal purification-combustion system: Product and efficiency of coal purification process

A novel coal purification-combustion technology is presented to realize the efficient and clean utilization of coal under carbon peaking and carbon neutrality goals. Central to this technology is the implementation of a purification process, the product characteristics, and energy properties of which are the focus of this study. An experimental test of coal purification was conducted using Shenmu coal. The results demonstrate increased coal reactivity following the moderate temperature activation (MTA) process. The high temperature reduction (HTR) phase promotes the production of higher amounts of amorphous carbon, reduces aromatic carbon content, and further decreases fuel particle size. The composite combustion characteristic index(S) of the purified fuel reaches its peak when the excess air coefficient of secondary air (λ2) is 0.36. As λ2 increases from 0.1 to 0.36, the energy in the gas product of the purification system increases from 13700 kJ/kg coal to 25351 kJ/kg coal, while exergy increases from 6530 kJ/kg coal to 11030 kJ/kg coal. The energy efficiency of the purification process ranges from 74.74 % to 80.88 %, with exergy efficiency varying between 60.51 % and 70 %. These findings offer significant insights into refining the coal purification process, ultimately contributing towards maximizing the utility of coal resources.

Catalytic upgrading of Naomaohu coal pyrolysis volatiles over NiAl and NiLiAl oxides

Catalytic upgrading of volatiles is an essential technology to improve the product distribution of pyrolysis for the clean and efficient utilization of low-rank coals. In this work, novel acid-base bifunctional catalysts composed of Ni/Li/Al oxides were designed and prepared using LDH precursors with tunable chemical composition and structural properties. The catalysts were systematically characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), physisorption, NH3-temperature programmed desorption (NH3-TPD), CO2-temperature programmed desorption (CO2-TPD), H2-temperature programmed reduction (H2-TPR), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). A two-stage fixed bed reactor was employed to evaluate the performance of the catalysts. Characterization results suggest that the crystal size of NiO and the surface area of the catalyst decreased with increasing Li content and decreasing Ni content in the catalyst, while the pore volume and pore diameter were positively correlated with Li content. Moreover, the addition of Li reduced the amount of weak acid sites and raised the amount of total basic sites. Consequently, the bifunctional catalysts boosted the yield of light tar and the contents of aromatics and phenols in tar. Specifically, with the highest total acid sites (569 μmol/g) promoting the cracking of heavy pitch components, Ni2.5Li0.5Al1 decreased the content of pitch in tar to 23.8 wt%, representing a 42.7 % drop from the corresponding non-catalytic pyrolysis. Accordingly, it improved the light tar yield to 7.2 wt%, which was 18 % higher than non-catalytic pyrolysis. 450 °C is identified as a suitable temperature for the catalytic upgrading of volatiles from Naomaohu coal; higher catalysis temperatures at 500 °C and 550 °C led to lower tar yield and lower phenols content, along with higher gas yield and more carbon deposition.

Enhanced Aquathermolysis of Water-Heavy Oil-Ethanol Catalyzed by B@Zn(II)L at Low Temperature.

In order to study the synergistic effects of exogenous catalysts and in situ minerals in the reservoir during heavy oil aquathermolysis, in this paper, a series of simple supported transition metal complexes were prepared using sodium citrate, chloride salts and bentonite, and their catalytic viscosity reduction performances for heavy oil were investigated. Bentonite complex catalyst marked as B@Zn(II)L appears to be the most effective complex. B@Zn(II)L was characterized by scanning electron microscopy (SEM), Fourier-Transform Infrared (FTIR) spectroscopy, thermo-gravimetric analysis (TGA) and N2 adsorption-desorption isotherms. Under optimized conditions, the viscosity of the heavy oil was decreased by 88.3%. The reaction temperature was reduced by about 70 °C compared with the traditional reaction. The results of the group composition analysis and the elemental content of the heavy oil indicate that the resin and asphaltene content decreases, and the saturated and aromatic HC content increases. The results of TGA and DSC of the heavy oil show that the macromolecular substances in the heavy oil were cracked into small molecules with low boiling points by the reaction. GC-MS examination of water-soluble polar compounds post-reaction indicates that B@Zn(II)L can diminish the quantity of polar substances in heavy oil and lower the aromatic nature of these compounds. Thiophene and quinoline were utilized as model compounds to investigate the reaction mechanism. GC-MS analysis revealed that C-C, C-N and C-S bonds were cleaved during the reaction, leading to a decrease in the viscosity of heavy oil.

