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   

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   

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   

The interplanetary magnetic field environment at Mercury's orbit     

Haje Korth  Brian J. Anderson  Thomas H. Zurbuchen  James A. Slavin  Silvia Perri  Scott A. Boardsen  Daniel N. Baker  Sean C. Solomon  Ralph L. McNutt Jr. 《Planetary and Space Science》2011,59(15):2075-2085

Mercury is exposed to the most dynamic heliospheric space environment of any planet in the solar system. The magnetosphere is particularly sensitive to variations in the interplanetary magnetic field (IMF), which control the intensity and geometry of the magnetospheric current systems that are the dominant source of uncertainty in determinations of the internal planetary magnetic field structure. The Magnetometer on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft has made extensive magnetic field observations in the inner heliosphere over the heliocentric distances of Mercury's orbit, between 0.31 and 0.47 AU. In this paper, Magnetometer data from MESSENGER, obtained at rates of 2 and 20 vector samples per second, are used together with previous observations in the inner heliosphere by Helios and at Earth by the Advanced Composition Explorer, to study the characteristics of IMF variability at Mercury's orbit. Although the average IMF geometry and magnitude depend on heliocentric distance as predicted by Parker, the variability is large, comparable to the total field magnitude. Using models for the external current systems we evaluate the impact of the variability on the field near the planet and find that the large IMF fluctuations should produce variations of the magnetospheric field of up to 30% of the dipole field at 200 km altitude, corresponding to the planned periapsis of MESSENGER's orbit at Mercury. The IMF fluctuations in the frequency range are consistent with turbulence, whereas evidence for dissipation was observed for . The transition between the turbulent and dissipative regimes is indicated by a break in the power spectrum, and the frequency of this break point is proportional to the IMF magnitude.  相似文献   

The transition from complex crater to peak-ring basin on Mercury: New observations from MESSENGER flyby data and constraints on basin formation models     

David M.H. Baker  James W. Head  Samuel C. Schon  Carolyn M. Ernst  Louise M. Prockter  Scott L. Murchie  Brett W. Denevi  Sean C. Solomon  Robert G. Strom 《Planetary and Space Science》2011,59(15):1932-1948

The study of peak-ring basins and other impact crater morphologies transitional between complex craters and multi-ring basins is important to our understanding of the mechanisms for basin formation on the terrestrial planets. Mercury has the largest population, and the largest population per area, of peak-ring basins and protobasins in the inner solar system and thus provides important data for examining questions surrounding peak-ring basin formation. New flyby images from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft have more than doubled the area of Mercury viewed at close range, providing nearly complete global coverage of the planet's surface when combined with flyby data from Mariner 10. We use this new near-global dataset to compile a catalog of peak-ring basins and protobasins on Mercury, including measurements of the diameters of the basin rim crest, interior ring, and central peak (if present). Our catalog increases the population of peak-ring basins by ∼150% and protobasins by ∼100% over previous catalogs, including 44 newly identified peak-ring basins (total=74) and 17 newly identified protobasins (total=32). A newly defined transitional basin type, the ringed peak-cluster basin (total=9), is also described. The new basin catalog confirms that Mercury has the largest population of peak-ring basins of the terrestrial planets and also places the onset rim-crest diameter for peak-ring basins at , which is intermediate between the onset diameter for peak-ring basins on the Moon and those for the other terrestrial planets. The ratios of ring diameter to rim-crest diameter further emphasize that protobasins and peak-ring basins are parts of a continuum of basin morphologies relating to their processes of formation, in contrast to previous views that these forms are distinct. Comparisons of the predictions of peak-ring basin-formation models with the characteristics of the basin catalog for Mercury suggest that formation and modification of an interior melt cavity and nonlinear scaling of impact melt volume with crater diameter provide important controls on the development of peak rings. The relationship between impact-melt production and peak-ring formation is strengthened further by agreement between power laws fit to ratios of ring diameter to rim-crest diameter for peak-ring basins and protobasins and the power-law relation between the dimension of a melt cavity and the crater diameter. More detailed examination of Mercury's peak-ring basins awaits the planned insertion of the MESSENGER spacecraft into orbit about Mercury in 2011.  相似文献   

Observations of suprathermal electrons in Mercury's magnetosphere during the three MESSENGER flybys     

George C. Ho  Richard D. Starr  Robert E. Gold  Stamatios M. Krimigis  James A. Slavin  Daniel N. Baker  Brian J. Anderson  Ralph L. McNutt Jr.  Larry R. Nittler  Sean C. Solomon 《Planetary and Space Science》2011,59(15):2016-2025

In 2008 the MESSENGER spacecraft made the first direct observation of Mercury's magnetosphere in the more than 30 years since the Mariner 10 encounters. During MESSENGER's first flyby on 14 January 2008, the interplanetary magnetic field (IMF) was northward immediately prior to and following MESSENGER's equatorial passage through this small magnetosphere. The Energetic Particle Spectrometer (EPS), one of two sensors on the Energetic Particle and Plasma Spectrometer instrument that responds to electrons from ∼35 keV to 1 MeV and ions from ∼35 keV to 2.75 MeV, saw no increases in particle intensity above instrumental background (∼5 particles/cm²/sr/s/keV at 45 keV) at any time during the probe's magnetospheric passage. During MESSENGER's second flyby on 6 October 2008, there was a steady southward IMF, and intense reconnection was observed between the planet's magnetic field and the IMF. However, once again EPS did not observe bursts of energetic particles similar to those reported by Mariner 10 from its March 1974 encounter. On 29 September 2009, MESSENGER flew by Mercury for the third and final time before orbit insertion in March 2011. Although a spacecraft safe-hold event stopped science measurements prior to the outbound portion of the flyby, all instruments recorded full observations until a few minutes before the closest approach. In particular, the MESSENGER Magnetometer documented several substorm-like signatures of extreme loading of Mercury's magnetotail, but again EPS measured no energetic ions or electrons above instrument background during the inbound portion of the flyby. MESSENGER's X-Ray Spectrometer (XRS) nonetheless observed photons resulting from low-energy (∼10 keV) electrons impinging on its detectors during each of the three flybys. We infer that suprathermal plasma electrons below the EPS energy threshold caused the bremsstrahlung seen by XRS. In this paper, we summarize the energetic particle observations made by EPS and XRS during MESSENGER's three Mercury flybys, and we revisit the observations reported by Mariner 10 in the context of these new results.  相似文献