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Kerogen can release both liquid and gaseous hydrocarbons during thermal maturation. In this study, the maturation and hydrocarbon generation of a low-maturity type II kerogen were simulated via tem...

This study demonstrates a new system for the degradation of emerging pharmaceutical contaminants (e.g., ibuprofen) in water by coupling the naturally occurring ilmenite with hydroxylamine (HA) and persulfate (PS). Ilmenite was able to activate persulfate to generate sulfate radicals (SO4−·) and hydroxyl radicals (HO·). The radical generation was greatly improved by adding small amount of hydroxylamine into the solution, due to the efficient Fe(III)/Fe(II) cycle on the ilmenite surface promoted by HA, which was confirmed by X-ray photoelectron spectroscopy and electron paramagnetic resonance (EPR) spectroscopy analysis. SO4−· and HO· contributed comparably to ibuprofen degradation, which was verified by the radical scavenging tests. The degradation was enhanced with increasing ilmenite, PS and HA dosages, but the HA exhibited strong scavenging effect at its high concentrations. The ilmenite/PS/HA process worked well in the real treated wastewater, because the surface-controlled radical generation was less affected by the water matrix. However, the formation of bromate in the bromide-containing water by this process should be concerned. Ibuprofen was partially mineralized, and the degradation products were identified by ESI-tqMS. A radical-induced degradation pathway was proposed based on the product identification. This work provides the mechanistic insights on persulfate activation based on the surface-controlled catalytic processes. It also offers a new strategy to degrade emerging contaminants in water and sheds light on the environmental functions of natural minerals.

The oxygen vacancy in MnO2 is normally proved as the reactive site for the catalytic ozonation, and acquiring a highly reactive crystal facet with abundant oxygen vacancy by facet engineering is advisable for boosting the catalytic activity. In this study, three facet-engineered α-MnO2 was prepared and successfully utilized for catalytic ozonation toward an odorous CH3SH. The as-synthesized 310-MnO2 exhibited superior activity in catalytic ozonation of CH3SH than that of 110-MnO2 and 100-MnO2, which could achieve 100% removal efficiency for 70 ppm of CH3SH within 20 min. The results of XPS, Raman, H2-TPR, and DFT calculation all prove that the (310) facets possess a higher surface energy than other facets can feature the construction of oxygen vacancies, thus facilitating the adsorption and activate O3 into intermediate peroxide species (O2-/O22-) and reactive oxygen species (•O2-/1O2) for eliminating adjacent CH3SH. In situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) revealed that the CH3SH molecular was chemisorbed on S atom to form CH3S-, which was further converted into intermediate CH3SO3- and finally oxidized into SO42- and CO32-/CO2 during the process. Attributed to the deep oxidation of CH3SH on 310-MnO2 via efficient cycling of active oxygen vacancies, the lifetime of 310-MnO2 can be extended to 2.5 h with limited loss of activity, while 110-MnO2 and 100-MnO2 were inactivated within 1 h. This study deepens the comprehension of facet-engineering in MnO2 and presents an efficient and portable catalyst to control odorous pollution.

To evaluate petroleum generation and expulsion processes, pyrolysis experiments that simulate increased overburden pressures were conducted on an immature organic-rich shale with type-II kerogen. Expelled oils and residual rocks with different maturities covering the oil window were recovered from the experiments. The residual rocks were then subjected to stepwise extraction in conjunction with stepwise dissolution of the carbonate and silicate minerals to obtain free and bound bitumen fractions. The compositions of acidic and neutral compounds in both expelled oils and bitumen fractions were investigated by negative-ion electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Neutral nitrogen compounds were found to only exist in expelled oil and free bitumen, while acidic compounds (typically contain carboxylic functional group(s)) were prevalent in bound bitumen. Oxygen-containing functional groups with high polarity in oxygen-containing compounds and oxygenated nitrogen/sulfur compounds are proposed to be the dominant bonding forces that facilitate the interaction between bitumen and mineral matrix or kerogen. Semiquantitative results of acidic compounds reveal that the distributions of acidic compounds in both free and bound bitumens vary throughout the oil window stage, especially for those in the bound phase after an intense oil expulsion from the shale at Easy%Ro > 0.9. During maturation, acidic compounds in free and bound bitumens gradually decreased in their abundances. However, oil expulsion from the shale brought about a significant redistribution of acidic compounds among expelled oil, free and bound bitumens. These results indicate that polar components in shales are closely related to thermal maturation of organic matter and oil expulsion from the shales in a petroleum system.

[Image: see text] Petroleum generation–expulsion thermal simulation experiments on a low-maturity type I source rock were carried out. The composition of hydrocarbons and heteroatom-containing compounds in both expelled and residual oils was characterized by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry and gas chromatography-mass spectrometry. A thorough analysis of fractionation effects was presented between expelled and residual oils. The oil composition strongly depended on the pyrolysis temperature. A significant difference in the molecular composition was found between expelled and residual oils at various pyrolysis temperatures. The difference in maturity for expelled and residual oils could be revealed clearly by the difference in the molecular composition of heteroatom-containing compounds. Carboxylic acids in the residual oil cracked quickly with the pyrolysis temperature above 350 °C (% Ro = 1.0) but part of them would survive if they were expelled out of the source rock timely. The variations between the relative abundance of oxygen compounds and nitrogen compounds indicated that the thermostability of oxygen-containing nitrogen compounds was lower than that of neutral nitrogen compounds. The variation trends in double bond equivalents and carbon number distributions of O(1), O(2), and N(1) class species were similar. The aromaticity of heteroatom-containing polar species increased with maturity.

Summary In this study, two liquid hydrocarbon collection methods were used to collect light hydrocarbons generated from the cracking of crude oil in closed system, and the characteristics of the products collected were compared. Relative to the liquid nitrogen direct freezing collection (LNDF) method, the traditional liquid hydrocarbon collection (TLH) method can cause the yield loss of 10%-75% of light hydrocarbons, especially low carbon number light hydrocarbons (such as nC6, nC7, benzene, toluene, and 3-methylhexane). Because the TLH method can lead to various degrees of loss for different compounds in light hydrocarbons, it can also lead to the deviation of some light hydrocarbon parameters representing oil-oil correlation, indicating the maturity of crude oil and reflecting secondary alteration of crude oil. In addition, the δ13C values of nC6, nC7, benzene, toluene and 3-methylhexane collected by TLH method are heavier. These compounds with heavier δ13C values are the ones that have suffered the most yield loss in the TLH method. Therefore, the LNDF method can more accurately reflect the yield, parameters and carbon isotopes of light hydrocarbons in closed system pyrolysis.

