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31.
32.
The importance of sulfur dioxide emissions for climate change is now established, although substantial uncertainties remain.
This paper presents projections for future sulfur dioxide emissions using the MiniCAM integrated assessment model. A new income-based
parameterization for future sulfur dioxide emissions controls is developed based on purchasing power parity (PPP) income estimates
and historical trends related to the implementation of sulfur emissions limitations. This parameterization is then used to
produce sulfur dioxide emissions trajectories for the set of scenarios developed for the Special Report on Emission Scenarios
(SRES). We use the SRES methodology to produce harmonized SRES scenarios using the latest version of the MiniCAM model. The
implications, and requirements, for integrated assessment modeling of sulfur dioxide emissions are discussed. We find that
sulfur emissions eventually decline over the next century under a wide set of assumptions. These emission reductions result
from a combination of emission controls, the adoption of advanced electric technologies, and a shift away from the direct
end use of coal with increasing income levels. Only under a scenario where incomes in developing regions increase slowly do
global emission levels remain at close to present levels over the next century. Under a climate policy that limits emissions
of carbon dioxide, sulfur dioxide emissions fall in a relatively narrow range. In most cases, the relative climatic effect
of sulfur dioxide emissions decreases dramatically to a point where sulfur dioxide is only a minor component of climate forcing
by the end of the century. Ecological effects of sulfur dioxide, however, could be significant in some developing regions
for many decades to come. 相似文献
33.
Solubility of Pt in sulphide mattes: Implications for the genesis of PGE-rich horizons in layered intrusions 总被引:1,自引:0,他引:1
Raúl O.C. Fonseca Ian H. Campbell Hugh St. C. ONeill Charlotte M. Allen 《Geochimica et cosmochimica acta》2009,73(19):5764-5777
The partitioning of Pt in sulphide melt (matte) has been studied as a function of fS2 and fO2 at 1200 and 1300 °C. The results show that the solubility of Pt in mattes increases strongly with increasing fS2 and decreases weakly with increasing fO2. The increase in Pt solubility with increasing fS2 is attributed to Pt dissolving in the melt as a sulphide species and the weak inverse dependence of Pt solubility on fO2 to the diluting effect of increasing O in the melt at high fO2. These results, coupled with measurements of Pt solubility in silicate melts taken from the literature, allow the calculation of Pt matte/silicate-melt partition coefficients () for a range of conditions pertinent to the formation of Pt-rich horizons in layered intrusions. The calculated values range between 107 and 1011, depending on fO2 and fS2, several orders of magnitude higher than previously published values. Our preferred value for for conditions appropriate to the Merensky Reef is 107 and for the Stillwater Pt-rich horizon 108. The new results are consistent with the magmatic hypothesis for Pt-rich horizons in layered intrusions. 相似文献
34.
This paper surveys coronal motions detected by the Yohkoh soft X-ray telescope SXT, emphasizing `global restructuring'. Large-scale structures in the solar corona can persist for
time scales much longer than those of the supergranulation, and may have larger spatial scales. Flares and coronal mass ejections
(CMEs) can disrupt these structures. A grazing-incidence telescope such as SXT provides a view of the corona biased in temperature
towards the hotter components, but in a thick `observing slice' (spatial contribution function). This helps in seeing excitation
(energy release) but may conceal some of the structural changes. The observations of restructuring largely appear to consist
of expanding or outwards magnetic motions, which are endoergic. This suggests a conjecture regarding the existence of magnetic implosions on scales not yet detected, as a source of free energy. 相似文献
35.
Hugh Kirkman 《Marine pollution bulletin》1999,37(8-12):460-467
The aim of this study was to investigate characteristics of some south-western Australian seagrasses that might be useful for further investigation with respect to restoration. Although seeds and fruits of seagrass species may be useful for producing propagules for planting, their collection is based on knowing when they become available. Posidonia australis, P. angustifolia and P. coriacea flower profusely annually, but P. sinuosa does not. Once collected, the fruits dehisce in a few days and are ready for planting. It was found that the best way to plant Posidonia seedlings is in clusters in Growool® blocks but the rhizomes do not spread quickly. Single Posidonia seedlings, when planted out, were not successful and neither were naturally colonizing seedlings of Posidonia sinuosa in unexposed unvegetated areas. Successful planting of seedlings and sprigs of Amphibolis in matting needs months of calm weather for them to spread out from their attaching matting which must be very securely attached to the substratum. Little success was achieved in growing Amphibolis. In a search for Halophila ovalis seeds, few were found because of the patchy nature of their fruiting and small size. Germination was slow but 63% germinated within 6 months. 相似文献
36.
