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Most oil source correlation indicators are invalid because of the high maturity of the deep marine strata. Thus, a suitable indicator with high thermal stability requires to be established. In this study, to understand the effect of thermal maturation on the carbon isotopic composition of unsubstituted aromatics, we performed a number of anhydrous thermal simulation experiments involving two typical Chinese shales (lacustrine and marine shales), their corresponding expelled oils, three crude oils, and their associated oil fractions, that is, saturates, aromatics, resins, and asphaltenes (SARA). The generated unsubstituted aromatics were examined in terms of molecular distributions and carbon isotopic composition. The results show that unsubstituted aromatics in different types of samples demonstrated similar variation characteristics. Phenanthrene can be formed continuously in 0.45%/0.55-2.30%

Petroleum contamination surrounding oilfields has attracted more concerns. However, the levels, distribution and source of petroleum of Changqing Oilfield soil still remain lots of knowns, which is important for local environmental protection. Given soil contamination issues in Changqiong Oilfield were investigated. The maximum concentrations of total petroleum hydrocarbons (TPHs), N-alkanes (TNAs) and polycyclic aromatic hydrocarbons (PAHs) were determined to be 1960.29, 96.13 and 0.82 mg/kg, respectively. TPHs were higher in the north than the south of the study area. TPHs decreased in the horizontal and vertical distribution as soil depth and distance from oil wells increased. Source analysis showed that TNAs mainly originated from petroleum, PAHs were controlled by petroleum spills, combustion and traffic. Correlation analysis implied that TPHs residues had an effect on soil environmental quality. This study have important implications for understanding the environmental behavior of petroleum and can provide support for petroleum remediation and risk control.

Investigate the effect of soil organic matter (SOM) and low molecular weight organic acids (LMWOAs) on minerals adsorption of PAHs. Batch adsorption experiments have been carried out to study the adsorption of PAHs (Naphthalene (NaP), Phenanthrene (Phe) and Pyrene (Pyr)) by minerals (Montmorillonite (Mnt), kaolinite (Kln) and calcite (Cal)). This research found that compared with Kln and Cal, Mnt showed the maximum adsorption capability for PAHs. And the order of PAHs adsorption by Mnt was: Pyr Phe Nap, which corresponds to the octanol-water partition coefficient (K

The distribution, composition, sources, and potential ecological risks of polycyclic aromatic hydrocarbons (PAHs) in the sediments of the Lanzhou Reach of the Yellow River, China were investigated. The total concentration of the 18 individual PAHs (∑18PAHs) in the sediments ranged from 638 to 1620 ng/g, with a mean value of 901 ng/g. The pollution level of PAHs in the sediments was low to moderate. Spatially, the distribution of PAHs in the sediments showed an increasing trend along the direction of water flow. ∑18PAHs predominantly consisted of low molecular weight PAHs. The principal component analysis and isomer ratios of PAHs suggested the mixed sources of petroleum and those from the combustion of petroleum, coal, and biomass. The results showed that the PAHs in the sediments of the Lanzhou Reach of the Yellow River have a low ecological risk. However, the BaP equivalent exposure values suggested a potential cancer risk.

This work presents a dataset which provides information on the influence of aromatic nuclei on the carbon isotope of gases. Gases analyzed herein were obtained by pyrolysis of model compounds and kerogens. The carbon isotope of gases from paraffin cracking with and without the addition of aromatic nuclei is summarized. We also obtained carbon isotope data for the gases from different type of kerogens, which indicate the role of aromatic nuclei in the formation of natural gases from kerogen cracking. Further interpretation and discussion of these data can be found in the related research article entitled “The methylation of aromatic nuclei — I: Implications for the geochemical evolution of gas” [1]. Keywords: Aromatic nuclei, Carbon isotope, Natural gas, Pyrolysis experiment

The abundant acyclic isoprene alkanes, including norpristane (2, 6, 10-tetramethyltetradecane), pristane (2, 6, 10, 14-tetramethylpentadecane), phytane (2, 6, 10, 14-tetramethylhexadecane) and thei...

