Ratios Of Hydrocarbons Research Articles

PECVD-derived graphene saturable absorber mirror for 2.8 μm pulsed Er:ZBLAN fiber laser

Graphene has been emerging as an ideal mid-infrared saturable absorber (SA) due to its broadband absorption, ultrafast nonlinear optical response, high stability and thermal tolerance. However, the current routes (e.g. chemical vapor deposition and spin coating) for constructing graphene SAs are suffering from the limited flexibility in substrate choice and the introduction of impurities during the transfer process, resulting in poor film quality and unstable laser modulation. Here, we demonstrate a high-quality graphene SA mirror (GSAM) grown directly on calcium fluoride (CaF2) substrate by a low-temperature plasma enhanced chemical vapor deposition (PECVD) method for mid-infrared pulse modulation. The controllable growth of high-quality graphene film on the nickel-modified CaF2 substrate is realized by adjusting the growth time and hydrocarbon ratio during PECVD process. Consequently, the GSAM shows excellent nonlinear optical absorption with the modulation depth of 11.2%. By inserting the GSAM into the Er:ZBLAN fiber laser, a stable passive Q-switched (QS) operation can be achieved with an average output power of 142 mW and a pulse width of 300.2 ns. The slope efficiency of QS laser is up to 17.4% and the peak power is 7.76 W. Our strategy paves the way for developing high quality and modulation stability GSAM towards industrial applications of pulsed mid-infrared lasers.

The Effect of Thermochemical Sulphate Reduction on the Carbon Isotope Ratio of Individual Light Hydrocarbons Associated With Natural Gas

To understand the effect of thermochemical sulphate reduction (TSR) on the stable carbon isotopes of light hydrocarbons (LHs) associated with natural gas, 15 gases with varying H2S content from Ordovician reservoir of the Tazhong gas field (TZ-I) in Tarim Basin and Triassic Leikoupo reservoir of the Zhongba gas field (ZB) in Sichuan Basin were collected. Based on the data from molecular components and stable carbon isotope ratios of the C1-C4 alongside the individual LHs (C6-C7) in these gases, the origin of natural gas and the effect of TSR on the stable carbon isotope ratio of individual LHs were studied. The δ13C in ethane (<−28‰), LHs (<−26‰) and the composition distribution characteristic of C6-C7 indicated that the gases were oil-associated gases. Moreover, the gas sourness index, defined as H2S/(H2S+∑Cn) demonstrated that the gases from the TZ-I and ZB gas fields were in the early liquid-hydrocarbon-involved and heavy-hydrocarbon-gas-dominated TSR stages, respectively. The comparison of stable carbon isotope ratios of the LHs between the two gas fields revealed that TSR exhibited a complex effect on the carbon isotope values of LHs, but only little effect on 2-methylpentane (2-MP) and 3-methylpentane (3-MP). The δ13C values of benzene (BEN) and toluene (TOL) were -28.3‰ and -29.4‰ in the TZ-I and -27.7‰ and -28.1‰ in the ZB gas field. The stable carbon isotope ratios of BEN and TOL in ZB gas field exhibited more enriched 13C than those in TZ-I gas field, likely driven by TSR. Meanwhile, cycloalkanes, such as methyl cyclopentane (MCP), cyclohexane (CH), and methylcyclohexane (MCH), enriched 13C with TSR process and displayed a greater trend than aromatic compounds, about 2‰. Therefore, the influence of TSR on the carbon isotopes of individual LHs should be considered while using the stable carbon isotope ratio of cycloalkanes, BEN, and TOL to identify the genetic type and source of marine natural gas, especially at the cross plot (δ13C = −24‰) of coal-derived gas and oil-associated gas.

