Benzene Polycarboxylic Acids Research Articles

Ruthenium ion catalytic oxidation depolymerization of lignite under ultra-low dosage of RuCl3 catalyst and separation of the organic products with inorganic salts.

Depolymerization of lignite into valuable chemicals via ruthenium ion catalytic oxidation (RICO) is a potential route for the non-energy utilization of lignite. However, the high cost of the Ru catalyst during depolymerization and the high content of inorganic salts in the product solution limit the development of this route. In this work, RICO depolymerization of lignite was conducted under an ultra-low dosage of RuCl3 catalyst to decrease the usage of the catalyst during the RICO process. Different approaches were attempted to fulfill the separation of benzene polycarboxylic acids (BPCAs) products with the inorganic salts derived from the oxidant NaIO4, including butanone extraction and desalting via crystallization under different temperatures. The results show that lignite can be efficiently depolymerized under the mass ratio of RuCl3/lignite as low as 1/1000 by prolonging the reaction time without decreasing the depolymerization degree and BPCAs yields compared to the commonly used mass ratio of 1/10. Butanone can extract ca. 91% of the total BPCAs in the product solution, and the inorganic salts content (mainly NaIO3) in the extraction solution was as low as 0.19 mg mL-1. A new strategy of first acidification of depolymerization aqueous solution by HCl and then extraction by butanone is proved to be efficient for the separation of BPCAs with inorganic salts. Salting out via crystallization under lower temperature can remove ca. half content of the salts, and the efficiency is inferior to butanone extraction. The low usage of RuCl3 can efficiently decrease the catalyst cost of the RICO process, and butanone extraction can fulfill the enrichment of BPCAs and the separation of BPCAs with inorganic salts. This work is meaningful for the potential application of RCIO depolymerization of lignite for the production of valuable chemicals.

Hybrid water adsorption and solubility partitioning for aerosol hygroscopicity and droplet growth

Abstract. In this work, we studied the cloud condensation nuclei (CCN) activity and subsaturated droplet growth of phthalic acid (PTA), isophthalic acid, (IPTA) and terephthalic acid (TPTA), significant benzene polycarboxylic acids and structural isomers found in the atmosphere. Köhler theory (KT) can be effectively applied for hygroscopicity analysis of PTA due to its higher aqueous solubility compared to IPTA and TPTA. As with other hygroscopicity studies of partially water-soluble and effectively water-insoluble species, the supersaturated and subsaturated hygroscopicity derived from KT principles do not agree. To address the disparities in the sub- and supersaturated droplet growth, we developed a new analytical framework called the Hybrid Activity Model (HAM). HAM incorporates the aqueous solubility of a solute within an adsorption-based activation framework. Frenkel–Halsey–Hill (FHH) adsorption theory (FHH-AT) was combined with the aqueous solubility of the compound to develop HAM. Analysis from HAM was validated using laboratory measurements of pure PTA, IPTA, TPTA and PTA–IPTA internal mixtures. Furthermore, the results generated using HAM were tested against traditional KT and FHH-AT to compare their water uptake predictive capabilities. A single hygroscopicity parameter was also developed based on the HAM framework. Results show that the HAM-based hygroscopicity parameter can successfully simulate the water uptake behavior of the pure and internally mixed samples. Results indicate that the HAM framework may be applied to atmospheric aerosols of varying chemical structures and aqueous solubility.

