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81.
82.
The hillslope‐riparian‐stream system is a key functional unit of catchments, yet very difficult to measure and monitor due to its tremendous complexity and high spatio‐temporal variability. Here, we present a simple and practical tool for imaging directly these hillslope‐riparian‐area connections. We used a FLIR b50 infrared camera to produce thermal images at the scale of 140 × 140 pixels over the spectral range 7·5–13 µm. Our IR imaging technique is sensitive to the upper 0·1 mm of the water column. Images were obtained from a constant position on the right bank of the Weierbach catchment in Luxembourg, at an incidence angle of approximately 45° over a 5‐week period. The study site measured 5 × 3 m. Our results show that ground‐based IR imagery can discriminate between areas with snow cover, snow melt, soil seepage, and stream water. More importantly, it can detect when and where variably saturated areas are active and when connectivity exists between the hillslope–riparian–stream system. Our proof of concept suggests that this is a simple, inexpensive technology for sequential mapping and characterisation of surface saturated areas and a useful complement to conventional tracer techniques. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
83.
Ademar Michels Flávio Dias Mayer Roger Gallon Ronaldo Hoffmann Seimur Tiago Serafini 《洁净——土壤、空气、水》2008,36(9):743-747
The global warming and energy crisis is motivating the search for sustainable power sources. The objective of this work is to analyze the economic return and quantify the reduction in the emission of pollutants, when low‐cost solar collectors are used as a partial substitute for a boiler that uses fuel oil as the energy source, in order to heat water for the swimming pools of the Physical Education Center, Federal University of Santa Maria. The collectors are made from PVC and other easily acquired materials. The estimations for energy saving are based on a collecting area of 182 m2. From knowledge of the collectors' efficiency, the mathematical demonstration shows a fuel oil saving of 13,174 kg, representing 24% of the total amount consumed per annum. The investment required for the construction and installation of the collectors is US$ 6,445 and the estimated useful live is five years. The internal rate of return is 30%. The emission of pollutants is reduced by a considerable amount of 41,213 kg CO2 equivalent/year. The use of direct sun energy as an alternative power source represents a significant economic interest as well as contributing to the mitigation of greenhouse gases. 相似文献
84.
85.
Erin Jing Male William L. Pickles Eli A. Silver Gary D. Hoffmann Jennifer Lewicki Martha Apple Kevin Repasky Elizabeth A. Burton 《Environmental Earth Sciences》2010,60(2):251-261
Hyperspectral plant signatures can be used as a short-term, as well as long-term (100-year timescale) monitoring technique
to verify that CO2 sequestration fields have not been compromised. An influx of CO2 gas into the soil can stress vegetation, which causes changes in the visible to near-infrared reflectance spectral signature
of the vegetation. For 29 days, beginning on July 9, 2008, pure carbon dioxide gas was released through a 100-m long horizontal
injection well, at a flow rate of 300 kg day−1. Spectral signatures were recorded almost daily from an unmown patch of plants over the injection with a “FieldSpec Pro”
spectrometer by Analytical Spectral Devices, Inc. Measurements were taken both inside and outside of the CO2 leak zone to normalize observations for other environmental factors affecting the plants. Four to five days after the injection
began, stress was observed in the spectral signatures of plants within 1 m of the well. After approximately 10 days, moderate
to high amounts of stress were measured out to 2.5 m from the well. This spatial distribution corresponded to areas of high
CO2 flux from the injection. Airborne hyperspectral imagery, acquired by Resonon, Inc. of Bozeman, MT using their hyperspectral
camera, also showed the same pattern of plant stress. Spectral signatures of the plants were also compared to the CO2 concentrations in the soil, which indicated that the lower limit of soil CO2 needed to stress vegetation is between 4 and 8% by volume. 相似文献
86.
C. Aerts P. De Cat G. Handler U. Heiter L. A. Balona J. Krzesinski P. Mathias H. Lehmann I. Ilyin J. De Ridder S. Dreizler A. Bruch I. Traulsen A. Hoffmann D. James E. Romero-Colmenero T. Maas M. A. T. Groenewegen J. H. Telting K. Uytterhoeven C. Koen P. L. Cottrell J. Bentley D. J. Wright J. Cuypers 《Monthly notices of the Royal Astronomical Society》2004,347(2):463-470
87.
Among the terrestrial planets, Mercury is the smallest and has the highest bulk density. Mercury exhibits a lunar-like surface, shaped by impact basins and craters. Rapid cooling and contraction as well as tidal despinning have resulted in a large inventory of tectonic scarps and faults visible on the surface. With plans for new orbiter missions to this intriguing planet taking shape, this paper presents a summary of our current knowledge on Mercury's geology and cratering history. On the basis of improved data on asteroid populations and crater scaling, we updated the time stratigraphic sequence for the planet and made new estimates for the time of formation of impact basins such as Tolstoj and Caloris, which generally are now thought to be younger than in previous estimates. In order to advance our understanding of the geology of the planet, imaging experiments on future missions must fill the gap in the global coverage left by the Mariner spacecraft, and increase the global multispectral spatial resolution to at least 100 m/pixel. Locally, the image resolution must reach approx. 10 m/pixel. Also, stereo topographic models with global and local resolutions of 200 and 20 m, respectively, are required. 相似文献
88.
