论文检索

主页 | 软件工具 | 课题库 | 公众号
:



总访问量:1733817

总访客量:86888

关键词:
Organic Matter |
DOM |
POM |
Soil OM |
Sediment OM |
Organic Carbon |
Organic Nitrogen |
Biomarker |
Humic Substances |
Fulvic Substances |
Humins |
Biochar |
Black Carbon |
GDGT |
Lignin |
Free Radical |
...
最新文章  | 
昨日文章 | 
前日文章
期刊:
Agriculture, Ecosystems & Environment |
Agricultural Water Management |
Applied Geochemistry |
Applied Soil Ecology |
Aquatic Geochemistry |
Atmospheric Research |
Biogeochemistry |
Biogeosciences |
Biology and Fertility of Soils |
Bioresource Technology |
CATENA |
Chemical Engineering Journal |
Chemical Geology |
Chemosphere |
CLEAN - Soil, Air, Water |
Colloids and Surfaces A: Physicochemical and Engineering Aspects |
Deep Sea Research Part II: Topical Studies in Oceanography |
Earth-Science Reviews |
Ecological Engineering |
Ecology Letters |
Ecology |
Ecotoxicology and Environmental Safety |
Environment International |
Environmental Earth Sciences |
Environmental Geochemistry and Health |
Environmental Monitoring and Assessment |
Environmental Pollution |
Environmental Research |
Environmental Science & Technology |
Environmental Science and Pollution Research |
Environmental Science: Processes Impacts |
Environmental Science: Water Research & Technology |
Environmental Toxicology and Chemistry |
Estuarine, Coastal and Shelf Science |
European Journal of Soil Science |
Forest Ecology and Management |
Geochimica et Cosmochimica Acta |
Geoderma |
Geophysical Research Letters |
Global Change Biology |
Global Biogeochemical Cycles |
Groundwater |
Harmful Algae |
International Journal of Coal Geology |
Journal of Environmental Chemical Engineering |
Journal of Environmental Management |
Journal of Environmental Sciences |
Journal of Geophysical Research: Biogeosciences |
Journal of Geophysical Research: Oceans |
Journal of Hazardous Materials |
Journal of Membrane Science |
Journal of Soils and Sediments |
Land Degradation & Development |
Limnology and Oceanography |
Marine Chemistry |
Marine Pollution Bulletin |
Nature Communications |
Nature Geoscience |
Ocean Science Journal |
Oikos |
Organic Geochemistry |
Palaeogeography, Palaeoclimatology, Palaeoecology |
Plant and Soil |
Progress in Oceanography |
Quaternary International |
Science of The Total Environment |
Sedimentary Geology |
Separation and Purification Technology |
Soil and Tillage Research |
Soil Biology and Biochemistry |
Waste Management |
Water Research |
Water, Air, & Soil Pollution |
Wetlands |
...

所有论文

23501. 题目: Particle-scale visualization of the evolution of methanogens and methanotrophs and its correlation with CH4 emissions during manure aerobic composting
文章编号: N180625D5
期刊: Waste Management
作者: Jinyi Ge, Guangqun Huang, Junbao Li, Lujia Han
更新时间: 2018-06-25
摘要: Methane (CH4) emissions are a major environmental concern in composting facilities. Therefore, this study initially visualized the dynamic distribution and quantity of methanogens and methanotrophs in composting particles during manure aerobic composting using fluorescence in situ hybridization–confocal laser scanning microscopy (FISH–CLSM) and quantified their correlation with CH4 emissions. The visualization results showed that methanogens existed inside the particles, while methanotrophs clustered in the outer layer; a facultative anaerobic zone existed in between. The quantification results of integral optical density of methanogens and methanotrophs per unit particle area (U gen and U oxi, respectively) indicated that, in the cooling phase, CH4 generation and oxidation could still be high and could strike a balance if the initial organic matter content of composting materials is high, while both could be extremely low if the content is low. A strong linearity between U gen obtained by FISH–CLSM and methyl-coenzyme M reductase copy number obtained by quantitative polymerase chain reaction analysis (R 2 = 0.88) was observed, which justified the effectiveness of the FISH–CLSM method and demonstrated that macro-scale CH4 emissions were essentially an accumulation of particle-scale CH4 emissions. CH4 emissions were equal to 3.3297 × 107 U gen – 3.1814 × 106 U oxi – 3902.9900 (R 2 = 0.98). Overall, the results showed that methanogens exerted more influence on CH4 emissions than methanotrophs. Combining these results with CH4-generation and -oxidation kinetics may help illustrate CH4-emission mechanisms, improve particle-scale CH4-emission models, and thereby provide theoretical guidance for operation optimization and emission reduction in composting processes.

23502. 题目: Performance of a two-stage anaerobic digestion system treating fruit pulp waste: The impact of substrate shift and operational conditions
文章编号: N180625D4
期刊: Waste Management
作者: Mónica Carvalheira, Joana Cassidy, Jo?o M. Ribeiro, Bruno A. Oliveira, Elisabete B. Freitas, Christophe Roca, Gilda Carvalho, Adrian Oehmen, Maria A.M. Reis
更新时间: 2018-06-25
摘要: Food and beverage industry wastes present high amounts of organic matter, which may cause water quality degradation if not treated. Two-stage anaerobic digestion is a promising and efficient solution for the treatment of this type of wastes whilst producing bioenergy. The composition of fruit pulp waste varies throughout the different harvesting seasons, which may impact the process performance. In this study, a two-stage anaerobic digestion system was operated to assess the effect of substrate shift from peach to apple pulp wastes (obtained from a fruit juice company) on the microbial community activity and performance. During acidogenesis, the sugar conversion was higher than 95% for all operational conditions tested, obtaining a degree of acidification up to 89%. Principal Component Analysis was used to evaluate the relationship between the initial fermentation state of the residues in each operational condition and the obtained effluent. Methanogenic activity resulted in high organic carbon consumption (89%) and high methane productivities, achieving a maximum of 4.33 L C H 4 / L . d for peach waste influent. Overall, the results showed that the microbial community activity was not affected by the substrate shift, converting the sugars into biogas rich in methane (>70% CH4). Microbial analysis showed that the communities present in the acidogenic and methanogenic reactors were highly enriched in bacteria and archaea, respectively. The observed stability of the process, also demonstrated in pilot scale, confirmed the robustness of the process and thus, was suitable for implementation in companies producing seasonally different fruit wastes in a continuous operation.