Structural evolution of lignite from heterogeneous particles to homogeneous products during ruthenium ion catalytic oxidation depolymerization

Disclosing the structure evolution of lignite from heterogeneous particles to homogeneous products during depolymerization is of great significance to understand the depolymerization process of lignite. In this work, the structure evolution of lignite during ruthenium ion catalytic oxidation (RICO) depolymerization was studied. Special attention was paid on the changes of the size of lignite particles and molecular weight of the soluble products. The results showed that the depolymerization of lignite into benzene polycarboxylic acids (BPCAs) involved the conversion of lignite from microparticles into nanoparticles, which can be further depolymerized and released the soluble products into the solution. Around 93% of the organic matter in lignite can be converted from heterogeneous particles to homogeneous products. The molecular weight of the soluble products had a wide distribution from dozens of thousand Dalton to several hundred Dalton, indicating that the macromolecules released from lignite particles were gradually decomposed and formed a series of intermediate products. These results explain that why the composition of the depolymerization products is complex. Finally, the microstructural evolution process of lignite during depolymerization was speculated. Lignite particles mainly experienced the microparticles, nanoparticles, macromolecules, and then small molecules such as BPCAs. The formation of macromolecules proceeded fast and the subsequent formation of BPCAs from macromolecules was the rate-determining step. This work contributes deep insights into the structural evolution process of lignite during RICO depolymerization, and provides basic data for the regulation and control of the depolymerization process.

Embedding of biochar in soil mineral fractions: Evidence from benzene polycarboxylic acids molecular biomarkers

Investigators are debating on the positive and negative priming effects of biochar on native soil organic carbon (SOC), which is largely attributed to the technical barrier of identifying biochar contribution to the apparently measured SOC or mineralized CO2. We combined benzene polycarboxylic acids (BPCAs) molecular biomarkers and soil particle density fractionation to identify biochar contributions to the carbon content in three representative allitic soils in Yunnan. The soil-biochar mixture was incubated for one-month to avoid significant biodegradation of biochar. The results showed that BPCAs were mainly distributed in free light fractions (fLF) up to 87 % of the total BPCAs contents after one month incubation. Recognition of BPCAs in occluded light fractions (oLF) and heavy fractions (HF) suggested a significant interaction between biochar and soil mineral particles. In addition, the percentage of B6CA is comparable or even higher in HF than in fLF or oLF. Thus, biochar-mineral interactions may be an additional stabilization mechanism besides the condensed aromatic structures in biochar. The apparently measured carbon contents increased after biochar application, and both positive and negative priming effects to native SOC were observed after deducting biochar contents based an accurate calculation from BPCAs. The most native SOC depletion (positive priming effects) was noted for the soil with the most favored biochar embedding in soil mineral compositions. This study emphasized that combining BPCAs molecular biomarkers and soil particle density fractionation could accurately quantify different carbon pools, and thus facilitate a comprehensive understanding on the stabilization and turnover of biochar in soils.

Identification of thermal signature and quantification of charcoal in soil using differential scanning calorimetry and benzene polycarboxylic acid (BPCA) markers

Abstract. Black carbon (BC) plays an important role in terrestrial carbon storage and can sustainably improve soil fertility. However, the accurate quantification of BC remains critical to fully unravelling the functions and dynamics of BC in soil. In this study, we explored the potential of differential scanning calorimetry (DSC) to identify, characterize and quantify charcoal in the soil of pre-industrial charcoal kiln sites from various forest and cropland areas in Belgium and Germany. Pre-industrial charcoals and uncharred soil organic matter (SOM) demonstrated a distinct thermal signature that could be used to distinguish between them, with charcoal being more thermally stable than SOM. The DSC pattern of charcoals was characterized by one to three specific exothermic peaks, varying in size and position depending on soil conditions. Our data suggest that the thermal moieties within charcoal depend on the strength of chemical bonds of C atoms (increasing with the degree of aromatic condensation and decreasing with weathering) and on the activation energy required to initiate combustion. Despite the specific thermal features of charcoal, its decomposition spans a wide range of temperatures that overlaps with the thermal signature of uncharred SOM. This stresses the challenge of BC quantification in soil and hinders the use of cut-off temperatures to accurately quantify charcoal in soil. Therefore, charcoal-C content was estimated from the relative height of exothermic peaks, attributed either to the combustion of charcoal or SOM. For a selection of 45 soil samples, charcoal-C content estimated by DSC was compared to benzene polycarboxylic acid (BPCA) abundance, a widely used method to quantify BC in soil. The two methods correlated strongly (R2=0.97), with BPCA C representing about one-fifth of DSC-derived charcoal C. This reinforces the view that operationally defined BC content has an absolute quantitative value only if the recovery rate is controlled, which is very complicated for many case studies. Overall, our results demonstrate that dynamic thermal analysis is largely under-exploited despite providing quantitatively interpretable information across the continuum of SOM.

