Hydrocarbon Biomarkers Research Articles

A NEW HOMOLOGOUS SERIES OF HOPANOIDS (HYDROCARBON BIOMARKERS) IN OILS AND NATURAL BITUMENS OF THE NORTHEASTERN SLOPE OF THE ALDAN ANTECLISE

Oil and bitumen shows with previously unknown hydrocarbon biomarkers – 9-­methyl, 8-14-secohopanes – were encountered in the sections of hydrogeological wells on the northeastern slope of the Aldan anteclise. Shows of biodegraded asphaltites are confined to the cavernous horizon in the middle Cambrian limestones of the Tankhai Formation. The relatively high residual concentrations of the “new” biomarkers are due to their very high resistance to biologic oxidation processes. Geologic materials and geochemical data on the studied naphthides suggest that in the region under consideration there is a typical oil deposit sealed in the “head” of the cavernous horizon by highly viscous bitumens.

Organic petrographic and geochemical insights into organic matter derived from land plants and marine algae in the Lark Formation, Danish North Sea

Climatic fluctuations from the Eocene to the Miocene highlight the importance of investigating the paleoenvironment of the latest Eocene to the Middle Miocene Lark Formation in the Danish North Sea. This study investigates immature sedimentary organic matter in the Lark Formation using 54 cuttings samples and one core sample collected from seven wells in the eastern North Sea Basin. Organic petrography and molecular geochemistry analyses were performed to determine the variations in the quantity and origin of allochthonous and autochthonous organic matter. Additionally, the study assesses the impact of climate fluctuations on marine productivity in the eastern North Sea Basin and land plant vegetation at the basin margins during the latest Eocene to the Middle Miocene.The organic matter in the Lark Formation originated from mixed sources, primarily land plants, with a secondary contribution from marine algae. This is indicated by the maceral composition and the types and abundance of aliphatic and aromatic hydrocarbon biomarker compounds. Moreover, the presence of diterpenoids (gymnosperm biomarkers) and non-hopanoid triterpenoids (angiosperm biomarkers) reveals that the allochthonous organic matter originated from conifers and angiosperms.Climatic impacts on land plants and marine algae during the latest Eocene to the Middle Miocene are revealed by several parameters: the Averaged Chain Length (ACL) of land plant waxes, the proportion of coniferous contribution (C/(C + A)), and the whole rock volume percentages of huminite, inertinite (H + I, vol%) and liptinite (L, vol%). The shifts to cooler and drier climates highlighted the cold adaptation of onshore conifers and resulted in the input of higher molecular weight waxy components into the sediments. However, under these conditions, reduced precipitation and runoff resulted in lower amounts of terrigenous organic matter supplied to the basin. Additionally, the drop in water temperature and the warm-affinity of local algae assemblage led to reduced marine productivity. Together, these factors contributed to an overall decrease in organic richness. In contrast, during shifts to warmer and more humid climates, the trend reversed. The contribution of conifers to the floral assemblage diminished, but higher amounts of terrigenous organic matter were transported to the basin due to increased precipitation and runoff. This was accompanied by warmer water temperatures, boosting the productivity of organic-walled microplankton in the marine environment and contributing to greater organic richness.

Associations among urinary polycyclic aromatic hydrocarbon biomarker concentrations and birth outcomes in LIFECODES

Associations among urinary polycyclic aromatic hydrocarbon biomarker concentrations and birth outcomes in LIFECODES

Biomarker Hydrocarbons and Carbon Isotopes of Individual n-Alkanes in Paraffin Oils and Bitumens of the Middle Devonian–Lower Frasnian Terrigenous Complex of the Timan–Pechora Basin

