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24261. 题目: Ag-doping on ZnO support mediated by bio-analytes rich in ascorbic acid for photocatalytic degradation of dipyrone drug
文章编号: N18060212
期刊: Chemosphere
作者: Venkatanarasimha Rao Chelli, Animes Kumar Golder
更新时间: 2018-06-02
摘要: The analytes such as ascorbic acid (AA) present in Sechium edule were extracted (294 mg AA kg-1 fruit) in an aqueous media for its potential application for Ag-doping onto wurtzite ZnO. The bandgap of ZnO was decreased to 2.85 eV at the optimal Ag-loading of 1.18% (w/w) against 3.13 eV for the control catalyst without using the analytes and, the commercial AA only could reduce the bandgap to 2.91 eV. The saturation photo-electrochemical current density (46.68 mA cm-2) at Eanode ≥ 0.31 V vs. Ag/AgCl was almost double than pristine ZnO under visible light illumination (λ mean = 525 nm, 18 K lux) and, the current density was insignificant in the dark. The doped catalyst exhibited the maximum 79.5% degradation (71% COD removal) of an anti-analgesic drug, dipyrone (100 μg L-1 dipyrone, catalyst 100 mg L-1) resulted from the formation of O2 - radical (g-factor of 2.002–2.008) and paramagnetic oxygen vacancies (g-factor of 2.020) and, no effect of dye-sensitization was noted. The highest quantum yield was found to be 34.7%. The catalyst loss was 6% after the fourth cycle and the dipyrone degradation was reduced to 70.8%.
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24262. 题目: Effects of coating materials on antibacterial properties of industrial and sunscreen-derived titanium-dioxide nanoparticles on Escherichia coli
文章编号: N18060211
期刊: Chemosphere
作者: Soyoung Baek, Sung Hee Joo, Pat Blackwelder, Michal Toborek
更新时间: 2018-06-02
摘要: Organic or inorganic stabilizers are often used for coating nanoparticles (NPs) in consumer products. However, upon release of stabilized NPs into the environment, uncertainty exists as to the antimicrobial properties of NPs due to stabilizers and the resultant bioaccumulation in organisms. This study investigates antibacterial effects and subsequent mechanisms of TiO2 NPs on Escherichia coli (E. coli) in the presence and absence of stabilizers (CMC, PVP, and SiO2) commonly used in consumer products. Compared with uncoated TiO2 NPs, the presence of any stabilizers tested in this study increased toxicity of NPs and enhanced growth inhibition in E. coli. While the particle sizes of TiO2 were smaller as the result of coating with PVP or CMC and appeared to contribute to E. coli cell damage, the generation of reactive oxygen species (ROS) was independent of stabilizer type. In fact, coating with PVP and CMC exerted ROS scavenging properties. In contrast, increased ROS production was observed at higher concentrations of TiO2 and upon coating with SiO2. This impact of SiO2 can be related to the formation of a Ti O Si chemical bond. The results of the present study emphasize the importance of nanoparticle coating to their anti-bacterial activity and toxicity.

24263. 题目: Rapid fingerprinting of spilled petroleum products using fluorescence spectroscopy coupled with parallel factor and principal component analysis
文章编号: N18060210
期刊: Chemosphere
作者: Fatemeh S. Mirnaghi, Nicholas Soucy, Bruce P. Hollebone, Carl E. Brown
更新时间: 2018-06-02
摘要: The characterization of spilled petroleum products in an oil spill is necessary for identifying the spill source, selection of clean-up strategies, and evaluating potential environmental and ecological impacts. Existing standard methods for the chemical characterization of spilled oils are time-consuming due to the lengthy sample preparation for analysis. The main objective of this study is the development of a rapid screening method for the fingerprinting of spilled petroleum products using excitation/emission matrix (EEM) fluorescence spectroscopy, thereby delivering a preliminary evaluation of the petroleum products within hours after a spill. In addition, the developed model can be used for monitoring the changes of aromatic compositions of known spilled oils over time. This study involves establishing a fingerprinting model based on the composition of polycyclic and heterocyclic aromatic hydrocarbons (PAH and HAHs, respectively) of 130 petroleum products at different states of evaporative weathering. The screening model was developed using parallel factor analysis (PARAFAC) of a large EEM dataset. The significant fluorescing components for each sample class were determined. After which, through principal component analysis (PCA), the variation of scores of their modeled factors was discriminated based on the different classes of petroleum products. This model was then validated using gas chromatography-mass spectrometry (GC-MS) analysis. The rapid fingerprinting and the identification of unknown and new spilled oils occurs through matching the spilled product with the products of the developed model. Finally, it was shown that HAH compounds in asphaltene and resins contribute to ≥4-ring PAHs compounds in petroleum products.