Measuring dissolved black carbon in water via aqueous, inorganic, high-performance liquid chromatography of benzenepolycarboxylic acid (BPCA) molecular markers.

Dissolved black carbon (DBC) is the condensed aromatic portion of dissolved organic matter produced from the incomplete combustion of biomass and other thermogenic processes. DBC quantification facilitates the examination of the production, accumulation, cycling, transformation, and effects of biologically recalcitrant condensed aromatic carbon in aquatic environments. Due to the heterogeneous nature of DBC molecules, concentrations are difficult to measure directly. Here, the method for DBC quantification consists of oxidizing condensed aromatic carbon to benzenepolycarboxylic acids (BPCAs), which are used as proxies for the assessment of DBC in the original sample. The concentrations of oxidation products (BPCAs) are quantified using high-performance liquid chromatography. DBC concentrations are determined from the concentration of BPCAs using a previously established conversion factor. Details and full descriptions of the preparative and analytical procedures and techniques of the BPCA method are usually omitted for brevity in published method sections and method-specific papers. With this step-by-step protocol, we aim to clarify the steps of DBC analysis, especially for those adopting or conducting the BPCA method for the first time.

Comparative study on the relative significance of low-/high-condensation aromatic moieties in biochar to organic contaminant sorption

Aromatic moieties of biochar are considered as key components for immobilizing hydrophobic organic contaminants in the environment. However, the relative importance of different aromatic moieties such as low-/high-condensation components in sorption has not been comprehensively investigated. In this study, biochar was produced from flue-cured tobacco straw (TB) and pine wood sawdust (WB) at various pyrolysis temperatures (200–600 °C). Aromatic moieties were characterized via elemental analysis, Fourier transform infrared spectroscopy, Raman spectroscopy, and benzene polycarboxylic acid molecular markers (BPCAs). The significance of different aromatic moieties in the sorption of phenanthrene (PHE) and bisphenol A (BPA) was assessed based on the individual BPCA patterns. The results indicated that aromaticity and aromatic moiety contents increased with increasing pyrolysis temperature. Biochar at 200 °C produced lower mellitic acid (B6CA) contents (18.7–27.9%) than the others. When the pyrolysis temperature was increased to 600 °C, the B6CA contents representing high-condensation aromatic moieties accounted for 55.4–60.9% of all the aromatic moieties. The unitary linear regressions between the individual BPCA distribution patterns and the n values and log Kd suggested that the high-condensation aromatic moieties played a more significant role than the low-condensation aromatic moieties (represented by B3CA–B5CA) in facilitating sorption nonlinearity (for PHE and BPA) and sorption capacity (for PHE). The elevated sorption of PHE can be attributed to the increased specific surface area and hydrophobicity of the newly formed aromatic moieties. Hydrogen bonds and π–π electron–donor–acceptor were the main mechanisms of BPA sorption. Because the WB biochar contained more aromatic moieties and more O-containing groups on the surface of the TB biochar, the WB exhibited a higher sorption for PHE; however, slightly elevated sorption was observed on the TB for BPA. This research may provide a new perspective in understanding the behavior of biochar aromatic moieties in sorption of organic contaminants.

