Volatile Hydrocarbons Research Articles

Bioelectrochemical assisted dechlorination of tetrachloroethylene and 1,2-dichloroethane by acclimation of anaerobic sludge

Volatile chlorinated hydrocarbons (VCHs) are often found as a type of persistent and ubiquitous contaminant in groundwater. The feasibility, characteristics and microbial mechanism of acclimation of biodiversity-rich inoculation source for bioelectrochemical stimulated VCH dechlorination remain poorly understood. Here, the superior bioelectrochemical catalytic activities were observed for tetrachloroethylene (0.26 mM d−1) and 1,2-dichloroethane (2.20 mM d−1) dechlorination in anaerobic sludge-acclimated biocathodes with an optimal potential of −0.5 V, averaging 1.60–2.71 times higher than those reported in previous works on biocathodes. When the cathode was applied as the sole electron donor for dechlorination, columbic efficiencies reached the values greater than 80%. Tetrachloroethylene dechlorination showed a metabolic pathway with cis-1,2-dichloroethene as the main product, whereas 1,2-dichloroethane was dechlorinated entirely to the nontoxic ethene. The cathodic biofilms were highly abundant with the dechlorination and electro-active genera, while significant bacterial consortium variation was observed in response to the different VCH types and changes in cathodic potential. Bacillus, Pseudomonas and Lactococcus were mostly enriched for tetrachloroethylene dechlorination, and pceA, tceA and omcX were highly expressed. Geobacter was the most predominant during 1,2-dichloroethane dechlorination with rdhA, tceA and omcX highly expressed. In addition, although the impact of cathodic potentials was weaker than that of VCH types, the lower cathodic potentials, the more abundant of the electrode respiring populations and the higher expression of extracellular electron transfer related gene. This study demonstrated the great potential of acclimation of anaerobic sludge by electrical stimulation for accelerating VCH remediations and gave insights into its working molecular mechanisms.

Pyrolysis of aquatic carbohydrates using CO2 as reactive gas medium: A case study of chitin

Here in this study, the thermolysis of aquatic biopolymer (i.e., chitin) was mainly investigated as a strategic means for reinforcing the insecure supply chains of terrestrial biomass. To maximize carbon utilization in the carbon substrate and establish a sustainable pyrolysis platform, this study particularly employed CO2 as reactive gas medium. To this end, this study laid great emphasis on elucidating the mechanistic role of CO2 in pyrolysis of chitin. For the fundamental study, the thermolysis of chitin in CO2 in reference to the case in N2 was characterized thermo-gravimetrically. A series of the TGA tests signified that the homogeneous reactions between solid-state chitin and CO2 should be excluded. However, a lab-scale pyrolysis of chitin in CO2 demonstrated that CO2 enhanced thermal cracking of the volatile hydrocarbon species from the thermolysis of chitin. In parallel, CO2 reacted with the volatile hydrocarbon species to form CO. To justify such genuine mechanistic roles of CO2, two-stage pyrolysis of chitin was conducted, and all experimental findings strongly supported the genuine mechanistic roles of CO2.

Sediment geochemical study of hydrocarbon seeps in Isfjorden and Mohnbukta: a comparison between western and eastern Spitsbergen, Svalbard

Methane is the most widespread volatile hydrocarbon and one of the most potent greenhouse gases. Marine sediments form the largest methane reservoir, from where large quantities of methane from gas-saturated sediments are released into the sea water and into the shallow shelf seas, through the water column almost unaltered into the atmosphere. Craters on the sea floor known as pockmarks are often related to seepage of methane-rich fluids originating either from shallow (microbial) or deep (thermogenic) sources. This paper presents the geochemical characteristics of migrating hydrocarbon gas from selected pockmarks and surrounding seabed in Isfjorden and Mohnbukta in western and eastern Spitsbergen, respectively. Collected gas samples, including wet gas fraction, were analyzed for methane concentration and methane carbon stable isotope ratio. Mixtures of microbial and thermogenic methane, together with higher homologies were found in the pockmarks as well as in the adjacent undisturbed seafloor, suggesting that the seepage activity in both areas is currently on the same level. Although the methane concentration profiles and methane stable carbon isotope ratios in Isfjorden and Mohnbukta show signs of biological oxidation and elevated concentrations of ethane/propane indicate input from deeper thermogenic sources. The gas composition and methane carbon stable isotope ratio from Isfjorden and Mohnbukta areas show similar trends, most likely due to originating in the same Mesozoic organic-rich marine mudstone.

