A microchip gas chromatography column assembly with a 3D metal printing micro column oven and a flexible stainless-steel column.

In this work, a microchip gas chromatography (GC) column assembly utilizing a three-dimensional (3D) printed micro oven and a flexible stainless steel capillary column was developed. The assembly's performance and separation capabilities were characterized. The key components include a 3D printed aluminum plate (7.50 × 7.50 × 0.16 cm) with a 3-meter-long circular spiral channel, serving as the oven, and the column coiled on the channel with an inner diameter of 320 µm and a stationary phase of OV-1. A heating ceramic plate was affixed on the opposite side of the plate. The assembly weighed 40.3 g. The design allows for easy disassembly, or stacking of heating devices and columns, enabling flexibility in adjusting column length. When using n-C13 as the test analyte at 140 °C, a retention factor (k) was 8.5, and 7797 plates (2599 plates/m) were obtained. The assembly, employing resistance heating, demonstrated effective separation performance for samples containing alkanes, aromatics, alcohols and ketones, with good reproducibility. The reduction in theoretical plates compared to oven heating was only 2.95 %. In the boiling point range of C6 to C18, rapid temperature programming (120 °C/min) was achieved with a power consumption of 119.512 W. The assembly was successfully employed to separate benzene series compounds, gasoline and volatile organic compounds (VOCs), demonstrating excellent separation performance. This innovative design addresses the challenges of the complexity and low repeatability of the fabrication process and the high cost associated with microchip columns. Furthermore, its versatility makes it suitable for outdoor analysis applications.

Dispersant addition, but not nutrients, stimulated blooms of multiple hydrocarbonoclastic genera in nutrient-replete coastal marine surface waters.

The range of impacts of chemical dispersants on indigenous marine microbial communities and their activity remains poorly constrained. We tested the response of nearshore surface waters chronically exposed to oil leakage from a downed platform and supplied with nutrients by the Mississippi River to Corexit dispersant and nutrient additions. As assessed using 14C-labeled tracers, hexadecane mineralization potential was orders of magnitude higher in all unamended samples than in previously assessed bathypelagic communities. Nutrient additions stimulated microbial mortality but did not affect community composition and had no generalizable effect on hydrocarbon mineralization potential. By contrast, Corexit amendments caused a rapid shift in community composition and a drawdown of inorganic nitrogen and orthophosphate though no generalizable effect on hydrocarbon mineralization potential. The hydrocarbonoclastic community's response to dispersants is largely driven by the relative availability of organic substrates and nutrients, underscoring the role of environmental conditions and multiple interacting stressors on hydrocarbon degradation potential.

Comprehensive study of retention influencing gas chromatographic parameters affecting linear retention indices.

Retention in gas chromatographic systems has a central role in the identification of compounds even if detectors providing spectral information are used. But linear retention indices (LRI) of a single compound originating from multiple sources tend to vary greatly, probably due to differences in the experimental settings of the determinations. The effect of gas chromatographic parameters on LRI has been investigated using 41 compounds - previously identified from food contact plastics - and n-alkanes (n-C7-n-C40) used as reference series. As the reproducibility of LRIs under the same conditions is generally very good, the smallest changes in the settings often caused statistically significant, though irrelevant changes in the LRI values. Therefore, a multicriterial scoring-ranking system has been worked out to highlight the LRI value differences. Our results highlight that column length, heating rate, and film thickness can all be the reasons of the varying published LRI values. We also demonstrated that for the reproduction of LRI data, the chemistry (and not simply the polarity) of the stationary phase is crucial.

The potential of Bacillus species isolated from Cinnamomum camphora for biofuel production.