Abstract ––The objects of study were bitumens of sedimentary rocks and paraffin oils of the Middle Devonian–lower Frasnian terrigenous complex of the Timan–Pechora basin. We studied the composition of biomarker hydrocarbons and the carbon isotope composition of individual n-alkanes of bitumens from the cores of the wells of the Omra–Lyzha saddle. The results were compared with similar data on the composition of paraffin oils from the south of the Pechora–Kozhva megaswell. The generation potential and thermal maturity of organic matter were studied by the Rock-Eval pyrolysis method. The maturity of organic matter in the rocks of the studied complex in the Omra–Lyzha saddle and the Pechora–Kozhva megaswell corresponds to the oil window. Data on the carbon isotopy of n-alkanes and on the composition of biomarker hydrocarbons do not contradict the possible genetic relationship between paraffin oils and the organic matter of the host sedimentary complex. Both the studied paraffin oils and the rock bitumens contain early eluting rearranged hopanes atypical of oils of other petroliferous complexes and show high contents of n-alkanes relative to iso-alkanes and polycyclic biomarkers. The content of 13C tends to decrease with an increase in the number of carbon atoms in the n-alkane molecule in both oils and bitumen rocks.

Associations between urinary hydroxylated polycyclic aromatic hydrocarbon biomarker concentrations and measures of timing of delivery and infant size at birth

Preterm birth is a leading cause of neonatal mortality and presents significant public health concerns. Environmental chemical exposures during pregnancy may be partially to blame for disrupted delivery timing. Polycyclic aromatic hydrocarbons (PAHs) are products of incomplete combustion, exposure to which occurs via inhalation of cigarette smoke and automobile exhaust, and ingestion of charred meats. Exposure to PAHs in the US population is widespread, and pregnant women represent a susceptible population to adverse effects of PAHs. We aimed to investigate associations between gestational exposure to PAHs and birth outcomes, including timing of delivery and infant birth size. We utilized data from the PROTECT birth cohort where pregnant women provided spot urine samples at up to three study visits (median 16, 20, and 24 weeks gestation). Urine samples were assayed for eight hydroxylated PAH concentrations. Associations between PAHs and birth outcomes were calculated using linear/logistic regression models, with adjustment for maternal age, education, pre-pregnancy BMI, and daily exposure to environmental tobacco smoke. Models accounted for urine dilution using specific gravity. We also explored effect modification by infant sex. Interquartile range (IQR) increases in all averaged PAH exposures during the second trimester were associated with reduced gestational age at delivery and increased odds of overall PTB, although these associations were not statistically significant (p > 0.05). Most PAHs at the second study visit were most strongly associated with earlier delivery and increased odds of overall and spontaneous PTB, with visit 2 2-hydroxynapthalene (2-NAP) being significantly associated with increased odds of overall PTB (OR:1.55; 95 %CI: 1.05,2.29). Some PAHs resulted in earlier timing of delivery among only female fetuses, specifically 2-NAP on overall PTB (female OR:1.52 95 %CI: 1.02,2.27; male OR:0.78, 95 %CI: 0.53,1.15). Future work should more deeply investigate differential physiological impacts of PAH exposure between pregnancies with male and female fetuses, and on varying developmental processes occurring at different points through pregnancy.

Geochemistry and accumulation of the ultra-deep Ordovician oils in the Shunbei oilfield, Tarim Basin: Coupling of reservoir secondary processes and filling events

Ultra-deep (7300 m–8900 m) condensed and volatile oil reservoirs have been discovered in the Ordovician reservoirs of the Shunbei oilfield, in the Tarim Basin. This study describes the petroleum accumulation process in the Shunbei oilfield by combining an analysis of its geochemical characteristics with seismic section observations and an analysis of petroleum filling events. Geochemical techniques are used to determine the sources, maturity, secondary processes, accumulation periods, and timing of petroleum filling. Analysis of fluid inclusion homogenization temperatures and burial-thermal histories indicates distinct petroleum filling events. Specifically, the north sub-section of the No. 5 fault zone experienced two petroleum filling periods during the late Caledonian and Indosinian epochs while the No. 1 fault zones and the mid-south sub-sections of the No. 5 fault zones experienced three distinct filling periods, encompassing the late Caledonian, Indosinian, and Himalayan periods. The CO2 concentrations and δ13CCO2 values suggest the presence of secondary microbial gases, primarily thermogenic gases. Gas component analysis reveals a transition from kerogen degradation gas to oil cracking gas from north to south. The detection of intact n-alkanes and compounds of the 25-norhopanes series in oil samples suggests a mixture of early biodegradable oil with late fresh oil in the area. Seismic sections reveal diabase intrusions with strong axial reflections. Local hydrothermal activities during the Permian era rapidly cracked saturated hydrocarbon biomarkers, forming polycyclic aromatic hydrocarbons in the oil. Hydrothermal activity in the south sub-section of the No. 5 fault zone depleted the hydrocarbon-generating capacity of the underlying source rocks. Petroleum charged during the Indosinian period likely originated from potential petroleum reservoirs in the Cambrian system. This explains the comparatively low temperature of the SHB57X reservoir (163.32 °C) and the lack of strong hydrothermal activity in the late stage, but no biomarkers of the second-stage charged oil have been detected. Biomarker detection and gas genesis in the mid-south sub-section of the No. 5 fault zone and in the No. 1 fault zone suggest weak or no hydrothermal activity, with Cambrian source rocks maintaining their hydrocarbon generation capacity. Gas filling in the Himalayan period caused evaporative fractionation in the original reservoirs, resulting in a disproportionate (2-MH+2,3-DMP)/(3-MH+2,4-DMP), producing high K1 values in the light hydrocarbons in the present petroleum reservoirs. Differences in gas charging events in the Himalayan period led to the present distribution of petroleum phases.