The presence of antibiotic in aquatic environments has become a topic of great concern with respect to both environment and global public health. However, to date, only a few studies have been carried out on the sorption behavior of antibiotics in aquatic environments. In this study, batch equilibrium experiments were conducted to explore the sorption/desorption behavior of Chlortetracycline (CTC) on the sediments in the Lanzhou section of the Yellow River. The results showed multilayer chemisorption on heterogeneous surfaces dominated by hydrophobic distribution and an obvious hysteresis phenomenon was observed. In addition, the sorption was found to be influenced by factors such as a continuous increase in the temperature, reduction in the initial concentration of CTC, and the increasing particle size of the sediments. The pH was found to affect the dissociation degree of CTC, and the sorptive amount was found to decrease with the increase in the pH value. The presence of other ions which with high valence state and concentration presenting an obvious inhibitory effect in the sorption process. Additionally, the large sorptive amount of antibiotics in the sediments due to the high Cation exchange capacity (CEC), organic matter, and clay particles indicated the influence of the physicochemical properties of sediments on the sorption behavior of antibiotics. This study preliminarily grasps the trend of CTC sorption/desorption on sediments, which is helpful in understanding the fate of CTC and assessing its ecological risks in the upper reaches of the Yellow River.

Adding livestock manure to soil to improve soil quality is a common agricultural practice. However, information on the effect of manure soil amendments on the sorption of veterinary antibiotics is scarce. Batch equilibrium experiments were utilized to investigate the effects of livestock manures on the sorption of chlortetracycline (CTC) onto sierozem. Kinetic sorption results showed that sorption equilibrium for CTC was reached within 2 h, and the presence of livestock manures lengthened the time to equilibrium attainment and promoted the sorption capacity of CTC onto sierozem. A good fit of the sorption kinetic data was achieved with a pseudo-second-order model with or without the presence of animal manure. Both boundary layer control and intraparticle diffusion were related to the sorption kinetic process. The CTC sorption isotherm of sierozem fit well with both Freundlich isothermal and linear models. The sorption of CTC onto sierozem exhibited strong pH dependence and was strongly governed by the ability of each substance to ionize as a function of pH. A decrease in CTC sorption was observed with increasing ionic strength as electrolyte cations competed with the positively charged CTC species and complexes for sorption sites. CTC sorption capacity declined when the solution contained Ca2+ compared to Na+ and Mg2+ solutions at similar ionic strength. The sorption of CTC by sierozem affected by livestock manures exhibited strong dependence on the amendment amount. The results suggest that manure application may change the sorption behavior and mechanism of CTC on loess soil. These findings contribute to understanding the fate and risk of veterinary antibiotics in loess soil affected by manure application.

Dibenzopyrene and its isomers are considered the most potent carcinogens of all polycyclic aromatic hydrocarbons tested to date. However, despite public concerns over their deleterious effects, they have not been extensively studied. The occurrence of four highly carcinogenic isomers of dibenzopyrene – dibenzo[def,p]chrysene, dibenzo[a,e]pyrene, dibenzo[a,i]pyrene, and dibenzo[a,h]pyrene in urban soil samples from Shanghai, China, have been determined in this study, as well as that of benzo[a]pyrene and coronene. A total of 14 peaks with ions at m/z 302 were detected by gas chromatography-mass spectrometry. Although the concentrations of benzo[a]pyrene and the sum of the 16 priority polycyclic aromatic hydrocarbons were greater than that of dibenzopyrene and its isomers, the carcinogenic potency of the latter was higher than that of benzo[a]pyrene. The results also indicate that the relative carcinogenic potency of the four dibenzopyrene isomers in the samples is higher than that of the 16 priorit...