Photometric Stability of the Lunar Surface 总被引:1,自引:0,他引:1
Hugh H. Kieffer 《Icarus》1997,130(2):323-327
The rate at which cratering events currently occur on the Moon is considered in light of their influence on the use of the Moon as a radiometric standard. The radiometric effect of small impact events is determined empirically from the study of Clementine images. Events that would change the integral brightness of the moon by 1% are expected once per 1.4 Gyr. Events that cause a 1% shift in one pixel for low Earth-orbiting instruments with a 1-km nadir field of view are expected approximately once each 43 Myr. Events discernible at 1% radiometric resolution with a 5 arc-sec telescope resolution correspond to crater diameters of approximately 210 m and are expected once every 200 years. These rates are uncertain by a factor of two. For a fixed illumination and observation geometry, the Moon can be considered photometrically stable to 1 × 10−8per annum for irradiance, and 1 × 10−7per annum for radiance at a resolution common for spacecraft imaging instruments, exceeding reasonable instrument goals by six orders of magnitude. 相似文献
37.
Sergio Colombo Mario Chica-Olmo Francisco Abarca Hugh Eva 《ISPRS Journal of Photogrammetry and Remote Sensing》2004,58(5-6):330-341
Tropical forest mapping is one of the major environmental concerns at global and regional scales in which remote sensing techniques are firmly involved. This study examines the use of the variogram function to analyse forest cover fragmentation at different image scales. Two main aspects are considered here: (1) analysis of the spatial variability structure of the forest cover observed at three different scales using fine, medium and coarse spatial resolution images; and (2) the study of the relationship between rescaled images from the finest spatial resolution and those of the medium and coarse spatial resolutions. Both aspects are analysed using the variogram function as a basic tool to calculate and interpret the spatial variability of the forest cover. An example is presented for a Brazilian tropical forest zone using satellite images of different spatial resolutions acquired by Landsat TM (30 m), Resurs MSU (160 m) and ERS ATSR (1000 m). The results of this study contribute to establishing a suitable spatial resolution of remotely sensed data for tropical forest cover monitoring. 相似文献
38.
The oxygen isotope geochemistry of igneous rocks 总被引:34,自引:0,他引:34
Hugh P. Taylor Jr. 《Contributions to Mineralogy and Petrology》1968,19(1):1-71
Oxygen isotope analyses have been obtained for 443 igneous rock and mineral samples from various localities throughout the world. Detailed studies were made on the Medicine Lake, Newberry, Lassen, Clear Lake, S. E. Guatemala, Hawaii and Easter I. volcanic complexes and on the Bushveld, Muskox, Kiglapait, Guadalupe, Duluth, Nain, Egersund, Lac St. Jean, Laramie, Skaergaard, Mull, Skye, Ardnamurchan and Alta, Utah plutonic complexes, as well as upon several of the zoned ultramafic intrusions of S. E. Alaska. Basalts, gabbros, syenites and andesites are very uniform in O18/O16, commonly with δ-values of 5.5 to 7.0 per mil. Many rhyolite obsidians, particularly those from oceanic areas and the Pacific Coast of the United States, also lie in this range; this indicates that such obsidians are differentiates of basaltic or andesitic magma at high temperatures (about 1,000° C). They cannot represent melted sialic crust. The only plutonic granites with such low δ-values are some of the hypersolvus variety, suggesting that these also might form by fractional crystallization. Obsidians from the continental interior, east of the quartz-diorite line, have higher δ-values. This is compatible with their having assimilated O18-rich sialic crust. A correlation generally exists between the O18/O16 ratios of SiO2-rich differentiates and the chemical trends in volcanic complexes. High O18/O16 ratios accompany those trends having the lower Fe/Mg ratios, while ferrogabbro trends are associated with depletion in O18. Variations in oxygen fugacity may be responsible for these effects, as abundant early precipitation of magnetite should lead to both O18-enrichment and Fe-depletion in later differentiates. Plutonic granites have higher O18/O16 ratios than their volcanic equivalents, because (a) their differentiation occurred at much lower temperatures, or (b) they are in large part derived from O18-rich sialic crust by partial melting or assimilation. Also, the oxygen isotope fractionations among coexisting minerals are distinctly larger in plutonic rocks than in volcanic rocks. This is in keeping with their lower crystallization temperatures and their longer cooling history, which promotes post-crystallization oxygen isotope exchange. Hydrated obsidians and perlites have δO18-values that are much different from their primary, magmatic values. A correlation exists between D/H and O18/O16 ratios in hydrated volcanic glass from the western U.S.A., proving that the isotopic compositions are a result of exchange with meteoric waters. The O18 contents of the glasses appear to be about 25 per mil higher than their associated waters; hence, these hydrated glasses have not simply absorbed H2O, but they have exchanged with large quantities of it. The igneous rocks from Mull, Skye, Ardnamurchan and the Skaergaard intrusion are all abnormally depleted in O18 relative to “normal” igneous rocks. This is a result of their having exchanged at high temperatures with meteoric water that was apparently abundant in the highly jointed plateau lavas into which these igneous rocks were intruded. In part, this exchange occurred with liquid magma and in part with the crystalline rock; in the latter case the feldspar was more easily exchanged and has become much more depleted in O18 than has coexisting quartz or pyroxene. The later differentiates of the Muskox intrusion are markedly O18-rich, but this is not a result of fractional crystallization. It is in large part a result of deuteric exchange between feldspars and an oxygen-bearing fluid (H2O ?) that was either O18-rich or had a relatively low temperature. This phenomenon was also observed in a number of granophyres from other localities, particularly those containing brick-red alkali feldspar. The exchanged feldspars in all these examples are turbid or cloudy, and may be filled with hematite dust. It is concluded that most such feldspar in nature is the result of deuteric exchange and is probably drastically out of oxygen isotopic equilibrium with its coexisting quartz. 相似文献
39.