Rational design of sustainable, cost-efficient and highly efficient deionization electrodes is crucial for the practical applications of capacitive deionization (CDI). Mycelial pellet-derived nitrogen and sulfur heteroatom co-doped three-dimensional (3D) carbon nanosheets (NSHPC) with a hierarchical porous structure have been facilely fabricated via a simple one-step strategy by utilizing sustainable mycelial pellets as a carbon source, glutaraldehyde as a crosslinking agent, zinc chloride as a pore forming agent, and thiourea as a heteroatom supplier. The obtained biomass-derived NSHPC nanosheets, with interconnected hierarchical macro-meso-micropores and a lamellar structure, exhibit outstanding CDI performance with an electrosorption capacity of 18.71 mg g−1 in 500 mg L−1 NaCl solution and a high reversibility (stable up to 10 cycles). The performance of NSHPC significantly surpasses that of the bulk mycelial pellet-derived carbon without activation and modification. The efficient CDI performance of NSHPC can be attributed to its unique features, including the 3D network structure formed by bundled nanosheets to provide multi-dimensional ion diffusion pathways and interlayer ion storage, the hierarchical pores to assist efficient ion diffusion and capture, the surface functional groups derived from mycelial pellets, and the hydrophilicity contributed by the heteroatom co-doping. The design of NSHPC nanosheets paves an avenue for developing efficient sustainable materials for CDI applications.

A novel process for S-VOCs degradation using wet scrubbing coupled with catalytic ozonation was developed for first time. We report redox-robust catalysts consisting of Ag(0)/Ag(I) species decorated rambutan-like MnO2 hollow microspheres (Ag/R-MnO2) with strong metal-metal oxide interaction (MMOI) exhibited superior catalytic ozonation performance for CH3SH elimination. The optimum Ag/R-MnO2 reached a significant improvement in CH3SH elimination of 96.9% conversion over pristine R-MnO2 under GHSV of 75,000 mL h−1 g−1, and O3 utilization rate of 92.3%. An outstanding stability of Ag/R-MnO2 under wet catalytic ozonation process was demonstrated, which outperformed that in gaseous system. CH3SH was captured by aqueous solution and preferentially chemisorbed on Ag, then deeply oxidized to the final products of SO42-/CO32- via catalytic ozonation by multivalent R-MnO2. The excellent performance can be ascribed to efficient electron replenishing interaction between Ag(0)/Ag(I) and multivalent R-MnO2, efficient O3 activation through oxygen vacancies-rich R-MnO2, and enhanced mass diffusion in wet scrubbing process.

Identification and quantification of mixed sources of petroleum reservoirs as well as the sources of oil spills generally requires the molecular composition information about the mixture. In this study, the relative concentrations of a series of polar acidic compounds, semiquantified by negative ion ESI FT-ICR MS, were calculated using alternating least-squares (ALS) to unmix a group of oil mixtures prepared in the laboratory using three endmember oils. It was shown that the ALS results were accurate based on the relative concentrations of polar acidic compounds, regardless of whether endmember oils and several samples were removed from the sample set. ALS was able to accurately calculate the composition of endmember oils, regardless of whether they were included in the sample set. This method is relatively simple, efficient, time-saving, and has potential for geological source identification of mixed oils or oil spills.

Achieving an understanding of the biodegradation of organic sulfur compound(s) (OSC) in crude oils has been hampered by limitations in separation methods and analytical techniques. In this study, a simulated aerobic biodegradation experiment was performed on a sulfur-rich crude oil, from which a series of biodegraded oils from slight to moderate degrees of biodegradation were obtained. Molecular transformations in these biodegraded oils were investigated by gas chromatography–mass spectrometry (GC–MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT–ICR MS) under both positive- and negative-ion electrospray ionization (ESI) modes. The variations in the distributions of saturated hydrocarbons, OSCs, and acidic components during aerobic biodegradation were studied. A gradual decrease of OSCs with alkyl chains during biodegradation, especially in those with few sulfur-containing or naphthenic/aromatic rings, was observed. In addition, sulfur-containing phenols with alkyl chains also exhibited a trend of gradual decrease similar to alkyl phenols, with fewer ring numbers being more susceptible to biodegradation. The biodegradation pathways for OSCs and sulfur-containing acids, as well as certain other heteroatomic compounds, are discussed. Terminal oxidation, rather than sulfur-specific degradation, is the more likely biodegradation pathway of these OSCs, as in the case of n-alkanes in this study. Sulfur-containing carboxylic acids may be the biodegradation products of these OSCs.

Organic sulfur compounds (OSCs) are abundant in immature crude oils, including “polar” OSCs that are defined here as compounds containing one or more heteroatom(s) in addition to sulfur atoms having sufficient polarity to be analyzable by electrospray ionization (ESI) without derivatization. An understanding of the origins of polar OSCs in crude oils has been hampered by limitations in their analytical characterization. In this paper, we employed a high field (9.4 T) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled with ESI to study the sulfur-rich immature crude oils from the Jianghan Basin in China. The results show that the polar OSCs usually have non-sulfur counterparts, i.e., heteroatom-containing compounds without sulfur, with similar carbon number ranges, but slightly lower DBE (double bond equivalence) distributions. The similar or even identical carbon number distributions of the polar OSCs and their non-sulfur counterparts indicate their inheritance from the same precursors. The sulfur rings in polar OSCs are formed by intramolecular sulfurization that leads to the increases in DBEs compared to their non-sulfur counterparts. The results also indicate that the number of sulfur rings that can be formed in polar OSCs is largely controlled by the number of available reactive functional groups in their precursors. This paper extends our knowledge of intramolecular sulfurization during early diagenesis, especially for polar heteroatom-containing compounds.

