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971.
等离子体发射光谱法测定大气颗粒物中的无机元素 总被引:14,自引:4,他引:10
建立了用等离子体发射光谱(ICP-AES)测定大气颗粒物中无机元素的分析方法,包括样品消解体系的选择,仪器的操作条件及采样滤膜的选择,产对自行采样分析测得的无机元素数据作了初步的讨论。实验结果表明:采用HNO3-HClO4消解体系,操作方便,样品消解较完全;选用石英滤膜查减低空白值,保证测定质量以及同时在一张滤膜上测定大气颗粒物中的有机碳、元素碳及无机元素;内标法可有效降低由于仪器漂移等因素对测定 相似文献
972.
东北地区水文地质环境地质调查未来工作方向探讨 总被引:1,自引:0,他引:1
东北地区资源丰富,在为国家经济建设做出贡献的同时,自身地质环境也在不断变化.在简述东北地区区域水文、环境地质条件等自然地理概况的基础上,讨论了存在的水文地质、环境地质问题.认为未来在东北地区应加强战略性地下水资源的调查评价工作,提高全区研究程度,加强低山丘陵区地下水资源及其环境地质调查评价,在东北西部严重缺水的干旱-半干旱地区开展以解决生活用水、经济建设用水和生态环境建设用水的地下水勘查工作,加强东北中新生代盆地地热资源勘察工作,对地下水动态监测网格应加以补充、完善,加强城市地质调查工作,加强矿山环境地质工作,开展区域地质环境条件调查,建立地质环境监测工作的预报、预警系统. 相似文献
973.
974.
975.
Čermák Vladimír Šafanda Jan Krešl Milan Dědeček Petr Bodri Louise 《Studia Geophysica et Geodaetica》2000,44(3):430-441
Long-term (1961 – 1996) meteorological air temperature series together with the reconstructed ground surface temperature histories, obtained by inverting borehole temperature-depth profiles, were used to project regional patterns of the recent (climate) warming rate on the territory of the Czech Republic. The characteristic magnitude of the warming rate of 0.02 –0.03 K/yr was confirmed by the results of several years of monitoring the temperature in two experimental boreholes. The monitoring of shallow temperatures at depths of about 30 –40 m, i.e. below the reach of the seasonal surface temperature variations, can serve as an alternative tool of direct quantitative assessment of the present warming rate. The data also seem to sustain a potential man-made component contributing to the more pronounced recent warming rate observed in the areas of large agglomeration. 相似文献
976.
Catherine Schuur Duncan John A. Goff James A. AustinJr. Craig S. Fulthorpe 《Marine Geology》2000,170(3-4):395-421
Seafloor geomorphology and surficial stratigraphy of the New Jersey middle continental shelf provide a detailed record of sea-level change during the last advance and retreat of the Laurentide ice sheet (120 kyr B.P. to Present). A NW–SE-oriented corridor on the middle shelf between water depths of 40 m (the mid-shelf “paleo-shore”) and 100 m (the Franklin “paleo-shore”) encompasses 500 line-km of 2D Huntec boomer profiles (500–3500 Hz), an embedded 4.6 km2 3D volume, and a 490 km2 swath bathymetry map. We use these data to develop a relative stratigraphy. Core samples from published studies also provide some chronological and sedimentological constraints on the upper <5 m of the stratigraphic succession.The following stratigraphic units and surfaces occur (from bottom to top): (1) “R”, a high-amplitude reflection that separates sediment >46.5 kyr old (by AMS 14C dating) from overlying sediment wedges; (2) the outer shelf wedge, a marine unit up to 50 m thick that onlaps “R”; (3) “Channels”, a reflection sub-parallel to the seafloor that incises “R”, and appears as a dendritic system of channels in map view; (4) “Channels” fill, the upper portion of which is sampled and known to represent deepening-upward marine sediments 12.3 kyr in age; (5) the “T” horizon, a seismically discontinuous surface that caps “Channels” fill; (6) oblique ridge deposits, coarse-grained shelly units comprised of km-scale, shallow shelf bedforms; and (7) ribbon-floored swales, bathymetric depressions parallel to modern shelf currents that truncate the oblique ridges and cut into surficial deposits.We interpret this succession of features in light of a global eustatic sea-level curve and the consequent migration of the coastline across the middle shelf during the last 120 kyr. The morphology of the New Jersey middle shelf shows a discrete sequence of stratigraphic elements, and reflects the pulsed episodicity of the last sea-level cycle. “R” is a complicated marine/non-marine erosional surface formed during the last regression, while the outer shelf wedge represents a shelf wedge emplaced during a minor glacial retreat before maximum Wisconsin lowstand (i.e., marine oxygen isotope stage 3.1). “Channels” is a widespread fluvial subarial erosion surface formed at the late Wisconsin glacial maximum 22 kyr B.P. The shoreline migrated back across the mid-shelf corridor non-uniformly during the period represented by “Channels” fill. Oblique ridges are relict features on the New Jersey middle shelf, while the ribbon-floored swales represent modern shelf erosion. There is no systematic relationship between modern seafloor morphology and the very shallowly buried stratigraphic succession. 相似文献
977.