Biological origin and depositional environment of crude oils in the Qiongdongnan Basin: Insights from molecular biomarkers and whole oil carbon isotope

Molecular biomarker and whole oil carbon isotope (δ13Coil) analyses were conducted on eleven typical crude oils from the Qiongdongnan Basin to investigate their biological sources and depositional environments. Saturated hydrocarbon biomarkers in most samples are characterized by angiosperm-derived compounds, with aromatic compounds dominated by the naphthalene, phenanthrene, biphenyl, and fluorene series. The related source rocks of these oils were mainly deposited under oxic condition, but a subanoxic–suboxic and enclosed water column condition in the Central Depression during Oligocene. The identification of simonellite and related compounds in the aromatic fractions provides reliable evidence for the input of coniferous gymnosperms. Cadalene may also have a potential association with gymnosperms since it shows a strong positive correlation with simonellite. Evidence from density, n-alkanes, short-chain alkylbenzenes and secondary brine inclusions indicates that the unique crude oil B13-1 may have suffered from thermal alteration. These crude oils (excluding B13-1) can be classified into four types based on the δ13Coil values and molecular biomarkers. Type A oil (solely S34-3) is characterized by non-angiosperm plants, with minor dinoflagellates and increasing contribution from conifer gymnosperms than others. Type B oils (L17-2, L18-1, L25-1, and L25-1W) show heavy δ13Coil (−24 ‰ to −25 ‰) and mixed contributions from both angiosperms and marine algae, with the marine algae contribution increasing. Type C oils (L13-2 and B21-1) share similar biological sources with Type B, but the moderately δ13Coil (−25‰ to −26‰) and high level of terrestrial biomarkers suggesting a predominant contribution of angiosperms. Type D oils (Y13-1a, Y13-1b, and Y13-4) possess the lightest δ13Coil (mainly below −26‰) and are primarily derived from angiosperms, with mangrove vegetation playing an important role. Spearman correlation analysis among 14 source biomarker parameters with δ13Coil and geological setting of related source rocks implied that the marine algae should be responsible for the heavy δ13Coil in the Type B. The contribution of marine algae in the Central Depression may have been neglected in the past, as it is usually covered by remarkable angiosperm biomarkers.

Organic matter sources and distribution along land-use gradient in a Himalayan foothills River: Insights from molecular markers