23503. 题目: Biogeochemical dynamics and bioaccumulation processes in Manila clam: Implications for biodiversity and ecosystem services in the Ria de Aveiro Lagoon
文章编号: N180625D3
期刊: Estuarine, Coastal and Shelf Science
作者: Silvia Breda, Stefania Chiesa, Rosa Freitas, Etelvina Figueira, Francesca Becherini, Lorena Gobbo, Amadeu M.V.M. Soares, Emanuele Argese
更新时间: 2018-06-25
摘要: The present work was carried out in the Ria de Aveiro Lagoon (Portugal) to better understand the dynamics driving the bioaccumulation processes in edible bivalves, namely in the Manila clam Ruditapes philippinarum. For the first time, a holistic approach was applied, collecting data on sediment physico-chemical characteristics and its contamination, geochemical speciation and metal(loid) bioaccumulation in clams, from three exploited areas of the lagoon (Costa Nova, Torreira, lhavo). The Ria de Aveiro Lagoon is part of the Natura 2000 network, has the designation of Special Protection Area (SPA), contains Sites of Community Importance (SCI), it is protected by the EU Birds Directive (79/109/CEE) and includes a natural reserve in its northern part. Specifically concerning the metal(loid) occurrence, the monitoring and the identification of contaminated sites in protected areas are priorities, to improve the biodiversity conservation efforts and to ensure the correct management of natural resources. Results showed that multiple driving forces interacted together to determine site-specific impacts, resulting in different risks at local scale for the transferring of the metal(loid)s to the trophic chain. Hydrodynamics played a major role driving the occurrence of depositional or ablative sites, influencing the granulometric composition of sediments and their contamination; metal(loid) chemical forms were then determinated by multiple factors like pH, redox potential and organic matter content. The geochemical speciation data showed that the lhavo area should be considered the most dangerous in terms of clam consumption, since in case of environmental changes, possible conversion of the elements from the potentially bioavailable forms to the bioavailable ones can occur. Moreover, bioaccumulation processes in Manila clam were observed for Cd, Zn and especially As, the latter representing serious risk for consumer safety throughout clam consumption.

23504. 题目: Effects of Zostera marina rhizosphere and leaf detritus on the concentration and distribution of pore-water sulfide in marine sediments
文章编号: N180625D2
期刊: Estuarine, Coastal and Shelf Science
作者: Alexandra G. Simpson, Laura Tripp, David H. Shull, Sylvia Yang
更新时间: 2018-06-25
摘要: The relationship between seagrasses and pore-water hydrogen sulfide in the sediment is complex due to the opposing effects of the seagrass root system, which can reduce sulfide concentration by promoting its oxidation to sulfate, and the burial of organic matter from the plant itself, which can increase sulfide concentration by stimulating anaerobic sulfate reduction. Here, field samples of pore-water sulfide were collected in areas with and without Zostera marina shoots using Diffusive Gradients in Thin-Films (DGTs) to obtain two-dimensional visualizations of sulfide concentrations within the sediment in relation to location of eelgrass detritus and the rhizosphere. To decouple the effects of leaf detritus and the eelgrass rhizosphere on sulfide, manipulative laboratory studies were conducted over 4 weeks using 10 aquaria with or without eelgrass and different quantities of eelgrass detritus planted at 4 cm and 11 cm depths. Spatial distribution of pore-water sulfide was again measured via DGT. We found high spatial variation in pore-water sulfide concentration depending on the location analyzed relative to the rhizosphere or detritus. In the field study, pore-water sulfide concentration was greater in samples with eelgrass present, and the presence of leaf detritus accounted for higher than average sulfide concentrations in the sediment. In the laboratory experiment, sulfide concentrations localized around the leaf detritus increased with higher mass of added detritus, and sediment within the rhizosphere exhibited reduced sulfide concentrations. These results suggest that on the large scale the presence of eelgrass increases sulfide concentration, but on the smaller scale the pattern varies, with higher concentrations near buried detritus and lower concentrations near root tips.

23505. 题目: Long range transport and carbon and nitrogen dynamics of floating seagrass wracks in Greater Florida Bay
文章编号: N180625D1
期刊: Estuarine, Coastal and Shelf Science
作者: Rachel A. Perry, Jamie M.P. Vaudrey, Heidi M. Dierssen
更新时间: 2018-06-25
摘要: Floating aggregations of seagrass wrack can serve as an ecological “hot spot” contributing to the survival of many species in the form of habitat and food source. Considerable research has been conducted on seagrass wrack that is washed ashore, but here we demonstrate that large amounts of floating wrack produced in Greater Florida Bay can be advected great distances from their source, remain buoyant for weeks, and provide a nutrient subsidy into surrounding waters. Drifters tracking the location of floating Syringodium filiforme wracks revealed that movement of the wrack is strongly correlated to wind speed with total daily movement ranging from 10 to 40 km d 1. In mesocosm experiments, shedding followed an exponential model with highest rates estimated for loose aggregations of S. filiforme ( 0.124 d 1) compared to Thalassia testudinum (-0.047 d 1). Aggregated whorled S. filiforme wrack found offshore had an order of magnitude lower shedding with a rate of 0.013 d 1 suggesting it could remain buoyant for several months. Both wrack and the floating macroalgae Sargassum sp. released considerable amounts of dissolved organic carbon (DOC) and colored dissolved organic material (CDOM) daily into the dark mesocosm treatments. CDOM represented a constant proportion of the DOC exudate with a spectral slope suggestive of humic materials. Sargassum sp. produced twice as much DOC and CDOM compared to seagrass wrack. No net release of dissolved nitrogen was measurable in the treatments during the first 5 to 6 days while vegetation was photosynthetically viable, but particulate organic matter increased in the treatments consistent with the growth of bacterioplankton (C:N 7). Similar to Sargassum sp., seagrass wrack can be advected offshore and serve as a carbon and nitrogen source for organisms in oligotrophic waters.