BACKGROUND: Increasing concerns about climate change and global petroleum supply draw attention to the urgent need for the development of alternative methods to produce fuels. Consequently, the scientific community must devise novel ways to obtain fuels that are both sustainable and eco-friendly. Bacterial alkanes have numerous potential applications in the industry sector. One significant application is biofuel production, where bacterial alkanes can serve as a sustainable eco-friendly alternative to fossil fuels. This study represents the first report on the production of alkanes by endophytic bacteria. RESULTS: In this study, three Bacillus species, namely Bacillus atrophaeus Camph.1 (OR343176.1), Bacillus spizizenii Camph.2 (OR343177.1), and Bacillus aerophilus Camph.3 (OR343178.1), were isolated from the leaves of C. camphora. The isolates were then screened to determine their ability to produce alkanes in different culture media including nutrient broth (NB), Luria-Bertani (LB) broth, and tryptic soy broth (TSB). Depending on the bacterial isolate and the culture media used, different profiles of alkanes ranging from C8 to C31 were detected. CONCLUSIONS: The endophytic B. atrophaeus Camph.1 (OR343176.1), B. spizizenii Camph.2 (OR343177.1), and B. aerophilus Camph.3 (OR343178.1), associated with C. camphora leaves, represent new eco-friendly approaches for biofuel production, aiming towards a sustainable future. Further research is needed to optimize the fermentation process and scale up alkane production by these bacterial isolates.

From Antagonism to Enhancement: Triton X-100 Surfactant Affects Phenanthrene Interfacial Biodegradation by Mycobacteria through a Shift in Uptake Mechanisms.

Polycyclic aromatic hydrocarbons (PAHs), as persistent environmental pollutants, often reside in nonaqueous-phase liquids (NAPLs). Mycobacterium sp. WY10, boasting highly hydrophobic surfaces, can adsorb to the oil-water interface, stabilizing the Pickering emulsion and directly accessing PAHs for biodegradation. We investigated the impact of Triton X-100 (TX100) on this interfacial uptake of phenanthrene (PHE) by Mycobacteria, using n-tetradecane (TET) and bis-(2-ethylhexyl) phthalate (DEHP) as NAPLs. Interfacial tension, phase behavior, and emulsion stability studies, alongside confocal laser scanning microscopy and electron microscope observations, unveiled the intricate interplay. In surfactant-free systems, Mycobacteria formed stable W/O Pickering emulsions, directly degrading PHE within the NAPLs because of their intimate contact. Introducing low-dose TX100 disrupted this relationship. Preferentially binding to the cells, the surfactant drastically increased the cell hydrophobicity, triggering desorption from the interface and phase separation. Consequently, PAH degradation plummeted due to hindered NAPL access. Higher TX100 concentrations flipped the script, creating surfactant-stabilized O/W emulsions devoid of interfacial cells. Surprisingly, PAH degradation remained efficient. This paradox can be attributed to NAPL emulsification, driven by the surfactant, which enhanced mass transfer and brought the substrate closer to the cells, despite their absence at the interface. This study sheds light on the complex effect of surfactants on Mycobacteria and PAH uptake, revealing an antagonistic effect at low concentrations that ultimately leads to enhanced degradation through emulsification at higher doses. These findings offer valuable insights into optimizing bioremediation strategies in PAH-contaminated environments.

N-alkane shape distinctive microbial patterns in Kuroshio Extension.

Marine microorganisms are primary drivers of the elemental cycling. The interaction between heterotrophic prokaryotes and biomarker (n-alkane) in Kuroshio Extension (KE) remains unclear. Here, we categorize KE into three characteristic areas based on ocean temperatures and nutrient conditions: Cold Water Area (CWA), Mixed Area (MA), and Warm Water Area (WWA). A total of 49 samples were collected during two-year voyage to identify the source of n-alkane and associated degrading microorganisms. Total n-alkane concentrations (Σn-Alk) in surface water (SW) spanned from 1,308 ng L-1 to 1,890 ng L-1, it was significantly higher (Tukey-Kramer test, p < 0.05) in MA than CWA and WWA. The Σn-Alk in surface sediments (SS) gradually increased from north to south, ranging from 5,982 ng g-1 to 37,857 ng g-1. Bacteria and algae were the primary sources of n-alkane in both SW and SS. Proteobacteria was the most widely distributed among three areas. The presence of Rhodobacteraceae with alkB was the primary reason affecting n-alkane concentrations in SW. The Gammaproteobacteria with alkB and alkR chiefly affected n-alkane concentrations in SS. In summary, n-alkane s serve as an energy source for particular microorganisms, shaping the unique oceanographic patterns.

