C 1s K-edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy for characterizing functional group chemistry of black carbon     

Karen Heymann  Johannes Lehmann  Dawit Solomon  Michael W.I. Schmidt  Thomas Regier 《Organic Geochemistry》2011,42(9):1055-1064

Black carbon (BC) is considered ubiquitous in soil organic matter (OM) and therefore plays an important role in soil biogeochemistry. Its complexity, particularly within environmental matrices, presents a challenge for research, primarily as a result of techniques which may favor detection of certain functional group types rather than capturing total sample C. The objective of this study was to utilize carbon (C) 1s near edge X-ray absorption fine edge structure (NEXAFS) spectroscopy to characterize the C chemistry of a broad range of BC materials. Characteristic resonances in the NEXAFS spectra allowed direct molecular speciation of the total C chemistry of the reference materials, environmental matrices and potentially interfering materials, obtained from an earlier BC ring trial. Spectral deconvolution was used to further identify the functional group distribution of the materials. BC reference materials and soils were characterized by a large aromatic C region comprising around 40% of total absorption intensity. We were able to distinguish shale and melanoidin from BC reference materials on the basis of their unique spectral characteristics. However, bituminous coal shared chemical characteristics with BC reference materials, namely high aromaticity of more than 40% identified by way of a broad peak. Lignite also shared similar spectra and functional group distributions to BC reference materials and bituminous coal. We compared the results of spectral deconvolution with the functional group distributions obtained by way of direct polarization magic angle spinning (DPMAS) ¹³C nuclear magnetic resonance (NMR) spectroscopy. Correlations between aromatic type C values for DPMAS ¹³C NMR and NEXAFS gave r² = 0.633 (p < 0.05) and the values for NEXAFS were around 30–40% lower than for ¹³C NMR. Correlations were also drawn between the aromatic C/O-alkyl C ratio values for the two methods (r² = 0.49, p < 0.05). Overall, NEXAFS was applicable for a wide range of environmental materials, such as those measured, although some limitations for the technique were addressed.  相似文献   

Delineation of recharge patterns and contaminant transport using 3H–3He in a shallow aquifer contaminated by chlorinated solvents in South Korea     

Dugin Kaown  Dong-Chan Koh  D. Kip Solomon  Yoon-Yeol Yoon  Jaeha Yang  Kang-Kun Lee 《Hydrogeology Journal》2014,22(5):1041-1054

Stable isotopes of water and ³H–³He were used to delineate recharge patterns and contaminant transport for a granitic regolith aquifer in an industrial complex in Wonju, South Korea, that has historically been contaminated with chlorinated solvents including trichloroethene (TCE) and carbon tetrachloride (CT). Groundwater recharge mainly occurred in upgradient forested areas while little recharge occurred in the downgradient industrial areas covered with extensive sections of impermeable pavement and paddy fields. δ¹⁸O and δD data indicated that groundwater was mainly derived from summer precipitation. The apparent groundwater ages using ³H–³He ranged from 1 to 4 yrs in the upgradient area and from 9 to 10 yrs in the downgradient area. Comparison of groundwater flow velocities based on Darcy’s law and those calculated with simple mass balance models and groundwater age supported the presence of preferential pathways for TCE movement in the study area. Measureable TCE was observed in groundwater irrespective of groundwater age. Considering the 3-yr duration of the TCE spill, 14 yrs before sampling, this indicates that TCE plumes were continuously fed from sources in the unsaturated zone after the spill ended and moved downgradient without significant degradation in the aquifer.  相似文献   

Evaluation of image analysis methods used for quantification of particle angularity     

Solomon Tafesse  Joanne M. Robison Fernlund  Wenjuan Sun  Fredrik Bergholm 《Sedimentology》2013,60(4):1100-1110

