Biogeochemistry of Ethanol and Acetaldehyde in Freshwater Sediments     

J. Alan RoebuckJr.  G. Brooks Avery  J. David Felix  Robert J. Kieber  Ralph N. Mead  Stephen A. Skrabal 《Aquatic Geochemistry》2016,22(3):177-195

This study reports the first ethanol and acetaldehyde measurements in sediment porewaters collected at multiple freshwater locations. Ethanol concentrations ranged from 11 to 2535 nM and acetaldehyde concentrations ranged from 6 to 320 nM. A significant positive correlation (p < 0.001) was observed between ethanol concentrations and the percent organic carbon content of sediments (TOC). Porewater depth profiles at two sites within the same lake indicated potential diffusion of ethanol into sediments from the overlying water at a lower TOC site and upwards diffusion from sediment into the water column at a higher TOC site. Diffusion of water column ethanol into sediments was observed at individual sites from October to January, whereas the opposite was true from June to August indicating the seasonal variability of ethanol flux from sediments. Changes in ethanol concentrations during a long-term sediment incubation experiment showed an inverse relation with acetaldehyde concentrations. The lack of a quantitative conversion was likely due to other sources and sinks that control their abundance. Our study provided new information on the biogeochemistry of ethanol in freshwater sediments and shed light on the potential role of ethanol in the global carbon cycle.  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987114001583   总被引：4，自引：3，他引：1  

Christopher J.Spencer  Peter A.Cawood  Chris J.Hawkesworth  Anthony R.Prave  Nick M.W.Roberts  Matthew S.A.Horstwood  Martin J.Whitehouse  EIMF 《地学前缘(英文版)》2015,6(3):357-372

Detrital zircons from modern sediments display an episodic temporal distribution of U-Pb crystallization ages forming a series of 'peaks' and 'troughs'.The peaks are interpreted to represent either periods of enhanced generation of granitic magma perhaps associated with mantle overturn and superplume events,or preferential preservation of continental crust during global collisional orogenesis.The close association of those peaks with the assembly of supercontinents implies a causal relationship between collisional orogenesis and the presence of zircon age peaks.Here these two end-member models(episodic periodicity of increased magmatism versus selective preservation during collisional orogenesis) are assessed using U-Pb,Hf,and O analysis of detrital zircons from sedimentary successions deposited during the ~ 1.3-1.1Ca accretionary.~1.1-0.9 Ga collisional,and 0.9 Ga extensional collapse phases of the Grenville orogenic cycle in Labrador and Scotland.The pre-collisional,accretionary stage provides a baseline of continental crust present prior to orogenesis and is dominated by Archean and Paleoproterozoic age peaks associated with pre-1300 Ma Laurentian geology.Strata deposited during the Grenville Orogeny display similar Archean and Paleoproterozoic detrital populations along with a series of broad muted peaks from~ 1500 to 1100 Ma.However,post-collisional sedimentary successions display a dominant age peak between 1085 and 985 Ma,similar to that observed in modern North American river sediments.Zircons within the post-orogenic sedimentary successions have progressively lower εHf and higherδ~(18)O values from ~ 1800 to ~ 1200 Ma whereupon they have higher εHf and δ~(18) within the dominant1085-985 Ma age peak.Furthermore,the Lu-Hf isotopic profile of the Grenville-related age peak is consistent with significant assimilation and contamination by older crustal material.The timing of this dominant age peak coincides with the peak of metamorphism and magmatism associated with the Crenville Orogeny,which is a typical collisional orogenic belt.The change from broad muted age peaks in the syn-orogenic strata to a single peak in the post-orogenic sedimentary successions and in the modern river sediments implies a significant shift in provenance following continental collision.This temporal change in provenance highlights that the source(s),from which detrital zircons within syn-orogenic strata were derived,was no longer available during the later stages of the accretionary and collisional stages of the orogenic cycle.This may reflect some combination of tectonic burial,erosion,or possibly recycling into the mantle by tectonic erosion of the source(s).During continental collision,the incorporated continental crust is isolated from crustal recycling processes operative at subduction margins.This tectonic isolation combined with sedimentaiy recycling likely controls the presence of the isotopic signature associated with the Grenville Orogeny in the modern Mississippi and Appalachian river sediments.These results imply that zircon age peaks,which developed in conjunction with supercontinents,are the product of selective crustal preservation resulting from collisional orogenesis.  相似文献   

Voronoi Meshing to Accurately Capture Geological Structure in Subsurface Simulations     

LaForce  Tara  Ebeida  Mohamed  Jordan  Spencer  Miller  Terry A.  Stauffer  Philip H.  Park  Heeho  Leone  Rosie  Hammond  Glenn 《Mathematical Geosciences》2023,55(2):129-161

Mathematical Geosciences - Mesh generation lies at the interface of geological modeling and reservoir simulation. Highly skewed or very small grid cells may be necessary to accurately capture the...  相似文献   