The analysis of hydrocarbon biomarkers in surface sediments along the Markanda River in the foothills of the Indian Himalayas was conducted to gain insights into the distribution and composition of organic matter (OM) within the sediments. This investigation is essential for comprehending how anthropogenic changes are influencing the OM dynamics in river systems. The study involved identification and quantification of various compound groups such as n-alkanes, hopanes, steranes, polycyclic aromatic hydrocarbons (PAHs), linear alkyl benzenes (LABs) and phthalate esters along with their respective parametric ratios. The variation in distribution of n-alkanes and associated indices (odd-even carbon number predominance (OEP), average chain length (ACL), terrigenous to aquatic ratio (TAR), carbon preference index (CPI), and natural n-alkanes ratio (NAR)) were used to distinguish the natural source of organic content from those influenced by anthropogenic contamination. The detection of petroleum contamination was indicated by the presence of prominent unresolved complex mixtures (UCM) as well as specific petroleum biomarkers such as hopanes, diasteranes, and steranes. The study revealed varying concentrations of the analyzed organic pollutants, with the average of PAHs at 24.6 ng/g dw, LABs at 18.1 ng/g dw, and phthalates at 8.3 μg/g dw. The variability in concentration of the investigated compound groups across different locations indicated spatial heterogeneity, and the land use patterns appears to modulate the sources of OM in surface sediments. The source contribution of PAHs and phthalates determined by positive matrix factorization (PMF) shows the predominant sources of the anthropogenic hydrocarbons were linked primarily to petroleum/petroleum-derived products emissions, industrial discharges, cultural practices and common household waste/sewage disposal. This analysis provides insights for developing mitigation strategies and informing relevant policy changes globally, thereby contributing to the broader understanding of anthropogenic impacts on water ecosystems.

Geochemical Characteristics of Mesoproterozoic Source Rocks in North China: Insights for Organic Matter Enrichment and Thermal Evolution

In recent years, the exploration of oil and gas in China’s Precambrian strata has garnered significant attention, leading to notable advancements in exploration play assessment. However, there is a dearth of published literature on Proterozoic source rocks’ organic sources, sedimentary environments, marine hydrochemistry, and other attributes. This study focuses on investigating potential source rocks within the Hongshuizhuang and Xiamaling Formations in the Jibei Depression of North China. A comprehensive analysis was conducted to evaluate hydrocarbon generation characteristics, using hydrocarbon biomarkers and polar compounds as geochemical indicators for precursor biota and maturity levels. The results indicate high organic matter abundance with predominantly type I-II1 organic matter composition in the studied source rocks. These samples are at an immature–low mature stage, with the potential for primarily generating aromatic crude oil. The parent material is mainly attributed to lower aquatic organisms, such as bacteria and algae. The sedimentary environment exhibits marine facies, characterized by high evaporation rates, salinity levels, and strong euxinic conditions, that led to sulfur incorporation into the organic matter matrix. It should be noted that correlations between biomarker parameters and maturity may not be fully applicable to ancient source rocks; however, the methyldibenzothiophene ratio (MDR) demonstrates a strong correlation with Tmax. The compounds and their total monoisotope ions abundance (TMIA) were primarily identified and analyzed using FT–ICR MS. It was observed that these compounds were influenced by the depositional environment and organic matter maturity. Importantly, it was clearly demonstrated that the DBE and carbon number range of CH compounds gradually increased with maturity, due to the removal of N, S, and O functional groups. Specifically, N1 compounds predominantly consisted of carbazoles with short alkyl side chains which readily converted into N1Ox compounds. On the other hand, O1 compounds mainly comprised benzofurans with low abundance, indicating a reducing sedimentary environment, as suggested by their low TMIA values. Furthermore, S1 compounds were primarily thiophenes whose DBE range and carbon number increased with maturity, possibly suggesting an abiotic input of inorganic sulfur. Notably, the maturity indices (MAT) proved suitable for Mesoproterozoic source rocks while exhibiting strong linear relationships.

Petroleum Potential and Organic-Matter–Oil Correlation in the Rocks of the Upper Riphean Iremeken Formation in the Kamo Arch of the Baikit Anteclise (Siberian Platform)

Abstract —A complex of laboratory studies of Riphean rocks and oils was carried out by the organic-geochemistry methods to construct a basin model for the Kamo arch of the Baikit anteclise of the Siberian craton. We compared the parameters of the organic matter (OM) and oils of the Upper Riphean Iremeken carbonaceous member by biomarker hydrocarbons. Analysis of the obtained chromatography–mass spectrometry data showed an unordinary group hydrocarbon composition of extracts from the OM and oils and low contents of cheilanthanes and steranes in them. Within the Kamo arch, the Upper Riphean Iremeken OM-enriched deposits with a high petroleum potential might have reached the peak of petroleum generation only in the deepest part of the Madra trough; thus, the traps could not be completely filled with oil. The distribution of tricyclic terpanes in the rock bitumens from the studied wells testifies to immature OM in the Iremeken Formation. However, in the most submerged zones of the Kamo arch and in the adjacent areas, oil was generated from the OM of the Iremeken Formation. This is evidenced by the oils of the Upper Iremeken Subformation in the Kuyumbinskoe field and the Ter’-Kamo license area.