Angularity is an important parameter in the characterization of particle morphology that is used to interpret the transport history of particles in sedimentary deposits. In the past, visual classification using silhouette charts was widely used to determine particle angularity, but this approach is subjective and time‐consuming. With advances in modern image analysis techniques and low‐cost software packages, it is possible to rapidly quantify particle angularity more objectively than using visual classification methods. This study re‐examines the performance of three existing image analysis methods and one new image analysis procedure, applied to six rock and sediment samples that were visually different in angularity. To facilitate comparison between the angularity results, measurements were reduced to rankings for each aggregate sample. These results show that the four image analysis methods rank the angularity of the samples differently, and that none rank the mean angularity index in the same order as the angularity ranking using visual classification. Therefore, further research is needed to develop an image analysis method that can quantify the angularity of sedimentary particles more precisely.  相似文献   

Interstellar matter and star formation     

P.M. Solomon 《Astrophysics and Space Science》2003,285(2):481-495

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Separation of groundwater-flow components in a karstified aquifer using environmental tracers     

R. Nativ  G. Günay  H. Htzl  B. Reichert  D. K. Solomon  L. Tezcan 《Applied Geochemistry》1999,14(8):973

Groundwater discharges from the intensively karstified Taurus Mountains to the Mediterranean Sea, either along the contact zone between the mountains and the Travertine Plateau (the Kirkgozler Springs, 15 m³/s), or through the travertine (e.g. the Dudenbasi Spring, 18 m³/s) and underneath it (unnamed submarine springs, unknown discharges). In an attempt to identify the hydraulic connections between the various outlet points, groundwater was analyzed for stable and radioactive isotopes, CFCs and He. The upgradient springs, belonging to the Kirkgozler–Dudenbasi system, were proven to be a mixture of recent and older water on the basis of their low ¹⁴C values (12–22.4 pmc), their exceptionally high He content (429–991 μcc/kg) and ³He:⁴He (R:Ra) ratios (1.471–2.602) and their measurable ³H and CFC contents (1.9–5.9 TU and 0.84 to 3.27 pmoles/kg, respectively). The older component probably contains an even lower amount of modern C. However, the undersaturation of the mixture with respect to calcite, its high CO₂ content (up to 83 mg/L) and its enriched ¹³C values (−2.2 to −4.1‰) suggest intensive water/rock interactions, which would contribute ¹⁴C-devoid bicarbonates to the solution. Downgradient springs discharging along the Mediterranean coast contain groundwater contributions from higher altitudes, as evidenced by their depleted δ¹⁸O and δD composition with respect to the local precipitation; however, a larger portion of the recent water component could be contributed from direct precipitation on the travertine. This larger component is reflected in the increased ³H (3.4 to 8.4 TU) and ¹⁴C (32.7–63.6 pmc) contents, atmospheric He (43–82 pmoles/kg), R:Ra values (1.006–1.198) and CFC contamination of the water.  相似文献   

Fall and recovery of the Noblesville (Indiana,U.S.A.) H chondrite     

Michael E. Lipschutz  Brodie Spaulding  Brian D. Kinzie  Solomon Gartenhaus 《Meteoritics & planetary science》1993,28(2):240-242

Abstract We describe the circumstances of fall of a 0.5-kg meteorite that landed in Noblesville, Indiana, USA, 3.6 m in front of two witnesses on 1991 August 31. Provisional assessment of Noblesville as an H chondrite is confirmed by data reported elsewhere which demonstrate that it is a regolith breccia with unusual properties.  相似文献   

Transport of thermospheric NO to the upper stratosphere?     

Susan Solomon  Rolando R. Garcia 《Planetary and Space Science》1984,32(4):399-409

The rate of production of NO in the thermosphere is expected to vary greatly over the course of an 11-year solar cycle because the fluxes of both extreme ultraviolet radiation and auroral particles are known to increase substantially from solar minimum to solar maximum. In the stratosphere, NO participates in a catalytic cycle which constitutes the dominant photochemical destruction mechanism for stratospheric ozone. If appreciable long range transport of NO from the thermosphere to the upper stratosphere occurs, its effects should therefore be manifested in upper atmospheric ozone density variations over the 11-year solar cycle. In this paper, model predictions of the seasonal and latitudinal variations in upper stratospheric O₃ associated with NO transport for different levels of solar activity are compared to satellite observations of upper stratospheric ozone abundances.  相似文献   

The effect of carbon dioxide cooling on trends in the F2-layer ionosphere     

Liying Qian  Alan G. Burns  Stanley C. Solomon  Raymond G. Roble 《Journal of Atmospheric and Solar》2009,71(14-15):1592-1601