Per- and polyfluoroalkyl substances (PFASs) contamination in the Bohai Sea and its surrounding rivers has attracted considerable attention in recent years. However, few studies have been conducted regarding the distribution of PFASs in multiple environmental media and their distributions between the suspended particles and dissolved phases. In this study, surface water, surface sediment, and air samples were collected at the Bohai Sea to investigate the concentration and distribution of 39 targeted PFASs. Moreover, river water samples from 35 river estuaries were collected to estimate PFAS discharge fluxes to the Bohai Sea. The results showed that total ionic compound (Σi-PFASs) concentrations ranged from 19.3 to 967 ng/L (mean 125 ± 152 ng/L) in the water and 0.70–4.13 ng/g dw (1.78 ± 0.76 ng/g) in surface sediment of the Bohai Sea, respectively. In the estuaries, Σi-PFAS concentrations were ranged from 10.5 to 13500 ng/L (882 ± 2410 ng/L). In the air, ΣPFAS (Σi-PFASs + Σn-PFASs) concentrations ranged from 199 to 678 pg/m3 (462 ± 166 pg/m3). Perfluorooctanoic acid (PFOA) was the predominant compound in the seawater, sediment, and river water; in the air, 8:2 fluorotelomer alcohol was predominant. Xiaoqing River discharged the largest Σi-PFAS flux to the Bohai Sea, which was estimated as 12,100 kg/y. Some alternatives, i.e., 6:2 fluorotelomer sulfonate acid (6:2 FTSA), hexafluoropropylene oxide dimer acid (HFPO-DA), and chlorinated 6:2 polyfluorinated ether sulfonic acid (Cl-6:2 PFESA), showed higher levels than or comparable concentrations to those of the C8 legacy PFASs in some sampling sites. The particle-derived distribution coefficient in seawater was higher than that in the river water. Using high resolution mass spectrometry, 29 nontarget emerging PFASs were found in 3 river water and 3 seawater samples. Further studies should be conducted to clarify the sources and ecotoxicological effects of these emerging PFASs in the Bohai Sea area.

Water-soluble organic compounds (WSOC) and methanol-soluble organic compounds (MSOC) in smoke particles emitted from residential coal combustion were characterized by ultrahigh-resolution mass spectrometry. The results showed that the molecular compositions of WSOC and MSOC are different. S-containing compounds (CHOS and CHONS) are found to be the dominant components (65-87%) of the WSOC, whereas CHO and CHON compounds make a great contribution (79-96%) to the MSOC samples. It is worth noting that greater abundance of S-containing compounds was found in smoke produced from coal combustion compared to biomass burning and atmospheric samples. The molecular compositions of WSOC and MSOC also varied significantly depending on the maturity of the coal. The WSOC and MSOC derived from the combustion of low-maturity coal contained a higher proportion of oxidized functional groups but with a lower degree of aromaticity than the compounds derived from the combustion of high-maturity coal. Our findings suggest that organic molecules with a high modified aromaticity index, low O/C ratio, and low polarity showed stronger light absorption. This study also suggests that CHO and CHON compounds significantly contributed to the light absorption of WSOC and MSOC and that the contribution of CHON may be stronger.

Biodegradation greatly affects the physical properties and economic value of oil and gas reserves. Here, the composition of a suite of 27 samples of shale soluble organic matter from typical biodegraded shale profiles in the Upper Triassic Yanchang Formation, Ordos Basin, China, was analyzed using GC/MS/MS and ESI FT-ICR MS technology. The effects of slight to moderate biodegradation on the compositions of saturated hydrocarbons and polar nitrogen, sulfur, oxygen (NSO) compounds were assessed, revealing three key effects as biodegradation increases (1) Chloroform asphalt "A" (i.e. soluble organic matter). and saturated hydrocarbons gradually decrease, aromatic hydrocarbons gradually increase, non-hydrocarbons increase, and there is no regular change in asphaltene content. (2) The relative content of pristane (Pr) and phytane (Ph) to their corresponding n-alkanes increases gradually, indicating the n-alkanes decrease gradually. However, the resistance of the n-alkanes to biodegradation may be related to the carbon number and odd-even distribution. As the carbon number increases, the ability of n-alkanes to resist biodegradation increases, and even carbon number n-alkanes may be more resistant to biodegradation than odd carbon number n-alkanes. (3) No obvious changes in the relevant biodegradation indices of steranes and polar NSO compounds were observed in the entire profile. Hopane biodegradation indices were variable and sometimes contradictory with depth throughout the sediment profile. However, overall the data suggest the hopanes were not affected by biodegradation. Our results indicate that shale oil can also be biodegraded, and due to the tightness of shale reservoirs, slight to moderate biodegradation is common. Changes in shale oil content in the profile are the result of the primary migration and biodegradation together, with primary migration occurring mainly from the shale to the upper sandstone reservoirs. The above evidence shows that slight to moderate biodegradation has a relatively small impact on shale oil. However, in previous work we have shown that biodegradation has significant impacts on the shale gas content and its geochemical characteristics.

Atmospheric brown carbon (BrC) is an important constituent of light-absorbing organic aerosols with many unclear issues. Here, the light-absorption properties of BrC with different polarity characteristics at a regional site of Pearl River Delta Region during 2016–2017, influenced by sources and molecular compositions, were revealed using radiocarbon analysis and Fourier transform ion cyclotron resonance mass spectrometry. Humic-like substance (HULIS), middle polar (MP), and low polar (LP) carbon fractions constitute 46 ± 17%, 30 ± 7%, and 7 ± 3% of total absorption coefficient from bulk extracts, respectively. Our results show that the absorption proportions of HULIS and MP to the total BrC absorption are higher than their mass proportions to organic carbon mass, indicating that HULIS and MP are the main light-absorbing components in water-soluble and water-insoluble organic carbon fractions, respectively. With decreases in non-fossil HULIS, MP, and LP carbon fractions (66 ± 2%, 52 ± 2%, and 36 ± 3%, respectively), the abundances of unsaturated compounds and mass absorption efficiency at 365 nm of three fractions decreased synchronously. Increases in both non-fossil carbon and levoglucosan in winter imply that the enhanced light-absorption could be attributed to elevated levels of biomass burning organic aerosols (BBOA), which increases the number of light-absorbing nitrogen-containing compounds. Moreover, the major type of potential BrC in HULIS and MP carbon fractions are oxidized BBOA, but the potential BrC chromophores in LP are mainly associated with primary BBOA. This study reveals that biomass burning has adverse effects on radiative forcing and air quality, and probably indicates the significant influences of atmospheric oxidation reactions on the forms of chromophores.