Structural characterization of steranes and hopanes in petroleum by ion mobility mass spectrometry

The structural characterization of hydrocarbon biomarkers with high molecular weight still remains a challenge even using the ultrahigh resolution mass spectrometry (UHRMS). In this work, a homologue series identification strategy was proposed based on the “sequentiality” of crude oil, where “sequentiality” revealed a compositional continuum of the naturally existing components in crude oil. With the steady increase of mass to charge ratio (m/z), the collision cross-section (CCS) value was measured by trapped ion mobility mass spectrometry (TIMS-MS) and showed a linear relationship with m/z. The structure of C20-C34 steranes and C27-C38 hopanes was determined using linear correlation. The accuracy of molecular formula was confirmed by UHRMS, and the structural determination was verified by MS/MS. The identification of sterane series and hopane series demonstrated the application of the homologue series identification strategy in the structural determination of hydrocarbon biomarkers with high molecular weight. Compared with gas chromatography-mass spectrometry (GC–MS) within the GC-able reach, the new analytical strategy showed better qualitative results and comparable quantitative results, which made it promising to explore novel hydrocarbon biomarkers in crude oil.

Oil-source correlations and petroleum accumulation in oil sands in the Carboniferous Yanghugou Formation in the Shajingzi area, Ordos Basin, China

The south-central part of the western Ordos Basin is an important structural belt. Recent drilling of Well YT2 in the Shajingzi area of this belt has led to the discovery of oil sands in the Carboniferous Yanghugou Formation. In this study, Paleozoic source rocks and oil sands were sampled from the Well YT2 and analyzed for oil-source correlations. Geochemical data including saturate and aromatic biomarker compositions were used to investigate the genetic origins of oil sands. Saturated hydrocarbon biomarkers, such as n-alkanes, isoprenoids, tricyclic terpanes and C27-C28-C29 regular steranes, indicate that the oil and source rocks in the Ordovician Wulalike Formation are similar in terms of maturity, provenance and sedimentary environment. Aromatic parameters, such as dibenzothiophene/phenanthrene and alkyldibenzothiophene/alkyldibenzofuran ratios in the oil are similar to those in source rocks in the Carboniferous Yanghugou Formation and the Permian Taiyuan Formation. Moreover, retene is direct evidence that the oil has originated in part from the Yanghugou and/or Taiyuan formations. In addition, the modelled accumulation ages indicate that that the maturity of the two types of oil inclusions is consistent with the source rocks of the Wulalike, Yanghugou and Taiyuan formations during the charging times. The thrust faults runs through the Wulalike, Yanghugou and Taiyuan formations can provide pathways for oil migration. Therefore, the oil from the Yanghugou Formation has a mixed source from the Wulalike, Yanghugou and/or Taiyuan formations. This is the first documented discovery of Ordovician marine oil in the Ordos Basin.

Comparison of the Hydrocarbon Distribution in Thermolysis Products of Asphaltenes, Resins, and Acids Isolated from Weakly Transformed Crude Oil from the Anastasievsko-Troitskoe Oil Field (Horizon IV)

Regular trends in the distribution of hydrocarbon biomarkers (n-alkanes, isoprenanes, steranes, and terpanes) and hydrocarbons of the adamantane series in low-maturity crude oil from the Anastasievsko-Troitskoe oil field (horizon IV) and in products formed by thermolysis of asphaltenes, resins, and acids from this oil were studied by gas chromatography–mass spectrometry. Thermolysis of high-molecular-mass oil precursors yields the same hydrocarbons (HCs) as those present in the initial oil, and also protoadamantanes (precursors of adamantanes). HCs of the adamantane series are not formed, and their presence in this crude oil is due to their supply from other oil source strata. The experiments show that the n-alkanes present in the initial oil in small amounts are released under more severe conditions.

