Distribution Patterns Of Hydrocarbons Research Articles

Revealing crucial effects of reservoir environment and hydrocarbon fractions on fluid behaviour in kaolinite pores

The adsorption interactions of hydrocarbons and clay surfaces are crucial to understanding fluid behaviour within shale reservoirs and to mediating organic pollutants in soils. These interactions are affected by the diversity of complex hydrocarbon components and the variations in environmental conditions. This study examines the interactions between kaolinite clay, featuring two distinct basal surfaces, and an array of hydrocarbons. We assess the impact of various molecular structures, functional groups, and environmental conditions (focusing on the reservoir temperature and pressure ranges) on the adsorption selectivity, surface packing, molecular alignment and orientation, and diffusion of hydrocarbons. Analyses of molecular interaction energies provide a quantitative elucidation of the adsorption mechanisms of hydrocarbons on the different kaolinite surfaces. Our findings suggest that molecular configuration, functional group properties, and spatial effects dictate the distribution patterns of hydrocarbons for the different kaolinite surfaces. The differences in the interaction energy between various hydrocarbons with kaolinite reveal the adsorption strength of different hydrocarbons in the order of asphaltenes > heteroatomic hydrocarbons > saturated hydrocarbons > aromatic hydrocarbons. Furthermore, we observe that the adsorptive characteristics of hydrocarbons on kaolinite are highly temperature-sensitive, with increased temperatures markedly reducing the adsorption amount. Beyond a certain threshold, the effect of pressure rise on the fluid behaviour of hydrocarbons is non-negligible and is related to molecular packing and reduced mobility. Simulation results based on actual geological characteristics demonstrate notable adsorption disparities among hydrocarbon components on different kaolinite surfaces, influenced by competitive adsorption and clay surface interactions. Polar surfaces are predominantly occupied by heteroatomic hydrocarbons, whereas on non-polar surfaces, asphaltenes and heavy saturated hydrocarbons develop multi-layer adsorption structures, with molecules aligned parallel to the surface.

Stratified migration and distribution of the constituents of coal tar in the stratum

Coal tar (CT) is widely used in the rubber industry to produce a reinforcing substance known as carbon black. Due to the complexity constituents of CT, the migratory dynamics of its constituents have not been characterized, resulting in contamination of soil and groundwater. To understand the migration and distribution characteristics of different nature components of CT in the study site, the distribution and migration patterns of total petroleum hydrocarbons (TPHs), polycyclic aromatic hydrocarbons (PAHs), and Dense Non-Aqueous Phase Liquids (DNAPLs, ρ≫1 g/cm³) in soil and groundwater in a rubber enterprise were characterized and analyzed. We found that: the different components in CT settle at different points in the soil as they migrate, exhibiting stratification. Specifically, TPHs in soil and groundwater are mainly concentrated in the shallow layer near the tank area, and the maximum concentration is 113,000 mg/kg; PAHs are more migratory than TPHs, and the maximum concentration of PAHs is 7408 mg/kg. Most PAHs are concentrated in the middle layer and above; DNAPLs tend to be transported to deeper stratum, penetrating deeper into the terrain and aggregating into pools (depth＞13 m). In addition, the inherently slow flow of groundwater slower groundwater flow does not significantly impact the further migration of pooled DNAPLs, but it does influence the orientation of their pollution plume. This study provides a more accurate characterization of the dynamics of pollutants associated with rubber enterprises; these results bring forth a theoretical basis for the remediation and management of pollution linked with CT.