A novel, effective and easy-to-operate method to enrich unsubstituted naphthalene and phenanthrene directly from crude oils was developed based on closed-system pyrolysis. The pyrolysis at 500 °C for 12 h was found to be sufficient for the enrichment of unsubstituted aromatics that were free of unresolved complex mixture (UCM) and poly-substituted aromatics. This allowed further accurate compound specific isotope analysis, and GC-IRMS data showed that the δ13C values of unsubstituted naphthalene and phenanthrene had no obvious fractionation during the enrichment process. This method provides an easy-to-operate pre-concentration technique for unsubstituted aromatics suitable for compound-specific isotope analysis (CSIA), laying the foundation for developing new oil–oil correlation indicators.

Surface soils from the tourist areas of the northwest Qinling Mountains were analyzed to determine the concentrations, probable sources and potential risks of hydrocarbons. Concentrations of aliphatic and aromatic hydrocarbons ranged from 4.18 to 3240 ng g−1 and 0.0462 to 101 ng g−1 dry weight, respectively. The extent of soil contamination by hydrocarbons was generally typified by unpolluted to slightly polluted levels. The incremental lifetime cancer risks (ILCRs) for exposure to soil-borne PAHs indicated complete safety for tourists. Early diagenesis of natural products, bacteria activities and petroleum were the three main sources of aliphatic hydrocarbons, while the transport of air pollutants from pyrolytic processes was the main origin of PAHs. Because the photochemical reaction of PAHs in the atmosphere would produce lower ratios for Ant/(Ant + Phe), BaA/(BaA + Chr) and IcdP/(IcdP + BghiP), but a higher ratio for Fla/(Fla + Pyr), the source classification highly depended on the diagnostic ...

Anhydrous closed-system pyrolysis experiments were conducted on the pure alkyl naphthalenes, n-alkanes and three crude oils at the highly to over mature stage in order to investigate compositional and isotopic changes of individual aromatic hydrocarbons during laboratory maturation. On the whole, aromatic hydrocarbons have better thermal stability than n-alkanes. While the carbon isotopic composition of substituted aromatic hydrocarbons exhibits a positive correlation with increasing thermal maturity, there is no significant fractionation in the carbon isotopic composition of unsubstituted aromatic hydrocarbons. This finding suggests that the carbon isotopic distribution of unsubstituted aromatic hydrocarbons can be used as an effective tool for oil-oil and oil-source correlation, especially for highly-over mature fields.

The European Union has set targets to reduce greenhouse gas emissions in total energy consumption, ensure the development and use of clean energy sources, and strive to reduce carbon emissions by 90% from 1990 levels by 2050. This study attempts to assess the environmental impact of electricity production on electricity demand and associated emissions in Italy through a three-step process. First, a literature review was conducted to estimate the growth of electricity demand in Italy by population and industry in 2014. Secondly, the CO2 and SO2 produced in the process of power generation by different power production methods were evaluated and compared. Finally, according to the current production and power models, the development trend of renewable energy in Italy in 2050 was estimated, and the satisfactory conclusion is that the renewable energy can fully meet the supply and demand in 2050 in Italy.

With the deepening of oil and gas exploration practice, the increasing degree of oil and gas exploration and the increasing demand for oil and gas, the target of oil and gas exploration is gradually transformed into deep and ultra-deep areas. Meanwhile, the genesis of deep and ultra-deep reservoirs has gradually become the focus of research by domestic and foreign scholars. Oil/gas source correlation is an important means to study the genetic relationship between oil and gas and source rocks. Based on the geological and geochemical data, this paper summarizes and analyzes the advantages and disadvantages of the current methods of deep and ultra-deep oil/gas source correlation, and puts forward the existing problems and future development direction of deep and ultra-deep oil/gas source correlation.

