Propane Concentration Research Articles

Determination of rate constants for a thermoneutral H-abstraction reaction: Allylic hydrogen abstraction from 1,5-hexadiene by allyl radical

Thermoneutral H-abstraction reactions, which involve the abstraction by resonantly stabilized radicals from olefins to form other resonantly stabilized radicals, have recently been found to be important in high-temperature combustion. They will shift the distribution of resonantly stabilized radicals and affect the molecular weight growth kinetics, thus changing the prediction for aromatic species. The present work provides the first experimental study on a typical thermoneutral H-abstraction reaction: C3H5-A + 1,5-C6H10 = C3H6 + C6H9-A (R1). A rapid compression machine, together with a fast sampling technique, was used to study the high temperature kinetics of 1,5-hexadiene. Experimental conditions that can be used to derive the rate constant of R1 were first identified by sensitivity analysis of a kinetic model for 1,5-hexadiene combustion. The concentration of propene was found to be highly sensitive to the rate constant of R1 over the temperature range of 893–1007 K at 25 bar. By fitting the measured propene profiles, the rate constant of R1 was deduced under selected conditions. Furthermore, the concentration profiles of propene in 1,5-hexadiene pyrolysis from a flow reactor measurement by Wang et al. (Fuel 208, 779–790, 2017) and oxidation from a jet stirred reactor measurement by Vermeire et al. (Proc. Combust. Inst. 37, 1091–1098, 2019) were also used to derive the rate constant of R1 over wider temperature ranges. The rate coefficient of R1 was further calculated by ab initio transition state theory, with energies obtained at the level of DLPNO-CCSD(T)/aug-cc-pVTZ//B2PLYP/cc-pVTZ. The theoretical predictions were found to be in good agreement with the experimentally derived rate constants. The final rate coefficient determined is: kR1=15.058×T3.425exp(−14492.073/RT)cm3mol−1s−1(500−2000K), with an estimated uncertainty of a factor of 1.5.

Gaseous emissions from freshly extracted coal in the inert and air atmosphere in terms of natural desorption and early coal oxidation

The paper presents the results of chromatographic analyses of gas desorbed from freshly extracted different rank coal samples both, in the atmosphere of nitrogen and air. Samples in which coal remained in contact with nitrogen had higher concentrations of methane, ethane, propane, carbon dioxide, and hydrogen than in samples with air. On the other hand, samples in air found higher concentrations of carbon monoxide, ethylene, and propylene. When coal was in contact with nitrogen, the gaseous components present in the gas sample under investigation came mainly from natural desorption, whereas when coal was in contact with air, the oxidation of coal also occurred. In the process of natural desorption, mainly methane is emitted into the atmosphere of the mine along with the accompanying saturated hydrocarbons: ethane, propane and carbon dioxide. Diverse desorption of saturated hydrocarbons from the structure of coals results from the heterogeneity of hard coal and different content of hydrocarbons in the coal structure. No clear relationship was found between the content of desorbed hydrocarbons in the gas sample and the physicochemical properties of the tested coals.Carbon monoxide, ethylene and propylene are released as a result of contact of coal with oxygen from the air. The highest values of concentrations of carbon monoxide, ethylene and propylene were determined in gas samples desorbed from coals with the lowest, among the tested ones, degree of metamorphism and easily accessible internal pore structure.

Comparing DPPP fluorescence and UV based methods to assess oxidation degree of krill oil-in-water emulsions

In this study, lipid oxidation evaluation methods were compared for a krill-oil-in-water emulsion system. With this aim, thiocyanate and DPPP (diphenyl-1-pyrenylphosphine) fluorescence methods were comparatively examined to determine primary oxidation products. 2-thiobarbituric acid reactive substances (TBARS), hexanal and propanal formation were also monitored as secondary oxidations products. All oxidation experiments were performed via both auto-oxidation at 45 °C and light-riboflavin induced photooxidation at 37 °C. The results have shown that thiocyanate method was not suitable to measure lipid hydroperoxides by the both in auto- and photo-oxidation systems. On the other hand, fluorescence intensity of samples containing the DPPP probe increased during incubation period which indicates the formation of lipid hydroperoxides could be detected via this method. TBARS, hexanal and propanal concentrations also increased during storage period and the formation kinetics of secondary oxidation products was confirmed that the DPPP fluorescence method was accurate and reliable at different environmental conditions.