An integrated evaluation of bioenhanced in situ LNAPL dissolution.

Performance evaluation of in situ bioremediation processes in the field is difficult due to uncertainty created by matrix and contaminant heterogeneity, inaccessibility to direct observation, expense of sampling, and limitations of some measurements. The goal of this research was to develop a strategy for evaluating in situ bioremediation of light nonaqueous-phase liquid (LNAPL) contamination and demonstrating the occurrence of bioenhanced LNAPL dissolution by: (1) integrating a suite of analyses into a rational evaluation strategy; and (2) demonstrating the strategy's application in intermediate-scale flow-cell (ISFC) experiments simulating an aquifer contaminated with a pool of LNAPL (naphthalene dissolved in dodecane). Two ISFCs were operated to evaluate how the monitored parameters changed between a "no bioremediation" scenario and an "intrinsic in situ bioremediation" scenario. Key was incorporating different measures of microbial activity and contaminant degradation relevant to bioremediation: contaminant loss; consumption of electron acceptors; and changes in total alkalinity, pH, dissolved total inorganic carbon, carbon-stable isotopes, microorganisms, and intermediate metabolites. These measurements were integrated via mass-flux modeling and mass-balance analyses to document that in situ biodegradation of naphthalene was strongly accelerated in the "intrinsic in situ bioremediation" scenario versus "no bioremediation." Furthermore, the integrated strategy provided consistent evidence of bioenhancement of LNAPL dissolution through intrinsic bioremediation by a factor of approximately 2 due to the biodegradation of the naphthalene near the pool/water interface.

Metagenomic analysis of a thermophilic bacterial consortium and its use in the bioremediation of a petroleum-contaminated soil.

Biodegradation is difficult at high temperatures due to the limited capacity of microorganisms to survive and function outside their optimum temperature range. Here, a thermophilic petroleum-degrading consortium was enriched from compost at a temperature of 55 °C. 16S rDNA and metagenomic techniques were used to analyze the composition of the consortium and the mechanisms of degradation. The consortium degraded 17000 mg total petroleum hydrocarbons (TPHs) L-1 with a degradation efficiency of 81.5% in 14 days. The consortium utilized a range of substrates such as n-hexadecane, n-docosane, naphthalene and pyrene and grew well over a wide range of pH (4-10) and salinity (0-90 g L-1). The hydrocarbon-degrading extremophilic consortium contained, inter alia, (relative abundance >1%) Caldibacillus, Geobacillus, Mycolicibacterium, Bacillus, Chelatococcus, and Aeribacillus spp. Metagenomic analysis was conducted to discover the degradation and environmental tolerance functional genes of the consortium. Two alkane hydroxylase genes, alkB and ladA, were found. A microcosm study shows that the consortium promoted the bioremediation of soil TPHs. The results indicate that the consortium may be a good candidate for the high-temperature bioremediation of petroleum-contaminated soils.

Regiodivergent biosynthesis of bridged bicyclononanes.

Medicinal compounds from plants include bicyclo[3.3.1]nonane derivatives, the majority of which are polycyclic polyprenylated acylphloroglucinols (PPAPs). Prototype molecules are hyperforin, the antidepressant constituent of St. John's wort, and garcinol, a potential anticancer compound. Their complex structures have inspired innovative chemical syntheses, however, their biosynthesis in plants is still enigmatic. PPAPs are divided into two subclasses, named type A and B. Here we identify both types in Hypericum sampsonii plants and isolate two enzymes that regiodivergently convert a common precursor to pivotal type A and B products. Molecular modelling and substrate docking studies reveal inverted substrate binding modes in the two active site cavities. We identify amino acids that stabilize these alternative binding scenarios and use reciprocal mutagenesis to interconvert the enzymatic activities. Our studies elucidate the unique biochemistry that yields type A and B bicyclo[3.3.1]nonane cores in plants, thereby providing key building blocks for biotechnological efforts to sustainably produce these complex compounds for preclinical development.