This study investigated the content, distribution, and contamination levels of toxic metals (Cd, Cr, Cu, Pb, and Zn) in street dust in Lanzhou, an industrial city in Northwest China. Meanwhile, the risk these metals posed to the urban ecosystem and human health was also evaluated using the potential ecological risk index and human exposure model. Results showed that concentrations of these metals in the dust are higher than the background value of local soil, with Cu having the highest levels. The districts of Anning and Xigu had the most extreme levels of contamination, while Chengguan and Qilihe districts were lightly contaminated, which can be partly attributed to human activities and traffic densities. In comparison with the concentrations of selected metals in other cities, the concentrations of heavy metals in Lanzhou were generally at moderate or low levels. Heavy metal concentration increased with decreasing dust particle size. The pollution indices of Cr, Cd, Cu, Pb, and Zn were in the range of 0.289–2.09, 0.332–2.15, 1.38–6.21, 0.358–2.59, and 0.560–1.83 with a mean of 1.37, 1.49, 3.18, 1.48, and 0.897, respectively. The geo-accumulation index (I geo) suggested that Zn in street dust was of geologic origin, while Cd, Cr, Pb, and Cu were significantly impacted by anthropogenic sources. The comprehensive pollution index showed that urban dust poses a high potential ecological risk in Lanzhou. Non-carcinogenic and carcinogenic effects due to exposure to urban street dust were assessed for both children and adults. For non-carcinogenic effects, ingestion appeared to be the main route of exposure to dust particles and thus posed a higher health risk to both children and adults for all metals, followed by dermal contact. Hazard index values for all studied metals were lower than the safe level of 1, and Cr exhibited the highest risk value (0.249) for children, suggesting that the overall risk from exposure to multiple metals in dust is low. The carcinogenic risk for Cd and Cr was all below the acceptable level (

Aromatic hydrocarbons are an important component in crude oil and sediments. Furthermore, the structure of macromolecular organic matter (such as kerogen) is also based on aromatic nuclei. The earlier methylation and later demethylation of various aromatic nuclei would affect the chemical components and carbon isotopes of aromatics as well as saturated hydrocarbons and gaseous hydrocarbons. The scope of the present study was to investigate the role of aromatic nuclei in the formation and geochemical evolution of natural gas in complex geological systems. The use of model compounds could simplify the complex system, and n-tricosane (n-C23), n-tetracosane (n-C24), and naphthalene (N) were selected as model compounds for paraffins and aromatic hydrocarbons and subjected to pyrolysis experiments. The results showed that aromatic nuclei had a slight influence on the gas generation without using a catalyst. However, the gaseous components were substantially affected by aromatic nuclei under the catalysis of clay, when the temperature was lower than 400 °C. The ratios of isoparaffin to n-alkane of gaseous hydrocarbons were reduced by the aromatic nuclei. As carbon isotopically lighter methyls preferred to combine with the aromatic nuclei, the gas productions were reduced, and there was a 13C depletion of methane with increasing temperature, which is contrary to the case of paraffin cracking alone. This trend can also be observed in the pyrolysis gases formed from the type II and III kerogens. The macromolecular aromatic nuclei played a similar role with the small aromatic hydrocarbons. These effects would mainly occur in the mature to highly mature stage of the organic matter (the paleo-geothermal temperature is ≤ 150 °C). The above explorative experiments suggested that a large number of aromatic nuclei and their methylation reactions could exert a significant influence on the distributions and the carbon isotopic compositions of gaseous hydrocarbons in the evolution of sedimentary organic matter. This research also provided a new explanation for the carbon isotopic abnormality (the 13C-depleted methane and the increasing δ13C2-δ13C1 values) of deep natural gas of the Tarim Basin, in northwest China.

Biodegraded crude oils in China are distributed widely and make up a certain portion of heavy-oil resources. An unresolved complex mixture (UCM) of hydrocarbons was isolated from three biodegraded crude oils in the Gudao reservoir of the Shengli Oilfield, China. The biomarker composition of biodegraded oils was determined using GC–MS technique. The results show that n-alkanes were completely depleted, isoprenoids and diasteranes were almost absent. The hydrocarbons expect for tricyclic terpane, steranes, hopane, were preferentially depleted in saturated fraction. Meanwhile, the 25-norhopane series occurs, indicating that the crude oils experienced severe degradation equivalent to levels 5–6. Based on biomarker proxies, the depositional environment of the Gudao Oils can be divided into two phases. In the first (GD2-19-55 and GD8-27N12), deposition occurred completely in seawater-dominated oxic to suboxic conditions, with primary input of terrestrial higher plants with an abundant influx of aquatic organisms. The second phase (GD2-7-41, GD-KD-162, GD-KD-18-168 and GD-KD-45) consisted of mainly seawater anoxic to suboxic/oxic conditions along with a small freshwater influence, with diluted organic matte derived from phytoplankton and a lesser influence from terrestrial higher plants. In addition, the vitrinite reflectance (Ro) of ca. 0.73–0.89% and methylphenanthrene index (MPI-1) of ca. 0.55–0.82 indicate the organic matter to be mature.