Occurrence, distribution and sources of petroleum contamination in reef-associated sediments of the Gulf of Mannar, India

The distribution of saturated hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) was assessed in superficial sediment samples collected from Mandapam island groups, Gulf of Mannar, India. The hydrocarbon distribution pattern and the n-alkane indices (e.g., carbon preference index (CPI) and natural n-alkanes ratio (NAR)) were deployed to differentiate between the biogenic and anthropogenic sources. Petroleum pollution was indicated by the pristane/phytane ratio close to 1. Presence of a prominent unresolved complex mixture (UCM) as well as hopane concentrations further supported this assertion. The evaluation of petrogenic sources of contamination were also comprehended by various diagnostic ratios of PAHs. The sites associated with shipping activities, tourism, and located near the mainland and accessible portions of the islands exhibited high petroleum contamination. Correlation analysis underlines the significance of combining petroleum-specific marker compounds and diagnostic ratios to improve the assessment of human influence on marine ecosystems.

A new spatial estimation model and source apportionment of aliphatic hydrocarbons in coastal surface sediments of the Nayband Bay, Persian Gulf

Hydrocarbons, originating from oil and gas industries, are considered a potential risk for Nayband Bay, a natural marine park with extended mangroves, located on the north coastlines of the Persian Gulf, Iran. This paper determines the potential sources and spatial distribution of hydrocarbons, especially aliphatic hydrocarbons (AHCs), in Nayband Bay through the simultaneous application of three indices in the coastline surface sediments. To this end, a field study was conducted in the inter-tidal coastal zones and wetlands. Sediment samples were taken from surface layers along four transects with four sampling points at different distances from the gulf. The hydrocarbon compounds of the samples including AHCs, total petroleum hydrocarbons, and heavy metals (Ni, V as crude oil indicators) were analyzed and classified to discover the pollution indicators. Pearson pairwise correlation and cluster analyses along with pollution indices were employed to describe the spatial distribution pattern of hydrocarbons, identify hot spots, and determine the potential origin of AHCs. Different interpolation scenarios based on topographic and oceanic features were proposed to detect the spatial dynamics of AHCs. The results revealed that hydrocarbons mainly originated from anthropogenic sources including oil and gas industries located far from the affected area. It was also concluded that the long-distance pollution transfer was based on oceanic currents and wind direction in the bay. The proposed scenarios showed that the mean concentration values of total organic carbon and total organic material vary in the range 0.19 ppm to 0.4 ppm and 2.88 ppm to 3.20 ppm, respectively.

On the Formation of Diasteranes in Oil and Organic Matter of Rocks

Data obtained on the distribution patterns of biomarker hydrocarbons (n-alkanes, isoprenanes, steranes, and terpanes) in oils, organic matter in rocks, prokaryotes, and thermolysis products of the insoluble part of prokaryotic biomass indicate that the relatively high concentration of diasteranes (rearranged steranes) in the organic matter of rocks and in oils generated by clay strata is caused by characteristics of the original organic matter but not by the process of isomerization of regular steranes, as has been previously thought.

Cenozoic Depositional Evolution and Stratal Patterns in the Western Pearl River Mouth Basin, South China Sea: Implications for Hydrocarbon Exploration

Investigating the deposition evolution and stratal stacking patterns in continental rift basins is critical not only to better understand the mechanism of basin fills but also to reveal the enrichment regularity of hydrocarbon reservoirs. The Pearl River Mouth Basin (PRMB) is a petroliferous continental rift basin located in the northern continental shelf of the South China Sea. In this study, the depositional evolution process and stacking pattern of the Zhu III Depression, western PRMB were studied through the integration of 3D seismic data, core data, and well logs. Five types of depositional systems formed from the Eocene to the Miocene, including the fan delta, meandering river delta, tidal flat, lacustrine system, and neritic shelf system. The representative depositional systems changed from the proximal fan delta and lacustrine system in the Eocene–early Oligocene, to the tidal flat and fan delta in the late Oligocene, and then the neritic shelf system in the Miocene. The statal stacking pattern varied in time and space with a total of six types of slope break belts developed. The diversity of sequence architecture results from the comprehensive effect of tectonic activities, sediment supply, sea/lake level changes, and geomorphic conditions. In addition, our results suggest that the types of traps are closely associated with stratal stacking patterns. Structural traps were developed in the regions of tectonic slope breaks, whereas lithological traps occurred within sedimentary slope breaks. This study highlights the diversity and complexity of sequence architecture in the continental rift basin, and the proposed hydrocarbon distribution patterns are applicable to reservoir prediction in the PRMB and the other continental rift basins.