IGC investigation of the effect of the length of the n-alkyl substituent in 5-alkylsubstituted norbornenes on solute retention.

Polymerization of 5-n-alkyl-substituted 2-norbornenes synthesized a series of polymers having the same structure of the main polymer chain, but differing in the length of the alkyl substituent (up to 14 methylene units). The obtained polymers were studied by the capillary IGC method as a stationary phase during separation of a mixture of normal hydrocarbons C6-C10. Retention data in the form of a logarithm of the retention factor lnk were correlated with the size of the sorbate (via the carbon number of the alkane ZS) and with the size of the n-alkyl substituent in the polymer chain (via the carbon number of the polymer ZP). Correlation of lnk vs. ZS turned out to be linear for all polymers, but the angle of the slope of linear dependence dlnk/dZS increases with a decrease in the carbon number of the polymer ZP. Dependency of dlnk/dZS vs. ZP is not linear and indicates an increase in the retention of sorbates by the stationary phase with a decrease in the length of the alkyl substituent in the polymer chain. The correlation of the retention of lnk analytes with the carbon number of the polymer ZP is not linear and indicates an increase in the sorbate/sorbent interaction with a decrease in the length of the alkyl substituent. Inflection points were found at both correlations with ZP in the region of ZP = 8, which indicates a possible change in the sorption mechanism or a change in the phase state of the polymer. In polymer chemistry, the phase state of a polymer is characterized by the glass transition temperature Tg, the dependence of which vs. ZP turned out to be nonlinear with an inflection point at ZP ∼11. Thus, a decrease in the length of the alkyl substituent leads to the transition of the polymer from a rubbery state to a glassy one at ZP ∼ 11, which in turn, with a further decrease in the carbon number of the polymer to ZP ∼ 8, causes a change in the sorption mechanism from bulk sorption to surface sorption. The change in the sorption mechanism is accompanied by an increase in the interaction of the sorbate with the stationary phase, which manifests itself both in an increase in the retention time of analytes and in an increase in the enthalpy and entropy of sorption. The reason for this increase can be seen in the formation of a microporous structure in 5-alkyl-substituted polynorbornenes in a glassy state.

