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12801. 题目: Microbial decomposition processes and vulnerable arctic soil organic carbon in the 21st century
文章编号: N18092110
期刊: Biogeosciences
作者: Junrong Zha and Qianlai Zhuang
更新时间: 2018-09-21
摘要: Various levels of representations of biogeochemical processes in current biogeochemistry models contribute to a large uncertainty in carbon budget quantification. Here, we present an uncertainty analysis with a process-based biogeochemistry model, the Terrestrial Ecosystem Model (TEM), into which detailed microbial mechanisms were incorporated. Ensemble regional simulations with the new model (MIC-TEM) estimated that the carbon budget of the arctic ecosystems is 76.0±114.8PgC during the 20th century, i.e., −3.1±61.7PgC under the RCP 2.6 scenario and 94.7±46PgC under the RCP 8.5 scenario during the 21st century. Positive values indicate the regional carbon sink while negative values are a source to the atmosphere. Compared to the estimates using a simpler soil decomposition algorithm in TEM, the new model estimated that the arctic terrestrial ecosystems stored 12Pg less carbon over the 20th century, i.e., 19 and 30PgC less under the RCP 8.5 and RCP 2.6 scenarios, respectively, during the 21st century. When soil carbon within depths of 30, 100, and 300cm was considered as initial carbon in the 21st century simulations, the region was estimated to accumulate 65.4, 88.6, and 109.8PgC, respectively, under the RCP 8.5 scenario. In contrast, under the RCP 2.6 scenario, the region lost 0.7, 2.2, and 3PgC, respectively, to the atmosphere. We conclude that the future regional carbon budget evaluation largely depends on whether or not adequate microbial activities are represented in earth system models and on the sizes of soil carbon considered in model simulations.
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12802. 题目: Multiple sulphur isotope records tracking basinal and global processes in the 1.98 Ga Zaonega Formation, NW Russia
文章编号: N18092109
期刊: Chemical Geology
作者: K. Paiste, A. Lepland, A.L. Zerkle, K. Kirsimäe, G. Izon, N.K. Patel, F. McLean, T. Kreitsmann, K. Mänd, T.H. Bui, A.E. Romashkin, D.V. Rychanchik, A.R. Prave
更新时间: 2018-09-21
摘要: The exceptionally organic-rich rocks of the 1.98 Ga Zaonega Formation deposited in the Onega Basin, NW Russia, have refined our understanding of Earth System evolution during the Paleoproterozoic rise in atmospheric oxygen. These rocks were formed in vent- or seep-influenced settings contemporaneous with voluminous mafic volcanism and contain strongly 13C-depleted organic matter. Here we report new isotopic (δ34S, Δ33S, Δ36S, δ13Corg) and mineralogical, major element, total sulphur and organic carbon data for the upper part of the Zaonega Formation, which was deposited shortly after the termination of the Lomagundi-Jatuli positive carbon isotope excursion. The data were collected on a recently obtained 102 m drill-core section and show a δ13Corg shift from −38‰ to −25‰. Sedimentary sulphides have δ34S values typically between +15‰ and +25‰ reflecting closed-system sulphur isotope behaviour driven by high rates of microbial sulphate reduction, high sulphate demand, hydrothermal activity and hydrocarbon seepage. Four intervals record δ34S values that exceed +30‰. We interpret these unusually 34S-enriched sulphides to be a result of limited sulphate diffusion into pore waters due to changes in sedimentation and/or periods of basinal restriction. Additionally, there are four negative δ34S and positive Δ33S excursions that are interpreted to reflect changes in the open/closed-system behaviour of sulphate reduction or availability of reactive iron. Our findings highlight the influence of basinal processes in regulating sulphur isotope records and the need for care before interpreting such signals as reflecting global conditions.