The unique features of non-competitive vs. competitive sorption: Tests against single volatile aromatic hydrocarbons and their quaternary mixtures

The adsorption characteristics of four aromatic hydrocarbons (i.e., benzene, toluene, xylene, and styrene) onto ground-activated carbon were investigated both independently and as a mixture of the four at <10 Pa partial pressures (e.g., 0-100 ppm concentration range). The maximum sorption capacities for benzene, toluene, styrene, and xylene were measured both as a sole component and as a mixture (at 10 Pa). In the former, the values were approximately 123, 184, 272, and 238 mg g-1, respectively. In contrast, the latter values were 5, 52, 222, and 248 mg g-1 respectively, showing dramatic reduction in lighter compounds (below C7) relative to heavier ones (above C8). The mechanistic detail of sorption has been explained in terms of Henry's law and Langmuir, Freundlich, Dubinin-Radushkevich, and Elovich isotherm models. The linearized Langmuir adsorption isotherm analysis showed three sorption pressure regions: low (<1 Pa, retrograde), intermediate (1-4 Pa), and high (4-10 Pa). As such, the outcome of this study offers a unique opportunity to acquire detailed information on the dramatic and dynamic effects of the sorptive interaction between competing sorbates, along with a common sorption process between sorbent and sorbate at 298 K.

Marine Transform Faults and Fracture Zones: A Joint Perspective Integrating Seismicity, Fluid Flow and Life

Marine transform faults and associated fracture zones (MTFFZs) cover vast stretches of the ocean floor, where they play a key role in plate tectonics, accommodating the lateral movement of tectonic plates and allowing connections between ridges and trenches. Together with the continental counterparts of MTFFZs, these structures also pose a risk to human societies as they can generate high magnitude earthquakes and trigger tsunamis. Historical examples are the Sumatra-Wharton Basin Earthquake in 2012 (M8.6) and the Atlantic Gloria Fault Earthquake in 1941 (M8.4). Earthquakes at MTFFZs furthermore open and sustain pathways for fluid flow triggering reactions with the host rocks that may permanently change the rheological properties of the oceanic lithosphere. In fact, they may act as conduits mediating vertical fluid flow and leading to elemental exchanges between Earth’s mantle and overlying sediments. Chemicals transported upward in MTFFZs include energy substrates, such as H2 and volatile hydrocarbons, which then sustain chemosynthetic, microbial ecosystems at and below the seafloor. Moreover, up- or downwelling of fluids within the complex system of fractures and seismogenic faults along MTFFZs could modify earthquake cycles and/or serve as “detectors” for changes in the stress state during interseismic phases. Despite their likely global importance, the large areas where transform faults and fracture zones occur are still underexplored, as are the coupling mechanisms between seismic activity, fluid flow, and life. This manuscript provides an interdisciplinary review and synthesis of scientific progress at or related to MTFFZs and specifies approaches and strategies to deepen the understanding of processes that trigger, maintain, and control fluid flow at MTFFZs.

The Photodynamic Properties and the Genotoxicity of Heat-Treated Silicalite-1 Films.

We investigated the use of a supported silicalite-1 film (SF) as a promising coating for metallic materials used in the fabrication of prostheses. The role of carbonaceous residua present on high-temperature calcined-SF in generating singlet oxygen for future use as a sterilization method has also been addressed, and the potential genotoxicity of these residua in osteoblast-like cells has been investigated. Calcination of as-synthesized SF induced the appearance of a rather complicated mixture of aliphatic and aromatic species on its outer surface. A series of variously volatile polycyclic aromatic hydrocarbons (PAH), including naphthalene, fluorene, phenanthrene, anthracene, fluoranthene, and pyrene, were identified in micromole concentrations. Irradiation of these PAHs on calcined-SF immersed in air-saturated chloroform led to the formation of very low concentrations of singlet oxygen. However, an increased level of DNA damage was observed on calcined-SF by immunofluorescence staining of phosphorylated histone H2AX analyzed by flow cytometry.