Petroleum ether extract of Schisandra sphenanthera prevents hyperglycemia and insulin resistance in association with modulation of sweet taste receptors and gut microbiota in T2DM rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Schisandra sphenanthera (Schisandra sphenanthera Rehd. et Wils.) is the dried mature fruit of Schisandra sphenanthera, a plant in the Magnoliaceae family. It was used in the treatment of diabetes mellitus in the Jade Fluid Decoction and the Xiaoke pills, which were recorded in ancient books. However, its mechanism of action in the treatment of type 2 diabetes mellitus (T2DM) was unclear and needs further study. AIM OF THE STUDY: This research aimed to investigate the chemical composition and lignan content of Schisandra sphenanthera petroleum ether parts (SPEP) and to evaluate the effects of SPEP on sweet taste receptors (STRs) and intestinal flora in rats on a high-fat diet (HFD). Additionally, the relationships between SPEP and hyperglycemia and insulin resistance were examined. MATERIALS AND METHODS: GC-MS was used to determine the chemical composition of SPEP, and HPLC was used to determine the lignin content. A combination of the HFD and the administration of streptozotocin (STZ) was employed to generate a rat model of T2DM. Petroleum ether extracts from Schisandra sphenanthera were used as the focus of the research to evaluate the effects of these extracts on the glucolipid metabolism of T2DM rats, as well as the underlying mechanisms. RESULTS: Analysis of the GC-MS spectrum of SESP revealed a total of 58 compounds. HPLC analysis revealed that SPEP had the highest concentration of Schisandrin A and the lowest concentration of Schisandrol A. The drug administration intervention resulted in a significant decrease in body weight and pancreatic weight of diabetic rats compared to the Normal group. When compared to the Model group, the body weight of rats in the drug administration group and the Metformin group had a more moderate decrease, while the pancreatic weight and pancreatic-to-body ratio increased. The Model group shown significant increases in FBG, OGTT, GHb, TC, TG, LDL-C, ALT, AST, MDA, FINS, and NEFA, as well as significant decreases in HDL-C and SOD, when compared to the Normal group (P < 0.05). The administration of each group was found to be significantly effective in decreasing FBG, OGTT, GHb, TC, TG, LDL-C, ALT, AST, MDA, FINS, NEFA, while increasing HDL-C and SOD when compared to the Model group. The application of SPEP had a positive impact on hepatocyte swelling, hepatocyte degeneration, and necrosis, as well as the morphological structure of pancreatic islet cells. Furthermore, the protein expression levels of T1R2, TRPM5 and GLP-1 in the small intestine of the Model group were reduced. After a period of six weeks, the protein expression levels began to align more closely with those of the Normal group of rats. Analysis of 16S rRNA sequencing revealed that the intestinal microbiota of diabetic rats was significantly disrupted, with a decrease in the abundance of the Firmicutes phylum and an increase in the abundance of the Bacteroidetes phylum. Furthermore, the composition of the dominant genus was distinct from that of the control group. After the drug intervention, the microbiota of diabetic rats was significantly altered, exhibiting a higher abundance and diversity, as well as a significant enrichment of the community. The SPEP treatment resulted in a significant increase in acetic acid, propionic acid, and butyric acid. CONCLUSIONS: The findings of this research indicated that SPEP could be effective in treating T2DM through the regulation of STRs, the adjustment of disturbed metabolite levels, and the alteration of intestinal flora.

Simultaneous production of biosurfactant and extracellular unspecific peroxygenases by Moesziomyces aphidis XM01 enables an efficient strategy for crude oil degradation.

Crude oil is a hazardous pollutant that poses significant and lasting harm to human health and ecosystems. In this study, Moesziomyces aphidis XM01, a biosurfactant mannosylerythritol lipids (MELs)-producing yeast, was utilized for crude oil degradation. Unlike most microorganisms relying on cytochrome P450, XM01 employed two extracellular unspecific peroxygenases, MaUPO.1 and MaUPO.2, with preference for polycyclic aromatic hydrocarbons (PAHs) and n-alkanes respectively, thus facilitating efficient crude oil degradation. The MELs produced by XM01 exhibited a significant emulsification activity of 65.9% for crude oil and were consequently supplemented in an "exogenous MELs addition" strategy to boost crude oil degradation, resulting in an optimal degradation ratio of 72.3%. Furthermore, a new and simple "pre-MELs production" strategy was implemented, achieving a maximum degradation ratio of 95.9%. During this process, the synergistic up-regulation of MaUPO.1, MaUPO.1 and the key MELs synthesis genes contributed to the efficient degradation of crude oil. Additionally, the phylogenetic and geographic distribution analysis of MaUPO.1 and MaUPO.1 revealed their wide occurrence among fungi in Basidiomycota and Ascomycota, with high transcription levels across global ocean, highlighting their important role in biodegradation of crude oil. In conclusion, M. aphidis XM01 emerges as a novel yeast for efficient and eco-friendly crude oil degradation.

Archaea oxidizing alkanes through alkyl-coenzyme M reductases.

This review synthesizes recent discoveries of novel archaea clades capable of oxidizing higher alkanes, from volatile ones like ethane to longer-chain alkanes like hexadecane. These archaea, termed anaerobic multicarbon alkane-oxidizing archaea (ANKA), initiate alkane oxidation using alkyl-coenzyme M reductases, enzymes similar to the methyl-coenzyme M reductases of methanogenic and anaerobic methanotrophic archaea (ANME). The polyphyletic alkane-oxidizing archaea group (ALOX), encompassing ANME and ANKA, harbors increasingly complex alkane degradation pathways, correlated with the alkane chain length. We discuss the evolutionary trajectory of these pathways emphasizing metabolic innovations and the acquisition of metabolic modules via lateral gene transfer. Additionally, we explore the mechanisms by which archaea couple alkane oxidation with the reduction of electron acceptors, including electron transfer to partner sulfate-reducing bacteria (SRB). The phylogenetic and functional constraints that shape ALOX-SRB associations are also discussed. We conclude by highlighting the research needs in this emerging research field and its potential applications in biotechnology.