12803. 题目: Soil physicochemical properties associated with quasi-circular vegetation patches in the Yellow River Delta, China
文章编号: N18092108
期刊: Geoderma
作者: Qingsheng Liu, Gaohuan Liu, Chong Huang, He Li
更新时间: 2018-09-21
摘要: In recent years, decreased runoff and sediment, intensified storm surge and seawater intrusion, urbanization, petroleum exploration, and production, and other factors have gradually deteriorated the unique wetland ecosystem in the Yellow River Delta (YRD). Although previous studies have analyzed the relationships between vegetation and soil properties at different scales, few studies have documented quasi-circular vegetation patches (QVPs) in the YRD, which appear to exhibit faster succession rates that make them ideal for studies on the relationships between vegetation and soil properties. Therefore, this study investigated differences in soil physicochemical properties at 0–20 cm depths between QVPs and inter-QVP bare soil areas, among QVPs, and among plant species communities. Additionally, spatial variations in soil physicochemical properties were explored in south-north and west-east transects across and within QVPs. The results showed that soils beneath QVPs had significant fertility island effects associated with soil organic matter (SOM) and total nitrogen (TN). Furthermore, these areas were richer in clay content, showed slightly higher pH values, and exhibited less available phosphorus (APH), available potassium (APO), total salt content, and silt content than those of bare soil areas. A multiple independent samples nonparametric Kruskal-Wallis H test detected significant differences in SOM, TN, APH, and pH among 18 QVPs, but no significant differences were found in APO, total salt content, sand, silt, and clay contents. Regardless of plant species, different plant species communities had significant effects on soil physicochemical properties. Particularly, soils underneath plant species communities with Tamarix chinensis were richer in SOM and TN, and they contained less APH, APO, and total salt content than those without T. chinensis. In each QVP, values of SOM and TN in soil samples along the patch perimeter were less than those of samples located midway toward the perimeter, and these values were less than those of samples centered in the patch. However, APO and total salt content values exhibited opposite changes from the perimeter to the center of the patch. The results also indicated significant differences in SOM, TN, APH, APO, and pH between south-north transect A and west-east transect B across QVPs, but no significant differences were found in total salt content, sand, silt, and clay contents. Therefore, the results of this study indicate that QVPs have significant effects on topsoil nutrients and salinity but little effects on soil texture. Furthermore, the occurrence and development of QVPs are associated with suitable soil conditions, including higher clay fractions and lower total salt content values.

12804. 题目: A concise review of biochar application to agricultural soils to improve soil conditions and fight pollution
文章编号: N18092107
期刊: Journal of Environmental Management
作者: Muhammad Shaaban, Lukas Van Zwieten, Saqib Bashir, Aneela Younas, Avelino Núñez-Delgado, Muhammad Afzal Chhajro, Kashif Ali Kubar, Umeed Ali, Muhammad Shoaib Rana, Mirza Abid Mehmood, Ronggui Hu
更新时间: 2018-09-21
摘要: Application of biochar to soil can play a significant role in the alteration of nutrients dynamics, soil contaminants as well as microbial functions. Therefore, strategic biochar application to soil may provide agronomic, environmental and economic benefits. Key environmental outcomes may include reduced availability of toxic metals and organic pollutants, reduced soil N losses and longer-term storage of carbon in soil. The use of biochar can certainly address key soil agronomic constraints to crop production including Al toxicity, low soil pH and may improve nutrient use efficiency. Biochar application has also demerits to soil properties and attention should be paid when using a specific biochar for a specific soil property improvement. This review provides a concise assessment and addresses impacts of biochar on soil properties.
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12805. 题目: Two novel decamethyl henicosanes (C31H64) identified in a Maoming Basin shale, China
文章编号: N18092106
期刊: Organic Geochemistry
作者: Jing Liao, Hong Lu, Qiao Feng, Youping Zhou, Quan Shi, Ping'an Peng, Guoying Sheng
更新时间: 2018-09-21
摘要: Two new C31 branched alkanes (botryococcanes) presumably produced by the B race of Botryococcus braunii were isolated and purified from the Maoming Basin shales using column chromatography and preparative gas chromatography and structurally characterized with HR-EI-MS and 1D and 2D NMR. Interpretation of their EI mass spectral and 1D and 2D NMR (HMBC and HSQC) data led to the firm assignments of the two alkanes as diastereoisomeric 2,3,6,7,10,12,15,16,19,20-decamethylhenicosanes (DMHs). The structural assignments were further confirmed by the close match of the measured 13C NMR chemical shifts with those predicted by Lindeman-Adams 13C chemical shift modeling. The skeletons of these two DMHs are virtually identical to that of the recently identified C33 botryococcane/botryococcanone in the same sample. It is proposed that these two DMHs share a precursor C33 botryococcene biochemically formed by condensing two farnesyl diphosphates involving an unusual cyclobutanation, a retro-Prins reaction and a tetramethylation. A photo-mediated geochemical oxidation of the double bond in the ethenyl group connected to the sole quaternary carbon C-10 is also proposed to be responsible for the formation of the co-occurring DMHs and C33 botryococcane/botryococcanone.