Flammability and flame propagation of propane/L-leucine powder hybrid mixtures

The minimum explosible concentration (MEC) and flame propagation behaviors of propane/L-leucine powder hybrid mixtures were experimentally investigated. The results of the experiment demonstrated that the MEC values decreased as the propane concentration increased. Additionally, the findings of the analysis proved that the flame propagation limitation in dust explosions increased with the increase in propane concentration. The results indicated two things. First, the flame speed of stoichiometric propane-air/L-leucine powder hybrid mixtures in the initial period of propagation was almost constant notwithstanding an increase in the L-leucine concentration. Second, the dimensionless flame speed was close to unity because the speed of the hybrid mixture was strongly affected by the propane–air premixed flame speed, although the flame speed increased with the increase in propane concentration. Further, it was found that the separate propagating flames of dust/gas hybrid mixtures had a considerable difference in flame speeds were observed.

The year-round variations of VOC mixing ratios and their sources in Kuytun City (northwestern China), near oilfields

Few studies of volatile organic compounds (VOCs) near oilfields have been performed. Continuous online measurements of 102 VOC species were made for 1 year in Kuytun city (northwestern China), near the Karamay and Tuha oilfields. The total VOC (TVOC) concentrations were high (mean 45.6 ppbv, range 21.9–86.1 ppbv). Alkanes, alkenes, nitrogen- and oxygen-containing VOCs, acetylene, halohydrocarbons, and aromatic compounds contributed 46.6%, 23.7%, 12.9%, 11.8%, 11.4%, and 5.3%, respectively, of TVOC concentrations. TVOC concentration varied markedly by season, and decreased in the order winter, spring, summer, fall. The dominant 11 VOCs (in decreasing concentration order) were acetylene, ethane, propane, carbon tetrachloride, isopentane, ethylene, n-butane, acetone, isobutane, methyl tert-butyl ether, and n-pentane, which contributed 68% of TVOC concentrations. The acetone, acetylene, chloroethylene, ethane, ethylene and benzene concentrations were higher on more-polluted than less-polluted days but the n-butane, carbon tetrachloride, isobutane, isopentane, methyl tert-butyl ether, n-pentane, and propane concentrations were always lower on more-polluted than less-polluted days. A positive matrix factorization model indicated that acetylene was the main VOC emitted through combustion during the heating period but acetylene, halohydrocarbons, and oxygen-containing VOCs emitted by industrial plants were dominant during the non-heating period. Carbon tetrachloride, methyl tert-butyl ether, and propane were the dominant VOCs emitted by petrochemical plants, gasoline-powered vehicles and liquefied petroleum gas, respectively. Air mass back trajectories (72 h) indicated that VOCs were mainly supplied by local and regional sources but clean air from Kazakhstan decreased VOC concentrations when wind came from the northwest at wind speeds higher than scale 5.

Deactivation Kinetics of the Catalytic Alkylation Reaction

A kinetics theory of catalyst deactivation is presented of the solid acid-catalyzed alkylation reaction of isobutane with propylene or butene that gives alkylate, a high octane fuel, as product. The intimate relation between the kinetics network of the reaction, catalyst deactivation kinetics, and residence time distribution is analyzed. The question is addressed why the deactivation of the alkylation reaction in a continuously stirred tank reactor (CSTR) is slow compared to that in a tubular plug flow reactor (PFR). Conditions are derived where such differences will be minimum and maximum. In the reaction regime of high alkylate selectivity, linear and quadratic power law kinetics equations in propylene concentration can be deduced from microkinetics. They are used to derive analytical expressions of deactivation times for CSTR and PFR. The theoretical power law kinetics equations can be related to previously established empirical rate equations of catalyst deactivation. We show that, in the CSTR, the self-alkylation reaction path contributes substantially to the deactivation time. In the self-alkylation reaction, alkylate is formed by reaction of the isobutene reaction intermediate and isobutane. Catalysts of high proton strength can benefit catalyst deactivation times by suppressing the carbenium ion deprotonation reaction that produces alkenes as isobutene. In the PFR, selective alkylate formation occurs only when the reaction occurs in a reaction zone of the catalyst bed. Deactivation is faster than in CSTR because of the reactant profile in the reaction zone. This reaction zone has restricted mobility due to the fast deactivation of reactive protons located behind the reaction zone by alkenes formed by nonselective reactions in the reaction zone. In PFR, as long as the reaction is limited to an immobile reaction zone, deactivation time is independent of reaction site density and contact time. Contact time dependence arises when the reaction zone is mobile. Overall deactivation time then depends strongly on the degree of deactivation of the protons behind the reaction zone.