Quantification of C10–C14 Adamantanes in High-Viscosity Naphthenic Oils

The paraffin–naphthenic fractions (with boiling points below 310°C) prepared from three high-viscosity naphthenic crude oils, classified as types B1 and B2 (according to Petrov’s classification), were subjected to thiocarbamide complexation. The molecular composition of polycyclic hydrocarbon biomarkers and C11–C13 adamantanes in the oil samples suggested a predominantly marine genotype of the precursor organic matter (OM). The molecular composition also suggested source rocks of a clayey type. Nonetheless, the biomarkers detected in one sample indicated some contribution of terrigenous components to the precursor OM. All the oils were generated under the conditions of the main oil generation zone and, presumably, underwent microbial transformations in the deposits. The compositions of C10–C14 adamantanes in the initial paraffin–naphthenic fraction, in the thiocarbamide adduct, and in the filtrate that remained after the adduction were comparatively characterized for each oil sample. The test conditions allowed us to have adamantane more than 100-fold concentrated (in the adduct), to quantify it in the oils, and to evaluate the concentrations of C11–C14 alkyladamantanes in the oils using adamantane as an internal standard. C10–C14 adamantanes exhibited selective adduction ability, with the extraction ratios of individual components being different. Taking into account these extraction ratios, the component concentrations were evaluated on crude oil basis: 2.7 to 7.6×10–3 wt % for adamantane and 87 to 267×10–3 wt % for total C10–C14 adamantanes. The identification of adamantanes in the initial paraffin–naphthenic fractions, adducts, and filtrates revealed the presence of some other tricyclanes (probable precursors of alkyladamantanes) as well as decaline homologues. Like adamantanes, these compounds exhibited selective ability to complex with thiocarbamide.

Crude Oils of Domanik Genotype from Middle Devonian Deposits of the Timan–Pechora Oil-and-Gas Province

The composition of biomarker hydrocarbons in crude oil samples from Middle Devonian deposits of the Western Tebuk, Dzh”er, and Michayu oil fields of the Omra–Lyzha saddle in the Timan–Pechora oil-and-gas province was studied. Significant effect of the Upper Devonian Domanik source rocks on the formation of the composition of these crude oils was revealed. The main parameters demonstrating the genetic relationship of the oils from Middle Devonian reservoirs with this source rocks are distribution of steranes С27 : С28 : С29, ratio of isoprenoid to normal alkanes, and distribution of normal alkanes. All these characteristics sharply distinguish the crude oils under consideration from paraffinous oils syngenetic to Middle Devonian deposits, characteristic of deposits in the southern part of the Pechora–Kozhva megarampart.

Aliphatic Biomarker Signatures of Crude Oil from Tarakan Subbasin, Tarakan Basin, North Kalimantan, Indonesia

Organic geochemical studies of crude oil from Pamusian Field, Tarakan Subbasin, Tarakan Basin, North Kalimantan, have been done. Biomarker aliphatic hydrocarbon fractions were identified using a combined gas chromatography-mass spectrometer (GC - MS). Identified biomarkers consist of n-alkane groups, isoprenoids, bicyclic sesquiterpenoids, and pentacyclic triterpenoids. The most abundant aliphatic hydrocarbon biomarker is pristane followed by n-C19. The existence of n-alkanes shows a homologous (n-C16- n-C30) with a unimodal distribution type. The abundance of n-C19 is higher than other n-alkanes, supported by LHCPI value of 2.03, as an indicator of organic matter derived from microbial organisms. The amount of long chain n-alkanes (n-C25- n-C30) is almost the same as medium chain n-alkanes (n-C19 - n-C24) indicating the source of organic compounds is not only from microbial organisms, but also from terrestrial higher plants. The presence of 8β (H)-drimane compounds together with homodrimane shows the presence of bacterial input on the formation of oil from organic compounds. Ratio of Pr/Ph is 3.76, ratio of drimane/homodrimane is 1.058, ratio of Pr/n-C17 is 34.41, and ratio of Ph/n-C18 is 16.02 indicating the source of organic compounds came from terrestrial higher plants deposited in the oxic environment, and disposed to increase biodegradation. The CPI value is 0.95, and the highest amount of 17α (H), 21β (H)-hopane compounds suggest that Tarakan Subbasin oil was mature, and the source of organic compounds was derived from bacteria Keywords: Tarakan Basin, organic geochemistry, aliphatic hydrocarbon fraction, CPI

The effect of polycyclic aromatic hydrocarbon biomarkers on cardiovascular diseases.