23506. 题目: Mangrove carbon assessment tool: Model development and sensitivity analysis
文章编号: N180625D0
期刊: Estuarine, Coastal and Shelf Science
作者: Zhaohua Dai, Carl C. Trettin, Steve Frolking, Richard A. Birdsey
更新时间: 2018-06-25
摘要: It is important to have the capability to assess carbon (C) dynamics in mangrove forests and estimate their role in mitigating climate change because of their high carbon density, the threats to their integrity from land-use change and sea-level rise, and functional linkages of the many goods and services. A process-based model for mangroves was developed by integrating new features with existing biogeochemical processes in Forest-DNDC for simulating C sequestration and turnover in mangrove ecosystems. The new model is used to assess (1) the dynamics of C, nitrogen and phosphorous in mangrove ecosystems, including above-and below-ground C in saline wetlands, (2) the impacts of ecological drivers, including climate, soil nitrogen and phosphorous deficit and salt stress, on mangrove production, (3) the production of methane, and aerobic and anaerobic oxidation of methane with sulfate, nitrate and nitrite reductions, (4) the contributions of dissolved inorganic C (DIC), dissolved organic C (DOC), particulate organic C (POC) and burial C (BC) to blue C, and (5) impacts of natural and anthropogenic disturbances on C sequestration in mangrove ecosystems. Model sensitivity analysis showed that C sequestration in mangrove ecosystems was highly sensitive to multiple ecological factors, including climate, soil phosphorus, salinity and sulfate, as well as latitude. The responses of different C components to these factors were distinct. The responses of gross and net primary productivity and aboveground biomass to alterations of mean daily temperature (MDT) were quadratic, or increasing or decreasing non-linearly with an increment or decrement in MDT, but leaf production was linear. Similarly, other mangrove C components, such as BC, DIC, DOC and POC, respond substantially to variations of the ecological drivers. The combined effects of the driving factors are complex due to their intricate interactions. For example, while mangrove productivity is sensitive to available phosphorous, phosphorous cannot mitigate the stress imposed by high salinity. These results highlight the value of a tool to assess C dynamics in mangroves, especially for regional or large mangrove forests.

23507. 题目: River plume and bottom boundary layer – Hotspots for nitrification in a coastal bay?
文章编号: N180625C9
期刊: Estuarine, Coastal and Shelf Science
作者: Ines Bartl, Iris Liskow, Kirstin Schulz, Lars Umlauf, Maren Voss
更新时间: 2018-06-25
摘要: Coastal zones, impacted by major rivers, comprise distinct environments, such as river plumes and bottom boundary layers (BBL). These environments are characterized by high nutrient concentrations and high microbial activities and thus offer favourable conditions for nitrification, a key process in the coastal nitrogen cycle. Because nitrification provides substrates for both primary production and denitrification, elucidation of its magnitude and regulation is crucial for understanding the nitrogen cycle in coastal zones. During three research cruises covering three seasons, the enhancement of nitrification rates and their regulation by environmental variables, including salinity, temperature, oxygen, and inorganic and organic nitrogen were investigated in river plume and BBL of the Vistula Estuary (Bay of Gdansk, Southern Baltic Sea). Nitrification rates were not enhanced in the river plume (39 ± 38 nmol L 1 d 1) compared to coastal surface water (45 ± 18 nmol 1 d 1) but the relationship to salinity and particulate organic nitrogen changed, suggesting different regulatory mechanisms along the salinity gradient. Nitrification rates in the BBL covered a range from 1 to 227 nmol L 1 d 1 and did not differ seasonally. NH4 + turnover was dominated by assimilation into biomass in summer and by nitrification in winter and spring. In summer, rates were only slightly enhanced in the BBL and clearly related to particulate organic nitrogen and carbon concentrations, indicating particle attachment of nitrifiers and close coupling to organic matter degradation. The lack of correlations between nitrification and environmental variables in winter and spring suggested other regulatory mechanisms than in summer. Short-term changes, including the oxygenation of anoxic deep offshore water and particle resuspension clearly enhanced nitrification and further highlighted the variable mechanisms regulating nitrification in the Bay of Gdansk. Although nitrification rates did not greatly differ between seasons or water layers, the variability in regulatory mechanisms and the seasonal switch in NH4 + recycling are likely to have implications on coastal N-turnover and hence on the filter function of coastal waters.