Confined pyrolysis experiments (gold capsules), quantitative flash pyrolysis-gas chromatography (Py-GC) and Rock-Eval analysis were performed on ten coals from the Junggar Basin and seven coals from the Kuqa Depression, Tarim Basin, northwestern China. The maximum yields of liquid components in confined pyrolysis experimnets (MCPΣC8+), which reflect oil potentials, have close correlations with the yields of n-alkanes + n-alkenes (FPΣn-C7+) in flash Py-GC, but have poor correlations with Rock-Eval QI ((S1 + S2)/TOC) values. Thus, oil potentials of coals can be better predicted on the basis of FPΣn-C7+ yields from flash Py-GC analysis. Coals with FPΣn-C7+ yield >10.4 mg/g TOC can generate MCPΣC8+ yield >∼22.5 mg/g TOC or oil yield >∼40 mg/g TOC in confined pyrolysis or in natural systems and are effective oil source rocks. Although both Py-GC and Rock-Eval are open systems, the yields of total liquid components (FPΣC7+) obtained from flash Py-GC have poor correlations with, and are substantially lower than, Rock-Eval QI. In contrast, FPΣC7+ values have much better correlations with oil potentials (MCPΣC8+). Coals with higher oil potentials (MCPΣC8+) generate higher amounts of liquid components detected in flash Py-GC (FPΣC7+) than those with lower oil potentials but similar Rock-Eval QI. The correlations for parameters with gas to oil ratios (GOR) in confined pyrolysis are increasingly better in the sequence of Rock-Eval QI, H/C atomic ratios, MCPΣC8+, FPΣn-C7+ and FPΣn-C7+/ΣC7+ ratios. GOR of petroleum generated from coals within oil generative window can be reasonably predicted on the basis of FPΣn-C7+/ΣC7+ ratio from flash Py-GC analysis.

This study investigates the degradation of a refractory emerging contaminant (i.e., ibuprofen) by a newly developed piezoelectric catalytic persulfate (PS) activation process. BaTiO3 nanoparticles (NP) and nanowires (NW) were hydrothermally synthesized and used as the piezo-catalysts to activate PS under ultrasonic irradiation for radical generation and ibuprofen (IBP) degradation. IBP was efficiently degraded in the US/BTO NW/PS system with a pseudo first order rate constant of 0.0818 min-1, and the rate constant was faster than that in the US/BTO NP/PS (0.0492 min-1), US/BTO NW (0.0324 min-1) and US/PS (0.0057 min-1) systems. The outstanding performance of IBP degradation in the US/BTO NW/PS system was attributed to the continuous generation of ·SO4- and ·OH via PS activation by the piezo-catalysis induced electrons. ·SO4- and ·OH contributed 53% and 44% to the IBP degradation respectively. Meanwhile, ·O2-, 1O2 and H2O2 were in-situ formed and identified as key intermediates for the generation of SO4- and ·OH. The IBP was partially mineralized and transformed to other organic compounds. The degradation products were identified using the UPLC/ESI-tqMS and a degradation pathway was proposed, which involved a sequence of hydroxylation, decarboxylation/demethylation and ring-opening reactions with ·SO4- and ·OH. This study demonstrates a new energy-saving approach to activating PS for micropollutant abatement and also provides insights into the mechanisms of the PS activation by the piezoelectric catalysis.

Due to multi-stage tectonic movements, many oil reservoirs in typical superimposed basins of China have undergone more than one secondary alteration. Typically, these oil reservoirs experienced biodegradation at an early stage followed by thermal alteration at a later stage. The extent of each secondary alteration can be variable. Here, the succession of biodegradation and subsequent thermal alteration is called superimposed secondary alteration. This study aims not only to show the superimposed secondary alteration process in the reservoir by laboratory simulations, but also to show how varying extents of biodegradation influence the gas generation behavior of crude oils under thermal stress. Hydrocarbon gas generation potential is significantly reduced at the low to moderate biodegradation stage because of the selective removal of normal and branched alkanes. Hydrocarbon gases generated from the more severely biodegraded oils are drier, attributable to the decreasing yields of C2–C5 gases relative to methane. In the oil-generative window, the methane generated from more severely biodegraded oils is relatively enriched in 13C. Kinetic modeling suggests that moderately and severely biodegraded oils are thermally less stable than the non-biodegraded and slightly biodegraded oils. The bulk hydrocarbon gas yields from the non-biodegraded oil do not exceed those from the moderately biodegraded oils until EasyRo > 1.6%. For EasyRo of 1.6–2.5%, pyro-bitumen yields from heavily to severely biodegraded oils were about 2–4 times that of non-biodegraded oil. That is, the gas yields normalized to the weight of pyro-bitumen from heavily to severely biodegraded oil is only 25–50% of the gas yield of non-biodegraded oil. Therefore, hydrocarbon gas resource potential based on pyro-bitumen content must be very carefully considered in cases of superimposed secondary alteration.

A visible-light-driven photocatalytic fuel cell system integrating electro-Fenton process (EF-PFC), comprised of oxygen vacancies-rich rGO/BiO1−xI photoanode and biomass-derived N-doped carbon (BNC) cathode, was developed to eliminate organic pollutant and generate electricity synchronously. The structure and properties of rGO/BiO1−xI were characterized by means of XRD, SEM, TEM, solid-state EPR, FTIR, Raman, XPS, UV-vis DRS and PL spectra. The photoelectrochemical activity of rGO/BiO1−xI was characterized by Mott-Schottky plots, photocurrent responses and EIS. The experimental results indicated that the introduced oxygen vacancies and graphene modification not only promoted the light-harvesting ability but also greatly improved the generation and transfer rate of charge carriers. Most importanly, BNC, acted as cathode, could efficiently reduce oxygen to H2O2, thus leading to more ·OH production in the presence of Fe2+. Simultaneously, the photogenerated electron could efficiently accelerate Fe2+/Fe3+ redox cycling for continuous Fenton reaction and increasing electricity generation in synergistic EF-PFC system. Using formic acid as sacrificial fuel, approximately 68% removal efficiency was reached in rGO/BiO1−xI-BNC EF-PFC system under visible light irradiation for 240 min while the photocurrent density (Jsc) and the maximum power density (Pmax) were measured to be 133.18 μA cm−2 and 17.50 μW cm−2. Furthermore, the radicals trapping experiments, hydrogen peroxide quantitative studies and ESR tests clearly revealed the mechanism of enhanced performance in rGO/BiO1−xI-BNC EF-PFC system. Therefore, this engineered rGO/BiO1−xI-BNC EF-PFC system with the cooperation of Fe2+/Fe3+ redox is a promising means to eliminate organic pollutants and generate electricity synchronously.