A. Gil de Paz A. Aragón-Salamanca J. Gallego A. Alonso-Herrero J. Zamorano G. Kauffmann 《Monthly notices of the Royal Astronomical Society》2000,316(2):357-373
We present new near-infrared J and K imaging data for 67 galaxies from the Universidad Complutense de Madrid (UCM) survey used in the determination of the SFR density of the local Universe by Gallego et al. This is a sample of local star-forming galaxies with redshift lower than 0.045, and they constitute a representative subsample of the galaxies in the complete UCM survey. From the new data, complemented with our own Gunn- r images and long-slit optical spectroscopy, we have measured integrated K -band luminosities, r − J and J − K colours, and H α luminosities and equivalent widths. Using a maximum likelihood estimator and a complete set of evolutionary synthesis models, these observations allow us to estimate the strength of the current (or most recent) burst of star formation, its age, the star formation rate and the total stellar mass of the galaxies. An average galaxy in the sample has a stellar mass of 5×1010 M⊙ and is undergoing (or has recently completed) a burst of star formation involving about 2 per cent of its total stellar mass. We identify two separate classes of star-forming galaxies in the UCM sample: low-luminosity, high-excitation galaxies (H ii like ) and relatively luminous spiral galaxies (starburst disc- like ). The former show higher specific star formation rates (SFRs per unit mass) and burst strengths, and lower stellar masses than the latter. With regard to their specific star formation rates, the UCM galaxies are intermediate objects between normal quiescent spirals and the most extreme H ii galaxies. 相似文献
978.
Maldonado Andrés Carlos Balanyá Juan Barnolas Antonio Galindo-Zaldívar Jesús Hernández Javier Jabaloy Antonio Livermore Roy Miguel Martínez-Martínez José Rodríguez-Fernández José Sanz de Galdeano Carlos Somoza Luis Suriñach Emma Viseras César 《Marine Geophysical Researches》2000,21(1-2):43-68
New swath bathymetric, multichannel seismic and magnetic data reveal the complexity of the intersection between the extinct West Scotia Ridge (WSR) and the Shackleton Fracture Zone (SFZ), a first-order NW-SE trending high-relief ridge cutting across the Drake Passage. The SFZ is composed of shallow, ridge segments and depressions, largely parallel to the fracture zone with an `en echelon' pattern in plan view. These features are bounded by tectonic lineaments, interpreted as faults. The axial valley of the spreading center intersects the fracture zone in a complex area of deformation, where N120° E lineaments and E–W faults anastomose on both sides of the intersection. The fracture zone developed within an extensional regime, which facilitated the formation of oceanic transverse ridges parallel to the fracture zone and depressions attributed to pull-apart basins, bounded by normal and strike-slip faults.On the multichannel seismic (MCS) profiles, the igneous crust is well stratified, with numerous discontinuous high-amplitude reflectors and many irregular diffractions at the top, and a thicker layer below. The latter has sparse and weak reflectors, although it locally contains strong, dipping reflections. A bright, slightly undulating reflector observed below the spreading center axial valley at about 0.75 s (twt) depth in the igneous crust is interpreted as an indication of the relict axial magma chamber. Deep, high-amplitude subhorizontal and slightly dipping reflections are observed between 1.8 and 3.2 s (twt) below sea floor, but are preferentially located at about 2.8–3.0 s (twt) depth. Where these reflections are more continuous they may represent the Mohorovicic seismic discontinuity. More locally, short (2–3 km long), very high-amplitude reflections observed at 3.6 and 4.3 s (twt) depth below sea floor are attributed