Monocyclic Aromatic Compounds Research Articles

Organic Components of Personal PM2.5 Exposure Associated with Inflammation: Evidence from an Untargeted Exposomic Approach.

Fine particulate matter (PM2.5) can promote chronic diseases through the fundamental mechanism of inflammation; however, systemic information is lacking on the inflammatory PM2.5 components. To decipher organic components from personal PM2.5 exposure that were associated with respiratory and circulatory inflammatory responses in older adults, we developed an exposomic approach using trace amounts of particles and applied it on 424 personal PM2.5 samples collected in a panel study in Beijing. Applying an integrated multivariate and univariate untargeted strategy, a total of 267 organic compounds were filtered and then chemically identified according to their association with exhaled nitric oxide (eNO)/interleukin (IL)-6 or serum IL-1β/IL-6, with monocyclic and polycyclic aromatic compounds (i.e., MACs and PACs) as the representatives. Indoor-derived species with medium volatility including MACs were mainly associated with systemic inflammation, while low-volatile ambient components that originate from combustion sources, such as PACs, were mostly associated with airway inflammation. Following ambient component exposure, we found an inverted U-shaped relationship on change of eNO with insulin resistance, suggesting a higher risk of cardiopulmonary dysfunction for individuals with homeostatic model assessment for insulin resistance (HOMA-IR) levels > 2.3. Overall, this study provided a practical untargeted strategy for the systemic investigation of PM2.5 components and proposed source-specific inflammatory effects.

Proteomic Characterization of the Pseudomonas sp. Strain phDV1 Response to Monocyclic Aromatic Compounds.

The degradation of aromatic compounds comprises an important step in the removal of pollutants and re-utilization of plastics and other non-biological polymers. Here, Pseudomonas sp. strain phDV1, a gram-negative bacterium that is selected for its ability to degrade aromatic compounds is studied. In order to understand how the aromatic compounds and their degradation products are reintroduced in the metabolism of the bacteria and the systematic/metabolic response of the bacterium to the new carbon source, the proteome of this strain is analyzed in the presence of succinate, phenol, and o-, m-, and p-cresol as the sole carbon source. As a reference proteome, the bacteria are grown in succinate and then compared with the respective proteomes of bacteria grown on phenol and different cresols. In total, 2295 proteins are identified; 1908 proteins are used for quantification between different growth conditions. The carbon source affects the synthesis of enzymes related to aromatic compound degradation and in particular the enzyme involved in the meta-pathway of monocyclic aromatic compounds degradation. In addition, proteins involved in the production of polyhydroxyalkanoate (PHA), an attractive biomaterial, show higher abundance in the presence of monocyclic aromatic compounds. The results provide, for the first time, comprehensive information on the proteome response of this strain to monocyclic aromatic compounds.

Kinetic analysis of waste tire pyrolysis with metal oxide and zeolitic catalysts

Research interest in the conversion of waste tire into energy and fuels via pyrolysis process has increased extensively. To optimize pyrolysis reactor design and operating conditions, an understanding of the pyrolysis kinetics of waste tire is of fundamental importance. This study investigated the pyrolysis kinetics of waste tire in three cases (no catalyst, ZSM-5, and MnO2) under different heating rates. The thermogravimetric data showed that there was no apparent difference between the devolatilization processes of waste tire without catalyst and with ZSM-5. The activation energy was obtained by Friedman’s method, Kissinger-Akahira-Sunose (KAS) method and Flynn-Wall-Ozawa (FWO) method. The activation energy of waste tire pyrolysis suggested that MnO2 had a positive influence on the thermal decomposition of waste tire. Under the catalysis of ZSM-5, the pyrolysis of waste tire produced more C1-C4 alkanes and alkenes. While, the monocyclic aromatic compounds in the oil products were also enriched. Whereas, ZSM-5, which has been popularly used in thermal chemical conversions, had little catalytic effect on the decomposition of waste tire.

Characterization of Ligninolytic Bacteria and Analysis of Alkali-Lignin Biodegradation Products.