Associations between environmental pollutants and larval amphibians in wetlands contaminated by energy-related brines are potentially mediated by feeding traits

Energy production in the Williston Basin, located in the Prairie Pothole Region of central North America, has increased rapidly over the last several decades. Advances in recycling and disposal practices of saline wastewaters (brines) co-produced during energy production have reduced ecological risks, but spills still occur often and legacy practices of releasing brines into the environment caused persistent salinization in many areas. Aside from sodium and chloride, these brines contain elevated concentrations of metals and metalloids (lead, selenium, strontium, antimony and vanadium), ammonium, volatile organic compounds, hydrocarbons, and radionuclides. Amphibians are especially sensitive to chloride and some metals, increasing potential effects in wetlands contaminated by brines. We collected bed sediment and larval amphibians (Ambystoma mavortium, Lithobates pipiens and Pseudacris maculata) from wetlands in Montana and North Dakota representing a range of brine contamination history and severity to determine if contamination was associated with metal concentrations in sediments and if metal accumulation in tissues varied by species. In wetland sediments, brine contamination was positively associated with the concentrations of sodium and strontium, both known to occur in oil and gas wastewater, but negatively correlated with mercury. In amphibian tissues, selenium and vanadium were associated with brine contamination. Metal tissue concentrations were higher in tadpoles that graze compared to predatory salamanders; this suggests frequent contact with the sediments could lead to greater ingestion of metal-laden materials. Although many of these metals may not be directly linked with energy development, the potential additive or synergistic effects of exposure along with elevated chloride from brines could have important consequences for aquatic organisms. To effectively manage amphibian populations in wetlands contaminated by saline wastewaters we need a better understanding of how life history traits, species-specific susceptibilities and the physical-chemical properties of metals co-occurring in wetland sediments interact with other stressors like chloride and wetland drying.

An improved neural network for TOC, S1 and S2 estimation based on conventional well logs

Total organic carbon (TOC), volatile hydrocarbon (S1) and remaining hydrocarbon (S2) are significant factors for shale oil and gas exploration and development. However, the TOC, S1 and S2 estimations are considered as challenges for the geological engineers because the direct laboratory method is time consuming and costly. Passey method and back propagation artificial neural network (BPANN) based on well logs have been extensively employed to determine organic richness. However, the prediction accuracy of Passey method is low, and BP neural network is easily trapped into local optimum. Hence, in this paper, for the first time, we propose a six-layer convolutional neural network (CNN) model in the field of deep learning to address these challenges. CNN is characterized by local connections, weight sharing and convolution kernels. These merits enable CNN to mitigate overfitting and provide higher prediction accuracy and better generalization ability than the traditional neural network.Specifically, 125 core shale samples and well logging data of Shahejie Formation from Dongying Depression, Bohai Bay, China were split into 100 training samples and 25 validating samples to evaluate the proposed CNN for predicting TOC, S1 and S2. Moreover, we made a correlation between TOC S1, S2 and well logs to choose the suitable input. All logging attributes and selected logging attributes were used as inputs respectively for comparison. The experimental results demonstrate that the new technique CNN model outperforms the available methods in calculating the TOC, S1 and S2, which indicates the feasibility of this method. Besides, the prediction accuracy with selected logs as input is higher than that of with all logs as input, which illustrates that making a correlation between well logs and TOC, S1, S2 to choose appropriate logs is helpful for improving prediction accuracy.The proposed CNN model allows organic richness (TOC, S1 and S2) to be precisely calculated based on conventional well logs.