Study on H3PO4-activated carbon catalytic co-pyrolysis of bamboo and LDPE to poly-generation syngas and aromatics at low temperature

Biomass-derived carbon activated by H3PO4 was adopted to catalytic co-pyrolysis of bamboo and low-density polyethylene (LDPE) to produce syngas and aromatics on a fixed bed reactor. Effects of LDPE ratio in the feedstock, catalytic co-pyrolysis temperature and ratio of catalyst to feedstock on the yields and compositions of the products were investigated. The increase of LDPE ratio in liquid first improved and then reduced the relative content of aromatics, while it showed a positive effect on the yield and the H2/CO ratio of gas. 500℃ was an optimum temperature, under which the relative content of aromatics in liquid kept higher, meanwhile, avoided the undesirable polymerization reactions of monocyclic aromatics. At the same time, the content of H2 in gas reached a maximum (59.3%), which was in favor of poly-generation. H3PO4-activated carbon catalyst (H3PO4-ACC) with abundant functional groups on surface catalyzed cracking, hydrodeoxygenation, cyclization and aromatization reactions so as to facilitate the generation of aromatics. Non-condensable gas was dry reformed on P-ACC at the expense of CO2, CH4 and CO to generate char and H2. When the reaction condition was at a LDPE ratio of 50%, a catalyst/feedstock ratio of 2:1 and at 500℃, the relative content of aromatics in liqiud was 81.65% and the proportion of syngas component in gas was 79.73%. The volume ratio of H2/CO approached to 3:1 in gas under this condition. H3PO4-ACC catalytic co-pyrolysis of bamboo and LDPE could obtain high quality gas and liquid products at a relative low reaction temperature, which provided a new research idea on high-value application of biomass and waste plastics.

Changes in factor profiles deriving from photochemical losses of volatile organic compounds: Insight from daytime and nighttime positive matrix factorization analyses

Substantial effects of photochemical reaction losses of volatile organic compounds (VOCs) on factor profiles can be investigated by comparing the differences between daytime and nighttime dispersion-normalized VOC data resolved profiles. Hourly speciated VOC data measured in Shijiazhuang, China from May to September 2021 were used to conduct study. The mean VOC concentration in the daytime and at nighttime were 32.8 and 36.0 ppbv, respectively. Alkanes and aromatics concentrations in the daytime (12.9 and 3.08 ppbv) were lower than nighttime (15.5 and 3.63 ppbv), whereas that of alkenes showed the opposite tendency. The concentration differences between daytime and nighttime for alkynes and halogenated hydrocarbons were uniformly small. The reactivities of the dominant species in factor profiles for gasoline emissions, natural gas and diesel vehicles, and liquefied petroleum gas were relatively low and their profiles were less affected by photochemical losses. Photochemical losses produced a substantial impact on the profiles of solvent use, petrochemical industry emissions, combustion sources, and biogenic emissions where the dominant species in these factor profiles had high reactivities. Although the profile of biogenic emissions was substantially affected by photochemical loss of isoprene, the low emissions at nighttime also had an important impact on its profile. Chemical losses of highly active VOC species substantially reduced their concentrations in apportioned factor profiles. This study results were consistent with the analytical results obtained through initial concentration estimation, suggesting that the initial concentration estimation could be the most effective currently available method for the source analyses of active VOCs although with uncertainty.