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24264. 题目: Enhanced biofiltration of O&G produced water comparing granular activated carbon and nutrients
文章编号: N18060209
期刊: Science of The Total Environment
作者: Stephanie M. Riley, Danika C. Ahoor, Tzahi Y. Cath
更新时间: 2018-06-02
摘要: Large volumes of water are required for the development of unconventional oil and gas (O&G) wells. Water scarcity coupled with seismicity induced by deep-well disposal promote new O&G wastewater management strategies, specifically treatment and reuse. One technology that has been proven effective for removal of organic matter and solids is biologically active filtration (BAF) with granular active carbon (GAC); however, further optimization is needed to enhance BAF performance. This study evaluated three GAC media (one spent and two new) and two nutrient-mix supplements for enhanced removal of chemical oxygen demand (COD) and dissolved organic carbon (DOC). Biofilm development was also monitored and correlated to BAF performance. The spent GAC with extant biofilm quickly acclimated to PW and demonstrated up to 92% DOC removal (81% COD) in 24h, while little impact by nutrient addition was observed. In addition, virgin GAC was slow to establish a biofilm, indicating that appropriate GAC selection and pre-developed biofilm is critical for efficient BAF performance. Furthermore, the production of high quality BAF effluent (less than 20mg/L DOC) presents the opportunity to apply BAF as a pretreatment for subsequent desalination—expanding the potential for reuse applications of PW.
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24265. 题目: Geochemical modeling of mercury speciation in surface water and implications on mercury cycling in the everglades wetland
文章编号: N18060208
期刊: Science of The Total Environment
作者: Ping Jiang, Guangliang Liu, Wenbin Cui, Yong Cai
更新时间: 2018-06-02
摘要: The geochemical model PHREEQC, abbreviated from PH (pH), RE (redox), EQ (equilibrium), and C (program written in C), was employed on the datasets generated by the USEPA Everglades Regional Environmental Monitoring and Assessment Program (R-EMAP) to determine the speciation distribution of inorganic mercury (iHg) in Everglades water and to explore the implications of iHg speciation on mercury cycling. The results suggest that sulfide and DOM were the key factors that regulate inorganic Hg speciation in the Everglades. When sulfide was present at measurable concentrations (>0.02 mg/L), Hg-S complexes dominated iHg species, occurring in the forms of HgS2 2-, HgHS2 -, and Hg(HS)2 that were affected by a variety of environmental factors. When sulfide was assumed nonexistent, Hg-DOM complexes occurred as the predominant Hg species, accounting for almost 100% of iHg species. However, when sulfide was presumably present at a very low, environmentally relevant concentration (3.2 × 10-7 mg/L), both Hg-DOM and Hg-S complexes were present as the major iHg species. These Hg-S species and Hg-DOM complex could be related to methylmercury (MeHg) in environmental matrices such floc, periphyton, and soil, and the correlations are dependent upon different circumstances (e.g., sulfide concentrations). The implications of the distribution of iHg species on MeHg production and fate in the Everglades were discussed.
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24266. 题目: Seasonal changes in dissolved organic matter composition in Delaware Bay, USA in March and August 2014
文章编号: N18060207
期刊: Organic Geochemistry
作者: Leanne C. Powers, Jenna L. Luek, Philippe Schmitt-Kopplin, Barbara J. Campbell, Cédric Magen, Lee W. Cooper, Michael Gonsior
更新时间: 2018-06-02
摘要: We combined Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and mass spectrometric analysis of stable carbon isotopes, a traditional method for tracking DOM sources, to investigate the variation in the complexity of water samples collected along a salinity gradient in Delaware Bay in March and August 2014. Detailed analyses of optical properties (ultraviolet and visible (UV–Vis) absorbance and excitation-emission matrix (EEM) fluorescence spectroscopy) were carried out. Results from statistical parallel factor analysis (PARAFAC) of EEM data were also used to track and further constrain fluorescent DOM (FDOM). Optical analyses and FT-ICR-MS data showed large differences between late winter and summer conditions, and the stable carbon isotopic composition was more variable in summer than in late winter. Although terrestrial inputs of DOM are evident at low salinities in both seasons, our data suggest that a significant source of FDOM, from either in situ water column production or from benthic aquatic or semi-aquatic plant communities, contributes DOM to low and mid-salinity waters in Delaware Bay during summer but not in late winter.