There are abundant bitumens and oil seepages stored in vugs in a Lower-Triassic Daye formation (T1d) marlite in Ni’erguan village in the Southern Guizhou Depression. However, the source of those oil seepages has not been determined to date. Multiple suites of source rocks of different ages exist in the depression. Both the oil seepages and potential source rocks have undergone complicated secondary alterations, which have added to the difficulty of an oil-source correlation. For example, the main source rock, a Lower-Cambrian Niutitang Formation (Є1n) mudstone, is over mature, and other potential source rocks, both from the Permian and the Triassic, are still in the oil window. In addition, the T1d oil seepages underwent a large amount of biodegradation. To minimize the influence of biodegradation and thermal maturation, special methods were employed in this oil-source correlation study. These methods included catalytic hydropyrolysis, to release covalently bound biomarkers from the over mature kerogen of Є1n mudstone, sequential extraction, to obtain chloroform bitumen A and chloroform bitumen C from the T1d marlite, and anhydrous pyrolysis, to release pyrolysates from the kerogen of T1d marlite. Using the methods above, the biomarkers and n-alkanes released from the oil samples and source rocks were analysed by GC–MS and GC-C-IRMS. The oil-source correlation indicated that the T1d oil seepage primarily originated from the Є1n mudstone and was partially mixed with oil generated from the T1d marlite. Furthermore, the seepage also demonstrated that the above methods were effective for the complicated oil-source correlation in the Southern Guizhou Depression.

There is an on-going debate about whether asphaltenes can be anaerobically biodegraded in reservoir rocks due to their complex macromolecular structure. In this study, asphaltenes were precipitated from a sequence of bitumens at various degrees of biodegradation. The compositions of alkyl moieties within the asphaltene molecular structure were characterized by on-line flash pyrolysis–gas chromatography (Py–GC), on-line thermally assisted hydrolysis and methylation using tetramethylammonium hydroxide (THM–GC), and Py–GC combined with alkaline hydrolysis. The results indicate that alkyl moieties bonded to asphaltene macromolecules are dominated by linear structures with chain lengths up to C27, mainly bonded through C–C and ether (thioether) bonds but less so through ester and hydrogen bonds. Furthermore, most n-fatty acids and linear aliphatic alcohols bonded to asphaltene structure by ester and hydrogen bonds were altered at slight–moderate biodegradation stages, while linear alkyl moieties attached to the asphaltene core through C–C and ether (thioether) bonds were likely altered at heavy–severe biodegradation stages. This indicates that the linear alkyl moieties bonded to the asphaltene structure by hydrogen and ester bonds are more susceptible to biodegradation than those bonded to the asphaltene core through stronger covalent bonds such as C–C and ether (thioether) bonds. Furthermore, variations in the chemical compositions and molecular structure of asphaltenes during biodegradation may not only be attributed to the alteration of linear alkyl moieties, but also the replacement of linear alkyl moieties bonded to the asphaltene structure by hydrogen and ester bonds with other biodegradation products.

Catalytic hydropyrolysis (HyPy) was used to release covalently bound aromatic hydrocarbons from both mature and overmature Permian source rocks in the Sichuan Basin, China. The released covalently bound aromatic hydrocarbons were discussed and compared with their free counterparts obtained by Soxhlet extraction. Furthermore, a mature Permian Dalong kerogen was selected for artificial simulation experiments. The HyPy experiments of the above thermal altered kerogens were subsequently conducted. The results from the artificial simulation sequence were also discussed and compared with those from the natural maturity sequence. For both natural maturity sequence and artificial simulation sequence, the distributions of covalently bound methylphenanthrenes and methyldibenzothiophenes are quite similar at different maturity stages. Triaromatic and monoaromatic steroids which are the aromatization products of steroids were not detected in covalently bound aromatics of all samples. The above results indicate that the rearrangement of methyl group on aromatic nucleus and the aromatization of steroids within kerogen was retarded to some extent or even prohibited, due to the protection of macromolecular structure below a vitrinite reflectance of 2.4%. It implies that aromatic maturity-related biomarker parameters based on the rearrangement and aromatization reactions within kerogens are probably not appropriate for maturity assessment. Meanwhile, perylene which is easily altered by thermal alteration was still existent in covalently bound aromatics released from the Dalong Formation even at over mature stage (Ro: 1.8%) and from the thermal altered kerogen until the temperature below of 400 °C (H/C: 0.49). It means the covalently bound perylene can be protected by macromolecular structure from the destruction of thermal stress at least below Ro of 1.8% (or H/C > 0.5). The results obtained also permitted the geochemical characterization of the source rocks.

Humic-like substances (HULIS) are a class of high molecular weight, light-absorbing compounds that are highly related to brown carbon (BrC). In this study, the sources and compositions of HULIS isolated from fine particles collected in Beijing, China during the 2014 Asia-Pacific Economic Cooperation (APEC) summit were characterized based on carbon isotope (13C and 14C) and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses, respectively. HULIS were the main light-absorbing components of water-soluble organic carbon (WSOC), accounting for 80.2 ± 6.1% of the WSOC absorption capacity at 365 nm. The carbon isotope data showed that HULIS had a lower non-fossil contribution (53 ± 4%) and were less enriched with 13C (−24.2 ± 0.6‰) relative to non-HULIS (62 ± 8% and −20.8 ± 0.3‰, respectively). The higher relative intensity fraction of sulfur-containing compounds in HULIS before and after APEC was attributed to higher sulfur dioxide levels emitted from fossil fuel combustion, whereas the higher fraction of nitrogen-containing compounds during APEC may have been due to the relatively greater contribution of non-fossil compounds or the influence of nitrate radical chemistry. The results of investigating the relationships among the sources, elemental compositions, and optical properties of HULIS demonstrated that the light absorption of HULIS appeared to increase with increasing unsaturation degree, but decrease with increasing oxidation level. The unsaturation of HULIS was affected by both sources and aging level.