12806. 题目: Magnetic lignin-based carbon nanoparticles and the adsorption for removal of methyl orange
文章编号: N18092105
期刊: Colloids and Surfaces A: Physicochemical and Engineering Aspects
作者: Ying-zhi Ma, Da-feng Zheng, Zhen-ye Mo, Rui-jing Dong, Xue-qing Qiu
更新时间: 2018-09-21
摘要: In order to expand the application of lignin, magnetic lignin-based carbon nanoparticles (MLBCN) were synthesized using a precipitation-carbonization process and the structure was confirmed by FTIR, XRD, Raman, BET, SEM, DLS and VSM. The adsorption of MLBCN for methyl orange was consistent with the Langmuir model and pseudo-second-order model, showing monolayer adsorption, with a maximum adsorption capacity of 113.0 mg/g and chemisorption being the rate-controlling step. This process was exothermic and of entropy reduction, showing spontaneous below 35 °C. MLBCN could be used under near neutral conditions and easily regenerated. This study demonstrates that MLBCN is promising as an efficient, sustainable absorbent.
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12807. 题目: A mechanistic microbial underpinning for the size-reactivity continuum of dissolved organic carbon degradation
文章编号: N18092104
期刊: Marine Chemistry
作者: C. Arnosti, G. Reintjes, R. Amann
更新时间: 2018-09-21
摘要: The reservoir of dissolved organic carbon (DOC) in the ocean is modified by multiple input and removal processes. Incubation experiments as well as measurements of oceanic DOC have demonstrated that the high molecular weight (HMW) fraction of DOC typically has a younger radiocarbon age and is more reactive biologically than the low molecular weight (LMW) fraction of DOC. These observations have been summarized as a ‘size-reactivity continuum’ of DOC reactivity, but mechanistic explanations for these observations have been lacking. Here we describe how our recent discovery of ‘selfish’ HMW organic matter uptake among bacteria in surface ocean waters may help explain the rapid removal of HMW DOC. ‘Selfish’ substrate uptake by bacteria encompasses rapid binding and partial hydrolysis of intact polysaccharides on the outer membrane of bacteria, seamlessly followed by the transport of large oligosaccharide fragments into the periplasm with little to no loss of LMW hydrolysis products. ‘Selfish’ bacteria therefore process HMW substrates in a manner distinct from bacteria that carry out extracellular hydrolysis that yields LMW hydrolysis products in the environment. Recognition of the presence and prevalence of selfish bacteria in the ocean has profound implications for carbon flow – the source and quantity of LMW substrates made available to non-extracellular-enzyme producing bacteria – as well as for efforts to model and measure bacterial interactions during organic matter degradation. This discovery also highlights the importance of targeted substrate binding and uptake as key (often understudied) factors in geochemical investigations of microbially driven carbon cycling in the ocean. We conclude with some speculative thoughts about the factors that may determine the prevalence of selfish substrate uptake in the environment.
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12808. 题目: Sorption of Cu(II) by Al hydroxide organo–mineral coprecipitates: Microcalorimetry and NanoSIMS observations
文章编号: N18092103
期刊: Chemical Geology
作者: Huihui Du, Qiaoyun Huang, Min Zhou, Boqing Tie, Ming Lei, Xiangdong Wei, Xiaoli Liu, Yuan Yang
更新时间: 2018-09-21
摘要: The Al constituents of soils and sediments play an important role in the bioavailability and fate of trace heavy metals. Pure Al precipitates rarely exist; instead, Al3+ is commonly coprecipitated with organics to produce organo–Al hydroxide composites. Herein, we replicate the Al hydroxide organo−mineral composite formation in soils and sediments by synthesizing composites using humic acid (HA) during coprecipitation with Al hydroxide (Al(OH)3). The mineralogy and morphology results indicate the formation of amorphous and nanosized pure Al(OH)3 and Al(OH)3HA composites, while HA reduces the SSA and aggregation of the pure mineral. The sorption of Cu is enhanced on the Al(OH)3HA composite over pure Al(OH)3 at pH < 6, which is attributable to the additional binding sites present in the HA molecule. The isothermal titration calorimetry (ITC) results show that Cu sorption is endothermic on Al(OH)3 and exothermic on HA, and the sorption sequence is HA > Al(OH)3. The Cu uptake by the Al(OH)3HA composite is an energy-favorable process accomplished by an increase in entropy, signifying the formation of Cu-ligand inner-sphere complexes. Nano secondary ion mass spectrometry (NanoSIMS) results demonstrate that Cu is mainly sorbed on the HA fraction of the Al(OH)3–HA composite. This study therefore has important implications for predicting the cycling of trace heavy metals in Al-rich geologic environments, and sheds light on the combined use of ITC and NanoSIMS to uncover the distribution and speciation of trace elements in complex mineral–organic composites.