23508. 题目: Geochemical characteristics of the extremely high thermal maturity transitional shale gas in the Southern North China Basin (SNCB) and its differences with marine shale gas
文章编号: N180625C8
期刊: International Journal of Coal Geology
作者: Yang Liu, Xuan Tang, Jinchuan Zhang, Xuanxue Mo, Huang Huang, Ziyi Liu
更新时间: 2018-06-25
摘要: A great number of studies have been carried out on the geochemical characteristics of marine shale gas from the lower Silurian Longmaxi Formation in the Sichuan Basin. However, a systematic study on geochemical and isotopic characteristics of transitional shale gas (gas from the alternating marine-terrigenous shale facies) has not been well addressed. In the present study, transitional shale gas from the lower Permian Shanxi (P1s) and Taiyuan (P1t) Formation in the Southern North China Basin (SNCB) were collected and analyzed for their geochemical and isotopic compositions. The hydrocarbon gases are dominated by methane, with small amounts of ethane, without propane and butane, which is consistent with the extremely high thermal maturity of the gas shales (RO% values between 3.2 and 4.2%). Compared with marine shale gas, the relatively high non-hydrocarbon components may be associated with the humic source rocks. The δ13C1 values range from 31.6‰ to 21.0‰ and the δ13C2 values range from 35.9‰ to 26.1‰, the δ2HCH4 values range from 221‰ to 138‰. These results indicate that the gases are of thermogenic origin, methane with anomalous heavy carbon isotopic and light hydrogen isotopic values was interpreted as redox reactions of gases with transition metals and water at maximum burial resulting in Rayleigh-type fractionation. The difficulties of identifying marine and transitional shale gas may be due to the complete or partial carbon isotopic reversal caused by secondary alteration and the extremely high thermal maturity of the gas shales. CO2 concentration and δ13C(CO2) values suggest that CO2 in the transitional shale gas was mainly thermogenic origin and formed together with hydrocarbon generation. Furthermore, significant differences can be observed from the CO2 in different types of shale gas, CO2 in the transitional shale gas is mainly distributed in areas with CO2 > 5% and δ13C(CO2) < 8‰, while CO2 in the marine shale gas is mainly distributed in areas with CO2 < 5% and δ13C(CO2) > 8‰. The δ15N(N2) values and high illite and illite-smectite mixed clay (I/S) content suggest that nitrogen in transitional shale gas was possibly generated during thermo-ammoniation of organic matter and/or the breakdown of NH4-rich clay minerals. In addition, based on the geochemical characteristics of marine and transitional shale gas, a geochemical pattern of shale gas is presented in this paper.

23509. 题目: Heterogeneity characterization of the lower Silurian Longmaxi marine shale in the Pengshui area, South China
文章编号: N180625C7
期刊: International Journal of Coal Geology
作者: Luchuan Zhang, Bo Li, Shu Jiang, Dianshi Xiao, Shuangfang Lu, Yuying Zhang, Cheng Gong, Lei Chen
更新时间: 2018-06-25
摘要: The heterogeneity of shale is significant for the evaluation and “sweet spot” prediction of a shale gas reservoir. Core observations, thin sections, field emission scanning electron microscopy (FE-SEM), nitrogen gas adsorption (N2GA) and geochemical analyses were performed on shale samples from the Lower Longmaxi Formation in the Pengshui area of South China. In this study, the macroscopic and microscopic heterogeneities of the Longmaxi shale are revealed, and their origins and inner link are also discussed. The results show that three systems tracts were developed in the Lower Longmaxi Formation: a transgressive systems tract (TST), early highstand systems tract (EHST) and late highstand systems tract (LHST). From TST to LHST, TOC (total organic carbon), siliceous minerals (quartz+feldspar), and pyrite show an upward decreasing trend in weight content, while the clay minerals and carbonate contents increase upward. Hence, the TST, EHST and LHST shales are generally characterized by organic-rich shale lithofacies, organic-moderate shale lithofacies, and organic-lean shale lithofacies, respectively. The in situ gas content decreases from TST to LHST and primarily depends on TOC content. The sedimentary environment of the TST shale is an anoxic environment with high paleoproductivity, which then evolves to a dysoxic-oxic environment in the EHST shale and an oxic environment in the LHST shale with relatively low paleoproductivity. Organic matter pores are the primary contributors to the total pore volume in the TST shale, and then, the pore content and role in porosity decrease upward from EHST to LHST. However, the proportions of clay-related pores and brittle mineral-related pores gradually elevate from the TST shale to the LHST shale. The sedimentary environment, including water depth, redox conditions, paleoproductivity, terrigenous input and hydrodynamics, etc., control the development of organic matter, mineral composition, lithofacies association, color, bedding and palaeobios in the Lower Longmaxi shales, which constitute the macroscopic heterogeneity. Nevertheless, the microscopic heterogeneity of shale originates from diagenesis/catagenesis. Specifically, shales are primarily composed of interparticle pores and clay-related pores during deposition, and the porosity is reduced primarily under mechanical compaction and chemical cementation. As the burial depth and diagenetic degree increase, a large number of organic matter pores and dissolution pores begin to appear, which are associated with the hydrocarbon generation process. Moreover, macroscopic shale composition plays a crucial role in development levels of microscopic shale pores.

23510. 题目: Improving coal bioavailability for biogenic methane production via hydrogen peroxide oxidation
文章编号: N180625C6
期刊: International Journal of Coal Geology
作者: Tianyu Chen, Sandra Rodrigues, Suzanne D. Golding, Victor Rudolph
更新时间: 2018-06-25
摘要: Hydrogen peroxide solution was used to pretreat coal samples for the purpose of improving bioavailability for methanogenesis. Crushed coals of subbituminous (PEN9-003) and medium-volatile-bituminous (C.D.) ranks were oxidized with three different dosages of H2O2 solution over four time periods (1, 4, 7, and 30 days) in the presence of UV light. Bioassays were set up using the oxidation products as the sole carbons substrates for biomethane production. To characterize the change in coal composition after oxidation, concentrations of volatile fatty acids (VFAs) and total organic carbon (TOC) in the filtered liquid sample of the pretreatment reactor were measured. The solid phase was dried and solvent-extracted with a mixture of dichloromethane and methanol. Compounds in the organic extract were analyzed using a GC–MS. H2O2 oxidation has managed to boost the biomethane yield in the subbituminous PEN9-003 coal by a maximum 10 times to 223.7 μmol/g. Production of methane was found to increase exponentially with the concentration of H2O2 relative to coal, but less significantly with pretreatment length. In contrast, the bituminous C.D. coal was barely affected by pretreatment. In addition, oxidation has considerably enhanced solubilization of PEN9-003 coal in water, with contents of VFAs and dissolved TOC surged by up to 28.2 and 22.3 times. The pretreatment has also increased the abundance of solvent-extractable matter in PEN9-003 coal. Oxygen-containing compounds, including aliphatic carboxylic acids, alcohols, ethers, ketones, and oxygenated monocyclic aliphatic and aromatic hydrocarbons were the most affected. The enrichment was due both to formation of new chemical species and an increase in the abundance of existing compounds. In comparison, oxidation of C.D. coal failed to generate any new organic species, nor did it increase the content of dissolved TOC. Biodegradation has resulted in depletion of all dissolved organic carbon, suggesting water-soluble compounds are highly bioavailable. Bioconversion of solvent-extractable matter in PEN9-003 has been improved by a maximum 29.5% upon pretreatment, while that of C.D. coal was lowered. Molecules with heterogeneous moieties, especially those that have been enriched after pretreatment demonstrated the highest bioavailability. Thermal maturation of coal from subbituminous to medium-volatile bituminous rank has been associated with a decrease in extractable matter contents, liptinite proportion, H/C ratio, elemental oxygen, heterogeneous moieties, as well as physical accessibility to microorganisms. They are thought to be responsible for the poor bioavailability and amenability of C.D. coal to H2O2 oxidation. Application of the pretreatment is only likely to be ex-situ, in which coal beneficiation waste may be used as a feed to bioreactors. The study offers a good basis for further process optimization and upscaling.