Detailed analysis of gaseous components in soil gases around petroleum wells - An effective tool for evaluation of their integrity

Recently methane has been regarded as one of the most hazardous gases in the Earth's atmosphere. Among important sources of methane emissions are leaking petroleum wells, both production and abandoned. The following paper presents an example of an optimal solution to the planning, execution, and interpretation of the results of surface geochemical surveys around decommissioned or abandoned, as well as production petroleum wells. The research consisted of the analytical results of the molecular composition of 94 soil gas samples collected around 3 wells in one of the oil and gas fields in the Polish Outer Carpathians. Using a patented sampling kit, soil gas was taken at 1.2 m depth at sampling sites located within a radius of 60 m from a particular well. Samples were analyzed chromatographically for their molecular composition. The results revealed the following maximum concentrations of selected gaseous components of soil gas: methane – almost 51 vol%, total alkanes C2–C5 – 0.51 vol%, total alkenes C2–C4 – 158.4 ppm, hydrogen – 0.1 vol%, carbon dioxide – 11.2 vol%, and nitrogen - 90.5 vol%. Detailed statistical analysis of the results demonstrated the presence of anomalous concentrations of methane and/or higher hydrocarbons that originated from leaking wells but also from the complex and complicated microbial processes that may be related to spills of crude oil or hydrocarbon fuels. The methodology of interpretation of the geochemical results applied may be useful in the evaluation of hydrocarbon distribution patterns and may provide an effective tool for the evaluation of the integrity of oil wells.

Seasonal distribution pattern and bioaccumulation of Polycyclic aromatic hydrocarbons (PAHs) in four bioindicator coastal fishes of Argentina

Polycyclic aromatic hydrocarbons (PAHs) are pollutants of global concern in coastal environments. They have a wide range of biological toxicity and due to their inherent properties, can easily bioaccumulate in organisms and concentrate in the environment. This work evaluated, in an integrated way, the seasonal PAH distribution patterns in sediments and four bioindicators fish species in a highly impacted estuary of Argentina; besides, their bioaccumulation patterns were assessed for the first time as indicator of ecological risk. The highest PAH levels in fish were found for Ramnogaster arcuata with an average of 64 ng g−1 w.w., followed by Micropogonias furnieri (45 ng g−1 w.w.), Cynoscion guatucupa (28 ng g−1 w.w.), and Mustelus schmitti (16 ng g−1 w.w.). Fish presented the highest PAH levels in fall with a predominance of petrogenic PAHs in colder seasons and pyrolytic PAHs in warmer seasons. Sediments presented an average of 233 ng g−1 d.w. with the same seasonal composition pattern of the fish tissues. Additionally, the data suggested that the main source of PAHs are wastewater discharges. The bioaccumulation factor (BAF) of PAHs in the tested fishes were found to range from 0.3 to 8. The highest values were observed during fall and winter, while bioaccumulation did not occur in moist spring and summer samples, which would suggest a high biotransformation process during these seasons. Results suggested that class III of juvenile C. guatucupa and M. furnieri, and adults R. arcuata are more sensitive bioindicators of chronic PAH contamination and that their bioaccumulation is independent of the compound hydrophobicity; this could have a positively influence on the criteria used for biological monitoring programs along the Atlantic coast. In addition, the presented BAF data on the target species will serve as a useful pollution indicator for South Atlantic coastal fish.