Modelling particle residence times in agricultural river basins using a sediment budget model and fallout radionuclide tracers 总被引:1,自引:0,他引:1 下载免费PDF全文
Contemporary patterns in river basin sediment dynamics have been widely investigated but the timescales associated with current sediment delivery processes have received much less attention. Furthermore, no studies have quantified the effect of recent land use change on the residence or travel times of sediment transported through river basins. Such information is crucial for understanding contemporary river basin function and responses to natural and anthropogenic disturbances or management interventions. To address this need, we adopt a process‐based modelling approach to quantify changes in spatial patterns and residence times of suspended sediment in response to recent agricultural land cover change. The sediment budget model SedNet was coupled with a mass balance model of particle residence times based on atmospheric and fluvial fluxes of three fallout radionuclide tracers (7Be, excess 210Pb and 137Cs). Mean annual fluxes of suspended sediment were simulated in seven river basins (38–920 km2) in south‐west England for three land cover surveys (1990, 2000 and 2007). Suspended sediment flux increased across the basins from 0.5–15 to 1.4–37 kt y‐1 in response to increasing arable land area between consecutive surveys. The residence time model divided basins into slow (upper surface soil) and rapid (river channel and connected hillslope sediment source area) transport compartments. Estimated theoretical residence times in the slow compartment decreased from 13–48 to 5.6–14 ky with the increase in basin sediment exports. In contrast, the short residence times for the rapid compartment increased from 185–256 to 260–368 d as the modelled connected source area expanded with increasing sediment supply from more arable land. The increase in sediment residence time was considered to correspond to longer sediment travel distances linked to larger connected source areas. This novel coupled modelling approach provides unique insight into river basin responses to recent environmental change not otherwise available from conventional measurement techniques. © 2014 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd. 相似文献
40.
In this report, three different models in increasing order of complexity have been used to identify the seismic behaviour of a three-storey steel structure subjected to arbitrary forcing functions, all of which excite responses within the elastic range. All of the models are constructed using system identification. In the first model, five parameters have been used to identify the frame. Treating the system as a shear building, we assign one stiffness coefficient to each floor and introduce Rayleigh-type damping with two additional parameters. The mass, assumed to be concentrated at a floor level, is kept constant throughout the study. The parameters are established using a modified Gauss-Newton algorithm. The match between measured and predicted quantities is satisfactory when these quantities are restricted to floor accelerations or displacements. To remove the constraint imposed by assuming that the frame deforms as a shear building, a second model with eight parameters is introduced, allowing rotations of the joints as independent degrees of freedom. Six of the eight parameters are related to the stiffness characteristics of the structural members while the remaining two are related to damping as before. In constructing the eight-parameter model, we learned that it is the effective lengths of the members that change during optimization. We also found that the independent response quantities, floor accelerations and joint rotations, must be used in the cost function for the optimization algorithm to converge. The match between measured and predicted quantities for the eight-parameter model is excellent. The set of parameters derived from the minimum squared error gives a model that shows very good correlation using information on the full duration of the pulse or only a portion of it. Also the same correlation exists between the coefficients obtained from different excitations. In an effort to explain the values of the parameters associated with the girders, an additional degree of freedom, namely, the pitching motion of the shaking table, is introduced as an additional degree of freedom. The paper presents, therefore, a five-, an eight- and, finally, a nine-parameter model. 相似文献