Alkaline earth metal ions mediated coordination separation of valuable organic acids from depolymerization products of lignite

Oxidative depolymerization of lignite to produce valuable organic acids such as benzene polycarboxylic acids (BPCAs) is a potential route to achieve non-energy and value-added utilization of lignite. However, due to the complexity of depolymerization products of lignite, the separation process becomes the bottleneck problem during the utilization of the depolymerization products, which limits seriously the development of this route. In this study, based on the coordination properties of carboxylic acids with metal ions, the coordination separation of BPCAs from depolymerization product mixture via the coordination of alkaline earth metal ions (Mg2+, Ca2+, Sr2+, and Ba2+) was proposed. The separation conditions including pH of the solution, the dosage of metal salts, reaction time, and temperature were studied. The results showed that the route was effective and different metal ions exhibited different separation behaviors towards BPCAs. Ca2+, Sr2+, and Ba2+ showed high selectivity to BPCAs with carboxylic groups ≥ 4 when the pH was around 8 (for Ca2+) or 6 (for Sr2+ and Ba2+). By comparing the influences of different factors, it was found that the pH value of the mother solution had significant influence on both separation yields and selectivity of BPCAs. The dosage of metal ions, reaction temperature and time mainly affected the separation yields with no obvious influence on the selectivity. The structures of the intermediate formed by BPCAs with metal ions were analyzed, and the results showed that BPCAs were separated out from the mixture via the coordination interaction between metal ions and the carboxylic groups in BPCAs. The metal ions could be reused for 3 times without obvious decrease in the efficiency. The separation process was carried out under near room temperature and used water as the solvent, which is mild and no need of using the organic solvents. The separation selectivity could be simply tuned by controlling the variety of metal ions and the pH of the solution. This work can provide basic data and technical reference for the separation of organic acids from depolymerization products of lignite.

The molecular markers provide complementary information for biochar characterization before and after HNO3/H2SO4 oxidation

Biochar inevitably goes through long-term aging under biotic and abiotic processes in the environment, which results in various changes in its physicochemical properties. However, the traditional characterization methods based on particle separation cannot effectively monitor biochar in complex matrixes. Molecular markers, especially benzene polycarboxylic acids (BPCAs), can be used to directly identify the source and properties of biochar. In this study, biochars were prepared using corn straw (CS) and pinewood (PW) and were oxidized with HNO3/H2SO4 to simulate the aging processes. Molecular markers of lignin-derived phenols showed that PW has more vanillyl unit and thus more stable than CS. The overall BPCAs content and the relative content of mellitic acid (B6CA) both increased with pyrolysis temperature, indicating increased aromatic condensation/aromaticity. The pristine CS biochar has a higher BPCAs content compared to PW biochar. HNO3/H2SO4 treatment greatly decreased the lignin components and more vanillyl and cinnamyl units were removed from CS biochar than PW biochar. In addition, BPCAs contents decreased by 41–60 mg/g for CS biochar, while increased by 86–133 mg/g for PW biochar after HNO3/H2SO4 oxidation. This is owing to the release of the condensed aromatic structures in CS biochars, but the concentration of the condensed aromatic structures in PW biochars after oxidation. These results showed that PW biochars are more stable than CS biochars. The application of the molecular markers can help understanding the dynamic change of biochar in the environment.

Anthropogenic fire fingerprints in Late Pleistocene and Holocene sediments of Sodmein Cave, Egypt

Sodmein Cave in Egypt is an exceptional archive for the study of past human behavior and anthropogenic fire history. Stratified remains of human occupation were excavated, ranging from the Middle Stone Age to the Neolithic. Hearths were repeatedly detected throughout the stratigraphy, with the lowest Pleistocene level having particularly large fire pits. This study is the first to apply a black carbon (BC) method on sediments bearing archaeology from the last 120,000 years. The method oxidizes BC to benzene polycarboxylic acids (BPCA) as a proxy for fire residue input. We detected significant changes in BC amounts throughout the stratigraphy; the highest contents in the form of two distinctive peaks were found in samples corresponding to the beginning of the Late Pleistocene (3.3 and 2.2 g BC kg−1, respectively), indicating frequent burning. In the overlying layers, BC remained low (on average: 0.2 g BC kg−1) until the beginning of the Holocene, when contents increased, and human influence became visible again (1.7 g BC kg−1). Also, BPCA composition as a proxy for changes in fire temperature changed significantly over the stratigraphy. In the Pleistocene, residues of hotter fires were predominantly found, while the Holocene was characterised by a change to low-temperature fires. Variations in BC input and source are in agreement with the archaeological results, demonstrating the varying intensities and recurrence of human visits to the shelter during the last 120,000 years, but also show the potential to resolve different phases of human occupation more finely, when the archaeological findings are accompanied by geochemical BC analyses.