Flash pyrolysis (Py) in combination with gas chromatography (GC) and mass spectrometry are often used to elucidate the structure of geomacromolecules such as kerogens, coals, asphaltenes and humic acids by analyzing their low molecular weight pyrolysis products. Most previous work restricts itself to C6+ pyrolysis products with only a few reports on the quantitative measurement of individual C1–C5 gaseous hydrocarbons. This is because of the difficulty in simultaneously separating C1–C5 efficiently. By using a GasPro capillary column to separate C1–C5 gaseous hydrocarbons and using polystyrene as external standard, we explore a quantitative Py-GC flame ionization detector (FID) method to study the C1–C5 pyrolysis products released from kerogens (coals) by primary cracking. Our study indicates that there is a good linear relationship between peak area of C1–C5 on Py-GC FID and kerogen sample weight. Based on the above methods, the yields of C1–C5 gaseous hydrocarbons released from various kerogen types were quantitatively studied. The results indicate that kerogen type plays a key role in controlling the compositions of C1–C5 gaseous hydrocarbons released by kerogen primary cracking under pyrolysis conditions. Type III kerogens (vitrinite rich coals) seem to have more abundant short alkyl chains linked to aromatic nuclei. Sequential flash pyrolysis at 800 °C, 1000 °C and 1200 °C suggests the generation mechanism of C1 is different from that of C2–C5. C2–C5 are mainly generated by the release of alkyl precursors while aromatization and condensation of the kerogen structure may also be an important source of C1 at high maturity, especially for type III kerogens (vitrinite rich coals). It seems to be a reliable way to study the generation mechanisms of C1–C5 by kerogen primary cracking and also the distribution of short alkyl chains within kerogen structure.

Solid bitumens occur extensively in Permian coral reefs of the Nanpanjiang Depression. Both potential source rocks and solid bitumens in the study area are highly overmature and have similar bulk carbon isotope values. It is difficult to perform an oil–source rock correlation study in this area based on only regular molecular geochemical methods and bulk carbon isotope values. Thus the covalently bound biomarkers released from solid bitumens and source rock kerogens by catalytic hydropyrolysis (HyPy), together with the geological settings, were taken into account in this oil–source rock correlation study. The distribution characteristics of covalently bound biomarkers suggest that the major source rock of the Longlin paleo-reservoir (in the midwest of the depression) solid bitumen should be the Middle Devonian mudstone, whereas the source rock of the Ziyun paleo-reservoir (in the north of the depression) solid bitumen should be the Lower Permian source rock. However, solid bitumens in the Ceheng and Wangmo paleo-reservoirs (in the middle of the depression) may be mainly sourced from the Middle Devonian source rock, but partly from the Permian source rock. Our bitumen–source rock correlation results are also supported by the petroleum geological settings of the study area, which indicate that the filling of those paleo-reservoirs was controlled by the matching of hydrocarbon generation and trap formation. Basically, the timing of hydrocarbon generation of the Middle Devonian source rocks matches well with the formation of Permian coral reef traps in the middle and midwest portions of the depression, but it is earlier than the formation of the Permian coral reef trap in the north of the depression. We show that our oil–source rock correlation study based on covalently bound biomarkers can provide reliable information for petroleum system analysis when highly overmature strata in South China are involved.

The Tianjingshan structure of the northern Longmen Mountain is located in the north of the Sichuan province, China. Two primary source rocks are present in this region, the overmature Infracambrian-Lower Cambrian source rocks and the mature Upper-Permian source rocks. Oil seeps and solid bitumens occur extensively in the Mesozoic and Paleozoic marine strata, indicating good exploration prospects in this area. However, oil-to-source correlation in the Tianjingshan structure is difficult due to both high maturity of the Lower Cambrian source rocks and severe biodegradation of oil seeps and bitumens. In this work, one oil seep from the Permian Qixia Formation and two severely degraded bitumens from the Cambrian strata in the Tianjingshan structure were correlated with their potential source rocks. Hydropyrolysis was used to release biomarkers bound to kerogen of the overmature Lower Cambrian source rock. The released biomarkers were used for the oil-to-source correlation together with those indexes resistant to thermal degradation and biodegradation. Based on the geochemical data and the petroleum geological settings of the area, it can be inferred that the Cambrian, Ordovician and Silurian bitumens with light bulk isotopic values (commonly δ 13 C

Seven reservoir core (tar sand) bitumens of identical source and similar maturity from the Liaohe Basin of northeast China possess a natural sequence of increasing severity of biodegradation. This set of samples provides us an opportunity to study the change in oil composition or compound class distributions with biodegradation severity by negative ion electrospray Fourier transform-ion cyclotron resonance mass spectrometry (FT ICR-MS). The bitumen extracts from two columns (Es3 and Es1) were separated into maltene and asphaltene fractions for analysis of heteroatomic species by ESI FT-ICR MS. The maltene fractions were found to mainly contain N1, N1O1, N1O2, N1O3, O1, O2, O3 and O4 classes, while the asphaltene fractions mainly contain N1, N2O1, N1O1, N1O2, N1O3, N1O4, O2, O3, O4 and O5 classes. These species identified by FT-ICR MS in asphaltene fractions are likely to be chemisorbed/coprecipitated compounds, or the species precipitated due to high polarity during deasphaltene process. The susceptibility of compound classes and homologous series to biodegradation was studied based on the relative abundances. The results indicate that microorganisms alter the distribution of acids and nitrogen-containing compounds by selective removal and preservation of certain classes of compounds according to their susceptibility to biodegradation. For example, O2 and N1O2 classes increase significantly while N1 and N1O1 classes decrease with biodegradation. The differences in the susceptibility to microbial alteration within acyclic acids, 4–5 ring acids and 1–2 ring acids are discussed and the differences in the susceptibility of homologous series of heteroatom-containing polycyclic aromatic hydrocarbons are also discussed in this work.