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12809. 题目: Complexation and reduction of iron by phenolic substances: Implications for transport of dissolved Fe from peatlands to aquatic ecosystems and global iron cycling
文章编号: N18092102
期刊: Chemical Geology
作者: Xiang Wan, Wu Xiang, Neng Wan, Sen Yan, Zhengyu Bao, Yiliu Wang
更新时间: 2018-09-21
摘要: Iron (Fe) is among the limiting nutrients in marine environments and mainly originates from terrigenous sources. Dissolved organic carbon (DOC), an important natural organic ligand, plays a key role in the dissolution and transport of terrestrial iron. Peat-derived DOC contains a large number of phenolics, and a systematic study of the geochemical interaction between DOC and Fe will contribute to the understanding of the global carbon and iron cycles. Phenolics, including phenolic acids, are secondary metabolites from plants and fungi. These compounds possess an aromatic ring bearing one or more hydroxyl groups and their structures may range from that of a simple phenolic molecule to that of a complex high-molecular weight polymer. Despite the extensive literature describing the biological effects of phenolic acids, the effect of phenolics on the iron cycle in peatlands is not known very well. Zoige peatland, the world's largest plateau peat wetland, was studied through field investigation and laboratory simulated experiments. The content of phenolics, filterable Fe and some physicochemical parameters in the rivers of the area were investigated. The waters are generally alkaline, with an average pH of 8.04, and aqueous Fe(III) and Fe(II) concentrations are higher than most of the common rivers in the world. The results of our experiments suggested that the high iron solubility was closely related to the phenolic content of the DOC. In particular, phenolics with catechol or galloy moieties forming complexes with iron and significantly impede the oxidation of complexed Fe(II). In addition, some phenolic substances are able to reduce ferric iron to ferrous iron. The combination of complexation and reduction in Fe by phenolics effectively increased the proportion of ferrous iron to total iron and slowed the oxidation and precipitation in the waters, maintaining a high content of “soluble iron” in the peatland. This mechanism has great implications for the effective transport of soluble iron from peatlands to aquatic ecosystems and the global coupled iron and carbon cycles.
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12810. 题目: Mechanistic insights into adsorption and reduction of hexavalent chromium from water using magnetic biochar composites: Key roles of Fe3O4 and persistent free radicals
文章编号: N18092101
期刊: Environmental Pollution
作者: Delai Zhong, Yanrong Zhang, Linling Wang, Jing Chen, Yi Jiang, Daniel C.W. Tsang, Zezhou Zhao, Shupeng Ren, Zhenhua Liu, John C. Crittenden
更新时间: 2018-09-21
摘要: Magnetic biochar (MBC) has been used to remove hexavalent chromium (Cr(VI)) from water, but the roles of Fe3O4 and persistent free radicals (PFRs) in MBC in Cr(VI) removal are still less investigated. In this work, the MBC synthesized by microwave co-pyrolysis of solid-state FeSO4 and rice husk was employed to remove Cr(VI) from water. In comparison to the rice husk biochar (BC), the MBC exhibits the 3.2- and 11.7-fold higher adsorption and reduction efficiency of Cr(VI), resulting in the higher Cr(VI) removal efficiency (84.3%) and equilibrium adsorption capacity of MBC (8.35 mg g−1) than that (26.5% and 2.63 mg g−1) of BC. Multiple characterization results revealed that the high Cr(VI) removal performance of MBC was mainly attributed to the presence of active Fe3O4 and carbon-centered PFRs in the porous and graphitic MBC. The Fe3O4 not only provided active chemisorption/reduction sites for Cr(VI) via its Fe(II)oct and Fe(III)oct coordination, but also facilitated the generation of more active electron donating carbon-centered PFRs than carbon-centered PFRs with an oxygen atom in the graphitic structure to reduce Cr(VI). The presence of Fe3O4 also elevated 36.7 m2 g−1 of BET-surface area and 0.043 cm2 g−1 of pore volume of MBC, promoting the Cr(VI) removal. The Fe3O4 and carbon-centered PFRs contributed to ∼81.8% and ∼18.2% of total Cr(III) generation, respectively. In addition, the initial solution pH was responsible for determining the relative significance of Cr(VI) adsorption and reduction. This study provides new insights into the mechanisms of Cr(VI) removal from water by the MBC.