Continental-scale measurements of soil pyrogenic carbon in Europe

Pyrogenic carbon (PyC), the product of incomplete biomass combustion, is a key component of soil organic carbon (SOC) because it can persist in soils for centuries to millennia. Quantifying PyC across large spatial scales remains a significant challenge in constraining the global carbon cycle. We measured PyC in topsoils across Europe using molecular marker (benzene polycarboxylic acids, BPCA) and spectroscopic techniques (Diffuse Reflectance Infrared Fourier Transform Spectroscopy, DRIFTS). We developed a calibration between BPCA and DRIFTS, but the calibration was less reliable (Y-variance explained = 0.62) than previous reports due to low soil PyC content and heterogeneity of soil matrices. Thus, we performed multiple regressions to identify drivers of PyC distribution using only the measured BPCA data. PyC content varied widely among soils, contributing 0–24% of SOC. Organic carbon was the strongest predictor of soil PyC content, but mean annual temperature, clay, and cation exchange capacity also emerged as predictors. PyC contributes a smaller proportion of SOC in European soils compared to other geographic regions. Comparing soil PyC measurements to PyC production rates in high latitude and Mediterranean regions suggests that transport, degradation, and recombustion are important mechanisms regulating soil PyC accumulation.

Polycyclic Aromatic Carbon: A Key Fraction Determining the Light Absorption Properties of Methanol-Soluble Brown Carbon of Open Biomass Burning Aerosols.

The composition and radiative forcing of light-absorbing brown carbon (BrC) aerosol remain poorly understood. Polycyclic aromatics (PAs) are BrC chromophores with fused benzene rings. Understanding the occurrence and significance of PAs in BrC is challenging due to a lack of standards for many PAs. In this study, we quantified polycyclic aromatic carbon (PAC), defined as the carbon of fused benzene rings, based on molecular markers (benzene polycarboxylic acids, BPCAs). Open biomass burning aerosols (OBBAs) of 22 rainforest plants were successively extracted with water and methanol for the analysis of water- and methanol-soluble PAC (WPAC and MPAC, respectively). PAC is an important fraction of water- and methanol-soluble organic carbon (WSOC and MSOC, respectively). WPAC/WSOC ranged from 0.03 to 0.18, and MPAC/MSOC was even higher (range: 0.16-0.80). The priority polycyclic aromatic hydrocarbons contributed less than 1% of MPAC. The mass absorption efficiency (MAE) of MSOC showed a strong linear correlation with MPAC/MSOC (r = 0.60-0.95, p < 0.01). The absorption Ångström exponent (AAE) of methanol-soluble BrC showed a strong linear correlation with the degree of aromatic condensation of MPAC, which was described by the average number of carboxylic groups of BPCA (r = -0.79, p < 0.01). This result suggested that PAC was a key fraction determining the light absorption properties (i.e., light absorptivity and wavelength dependence) of methanol-soluble BrC in OBBAs.