Nanocrystalline Co3O4 catalysts for toluene and propane oxidation: Effect of the precipitation agent

A set of cobalt oxide catalysts was prepared via precipitation using various precipitants and evaluated in the total oxidation of toluene and propane. A commercial Co3O4 catalyst was used as a reference. Various techniques were used to characterize the catalysts before and after testing. The results showed that the physicochemical properties and the catalytic performance of these cobalt oxide catalysts were greatly influenced by the nature of the precipitation agent used upon preparation. All catalysts exhibited a Co3O4 cubic spinel structure, with different crystallite sizes (27–41 nm) and specific surface areas (15–40 m2 g−1). The optimal catalyst, obtained via carbonate-precipitation and named Co-CO3, achieved 90 % toluene and propane conversion at 256 and 226 °C, respectively. This Co-CO3 catalyst performed better than the commercial catalyst in the toluene oxidation and similarly to the commercial one in the propane oxidation. All catalysts maintained constant performance upon three consecutive catalytic cycles; however, they deactivated to a different extent upon longer-term stability tests depending on the molecule to be oxidized. In toluene oxidation, Co-CO3 exhibited good stability upon cycling but a poor long-term durability. To overcome this issue, a dual-bed catalytic system was proposed. In propane oxidation, Co-CO3 showed stable performance in both cases. The effects of propane and oxygen concentrations on the catalytic performance of Co-CO3 in propane oxidation were also investigated. A positive reaction order with respect to oxygen and the results of oxygen-free catalytic test revealed the dominant role of chemisorbed oxygen species in the oxidation of propane. The excellent performance of Co-CO3 was tentatively ascribed to the highly strained nanocrystalline structure, the high concentration in Co2+ and the superior reducibility.

Auto-ignition performance of an electrified microreactor with constructal geometries

Common techniques employed to minimize ignition energy of gaseous fuels in micro reactors such as the use of catalyst are being plagued with setbacks. This report demonstrates the use of electric field to sustain combustion, minimize heat loss and enhance reactant mixing in microchannels of varying geometries. We set two defining constructal parameters for serpentine and straight microchannels of 0.05 to 0.25 to investigate geometric effect on the mixing of the reactants. Inlet concentration of propane and oxygen was set at 0.15 mol/dm3 and 0.7 mol/dm3 respectively. Reynolds numbers 400, 470, 530, 600 and 670 corresponding to inlet velocities of 0.06 m/s, 0.07 m/s, 0.08 m/s, 0.09 m/s and 0.1 m/s were used in the straight channel to study the dependence of reaction rate, temperature drop and reactants diffusion on the combustion process. We report that at an inlet temperature of 500 K which was below the propane’s auto ignition temperature of 743 K, the reaction could occur in the presence of a 50 V applied voltage. Increasing constructual parameter (β) yielded an increase in reaction rate and a decrease in temperature drop. At the same constructual parameter, the serpentine geometry displayed a better result with the peak reaction rate of 894 mol/m3s. More so, increase in the Reynolds number and shape factor for the two geometries led to an increase in reaction rate and propane consumption. These findings could be suitably beneficial to provide minimal fuel requirement for miniaturized vehicles and micro-heat engines.

Tea catechin role in decreasing the oxidation of dairy beverages containing linseed oil.