24267. 题目: Variable apparent hydrogen isotopic fractionation between sedimentary n-alkanes and precipitation on the Tibetan Plateau
文章编号: N18060206
期刊: Organic Geochemistry
作者: Juzhi Hou, Qian Tian, Mingda Wang
更新时间: 2018-06-02
摘要: The hydrogen isotope ratio values of sedimentary leaf wax n-alkanes (δDwax) have been considered a reliable proxy for precipitation isotope ratios (δDP) across various transects on a global basis. Records of δDwax have been used to infer past changes in hydrology, climate and altimetry, assuming nearly constant apparent hydrogen isotopic fractionation (εwax-P) between sedimentary leaf wax components and precipitation. Here, we present the results of an analysis of δDwax values from the surface sediments of 22 lakes across a precipitation and vegetation gradient on the Tibetan Plateau. The δDwax values correlated significantly with mean annual precipitation δD (r 0.90) and summer precipitation δD (r 0.91), suggesting that δDwax can record δDP in very dry regions. However, εwax-P varies with annual precipitation as well as with relative humidity. Calculation using Craig-Gordon isotope models showed that the variable εwax-P values likely resulted from intensive soil evaporation and plant evapotranspiration in this relatively arid region. This implies that variable isotopic fractionation should be taken into consideration when reconstructing paleohydrology, paleoclimate and paleoaltimetry.

24268. 题目: Moderate KMnO4-Fe(II) pre-oxidation for alleviating ultrafiltration membrane fouling by algae during drinking water treatment
文章编号: N18060205
期刊: Water Research
作者: Baiwen Ma, Jing Qi, Xing Wang, Min Ma, Shiyu Miao, Wenjiang Li, Ruiping Liu, Huijuan Liu, Jiuhui Qu
更新时间: 2018-06-02
摘要: Although ultrafiltration (UF) membranes are highly beneficial for removing algae, the removal process causes serious UF membrane fouling. To avoid the unfavorable effects of algal cells that have been damaged by oxidants, our previous study reported a novel, moderate pre-oxidation method (KMnO4-Fe(II) process) that aimed to achieve a balance between the release of intracellular organic matter and enhanced algae removal. This study further investigated the performance of a UF membrane with KMnO4-Fe(II) pretreatment in the presence of algae-laden reservoir water after a long running time. We found that algae could be completely removed, membrane fouling was significantly alleviated, and the overall performance was much better than that of Fe(III) coagulation alone. The transmembrane pressure (TMP) during Fe(III) coagulation increased to 42.8 kPa, however, that of the KMnO4-Fe(II) process only increased to 25.1 kPa for after running for 90 d. The slower transmembrane pressure was attributed to the larger floc size, higher surface activity, and inactivation of algae. Although there was little effect on microorganism development, lower microorganism abundance (20.7%) was observed during the KMnO4-Fe(II) process than during coagulation alone (44.9%) due to the release of extracellular polymeric substances. We also found that the floc cake layer was easily removed by washing, and many of the original membrane pores were clearly observed. Further analysis demonstrated that the effluent quality was excellent, especially its turbidity, chromaticity, and Mn and Fe concentrations. Based on the outstanding UF membrane performance, it may be concluded that the KMnO4-Fe(II) process exhibits considerable potential for application in the treatment of algae-laden water.