Ligninolytic bacteria degrading lignin were isolates and identified, and their biodegradation mechanism of alkaline-lignin was investigated. Four strains with lignin degradation capability were screened and identified from the soil, straw, and silage based on their decolorizing capacity of aniline blue and colony size on alkaline-lignin medium. The degradation ratio of Bacillus aryabhattai BY5, Acinetobacter johnsonii LN2, Acinetobacter lwoffii LN4, and Micrococcus yunnanensis CL32 have been assayed using alkaline-lignin as the unique carbon source. Further, the Lip (lignin peroxidase) and Mnp (manganese peroxidase) activities of strains were investigated. Lip activity of A. lwoffii LN4 was highest after 72 h of incubation and reached 7151.7 U · l–1. Mnp activity of M. yunnanensis CL32 was highest after 48 h and reached 12533 U · l–1. The analysis of alkaline-lignin degradation products by GC-MS revealed that the strains screened could utilize aromatic esters compounds such as dibutyl phthalate (DBP), and decomposite monocyclic aromatic compounds through the DBP aerobic metabolic pathway. The results indicate that B. aryabhattai BY5, A. johnsonii LN2, A. lwoffii LN4, and M. yunnanensis CL32 have high potential to degrade alkaline-lignin, and might utilize aromatic compounds by DBP aerobic metabolic pathway in the process of lignin degradation.

Microwave-assisted catalytic pyrolysis of waste printed circuit boards, and migration and distribution of bromine

Microwave-assisted pyrolysis (MAP) of waste printed circuit boards (WPCB) was performed to investigate the characteristics of pyrolysis product and Br fixation. Pyrolysis conversion increased with increasing temperature, reaching 93.3 % at 650 °C. However, increasing heating time did not exhibit remarkable influence on pyrolysis conversion. At 350 °C, phenols were main compounds in the oil accounting for 91.15 %. As the temperature increased to 650 °C, polycyclic aromatic hydrocarbons and monocyclic aromatic hydrocarbons (except phenols) increased to 20.55 % and 19.03 %, respectively. Meanwhile, the total content of CO2, CO, CH4 and H2 in the non-condensable gases increased significantly. Addition of ZSM-5 and kaolin promoted the recombination reaction of pyrolysis products, increased the relative percentage of monocyclic aromatic hydrocarbons (except phenols) and C11-C20 compounds in the oil, and reduced non-condensable gases. The oxygen bomb-ion chromatography was used to evaluate the Br content of pyrolysis residues. Higher pyrolysis temperature enhanced transfer of Br to pyrolysis gas. K2CO3, Na2CO3 and NaOH reacted with hydrogen bromide to generate KBr and NaBr, which significantly improved the Br fixation efficiency of pyrolysis residues (i.e. from 29.11%–99.80%, 96.39 % and 86.69 %, respectively) and reduced Br content in pyrolysis gas.

Molecular structure determination: Equilibrium structure of pyrimidine (m-C4H4N2) from rotational spectroscopy (re SE) and high-level ab initio calculation (re) agree within the uncertainty of experimental measurement.

The pure rotational spectrum of pyrimidine (m-C4H4N2), the meta-substituted dinitrogen analog of benzene, has been studied in the millimeter-wave region from 235 GHz to 360 GHz. The rotational spectrum of the ground vibrational state has been assigned and fit to yield accurate rotational and distortion constants. Over 1700 distinct transitions were identified for the normal isotopologue in its ground vibrational state and least-squares fit to a partial sextic S-reduced Hamiltonian. Transitions for all four singly substituted 13C and 15N isotopologues were observed at natural abundance and were likewise fit. Deuterium-enriched samples of pyrimidine were synthesized, giving access to all eleven possible deuterium-substituted isotopologues, ten of which were previously unreported. Experimental values of rotational constants and computed values of vibration-rotation interaction constants and electron-mass corrections were used to determine semi-experimental equilibrium structures (re SE) of pyrimidine. The re SE structure obtained using coupled-cluster with single, double, and perturbative triple excitations [CCSD(T)] corrections shows exceptional agreement with the re structure computed at the CCSD(T)/cc-pCV5Z level (≤0.0002 Å in bond distance and ≤0.03° in bond angle). Of the various computational methods examined, CCSD(T)/cc-pCV5Z is the only method for which the computed value of each geometric parameter lies within the statistical experimental uncertainty (2σ) of the corresponding semi-experimental coordinate. The exceptionally high accuracy and precision of the structure determination is a consequence of the large number of isotopologues measured, the precision and extent of the experimental frequency measurements, and the sophisticated theoretical treatment of the effects of vibration-rotation coupling and electron mass. Taken together, these demanding experimental and computational studies establish the capabilities of modern structural analysis for a prototypical monocyclic aromatic compound.