A study of the spatial distribution patterns of airborne polycyclic aromatic hydrocarbons in crowberry (Empetrum nigrum) in Ilulissat, Greenland

Polycyclic aromatic hydrocarbons (PAHs) are produced by anthropogenic activities, such as traffic and domestic heating. Due to their adverse effects to humans and natural habitats, the presence of PAHs in the environment needs to be monitored. Plants are known as natural accumulators of persistent organic pollutants (POPs) and can therefore be used for the monitoring of PAHs emitted into the environment. Contamination by PAHs also occurs in the Arctic such as Greenland due to long-range transport through air. However, as anthropogenic activities in the Arctic are increasing, there is a need to investigate the distribution of PAHs due to local emission sources. In this study, we present a systematic sampling approach to identify the influence of PAH sources in an area next to the town of Ilulissat in Greenland. Composite crowberry samples have been collected north of Ilulissat, where the town itself, an incineration site and Ilulissat airport are possible emission sources for PAHs. Matrix solid-phase extraction was used for the extraction of PAHs and the chemical analysis was performed by gas chromatography with mass spectrometry detection (GC-MS). In total, 18 out of 19 investigated PAHs could be detected in Empetrum nigrum in a concentration range of 0.69 to 93.01μg/kgdry weight. Higher concentrations for most of the targeted PAHs were found close to the suspected emission sources and also along the road connecting them. For pyrene, the correlation between the concentration and the distance from the emission sources could be modelled and visualized using a two-dimensional exponential variogram and ordinary kriging. The range in which the samples were spatially correlated was approximately 500m. Our results show that local emission sources contribute to the spatial distribution patterns of PAHs. Monitoring of pollution by airborne PAHs is therefore needed even in areas far from major pollution sources such as Ilulissat, Greenland. E. nigrum showed to be a feasible species for biomonitoring of PAHs due to its large abundance in the sampling area and its widespread availability in the Artic region.

Direct control of normal fault in hydrocarbon migration and accumulation in northwestern Bozhong subbasin, Bohai Bay Basin, China

Fault growth and reactivation activities have been interpreted as potential controlling factors in vertical hydrocarbon migration, but the coupling and direct comparison of fault growth/reactivation history and hydrocarbon distribution patterns remain poorly understood. The spatial distribution of oil fields in the Western subsag of the Bozhong subbasin in the Bohai Bay Basin is closely related to fault geometry and presents a unique opportunity to investigate the coupling mechanism of the evolution of normal faults and petroleum migration and accumulation. The evolution history of two major normal faults, Faults F1 and F2, was investigated via three-dimensional seismic reflection data, and Fault F2 was associated with the spatial distribution of oil. Quantitative throw analyses, including throw versus distance plots, throw versus depth (T-z) plots, throw contour projections, and expansion indexes (EI) were employed. Fault F2 exhibited a large displacement between the footwall and hanging wall along most of the fault plane and thickened hanging walls of the upper fault surface. Laterally, the fault comprised three segments that linked along the strike at local throw minima. Vertically, the fault formed through the coalescence of two parts via dip linkage. Both the isolated- and coherent-fault models may have contributed to the evolution of Fault F2 during different periods and can be summarized in several steps, including blind fault propagation as individual segments, free surface breaching, lateral and dip linkage, and subsequent frequent reactivation as a coherent structure. A key result of this study was that petroleum migration and accumulation could be directly controlled by multiple growth and reactivation activities of faults.

Inter-maceral effects on hydrocarbon generation as determined using artificial mixtures of purified macerals