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24269. 题目: The role of salinity on the changes of the biomass characteristics and on the performance of an OMBR treating tannery wastewater
文章编号: N18060204
期刊: Water Research
作者: M.J. Luján-Facundo, J. Fernández-Navarro, J.L. Alonso-Molina, I. Amorós-Mu?oz, Y. Moreno, J.A. Mendoza-Roca, L. Pastor-Alca?iz
更新时间: 2018-06-02
摘要: Tannery wastewaters are difficult to treat biologically due to the high salinity and organic matter concentration. Conventional treatments, like sequential batch reactors (SBR) and membrane bioreactors (MBR), have showed settling problems, in the case of SBR, and ultrafiltration (UF) membrane fouling in the case of MBR, slowing their industrial application. In this work, the treatment of tannery wastewater with an osmotic membrane bioreactor (OMBR) is assessed. Forward osmosis (FO) membranes are characterized by a much lower fouling degree than UF membranes. The permeate passes through the membrane pores (practically only water by the high membrane rejection) from the feed solution to the draw solution, which is also an industrial wastewater (ammonia absorption effluent) in this work. Experiments were carried out at laboratory scale with a FO CTA-NW membrane from Hydration Technology Innovations (HTI). Tannery wastewater was treated by means of an OMBR using as DS an actual industrial wastewater mainly consisting of ammonium sulphate. The monitoring of the biological process was carried out with biological indicators like microbial hydrolytic enzymatic activities, dissolved and total adenosine triphosphate (ATP) in the mixed liquor and microbial population. Results indicated a limiting conductivity in the reactor of 35 mS cm-1 (on the 43th operation day), from which process was deteriorated. This process performance diminution was associated by a high decrease of the dehydrogenase activity and a sudden increase of the protease and lipase activities. The increase of the bacterial stress index also described appropriately the process performance. Regarding the relative abundance of bacterial phylotypes, 37 phyla were identified in the biomass. Proteobacteria were the most abundant (varying the relative abundance between 50.29% and 34.78%) during the first 34 days of operation. From this day on, Bacteroidetes were detected in a greater extent varying the relative abundance of this phylum between 27.20% and 40.45%.
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24270. 题目: Transformation of dissolved organic matters produced from alkaline-ultrasonic sludge pretreatment in anaerobic digestion: From macro to micro
文章编号: N18060203
期刊: Water Research
作者: Dan Lu, Keke Xiao, Yun Chen, Yan Ni Annie Soh, Yan Zhou
更新时间: 2018-06-02
摘要: Soluble organic compounds released by alkaline (ALK), ultrasonic (ULS) and combined alkaline-ultrasonic (ALK-ULS) pretreatment as well as their transformation in the anaerobic digestion systems were investigated. The maximum methane production of 197.1 ± 3.0 mL CH4/g tCODfeed was observed with ALK-ULS pretreated sludge (pH 12 and specific energy input of 24 kJ/g TS). The combined treatment likely enhanced the sludge solubilization and produced more low molecular weight (LMW) substances, which were beneficial to improve the biogas generation rate. However, such pretreatment released not only easily biodegradable substances but also more recalcitrants, such as humic substances (HS) and complex high molecular weight (HMW) proteins. Thus, more residual dissolved organic matters (DOMs) were detected after digestion, which may pose adverse effects on the downstream water treatment. Refractory HS and hydrophobic dissolved organic carbon (HO DOC) were the main components of the residual DOMs, which accounted up to 35.0% and 22.3% respectively. At the molecular level, a large amount of residual polycyclic steroid-like matters, alkanes and aromatics were identified. Specific higher MW residual compounds, e.g. polar metabolites (like dipeptide, benzene and substituted derivatives), and non-polar lipids (like diacylglycerols, long chain fatty acids, alkenes, flavonoids, sphingolipids, glycerolipids, glycerophospholipids and their derivatives) were also identified. The results indicate that further polishing steps should be considered to remove the remaining soluble recalcitrant compounds. This study helps to understand the insight of sludge treatment from macro to micro level.