Oxygen detoxification by dienoyl‐CoA oxidase involving flavin/disulfide cofactors

Class I benzoyl-CoA reductases (BCRs) are oxygen-sensitive key enzymes in the degradation of monocyclic aromatic compounds in anaerobic prokaryotes. They catalyze the ATP-dependent reductive dearomatization of their substrate to cyclohexa-1,5-diene-1-carboxyl-CoA (1,5-dienoyl-CoA). An aromatizing 1,5-dienoyl-CoA oxidase (DCO) activity has been proposed to protect BCRs from oxidative damage, however, the gene and its product involved have not been identified, yet. Here, we heterologously produced a DCO from the hyperthermophilic euryarchaeon Ferroglobus placidus that coupled the oxidation of two 1,5-dienoyl-CoA to benzoyl-CoA to the reduction of O2 to water at 80°C. DCO showed similarities to members of the old yellow enzyme family and contained FMN, FAD and an FeS cluster as cofactors. The O2 -dependent activation of inactive, reduced DCO is assigned to a redox thiol switch at Eo ' = -3mV. We propose a catalytic cycle in which the active site FMN/disulfide redox centers are reduced by two 1,5-dienoyl-CoA (reductive half-cycle), followed by two consecutive two-electron transfer steps to molecular oxygen via peroxy- and hydroxyflavin intermediates yielding water (oxidative half-cycle). This work identified the enzyme involved in a unique oxygen detoxification process for an oxygen-sensitive catabolic enzyme.

Artificial produced water as a medium to grow Chlorella sp. for biodiesel production

Increased interest in renewable, carbon-neutral energy sources makes processing biodiesel from microalgae has become the objective for many researchers and companies. Some kind of wastewater including municipal, industrial and agricultural wastewaters have been identified as alternate growth mediums. Produced water is the largest byproduct of the oil and natural gas extraction process which constitutes of high concentration of pollutants, such as dissolved nitrogen, phosphorus, dissolved organic carbon, heavy metal and monocyclic aromatic compound like BTEX. The purpose of this study is to identify Chlorella sp. potential for producing lipid in artificial produced water. Variations made in this study consist of 0%, 25%, 50%, 75% and 100% volume of artificial produced water to the control Walne medium. The highest specific growth rate and biomass productivity of Chlorella sp. achieved by culture grown in 25% wastewater with a value of 0.225 day−1 and 0.175 g L−1day−1, respectively. The highest lipid yield and productivity in mixed culture of artificial produced water and Walne medium achieved by culture in 25% artificial produced water with value of 0.231 and 40.48 mg.L−1.day−1. C16 and C18 fatty acids which dominated the lipids of Chlorella sp. in all culture variations indicated that the lipid of Chlorella sp. were suitable for producing high quality biodiesel.

Four Aromatic Intradiol Ring Cleavage Dioxygenases from Aspergillus niger.