Different proportions of purified, low maturity maceral concentrates (∼0.4 %Ro) have been artificially mixed to evaluate changes in the hydrocarbon generation characteristics as a function of maceral-maceral interactions. The purified maceral concentrates (lamalginite [L], detrovitrinite [D] and resinite [R]) were obtained from an Eocene lacustrine oil shale and an Eocene coal sample from NE China. Four artificial mixtures (L:D:R = 80:20:0 wt%, 50:50:0 wt%, 70:25:5 wt%, and 20:80:0 wt% were prepared for analysis. Comparison of the measured and calculated geochemical parameters of artificial mixtures shows that bulk characteristics such as Rock-Eval data, carbon isotope values, Fourier transform infrared (FTIR) parameters, the Py-GC gaseous hydrocarbon content and gas–oil ratios of the maceral mixtures are consistent with the calculated values. However, the Py-GC hydrocarbon distribution patterns of the liquid oil (C5-14) and C15+ fractions show deviations from the expected values. In particular, the Py-GC distribution pattern and n-alkene/n-alkane pattern of the mixtures are similar to that of the purified lamalginite maceral concentrate, even when the lamalginite content in the mixture is low (i.e. 20%). Py-GC of the mixtures with detrovitrinite yields much more of the C15+ fraction than calculated and the deviation is larger in mixtures with a smaller amount of detrovitrinite. It is apparent that the alginite maceral is the main source of hydrocarbons and will strongly influence the hydrocarbon distribution pattern, while the presence of vitrinite could lead to enhanced C15+ hydrocarbon amounts. These results suggest that geochemical properties and generated hydrocarbon amounts can be influenced by the interaction of different organic matter types. Further research is needed to determine the specific chemical/physical nature of these interactions.

Tracing the sources and evolution processes of shale gas by coupling stable (C, H) and noble gas isotopic compositions: Cases from Weiyuan and Changning in Sichuan Basin, China

The source and thermal evolution history of organic matter for the Longmaxi shale are still debated. This study analyzed the molecular and stable carbon isotopic compositions of hydrocarbons (CH4, C2H6, and C3H8) and CO2 as well as the stable hydrogen isotopic compositions of methane, ethane, and noble gases (He, Ne, Ar, Kr, and Xe). Shale gases in the WY and CN areas show an extremely-low-wetness with CH4 concentrations range from 93.41% to 99.01%. Non-hydrocarbon gases are mainly N2 (0.22%–2.81%) and CO2 (0.03%–1.35%). H2S have not been detected. Different δ13C1 and δ13C2 values in WY and CN shale gases (WY: −37.3‰ to −35.0‰ and −40.3‰ to −38.3‰, CN: −29.8‰ to −26.3‰ and −35.3‰ to −32.7‰) and various carbon isotope-composition distribution patterns (δ13C1>δ13C2<δ13C3 and δ13C1>δ13C2>δ13C3) of hydrocarbons indicate a complex evolution process. WY shale gases include more oil-cracking gas than CN shale gases, suggesting WY shale gases more like come from Type I-II organic matter. In shale gas systems, methane content and δ13C1 ratios vary with the degree of thermal evolution, so the origin of shale gas cannot be determined using carbon isotope data alone. The wide range of δ13CCO2 values (−8.9‰ to −0.8‰) and N2/40Ar ratios (20.8–165.1) suggests multiple origins of the gases. Emeishan mantle plume provides the source of heat for some thermo-genic gas. Noble gas isotopic compositions (3He/4He: 0.001Ra to 0.019Ra) indicate air and crustal origins with no significant contribution from the mantle. 40Ar/36Ar ratios (1194.3–4604.5) are consistent with the age of Longmaxi strata calculated by accumulative effect of Ar isotope. The shale gas humidity, carbon isotope ratios, and the carbon isotope-composition distribution patterns may contain information indicating the shale gas sweet spot.

Occurrence, Sources and Exposure Risk of Polycyclic Aromatic Hydrocarbons (PAHs) in Street Dusts from the Nigerian Megacity, Lagos