Fast characterization of biomass pyrolysis oil via combination of ATR-FTIR and machine learning models

This study proposed a fast characterization method of bio-oil via the combination of attenuated total reflection flourier transformed infrared spectroscopy (ATR-FTIR) and machine learning models. The input to the model is high-dimensional infrared spectral data. Unsaturated concentration, effective hydrocarbon ratio, low calorific value, C content, H content, and O content are all relevant bio-oil indicators. The model parameters were optimized based on prediction accuracy and correlation coefficient. By comparing the sole support vector regression (SVR) model versus principal component analysis (PCA) preprocessed SVR model, the results showed that PCA preprocessing can significantly improve the overall performance of SVR model towards prediction of bio-oil characteristics. Under optimal parameters, the predicted accuracies for unsaturated concentration, effective hydrocarbon ratio, low calorific value, C content, H content, and O content reached 91.98%, 97.44%, 99.50%, 98.65%, 98.56%, and 97.88%, respectively. The correlation coefficient of sole SVR model was 0.3, and the correlation coefficient of PCA preprocessed SVR model was 0.9. Furthermore, the characteristic peaks of the infrared spectra at the optimal PC were analyzed, and PC6 and PC7 were found to have the most influence on the predicting performance.

FORECAST OF HYDROCARBON RATIOS BASED ON EXTRACTED RESERVES

The article provides an analysis of the forecast of hydrocarbon ratios based on the data extracted. Various methods are used in the technological processes of gas extraction in order to build forecast models of the final gas-condensate yield coefficients. It is important to select the most accurate and reliable models in order to determine the recoverable reserves of gas and condensate fields operated in flood and depletion regimes or to assess the effectiveness of geological and technical measures taken to increase development efficiency. Mathematical modeling methods are widely used for analysis, control of gas and condensate field development and qualitative and quantitative forecasting of its technological parameters. At the same time, long-term operation of gas-condensate fields shows that the application of erolusion modeling methodology, which is one of the most accurate methods for determining the forecast values of recoverable gas reserves for different stages of development, is more appropriate. Keywords: Extracted reserves, hydrocarbon ratios, forecast, regimes, water pressure, gas-condensate fields.

Experience in the Application of Hydrocarbon Optical Studies in Oil Field Development

This article reviews the results of measurement of optical properties of oil, such as polarimetry, refractometric, luminescent-bituminological research, IR-spectrometry and UV-visible-NIR spectrometry used to solve geo-bituminology development of hydrocarbon deposits. The authors pay special attention to optical research in the field of UV-visible-NIR electromagnetic radiation, the results of which allow us to estimate the residual oil reserves, separate production for each formation during the operation of multi-layer objects, determine the producing gas-oil ratio, density and content of hydrocarbons, efficiency of hydraulic fracturing, flow-reducing technologies, and injection of solvents of heavy oil sediments, etc. The published approaches to methods of optical research, which are carried out by laboratories or in-well devices, have been analyzed. This article analyzes the main advantages and disadvantages of current technologies for determining the optical properties of oil. The authors propose wellhead devices for determining the optical properties of oil in UV-visible-NIR radiation (190–1100 nm) and their functional schemes, with a description of the operating principle.

Emissions Merit Function for Evaluating Multifunctional Catalyst Beds

With emission control regulations getting stricter, multi-functional catalyst systems are increasingly important for low-temperature operation. We investigate a wide range of multi-component catalyst systems, as physical mixtures and in multi-bed configurations, while varying the ratios of hydrocarbon traps (HCT), passive NOx adsorbers (PNAs), and diesel oxidation catalysts (DOC). Using industrially guided protocols, we measured the ability of these complex catalyst systems to reduce emissions during a 40 °C/min temperature ramp to simulate cold-start conditions. Using a temperature boundary condition of 250 °C, the average conversion was calculated for each regulated pollutant: CO, NOx, and total hydrocarbons (THC). An emissions merit function was developed to evaluate the effectiveness of each system relative to the relevant emission standards and expected engine exhaust concentrations. This merit function identified that a 1:1:4 ratio of PNA:HCT:DOC was the most effective emissions reduction configuration and had similar reactivity as a physical mixture or as a PNA→HCT→DOC multi-bed reactor.

Modeling, Kinetic and Experimental optimization of Reforming Unit for ‎Al- Doura Heavy Naphtha over bi and Tri-metallic Catalysts