“Diseño de un Sistema de Producción de CO2 para Consumo Humano a partir de las emisiones Generadas en un Relleno Sanitario”

“Diseño de un Sistema de Producción de CO2 para Consumo Humano a partir de las emisiones Generadas en un Relleno Sanitario” Quispe Solano Roldan Heivis UNIVERSIDAD NACIONAL DEL CALLAO, CENTRO DE ESTUDIO E INVESTIGACION DEL MEDIO AMBIENTE-CEIMA, Av. Juan Pablo II 306, Bellavista – Callao Teléfono: (051) 988062555 – RPM:*221029 DOI: https://doi.org/10.33017/RevECIPeru2011.0020/ RESUMEN El presente proyecto se pretende demostrar que las emisiones generadas en un relleno sanitario que contaminan el ambiente, pueden ser aprovechadas para obtener CO2 de alta pureza para consumo humano; en cantidades suficientes como para cubrir una parte de la creciente demanda de un mercado cada vez más exigente, actualmente viene siendo un problema cada vez más crítico la generación de emisiones en el planeta produciendo el calentamiento global. Para llegar al objetivo, se diseñara un sistema de captura y recuperación gases emitidos por la reacción y descomposición de los residuos sólidos para producir CO2 de alta pureza para consumo humano, con el fin de optimizarlo para las condiciones propias del lugar. Los gases serán capturados en un tanque de almacenamiento siendo enfriado a temperatura ambiente, luego será quemado con aire del ambiente, purificado, comprimido, secado, licuado y almacenado. El CO2 obtenido será analizado para determinar el grado de pureza del CO2 y de otros gases (O2, N2, Stotal, C2H4O, CO, hidrocarburos Volátiles como metano, olor, sabor y apariencia en agua). Palabras clave: Sistema de recuperación de CO2, producción de CO2. ABSTRACT This project aims to demonstrate that the emissions generated in a landfill polluting the environment, can be exploited to obtain highly pure CO2 for human consumption in quantities sufficient to cover part of the growing market demand for increasingly demanding, an issue currently is being increasingly critical generation of emissions on the planet causing global warming. To reach the objective, design a recovery system for capturing and gases emitted by the reaction and decomposition of solid waste to produce high purity CO2 for human consumption in order to optimize the conditions of the place. The gases will be captured in a storage tank being cooled to room temperature, then be burned with ambient air, purified, compressed, dried, liquefied and stored. The CO2 obtained will be analyzed to determine the purity of CO2 and other gases (O2, N2, Stotal, C2H4O, CO, volatile hydrocarbons such as methane, odor, taste and appearance in water). Keywords: CO2 recovery system, CO2 production.

Factors influencing volatile hydrocarbon pollution in urban areas

Volatile hydrocarbons in urban environments pose significant risks to human and ecosystem health, resulting from wash-off into receiving waters during storm events. Effective mitigation strategies require understanding of the significance of contributing factors to pollutant generation and their processes. This study employed Bayesian Network modelling to investigate how anthropogenic and environmental factors influence volatile hydrocarbons build-up. The volatile hydrocarbons investigated were, benzene, toluene, ethylbenzene and xylene and styrene. Most volatile hydrocarbons showed statistically significant relationships with environmental factors rather than with anthropogenic factors. Additionally, the research study found that anthropogenic factors could largely contribute to releasing volatile hydrocarbon into the urban environment, while environmental factors are likely to determine their prevalence. The research outcomes will contribute to improving stormwater quality modelling approaches and strengthen the assessment of risk associated with stormwater pollutants in order to enhance stormwater reuse.

Childhood Poisoning Cases Admitted to Zagazig University Hospitals during the Year 2018: A Retrospective Study