23511. 题目: Late gas generation potential for different types of shale source rocks: Implications from pyrolysis experiments
文章编号: N180625C5
期刊: International Journal of Coal Geology
作者: Haifeng Gai, Hui Tian, Xianming Xiao
更新时间: 2018-06-25
摘要: Gas generation from shale source rocks typically occurs via cracking of both kerogen and retained oils, such that it is difficult to predict and compare gas generation potentials of different shales because they are related not only to the kerogen type but also to the oil expulsion efficiency. In this study, five different shale kerogen samples were pyrolyzed in sealed gold tubes to investigate how kerogen type and oil expulsion efficiency affect their gas generation after oil-window maturity. The results illustrate that the maximum extractable organic matter (EOM) and gas generation potentials of different original shale kerogens (O-kerogen) in a closed system vary widely in the range of 229–790 mg/g TOCOK and 308–594 mL/g TOCOK, respectively. However, the gas yields of different residual shale kerogens (R-kerogen) with a starting equivalent vitrinite reflectance (EqVRo) value of approximately 1.22% are quite similar and vary between 131 and 145 mL/g TOCRK. Pyrolysis experiments also reveal that the late gas generation potential (EqVRo > 1.22%) of shale is mainly controlled by the amount of retained EOMs rather than kerogen type. When the shale source rocks containing types I and II kerogens have the same amount of retained EOMs, their gas generation potentials are quite similar. Under most geological conditions, the late gas generation potentials of shale source rocks, normalized to the TOC of matured shale at 1.22% EqVRo (TOCShale), vary approximately in the range of 180–300 mL/g TOCShale. To reach a gas content of 3 m3/ton shale for the present-day overmature shale gas exploration in the Lower Palaeozoic shales of South China, a conservative present-day TOC (TOCpd) value of 2.0% is proposed as a screening parameter that can eliminate the risk of insufficient gas generation potential as much as possible.

23512. 题目: On the petrographic distinction of bituminite from solid bitumen in immature to early mature source rocks
文章编号: N180625C4
期刊: International Journal of Coal Geology
作者: Paul C. Hackley, Brett J. Valentine, Javin J. Hatcherian
更新时间: 2018-06-25
摘要: The oil-prone maceral bituminite (and its equivalents: ‘amorphous organic matter’, ‘sapropelinite’, ‘amorphinite’, etc.) converts to petroleum during thermal maturation of source rocks, resulting in formation of a mobile saturate-rich hydrocarbon and a polar-rich residue of solid bitumen. Evidence of this transition is preserved in immature to early mature source rocks (e.g., Alum, Bakken, Kimmeridge, New Albany, Ohio shales, among many others), where organic petrography reveals a continuum of textures, reflectance, and fluorescence intensity occurring between bituminite and solid bitumen. Bituminite generally is characterized by high(er) intensity fluorescence, low contrast to the inorganic matrix, lower reflectance (compared to solid bitumen), and heterogeneous wispy or ‘schlieren’ textures. In comparison, solid bitumen generally shows lower intensity or no fluorescence compared to bituminite, a distinct contrast to the mineral matrix which usually includes a gray homogeneous surface of low to moderate reflectance, and may possess void-filling, embayment or groundmass textures suggesting evidence of migration or its in situ exsolution. However, these properties may manifest across a continuous spectrum in a sample or in a single microscope field, often making identification inconclusive. Unambiguous identification is further hampered by sample preparation, e.g., mechanical polish may improve homogeneity of larger accumulations, whereas smaller accumulations, or those sheltered by hard minerals, may appear more heterogeneous, leading to identification of the same organic matter as solid bitumen or bituminite, respectively. The disruptive innovation of ion milling in shale sample preparation leads to increased organic reflectance and surface homogeneity, causing bituminite and other oil-prone macerals, e.g., alginite, to develop a gray reflecting surface which is easy to confuse with solid bitumen, especially when obvious void-filling or embayment textures of the latter are absent. Herein we review distinction of solid bitumen from bituminite and alginite in immature to early mature source rocks, providing examples from nine samples illustrated by typical organic petrography images, including samples from hydrous pyrolysis experiments. Based on a review of the literature, we observe an arbitrary reflectance limit of 0.30% in mechanically polished samples seems to differentiate bituminite (<0.30%) from confident identifications of homogeneous solid bitumen (which otherwise lacks obvious void-filling or identifying embayment textures) as individual macerals on a continuous spectrum in immature and early mature source rocks. Future work conducted by governing bodies such as the International Committee for Coal and Organic Petrology (ICCP) should consider interlaboratory studies conducted on multiple immature source rock samples to develop consensus guidelines for bituminite and solid bitumen discrimination.

