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111.
Katrin Fleischbein Wolfgang Wilcke Rainer Goller Jens Boy Carlos Valarezo Wolfgang Zech Klaus Knoblich 《水文研究》2005,19(7):1355-1371
Rainfall interception in forests is influenced by properties of the canopy that tend to vary over small distances. Our objectives were: (i) to determine the variables needed to model the interception loss of the canopy of a lower montane forest in south Ecuador, i.e. the storage capacity of the leaves S and of the trunks and branches St, and the fractions of direct throughfall p and stemflow pt; (ii) to assess the influence of canopy density and epiphyte coverage of trees on the interception of rainfall and subsequent evaporation losses. The study site was located on the eastern slope of the eastern cordillera in the south Ecuadorian Andes at 1900–2000 m above sea level. We monitored incident rainfall, throughfall, and stemflow between April 1998 and April 2001. In 2001, the leaf area index (LAI), inferred from light transmission, and epiphyte coverage was determined. The mean annual incident rainfall at three gauging stations ranged between 2319 and 2561 mm. The mean annual interception loss at five study transects in the forest varied between 591 and 1321 mm, i.e. between 25 and 52% of the incident rainfall. Mean S was estimated at 1·91 mm for relatively dry weeks with a regression model and at 2·46 mm for all weeks with the analytical Gash model; the respective estimates of mean St were 0·04 mm and 0·09 mm, of mean p were 0·42 and 0·63, and of mean pt were 0·003 and 0·012. The LAI ranged from 5·19 to 9·32. Epiphytes, mostly bryophytes, covered up to 80% of the trunk and branch surfaces. The fraction of direct throughfall p and the LAI correlated significantly with interception loss (Pearson's correlation coefficient r = −0·77 and 0·35 respectively, n = 40). Bryophyte and lichen coverage tended to decrease St and vascular epiphytes tended to increase it, although there was no significant correlation between epiphyte coverage and interception loss. Our results demonstrate that canopy density influences interception loss but only explains part of the total variation in interception loss. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
112.
113.
Characterization of sediments in an abandoned mining area; a case study of Mansfeld region,Germany 总被引:1,自引:0,他引:1
Rainer?WennrichEmail author Jürgen?Mattusch Peter?Morgenstern Klaus?Freyer Hanns-Christian?Treutler Hans-Joachim?St?rk Lutz?Brüggemann Albrecht?Paschke Birgit?Daus Holger?Weiss 《Environmental Geology》2004,45(6):818-833
The distribution of selected heavy metals, including some radionuclides, metalloids and non-metals was determined in stream sediments in a region influenced by abandoned copper mining and ore processing activities. A considerable amount of the ore processing waste with a very complex composition and highly elevated concentrations of zinc, sulfur, lead, copper, arsenic, and a lot of other elements in the range between 100 and 1,000 mg/kg (Sb, Mn, Ni, Cr, Cd, Hg, and Ag) was piled up on mine dumps. The dispersion of the pollutants originating from this source and their environmental impact were investigated. Both, sediments and original waste material were studied to indicate the pathways and the mobilization behavior of different pollutants. For this purpose, the process of the elution of pollutants by application of different fractionation schemes was studied. The capabilities of different analytical techniques are shown for the analysis of solid samples (X-ray fluorescence spectrometry, Gamma-spectrometry) and liquid ones (ICP-atomic emission spectrometry, ICP-mass spectrometry and different techniques of atomic absorption). Additionally, the coupling of ion chromatography and ICP-MS detection was used to study the distribution of arsenic species in the sediment cores of a lake which acts as a natural sink for the region. 相似文献
114.
LIU Qiyuan Rainer Kind CHEN Jiuhui YUAN Xiaohui LI Shuncheng GUO Biao Kurt Wylegalla & LAI Yuangen . State Key Laboratory of Earthquake Dynamics Institute of Geology China Earthquake Administration Beijing China . GeoForschungZentrum Potsdam Telegrafenburg A Potsdam D- Germany 《中国科学D辑(英文版)》2005,48(7)
The Dabie Shan is located on the eastern side of the Qinling-Dabie orogenic belt, which marks a geological boundary between the Sino-Korean and Yangtze cra- ton. Since the 1980s, the discovery of coesite and mi- crodiamond in the Dabie Shan orogen motivates an extensive interest to the ultra-high pressure (UHP)metamorphism and its exhumation[1,2]. Many results about them were published, which deal with different disciplines, including tectonics, petrology and chro- nology[3?8]. Up to now,… 相似文献
115.