The effect of carbon dioxide (CO₂) cooling on trends of h_mF₂ and N_mF₂ are investigated using a coupled thermosphere and ionosphere general circulation model. Model simulations indicate that CO₂ cooling not only causes contraction of the upper atmosphere and changes of neutral and ion composition but also changes dynamics and electrodynamics in the thermosphere/ionosphere. These changes determine the altitude dependence of ionospheric trends and complex latitudinal, longitudinal, diurnal, seasonal, and solar cycle variations of trends of h_mF₂ and N_mF₂. Under the CO₂ cooling effect, trends of N_mF₂ are negative with magnitude from 0% to −40% for doubled CO₂, depending on location, local time, season, and solar activity. The corresponding trends of h_mF₂ are mostly negative with a magnitude from 0 to −40 km, but can be positive with a magnitude from 0 to 10 km at night, with maximum positive trends occurring after midnight under solar minimum conditions.  相似文献   

Spatiotemporal seismic hazard and risk assessment of M9.0 megathrust earthquake sequences of wood‐frame houses in Victoria,British Columbia,Canada     

Lizhong Zhang  Katsuichiro Goda  Maximilian J. Werner  Solomon Tesfamariam 《地震工程与结构动力学》2021,50(1):6-25

Megathrust earthquake sequences, comprising mainshocks and triggered aftershocks along the subduction interface and in the overriding crust, can impact multiple buildings and infrastructure in a city. The time between the mainshocks and aftershocks usually is too short to retrofit the structures; therefore, moderate‐size aftershocks can cause additional damage. To have a better understanding of the impact of aftershocks on city‐wide seismic risk assessment, a new simulation framework of spatiotemporal seismic hazard and risk assessment of future M9.0 sequences in the Cascadia subduction zone is developed. The simulation framework consists of an epidemic‐type aftershock sequence (ETAS) model, ground‐motion model, and state‐dependent seismic fragility model. The spatiotemporal ETAS model is modified to characterise aftershocks of large and anisotropic M9.0 mainshock ruptures. To account for damage accumulation of wood‐frame houses due to aftershocks in Victoria, British Columbia, Canada, state‐dependent fragility curves are implemented. The new simulation framework can be used for quasi‐real‐time aftershock hazard and risk assessments and city‐wide post‐event risk management.  相似文献   

Impacts of climate change on August stream discharge in the Central-Rocky Mountains     

Jason C. Leppi  Thomas H. DeLuca  Solomon W. Harrar  Steven W. Running 《Climatic change》2012,112(3-4):997-1014

In the snowmelt dominated hydrology of arid western US landscapes, late summer low streamflow is the most vulnerable period for aquatic ecosystem habitats and trout populations. This study analyzes mean August discharge at 153 streams throughout the Central Rocky Mountains of North America (CRMs) for changes in discharge from 1950–2008. The purpose of this study was to determine if: (1) Mean August stream discharge values have decreased over the last half-century; (2) Low discharge values are occurring more frequently; (3) Climatic variables are influencing August discharge trends. Here we use a strict selection process to characterize gauging stations based on amount of anthropogenic impact in order to identify heavily impacted rivers and understand the relationship between climatic variables and discharge trends. Using historic United States Geologic Survey discharge data, we analyzed data for trends of 40–59 years. Combining of these records along with aerial photos and water rights records we selected gauging stations based on the length and continuity of discharge records and categorized each based on the amount of diversion. Variables that could potentially influence discharge such as change in vegetation and Pacific Decadal Oscillation (PDO) were examined, but we found that that both did not significantly influence August discharge patterns. Our analyses indicate that non-regulated watersheds are experiencing substantial declines in stream discharge and we have found that 89% of all non-regulated stations exhibit a declining slope. Additionally our results here indicate a significant (α?≤?0.10) decline in discharge from 1951–2008 for the CRMs. Correlations results at our pristine sites show a negative relationship between air temperatures and discharge and these results coupled with increasing air temperature trends pose serious concern for aquatic ecosystems in CRMs.  相似文献