Protein Binding of a Novel Platinum-Based Anticancer Agent BP-C1 Containing a Lignin-Derived Polymeric Ligand

Platinum (Pt) antineoplastic agents remain indispensable for the treatment of oncological disease. Pt-based drugs are mainly used in the therapy of ovarian cancer and non-small-cell lung carcinoma. A novel platinum-containing antineoplastic agent BP-C1 is a complex of diamminoplatinum with an oxygen-donor polymeric ligand of benzene-polycarboxylic acids, isolated from natural lignin. The aim of the study was to investigate ex vivo protein binding of BP-C1. Protein binding of BP-C1 was tested using equilibrium dialysis. Pooled blood plasma was used in the study. Control solutions contained the same dosages of BP-C1 in PBS (pH 7.2). Plasma and control solutions were submitted to equilibrium dialysis across a vertical 8 kDa cut-off membrane for 4 h at 37 °C under gentle shaking. Platinum was quantified in dialysis and retained fractions using inductively coupled plasma mass spectrometry after microwave digestion. The dialysis system was tested and validated; this showed no protein saturation with platinum. A medium degree of binding of platinum to macromolecular species of ca. 60% was observed. The study showed the maintenance of a high fraction of free BP-C1 in the bloodstream, facilitating its pharmacological activity.

Comparison of the Methods for Determining Pyrogenically Modified Carbon Compounds

The soil organic matter (SOM) is searched for the biomarkers and specific features associated with the effect of wildfires by the case study of peat soil, Rheic Hemic Histosol (Lignic), in the south of the middle taiga of the Komi Republic. It is shown that fires considerably influence the peat organic matter. Pyrogenic activity is assessed according to the content of charcoal particles. SOM is examined using solid-state 13C-NMR spectroscopy to determine the concentrations of polycyclic aromatic hydrocarbons (PAHs) and benzene polycarboxylic acids (BPCAs). The used methods allow for diagnosing the effects of wildfires on the SOM composition. In the horizons with the signs of pyrogenesis, the share of carbon represented by aromatic fragments increases as well as the PAH concentration, mainly at the expense of naphthalene, phenanthrene, and chrysene. The carbon stock of pyrogenically modified compounds, amounting to 4.4 kg/m2, is for the first time assessed in the European north based on the BPCA content. The characteristics of pyrogenically changed organic compounds and their fragments obtained by different methods correlate well: the Pearson coefficient for the correlation of the carbon content in aromatic compounds (Caryl) with total BPCA content is R = 0.84 (p < 0.05) and with individual BPCAs, R = 0.81–0.90 (p < 0.05).

Use of molecular markers and compound-specific isotopic signatures to trace sources of black carbon in surface sediments of Peninsular Malaysia: Impacts of anthropogenic activities

Black carbon (BC) acts as a reservoir of carbon in sediment due to its high persistency. Southeast Asia (SEA) is a main source region for BC emissions across the globe due to extensive biomass burning and escalating fossil fuel consumption. However, our understanding of the sources and sinks of BC in SEA is limited. Here, we have analysed BC structure using benzene polycarboxylic acid (BPCA) method in combination of stable carbon isotope (δ13C) signatures for B5CA and B6CA using HPLC-IRMS in sediment samples from riverine, coastal and shelf areas in Peninsular Malaysia. BPCA molecular markers indicated higher degree of aromatic condensation and lighter isotopic composition in relatively pristine environment of the East coast compared to developed environment of the West and South coast. n-Alkane biomarkers clearly demonstrated higher anthropogenic impacts on the sediments of the West and South coast compared to the East coast. Biomass burning with the predominance of C3 plants and the large share of natural gas in the energy mix in Malaysia are possibly the main reasons for the isotopically light composition of sedimentary BC (−45.4 to −26.4‰). Atmospheric soot and petrogenic BC are the possible main sources of BC in the East coast sediments, while char residues of low temperature biomass burning likely contribute more to sedimentary BC in the West and South coast. The n-alkane indices implied that the sediments of the Kelantan adjacent shelf area receive great proportion of terrestrial organic matter and the associated BC.