23513. 题目: Origin, properties, and implications of solid bitumen in source-rock reservoirs: A review
文章编号: N180625C3
期刊: International Journal of Coal Geology
作者: Maria Mastalerz, Agnieszka Drobniak, Artur B. Stankiewicz
更新时间: 2018-06-25
摘要: This paper reviews the significance of solid bitumen with emphasis on source-rock reservoirs. We discuss difficulties and discrepancies with terminology, especially those terms related to the origin of solid bitumen and its physical and chemical properties. Various definitions of solid bitumen have their own justifications and can be used provided there is clarity about which defining criteria are being considered. Difficulties in conforming to chemical-, solubility-, or origin-related definitions lead us to suggest adapting the reflectance of solid hydrocarbon as a practical choice for placing the boundary between solid bitumen and pyrobitumen, and 1.50% is proposed as the boundary value. It has to be noted that this boundary may be shifted down to 1.3% for sulfur-rich kerogen. Recently, much progress has been made by combining imaging and physical adsorption techniques in porosity studies, and so the porosity of solid bitumen is given special emphasis. Comparing pore characteristics obtained from SEM versus those generated by gas adsorption, mercury intrusion, or neutron scattering techniques indicates that the SEM pore inventory fails to account for the smallest pores (<5 nm in size) present in organic matter. Therefore, low-pressure CO2 adsorption is still the most effective technique to assess microporosity (pores <2 nm in diameter) in shales. We conclude that combining observational in situ techniques with techniques based on physical principles is necessary to make progress toward a better understanding of porosity systems in organic matter, including solid bitumen. We review the implications of the abundance of solid bitumen on reservoir quality, porosity, permeability, and producibility, based on examples of selected sequences. One of the difficulties in predicting the influence of solid-bitumen-bearing horizons on reservoir quality arises from the problems with detecting organic phases using various logging techniques. The use of specialized techniques such as NMR logging that allows two-dimensional T1 and T2 measurements should be expanded, and other potential techniques need to be further researched and tested. Certain aspects of the properties of solid bitumen that are not as well understood, such as its hydrocarbon generation potential or its role in hydrocarbon migration are also discussed with the aim of identifying further research that could lead to a better understanding of the role that solid bitumen plays in unconventional reservoirs.

23514. 题目: Paleoenvironmental reconstruction and hydrocarbon potentials of Upper Cretaceous sediments in the Anambra Basin, southeastern Nigeria
文章编号: N180625C2
期刊: International Journal of Coal Geology
作者: Olajide Femi Adebayo, Adebanji Kayode Adegoke, Khairul Azlan Mustapha, Mutiu Adesina Adeleye, Amos Okechukwu Agbaji, Nor Syazwani Zainal Abidin
更新时间: 2018-06-25
摘要: Palynological, organic petrographic, and organic geochemical analyses of the Campanian-Maastrichtian sediments in Akukwa-2 well were carried out to infer their paleoenvironments, origin of the organic matter, and hydrocarbon generation potentials. The TOC values of the analysed sediments range from 0.27–3.02 wt%, while the S2 pyrolysis yield range from 0.55 to 3.35 mg HC/g rock. This indicates that the Nkporo and Mamu sediments possess fair source generative potential. The samples contain Type III-II and Type III kerogen as shown by the present-day HI values between 58 and 292 mg HC/g TOC and pyrolysis-GC data. The organic matter within the sediments is also likely to generate mainly gas. This is in agreement with the petrographic observations, which revealed that the analysed shale samples contain abundant vitrinite macerals, apart from bituminite, alginite, cutinite, and resinite. Also, the sediments are immature to early mature in terms of hydrocarbon generation as indicated by vitrinite reflectance, biomarker maturity, and pyrolysis Tmax data. Biomarker distribution ratios, palynomorphs assemblage, and organic petrographic observations further point out that the organic materials within the sediments were of mixed aquatic and terrigenous origin and were deposited under suboxic paleodepositional conditions. Based on sedimentological, palynological, and biomarker characteristics, the environment of deposition of the analysed sediments was inferred to be a relatively quiet, shallow marine with fluvial incursion, most especially at the upper part of the intervals studied and consequently, it is a delta associated depositional environment with a fluviatile influence. The sediments are therefore suggested to be deposited in a paleogeographic setting close to vegetation source.

23515. 题目: Permeability anisotropy and gas slippage of shales from the Sichuan Basin in South China
文章编号: N180625C1
期刊: International Journal of Coal Geology
作者: Wen Zhang, Qin Wang
更新时间: 2018-06-25
摘要: Permeability anisotropy (A p ) and gas slippage of shales are critical for shale gas exploration, but laboratory measurements are still limited. We investigated composition, pore structure, permeability anisotropy and gas slippage of the Longmaxi and Wufeng shales from the Sichuan Basin in South China. The total organic carbon (TOC) content is positively related with the effective porosity and volume fraction of micropores, suggesting enhanced pore connectivity by organic matter. Dependence of permeability on the effective pressure (i.e., the confining pressure minus the pore pressure of N2) follows an exponential equation for five shale samples. At effective pressure of 6.9 MPa, our samples show very large A p variation from 1.2 to 1864.4. Compared with pore structure, clay content and the TOC content, microfractures significantly increase both permeability and A p of shales and play a predominant role in shale gas production. For shales with A p > 4, A p generally decreases with the increasing effective pressure due to the closure of oriented microcracks and slit-shaped macropores. At effective pressure of 6.9 MPa, the gas slippage is observed in four cores, with deviation from the Klinkenberg plot in three cores at high pore pressure. A new equation is proposed to describe the log trend of measured permeability with pore pressure. It allows us to quantify the deviation amount from the Klinkenberg plot and to constrain the pore pressure range where the effective stress law breaks down. In addition, the deviation from the Klinkenberg plot is more significant in shales with relatively high permeability and large pore width. The dominant transport regime in shales can change from the slip flow to the Darcy flow in fracture-bearing samples. The results indicate the important influence of permeability anisotropy and gas slippage of shales on final gas production and reservoir management.