This study presents the results for the determination of the concentrations and distribution patterns of polycyclic aromatic hydrocarbons (PAHs) in urban street dusts from the Nigerian megacity, Lagos, in order to provide information on their sources, and the potential environmental and human health risks arising from exposure to PAH contaminated dust. Gas chromatography-mass spectrometry was used for the quantification of the levels of PAHs in the dust samples after they were extracted with n-hexane/dichloromethane by ultrasonication. The PAH concentrations in the urban street dusts ranged from 545 to 10785 μg kg−1, 289 to 17943 μg kg−1 and 616 to 13174 μg kg−1 for industrial, commercial, and residential areas, respectively. The risk quotient (RQ) values indicated a moderate to high ecosystem risk for organisms in contact with PAHs in dust from these functional areas. The BaPTEQ and BaPMEQ values indicated potential carcinogenic and mutagenic risks to residents of the megacity. The hazard index (HI) values signify that there is a substantial non-carcinogenic risk relating to exposure of children to PAHs in dusts from the commercial areas, while the lifetime cancer risk factors indicate a considerable cancer risk for human exposure to PAHs via oral ingestion and dermal contact with the dust particles. The source diagnosis, determined from PAH isomeric ratios and multivariate analysis, showed that PAHs in the urban street dust originated from vehicular traffic emissions, burning of biomass, volatilization of petroleum products, and domestic cooking gas.

Distribution patterns of aliphatic hydrocarbons in sediments from a tropical estuarine system

Abstract The Sao Francisco River has historical and economic relevance to the development of Northeast Brazil. However, the dams and reservoirs located along the basin and anthropogenic activities have been affecting its estuary. Herein, 26 surface sediment samples were analyzed to access the origin and distribution of aliphatic hydrocarbons. Concentrations of these hydrocarbons ranged from 0.95 μg g−1 to 2.87 μg g−1 in the summer and from 0.22 μg g−1 to 1.49 μg g−1 in the winter. Diagnostic ratios and indexes indicate higher plants, bacteria, and petroleum as hydrocarbon sources. A positive correlation was also observed between ∑n-alkanes and total organic matter (0.25) and fine fraction (0.47) as well as a significant difference (p

Distribution Pattern, Emission Characteristics and Environmental Impact of Polycyclic Aromatic Hydrocarbons (PAHs) in Download Ash and Dust from Iron and Steel Enterprise.

Download ash and emission dust samples were collected from sintering, coking, ironmaking and steelmaking processes of iron and steel enterprises in Laiwu. Sixteen kinds of polycyclic aromatic hydrocarbons (PAHs) in the United States Environmental Protection Agency (USEPA) priority controlled lists were quantitatively analyzed using Gas Chromatography-Mass Spectrometer (GC-MS). Laser particle size analyzer was used to obtain the distribution pattern of download ash. It was found that the diameter distribution pattern from four production processes was quite different. The proportion of fine particulate (0–2.5 μm) was the highest (72.62%) in the steelmaking refining process, and was 28.962% in the ironmaking process. Moreover, the particle size in download ash from steelmaking refining is all less than 10 μm and that from the ironmaking process was 52.92%. The medium-sized particles (10–100 μm) were dominant in sinter and coking download ashes. The total PAHs (∑16PAHs) mass concentration ranged from 0.49 ± 0.06 to 69.63 ± 5.57 μg·g−1 in download ash samples, and varied from 2.815 ± 0.253 to 19.429 ± 2.545 μg·m−3 in emission dust samples. The ∑16PAHs values were both largest in download ash and dust emission from the coking process (69.63 ± 5.57 μg·g−1 and 19.429 ± 2.545 μg·m−3, respectively). The most abundant individual PAHs were benzo[b]fluoranthene, benzo[k]fluoranthene, phenanthrene, benzo[a]anthracene in ash samples, and benzo[a]anthracene, benzo[k]fluoranthene, benzo[b]fluoranthene and indeno[1,2,3-cd]pyrene in emission dust samples. Dominant compounds were high-molecular weight (four- to six-ring) PAHs in both ash and dust samples. The concentration order of individual compounds in PM10 and PM2.5 in ambient air around the steel plant was completely consistent with each other, and the concentration of ∑16PAHs was the highest in the steel plant and lowest in Daqin village because of upwind of the steel plant. The concentrations of benzo[b]fluoranthene and fluoranthene in ambient air were comparatively high, and were in accordance with the higher concentration of the two monomers in the download ash samples, which suggested that the effect of the emission flue gas from the steel plant on ambient air was necessary to concern.