Ring cleavage dioxygenases catalyze the critical ring-opening step in the catabolism of aromatic compounds. The archetypal filamentous fungus Aspergillus niger previously has been reported to be able to utilize a range of monocyclic aromatic compounds as sole sources of carbon and energy. The genome of A. niger has been sequenced, and deduced amino acid sequences from a large number of gene models show various levels of similarity to bacterial intradiol ring cleavage dioxygenases, but no corresponding enzyme has been purified and characterized. Here, the cloning, heterologous expression, purification, and biochemical characterization of four nonheme iron(III)-containing intradiol dioxygenases (NRRL3_02644, NRRL3_04787, NRRL3_05330, and NRRL3_01405) from A. niger are reported. Purified enzymes were tested for their ability to cleave model catecholate substrates, and their apparent kinetic parameters were determined. Comparisons of kcat/Km values show that NRRL3_02644 and NRRL3_05330 are specific for hydroxyquinol (1,2,4-trihydroxybenzene), and phylogenetic analysis shows that these two enzymes are related to bacterial hydroxyquinol 1,2-dioxygenases. A high-activity catechol 1,2-dioxygenase (NRRL3_04787), which is phylogenetically related to other characterized and putative fungal catechol 1,2-dioxygenases, was also identified. The fourth enzyme (NRRL3_01405) appears to be a novel homodimeric Fe(III)-containing protocatechuate 3,4-dioxygenase that is phylogenetically distantly related to heterodimeric bacterial protocatechuate 3,4-dioxygenases. These investigations provide experimental evidence for the molecular function of these proteins and open the way to further investigations of the physiological roles for these enzymes in fungal metabolism of aromatic compounds.IMPORTANCE Aromatic ring opening using molecular oxygen is one of the critical steps in the degradation of aromatic compounds by microorganisms. While enzymes catalyzing this step have been well-studied in bacteria, their counterparts from fungi are poorly characterized despite the abundance of genes annotated as ring cleavage dioxygenases in fungal genomes. Aspergillus niger degrades a variety of aromatic compounds, and its genome harbors 5 genes encoding putative intracellular intradiol dioxygenases. The ability to predict the substrate specificities of the encoded enzymes from sequence data are limited. Here, we report the characterization of four purified intradiol ring cleavage dioxygenases from A. niger, revealing two hydroxyquinol-specific dioxygenases, a catechol dioxygenase, and a unique homodimeric protocatechuate dioxygenase. Their characteristics, as well as their phylogenetic relationships to predicted ring cleavage dioxygenases from other fungal species, provide insights into their molecular functions in aromatic compound metabolism by this fungus and other fungi.

Chemoenzymatic Synthesis of (-)-Ribisins A and B from Dibenzo[b,d]furan.

cis-Dihydrodiols, derived from monocyclic aromatic compounds, are valuable chiral pool intermediates for the synthesis of cyclic natural products. A drawback of this approach, to the synthesis of polycyclic secondary metabolites, is that additional rings must be annulated. To date, relatively few chiral natural products have been synthesized from polycyclic arene cis-dihydrodiols. Fungal metabolites, (-)-ribisins A and B, have now been obtained by functional group manipulation of a tricyclic arene metabolite, obtained from toluene dioxygenase-catalyzed regioselective and stereoselective cis-dihydroxylations of dibenzo[b,d]furan. The synthetic sequences were marginally shorter than the alternative routes, using monocyclic arene cis-dihydrodiols, and required no carbon-carbon bond-forming reactions.

Benzene promotes microbial Fe(III) reduction and flavins secretion

Abstract The microbial reduction of Fe(III) (oxyhydr)oxide is widespread in subsurface and plays a critical role in both the biogeochemical cycle of iron and the fate of contaminants. Monocyclic aromatic compounds are ubiquitous constituents of organic matter in many geologic environments and contaminated subsurface. Benzene is a typical monocyclic aromatic compound and frequently occurs in the subsurface environment. Due to its carcinogenicity and cytotoxicity, benzene may be toxic to the coexisted Fe(III)-reducing bacteria and thereby inhibit the microbial Fe(III) reduction. However, there is limited knowledge about the impact of the coexisting monocyclic aromatic compounds on the microbial Fe(III) reduction. In this study, the reduction of ferrihydrite by the dissimilatory iron-reducing bacterium Shewanella oneidensis MR-1 (MR-1) was investigated in the presence of benzene. Results showed that benzene had a negligible impact on the growth, cell morphology and integrity of MR-1, but it promoted the microbial Fe(III) reduction. The promotion of microbial Fe(III) reduction is maximum at benzene concentration of 3.8 μM. In the presence of 3.8 μM benzene, the produced Fe(II) from microbial Fe(III) reduction in 60 h doubled that in the absence of benzene, and the Fe(II)-O content of mineral surface after reduction experiment increased 4.73%. The promotion of microbial Fe(III) reduction was ascribed to the benzene induced increase of cell membrane permeability, which facilitated extracellular electron transfer and the secretion and release of flavin mononucleotide (FMN) as electron shuttle or cofactor. The impacts of benzene on the FMN secretion and microbial Fe(III) reduction have broad implications for both the cycling of iron and the biogeochemical transformation of redox-sensitive elements and contaminants in the benzene-containing subsurface environments.