Polycyclic aromatic hydrocarbon (PAHs) are part of particulate matter (PM), which is produced from incomplete combustion of organic matter. Biomarkers mean biological indicators, molecules that indicate a normal or abnormal process in the body and may be a signof a condition or disease. Studies show that PAHs increase the risk of cardiovascular diseases through processes such as oxidative stress, inflammation andatherosclerosis. The present study focused on the evaluation of health effects PAHs biomarkers on cardiovascular diseases (CVD). In this narrative study, data werecollected from databases such as Scopus, PubMed, Web of science and Google Scholar in the period 1975-2023. After screening, duplicate and irrelevant articles were removed. Finally, 68 articles related to the effect of PAHs on CVD were included in the study. In addition to the articles found through the search in databases, another 18 articles from the references of the selected articles were included. According to the finding in during the biotransformation of PAH, a number of metabolites are made, such as phenols, diols, quinones, and epoxides. Phenolic isomers have the highest percentage and biomarkers used for their detection include 2-OHNAP used totrace naphthalene from heating processed food, 3-OHPHEN used to trace phenanthrene fromdiesel, 2-OHFLU used to trace fluorene and 1-OHPYR used to trace pyrene from cigarette and hookah smoke. According to the result, increasing blood pressure and heart rate and causing atherosclerosis are the main complications due to exposure to PAH metabolite on cardiovascular system. The most important agents that causes this affects including increased homocysteine, cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), serum biomarkers of C-reactive protein, and triglycerides. Result this study showed that cardiovascular diseases riskis increased by exposure to PAH biomarkers from smoking, car emissions, occupational exposure, and incinerators. Therefore, strict controls should be implemented for sources of PAH production and exposure.

Origin and Geological Significance of Residual Oil in High-Angle Joint Fissures: A Case Study of the Nadu Formation in Baise Basin, South China

The Baise Basin is a Paleogene pull-apart basin with numerous strike-slip faults which are not favorable for hydrocarbon preservation. The Nadu Formation, research object of this paper, is generally rich in oil and contains a large number of high-angle joint fissures. Analyzing the origin of residual oil in high-angle joint fissures can reveal the hydrocarbon migration and accumulation characteristics of the pull-apart-type basins. Molecular geochemical composition characteristics of crude oil and oil source of the Nadu Formation were discussed based on the saturated hydrocarbon biomarker compound and stable carbon isotope distribution of n-alkanes. The studied samples were selected from four members (E2n1, E2n2, E2n3up, and E2n3low) of the Nadu Formation. The results suggested that the average oil content of E2n1 fissures is 0.32 mg/cm2, and the oil distribution is not uniform. The distribution of oil on the fissures of E2n2 and E2n3 is uniform and complete, and the oil content reaches 0.53 mg/cm2. The oil in the joint fissures of the Nadu Formation is heavy, as the light hydrocarbon is seriously lost during migration. Thus, the oil in the joint fissures is residue after crude oil loses light components during migration. By comparing the molecular biomarker characteristics and stable carbon isotopic compositions, crude oil of the Nadu Formation can be classified into three categories: E2n1, E2n2 + E2n3up, and E2n3low. The E2n1 oils have the lowest maturity and are sourced from the E2n1 source rocks. Moreover, the maturity of E2n2 and E2n3 samples are relatively high. Biomarker and carbon isotope characteristics of the E2n2 and E2n3up oils are similar, indicating that they are derived from the E2n2 + E2n3up source rocks. The E2n3low oils are the mixture of the crude oil generated from the E2n3up source rocks and the E2n3low source rocks. Results presented show that the residual oil of high-angle joint fissures in the Nadu Formation is contributed by adjacent source rocks. The crude oil discharged from the Nadu Formation can only migrate upward along high-angle joints in a short distance, and the migration distance is usually less than 5 m. In conclusion, although the Nadu Formation has developed a large number of high-angle joint fissures, crude oil in the Nadu Formation has not vertically migrated for long distance along the joint fissures. The well-preserved fractures as important shale oil storage spaces indicate that the Nadu Formation has good shale oil exploration potential. The results may provide insights into the origins of hydrocarbons in the Nadu Formation from the Baise Basin and enhanced knowledge for optimizing future exploration and production.