Dairy beverages containing emulsified linseed oil is a suitable vehicle for delivering polyunsaturated fatty acids to consumers. However, these beverages are prone to oxidation. The purpose of this study was to evaluate the effect of adding various concentrations (0, 0.001, 0.01 and 0.1% (w/w)) of green tea extract (GTE) to dairy beverages (DB) containing linseed oil (2.0%, w/w), in order to inhibit lipid oxidation during storage at high temperature (50°C) or under fluorescent light exposure. During storage, the concentration of catechin (C), epicatechin (EC) and epicatechin gallate (ECG) were significantly reduced (P ≤ 0.05) and degradation rate was greater when the DB were exposed to light (C 35%, EC 74% and ECG 68%) as compared to high temperature (C 34%, EC 45% and ECG 49%). In DB without GTE, the conjugated dienes (CD) hydroperoxides concentration increased significantly (P ≤ 0.05) from 23 mmol kg-1 fat to 243 mmol kg-1 fat under 6-day-light exposition, and to 83 mmol kg-1 fat under 6-day-heat temperature. The addition of GTE significantly increased the antioxidant capacity of DB and reduced the formation of CD, propanal and hexanal, induced by light exposure or high temperature. GTE at 0.10% completely inhibited CD formation during the storage period and reduced propanal and hexanal concentrations below the threshold.

Dynamic modeling: The influence of the improved solid elutriation correlation on the two‐phase mathematical model of polyolefin polymerization in a gas‐phase fluidized bed reactor

AbstractDynamic modeling of the polyolefin polymerization process in the gas phase is relatively complex due to its high nonlinearity. This nonlinearity is induced by several factors including the reaction mechanism, the heat and mass transfer mechanism, the flow properties in both solid and gas phases, the type of reactor, and the correlations between the operating conditions and the chemical and physical properties of the polyolefin. In this study, polymerization of the polypropylene was observed in a fluidized bed reactor to potentially improve the solid elutriation correlations proposed previously, to increase the reliability and the accuracy of this two‐phase model. By embedding the improved solid elutriation correlations, the production rate was reduced relative to earlier proposed solid elutriation correlations due to the loss of the product at the top of the fluidized bed reactor. The composition of the reactants and the catalyst flow rate also influenced the production rate, yet the inlet temperature did not. The current two‐phase model is validated with the pilot plant data with the deviations lower than the previously validated model with reference to the production rate, the concentration of propylene and hydrogen, and the temperature of the reactor.

Direct laser hardening of AISI 1020 steel under controlled gas atmosphere

Laser hardening is usually performed in air. Use of a controlled gas atmosphere might produce a direct reaction of the gas with surface and thus provide an opportunity to engineer the surface microstructures. However, few studies are reported on direct gas-assisted laser hardening process. In this paper, a direct gas-assisted laser hardening is demonstrated on AISI 1020 steel using an ytterbium-doped fiber laser in presence of four different gases – air, argon, carbon dioxide and propane. All hardening trials were conducted at same laser parameters and only the gas was changed to evaluate its effect on hardness and microstructure of the steel. Results show that argon had slightly higher hardening effect than air as it prevents surface oxidation. Propane produced a very high surface hardness (914 HV) compared to conventional laser hardening process (395 HV). The ultrahigh hardness is due to diffusion of carbon into steel from decomposed propane. Increasing the concentration of propane contributed to an increment in hardness primarily due to large amount of carbides in near surface region. Contrarily, carbon dioxide yielded a lower surface hardness (350 HV) despite its high carbon content. This is attributed to the oxidizing effect of carbon dioxide, which produces decarburization during laser processing. The study reveals the potential of using direct gas-assisted laser hardening technique to alter surface mechanical properties of steel.

Pyrolysis of Waste Palm Oil in the Presence of Steam

This work ranges among studies dedicated to valorization of waste vegetable oils. In the present study, the pyrolysis of the waste palm oil was performed in presence of steam, in a tubular pyrolysis reactor operated in a continuous mode. The raw used in the pyrolysis reaction is the frying waste palm oil and the reactor was operated at high temperature (575 -625°C) and reaction time of 72s and 144s, at a steam: oil ratio of 0.1 -0.2. Valuable compounds such as olefins (ethylene, propylene) were obtained in the process, and they can be used further as raw materials in the chemical and petrochemical industry. The gaseous product resulted contained high ethylene and propylene concentrations: 18.89 - 25.5% and 13.33-15.05%, respectively. Based on the experimental results, some linear equations were developed to predict the products yields, and the coefficients of the model were statistically verified. These equations can serve at scaling up the pyrolysis process. Keywords: Steam cracking, vegetable oil pyrolysis, yield prediction, mathematical model

Pressure coring a Gulf of Mexico deep-water turbidite gas hydrate reservoir: Initial results from The University of Texas–Gulf of Mexico 2-1 (UT-GOM2-1) Hydrate Pressure Coring Expedition