Stability of Woodchips Biochar and Impact on Soil Carbon Stocks: Results from a Two-Year Field Experiment

Biochar has been shown to improve soil quality and crop yields. Furthermore, thanks to its high carbon content (C) and stable chemical structure, biochar can sequester C in the soil for a long time, mitigating climate change. However, the variability in published biochar stability in the soil makes verifying this trait under different environmental and agricultural conditions necessary. Moreover, most of the published literature refers to short-term incubation experiments, which are considered to not adequately represent long-term dynamics under field conditions. This article reports the results of a field experiment carried out in a vineyard near Merano, northern Italy, where the stability of woodchips biochar in soil, its impact on the total soil C stocks as well as on the original soil organic C (priming effect) were studied over two years. Vineyard soil (Dystric Eutrochrept) was amended with biochar (25 and 50 t ha−1) alone or together with compost (45 t ha−1) and compared with unamended control soil. Two methods assessed the stability of biochar in soil: the isotopic mass balance approach and the quantification of Benzene PolyCarboxylic Acids (BPCAs), molecular markers of biochar. The amount of C in the soil organic matter (SOM-C) was determined in the amended plots by subtracting the amount of biochar-C from the total soil organic C stock, and the occurrence of priming effect was verified by comparing SOM-C values at the beginning and at the end of the experiment. Results did not show any significant biochar degradation for both application rates, but results were characterized by a high variation. The application of 50 t ha−1 of biochar significantly increased soil C stock while no effect of biochar on the degradation of SOM-C was observed. Results were confirmed in the case of biochar application together with compost. It can be concluded that the use of woodchips biochar as a soil amendment can increase soil C content in the medium term. However, further analyses are recommended to evaluate the impact of biochar on climate change mitigation in the long term.

Reusability Investigation of a Ruthenium Catalyst during Ruthenium Ion-Catalyzed Oxidative Depolymerization of Lignite for the Production of Valuable Organic Acids.

A clean and efficient conversion process is essential for the utilization of low-rank coals. Lignite, a typical representative of the low-rank coal family, has huge potential for the production of valuable chemicals via the oxidative depolymerization reaction. Ruthenium ion-catalyzed oxidation (RICO) is an effective route for lignite depolymerization under mild conditions, but the high cost of precious Ru limits the potential large-scale application of RICO. How to recycle and reuse Ru is critical to promote the application of RICO. In this work, a novel and efficient approach for reusing Ru through recycling the solvent mixture containing Ru was established for RICO. First, the influence of different reaction parameters on the depolymerization degree of lignite and benzene polycarboxylic acid (BPCA) yields was investigated. Second, the distribution of Ru in the organic phase (OP), aqueous phase (AP), and residual solid phase (RSP) was analyzed after the RICO reaction. Finally, based on the distribution of Ru in different phases, a novel route of recycling Ru by reusing the Ru-containing solvents was proposed. The results showed that the dosage of RuCl3 and NaIO4 had a significant influence on both the depolymerization degree of lignite and BPCA yields. The distribution of Ru had a close relationship with the depolymerization degree of lignite and the dosage of NaIO4. After the depolymerization reaction, the CCl4 phase containing Ru was reused directly as the solvent for the next run, which could fulfill the reuse of both CCl4 and Ru. The results proved that the Ru-containing CCl4 phase could maintain catalytic performance for 5 runs. This work provides an efficient route to reuse Ru for the RICO depolymerization of lignite into valuable organic acids. As far as we know, this is the first report concerning the recycling and reuse of Ru during the RICO of lignite. This work is important for the application of RICO in lignite depolymerization.