In the present work mathematical representation (simulation studies) and experimental work in order to describe the Iraqi heavy naphtha ‎(feed stock) for catalytic reforming process ‎reaction kinetics. Tri and bi-metal catalysts were prepared by adding of tin and iridium (Ir) ‎to classical catalyst using in catalytic reforming unit in Al –Doura refinery to enhance ‎th reaction selectivity. Catalysts performance (activity and selectivity) for the three main catalytic reforming reactions were investigated such as dehydrogenation, hydrocracking, and dehydrocyclization reaction. Catalysts performances were investigated under the following operating condition: constant reaction pressure equal to 6 atm‎, the reaction temperature range of (480, 490, 500, and 510 ˚C), constant hydrogen to hydrocarbon ratio of 4:1, and WHSV (weight hour space velocity) range of (1, 1.5, and 2 hr-1) The results show that as reaction temperatures increase‎ higher conversion of Paraffins and Naphthenes components ‎in Iraqi heavy naphtha while negative impact on conversion as‎ weight hourly space velocity increase (i.e., higher WHSV shows lower conversion). Generally tri and bi-metal catalysts the aromatics and light components ‎yields will be increased under the same operating conditions reforming process.

Selective Hydrocracking Of Heavy Distillate To High Viscosity Index Lube Base Stock By Using Bi-Functional Catalysts

Hydroprocessing is the catalytic reaction of hydrogen with petroleum or other hydrocarbon materials. It may be carried out for a variety of objectives, including: saturation of olefins or aromaties, molecular rearrangement, or removal of impurity (1).Selective hydrocracking is one of this hydroprocessing to convert higherboiling distillate to lube base stock using a bi-functional catalyst containing both acid site and metal site. Those two active sites of bi-functional catalyst should promote the correct combination of hydrogenation, isomerization and limited hydrocracking function, resulting in the maximum yield of product in the lube oil range (2). The kinetics of this selective hydrocracking greatly depends on the operating conditions: such as feedstock composition, type of catalyst, temperature, pressure, hydrogen to hydrocarbon ratio, and space velocity (6).The versatility of the hydroconversion process with respect to the variety of feedstock are case to study: i.e. the feasibility of the hydroconversion of obtaining lube base stock from heavy distillate.In order to gain more information, an experiment has been carried out to study the selective hydrocracking of vacuum distillate (paraffinic and non paraffinic) by using bifunctional catalysts with various acidity at the following operating conditions: temperature: from 380 to 410 ° C, pressure: 100 kg/cm2 and hydrogen to hydrocarbon ratio: 1000 l/lt. A catatest unit operated in a continuous system was used in this experiment.Gas and liquid product samples were taken from gas and liquid samples, respectively. Liquid product was fractionated to get the following cuts: IBP-380°C and380°C with 30 theoretical plate fractionator, operating at 4/1 reflux ratio. The 380°C bottom product was treated by dewaxing, using methylisobutyl ketone as a solvent to obtain the lube base stock and wax.

Jet Fuel Synthesis from Syngas Using Bifunctional Cobalt-Based Catalysts

Advanced biofuels are required to facilitate the energy transition away from fossil fuels and lower the accompanied CO2 emissions. Particularly, jet fuel needs a renewable substitute, for which novel production routes and technology are needed that are more efficient and economically viable. The direct conversion of bio-syngas into fuel is one such development that could improve the efficiency of biomass for jet fuel processes. In this work, bifunctional catalysts based on hierarchical zeolites are prepared, tested and evaluated for their potential use in the production of actual jet fuel. The bifunctional catalysts Co/H-mesoZSM-5, Co/H-mesoBETA and Co/H-mesoY have been applied, and their performance is compared with their microporous zeolite-based counterparts and two conventional Fischer–Tropsch Co catalysts. Co/H-mesoZSM-5 and Co/H-mesoBETA showed great potential for the direct production of jet fuel as bifunctional catalysts. Besides the high jet fuel yields under Fischer–Tropsch synthesis conditions at, respectively, 30.4% and 41.0%, the product also contained the high branched/linear hydrocarbon ratio desired to reach jet fuel specifications. This reveals the great potential for the direct conversion of syngas into jet fuel using catalysts that can be prepared in few steps from commercially available materials.