Unravelling the role of the group 6 soluble di-iron monooxygenase (SDIMO) SmoABCD in alkane metabolism and chlorinated alkane degradation.

Soluble di-iron monooxygenases (SDIMOs) are multi-component enzymes catalysing the oxidation of various substrates. These enzymes are characterized by high sequence and functional diversity that is still not well understood despite their key role in biotechnological processes including contaminant biodegradation. In this study, we analysed a mutant of Rhodoccocus aetherivorans BCP1 (BCP1-2.10) characterized by a transposon insertion in the gene smoA encoding the alpha subunit of the plasmid-located SDIMO SmoABCD. The mutant BCP1-2.10 showed a reduced capacity to grow on propane, lost the ability to grow on butane, pentane and n-hexane and was heavily impaired in the capacity to degrade chloroform and trichloroethane. The expression of the additional SDIMO prmABCD in BCP1-2.10 probably allowed the mutant to partially grow on propane and to degrade it, to some extent, together with the other short-chain n-alkanes. The complementation of the mutant, conducted by introducing smoABCD in the genome as a single copy under a constitutive promoter or within a plasmid under a thiostreptone-inducible promoter, allowed the recovery of the alkanotrophic phenotype as well as the capacity to degrade chlorinated n-alkanes. The heterologous expression of smoABCD allowed a non-alkanotrophic Rhodococcus strain to grow on pentane and n-hexane when the gene cluster was introduced together with the downstream genes encoding alcohol and aldehyde dehydrogenases and a GroEL chaperon. BCP1 smoA gene was shown to belong to the group 6 SDIMOs, which is a rare group of monooxygenases mostly present in Mycobacterium genus and in a few Rhodococcus strains. SmoABCD originally evolved in Mycobacterium and was then acquired by Rhodococcus through horizontal gene transfer events. This work extends the knowledge of the biotechnologically relevant SDIMOs by providing functional and evolutionary insights into a group 6 SDIMO in Rhodococcus and demonstrating its key role in the metabolism of short-chain alkanes and degradation of chlorinated n-alkanes.

Anaerobic oxidation of ammonium and short-chain gaseous alkanes coupled to nitrate reduction by a bacterial consortium.

The bacterial species "Candidatus Alkanivorans nitratireducens" was recently demonstrated to mediate nitrate-dependent anaerobic oxidation of short-chain gaseous alkanes (SCGAs). In previous bioreactor enrichment studies, the species appeared to reduce nitrate in two phases, switching from denitrification to dissimilatory nitrate reduction to ammonium (DNRA) in response to nitrite accumulation. The regulation of this switch or the nature of potential syntrophic partnerships with other microorganisms remains unclear. Here, we describe anaerobic multispecies cultures of bacteria that couple the oxidation of propane and butane to nitrate reduction and the oxidation of ammonium (anammox). Batch tests with 15N-isotope labelling and multi-omic analyses collectively supported a syntrophic partnership between "Ca. A. nitratireducens" and anammox bacteria, with the former species mediating nitrate-driven oxidation of SCGAs, supplying the latter with nitrite for the oxidation of ammonium. The elimination of nitrite accumulation by the anammox substantially increased SCGA and nitrate consumption rates, whereas it suppressed DNRA. Removing ammonium supply led to its eventual production, the accumulation of nitrite, and the upregulation of DNRA gene expression for the abundant "Ca. A. nitratireducens". Increasing the supply of SCGA had a similar effect in promoting DNRA. Our results suggest that "Ca. A. nitratireducens" switches to DNRA to alleviate oxidative stress caused by nitrite accumulation, giving further insight into adaptability and ecology of this microorganism. Our findings also have important implications for the understanding of the fate of nitrogen and SCGAs in anaerobic environments.