to an interlayered upper mantle transition zone. The MCS profiles also show a pattern of regularly spaced, steep-inclined reflectors, which cut across layers 2 and 3 of the oceanic crust. These reflectors are attributed to deformation under a transpressional regime that developed along the SFZ, shortly after spreading ceased at the WSR. Magnetic anomalies 5 to 5 E may be confidently identified on the flanks of the WSR. Our spreading model assumes slow rates (ca. 10–20 mm/yr), with slight asymmetries favoring the southeastern flank between 5C and 5, and the northwestern flank between 5 and extinction. The spreading rate asymmetry means that accretion was slower during formation of the steeper, shallower, southeastern flank than of the northwestern flank. 相似文献
979.
The characteristics of the halo gas and its interaction with the galactic disk in spiral galaxies are poorly known; this is
particularly true for the warm neutral gas associated with HVCs and galactic chimneys. The detection of absorption features
such as the NaI D or the CaII (H,K)lines is instrumental to study its detailed physical properties but requires very long
integration times. In this work very deep optical spectra of NGC 604, the brightest giant HII region among the nearby spirals,
are presented. The detection of two absorption components at LSR velocities -255 km/s and −20 km/s respectively, is reported;
the first component is associated with the HII region. The inferred line width after deconvolution is 155 km/s; this large
width is produced by the blending of the multiple absorption components produced by the diverse sources of internal motion
(expanding shells and general turbulence). The radial velocity of the CaII absorption is slightly larger than the measured
in the HII emission lines suggesting a possible flow of gas into the halo above the young star cluster. The large ratio x = W
λ
(NaID_2)/W
λ
(CaIIK) = 0.7indicates the probable presence of shocks which release Ca from the dust grains into the gas phase. The lower velocity
component most likely trace galactic gas.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
980.
N. Huélamo M. Franqueira A. I. Gómez de Castro 《Monthly notices of the Royal Astronomical Society》2000,312(4):833-842
The far-UV spectrum of the T Tauri stars (TTSs) provides important clues about the structure of the stellar atmospheres, winds and accretion shocks. The IUE ( International Ultraviolet Explorer ) Final Archive contains the most complete data base for such studies. A new extraction system, the IUE Newly Extracted Spectra ( ines ), has been developed to overcome the disadvantages of the extraction system used in the IUE Final Archive, the Signal Weighted Extraction Technique ( swet ). We have compared the ines spectra of the whole sample of TTSs in the far-UV range (1200–2000 Å) with the swet low-resolution spectra available in the IUE Final Archive. Although in most of the cases there is a good agreement between both samples, an important enhancement of the ines line fluxes with respect to the swet line fluxes is reported for particular spectra. The line fluxes are enhanced by as much as a factor of ∼2.5 in some objects, which is significant for variability studies of TTSs because the variations of the UV lines are typically of this order. The emission-measure distributions built to study the atmospheres of these stars are based on the UV emission line fluxes, so the new system is susceptible to introduce changes in these models. Moreover, the non-linear enhancement of the ines line fluxes produces variations in diagnostic line ratios usually taken as temperature and density tracers in late-type stars. These line ratios can vary by as much as a factor of 3 when the ines data are compared with the swet , with the subsequent variation of the physical parameters derived from them. 相似文献