On the determination of oil charge history and the practical application of molecular maturity markers

Determining the thermal maturity and the charge history of crude oil to any reservoir, has key implications for understanding petroleum generation, accumulation history and hence identification of exploration potential. In this paper we combine studies of several source rock sequences and associated crude oils using quantitative component concentration data in addition to traditional molecular marker ratio parameter approaches. The case history studies include examination of organic-rich sapropelic marine source rocks from the Second White Speckled Shale Formation (2 WS Fm.), in the Western Canada Sedimentary Basin and the upper Jurassic Draupne Fm. in the North Sea and their related oils. Each molecular component in the petroleum has a unique concentration evolution curve during source rock maturation, in which n-alkanes, light aromatic hydrocarbons and diamondoid hydrocarbons increase in concentration with increasing maturity, while biomarkers decrease in concentration with maturity. This maturity dependent concentration variation plus the ubiquitous mixing of multiple oils in the reservoir is a key process that complicates the direct application of qualitative molecular marker ratio approaches to analysis of petroleum systems. We suggest an alternative maturity assessment approach using maturation calibrated curves of absolute concentrations of biomarkers and other alkanes in petroleum, coupled with selected aromatic hydrocarbon ratios to track the maturity/petroleum mass fraction relationships for a reservoired oil mixture in a more complex but realistic manner. Isoprenoid alkanes show less variation in concentration with maturity than other components and may be used as an internal reference point for mass fraction maturity and charge history assessment. Using component concentration data normalized to the concentration of the isoprenoid alkanes and calibrated using source rock analyses at different maturity levels from a single petroleum system (2WS), a simple mass balance model was constructed that allowed aggregate concentration data to be calculated for any mixture of oils produced in a prescribed oil charge history. In principle any charge history can be simulated using this approach and comparing the modelled and actual quantitative compositional profiles of crude oils allows differentiation of the more plausible and implausible oil charge histories for that particular reservoir. Clearly considerable refinement of this approach is needed but it appears that such a procedure has the potential, if developed further, to be a useful addition to the arsenal of petroleum geochemists and basin modelers. Knowing what a typical complete charge mass fraction maturity profile would look like for a given source rock type, enables the estimation of missing charge in the basin, allows the detection of complex multi-history charge scenarios, and provides a much more robust and complete data set for calibration of basin model charge history assessments. It also, with further development may be integrated into stochastic basin modelling approaches to study petroleum systems.

Mobile monitoring of VOCs and source identification using two direct-inlet MSs in a large fine and petroleum chemical industrial park

Mobile monitoring with direct-inlet MS (DI-MS), one of the most direct and effective ways to track emission sources, can effectively serve air quality management in chemical industrial parks (CIPs). Mobile monitoring using a high mass-resolution proton-transfer-reaction time-of-flight MS (HMR-PTR-TOFMS) and single-photon ionization time-of-flight MS (SPI-TOFMS) was conducted in a large fine and petroleum CIP in eastern China for three days. The high mixing ratios of aliphatic hydrocarbons (AHs), aromatics, oxygenated VOCs (OVOCs), and nitrogenous VOCs (NVOCs) were found in the northeast, middle, north, and northeast of the fine chemical industrial zone (FCIZ), respectively. OVOCs were the most abundant VOC group in this area. Abnormal emissions of aromatics were universal throughout the CIP. We discovered 38 characteristic VOCs by the HMR-PTR-TOFMS, mainly including C6-C10 aromatics, C2-C6 carbonyls, C2-C3 organic acids, and some NVOCs. The time series and spatial distribution of the TVOCs obtained by the two DI-MSs are generally consistent. A comparison of the speciated VOCs at the TVOC peak points illustrates that the characteristic VOCs obtained by different instruments differed significantly: PTR-TOFMS showed an advantage in measuring aromatics and OVOCs; SPI-TOFMS showed an advantage in measuring aromatics and some Ahs; offline GC–MS showed an advantage in measuring AHs, aromatics, some OVOCs, and halohydrocarbons. Similarities were compared between five positive matrix factorization (PMF) model-based fingerprints of VOCs in a previous study and observed profiles of VOCs from mobile monitoring. The emission sources of the five fingerprints were identified and validated: two were widely distributed, one was a chemical reagent production factory, one was an acrylic fiber production plant, and one was a pesticide factory. This study demonstrated methods for analyzing mobile monitoring data, characterizing the VOCs in the fine and petroleum CIP, correlating the results of stationary observation and mobile monitoring, and integrating the source tracing system with DI-MSs.