Pyrolysis behaviors and product distribution of Shengli Lignite at different heating rate and final temperature by TG-FTIR and Py-GC-MS

ABSTRACT The slow pyrolysis characteristics of Shengli lignite (SL) from ambient temperature to 800°C at heating rates of 20°C/min and 100°C/min were investigated by thermogravimetric analysis coupled with Fourier transform infrared spectrometry (TG-FTIR) and by pyrolysis coupled with gas chromatography-mass spectrometry (Py-GC-MS). The final temperatures had larger effect on the pyrolysis products. The pyrolysis at 800°C of 20°C/min and 100°C/min (from the Py-GC-MS) obtained a variety of aliphatic compounds and monocyclic aromatic compounds, including short-chain olefins, alcohols, and ketones. But at 400°C, almost no short-chain aliphatic compounds were obtained, and a faster heating rate (100°C/min) was beneficial for obtaining long-chain aliphatic alkanes, alcohols, and acids (n-Hexadecanoic acid and Octadecanoic acid). It provides evidence that the aliphatic chains in lignite structure were long-chain, and the short-chain aliphatic compounds were from the secondary decomposition. The bicyclic compounds, monocyclic aromatic compounds were always important products. The real-time FTIR showed obvious differences in the pyrolysis at different heating rates. In the slower pyrolysis process (20°C/min), the absorbance of CO2 was much higher than that in the other processes, but in the faster pyrolysis process (100°C/min), the diversity of the pyrolysis products was substantially improved by the -OH, C = O, -COOH, C-CH3 and aromatic C-H functional groups, so maybe more valuable gas/liquid products could be produced at larger heating rate. The products at some specific temperatures (from the DTG peaks) were also provided for the reaction analysis.

Capability of Nocardia nova found in activated sludge to use synthetic BTEX as sole source of carbon and energy

ABSTRACT Benzene and its derivatives, toluene, ethylbenzene and xylenes (BTEXs) are volatile monocyclic aromatic compounds which are widely distributed in nature and highly hazardous to human and animal health. The species belonging to the genus Nocardia are filamentous bacteria widely present in the flocs of activated sludge. They lead to the formation of foams and bulking sludge, which disrupt the sludge settling properties and thus reduce the quality of the purified water. The aim of our study is to isolate from these filamentous bacteria in the activated sludge, indigenous strains of Nocardia able to use the BTEX as the sole source of carbon and energy. Two isolation media were used to isolate the Nocardia species found in the activated sludge samples taken from the Ibn Ziad (Constantine-Algeria) wastewater treatment plant. The results show that five strains that morphologically resemble Nocardia have been isolated. The strain named (S) was identified by the sequencing of its 16S rRNA gene as Nocardia nova. This strain was the only isolate capable of growing under laboratory conditions, on BTE (m-o-p) X added at concentrations of 1500 mg/L each. Such a result can be used in the bioremediation of aquatic or terrestrial ecosystems contaminated by these compounds, using this bacterium as a bio-augmentation agent.

Chemical Characteristics of Organic Aerosols in Shanghai: A Study by Ultrahigh‐Performance Liquid Chromatography Coupled With Orbitrap Mass Spectrometry

AbstractParticulate matter 2.5 (PM2.5) filter samples were collected in July and October 2014 and January and April 2015 in urban Shanghai and analyzed using ultrahigh‐performance liquid chromatography coupled to Orbitrap mass spectrometry. The measured chromatogram‐mass spectra were processed by a nontarget screening approach to identify significant signals. In total, 810–1,510 chemical formulas of organic compounds in the negative polarity (negative electrospray ionization (ESI−)) and 860–1,790 in the positive polarity (ESI+), respectively, were determined. The chemical characteristics of organic aerosols (OAs) in Shanghai varied among different months and between daytime and nighttime. In the January samples, organics were generally richer in terms of both number and abundance, whereas those in the July samples were far lower. More CHO− (compounds containing only carbon, hydrogen, and oxygen and detected in ESI−) and CHOS− (sulfur‐containing organics) were found in the daytime samples, suggesting a photochemical source, whereas CHONS− (nitrogen‐ and sulfur‐containing organics) were more abundant in the nighttime samples, due to nocturnal nitrate radical chemistry. A significant number of monocyclic and polycyclic aromatic compounds, and nitrogen‐ and sulfur‐containing heterocyclic compounds, were detected in all samples, indicating that biomass burning and fossil fuel combustion made important contributions to the OAs in urban Shanghai. Additionally, precursor‐product pair analysis indicates that the epoxide pathway is an important formation route for organosulfates observed in Shanghai. Moreover, a similar analysis suggests that 35–57% of nitrogen‐containing compounds detected in ESI+ could be formed through reactions between ammonia and carbonyls. Our study presents a comprehensive overview of OAs in urban Shanghai, which helps to understand their characteristics and sources.