The University of Texas Hydrate Pressure Coring Expedition (UT-GOM2-1) recovered cores at near in situ formation pressures from a gas hydrate reservoir composed of sandy silt and clayey silt beds in Green Canyon Block 955 in the deep-water Gulf of Mexico. The expedition results are synthesized and linked to other detailed analyses presented in this volume. Millimeter- to meter-scale beds of sandy silt and clayey silt are interbedded on the levee of a turbidite channel. The hydrate saturation (the volume fraction of the pore space occupied by hydrate) in the sandy silts ranges from 79% to 93%, and there is little to no hydrate in the clayey silt. Gas from the hydrates is composed of nearly pure methane (99.99%) with less than 400 ppm of ethane or heavier hydrocarbons. The δ13C values from the methane are depleted (−60‰ to −65‰ Vienna Peedee belemnite), and it is interpreted that the gases were largely generated by primary microbial methanogenesis but that low concentrations of propane or heavier hydrocarbons record at least trace thermogenic components. The in situ pore-water salinity is very close to that of seawater. This suggests that the excess salinity generated during hydrate formation diffused away because the hydrate formed slowly or because it formed long ago. Because the sandy silt deposits have high hydrate concentration and high intrinsic permeability, they may represent a class of reservoir that can be economically developed. Results from this expedition will inform a new generation of reservoir simulation models that will illuminate how these reservoirs might be best produced.

A Variable-Potential Amperometric Hydrocarbon Sensor

Using the understanding of an inexpensive production NOx sensor, the operating parameters are changed to enable hydrocarbon measurement using the same sensor. A limiting-current-type amperometric hydrocarbon sensor for rich conditions (in the absence of O2) is developed in this work. To do this, an inexpensive three-chamber amperometric sensor with three separate electrochemical cells is parameterized to measure propane concentration. The sensor is tested using a controlled sensor test rig at different propane concentrations. The inputs to the sensor electrochemical cells have been modified to determine the best HC measurement parameters (HCMPs) for measuring propane at different concentrations. First, the transient performance and stability of the sensor are optimized by changing the sensor temperature, the reference cell potential, and the stabilizing cell potential at a high propane concentration (5000 ppm - balanced with nitrogen). Over the range tested, the sensor has the longest stable output duration at the temperature of 1009 K, the reference cell potential of 0.67 V and the stabilizing cell potential of 0.45 V. Using these sensor inputs for sensor temperature, reference cell potential and stabilizing cell potential, the sensor steady state behavior is studied to find the diffusion-rate-determined operating region. The sensor is shown to have a linear sensitivity to propane concentration from 0 to 3200 ppm. Finally, the sensor response time to different step changes from 0 up to 5000 ppm propane concentration are studied. It is shown that propane stepsize does not have a significant effect on the sensor response time. Consequently, using the working principles of an existing production amperometric NOx sensor and changing the sensor operating parameters, an amperometric hydrocarbon sensor that works in diffusion rate determining operating region is developed.

Каталитическая трансформация диметилового эфира в углеводороды на железо модифицированном цеолите H-ZSM-5

Decrease of traditional hydrocarbon feed stock stimulates a widespread interest in the development hydrocarbons synthesis from renewable or low-value sources. The catalytic transformation of methanol into hydrocarbons, along with the Fischer–Tropsch process, can be considered as a possible way to obtain synthetic hydrocarbons. At the same time, the activity and stability of the catalysts have a decisive influence on the efficiency of the whole process. Zeolites and zeotypes of various structures traditionally used as catalysts are characterized by low rates of hydrocarbon accumulation and a short period of functioning, which requires a change in their structural characteristics or the synthesis of new systems. The aim of this work is to obtain iron-modified H-ZSM-5 type zeolites in order to increase the rate of liquid hydrocarbons accumulation and increase the lifetime of the catalyst. To achieve this goal zeolite was modified with iron, the main physicochemical characteristics of the obtained catalysts were determined and the catalytic properties were screened. Modification of zeolites by iron was carried out by the ion exchange method, as a result samples with an iron content of 0.004 wt.% to 0.240 wt.% were synthesized. In this case the decrease in the micropores surface from 280 m2/g to 190 m2/g and decrease in the number of acid sites from 1.08 mmol/g to 0.72 mmol/g was noticed. Modification of zeolite with iron of concentration up to 0.008 wt. % contributed to an increase in transformation rate of dimethyl ether from 0.04 to 0.06 kg (DME)/(kg (Cat)h) and decreace to 0.03 kg (DME)/(kg (Cat) h) during further increasing of iron content, however process selectivity to liquid hydrocarbons increase from 30% to 54%. Modification of zeolite with iron contributes to a significant change in hydrocarbon composition. With an increase in the iron concentration from 0.004 wt.% to 0.017 wt.%, the increase in the concentration of propane, butane and aliphatic hydrocarbons with the number of carbon atoms of six or more was noticed along with a decrease in the concentration of aromatic compounds.