Kimmoun Olivier Hsu Hung-Chu Hoffmann Norbert Chabchoub Amin 《Ocean Dynamics》2021,71(11-12):1105-1112
Ocean Dynamics - We report an experimental study addressing the characteristic hydrodynamic transformations of unstable wave groups as well as JONSWAP wave fields propagating from deep-water... 相似文献
89.
Mechanisms of Archean crust formation inferred from high-precision HFSE systematics in TTGs 总被引:7,自引:0,他引:7
J. Elis Hoffmann Carsten Münker Minik T. Rosing Dieter Garbe-Schönberg 《Geochimica et cosmochimica acta》2011,75(15):4157-6628
It has been proposed that Archean tonalitic-trondhjemitic-granodioritic magmas (TTGs) formed by melting of mafic crust at high pressures. The residual mineralogy of the TTGs (either (garnet)-amphibolite or rutile-bearing eclogite) is believed to control the trace element budget of TTGs. In particular, ratios of high-field-strength elements (HFSE) can help to discriminate between the different residual lithologies. In order to place constraints on the source mineralogy of TTGs, we performed high-precision HFSE measurements by isotope dilution (Nb, Ta, Zr, Hf) together with Lu-Hf and Sm-Nd measurements on representative, ca. 3.85-2.8 Ga TTGs and related rock types from southern West Greenland, W-India and from the Superior Province. These measurements are complemented by major and trace element data for the TTGs. Texturally homogeneous early Archean (3.85-3.60 Ga old) and Mesoarchean (ca. 3.1-2.8 Ga old) TTGs have both low Ni (<11 ppm) and Cr contents (<20 ppm), indicating that there was little or no interaction with mantle peridotite during ascent. Ratios of Nb/Ta in juvenile Eoarchean TTGs range from ca. 7 to ca. 24, and in juvenile Mesoarchean TTGs from ca. 14 to ca. 27. Even higher Nb/Ta (14-42) were obtained for migmatitic TTGs and intra-crustal differentiates, most likely mirroring further fractionation of Nb from Ta as a consequence of partial melting, fluid infiltration and migmatisation. In the juvenile TTGs, positive correlations between Nb/Ta and Gd/Yb, La/Yb, Sr/Y, Zr/Sm and Zr/Nb are observed. These compositional arrays are best explained by melting of typical Isua tholeiites in both, the rutile-bearing eclogite stability field (>15 kbar, high Nb/Ta) and the garnet-amphibolite stability field (10-15 kbar, low Nb/Ta). With respect to the low end of Nb/Ta found for TTGs, there is currently some uncertainty between the available experimental datasets for amphibole. Independent of these uncertainties, the TTG compositions found here still require the presence of both endmember residues. A successful geological model for the TTGs therefore has to account for the co-occurrence of both low- and high-Nb/Ta TTGs within the same geologic terrane. An additional feature observed in the Eoarchean samples from Greenland is a systematic co-variation between Nb/Ta and initial εHf(t), which is best explained by a model where TTG-melting occured at progressively increasing pressures in a pile of tectonically thickened mafic crust. The elevated Nb/Ta in migmatitic TTGs and intra-crustal differentiates can shed further light on the role of intra-crustal differentiation processes in the global Nb/Ta cycle. Lower crustal melting processes at granulite facies conditions may generate high-Nb/Ta domains in the middle crust, whereas mid-crustal melting at amphibolite facies conditions may account for the low Nb/Ta generally observed in upper crustal rocks. 相似文献
90.
O. O. Sonibare O. B. Agbaje D. E. Jacob J. Faithfull T. Hoffmann S. F. Foley 《Australian Journal of Earth Sciences》2013,60(7):979-985
The terpenoid composition of fossil resin from the Cape York Peninsula, Australia has been analysed by pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) to determine its origin. The pyrolysis products were dominated by cadalene-based C15 bicyclic sesquiterpenoids including some C30–C31 bicadinanes and bicadinenes typical of Class II resin derived from angiosperm plants of Dipterocarpaceae. This observation contrasts with the Araucariaceae (Agathis sp.) source previously suggested for the resin based on Fourier transform infrared (FTIR) analyses. Dipterocarpaceae are not known in Australian vegetation but grow abundantly in Southeast Asia including New Guinea, indicating that the geological origin of the amber is not the Australian mainland but could be traced to Southeast Asia. 相似文献