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12811. 题目: Soil Na + concentration controls salt-affected soil organic matter components in Hetao region China
文章编号: N18092014
期刊: Journal of Soils and Sediments
作者: Xinliang Dong, Mozhi Li, Qimei Lin, Guitong Li, Xiaorong Zhao
更新时间: 2018-09-20
摘要: Purpose: There is little knowledge on the organic matter fractions of salt-affected soil aggregates. This study aimed at investigating characteristics of salt-affected soil organic carbon components and the relationships between soil salt concentration and soil organic carbon component content. Materials and methods: Five typical salt-affected soils in Hetao region China were collected and analyzed for light (LF) and heavy fraction (HF) in different water-stable aggregates. And the soil organic carbon components were measured by Fourier transform infrared (FTIR) and pyrolysis-gas chromatography/mass spectrometer (Py–GC/MS). Results and discussion: The results showed that the salt-affected soils were dominant in 53–10-μm water-stable aggregates, 61–80% in the bulk soil, and very low in > 250-μm macro-aggregates, less than 7.06% in the bulk soil. The proportions of > 250-μm macro-aggregates and the mean weight diameter (MWD) were negatively correlated to Na+ concentration (p < 0.05). Furthermore, the macro-aggregates were generally higher in total organic carbon (TOC) and accordingly higher C/N ratio than those in micro-aggregates. Heavy fractions (HF) from both > 53 μm and < 53-μm soil aggregates accounted for 99.30–99.83% of the bulk soil and contained 89.6–98.5% lower TOC and accordingly 49.2–84.8% lower C/N ratio than those in light fractions (LF). The LFs were high in lignin (7.27–34.02% in total pyrolysis products, 19.89% on average) and alkane/alkene-derived compounds (9.51–37.21%, 23.18% on average), but low in N-containing compounds (0–3.64%, 1.71% on average), while HFs were high in both alkane/alkene (4.38–27.46%, 15.06% on average) and N-containing compounds (7.45–26.45%, 13.98% on average), but low in lignin-derived compounds (1.13–8.75%, 3.86% on average). Conclusions: The tested salt-affected soils were predominant in 53–10-μm micro-aggregates, which was caused by the Na+ dispersion effect on soil aggregates. Most SOM was stored in HF that contained high N-containing compounds and low C/N ratios. Our results suggested that the components of SOM were mainly controlled by the soil Na+ concentration.

12812. 题目: Biodegradability of thermokarst carbon in a till‐associated, glacial margin landscape: the case of the Peel Plateau, NWT, Canada
文章编号: N18092013
期刊: Journal of Geophysical Research: Biogeosciences
作者: Cara A. Littlefair, Suzanne E. Tank
更新时间: 2018-09-20
摘要: The Peel Plateau is a characteristic glacial margin landscape, with permafrost comprised of thick, ice‐rich glacial tills deposited at the end of the Last Glacial Maximum. Unmodified tills at depth are overlain by a paleo‐active layer, created when early Holocene warming deepened regional active layers, enabling organic matter incorporation into now‐frozen soils. Ice‐rich permafrost encourages retrogressive thaw slumps (RTSs), which mobilize variable proportions of modern active layer, paleo‐active layer, and Pleistocene tills to downstream systems. Here, we investigate the biolability of thaw‐released dissolved organic carbon (DOC) on the Peel Plateau, and compare our results to previous studies from non‐till‐dominated landscapes. Similar to other Arctic regions, biolability was significantly greater for slump‐derived DOC (RTS runoff) than for DOC from paired, unimpacted locations. However, runoff source was an important control on biolability. Lability was greater for slumps releasing water with a Holocene‐like δ18O signature than for slumps with a more Pleistocene‐like signature, while a small slump, with runoff δ18O similar to the modern active layer, showed no biolability increase. Similar to other Arctic regions, biolability was strongly related to DOC aromaticity and molecular weight. However, lability also increased significantly with increasing nutrients, which has not been shown universally. Previous work has shown that DOC concentration dynamics differ sharply on the Peel Plateau when compared to other permafrost thaw landscapes. This work indicates that the lability of permafrost DOC may be relatively uniform across variable Arctic regions, although some factors – such as the importance of nutrient status – may need further exploration.