Production of monocyclic phenols by the liquid-phase hydrogenolysis of benzofuran and dibenzyl ether using in situ hydrogen production from methanol

We herein report our study into the hydrogenolysis of benzofuran, a model compound for the poorly decomposable compounds derived from lignin, over Pt supported catalysts in methanol in the absence of gaseous hydrogen. In this in situ hydrogenolysis reaction system, it was elucidated that both hydrogen production from methanol and selective hydrogenolysis of the furan moiety proceeded simultaneously to yield monophenolic compounds and gaseous hydrogen. This in situ hydrogenolysis reaction was investigated at temperatures between 180 and 220 °C and with reaction times ranging from 1 to 48 h. We found that the hydrogenolysis reaction was accelerated with increased hydrogen concentrations in the solvent. The molar ratio of consumed hydrogen to net hydrogen production increased gradually upon increasing the reaction temperature and time. In addition, the in situ hydrogenolysis of benzofuran under a hydrogen gas atmosphere revealed that the hydrogen produced in situ was more effective in the reaction than gaseous hydrogen, likely due to the dissolution and diffusion resistances of the solvent. Furthermore, dibenzyl ether was hydrogenolyzed to give monocyclic aromatic compounds under the same reaction conditions, suggesting that this in situ hydrogenolysis process could be effective in converting the by-products obtained during lignin depolymerization into valuable aromatic compounds.

2 芳香族化合物の超音波分解 : 分解速度に及ぼす溶質疎水性の影響(一般講演)

2 芳香族化合物の超音波分解 : 分解速度に及ぼす溶質疎水性の影響(一般講演)

Conversion of cis-2-carboxycyclohexylacetyl-CoA in the downstream pathway of anaerobic naphthalene degradation.

The cyclohexane derivative cis-2-(carboxymethyl)cyclohexane-1-carboxylic acid [(1R,2R)-/(1S,2S)-2-(carboxymethyl)cyclohexane-1-carboxylic acid] has previously been identified as metabolite in the pathway of anaerobic degradation of naphthalene by sulfate-reducing bacteria. We tested the corresponding CoA esters of isomers and analogues of this compound for conversion in cell free extracts of the anaerobic naphthalene degraders Desulfobacterium strain N47 and Deltaproteobacterium strain NaphS2. Conversion was only observed for the cis-isomer, verifying that this is a true intermediate and not a dead-end product. Mass-spectrometric analyses confirmed that conversion is performed by an acyl-CoA dehydrogenase and a subsequent hydratase yielding an intermediate with a tertiary hydroxyl-group. We propose that a novel kind of ring-opening lyase is involved in the further catabolic pathway proceeding via pimeloyl-CoA. In contrast to degradation pathways of monocyclic aromatic compounds where ring-cleavage is achieved via hydratases, this lyase might represent a new ring-opening strategy for the degradation of polycyclic compounds. Conversion of the potential downstream metabolites pimeloyl-CoA and glutaryl-CoA was proved in cell free extracts, yielding 2,3-dehydropimeloyl-CoA, 3-hydroxypimeloyl-CoA, 3-oxopimeloyl-CoA, glutaconyl-CoA, crotonyl-CoA, 3-hydroxybutyryl-CoA and acetyl-CoA as observable intermediates. This indicates a link to central metabolism via β-oxidation, a non-decarboxylating glutaryl-CoA dehydrogenase and a subsequent glutaconyl-CoA decarboxylase.