Geochemical records of human-induced environmental changes in two small remote lakes of Songnen Plain, Northeast China.

The abundance and composition of aliphatic hydrocarbon biomarkers were determined in dated sediment cores from Lakes Qijiapao (QJP) and Huoshaoheipao (HSH) in the Songnen Plain, Northeast China, to investigate historical environmental changes in these lakes and identify likely controlling factors. Based on these results, the recent environmental history of the two lakes can be divided into three periods. Before 1950, low Paq values (avg. 0.23 and 0.27, respectively) and middle-chain n-alkane abundances (normalized to total organic carbon, avg. 14.82 and 16.01µgg-1 TOC, respectively) in both lakes suggested low aquatic productivity and the limited input of submerged macrophyte organic matter (OM). However, the significant increase in the abundance of short-chain n-alkanes in Lake HSH (from 8.34 to 16.68µgg-1 TOC) indicated the emergence of early nutrient enrichment in the lake. From 1950 to 2000, marked increase in the abundance of middle-chain n-alkanes (avg. 21.72 and 22.62µgg-1 TOC in Lakes QJP and HSH, respectively) and Paq values indicated that both lakes had undergone eutrophication because of the population explosion and agricultural intensification. From 2000 to 2013, the abundance of short- and middle-chain n-alkanes in Lake QJP markedly exceeded those in Lake HSH and indicated a larger eutrophication in Lake QJP, which could be caused by the development of ecotourism in Lake HSH and the concomitant increase in aquaculture in Lake QJP in recent years. The highest abundance of C30 αβ-hopane (~ 10.24µgg-1 TOC) and the lowest CPIH values in Lake QJP revealed a possible petroleum pollution since 2008. Taken together, lake eutrophication in the Songnen Plain accelerated after 1950 and was influenced primarily by agriculture and aquaculture. This is in contrast to lakes in other regions of China (such as the Yangtze River Basin and Yunnan Province), where urbanization and industrialization have exerted a dominant influence on the lake environment.

Stepwise deforestation during the Permian-Triassic boundary crisis linked to rising temperatures

Although the trajectory of the marine mass extinction at the ∼252-Ma Permian-Triassic (P-Tr) boundary has been well studied, details of the coeval collapse of terrestrial ecosystems remain murky. Here, we use hydrocarbon biomarker compositions and other geological records (i.e., organic carbon isotopes (δ13Corg), charcoal abundance, and Hg content) from a tropical peatland succession in southwestern China to reconstruct in detail the history of terrestrial ecosystem collapse during the P-Tr crisis. Our high-resolution hydrocarbon biomarker records reveal that this collapse proceeded in a stepwise manner with increasing intensity as the crisis unfolded. We recognize three discrete crisis stages: Stage I within the uppermost Xuanwei Formation and Stages II and III within the lowermost Kayitou Formation. Stage I, the early crisis stage, is marked by a significant decline in terrestrial biomass (continuing into the later stages), as recorded by reduced C29 steranes relative to total steranes and a concomitant reduction in the ratio of pristane to phytane (Pr/Ph). Stage II, the main crisis stage, records intensified soil erosion and sediment flux as revealed by rising dibenzofuran (DBF) content and high hopane/sterane ratios, the disappearance of coal seams, a sharp negative shift in δ13Corg, and peak concentrations of charcoal reflecting increased wildfire incidence. Stage III, the late crisis stage characterized by enhanced soil erosion, corresponds to peak values of Hg and Hg/TOC but no charcoal peak, suggesting intensified volcanism and a return to a humid climate. These stages closely follow temperature records, which show a stepwise rise during the crisis interval, implying that the deforestation process was strongly influenced by punctuated rises in temperature and/or its attendant effects (e.g., climate aridification). This P-Tr transition scenario suggests that global warming can trigger deforestation and reduce terrestrial carbon storage, thus serving as a positive climate feedback, with important implications for present-day climate change.