Background: Childhood poisoning is considered major socioeconomic and public health problem as there are thousands of children admitted to the emergency departments and millions of calls are made to poison control centers every year. Aim of the Work: Determine the prevalence and pattern of childhood poisoning cases admitted to Zagazig University hospitals. Subjects and Methods: This is a retrospective study on children < 18 years old presented to Zagazig University hospital emergency department. The study was done from the beginning of January 2018 to the end of December 2018 on total of 624 cases with acute poisoning. All required epidemiological and clinical data were collected and analyzed. Results: A total of 624 childhood poisoning cases, more males than females (55.3% versus 44.7% respectively), and more in age group of 3 - 6 years old (40.86%), more in rural than urban communities (65.06% against 34.94% respectively). Oral exposure was the most against other routes (84.94%). Most cases were unintentional (92.8%). The prevalence of childhood poisoning in descending order was; compound therapeutic medications (32.69%) followed by pesticides (26.92%) then corrosives (17.31%), while volatile hydrocarbons (benzene or kerosene) accounted for (15.38%) and carbon monoxide (3.85%) and others (3.85%). Overall, minor cases were the commonest (63%) while only 3.8% of cases were severe. About 88.94% of cases were discharged after completed management while death rate was 0.96%. Conclusion: Most childhood poisoning cases were males, accidentally, mainly by oral route and in rural areas, most commonly in age group of 3 - 6 years. Most cases were due to therapeutic medications then pesticide exposures. Most of cases were completely cured.

Abiogenic formation of H2, light hydrocarbons and other short-chain organic compounds within the serpentinite mud volcanoes of the Marianna Trench

Serpentinite-hosting mud volcanoes, located in the Marianna forearc subduction zone, were drilled during IODP Expedition 366. Recovered samples from Asùt Tesoru seamount provide new insights on the generation of organic matter in deep environments. Short-chain alcohols, volatile fatty acids and light hydrocarbons are produced within hyperalkaline pore fluids (pH 12.5) rich in H2. The stable isotope values of those species show heavy δ13C values, suggesting a formation process through Fischer-Tropsch-Type reactions. This close isotopic study brings new constraints on the reaction pathways leading to the formation of not only light hydrocarbons, but also of short-chain organic molecules. These compounds may serve as precursors of building blocks essential to life in deep oceanic settings.

Determination Safe Duration of Exposure to Benzene in Workers of Petrolium Processing industrial Laboratory in indonesia by Using Noael of White Mice (Rattus norvegicus)

Benzene is a volatile liquid aromatic hydrocarbon. Benzene is also used in industries related to oil processing, one of which is fuel. According to the Agency for Toxic Substances and Disease Register (ATSDR), toxic chemicals contained in oil includes Policyclic Aromatic Hydrocarbons (PAHs), Total Petroleum Hydrocarbon (TPH), benzene, ethylene and toluene. Of all these toxin substances, benzene is the most dangerous chemical and exposure to benzene has a serious impact on human health. As a form of control effort, determining the safe duration of exposure (Dt) for benzene exposure based on the value of RfC (Reference of Concentration) using NOAEL (No Observed Adverse Effect Level) of white mice (Rattus norvegicus) is needed. This study aimed to determine the value of No Observed Adverse Effect Level (NOAEL) of white mice (Rattus norvegicus), safe limits of toxin dosage for the community or Reference of Concentration (RfC), Risk Quontient (RQ) and safe duration of exposure (Dt) in laboratory workers. This was a cross sectional, observational, and descriptive study with 51 samples of PT Pertamina RU IV Cilacap laboratory workers. The object sample used in this study was the air in the work area of the main laboratory section and the petrochemical and gas laboratory of PT Pertamina RU IV Cilacap. The results of this study indicated that safe duration of exposure (Dt) was 19 years; under normal safe duration of exposure for workers. The safe duration of exposure (Dt) can be a reference for the relevant company to consider the workers� working period and reduce the exposure duration with benzene to prevent significant health impact on workers. © 2019, Indian Journal of Public Health Research and Development. All rights reserved.

Benzene and leukemia: from scientific evidence to regulations. A historical example.