Responses of a multifrequency, multicoil airborne electromagnetic (AEM) system were modelled numerically for 3D electrical conductors embedded in a resistive bedrock and overlain by an overburden of low to moderate conductivity. The results cover a horizontal coplanar coil configuration and two frequencies, 7837 Hz and 51 250 Hz. The models studied are single or multiple, poor conductors (conductance lower than 0.1 S) embedded in a host rock of high but finite resistivity (5000 Ωm) and overlain by a layer of overburden with finite thickness and low to moderate conductivity (conductance up to 2 S). On the basis of the modelling results, limits of detectability for poor conductors have been studied for the various model structures. The results indicate that the anomaly from a steeply dipping, plate-like conductor will decrease significantly when the conductor is embedded in a weakly conductive host rock and is overlain by a conductive overburden. However, an anomaly is obtained, and its magnitude can even increase with increasing overburden conductivity or frequency. The plate anomaly remains practically constant when only the overburden thickness is varied. Changes in overburden conductivity will cause the plate-anomaly values to change markedly. If the plate conductance is less than that of the overburden, a local anomaly opposite in sign to the normal type of anomaly will be recorded. Another major consequence is that conductors interpreted with free-space models will be heavily overestimated in depth or underestimated in conductance, if in reality induction and current channelling in the host rock and overburden make even a slight contribution to the anomalous EM field. The lateral resolution for the horizontal coplanar coil system was found to be about 1.7 times the sensor altitude. Similarly, the lateral extension of a horizontal conductive ribbon, required to reach the semi-infinite (half-space) behaviour, is more than three times the sensor altitude. Finally, screening of a steeply dipping plate, caused by a small, conductive horizontal ribbon, is much more severe than screening of the same plate by an extensive horizontal layer. 相似文献
116.
I. M. Villa B. Grobéty S. P. Kelley R. Trigila R. Wieler 《Contributions to Mineralogy and Petrology》1996,126(1-2):67-80
We have investigated the mechanisms and pathways by which Ar diffuses through the McClure Mountains hornblende (ferroan pargasite),
selected as a good example of material normally dated during Ar-Ar studies. A coarse-grained hornblende separated from the
same hand specimen as the MMhb-1 age standard was subjected to a hydrothermal cold-seal bomb experiment and characterized
by TEM. Heated and unheated crystals were subjected to four different 39Ar/40Ar dating extraction techniques: conventional stepwise heating, infra-red laser spot, ultra-violet laser depth profiling,
and closed-system stepwise etching. The stepwise heating age spectrum reproduces the features often interpreted as resulting
from a concentric diffusive zonation, but the other three techniques yield results that are not compatible with such a simple
picture. The IR laser data indicate that the dependence of laboratory Ar loss on grain size, predicted by Fickian diffusion,
is at best poor and instead is related mainly to mineralogical variations. The depth profiles show the importance of planar
zones (spaced between <1 and >150 μm from TEM evidence) in providing fast pathways for inward diffusion of atmospheric Ar
from the capsule, but showed no evidence of diffusive profiles in the bulk of the hornblende lattice. The data from closed
system stepwise etching underscore the role of zones rich in planar defects both for Ar loss and for nucleation of etching.
The age spectra obtained by stepwise heating suffer from the differential breakdown of impurity phases, whose presence can
be diagnosed with several isotope correlation plots; particularly revealing are Cl-Ca-K trends. In addition to the problems
of mineral decomposition during in-vacuo laboratory degassing, an equally important decomposition occurs during many hydrothermal
experiments which, combined with problems of mineral purity, have led to an overestimation of the rate of argon diffusion
in hornblende. The response of hornblende to thermal disturbance in a hydrothermal environment can be every bit as complex
as breakdown in vacuo. Laboratory experiments on bulk samples have not succeeded in quantitatively constraining volume diffusion.
Received: 12 October 1995 / Accepted: 11 July 1996 相似文献
117.
Rainer Putz 《Aquatic Sciences - Research Across Boundaries》1997,59(1):74-93
Chlorophyll a-concentrations, AFWD (ash-free-dry-weight) and photosynthesis rates were estimated for periphyton assemblages in Amazonian black-and white-water habitats over 14 months. Cellulose-acetate strips were incubated in situ and showed few major differences in periphyton quality as compared to natural substrata. The only exceptions were submersed Igapó forest leaves, which exhibited higher proportions of green algae and cyanobacteria though not producing differences in total periphyton biomass. Enclosure experiments showed a considerable nutrient release by inundated non-senescent Igapó forest leaves. Periphyton biomass and productivity were found to be highest in black-and white water mixing zones, where biomass peaked at 41.6 mg Chla/m2 and 19.8 g/m2 AFDW. Production was estimated to be 380 gC/m2·a. Maximum biomass of periphyton in floating meadows was 46 mg Chla/m2 and 10.6 g/m2 AFDW, with an annual production of 170 gC/m2·a. Solimões main channel periphyton values were low: maximum Chla was 7.1 mg/m2, AFDW 0.8 g/m2 and annual production was estimated to be 30 gC/m2. Blackwater periphyton values were lower compared to whitewater and mixed water values but an enlarged trophogenic zone has to be taken into account. Highest Chla content reached 30.9 mg/m2, AFDW 1.43 g/m2. Estimated annual production was 110 gC/m2. Observed mean periphyton productivity of Amazonian blackwater habitats approximately corresponded to mesotrophic attached algae productivity in temperate zones, whereas productivity of whitewater periphyton approached those of temperate eutrophic lakes. The role of periphyton in the Amazon food web is discussed. 相似文献
118.