Grassland fire ecology has roots in the late Miocene

That fire facilitated the late Miocene C4 grassland expansion is widely suspected but poorly documented. Fire potentially tied global climate to this profound biosphere transition by serving as a regional-to-local driver of vegetation change. In modern environments, seasonal extremes in moisture amplify the occurrence of fire, disturbing forest ecosystems to create niche space for flammable grasses, which in turn provide fuel for frequent fires. On the Indian subcontinent, C4 expansion was accompanied by increased seasonal extremes in rainfall (evidenced by δ18Ocarbonate), which set the stage for fuel accumulation and fire-linked clearance during wet-to-dry seasonal transitions. Here, we test the role of fire directly by examining the abundance and distribution patterns of fire-derived polycyclic aromatic hydrocarbons (PAHs) and terrestrial vegetation signatures in n-alkane carbon isotopes from paleosol samples of the Siwalik Group (Pakistan). Two million years before the C4 grassland transition, fire-derived PAH concentrations increased as conifer vegetation declined, as indicated by a decrease in retene. This early increase in molecular fire signatures suggests a transition to more fire-prone vegetation such as a C3 grassland and/or dry deciduous woodland. Between 8.0 and 6.0 million years ago, fire, precipitation seasonality, and C4-grass dominance increased simultaneously (within resolution) as marked by sharp increases in fire-derived PAHs, δ18Ocarbonate, and 13C enrichment in n-alkanes diagnostic of C4 grasses. The strong association of evidence for fire occurrence, vegetation change, and landscape opening indicates that a dynamic fire-grassland feedback system was both a necessary precondition and a driver for grassland ecology during the first emergence of C4 grasslands.

Distribution pattern and health risk assessment of polycyclic aromatic hydrocarbons in the water and sediment of Algoa Bay, South Africa

Polycyclic aromatic hydrocarbons are amongst the pollutants of major concern in the terrestrial and aquatic habitats. They are mostly characterised by carcinogenic and non-carcinogenic effects. Distribution and potential health risks of sixteen priority PAHs in the water and sediment samples collected between December 2015 and June 2016 from Algoa Bay, South Africa, were evaluated. Water and sediment samples collected were extracted with liquid–liquid and soxhlet extraction methods, respectively, and then cleaned up using glass column loaded with silica gel. Final concentrations of the target PAHs were determined by gas chromatography interfaced with flame ionization detector. Results indicated that individual PAH concentrations in surface water, bottom water and sediment samples ranged from not detected (ND) to 24.66 µg/L, ND to 22.81 µg/L and ND to 5.23 mg/kg correspondingly. Total PAHs concentrations varied as 12.78–78.94 µg/L, 1.20–90.51 µg/L and 1.17–10.47 mg/kg in the three environmental matrices in that order. The non-carcinogenic risk was generally below 1, whereas risk indices (dermal contact) were above the acceptable limit of 1 × 10−4 in the water column, suggesting possible carcinogenic effects to humans, with adults being the most vulnerable. Similarly, highest contributions to TEQs and MEQs in the sediments were made by benzo(a)pyrene and dibenzo(a,h)anthracene, the two most toxic congeners, signifying the possibility of carcinogenicity and mutagenicity in humans. Diagnostic ratios of PAHs reflect a prevailing pyrogenic input all through. The pollution was albeit moderate, yet regular check is recommended to ensure safe and healthy environment for human and aquatic lives.