International audience; Coal samples analyzed from Junggar Basin are characterized by high Total Organic Carbon (TOC) contents (63.7-82.2%) in all samples, except the highly over-mature samples Ha-01 and Ha-02, and high S2 (60.5-83.0 mg HC/g rock) and Hydrogen Index (HI) values (77-118 mg HC/g TOC), indicating the coal rocks have excellent source rock potential. The Tmax values (418-531°C), C29 sterane 20S/(20S+20R) ratios (0.20-0.54) and C31 homohopane 22S/(22S+22R) ratios (0.26-0.61) indicate an immature to highly over-mature stage of organic matter, which is supported by the organic geochemical maturation parameters. In addition, n-alkane carbon numbers range from C11 to C33 with maxima at n-C19 or n-C23, exhibiting unimodal distribution patterns except Ai-13 and Ha-01, and low Pr/Ph ratios (0.29-0.80) in Ai-01, Ai-13, Ha-01 and Ha-02, indicating a suboxic reductive environment. In Wu-8, Wei-09 and Shinan-20, the Pr/Ph ratios are clearly greater than 1.0 (2.43-3.23), indicating oxic depositional conditions.Furthermore, pristane isomers were identified in extracts from these coal samples. Using coals of different maturity, which correspond to vitrinite reflectances (%Ro) of 0.36-2.99%, the Pristane Isomerization Ratio (PIR) (PIR = [6(R)10(R)+6(S)10(S)]/6(R)10(S)) ranges from 0.42 to 0.97 for the coal extracts. The value of the PIR, which is a molecular maturity parameter, is evaluated by analyzing a series of samples using known values of the molecular maturity parameter based on the sterane and hopane isomerization indices, and the Methyl Phenanthrene Index (MPI). Changes to the PIR in highly mature Ai-13 (Ro > 1.5%) and over-mature Ha-01 and Ha-02 (Ro > 2.0%) are clear; thus, a linear correlation is evident between the PIR and Ro. The results suggest that the PIR is an appropriate indicator of maturity for the highly mature and over-mature coal samples in the Junggar Basin.

In this study, n-alkanes, isoprenoids and n-alkyl-ketones were detected in lacustrine sediments in the Maogou section of the Linxia Basin, NE Tibetan Plateau, NW China. The distribution characteristics of these compounds correspond to arid climate change in inland Asia from the upper Oligocene to the Pliocene. The characteristic bimodal distribution of n-alkanes, which was observed in the investigated samples, is centered on n-C17–n-C20 and has maximum values at n-C18 in all samples; n-C27–n-C31 has maximum values at n-C29 in some of the samples. The front mode shows a weak even carbon number predominance of short-chain n-alkanes (CPI17–21 0.55–0.89); in contrast, the back mode has a strong odd carbon number predominance of long-chain n-alkanes (CPI25–31 1.41–2.42). Changes in the nC27/nC31 ratio (woody plants/grassy plants) along the entire section corresponded to three climate stages: an arid to humid climate stage from ~ 22.5 to 18.4 Ma; 6.25 to 5.5 Ma; and two major humid stages at ~ 18.4 Ma and ~ 5.5 Ma. A warm-humid climate was identified for the ~ 10 Ma to ~ 9 Ma period, which turned to an arid-cold climate from ~ 8 Ma to ~ 7.5 Ma, by assessing changes in the (n-C17–n-C21)/(n-C27–n-C31) ratios. Warm-humid conditions gradually increased from ~ 7.5 Ma to ~ 5.5 Ma, as has been confirmed by multiple geochemical climate indicators. A distinctive climate change toward arid-cold conditions at ~ 8 Ma corresponded to a striking increase in the high-carbon-numbered n-alkanes and a rapid decrease in the (n-C17–n-C21)/(n-C27–n-C31) and n-C27/n-C31 ratios of n-alkanes, which suggests a large input of higher plants. Our observation from the biomarker analysis is in agreement with previous reports that used palynofloras to determine that climate change in the investigated region responded to the uplift of the Tibetan Plateau at ~ 8 Ma.