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24271. 题目: Impact of natural organic matter and increased water hardness on DGT prediction of copper bioaccumulation by yellow lampmussel (Lampsilis cariosa) and fathead minnow (Pimephales promelas)
文章编号: N18060202
期刊: Environmental Pollution
作者: Rebecca R. Philipps, Xiaoyu Xu, Gary L. Mills, Robert B. Bringolf
更新时间: 2018-06-02
摘要: We conducted an exposure experiment with Diffusive Gradients in Thin- Films (DGT), fathead minnow (Pimephales promelas), and yellow lampmussel (Lampsilis cariosa) to estimate bioavailability and bioaccumulation of Cu. We hypothesized that Cu concentrations measured by DGT can be used to predict Cu accumulation in aquatic animals and alterations of water chemistry can affect DGT's predict ability. Three water chemistries (control soft water, hard water, and addition of natural organic matter (NOM)) and three Cu concentrations (0, 30, and 60 μg/L) were selected, so nine Cu-water chemistry combinations were used. NOM addition treatments resulted in decreased concentrations of DGT-measured Cu and free Cu ion predicted by Biotic Ligand Model (BLM). Both hard water and NOM addition treatments had reduced concentrations of Cu ion and Cu-dissolved organic matter complexes compared to other treatments. DGT-measured Cu concentrations were linearly correlated to fish accumulated Cu, but not to mussel accumulated Cu. Concentrations of bioavailable Cu predicted by BLM, the species complexed with biotic ligands of aquatic organisms and, was highly correlated to DGT-measured Cu. In general, DGT-measured Cu fit Cu accumulations in fish, and this passive sampling technique is acceptable at predicting Cu concentrations in fish in waters with low NOM concentrations.
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24272. 题目: Combined effects of coagulation and adsorption on ultrafiltration membrane fouling control and subsequent disinfection in drinking water treatment
文章编号: N18060201
期刊: Environmental Science and Pollution Research
作者: Jiajian Xing, Heng Liang, Xiaoxiang Cheng, Haiyan Yang, Daliang Xu, Zhendong Gan, Xinsheng Luo, Xuewu Zhu, Guibai Li
更新时间: 2018-06-02
摘要: This study investigated the combined effects of coagulation and powdered activated carbon (PAC) adsorption on ultrafiltration (UF) membrane fouling control and subsequent disinfection efficiency through filtration performance, dissolved organic carbon (DOC) removal, fluorescence excitation-emission matrix (EEM) spectroscopy, and disinfectant curve. The fouling behavior of UF membrane was comprehensively analyzed especially in terms of pollutant removal and fouling reversibility to understand the mechanism of fouling accumulation and disinfectant dose reduction. Pre-coagulation with or without adsorption both achieved remarkable effect of fouling mitigation and disinfection dose reduction. The two pretreatments were effective in total fouling control and pre-coagulation combined with PAC adsorption even decreased hydraulically irreversible fouling notably. Besides, pre-coagulation decreased residual disinfectant decline due to the removal of hydrophobic components of natural organic matters (NOM). Pre-coagulation combined with adsorption had a synergistic effect on further disinfectant decline rate reduction and decreased total disinfectant consumption due to additional removal of hydrophilic NOM by PAC adsorption. The disinfectant demand was further reduced after membrane. These results show that membrane fouling and disinfectant dose can be reduced in UF coupled with pretreatment, which could lead to the avoidance of excessive operation cost disinfectant dose for drinking water supply.

24273. 题目: Microbial decomposition of marine dissolved organic matter in cool oceanic crust
文章编号: N18060136
期刊: Nature Geoscience
作者: Sunita R. Shah Walter, Ulrike Jaekel, Helena Osterholz, Andrew T. Fisher, Julie A. Huber, Ann Pearson, Thorsten Dittmar, Peter R. Girguis
更新时间: 2018-06-01
摘要: Marine dissolved organic carbon (DOC) is one of the largest active reservoirs of reduced carbon on Earth. In the deep ocean, DOC has been described as biologically recalcitrant and has a radiocarbon age of 4,000 to 6,000 years, which far exceeds the timescale of ocean overturning. However, abiotic removal mechanisms cannot account for the full magnitude of deep-ocean DOC loss. Deep-ocean water circulates at low temperatures through volcanic crust on ridge flanks, but little is known about the associated biogeochemical processes and carbon cycling. Here we present analyses of DOC in fluids from two borehole observatories installed in crustal rocks west of the Mid-Atlantic Ridge, and show that deep-ocean DOC is removed from these cool circulating fluids. The removal mechanism is isotopically selective and causes a shift in specific features of molecular composition, consistent with microbe-mediated oxidation. We suggest organic molecules with an average radiocarbon age of 3,200 years are bioavailable to crustal microbes, and that this removal mechanism may account for at least 5% of the global loss of DOC in the deep ocean. Cool crustal circulation probably contributes to maintaining the deep ocean as a reservoir of ‘aged’ and refractory DOC by discharging the surviving organic carbon constituents that are molecularly degraded and depleted in 14C and 13C into the deep ocean.