Highly Selective Production of Aromatic Hydrocarbons by CO2 Hydrogenation over Fe-Zn Oxide + H-ZSM-5 Composite Catalyst

Abstract Composite catalysts consisting of Fe-Zn oxides and H-ZSM-5 were very effective for the selective production of aromatic hydrocarbons by CO2 hydrogenation. The ratios of aromatic hydrocarbons in all hydrocarbons were beyond 80 C-mol% using these catalysts. When the weight ratio of Fe-Zn oxide and H-ZSM-5 was optimized, the ratio of aromatic hydrocarbons reached more than 90 C-mol%. The Fe-Zn oxides acted as methanol synthesis catalyst in the composite catalyst, forming aromatic hydrocarbons by methanol-to-hydrocarbons reaction over H-ZSM-5. Two aromatic hydrocarbons, p-xylene and 1,2,4-trimethylbenzene, were mainly obtained by the shape selectivity effect of H-ZSM-5. The composite catalyst deactivated by coke formation could be regenerated by air flow treatment.

Improved distributed optimization algorithm and its application in energy saving of ethylene plant

This paper investigates an energy optimization problem for ethylene production process without system dynamics. Fundamentally different from the conventional centralized optimization strategies, the energy optimization in the ethylene production process is transformed into a distributed optimization problem with input constraints due to multiple interconnected units involved. Based on the combination of consensus mechanism and gradient tracking technique, a distributed algorithm with adaptive step-sizes is derived to optimize the coil outlet temperature (COT) and steam hydrocarbon ratio (SHR) in the thermal cracking process as well as the temperature and duty in the product separation process. Besides, considering the mechanism limitation, a projection operation is adopted to deal with input constraints. The experimental results show that the proposed distributed algorithm is superior to the centralized method in terms of computational efficiency and robustness with a faster convergence speed.

An optimized accelerated solvent extraction and purification method for enhanced recovery of n-alkanes (notably short-chains) from environmental samples using the conventional dichloromethane/methanol solvent

Sedimentary lipid biomarker proxies are extensively used for paleoclimatic and paleoenvironmental research. Among all the lipid compounds, the non-polar n-alkanes (chain lengths n-C14 to n-C37) are one of the most widely used lipid fractions for such studies. However, the lack of optimized automated extraction and post-extraction sample workup procedure, using conventional polar solvent, from environmental samples, has been challenging. Conversely, extraction of the n-alkanes using non-polar solvents restricts the co-extraction of other polar lipid compounds like ketones, alcohols, acids, etc. which may be of interest to many researchers. Here we report an optimized total lipid extraction method using the conventional polar dichloromethane/methanol solvents with standardized Automated Solvent Extractor (ASE) parameters and post-extraction sample work-up protocols. The robustness of the method has been tested by extracting eight samples containing algae, leaf, and sediment/rock of varying age (spanning from recent to ∼252 Ma). The results of the extraction efficiency (yield) of the method were compared with commonly used methods, those using either non-polar n-hexane or polar dichloromethane/methanol solvents. For n-alkane extraction from algal biomass, the performance of the proposed method and the conventional polar solvent method are statistically comparable, but the new method performs better than the non-polar solvent method. Likewise, for the leaf and sediment samples, the performance of the proposed method is equivalent to the non-polar solvent method but outperforms the commonly used polar solvent method. The Terrestrial Aquatic Ratio (TAR) and long-chain hydrocarbon/short-chain hydrocarbon (LHC/SHC) ratios calculated from the algae and sediment samples also show that our recommended extraction approach can be confidently used in calculating n-alkane ratio proxies, which critically depend on the extraction efficiency of the short-chain n-alkanes. Taken together, the new method will be highly useful for studying the n-alkanes from a wide spectrum of natural sample matrices and provide reliable data for paleoclimatic inference.

Laboratory simulation of the influence of chromatographic effect and microbial oxidation on hydrocarbon microseepage

An experimental apparatus has been constructed with various experimental conditions to simulate the influence factors of the hydrocarbon gases microseeping from the deep reservoir to the surface. Both the chromatographic effect and the microbial oxidation effect are considered in the experiment. The results show that: the vertical hydrocarbon microseepage has the characteristics of a 'jump-over migration effect'; the coupling of a chromatographic process and microbial oxidation has less effect on the composition ratios of microseepage hydrocarbons, whereas the microbial oxidation has a large effect on the isotope values of methane; and the normal alkane and iso-alkane content of vertical microseepage show obvious differences due to the influence of chromatographic process and microbial oxidation. These experimental results may help to identify the genetic origins of the vertically migrating hydrocarbons, and thus promote the successful application of the surface hydrocarbon geochemical exploration technology. [Received: July 1, 2021; Accepted: February 23, 2022]