This study reports the first observation of predominant even C-numbered n-alkanes from sediments in the continuous lacustrine-sedimentary section (Maogou) from the Late Miocene to the Early Pliocene (13–4.4 Ma) in the Linxia Basin, NE Tibetan Plateau. The n-alkanes showed a bimodal distribution that is characterised by a centre at n-C16–n-C20 with maximum values at n-C18 and n-C27–n-C31 as well as at n-C29. The first mode shows a strong even C-number predominance (OEP16–20 0.34–0.66). In contrast, the second mode has a strong odd C-number predominance (OEP27–31 1.20–2.45). Certain types of special autochthonous bacteria are a possible source for this distribution of even C-numbered n-alkanes in lacustrine sediments. These bacteria may have a high production rate in weak oxic–anoxic and arid depositional environments, in which a variety of geochemical parameters have recorded palaeoclimate change.

The level, distribution, compositional pattern and possible sources of polycyclic aromatic hydrocarbons (PAHs) in Lanzhou urban soil of Northwest China were investigated in this study. The total level of 22 PAHs ranged from 115 to 12,100 µg kg(-1) and that of 16 priority PAHs from 82.4 to 10,900 µg kg(-1). Seven carcinogenic PAHs generally accounted for 6.18-57.4% of total 22 PAHs. Compared with data from those reported about urban areas, PAH contamination in Lanzhou urban soils was moderate. Among different functional areas, higher level of PAHs was found along roadsides and in the industrial district (p

Marked fish placed above a smolt trap allow fisheries biologists to estimate the efficiency of the trap and hence to estimate the number of smolts migrating past the trap. We compared stratified maximum likelihood estimators and confidence intervals of total numbers of fish migrating to two other well-known estimators and associated confidence intervals using simulation. The Bailey adjusted Lincoln-Petersen estimator and its bootstrap confidence interval performed well overall.

The status, source and health risk of street-dust-borne polycyclic aromatic hydrocarbons (PAHs) in Lanzhou of Northwest China were investigated. The total level of the 21 PAHs ranged from 1470 to 13,700 µg kg(-1) and that of the 16 priority PAHs from 1240 to 10,700 µg kg(-1). Higher levels of PAHs were mainly distributed in the Chengguan and Qilihe districts at Lanzhou central areas, and the lower levels were in Anning and Xigu districts. The level of seven potential carcinogenic PAHs generally accounted for 35-40 percent of total PAHs, and the PAHs contained two to four rings, mainly phenanthrene, benzo[b]fluoranthene and fluoranthene. The total level of PAHs increased with the decreasing particle size in the street dust. The correlation analysis suggested that the total organic carbon (TOC) was only slightly affected the PAH accumulation in street dust. The isomer ratios and principal component analysis indicated that the dust-borne PAHs in the dust were derived primarily from the combustion of biomass, coal and petroleum emission. The toxic equivalent concentrations (BaP(eq)) of dust-borne PAHs ranged from 115 to 827 µg BaP(eq) kg(-1), with a mean of 300 µg BaP(eq) kg(-1). The 95 percent upper confidence limit of Incremental Lifetime Cancer Risk due to human exposure to urban surface dust-borne PAHs in Lanzhou urban area was 2.031 × 10(-6) for children and 1.935 × 10(-6) for adults.