Investigation of the pyrolysis behaviour of hybrid filter media for needle-punched nonwoven bag filters

Hybrid polymer fibre filter media are critical to the effectiveness of needle-punched nonwoven bag filters. We investigated the pyrolytic behaviour of hybrid filter media to analyze the contents of the components. The pyrolytic behaviour was investigated using pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS). Pyrolysates were directly injected for GC–MS analysis. In total, 19, 22 and 23 compounds were identified with contents varying from 0.29% to 78.30%, 0.14% to 78.75% and 0.34% to 70.96% for hybrid filter media A, B and C, respectively. A large number of monocyclic and polycyclic aromatic compounds were formed when the pyrolysis temperature was greater than 650°C. The contents of aromatic hydrocarbons increased with increasing temperature. In addition to the aromatic compounds, monomeric and diploid tetrafluoroethylene were produced. The contents of the fluorochemical for the hybrid filter media A, B and C were 46.04%, 52.60% and 1.85%, respectively, when the pyrolysis temperature was 750°C. A pyrolysis mechanism for the hybrid filter media was proposed based on the determined pyrolysates. The investigation results provide useful information for understanding the thermal properties of hybrid filter media. The contents of PTFE were quantitatively analysed to assess the influence of the hybrid filter media on the abrasion resistances.

Global atmospheric budget of simple monocyclic aromatic compounds

Abstract. The global atmospheric budget and distribution of monocyclic aromatic compounds is estimated, using an atmospheric chemistry general circulation model. Simulation results are evaluated with an ensemble of surface and aircraft observations with the goal of understanding emission, production and removal of these compounds.Anthropogenic emissions provided by the RCP database represent the largest source of aromatics in the model (≃ 23 TgC year−1) and biomass burning from the GFAS inventory the second largest (≃ 5 TgC year−1). The simulated chemical production of aromatics accounts for ≃ 5 TgC year−1. The atmospheric burden of aromatics sums up to 0.3 TgC. The main removal process of aromatics is photochemical decomposition (≃ 27 TgC year−1), while wet and dry deposition are responsible for a removal of ≃ 4 TgC year−1.Simulated mixing ratios at the surface and elsewhere in the troposphere show good spatial and temporal agreement with the observations for benzene, although the model generally underestimates mixing ratios. Toluene is generally well reproduced by the model at the surface, but mixing ratios in the free troposphere are underestimated. Finally, larger discrepancies are found for xylenes: surface mixing ratios are not only overestimated but also a low temporal correlation is found with respect to in situ observations.

Composition of the organic matter in soils from six pedoclimatic zones of Magdalena (Colombia)

The soils in the NE of the Magdalena province (Colombia) are subject to intense degradation primarily because of the low accumulation rate of soil organic matter (SOM) and its fast turnover. Numerous traditional studies have aimed to mitigate this situation, focusing on the analysis of total SOM contents. The present study aimed to determine SOM quality from six areas under humid and dry tropical forest with different pedoclimatic conditions, using molecular characterization. For each area, sites with different current land use were studied, including forest and cultivated sites. We applied analytical pyrolysis (pyrolysis-GC/MS) to aqueous NaOH-extractable SOM from surface soil samples. One-hundred and ten pyrolysis products were identified and quantified, from the following chemical groups: N-containing compounds (34.1 ± 5.1%), carbohydrate markers (21.1% ± 7.1%), monocyclic aromatic compounds (20.0% ± 4.5%), aliphatic compounds (7.7% ± 1.4%), phenols (7.0% ± 5.0%), polycyclic aromatic compounds (3.6% ± 0.9 %), lignin products (0.3% ± 0.3%) and other compounds (0.2% ± 0.1%). SOM of all studied areas showed a large proportion of N-containing products, indicating a high contribution from microbial material to the SOM. Multivariate statistics allowed for the differentiation between microbial-derived and plant-derived SOM (Factor 1) and the relative proportion of burning residues (Factor 2), and indicated that pedoclimatic conditions exert more influence on SOM composition (cool and humid zones were enriched in microbial SOM while dry zones contained more plant-derived SOM) than land use for the studied soils.