24274. 题目: Aliphatic hydrocarbon biomarkers as indicators of organic matter source and composition in surface sediments from shallow lakes along the lower Yangtze River, Eastern China
文章编号: N18060135
期刊: Organic Geochemistry
作者: Yongdong Zhang, Yaling Su, Zhengwen Liu, Lingyang Kong, Jinlei Yu, Miao Jin
更新时间: 2018-06-01
摘要: Aliphatic hydrocarbon biomarkers from the surface sediments of lakes along the lower reaches of the Yangtze River (Eastern China) were analyzed in order to determine the origin and composition of organic matter (OM) in the sediment. This is necessary to understand how anthropogenic environmental change in the region is impacting on OM dynamics and carbon cycles. The results indicate that OM in lake sediments is derived from biogenic sources, including phytoplankton, aquatic macrophytes, bacteria and terrestrial plants and abiotic sources of petroleum hydrocarbon contamination. The significance of each source varies greatly between lakes. Inputs of autochthonous OM to sediments were closely dependent on nutrient levels and the organisms present in the lake water column. Cyanobacterial OM input, signified by the distribution of short-chain n-alkanes, was most abundant in sediments from the most severely polluted lake, West Lake Chaohu. OM derived from diatoms, indicated by C25 highly branched isoprenoids (HBIs), was relatively abundant in sediments from lakes Gucheng and Shijiu, the two studied lakes with the lowest nutrient levels. Growth of macrophytes in lakes Gucheng, Shijiu, Gehu and Yangcheng resulted in a significant accumulation of OM from these organisms in the sediments. In contrast, the input of allochthonous OM was controlled mainly by natural and anthropogenic activities around the lakes. For example, terrestrial plant OM input, deduced from the abundance and proportion of long-chain n-alkanes, was exceptionally high in the sediment of Lake Nanyi, perhaps stemmed from frequent severe flooding in the catchment. Input of fossil fuel OM reflected direct petroleum contamination of the water or anthropogenic petroleum burning in the catchment. In addition, the allochthonous refractory OM tended to be enriched in sediments of lakes with strong hydrodynamic process. The results of this study provided a lot of detail in explaining the variation of terrestrial OM dynamics and carbon cycle in response to anthropogenic activities.

24275. 题目: Change in provenance of branched glycerol dialkyl glycerol tetraethers over the Holocene in the Baltic Sea and its impact on continental climate reconstruction
文章编号: N18060134
期刊: Organic Geochemistry
作者: Lisa Warden, Matthias Moros, Yuki Weber, Jaap S. Sinninghe Damsté
更新时间: 2018-06-01
摘要: The Baltic Sea is an enclosed basin that experienced a number of different salinity phases during the Holocene corresponding to the establishment of a connection with the North Sea. Branched glycerol dialkyl glycerol tetraethers (brGDGTs) in surface sediments and Holocene sedimentary successions from the Gotland and Arkona Basins were analyzed to examine their potential applicability as indicators for soil organic matter input, as well as their suitability for paleoclimate reconstructions. Our results show a marked change in brGDGT distributions and the branched and isoprenoid tetraether (BIT) index. The transition of the Ancylus Lake (fresh) to the Littorina Sea (brackish) phase is revealed by a large drop in the BIT index and an increase in the MBT′5Me, which reveals a large shift in provenance of the sedimentary brGDGTs. During the lake phase, brGDGTs are presumed to be primarily produced by in situ production in the water column. During the brackish phase, in situ brGDGT production in the alkaline pore waters of the surface sediments (as revealed by their high degree of cyclization) was predominant although there was evidence of occasional input of soil-derived brGDGTs. The predominant aquatic autochthonous production of brGDGTs does not allow the use of brGDGTs for continental air temperature reconstructions but they can be used for bottom water and lake temperature reconstructions during some intervals. The results from this study demonstrate that geological changes and concomittant salinity variations can be revealed by the provenance of brGDGTs.