IMPORTANCE OF HUMIC SUBSTANCES FOR STABILIZING SOIL AGGREGATES AND CENTRAL REACTIONS EXPLANATION IN SOIL: A REVIEW

Humic substances have an essential function in soil fertility and are viewed as being of prime importance for soil aggregation stability. Humic substances as part of humus-soil organic matter are chemicals generated from the biomolecules physically, chemical and microbiologically (humifying). It is essential since it is the most pervasive biological material source, which nature knows. Roughly 80 percent of total carbon is produced with terrestrial humic compounds and 60 percent of the water dissolved carbon. During the last three decades there have been challenges in two major approaches, the concept of soil humic substances. Much of the organic aromatic soil originates from the carbon that is frequently known as black carbon (black carbon). However, the detection of benzene polycarboxylic acid markers and the UV technique in soil with two commonly used methods is not trustworthy. Polymerisation of phenolic compounds produced from the breakdown and synthesis of lignin microorganisms may result in a wide number of humic chemicals and components including organic molecules and inorganic molecules. The addition of e.g., triazines or tensile compounds that cause to bound residues in the humic matrix demonstrates that humic substances are crucial for clarifying critical soil processes. Plant nutrients, comprising p, fe and cu, are available in soil this is equally essential to understand and can directly influence the growth of higher plants in the soil.

Year‐Round Measurements of Dissolved Black Carbon in Coastal Southeast Asia Aerosols: Rethinking Its Atmospheric Deposition in the Ocean

AbstractDissolved black carbon (DBC) is an important recalcitrant fraction of marine dissolved organic matter. Riverine discharge is the largest known source of oceanic DBC; however, the significance of atmospheric deposition as a source of oceanic DBC remains poorly understood. In this study, year‐round aerosol sampling was carried out at a rural coastal site in Southeast Asia for DBC analysis using the benzene polycarboxylic acid (BPCA) method. The results revealed the uncertainty of an earlier estimate of the atmospheric deposition flux of DBC to the global ocean (FDBC), which assumed a linear correlation between DBC and water‐soluble organic carbon (WSOC). The correlation between DBC and WSOC depended on the sources of carbonaceous aerosols. The DBC/WSOC ratios were higher for the biomass burning aerosols. DBC was linearly correlated with black carbon (BC) for biomass or fossil fuel combustion aerosols. However, the DBC/BC ratios were higher for biomass burning aerosols (0.41 ± 0.22), whereas lower for fossil fuel combustion aerosols (0.04 ± 0.03). FDBC was revisited based on the relationship between DBC and BC. FDBC is primarily contributed by biomass burning aerosols and maybe previously underestimated. In this study, the DBC in aerosols had less condensed aromatic structures than the DBC present in the major rivers of the world, as shown by the BPCA compositions. This indicated that oceanic DBC sourced from atmospheric deposition was less likely to be removed by photodegradation and sedimentation, as compared to the DBC sourced from riverine discharge.

Dissolved Black Carbon and Semivolatile Aromatic Hydrocarbons in the Ocean: Two Entangled Biogeochemical Cycles?

Dissolved black carbon (DBC) plays a role in the oceanic carbon cycle. DBC originates from the heating and incomplete combustion of organic matter, including fossil fuels, a shared origin with polycyclic aromatic hydrocarbons (PAH). DBC is quantified using the benzene polycarboxylic acids produced by oxidation of the organic extract, a fraction of which derive from PAHs and other semivolatile aromatic-like compounds (SALCs). However, the current view of the DBC cycle does not take into account the inputs and sinks known for PAHs, such as diffusive air–water exchange and degradation. A meta-analysis of oceanic PAHs, SALCs, and DBC concentrations shows that SALCs account for 16% of DBC (ranging from 5% to 31%). Such a large contribution of semivolatile aromatic hydrocarbons to DBC is consistent with the large atmospheric input of SALCs (estimated as 400 Tg C y–1). Furthermore, photodegradation at the surface ocean and microbial degradation in the water column of semivolatile DBC can be important sinks, consistent with the ubiquitous occurrence of the degradation genes of the metabolic routes for aromatic hydrocarbons. Future work should focus on the characterization of semivolatile DBC and its degradation in order to constrain its contribution to refractory organic matter and the anthropogenic perturbation of the carbon cycle.