복합화력발전소 융합탈질설비에서 질소산화물 배출저감분석

Recently, the concern of the fine dust is increasing in our society and nitrogen oxides(NOx) has been considered as precursor of fine dust. Because, as well as the coal-fired power plants, the combined cycle power plants using LNG fuel also emit nitrogen oxides, our society strongly demands to lower the emission of NOx from the combined cycle power plants. In response of the public demand, Korean government set more stringent emission standard. Therefore, LNG power plants need to cope with it. The purpose of this paper is to study a reactive test that leads to Fast SCR by adjusting the mixing ratio of hydrocarbon reducing agent and NH3 reducing agent respectively. By so, it is expected to minimize the negative impact on the power plant operation and the power generation efficiency and contribute to the environment-friendly operation of power plant. Possessing a DeNOx system applicable to old combined cycle power plants and obtaining leading study results on the simultaneous removal of nitrogen oxides

Thermochemical conversion of biomass volatiles via chemical looping: Comparison of ilmenite and steel converter waste materials as oxygen carriers

Two oxygen carriers were tested with respect to chemical looping combustion (CLC) and chemical looping gasification (CLG). Ilmenite, a natural ore composed mainly of iron–titanium oxide, and LD Slag, an iron-based industrial waste, were investigated at 850 and 900 °C in a continuous operation in a 0.3 kW chemical-looping reactor system using synthetic biomass volatiles as fuel. CLC and CLG conditions were simulated in the fuel reactor by changing the fuel flow rates. In the case of ilmenite the syngas yield and methane conversion increased with fuel flow rate. Consequently, the syngas to hydrocarbon ratio was higher for ilmenite. Methane conversion improved for both tested oxygen carriers with increasing the operating temperature. Oxygen release was observed in the case of LD Slag. The H2/CO ratio was between 0.7 and 0.8 for both oxygen carriers at the higher fuel flows. With respect to CLC, ilmenite showed higher gas conversion than LD slag. Analysis of the particles revealed that ilmenite possessed better mechanical properties and formed less dust compared to LD Slag during the continuous operation with fuel.

Hydrocarbon accumulation depth limit and implications for potential resources prediction

The horizontal distribution and periodic accumulation of hydrocarbon in reservoirs are well understood. However, our understanding on the vertical distribution of hydrocarbon accumulation in reservoirs is not clear and remains mysterious to some extent. We proposed a concept of hydrocarbon accumulation depth limit (HADL) to characterize the hydrocarbon’s vertical distribution in petroliferous basins, which is determined by statistical analyses of the variation trends of reservoir layers’ essential properties, including hydrocarbon saturations (So), movable hydrocarbon ratios (Mo) and dry layer ratio (Ko), when the depth is increased. A total of 80,762 drilling results from 12,237 exploration wells in six representative petroliferous basins in China were collected and analyzed. The reservoir layers’ essential properties So, Mo and Ko and their correlations with porosity, permeability, pore throat radius and thermal evolution degree were investigated. The critical values of So, Mo and Ko that define HADL were quantified to be So = 0, Mo = 0 and Ko = 100. Our study indicates that the HADL in petroliferous basins varies from less than 3,000 m to more than 13,000 m deep, depending on the hydrocarbon composition, reservoir lithology, reservoir age, geothermal gradient, tectonic movement, etc. Two factors play an essential role in the formation and variation of HADL: 1) the depletion of hydrocarbon generation potential of source rocks which cuts off hydrocarbon contribution for reservoirs formation and 2) the termination of differential compaction which eliminates capillary pressure difference between the outer surrounding rocks and inner reservoir layers, ending the dominant driven force for hydrocarbon migration and accumulation in deep and tight reservoir layers. All proven oil reserves of 33.95 billion tons equivalent in China, as well as world’s discovered 52,926 oil and gas reservoirs and their unproved potential resources, are distributed above the HADL we defined.