12813. 题目: Fe(II)-Catalyzed Transformation of Organic Matter–Ferrihydrite Coprecipitates: A Closer Look Using Fe Isotopes
文章编号: N18092012
期刊: Environmental Science & Technology
作者: Zhe Zhou, Drew E. Latta, Nadia Noor, Aaron Thompson, Thomas Borch, Michelle M. Scherer
更新时间: 2018-09-20
摘要: Ferrihydrite is a common Fe mineral in soils and sediments that rapidly transforms to secondary minerals in the presence of Fe(II). Both the rate and products of Fe(II)-catalyzed ferrihydrite transformation have been shown to be significantly influenced by natural organic matter (NOM). Here, we used enriched Fe isotope experiments and 57Fe Mössbauer spectroscopy to track the formation of secondary minerals, as well as electron transfer and Fe mixing between aqueous Fe(II) and ferrihydrite coprecipitated with several types of NOM. Ferrihydrite coprecipitated with humic acids transformed primarily to goethite after reaction with Fe(II). In contrast, ferrihydrite coprecipitated with fulvic acids and Suwannee River NOM (SRNOM) resulted in no measurable formation of secondary minerals. Despite no secondary mineral transformation, Mössbauer spectra indicated electron transfer still occurred between Fe(II) and ferrihydrite coprecipitated with fulvic acid and SRNOM. In addition, isotope tracer experiments revealed that a significant fraction of structural Fe in the ferrihydrite mixed with the aqueous phase Fe(II) (∼85%). After reaction with Fe(II), Mössbauer spectroscopy indicated some subtle changes in the crystallinity, particle size, or particle interactions in the coprecipitate. Our observations suggest that ferrihydrite coprecipitated with fulvic acid and SRNOM remains a highly dynamic phase even without ferrihydrite transformation.
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12814. 题目: Dissolved Carbon Dynamics in Meltwaters From the Russell Glacier, Greenland Ice Sheet
文章编号: N18092011
期刊: Journal of Geophysical Research: Biogeosciences
作者: M. Grace Andrews, Andrew D. Jacobson, Magdalena R. Osburn, Theodore M. Flynn
更新时间: 2018-09-20
摘要: Melting of the Greenland Ice Sheet (GrIS) has accelerated in recent decades. Given the close association between the water and carbon (C) cycles, melting of the GrIS may also drive local and global C cycle feedback. However, few studies have quantified such feedback, which may have important implications for predicting future climate or understanding linkages between ice sheet destabilization and climate change in the geologic past. Here we investigate seasonal and interannual dissolved C cycling at the margin of the Russell Glacier, west Greenland. By synthesizing isotopic analyses of water (δ18O) and C (δ13C and Δ14C) with geomicrobiological observations, we present evidence for previously unknown connections between the GrIS's supraglacial and subglacial dissolved C cycles. Supraglacial streams have variable concentrations of dissolved organic carbon (DOC) and are the dominant source of DOC in subglacial discharge. Supraglacial stream dissolved inorganic carbon (DIC) concentrations are uniform and sourced from a spatially and temporally constant mixture of organic C (~25%) respired by aerobic heterotrophs inhabiting the GrIS surface and dissolved atmospheric C (~75%). Supraglacial inputs account for ~50% of subglacial discharge DIC. The remaining subglacial DIC derives from carbonate weathering and microbial CO2 production, with the latter attributable to abundant anaerobic heterotrophic communities observed in subglacial discharge. Furthermore, we find that supraglacial streams deliver young DOC to the subglacial environment during snowmelt and rain events. These pulses of organic C may drive heterotrophic microbial respiration, with the cumulative effect being a seasonal shift in the source of basal DIC, from microbial‐ to carbonate‐dominated.

12815. 题目: The enigmatic structure of the crenarchaeol isomer
文章编号: N18092010
期刊: Organic Geochemistry
作者: Jaap S. Sinninghe Damsté, W. Irene C. Rijpstra, Ellen C. Hopmans, Mimi J. den Uijl, Johan W.H. Weijers, Stefan Schouten
更新时间: 2018-09-20
摘要: Isolation of crenarchaeol and its isomer from marine surface sediments, followed by ether cleavage and GC–MS characterization using supersonic molecular beam (SMB) ionization of the biphytanes formed, revealed that the crenarchaeol isomer comprises a tricyclic biphytane that is stereochemically different from the tricyclic biphytane of crenarchaeol. This isomeric tricyclic biphytane was also released from the crenarchaeol isomer in extant Thaumarchaeotal biomass. Reinterpretation of previously obtained 13C NMR data of the crenarchaeol isomer suggested that the cyclopentane moiety adjacent to the cyclohexyl moiety of the tricyclic biphytane of the crenarcheaol isomers possesses the unusual cis stereochemistry in comparison to the trans stereochemistry of all cyclopentane moieties in crenarchaeol. This stereochemical difference likely affects the packing of lipid membranes of Thaumarchaeota and therefore provides a biophysical explanation for the role of the crenarchaeol isomer in the TEX86 palaeothermometer based on fossilized Thaumarcheotal lipids.