Rock avalanche on 14 July 2014 from Hillary Ridge,Aoraki/Mount Cook,New Zealand     

S. C. Cox  M. J. McSaveney  J. Spencer  S. K. Allen  S. Ashraf  G. T. Hancox  P. Sirguey  J. Salichon  B. G. Ferris 《Landslides》2015,12(2):395-402

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Herschel SPIRE FTS spectral mapping calibration     

Dominique Benielli  Edward Polehampton  Rosalind Hopwood  Ana Belén Griñón Marín  Trevor Fulton  Peter Imhof  Tanya Lim  Nanyao Lu  Gibion Makiwa  Nicola Marchili  David Naylor  Locke Spencer  Bruce Swinyard  Ivan Valtchanov  Matthijs van der Wiel 《Experimental Astronomy》2014,37(2):357-367

The Herschel SPIRE Fourier transform spectrometer (FTS) performs spectral imaging in the 447–1546 GHz band. It can observe in three spatial sampling modes: sparse mode, with a single pointing on sky, or intermediate or full modes with 1 and 1/2 beam spacing, respectively. In this paper, we investigate the uncertainty and repeatability for fully sampled FTS mapping observations. The repeatability is characterised using nine observations of the Orion Bar. Metrics are derived based on the ratio of the measured intensity in each observation compared to that in the combined spectral cube from all observations. The mean relative deviation is determined to be within 2 %, and the pixel-by-pixel scatter is ～ 7 %. The scatter increases towards the edges of the maps. The uncertainty in the frequency scale is also studied, and the spread in the line centre velocity across the maps is found to be ～ 15 km s ^{? 1}. Other causes of uncertainty are also discussed including the effect of pointing and the additive uncertainty in the continuum.  相似文献   

Titan: Interior,surface, atmosphere,and space environment,edited by I. Müller‐Wodarg,C. A. Griffith,E. Lellouch,and T. E. Cravens. Cambridge,UK: Cambridge University Press, 2014, 474 p. $135, hardcover (ISBN #978‐0521199926).     

Ralph D. Lorenz 《Meteoritics & planetary science》2014,49(6):1139-1140

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A photogrammetric surveying method for field applications     

Dirk H.  Rieke-Zapp  Ralph  Rosenbauer  Fritz  Schlunegger 《The Photogrammetric Record》2009,24(125):5-22

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William A. Cassidy (1928–2020)     

John Schutt  Ralph Harvey  Christian Koeberl 《Meteoritics & planetary science》2020,55(7):1709-1712

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Reflectance spectroscopy of insoluble organic matter (IOM) and carbonaceous meteorites     

Hannah H. Kaplan  Ralph E. Milliken  Conel M. O'D. Alexander  Christopher D. K. Herd 《Meteoritics & planetary science》2019,54(5):1051-1068

Insoluble organic matter (IOM) is the major organic component of chondritic meteorites and may be akin to organic materials from comets and interplanetary dust particles (IDPs). Reflectance spectra of IOM in the range 0.35–25 μm are presented as a tool for interpreting organic chemistry from remote measurements of asteroids, comets, IDPs, and other planetary bodies. Absorptions in the IOM spectra were strongly related to elemental H/C (atom) ratio. The aliphatic 3.4 μm absorption in IOM spectra increased linearly in strength with increasing H/C for H/C > 0.4, but was absent at lower H/C values. When meteorite spectra from the Reflectance Experiment Laboratory (RELAB) spectral catalog (n = 85) were reanalyzed at 3.4 μm, this detection limit (H/C > 0.4) persisted. Aromatic absorption features seen in IOM spectra were not observed in the meteorite spectra due to overlapping absorptions. However, the 3.4 μm aliphatic absorption strength for the bulk meteorites was correlated with both H/C of the meteorite's IOM and bulk C (wt%). Gaussian modeling of the 3 μm region provided an additional estimate of bulk C for the meteorites, along with bulk H (wt%), which is related to phyllosilicate abundance. These relationships lay the foundation for determining organic and phyllosilicate abundances from reflectance spectra. Both the full IOM spectra and the spectral parameters discussed here will aid in the interpretation of data from asteroid missions (e.g., OSIRIS‐REx, Hayabusa2), and may be able to place unknown spectral samples within the context of the meteorite collection.  相似文献   

三维正交非结构网格数值模型中物理流场的定义方法与改进     

刘晓辉  董礼先  Ralph T. Cheng 《海洋与湖沼》2010,41(4):621-627

使用Casulli等(2000)的数值方法建立了基于正交非结构网格的U型渠道的三维近岸正压水动力数值模型,检验了模型使用ELM(Eulerian-Lagrangian Method)方法处理平流项时,物理流场的定义对模拟结果的作用。数值试验和结果分析说明,使用ELM方法计算平流项所需的物理流场对计算结果影响明显,而目前常用的两种物理流场定义方法都存在一定不足——水位计算值对流速变化的反映不灵敏或者会产生小扰动等。针对常用物理流场定义方法的不足之处,作者在Casulli方法的基础上利用对多边形切向流速分量进行平均的方法改进了物理流场定义,抑制了小扰动。  相似文献