Biodegradation of aliphatic and aromatic hydrocarbons by bacteria isolated from Bahregan area.

Environmental pollution with aromatic and aliphatic hydrocarbons caused by oil and petrochemical industries has very toxic and carcinogenic effects on living organisms and should be removed from the environment. In this research, after analyzing the oil sludge of the Bahregan area, it was found that most aliphatic paraffin compounds are related to octadecane, most liquid aliphatic compounds are related to hexadecane, and most aromatic compounds are related to naphthalene, phenanthrene, fluoranthene, and anthracene. Then, we investigated the ability of native bacteria from this area, such as Thalassospira, Chromohalobacter, and a bacterial consortium, to biodegrade the dominant aromatic and aliphatic hydrocarbons found in oil sludge. The results of Gas Chromatography-Mass Spectrometry analysis showed that among the tested hydrocarbon sources, Thalassospira can completely remove octadecane and hexadecane, and Chromohalobacter can reduce hexadecane from 15.9 to 9.9%. The bacterial consortium can completely remove octadecane and reduce hexadecane from 15.9 to 5.1%, toluene from 25.6 to 0.6%, and phenanthrene from 12.93 to 6%. According to the obtained results, the bacterial consortium effectively plays a role in the biodegradation of aromatic and aliphatic hydrocarbons, making it a viable solution for treating hydrocarbon pollutants in various environments.

Characteristics of typical intermediate and semi volatile organic compounds in Shanghai during China International Import Expo event.

To ensure good air quality during the China International Import Expo (CIIE) event, stringent emission-reduction measures were implemented in Shanghai. To assess the efficacy of these measures, this study measured typical categories of intermediate/semi volatile organic compounds (I/SVOCs), including alkanes (C10-C26 n-alkanes and pristane), EPA-priority polycyclic aromatic hydrocarbons (PAHs), alkylnaphthalenes, benzothiazole (BTH) and chlorobenzenes (CBs), at an urban site of Shanghai before and during two CIIE events (2019 and 2020; non-CIIE versus CIIE). The average concentrations of alkanes and PAHs during both 2019 and 2020 CIIE events decreased by approximately 41% and 17%, respectively, compared to non-CIIE periods. However, the decline in BTH and CBs was only observed during CIIE-2019. Secondary organic aerosol (SOA) formation from alkanes, PAHs and BTH was evaluated under atmospheric conditions, revealing considerable SOA contributions from dimethylnaphthalenes and BTH. Positive matrix factorization (PMF) analysis further revealed that life-related sources, such as cooking and residential emissions, make a noticeable contribution (21.6%) in addition to the commonly concerned gasoline-vehicle sources (31.5%), diesel-related emissions (20.8%), industrial emissions (18.6%) and ship emissions (7.5%). These findings provide valuable insights into the efficacy of the implemented measures in reducing atmospheric I/SVOCs levels. Moreover, our results highlight the significance of exploring additional individual species of I/SVOCs and life-related sources for further research and policy development.

Correlation of the Molecular Cross-Sectional Area of Organic Monofunctional Compounds with Topological Descriptors.