24276. 题目: Correction for the siderite effect on Rock-Eval parameters: Application to the sediments of Lake Barombi (southwest Cameroon)
文章编号: N18060133
期刊: Organic Geochemistry
作者: David Sebag, Yannick Garcin, Thierry Adatte, Pierre Deschamps, Guillemette Ménot, Eric P. Verrecchia
更新时间: 2018-06-01
摘要: Originally developed for use in the petroleum industry, Rock-Eval pyrolysis is a technique commonly applied to lake sediments to infer paleoenvironmental reconstructions. The standard Rock-Eval parameters provide information on the amount of total organic and inorganic carbon (TOC and MinC, respectively), and are usually interpreted as proxies for the source (aquatic or terrestrial) of the primary production of organic matter (Hydrogen Index vs Oxygen Index). Although this method usually provides valuable evidence, the common presence of siderite in tropical lake sediments can alter the primary signal of the sedimentary organic matter (SOM). Indeed, the CO2 and CO released by the pyrolysis of siderite are integral to the calculation of the SOM-related standard Rock-Eval parameters. In this study, we analyze sediments from a core collected in the Lake Barombi (southwest Cameroon) and describe the impact of siderite on standard Rock-Eval parameters. We propose a workflow that allows standard Rock-Eval parameters to be corrected, based on the analysis of thermograms. The proposed corrections provide siderite-effect-free parameters, accurately reflecting the changes in sedimentary organic matter composition.

24277. 题目: Determination and geochemical implication of multiple series of long-chain oxygen-bearing compounds trapped in kerogen in the Lucaogou Formation, Santanghu Basin, NW China
文章编号: N18060132
期刊: Organic Geochemistry
作者: Bin Cheng, Jianbing Xu, Yungan Liang, Qian Deng, Yankuan Tian, Zewen Liao
更新时间: 2018-06-01
摘要: Studies of occluded oxygen-bearing compounds inside kerogen are scarce, although such studies are important in understanding early-stage transformation of organic matter. A relatively low-maturity kerogen from the late Permian mudstone of the Lucaogou Formation of the Santanghu Basin, northwestern China, was successively extracted with n-hexane, acetone and dichloromethane to release the adsorbed components, and the extracted kerogen was treated with a mild oxidation reagent H2O2 to release the occluded components. Gas chromatography–mass spectrometry analysis of the adsorbed and occluded components revealed a suite of oxygen-bearing compounds, including n-alkan-2-ones, n-aldehydes and fatty acid methyl esters. The n-alkan-2-ones were mainly detected in the adsorbed fraction and n-aldehydes in the occluded component. Comparison of the long-chain oxygen-bearing compound distributions and their individual stable carbon isotope characteristics both suggest that the oxygen-bearing compounds released by H2O2 treatment were occluded in the kerogen. The shorter-chain (C15 to C19) occluded n-aldehydes reflected similar isotopic distribution trends to the adsorbed n-alkan-2-ones, and the δ13C values of the mid-length (C21 to C25) occluded n-aldehydes were much closer to the adsorbed n-alkanes. Bacterially mediated methylation and decarbonylation of the n-aldehydes during kerogen formation may be important source(s) of n-alkan-2-ones and n-alkanes, respectively. The mid-chain ketones mainly originated from hydrothermal alteration of n-alkanes after kerogen formation. Uplift of the Lucaogou Formation in the Yuejingou section allowed surface-enhanced aerobic reactions.

24278. 题目: Effect of simulated diagenesis on the compositions, chemical stability and sorption properties of natural and engineered organic matter with different mineral contents
文章编号: N18060131
期刊: Organic Geochemistry
作者: Lanfang Han, Ziying Wang, Marco Keiluweit, Yan Yang, Ke Sun, Zheyun Zhang, Baoshan Xing
更新时间: 2018-06-01
摘要: Despite the abundance of diagenetically derived organic materials in the environment, the effects of diagenesis on the structure and some of the associated properties (e.g., stability and sorption behavior) of organic matter (OM) remain unclear. Here, subcritical water treatment, suggested previously to mimic the diagenesis process, was chosen to further investigate the impact of diagenesis on OM compositions, stability and sorption of selected hydrophobic organic compounds. Humic acids and biochars were selected as representatives of natural and engineered OM, respectively. To examine the impact of mineral constituents on the diagenesis of OM, de-ashed samples, as well as samples amended with minerals (kaolinite, calcite and calcium dihydrogen phosphate), were included in the diagenesis treatment system. Comparison of OM composition before and after treatment indicated that simulated diagenesis resulted in lower bulk polarity, higher surface polarity and aromaticity and greater microporosity. Thermal analysis and chemical oxidation suggested that as a result of the increase in aromaticity and decrease in O/C ratio of OM, the resistance of OM to thermal and chemical oxidation was enhanced after simulated diagenesis. Moreover, our diagenesis treatment of OM induced stronger sorption nonlinearity and higher sorption capacity, for phenanthrene. Additionally, minerals protected the structure of OM from being changed by simulated diagenesis. Consequently, with regard to the susceptibility of OM to oxidative decay, the presence of minerals mitigated the increase in chemical stability imparted by simulated diagenesis but, on the other hand, protected OM from degradation.