12816. 题目: Linking the geochemistry of crude oils and petroleum inclusions in the Ubarana and Lorena oilfields, Potiguar Basin, Brazilian Equatorial Margin
文章编号: N18092009
期刊: Organic Geochemistry
作者: André Luiz Silva Pestilho, Lena Virgínia Soares Monteiro, Carlos Alberto Carbonezi, Sandra Brandão Jorge, Eugênio V. Santos Neto
更新时间: 2018-09-20
摘要: A study of petroleum inclusions based on ultraviolet fluorescence petrography, microspectrophotometry and biomarker analyses was carried out on samples from two wells of the onshore Lorena and the offshore Ubarana oilfields, Potiguar Basin, Brazil. This study aimed to evaluate the contribution and compositional variability of oils associated with different source rocks through the geochemical correlation of petroleum inclusions and crude oils. Three groups of inclusions were identified: (i) a group from the Lorena reservoir (Pendência Formation); (ii) a second from the Ubarana siliciclastic reservoir (Açu Formation); and (iii) a third from the carbonates adjacent to the Ubarana reservoir (Ponta do Mel Formation, PML). Fluorescence microspectrophotometry shows that the three groups of inclusions have different API gravity oils, variable proportion of saturate, aromatic, resins and asphaltenes and are not biodegraded. Moreover, Pendência and PML inclusions suggest multiple pulses of hydrocarbon migration, while Açu inclusions record a homogeneous pulse. Biomarkers indicate that the Pendência and Açu inclusion oils correlate with reservoir oil extracts. The Pendência inclusion oils are similar to the lacustrine oils of the Umbuzeiro graben (Pendência Formation), whereas the Açu inclusion oil displays closer biomarker signature to the Areia Branca trend of mixed oils (Alagamar Formation source rock). However, the oil from fluid inclusions of the PML has characteristics of the Alagamar Formation lacustrine organic facies. The absence of mixed oils in the PML suggests an earlier lacustrine oil migration through the carbonate fractures prior to the main infill of mixed oils in the Ubarana oilfield.

12817. 题目: Assessing biomarker syngeneity: An in situ approach using monoclonal antibodies
文章编号: N18092008
期刊: Organic Geochemistry
作者: Fernando Medina Ferrer, Jake V. Bailey, Frank Corsetti, J. Michael Moldowan, Silvana M. Barbanti, David Caron, Joe Bryant-Huppert
更新时间: 2018-09-20
摘要: Lipid biomarkers preserved in ancient rocks have the potential to reveal much about ancient ecosystems. However, establishing that the compounds of interest are syngenetic has proven to be an analytically challenging task. Traditional biomarker analyses rely on extraction of large quantities of powdered rock, making the association of molecules with sedimentary fabrics difficult, if not impossible. As an alternative approach, here we show that monoclonal antibodies that bind specifically to geolipids can be used as molecular probes for in situ detection and localization of such compounds. Monoclonal antibodies that bind to squalene and cross-react with the biomarker squalane were evaluated for labeling sediment-associated hydrocarbons. The anti-squalene antibodies were shown by dot immunoblotting with composed standards to cross-react also with other isoprenoids, such as phytol and its diagenetic products, suggesting reactivity towards acyclic isoprenoids. Then, the anti-squalene antibodies were shown to react with naturally occurring crude oils and, via an immunofluorescence-labeling approach, to bind to isolated organic-rich laminae in rocks from the Eocene Green River Formation known to contain squalane among other linear isoprenoids. These results suggest that squalane, or structurally similar organic biomarkers that cross-react with the antibodies, are confined to discrete organo-sedimentary fabrics within those rocks, providing evidence for their syngeneity. Depending on the specificity and sensitivity of the antibody/geolipid pair, an in situ antibody detection approach may be useful for establishing biomarker syngeneity in older rocks.

12818. 题目: Change in carbon flux (1960–2015) of the Red River (Vietnam)
文章编号: N18092007
期刊: Environmental Earth Sciences
作者: Thi Phuong Quynh Le, Nhu Da Le, Viet Nga Dao, Emma Rochelle-Newall, Thi Mai Huong Nguyen, Cyril Marchand, Thi Thuy Duong, Thi Xuan Binh Phung
更新时间: 2018-09-20
摘要: Global riverine carbon concentrations and fluxes have been impacted by climate and human-induced changes for many decades. This paper aims to reconstruct the longterm carbon concentrations and carbon fluxes of the Red River, a system under the coupled pressures of environmental change and human activity. Based on (1) the relationships between particulate and dissolved organic carbon (POC, DOC) or dissolved inorganic carbon (DIC), and suspended sediments (TSS) or river water discharge and on (2) the available detailed historical records of river discharge and TSS concentration, the variations of the Red River carbon concentration and flux were estimated for the period 1960–2015. The results show that total carbon flux of the Red River averaged 2555 ± 639 kton C year−1. DIC fluxes dominated total carbon fluxes, representing 64% of total, reflecting a strong weathering process from carbonate rocks in the upstream basin. Total carbon fluxes significantly decreased from 2816 kton C year−1 during the 1960s to 1372 kton C year−1 during the 2010s and showed clear seasonal and spatial variations. Organic carbon flux decreased in both quantity and proportion of the total carbon flux from 40.9% in 1960s to 14.9% in 2010s, reflecting the important impact of dam impoundment. DIC flux was also reduced over this period potentially as a consequence of carbonate precipitation in the irrigated, agricultural land and the reduction of the Red River water discharge toward the sea. These decreases in TSS and carbon fluxes are probably partially responsible for different negatives impacts observed in the coastal zone.