Rainer Altherr Friedhelm Henjes-Kunst Alan Matthews Hans Friedrichsen Bent Tauber Hansen 《Contributions to Mineralogy and Petrology》1988,100(4):528-541
Sr, O, and D/H isotopic compositions have been analyzed in Miocene metaluminous to slightly peraluminous (I-type) granitoids of the central Aegean. Individual plutonic complexes display significant variations in their
18O and initial87Sr/86Sr compositions.D and
18O compositions of minerals and whole-rocks are mostly in the magmatic range. Some samples from Naxos and Mykonos/Delos show low D and
18O values characteristic of meteoric-water-hydrothermal interaction, but as a whole the changes in
18O and Sr isotopic compositions as a result of hydrothermal alteration were slight, even in instances where marked alteration is petrographically observable. Consequently, the bulk-rock variations of
18O from 8.1 to 12.0 and of87Sr/86Sr from 0.70438 to 0.71450 may be regarded as primary and indicative of the conditions of their evolution. Heterogeneous isotopic compositions observed in the individual plutons of Serifos, Ikaria, Samos and Kos may be caused by the multiple intrusion of chemically and isotopically distinct magma pulses, with high viscosities and relatively rapid consolidation in most cases preventing complete homogenization. The granitoids of Serifos, Ikaria and Kos display weak correlations between the initial87Sr/86Sr and
18O and 1/Sr. The granitoid province shows a positive correlation between87Sr/86Sr and
18O and a non-linear relationship between87Sr/86Sr and 1/Sr, whereby 1/Sr increases more rapidly than the isotopic ratio as the degree of fractionation of the rocks increases. It is argued that assimilation of older continental material by mantle-derived arc magmas with combined fractionation (AFC) is the most plausible model to explain the chemical and isotopic characteristics of the granitoids and the geological situation in which rock-types trend from granodiorites in the (south)west, near the inferred Oligocene-Miocene suture, to granites in the center and monzonites in the (north)east of the province. 相似文献
119.
J. H. Rainer 《地震工程与结构动力学》1986,14(3):369-377
Inertial transducers that measure horizontal movement are affected by rotation of the measurement location. In this paper, the effect of rotation is expressed quantitatively as a fraction of the translational signal amplitude and is shown to depend inversely on the effective radius of rotation of the measurement location and the square of the frequency component of the signal. Correction procedures are presented for various cases that arise in the determination of modal amplitudes and mode shapes for tower structures, suspension bridges and frame building structures. Specific numerical results are included for the CN Tower and the Commerce Court Building in Toronto, Canada, and the Lions' Gate Suspension Bridge in Vancouver, British Columbia. Rotational effects on signals obtained from horizontal transducers can be significant for very low frequency tower structures and suspension bridges, but are not likely to be of importance for frame buildings. 相似文献
120.
Variations in the atomic abundances of 53Cr, 92Zr, 98Ru, 99Ru, and 182W in meteorites and lunar samples relative to terrestrial values may imply the early decay of radioactive 53Mn, 92Nb, 98Tc, 99Tc and 182Hf, respectively. From this one can deduce nucleosynthetic sites and early solar system timescales. Because these effects are very small, production and consumption of the respective isotopes by cosmic-ray interactions is a concern. It has recently been demonstrated that 182W production by neutron capture reactions on 181Ta is crucial for most lunar samples (Leya et al., 2000a). In this study the neutron fluence of each sample was estimated from its nominal cosmic-ray exposure age as deduced from noble gas data. This approach overestimates the true cosmogenic isotopic shift for samples that might have been irradiated very close to the regolith surface. Here we therefore combine our model calculations with the neutron dose proxies 157Gd/158Gd and 149Sm/150Sm. This allows us to accurately correct the measured W isotopic data for cosmic-ray induced shifts without the explicit knowledge of the exposure age or the shielding depth of the sample simply by measuring 157Gd/158Gd and/or 149Sm/150Sm in an aliquot. In addition we present new model results for the GCR-induced effects on 53Mn-53Cr, 92Nb-92Zr and 98Tc-99Tc-98Ru-99Ru. For each of these systems, except Tc-Ru, a proper cosmic-ray dose proxy is given, permitting the accurate correction of measured isotopic ratios for cosmogenic contributions. 相似文献