In this work, we have successfully demonstrated a facile strategy to incorporate high-quality hollow CoPt bimetal alloy nanoparticles (HCoPt) onto reduced graphene oxide sheet (HCoPt-RGs). An advanced sandwich-type electrochemical aptasensor for thrombin was proposed by using the HCoPt-RGs conjugates as secondary label. The formed conjugates provided large surface area for loading plentiful redox probe thionine (Thi), horseradish peroxidase (HRP) and secondary aptamer (Apt II) with good stability and friendly biocompatibility, indicating their superior properties in electroactive mediator enrichment and biomolecule immobilization. Furthermore, activated by glutaraldehyde (GA), the chitosan-hollow CoPt alloy nanoparticle (CS-HCoPt) film can greatly facilitate the capture of primary aptamer (Apt I) and dramatically reduce the nonspecific binding. Excellent sensitivity was obtained by detecting the conspicuously enhanced electrochemical signal of Thi, which was amplified by HCoPt alloy nanoparticles and HRP toward the catalytic reduction of H2O2. The aptasensor displayed excellent performance for thrombin with a wide linearity in the range from 1.0 × 10−12 to 5.0 × 10−8 M and a relatively low detection limit of 3.4 × 10−13 M. Moreover, the resulted aptasensor also exhibited good specificity, acceptable reproducibility and stability, indicating that the present strategy could pave a promising way for the wide application of graphene in clinical research.

Herein, we present an ultrasensitive protein-detection protocol based on electrochemiluminescence (ECL) quenching through capture of ferrocene-labeled ligand-bound aptamer molecular beacon (MB). Our device included two main parts: a solid-state ECL sensing platform and an ECL switch. The sensing platform was constructed by modifying the composite of tris(2,2′-bipyridyl) ruthenium(II) and platinum nanoparticles (Ru-PtNPs) and followed by immobilization of capture DNA (CaDNA). MB worked as the ECL intensity switch. In the presence of thrombin (TB), the hairpin-shaped MB binded to TB, inducing the exposure of a partial single-strand (MBs at this state was ligand-bound MBs). The exposed single stand was complementary to CaDNA and hybridized with CaDNA, leading to the capture of ligand-bound MB onto ECL sensing platform and finally resulting in ECL quenching by ferrocene that linked to MB. Otherwise, the ligand-unbound MB could not be captured and ECL quenching would not happen. Accordingly, the change of ECL intensity indirectly reflected the concentration of TB in the sample. The results indicated that our protocol realized recognition of TB directly in the solution and exhibited much higher sensitivity with a detection limit of 1.7 pM. Thus, this approach would be a promising protein-detection procedure directly performed in the solution.

Herein, an ultrasensitive solid-state tris(2,2'-bipyridyl) ruthenium(II) (Ru(bpy)(3)(2+)) electrochemiluminescence (ECL) aptasensor using in-situ produced ascorbic acid as coreactant was successfully constructed for detection of thrombin. Firstly, the composite of Ru(bpy)(3)(2+) and platinum nanoparticles (Ru-PtNPs) were immobilized onto Nafion coated glass carbon electrode, followed by successive adsorption of streptavidin-alkaine phosphatase conjugate (SA-ALP) and biotinylated anti-thrombin aptamer to successfully construct an ECL aptasensor for thrombin determination. In our design, Pt nanoparticles in Ru(bpy)(3)(2+)-Nafion film successfully inhibited the migration of Ru(bpy)(3)(2+) into the electrochemically hydrophobic region of Nafion and facilitated the electron transfer between Ru(bpy)(3)(2+) and electrode surface. Furthermore, ALP on the electrode surface could catalyze hydrolysis of ascorbic acid 2-phosphate to in-situ produce ascorbic acid, which co-reacted with Ru(bpy)(3)(2+) to obtain quite fast, stable and greatly amplified ECL signal. The experimental results indicated that the aptasensor exhibited good response for thrombin with excellent sensitivity, selectivity and stability. A linear range of 1 × 10(-15)-1 × 10(-8) M with an ultralow detection limit of 0.33 fM (S/N=3) was obtained. Thus, this procedure has great promise for detection of thrombin present at ultra-trace levels during early stage of diseases.

A approach was successfully employed for constructing a solid-state electrochemiluminescence (ECL) immunosensor by layer-by-layer self-assembly of multiwall carbon nanotubes (MWCNTs)-Nafion composite film, Ru(bpy)32+/nano-Pt aggregates (Ru-PtNPs) and Pt nanoparticles (PtNPs). The influence of Pt nanoparticles on the ECL intensity was quantitatively evaluated by calculating the electroactive surface area of different electrodes with or without PtNPs to immobilize Ru(bpy)32+. The principle of ECL detection for target α-fetoprotein antigen (AFP) was based on the increment of resistance after immunoreaction, which led to a decrease in ECL intensity. The linear response range was 0.01–10 ng mL−1 with the detection limit of 3.3 pg mL−1. The immunosensor exhibited advantages of simple preparation and operation, high sensitivity and good selectivity.

Asphaltenes are traditionally considered to be recalcitrant to microbial alteration. Resins and asphaltenes of seven biodegraded oils extracted from reservoir cores of two columns (Es3 and Es1) of the Lengdong oilfield in the Liaohe Basin, NE China, were studied to test this hypothesis. Elemental (C, H, N, O, S) and isotopic compositions (δ13C and δ15N) were measured, FT-IR was used to study the oxygenated functionalities of both resins and asphaltenes, and Py–GC–MS was used to elucidate how alkyl side chains of asphaltenes were altered during biodegradation. We conclude that the products of biodegradation, such as carboxylic acids, phenol and alcohols, may not only contribute to the resin fraction of crude oils, but also are linked with functionalities of resins and asphaltenes. The amount of asphaltenes increases because some resin molecules are enlarged and their polarity increased such that they can be precipitated by hexane as newly generated asphaltenes. Thus, the hydrocarbons that are progressively consumed during biodegradation can pull the δ13C of asphaltene fraction closer to the δ13C of the altered resins and hydrocarbons that were consumed.