Large-scale soil application of hydrochar: Reducing its polycyclic aromatic hydrocarbon content and toxicity by heating

The beneficial roles of hydrochar in carbon sequestration and soil improvement are widely accepted. Despite few available reports regarding polycyclic aromatic hydrocarbons (PAHs) generated during preparation, their potential negative impacts on ecosystems remain a concern. A heating treatment method was employed in this study for rapidly removing PAHs and reducing the toxicity of corn stover-based hydrochar (CHC). The result showed total PAHs content (∑PAH) decreased and then sharply increased within the temperature range from 150 °C to 400 °C. The ∑PAH and related toxicity in CHC decreased by more than 80% under 200 °C heating temperature, compared with those in the untreated sample, representing the lowest microbial toxicity. Benzo(a)pyrene produced a significant influence on the ecological toxicity of the hydrochar among the 16 types of PAHs. The impact of thermal treatment on the composition, content, and toxicity of PAHs was significantly influenced by the adsorption, migration, and desorption of PAHs within hydrochar pores, as well as the disintegration and aggregation of large molecular polymers. The combination of hydrochar with carbonized waste heat and exhaust gas collection could be a promising method to efficiently and affordably reduce hydrochar ecological toxicity.

Quantification of microbial community assembly processes during degradation on diverse plastispheres based on physicochemical characters and phylogenetic bin-based null model analysis

To understand the differences in degradation processes depending on the chemical properties of polymers, it is necessary to both quantify the microbiome composition and evaluate the process of microbial turnover (i.e., community assembly processes) in a variety of polymer materials. In this study, using a phylogenetic bin-based null model analysis (i.e., iCAMP), we evaluated community assembly processes from original estuary water to 37 types of polymers, which provide overwhelmingly diverse niches for microbes, in 14-day incubation experiments. First, we evaluated the polymer properties related to degradation rates. Polymers with higher adipic acid (AdA) monomer exhibited higher motility, hydrophilicity, and degradation rates, whereas those with higher aromatic monomer exhibited the opposite trends. Second, microbiome composition analysis was performed, and the microbiomes were significantly changed by the AdA or aromatic content. This was consistent with the polymer properties, suggesting that polymer motility and hydrophilicity attributable to the first-order structure modify the accessibility of the enzyme to the reaction site and hence the degradation rate, resulting in differences in microbiome community composition. Finally, we determined community assembly processes from estuary water to plastics using a phylogenetic bin-based null model analysis. The importance of heterogeneous selection was higher in mobile, hydrophilic, and fast-degrading polymers, while that of homogeneous selection was lower. This suggests that the environmental difference between before and after incubation becomes significant under rapid degradation, which select microbes adapted to biofilm environments. In addition, the more stochastic turnover prevailed, the more variation in the communities (i.e., β-diversity) increased. This suggests that turnover processes not dictated by the environment lead to instability in community compositions.

Shifting Mountain Tree Line Increases Soil Organic Carbon Stability Regardless of Land Use.

Climate and land use changes are causing trees line to shift up into mountain meadows. The effect of this vegetation change on the partitioning of soil carbon (C) between the labile particulate organic matter (POM-C) and stable mineral-associated organic matter (MAOM-C) pools is poorly understood. Therefore, we assessed these C pools in a 10 cm topsoil layer along forest-meadow ecotones with different land uses (reserve and pasture) in the Northwest Caucasus of Russia using the size fractionation technique (POM 0.053-2.00 mm, MAOM < 0.053 mm). Potential drivers included the amount of C input from aboveground grass biomass (AGB) and forest litter (litter quantity) and their C/N ratios, aromatic compound content (litter quality), and soil texture. For both land uses, the POM-C pool showed no clear patterns of change along forest-meadow ecotones, while the MAOM-C pool increased steadily from meadow to forest. Regardless of land use, the POM-C/MAOM-C ratio decreased threefold from meadow to forest in line with decreasing grass AGB (R2 = 0.75 and 0.29 for reserve and pasture) and increasing clay content (R2 = 0.63 and 0.36 for reserve and pasture). In pastures, an additional negative relationship was found with respect to plant litter aromaticity (R2 = 0.48). Therefore, shifting the mountain tree line in temperate climates could have a positive effect on conserving soil C stocks by increasing the proportion of stable C pools.