Hydrocarbon distribution pattern and logging identification in lacustrine fine-grained sedimentary rocks of the Permian Lucaogou Formation from the Santanghu basin

A series of qualitative descriptions and quantitative analyses was used to determine the lithofacies characteristics and hydrocarbon distribution pattern of Lucaogou Formation fine-grained sedimentary rocks in the Santanghu Basin. The qualitative descriptions include core description, petrographic thin section observation, fluorescence observation, cathode luminescence observation and scanning electron microscope (SEM) observation. The quantitative analyses include X-ray diffraction, total organic content analysis, programmed pyrolysis, Soxhlet extraction, vitrinite reflectance, maceral composition, porosity and permeability analysis, and oil saturation analysis.Three main types of lithofacies were identified in this study area: organic-rich massive tuffaceous shale lithofacies (RMTSL), organic-rich laminated and cloddy diamictite lithofacies (RLCDL) and organic-lean massive dolomite lithofacies (LMDL). RMTSL mainly includes massive shale and tuffaceous shale. Quartz and clay minerals are the major components of rocks from this lithofacies. RLCDL develop lamina and a cloddy structure. Rocks from this lithofacies chiefly consist of dolomite and quartz. LMDL mainly contains massive bedding fine-grained carbonate rocks. Dolomite accounts for the main portion of these rocks. RMTSL contains the highest content of free hydrocarbon and solid organic matter. Moreover, higher porosity was observed in RMTSL. LMDL contains the lowest solid organic matter content and develops the least pores. RLCDL develop the largest number of cracks and fractures.Resistivity logging (RD) combined with tri-porosity logging suites were finally selected to differentiate the three lithofacies. The response characteristics of RMTSL should be high acoustic time (AC), low density (DEN), high compensated neutron logging (CN) and high resistivity logging (RD). On the contrary, the response characteristics of LMDL are low acoustic time (AC), high density (DEN), low compensated neutron logging (CN) and low resistivity logging (RD).Commercial oil production mainly appears in RMTSL. Uplift belts that are away from erosion areas and develop thick RMTSL will be the area with the most potential. Hence, the Mazhong uplift belt is the most favourable area for the accumulation of hydrocarbon on a large scale.

Distribution pattern and mass budget of sedimentary polycyclic aromatic hydrocarbons in shelf areas of the Eastern China Marginal Seas

AbstractThis study conducted the first extensive and comprehensive investigation of the regional‐scale sedimentary polycyclic aromatic hydrocarbons (PAHs) concentration, flux, and budget in the continental shelves of the Eastern China Marginal Seas (ECMSs). Surface sediment samples from multiple sites were collected and assessed, and the latest data from current research were assessed. The spatial distribution pattern of PAHs in the ECMSs was significantly influenced by the regional hydrodynamics, sediment properties (grain‐size, total organic carbon [TOC] content, and sedimentation rate), and anthropogenic impacts. Relatively higher PAHs concentrations occurred in areas with fine‐grained sediment. Results of source apportionment found that the relative proportions of PAHs showed significant regional variation, mainly influenced by socioeconomic differences between north and south China. The PAHs burial flux in the study area ranged from 11.2 to 1308 ng cm−2 yr−1 with an average value of 101 ± 104 ng cm−2 yr−1. The area‐integrated sedimentary PAHs burial flux across the ECMSs was 494 t yr−1. A mass budget calculation revealed that riverine input and atmospheric deposition were the most significant sources contributing, 28.4% and 71.6%, respectively. The study demonstrated that net PAHs transportation occurs between the Bohai Sea (BS) and Yellow Sea (YS), with a flux of approximately 10.2 t yr−1. PAHs were also transported from YS to the East China Sea (ECS), due to water exchange between the YS and ECS. Additionally, substantial amounts of PAHs in the inner shelf of the ECS were transported out of the shelf area due to cross‐shelf plume.

Distribution Patterns of Polycyclic Aromatic Hydrocarbons in Marshy Soil and Sediments in Warri, Southern Nigeria

Distribution Patterns of Polycyclic Aromatic Hydrocarbons in Marshy Soil and Sediments in Warri, Southern Nigeria