Background:Benzene is a highly flammable, highly volatile liquid aromatic hydrocarbon. It has been used in many industrial processes as a solvent or a starting material. At the beginning of the twentieth century, it was very widely used in the workplace, especially in printing and in the shoe manufacturing and rubber industries. Although benzene was first recognized to cause aplastic anemia, its association with leukemia has been investigated only since the 1930s. In 1963, Italy was one of the first countries in the world to adopt a law to ban benzene as a solvent in work activities.Objectives:This study analyzed the contribution of the Clinica del Lavoro in Milan, Italy, to studies of the relationship between exposure to benzene and leukemia.Methods:Scientific literature and historical sources on benzene and leukemia in the twentieth century were reviewed, and interviews with a first-hand witness of that period were conducted.Results:By 1928, several scholars had reported anecdotal cases of leukemia among workers exposed to benzene. Enrico Vigliani was the first to collect all of these cases and to try to conduct statistical analysis on these data, in order to support the association between benzene and leukemia. In the 1960s, Vigliani and Alessandra Forni showed that benzene could cause chromosome aberrations in the bone marrow that could produce leukemic clones.Conclusions:As a result of these studies and the subsequent regulations which banned benzene, exposure conditions changed in the workplace in the last few decades. The resulting low concentrations have prompted researchers to investigate new exposure biomarkers and to study any related health problems.

Volatile compounds and quality analysis in commercial medicinal plants of Camellia sinensis

ABSTRACT: The interest in the use of green tea (Camellia sinensis) (L.) Kuntze (Theaceae) products have increased in the last few years due to its medicinal properties. In the present study, we proposed that headspace solid phase microextraction, in combination with gas chromatography coupled to mass spectrometric could be an efficient method to assess the volatile compounds and to ensure the quality control of C. sinensis. We have also compared the anatomical leaf of different commercial green tea samples, analyzed the information in their labels and determined the presence of foreign materials, moisture content, total ashes and microorganisms. Among the 30 analyzed samples, six were identified as C. sinensis according to the anatomical study; 83.4% were not in accordance with the specified limits for foreign matter and 6.6% for moisture content. All samples presented total ashes in accordance with the current legislation. The analysis indicated the presence of several different volatile organic compounds, being terpenes, hydrocarbons and alcohols the major ones. Microbiological analysis showed that 13.3% and 16.6% of the samples exceeded the limits for counts of molds and yeasts, and for mesophilic bacteria, respectively. 73.3% presented E. coli above the established sanitary limits.

Environmental Forensic Investigation in the Residential Neighborhood Volta Grande IV, Volta Redonda, RJ, Brazil, Using TPH and PAHs Analyses in Soil Samples

This article presents the results of a forensic investigation concerning the origin of hydrocarbons detected in the subsurface soil of the residential neighborhood Volta Grande IV, Volta Redonda, RJ, Brazil. Previous investigations identified several areas with concentrations of volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) above the Brazilian regulatory standards of CONAMA 420/2009 within the study area. Concern was raised that these hydrocarbons might be derived from local steel mill wastes. This forensic investigation determined that the VOCs in the residential soil are associated with gasoline and possibly diesel fuel oil releases into the subsurface soils that are not associated with the steel mill waste. The PAHs in residential subsurface soil generally fell below background concentrations and are likely associated with regional soot. The PAHs in the three samples with concentrations above background (out of a total of thirty-six samples) exhibit compositional features similar to coal byproducts, such as tar and coke, possibly attributable to the steel mill operation. This work discusses the geoforensic data and chemical signatures that support these findings.

Volatile unsaturated hydrocarbons emitted by seedlings of Brassica species provide host location cues to Bagrada hilaris.

Bagrada hilaris Burmeister, is a stink bug native to Asia and Africa and invasive in the United States, Mexico, and more recently, South America. This species can cause serious damage to various vegetable crops in the genus Brassica, with seedlings being particularly susceptible to B. hilaris feeding activity. In this study, the role of volatile organic compounds (VOCs) emitted by seedlings of three Brassica species on the host preference of B. hilaris was evaluated. In dual choice arena and olfactometer bioassays, adult painted bugs preferred B. oleracea var. botrytis and B. napus over B. carinata. Volatiles from B. oleracea seedlings were collected and bioassayed with B. hilaris adults and late stage nymphs, using electroantennographic (EAG) and behavioral (olfactometer) techniques. When crude extracts of the VOCs from B. oleracea var. botrytis seedlings and liquid chromatography fractions thereof were bioassayed, B. hilaris adults and nymphs were attracted to the crude extract, and to a non-polar fraction containing hydrocarbons, whereas there were no responses to the more polar fractions. GC-MS analysis indicated that the main constituents of the non-polar fraction was an as yet unidentified diterpene hydrocarbon, with trace amounts of several other diterpene hydrocarbons. The major diterpene occurred in VOCs from both of the preferred host plants B. oleracea and B. napus, but not in VOCs of B. carinata. Our results suggest that this diterpene, alone or in combination with one or more of the minor compounds, is a key mediator in this insect-plant interaction, and could be a good candidate for use in lures for monitoring B. hilaris in the field.