23516. 题目: Petrographical and organic geochemical study of the lignite from the Smederevsko Pomoravlje field (Kostolac Basin, Serbia)
文章编号: N180625C0
期刊: International Journal of Coal Geology
作者: Nata?a ?okovi?, Danica Mitrovi?, Dragana ?ivoti?, Achim Bechtel, Reinhard F. Sachsenhofer, Vesna Mati?, Lidija Glamo?anin, Ksenija Stojanovi?
更新时间: 2018-06-25
摘要: Three Upper Miocene (Pontian) lignite seams are present in the Smederevsko Pomoravlje field (Kostolac Basin, Serbia). The origin of their organic matter (OM), the characteristics of the depositional environment and certain utilisation properties have been evaluated based on petrographic data, bulk organic geochemical parameters, biomarker patterns and their isotope signatures. Moreover, results of isotopic analysis were used for the investigation of the influence of diagenetic aromatisation on δ13C signatures of biomarkers. The studied lignites are typical humic coals. The OM of lignites is derived from woody vegetation and herbaceous peat-forming plants, with a strong prevalence of the former. The peat-forming vegetation is dominated by decay resistant conifers, including gymnosperm families Cupressaceae, Taxodiaceae, and Pinaceae. Angiosperms occurred in lower amounts. Minor contribution of ferns, fungi and emergent aquatic macrophyta to the biomass is also evident. Chemoautotrophic- and heterotrophic bacteria played an import role during diagenesis. Diagenetic alterations, associated with change in the number of carbon atoms, influence δ13C ratios. Diagenetic aromatisation of di- and non-hopanoid triterpenoids is accompanied with 13C depletion, whereas aromatisation of hopanoids displays the opposite trend. Peatification proceeded in a fresh water environment under variable, anoxic to slightly oxic redox conditions. The lowermost coal seam III accumulated in a topogenous fresh water peat mire with open water areas, which changed occasionally into a wet forest swamp. This resulted in the deposition of mineral-rich coal. The characteristics of lignite in coal seam II are similar to those of coal seam III. This is supported also by generally similar δ13C values of individual biomarkers. Coal seam I is dominated by xylite-rich coal, formed under mesotrophic to ombrotrophic conditions. Rapid flooding of the bogs stopped peat growth in all three coal seams. The ratios of ring-A-degraded and non-degraded aromatic diterpenoids and non-hopanoid triterpenoids, proposed in this study, as well as degree of aromatisation of these biomarkers, reflect changes in the water table. Calorific values of the samples indicate that they meet basic requirements for utilisation in the thermal power plants. None of the lignite samples is suitable for coal briquetting, whereas, based on petrographic data, lignite from coal seam I possesses certain potential for fluidized bed gasification.

23517. 题目: Revelation of organic matter sources and sedimentary environment characteristics for shale gas formation by petrographic analysis of middle Jurassic Dameigou formation, northern Qaidam Basin, China
文章编号: N180625B9
期刊: International Journal of Coal Geology
作者: Jing Qin, Shuangqing Wang, Hamed Sanei, Chunqing Jiang, Zhuoheng Chen, Shoumai Ren, Xuemin Xu, Jiajia Yang, Xiaotao Zhang
更新时间: 2018-06-25
摘要: The 7th member of Middle Jurassic Dameigou Formation (J2d7) in northern Qaidam Basin, China was proposed to have good hydrocarbon generating potential in previous studies. Here we apply an integrated petrographic and geochemical analysis to investigate the depositional environment, real thermal maturity and shale gas potential of organic-matter (OM)-rich assemblage. The relatively high content of C29 regular sterane (56.8%–62.8%) and vitrinite predominance in maceral composition suggesting plenty of higher-plant input, combined with the high pristane/phytane ratio (Pr/Ph)(2.8–8.2) and low gammacerane index (0.2–0.4) reveals oxic water column with in-situ depositional condition of carbonaceous-mudstone when the lower J2d7 was deposited. The maceral composition of oil shale at the upper part of J2d7 is mainly amorphous OM with small proportion of reworked vitrinite and inertinite, consistent with a mainly algea and small amount of exogenous OM input. When associated with low Pr/Ph (0.8) and high gammacerane index (4.3), the oil shale was deposited in an anoxic saline water column with mainly zooplankton OM source. The geochemical and petrographic result implies a transitional environment ranging from suboxic semi-saline to oxic fresh water environment with varying proportion of higher-plant and algae input by in-situ deposition and distant transportation for the mudstone at the middle part of J2d7. By use of random reflectance (Ro) distribution, two sedimentary environment microcycles which are confirmed by maceral composition, from the depth of 1983 m to 1962 m and 1954 m to 1931.9 m, are differentiated within the homogenous mudstone section. The variation of OM input condition and alternation of depositional environment led to accumulation and deposition of various kinds of abundant OM when J2d7 was deposited. Although the OM has actually low maturity at oil window with vitrinite reflectance around 0.6% according to the petrographic results, the liptinite inherited from higher-plants especially suberinite is the main maceral to generate gaseous hydrocarbons at the low maturity, which implies that the Dameigou formation (J2d7) of Qaidam Basin is of gas potential.