12819. 题目: In vitro cellular toxicity induced by extractable organic fractions of particles exhausted from urban combustion sources - Role of PAHs
文章编号: N18092006
期刊: Environmental Pollution
作者: Ekaterini Velali, Eleni Papachristou, Anastasia Pantazaki, Athanasios Besis, Constantini Samara, Christos Labrianidis, Theodore Lialiaris
更新时间: 2018-09-20
摘要: The bioactivity of the extractable organic matter (EOM) of particulate matter (PM) exhausted from major urban combustion sources, including residential heating installations (wood-burning fireplace and oil-fired boiler) and vehicular exhaust from gasoline and diesel cars), was investigated in vitro by employing multiple complementary cellular and bacterial assays. Cytotoxic responses were investigated by applying the MTT ((3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide)) bioassay and the lactate dehydrogenase (LDH) release bioassay on human lung cells (MRC-5). Sister Chromatids Exchange (SCE) genotoxicity was measured on human peripheral lymphocytes. Lipid peroxidation potential via reactive oxygen species (ROS) was evaluated on E. coli bacterial cells by measuring the malondialdehyde (MDA) end product. Furthermore, the DNA damage induced by the organic PM fractions was evaluated by the reporter (β-galactosidase) gene expression assay in the bacterial cells, and, by examining the fragmentation of chromosomal DNA on agarose gel electrophoresis. The correlations between the source PM-induced biological endpoints and the PM content in polycyclic aromatic hydrocarbons (PAHs), as typical molecular markers of combustion, were investigated. Fireplace wood smoke particles exhibited by far the highest content in total and carcinogenic PAHs followed by oil boilers, diesel and gasoline emissions. However, in all bioassays, the total EOM-induced toxicity, normalized to PM mass, was highest for diesel cars equipped with Diesel Particle Filter (DPF). No correlation between the toxicological endpoints and the PAHs content was observed suggesting that cytotoxicity and genotoxicity are probably driven by other extractable organic compounds than the commonly measured unsubstituted PAHs. Clearly, further research is needed to elucidate the role of PAHs in the biological effects induced by both, combustion emissions, and ambient air particles.
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12820. 题目: Environmental behavior and associated plant accumulation of silver nanoparticles in the presence of dissolved humic and fulvic acid
文章编号: N18092005
期刊: Environmental Pollution
作者: Yong Li, Haiyan Chen, Fei Wang, Furong Zhao, Xiaomin Han, Huanhuan Geng, Ling Gao, Huilun Chen, Rongfang Yuan, Jun Yao
更新时间: 2018-09-20
摘要: This work investigated the role of natural organic matter (NOM) in the environmental processes of silver nanoparticles (AgNP) and the uptake and accumulation of AgNP in wheat. Different NOMs (Suwannee River humic acids [SRHA], fulvic acid [FA]) and Ag elements (Ag(0) and Ag+) were incubated in a hydroponic media for 15 days. The results showed that the NOM (10 mg C L−1) altered the dissolution, stabilization, uptake and accumulation of AgNP. The dissolution of AgNP declined in the presence of NOM. Compared with FA, the dissolved Ag+ decreased much more from 0.30 mg L−1 to 0.10 mg L−1 in the presence of SRHA. The fluorescence quenching results indicated that SRHA exhibited stronger binding to Ag+ than that of FA, and the quenching constants Ksv were 0.1309 (SRHA) and 0.0074 (FA), respectively. C-O, C-H, C-O-C, and Me-OH were involved in the interaction between NOM and AgNP. The NOM decreased the accumulated content of Ag in wheat. Hence, NOM alleviated the inhibition of AgNP to wheat growth. SRHA reduced the Ag content of wheat roots approximately 3-fold. These results clearly indicated the importance of NOM on altering the behavior, fate and toxicity of AgNP in an environment.
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