Trilobites, Biostratigraphy, and Geochemistry of the Middle Cambrian Kuonamka Formation (Northeastern Siberian Platform, Kyulenke River)

Abstract —We studied the middle Cambrian unit of the Kuonamka Formation section on the Kyulenke River (Siberian Platform) and performed its biostratigraphic subdivision based on trilobites. The middle Cambrian section has intervals corresponding to the regional zones of the Amginian Stage. Six levels with mass accumulation of fauna remains have been identified: Two levels are located within the Ovatoryctocara Zone; the third level is at the boundary between the Ovatoryctocara and Kounamkites zones; the fourth layer is confined to the roof of the Triplagnostus gibbus Zone; and the fifth and sixth levels are located within the Tomagnostus fissus–Paradoxides sacheri Zone. The composition of rocks and bitumens of their organic matter (OM) has been studied, including the geochemical specifics of the mineral components of rocks (iron, sulfur, and CO2) and of saturated hydrocarbons of bitumens as well as noncarbonate carbon isotopes in the OM. It has been established that the OM sedimentation took place under normal aeration of the sea basin waters, without hydrogen sulfide contamination of the bottom waters. The intensity of chemical and biochemical transformations of mineral and organic components during diagenesis was controlled by the contents of organic carbon and sulfate ion, the activity of the anaerobic prokaryote community, and the rate of sediment mineralization. We have also established relationships between the content of organic carbon in potentially oil source rocks and the contents of iron oxide, total sulfur, and sulfide and sulfate sulfur as well as the ratios of saturated hydrocarbons. The alternation of highly carbonaceous black shales and carbonaceous rocks is apparently due to a change in the composition of biologic communities of microorganisms (sources of hydrocarbon biomarkers) and in the intensity of OM transformation during diagenesis. We assume that the OM transformation included sulfate reduction and dealkylation of high-molecular steroids in the unconsolidated OM-enriched marine sediments with the participation of bacteria. The intensity of these processes depended on the mass of the primary OM, the amount of sulfate ion, and, hence, the pH and Eh of the medium.

Pollution investigation and risk assessment of polycyclic aromatic hydrocarbons in soil and water from selected dumpsite locations in rivers and Bayelsa State, Nigeria.

The transfer ratio of polycyclic aromatic hydrocarbons (PAHs) from soil dumpsite to borehole water is dependent of polluting source and exposure matrices that causes immerse health risk to man and environment over a period of time. PAHs were assessed in selected soil dumpsite and borehole water located at Rivers state (Eleme, Eliozu, Eneka, Oyigbo, and Woji) and Bayelsa state (Yenagoa), Nigeria. Soil samples were collected at four different points 30 m (North, South, East and West) locations at a depth of 15 cm for each dumpsite using soil auger while control samples were collected 200 m away (farmland), where there were little anthropogenic activities and no presence of active dumpsites. Borehole water samples were collected from 300 m distance, which were packaged in an amber container, labeled, and transported to the laboratory for analysis. Standard analytical methods were employed. PAHs concentrations were analyzed using gas chromatography-mass spectrometry (GC-MS) after extraction of water and soil using liquid-liquid and soxhlet extraction methods respectively and clean-up of the extracts, thereafter the laboratory data generated were subjected to statistical analysis. Total PAHs (∑PAHS) concentrations in soil samples from the study sites ranged from 2.4294 mg/kg in Yenagoa to 5.1662 mg/kg in Eleme while in water samples the total PAHs ranged from 1.3935 mg/L in Woji to 3.009 mg/L in Eleme. The total PAH concentrations in the soil were above the Agency for Toxic Substances and Disease Registry levels of 1.0 mg/kg for a considerably contaminated site except for the control sites. The total concentration of carcinogenic PAHs ranged from 0.0038 to 1.1301mg/kg in soil samples and 0.0014 to 0.9429 mg/L in borehole water samples, therefore raising concern of human exposure via food chain. The results indicate that low molecular weight PAHs were more dominant than high molecular weight PAHs in both soil and water samples, however molecular diagnostic ratio shows that pyrogenic activities are major sources of PAHs as compared to petrogenic origin. Multivariate analysis (principal component analysis and Pearson correlation) showed strong negative correlation implying that they were from dissimilar sources and different migratory route. Cancer and non-cancer risk showed that children were more at risk compared to adults, where inhalation exposure were major contribution as compared to ingestion and dermal exposure, as such there is a need to implement regulatory laws on indiscriminate release of PAHs contaminants to maintain sustainability.