Hydrocarbon gases in seafloor sediments of the TATAR strait, the northern sea of Japan

The distributions of hydrocarbon gases (HCGs) from C1-C5 in seafloor sediments of the South Tatar sedimentary basin (northern Sea of Japan) were obtained during five research cruises from 2012 to 2017. As a result of this work, areas of gas hydrates, gas flares, and anomalous gas concentrations were discovered. The concentration of HCGs in seafloor sediment, as determined by the “headspace method” varied from 0.38 to 149,000 ppm, with a median of 177 ppm (N = 1420). The median values of HCGs for the Western, Central, and Eastern part of the South Tatar sedimentary basin are 11.7, 99, and 1134 ppm, respectively. Maximum values and gradients in concentrations of HCGs were found in the central and eastern parts of Tatar Strait, where multiple cores contain gas hydrates and gas-saturated sediments. The predominant gas component in all samples was methane, but relatively high concentrations of ethane (up to 789 ppm) and propane (up to 111 ppm) occur. Methane concentrations below 5.25 ppm can be considered as regional background for near seafloor (0–15 cm) sediments from the South Tatar sedimentary basin. The С1/(С2 + С3) ratio across all samples ranges between 2.6 and 345,000, with a median value of 219. The presence of a large-scale degassing zone exists in the northeastern part of Tatar Strait, which coincides with areas of gas hydrates and gas anomalies in the sediments and gas flares in the water column.

Effect of the Volumetric Flow Rate of Reaction Mixture Components on Nonoxidative Reforming of Methane with Admixed Water in Dielectric-Barrier Discharge

The effect of the volumetric flow rate of reaction mixture components on the nonoxidative reforming of methane with admixed water in dielectric-barrier discharge has been studied. An increase in the volumetric flow rate of water from 1.3 to 6 cm3/h did not exert a noticeable effect on the conversion of methane and on the concentrations of hydrogen and ethane in gaseous reaction products. An increase in the concentration of propane and butanes was observed, whereas the total ethylene and propylene content of the products decreased. An increase in the volumetric flow rate of methane from 5 to 60 cm3/min led to a decrease in the conversion of methane from 29.3 to 6.2 vol % and a decrease in energy consumption for its reforming from 88.3 to 34.7 eV/molecule, and it was also accompanied by a decrease in the rate of formation of gaseous alkanes and olefins. The experimental data confirmed previous conclusions on the reaction mechanism and kinetics of the nonoxidative reforming of methane in dielectric-barrier discharge, which were made using a mathematical model.

Methanogenesis and secondary processes in a fractured claystone aquifer influenced by a former landfill site: Implications for the interpretation of dissolved gases

Similar to marine and/or freshwater sediments, dissolved methane and longer chained hydrocarbons are ubiquitous in all natural groundwater environments including highly productive porous aquifers. The isotopic and chemical characteristics of dissolved gases in groundwater related to municipal landfills commonly differ from other non-polluted environments. In the survey presented in this study we investigated the geochemical and isotopic variations of dissolved hydrocarbons in a unique study area with different well defined ecological micro-habitats influenced by a former landfill for industrial and special waste. The dissolved methane concentrations have generally remained stable over the last decade but vary by several orders of magnitude in different zones of the area. The dominant methanogenic pathways can be clearly distinguished in the different ecosystems. Methyl-type fermentation methanogenesis prevails in the shallow groundwater zone (5–15 m depth) in- and outside the landfill. Anaerobic methane oxidation coupled to sulfate reduction occurs in the shallow downstream area within a former leachate plume. At larger depths CO2 reduction is the predominant methane formation pathway except within the physically isolated landfill site. The high ethane concentrations in a small part of the study area are potentially related to the degradation of volatile organic compounds. The background ethane concentrations are higher in the deeper groundwater zones, indicating the coupling to the CO2 reduction methanogenic pathway. The propane concentrations in most wells are below the detection limit, except within the waste site.Secondary methane oxidation, which frequently occurs in the groundwater in all environments can alter the gas composition mimicing the thermogenic gas signature in the standard Bernard-diagram. The isotopic fractionation between co-existing methane and formation water and carbon dioxide, respectively, differs from that suggested in standard interpretational diagrams (e.g. Bernard-Diagram and Whiticar-plots). Thus, the standard evaluation based on methane hydrogen and carbon isotopes is also susceptible to an erroneous interpretation as non-biogenic dissolved gases in other groundwater environments.