An ultrasensitive electrochemiluminescence (ECL) immunosensor was constructed for ultrasensitive detection of carcinoembryonic antigen (CEA) based on an amplified cathodic ECL of luminol at low potential. Firstly, Au nanoparticles (AuNPs) were electrodeposited onto single walled carbon nanotube-graphene composites (CNTs-Gra) coated glass carbon electrode (GCE) with enhanced surface area and good biocompatibility to capture primary antibody (Ab1) and then bind the antigen analytes. Secondly, Pd and Pt nanoparticles (Pd&PtNPs) decorated reduced graphene oxide (Pd&PtNPs@rGO) and glucose oxidase (GOD) labeled secondary antibody (Pd&PtNPs@ rGO-GOD-Ab2) could be captured onto the electrode surface by a sandwich immunoassay protocol to generate amplified cathodic ECL signals of luminol in the presence of glucose. The Pd&PtNPs@rGO composites and loaded GOD promoted luminol cathodic ECL response by efficiently catalyzing glucose to in-situ produce amount of hydrogen peroxide (H2O2) working as a coreactant of luminol. Then in turn Pd&PtNPs catalyzed H2O2 to generate various reactive oxygen species (ROSs), which accelerated the cathodic ECL reaction of luminol, enhanced the cathodic ECL intensity of luminol and improved the sensitivity of the immunosensor. The as-proposed ECL immunosensor exhibited sensitive response on the detection of CEA ranging from 0.0001 ng mL(-1) to 160 ng mL(-1) with a detection limit of 0.03 pg mL(-1) (S/N=3). Moreover, the stability, specificity, lifetime and reproducibility tests demonstrated the feasibility of the developed immunoassay, which can be further extended to the detection of other disease biomarkers.

A novel tracer, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) functionalized graphene sheet (GS) composite (GS–TCDA), is employed to label the secondary anti-thrombin aptamer (TBA) to construct an ultrasensitive electrochemiluminescent sandwich-type aptasensor. The GS provided large surface area for loading abundant PTCDA and TBA with good stability and biocompatibility. Because of the excellent electroconductivity of GS and the desirable optical properties of PTCDA, the as-formed Apt II bioconjugate considerably amplified the electrochmiluminescence (ECL) signal of peroxydisulfate (S 2 O 8 2− ) and worked as the desirable label for Apt II. On the basis of the considerably amplified ECL signal and sandwich format, an extremely wide range from 1 fM to 1 nM with an ultralow detection limit of 0.33 fM for thrombin was obtained. Additionally, the selectivity and stability of the proposed aptasensor were also excellent. Thus, this procedure has great promise for detection of thrombin present at ultra-trace levels during early stage of diseases.

In the present study, a new electrochemical probe-label-free aptasensor for thrombin (TB) based on the amplification of gold–platinum alloy nanoparticles (Au–PtNPs) and stearic acid was reported. Nafion@multiwalled carbon nanotubes (MWCNTs) coated electrode was firstly modified with electrochemical probe of methylene blue (MB). Then, Au–PtNPs were electrodeposited onto the electrode surface for the immobilization of aptamer and further hybridization of stearic acid labeled thrombin aptamer (TBA). In the presence of TB, the TBA bound with TB and released from the self-assembled duplex on the electrode into solution, decreasing the steric hindrance of the aptasensor and facilitating catalytic efficiency of Au–PtNPs in the presence of MB toward H 2 O 2 with an enhanced electrochemical signal. With the enhanced effect of Au–PtNPs/MB modified electrode and stearic acid, a detection limit as low as 3 pM for TB was achieved. The aptasensor also exhibited good selectivity and reproducibility.

A signal amplificatory electrochemical immunoassay with biotin-streptavidin conjunction and multienzymatic-based substrate recycling was developed in this work. Biotinylated secondary antibody (bio-IgG) was preliminarily assembled onto the immunosensor interface based on the sandwich format. Streptavidin was then loaded based on biotin-streptavidin conjunction. Owing to four identical binding sites of streptavidin to biotin, amounts of biotinylated alkaline phosphatase (bio-AP) were attached, and this improved the catalytic performance of the proposed immunosensor. Under the enzyme catalysis of AP, the electroinactive p-aminophenylphosphate (PAPP) substrate was rapidly hydrolyzed into the electroactive p-aminophenol (PAP) product, which next oxidized at the electrode surface into p-quinoneimine (PQI). In the presence of diaphorase (DI), PQI was reduced back to PAP, leading to a reversible cycle of PAP. Then the oxidized state of DI was regenerated into its reduced native state by its natural substrate, nicotinamide adenine dinucleotide (NADH). With the several amplification factors mentioned above, a wider linear ranged from 10(-14) to 10(-5) gml(-1) was acquired with a relatively low detection limit of 3.5 x 10(-5) gml(-1) for human IgG. In addition, the nonspecific adsorption of proposed immunosensor was also investigated here.

In this work, protonated l -cysteine was entrapped in Nafion (Nf) membrane by cation exchange function, forming Nf–Cys (cysteine) composite membrane, which was more stable, compact, biocompatible, and favorable for mass and electron transfer compared with Nf film solely. Then gold (Au) nanoparticles were adsorbed onto the electrode surface by thiol groups on the composite membrane. After that, nano-Au monolayer was formed, onto which carcinoembryonic antibody was loaded to prepare carcinoembryonic antigen (CEA) immunosensor. The results indicated that the immunosensor had good current response for CEA using potassium ferricyanide as the redox probe. A linear concentration range of 0.01 to 100 ng/ml with a detection limit of 3.3 pg/ml (signal/noise = 3) was observed. Moreover, the morphology of the modified Au substrates was investigated with atomic force microscopy, and the electrochemical properties and performance of modified electrodes were investigated by cyclic voltammograms and electrochemical impendence spectroscopy. The results exhibited that the immunosensor has advantages of simple preparation, high sensitivity, good stability, and long life expectancy. Thus, the method can be used for CEA analysis.

The Permian Dalong Formation (P2 d) source rocks from the mature Guangyuan outcrop section and the overmature Wangcang outcrop section in Sichuan Basin were selected. The Soxhlet extraction and kerogen catalytic HyPy were conducted on the P2 d source rocks. The biomarkers obtained by both methods were compared to discuss their difference and the influence extent of thermal maturation on covalently bound biomarkers. The results show that covalently bound biomarkers can hardly be correlated to the corresponding free biomarkers due to severe thermal alterations and/or interference of migrated hydrocarbons in both outcrop sections and thermal maturation have much lower influence on covalently bound biomarkers in kerogens than on free biomarkers in Soxhlet extracts. The application of HyPy in study of biomarker geochemistry can reduce the thermal maturation effect on biomarkers (R o⩾2.4%) to a greater extent and the interference of migrated hydrocarbons between interbedded layers. The covalently bound biomarkers released by HyPy are useful in the study of biomarker geochemistry and oil-source correlation on high-overmature source rocks.