24279. 题目: Geochemical characterization of lacustrine and marine oils from off-shore Brazilian sedimentary basins using negative-ion electrospray Fourier transform ion cyclotron resonance mass spectrometry (ESI FTICR-MS)
文章编号: N18060130
期刊: Organic Geochemistry
作者: Ygor dos Santos Rocha, Rosana Cardoso Lopes Pereira, Jo?o Graciano Mendon?a Filho
更新时间: 2018-06-01
摘要: Lacustrine and marine crude oils from different off-shore Brazilian basins were analyzed using a 7.2 Tesla LTQ FTICR-MS instrument. The samples were analyzed via electrospray ionization in the negative ion mode focusing on the polar compounds, i.e., nitrogen-, sulfur-, and oxygen-containing (NSO) compounds. We also employed a combination of other geochemical methods, such as GC-FID and GC-MS analyses, to characterize and assess the depositional environments of the different oil families. The results indicate that lacustrine oils tend to be enriched in Nx compounds, while marine oils show preference for Ox compounds. The dominant heteroatomic classes in crude oils are N1, followed by O1, O2, and N1O1 with remarkable differences in their distributions between marine and lacustrine, strongly suggesting the control by the kerogen type of the heteroatomic compounds found in these crude oils. Considerable differences in the DBE distribution of the main classes analyzed between the crude oils allowed an efficient geochemical characterization regarding their origin. The use of negative ESI FTICR-MS as a geochemistry tool can provide additional information beyond that obtained with currently employed geochemical methods, resulting in the full comprehension of crude oil composition.

24280. 题目: Influence of vegetation type on n-alkane composition and hydrogen isotope values from a high latitude ombrotrophic bog
文章编号: N18060129
期刊: Organic Geochemistry
作者: Nicholas L. Balascio, William J. D'Andrea, R. Scott Anderson, Stephen Wickler
更新时间: 2018-06-01
摘要: The composition and hydrogen isotope values of leaf wax components can be powerful tools in reconstructing past climate and environments. However, interpretation of past environmental conditions from such components in sediments is complicated by species-specific influences and there is a need to better understand how vegetation type affects leaf wax composition and isotope ratios in modern environments. In this study we analyzed leaf wax (n-alkane) distributions and hydrogen isotope values of plants from a high latitude ombrotrophic bog in northern Norway. The isotopic analysis of surface water was also conducted on samples from 15 lakes along a ca. 150 km transect to contextualize the bog water isotopic composition and constrain fractionation factors among n-alkane homologues. We identified 14 different plant types growing on the bog surface, including mosses, graminoids and other herbs, sub-shrubs and a tree. n-Alkanes from the leaves of the modern plants had average chain lengths from 25 to 30.5, with a variety of distributions, and with the dominant compound of longer chain lengths (C27, C29, or C31). δD values of n-C25 to n-C33 for the vegetation samples ranged from -197‰ to -116‰, with an average of -162‰. The data also revealed that the δD values for the homologues for half of the vegetation types had ranges that were ≥20‰. Using the average isotopic value of bog water samples, -60‰, we calculated apparent fractionation factors that ranged from -66‰ to -134‰ (avg. -108 ± 22‰), similar to other sites across Europe and to a global data compilation. Our results demonstrate the range of species-specific influences on leaf wax composition and isotopic values at this site and presumably other ombrotrophic bog environments, and provide a dataset to help evaluate the influence of vegetation type on regional sedimentary leaf wax records.