Suda Uçucu Aromatik Hidrokarbonların (UAH’lar) Hassas ve Doğru Analizi için Gaz Kromatografisi Yöntemi Doğrulama Çalışması

A wide range of chemicals comes to exist at the end of the industrial activities. They could have highly toxic and carcinogenic effects on the human health and water environment. Therefore, these substances, which are listed as prohibited chemicals on national and international lists, must be monitored permanently with regards to environmental and human health both in the water resources and potential receiving waterbodies. The objective of this study was to present the method for the sensitive and accurate determination of some volatile aromatic hydrocarbons (VAHs), including quite dangerous substances such as benzene, toluene, xylenes, styrene and chlorobenzenes by using gas chromatography - mass spectrometry (GC-MS) with purge &amp;amp; trap (PT) process in different water samples. The proposed method was verified with the selectivity, linearity, limits of detection and quantification (LOD and LOQ), precision studies of the method and instrument. All analytes examined in the study were trustworthily measured within the maximum performance limits for PT-GC-MS. The selectivity work was carried out by duplicate analysis of six blank water samples. There is no finding or observation within the interval of the retention time of the analytes in the water samples. The linearity of calibration curves was drawn by analysis of prepared standard solutions at nine concentration levels. The analytical response linearity in the working range can be assessed as an excellent since the correlation coefficients higher than 0.9996 for all analytes. The method accuracy was carried out by doing recovery experiment. Recoveries of analytes have been changed from 88.4 % to 94.6 % and the relative standard deviation (RSD) results were found between 3.52 % and 6.35 %. The applicability of developed method was confirmed by the determination of related analytes in the water samples.

Method for Analyzing the Molecular and Carbon Isotope Composition of Volatile Hydrocarbons (C1-C9) in Natural Gas.

Solid-phase microextraction (SPME) coupled with gas chromatography-isotope ratio mass spectrometry (GC-IRMS) has already been applied to collect and identify volatile light hydrocarbons in oil and source rocks. However, this technology has not yet been used to analyze volatile light hydrocarbons in dry gas (natural gas with C1/C2+ > 95%). In this study, we developed a method to measure the molecular and carbon isotope composition of natural gas using divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber. This fiber proved to be suitable for extracting C1–C9 hydrocarbons from natural gas without inducing carbon isotopic fractionation. Notably, the extraction coefficients of the analytes were not the same but rather increased with the increasing carbon number of the hydrocarbons. Nevertheless, we successfully identified 24 hydrocarbons from the in-lab standard natural gas, while also obtaining the carbon isotope composition of C1 to C9 hydrocarbons with satisfying repeatability. The relative standard deviation (RSD) of the molecular composition data was in the range of 0.06–0.74%, with the RSDs of the carbon isotope composition data not exceeding 1‰. Finally, seven natural gas samples, collected from different sedimentary basins, were successfully analyzed and the stable carbon isotope compositions of C1–C9 hydrocarbons present in these were determined through this method. Overall, the new approach provides a simple but useful technique to obtain more geochemical information about the source and evolution of natural gas.

The development of semiconductor Fourier spectroscopy principles for the gas analysis on the example of the volatile hydrocarbons concentrations thin-film sensors on based on rare-earth elements

In this work the basic principles of creation of semiconductor Fourier spectroscopy for the gas analysis are formulated, that will allow us to increase selectivity, sensitivity and stability of an operation of the gas sensors. The experimental data obtained by means of semiconductor sensors on the basis of samarium sulfide made by zol-gel technology given detecting micro impurity of propane and methane in atmospheric air are given in work.