The molecular cross-sectional area (σ) has proved to be an interesting molecular measure not only in the field of adsorption phenomena on solids but also in biochemistry, physiology, or surfactant chemistry. The existing methods to estimate the cross-sectional areas are either not readily applicable or can only be applied to a limited number of compounds. The aim of this work was to describe a method, as general as possible, quick and easy to perform. To that end, the molecular cross-sectional areas were correlated with topological indices. The Emmett-Brunauer formula was used to calculate the reference cross-sectional areas (σEB) of 431 compounds. The correlations of the Wiener (W), hyper-Wiener (WW), Balaban (J), and Randic (χ) indices with σEB were compared for n-alkanes as well as branched and cyclic alkanes. Only the Wiener and hyper-Wiener indices correlated well with σEB, with the data being best fitted by power law regression curves. The lower degeneracy of the hyper-Wiener index did not translate into any significant gain of performance when correlated with σEB. Following the parsimony principle, the less complex Wiener index was thus selected to correlate with the σEB of compounds representing 31 other monofunctional and structural families. The integration of all the compound families into a single curve allowed a quick rough estimation of the cross-sectional areas. The specific reference equations σEB = qWp were determined for the 34 selected families, allowing the fast and reliable calculation of the cross-sectional area of any monofunctional compound.

Viscosities and Densities of Binary and Ternary Mixtures of Aliphatic and Polyaromatic Hydrocarbons: Pyrene +1-Methylnaphthalene + Dodecane at T = (293.15 to 343.15) K. Experiment and Modeling.

This work presents new experimental viscosity and density data for aromatic and polyaromatic compounds in binary and ternary pyrene, 1-methylnaphthalene, and dodecane mixtures. The lack of experimental viscosity data for these mixtures requires the development of a new database, which is vital for understanding the behavior of mixtures in more complex systems, such as asphaltenes and fuels. The mixtures proposed in this work have been measured over a temperature range of (293.15 to 343.15) K at atmospheric pressure. Several mixture compositions have been studied at these conditions: 1.0, 2.5, 5.0, 7.5, 10.0, 12.5, and 15.0% pyrene mass fraction. The concentration of pyrene correlates with an increase in the viscosity and density values. At the lowest temperature in binary mixtures, the corresponding values reach 4.4217 mPa·s for viscosity and 1.0447 × 103 kg·m-3 for density, respectively. In ternary mixtures, the introduction of dodecane leads to the lowest maximum values of 3.5555 mPa·s for viscosity and 1.0112 × 103 kg·m-3 for density at the same temperature. The experimental data have been employed for the specific modification of viscosity models. These modifications could facilitate the prediction of the viscosity of mixtures that are more complex than those presented in this work. Various viscosity models have been employed, such as Linear, Ratcliff and Khan, modified UNIFAC-Visco, and Krieger-Dougherty. The settings in the models used reliably reproduce the experiment reliably. However, the Ratcliff model agrees excellently with the experiment, having a low standard deviation (2.0%) compared to other models. Furthermore, a model based on the equation of state of Guo is proposed to predict the viscosity values by modifying the specific parameters and adjusting them to the mixtures proposed in this work. The results from this study are compared to previous work, where pyrene, toluene, and heptane mixtures were analyzed. In this case, we find that the decrease of aggregation grade in the present systems is predicted by the model fixed in this work.

Oil and Organic Liquids Incorporation into Fresh Geopolymer Pastes Using Suitable Quaternary Ammonium Surfactants.

The direct incorporation of low viscosity organic liquids (OL) such as dodecane and tributylphosphate (TBP) into fresh geopolymers (GP) is difficult and generally leads to variable amounts of un-incorporated OL remaining outside the hardened geopolymer. Experimentally, it is observed that a regular torque increase during OL incorporation corresponds to a suitable dispersion of the OL in the form of fine micrometric droplets. This can be obtained for TBP and dodecane by adding a small quantity of quaternary ammoniums salts (QAs) such as cetyltrimethylammonium bromide (CTAB). Shorter alkyl chains QAs, such as hexamethyltrimethylammonium (HMTA) can also be used but with a reduced efficiency. The positive impact of CTAB is then confirmed by the Washburn capillary rise method, showing that the interactions between TBP and CTAB-modified metakaolin are weaker compared to untreated powder. Finally, it is observed that the incorporation of TBP into geopolymer slurries is much easier than the incorporation of dodecane. The low interfacial tension measured between TBP and the activating solution (around 8 mN·m -1 ), contrasting with dodecane (29 mN·m -1 ), explains that the dispersion of TBP droplets in fresh metakaolin suspensions is more efficient.