23518. 题目: Role of organo-clay composites in hydrocarbon generation of shale
文章编号: N180625B8
期刊: International Journal of Coal Geology
作者: Xiaojun Zhu, Jingong Cai, Guoli Wang, Mingshui Song
更新时间: 2018-06-25
摘要: Organic-mineral interactions are universal in natural environments. They cause the majority of the total organic carbon (TOC) in sediments and sedimentary rocks to combine with clay minerals to form organo-clay composites. However, the role of organo-clay composites in hydrocarbon generation is not clear. In this study, we select a suite of successively deposited shales to examine the association between organic matter (OM) and minerals, and to analyze the correlations of TOC with different mineral surface areas (MSAs) and the Rock-Eval pyrolysis in both bulk shales and their organo-clay composites. We find that OM in shale is dominantly incorporated with clay minerals by the main way of adsorbing on internal mineral surfaces rather than external mineral surfaces, which forms organo-clay composites. Further analyses on TOC-MSA correlations demonstrate the great heterogeneity of OM occurrence within shale. Also, the OM quality of organo-clay composites is poorer for hydrocarbon generation than that of bulk shales. We conclude that the variations in organic geochemistry between bulk shales and organo-clay composites are caused by hydrocarbon generation, which reduces the OM quality for further generation. Taken together, organo-clay composites dominate OM occurrence and have been generating hydrocarbons, which highlight the main control of organo-clay composites on hydrocarbon generation in natural samples. In comparison with the long-standing theory of hydrocarbon generated from kerogen, we propose the organo-clay composites to be the in situ and main source for hydrocarbon generation. This new hypothesis improves the existing knowledge of the organic origin of hydrocarbons in natural systems.

23519. 题目: The origin of pale and dark layers in Pliocene lignite deposits from Yunnan Province, Southwest China, based on coal petrological and organic geochemical analyses
文章编号: N180625B7
期刊: International Journal of Coal Geology
作者: Bangjun Liu, Cunliang Zhao, Jialiang Ma, Yuzhuang Sun, Wilhelm Püttmann
更新时间: 2018-06-25
摘要: A set of 39 pale lignite and dark lignite samples, obtained from a profile of the Pliocene Jinsuo lignite basin, Yunnan Province, China, were analyzed using coal petrology and biomarkers to determine whether changes in the depositional environment and/or vegetation caused the color changes ultimately observed in the lignites. A comprehensive analysis of all the data obtained revealed significant differences in the petrological and geochemical composition of the two lignite types. The pale lignites are characterized by a higher abundance of the liptinite group compared with the dark lignites. The composition of liptinites is dominated by bituminite (mineral-bituminous groundmass) and sporinite, along with a relatively low abundance of the huminite group. This indicates a higher degree of oxidation in the drier, more elevated peatland environments during deposition of the pale lignites. The low values of the tissue preservation index (TPI), vegetation index (VI), and gelification index (GI) in the pale lignites suggest a relatively high decomposition rate of plant materials under dry/aerobic conditions. In contrast, the dark lignites have a very high proportion of huminite dominated by ulminite, along with a low content of liptinite and inertinite macerals, which suggests the prevalence of wet/anaerobic conditions in the peat-forming mire. The high values of TPI, VI, and GI in the dark layers suggest better preservation of organic matter during deposition under anaerobic conditions, and more wet/humid climatic conditions, when compared with the pale lignites. With respect to the biomarker composition, the high concentrations of long-chain (C27-C31) n-alkanes in both pale and dark lignites are typical characteristics for the predominance of higher terrestrial plants. Significant concentrations of mid-chain n-alkanes (n-C21-C25) were detected preferentially in the dark lignites, suggesting that aquatic plants might also have contributed to the plant community during the formation of the dark layers. The content of diterpenoids, and the average ratio of diterpenoids to the sum of diterpenoids and triterpenoids (Di-/(Di- + Tri-terpenoids)) are higher in the pale lignites than in the dark lignites. This indicates that gymnosperms made a crucial contribution to the plant community during the formation of the pale lignites. In the dark lignites, triterpenoids are generally far more abundant than diterpenoids, which suggests that the dark layers were overwhelmingly formed by angiosperm plants. This is consistent with lower C/N ratios in the dark lignite layers (av. 40.8) compared with the pale lignite layers (av. 60.6). Higher microbial activities in the pale lignites than in the dark lignites are reflected by the higher concentration of hopanoids and 17α,21β-homohopane (22R) in the pale lignites.

23520. 题目: A 1500?year record of river discharge inferred from fluvial-marine sediments in the Australian subtropics
文章编号: N180625B6
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: J. Coates-Marnane, J. Olley, J. Tibby, J. Burton, D. Haynes, J. Kemp
更新时间: 2018-06-25
摘要: In Australia, there is a scarcity of high resolution hyrdoclimate reconstructions for the last several millennia. Fluvial-marine sediments offer a potential avenue for examining trends in freshwater input to coastal settings and, by inference, past hydroclimates. Here, major elemental geochemistry, δ13C and C:N ratios of organic matter, grain size and diatom species abundance, measured in a 4.4 m long sediment core collected from Moreton Bay, in east coast Australia, are used to infer the relative freshwater discharge of the adjacent catchment over the last ~1500 years. Reduced freshwater discharge into the Bay occurred from 630 to 1200 CE, especially between 1100 and 1200 CE. A broad increase in discharge is indicated after 1300 CE, extending to the present. The initial shift to the prolonged wet period coincides with both a decrease in the frequency of ‘dry’ El Ni o events based on regional records from the austral Pacific, and a broad hemispheric-scale cooling trend. This record provides further insight into low amplitude climate variability in the Australian subtropics over the last 1000 years, supporting efforts in both forecasting current and future climates, and managing regional water resources. Importantly, instrumental records do not cover the full range of natural climate variability experienced in the region over the last 1000 years.

 共 23819 条记录  本页 20 条  本页从 23501-23520 条  1176/1191页  首页 上一页  1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181  下一页  末页   

本数据库数据来源自各期刊,所有权归属各期刊。数据仅供分享学习,不作商业用途,特此申明。