Distribution of Short-chain Aliphatic Aldehydes in the Gastrointestinal Tract of Pigs (P06-033-19)

ObjectivesThe presence of short-chain aliphatic aldehydes (SCAAs), including acetaldehyde, propanal, butanal, and pentanal, in food has been detected. In addition, the production of SCAAs in the alimentary digestion of food has also been observed. However, the distribution of these SCAAs in the gastrointestinal tract (GIT) has not been defined previously. This study aimed to examine the distributions of SCAAs and their corresponding short chain fatty acids (SCFAs) in the GIT of pigs. MethodsDigesta samples were collected from the stomach, duodenum, jejunum, ileum, cecum, and rectum of 14 finishing barrows fed corn-soybean meal. The SCAAs and SCFAs in these samples were quantified by the liquid chromatography-mass spectrometry analysis, and their distribution in the GIT was further modeled by principal components analysis. ResultsSCAAs were far more abundant in the upper GIT than the lower GIT, with the highest concentrations of acetaldehyde and propanal in the stomach and the highest concentrations of butanal and pentanal in the duodenum and jejunum. In contrast, SCFAs were mainly present in the lower GIT, especially in the large intestine. ConclusionsThe digestive activities in the upper GIT can produce significant amounts of SCAAs, which were mostly eliminated in the lower GIT. The converse distribution patterns of SCAAs and SCFAs in the GIT suggested that some SCAAs may be oxidized into SCFAs in the large intestine through microbial metabolism. Funding SourcesThis study is partially supported by the AES project MIN-18-092.

Characterisation of the Carpinus betulus L. Phyllomicrobiome in Urban and Forest Areas.

Urban green areas are highly valued by citizens for their contribution to the quality of life in cities. Plants play an important role in mitigating airborne pollutants and are assisted in this role by the metabolic capacities of the millions of microbial cells that colonize leaf surfaces (phyllosphere). Many factors influence phyllosphere microbial community composition and function, but to what extent does airborne pollution in cities impact the composition of microbial communities and their functional degradation genes? Here we describe the characterization of the phyllospheric bacterial communities of Carpinus betulus L. trees (hornbeam) across three locations: the city center of Warsaw (Poland), a forest in a UNESCO World Heritage Site (Białowieża), and a forest in one of the world’s oldest operational oil fields (Bóbrka). C. betulus contained higher particulate matter (PM) concentrations, with higher concentrations of palladium and radon in the PM, on leaves in Warsaw than in the forests. Volatile organic compound (VOC) analyses of sampled air revealed higher concentrations of butanone methyl propanal, butylbenzene, and cyclohexane in Bóbrka than Warsaw and Białowieża, while in Warsaw, xylene and toluene were higher. Shotgun microbiome sequencing uncovered a dominance of Gammaproteobacteria (71%), mainly Pseudomonas spp., Actinobacteria, Alpha- and Betaproteobacteria, and Firmicutes. Community composition and function differed significantly between the forests and Warsaw city center. Statistically more hydrocarbon degradation genes were found in Białowieża compared to Warsaw and Bóbrka, and in vitro tests of diesel degradation and plant growth promotion traits of culturable representatives revealed that Białowieża held the highest number of bacteria with plant beneficial properties and degradation genes. This study provides the first detailed insights into the microbiome of C. betulus and sets the stage for developing to a more integrated understanding of phyllosphere microbiota in cities, and their relationships with human health.