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971.
Cell-Fe(III) mineral aggregates produced by anoxygenic Fe(II)-oxidizing photoautotrophic microorganisms (photoferrotrophs) may be influential in the modern Fe cycle and were likely an integral part of ancient biogeochemical cycles on early Earth. While studies have focused on the environmental conditions under which modern photoferrotrophs grow and the kinetics, physiology and mechanism of Fe(II) oxidation, no systematic analyses of the physico-chemical characteristics of those aggregates, such as shape, size, density and chemical composition, have as yet been conducted. Herein, experimental results show most aggregates are bulbous or ragged in shape, with an average particle size of 10-40 μm, and densities that typically range between 2.0 and 2.4 g/cm3; the cell fraction of the aggregates increased and their density decreased with initial Fe(II) concentration. The mineralogy of the ferric iron phase depended on the composition of the medium: goethite formed in cultures grown by oxidation of dissolved Fe(II) medium in the presence of low phosphate concentrations, while poorly ordered ferrihydrite (or Fe(III) phosphates) formed when amorphous Fe(II) minerals (Fe(II)-phosphates) and high concentrations of phosphate were initially present. Importantly, in all experiments, a fraction of the photoautotrophic cells remained planktonic, demonstrating a constant stoichiometric excess of Fe(III) compared to the autotrophically fixed carbon in the biogenic precipitate. These results not only have an important bearing on nutrient and trace element cycling in the modern water column, but the size, shape and composition of the aggregates can be used to estimate aggregate reactivity during sediment diagenesis over short and geologic time scales. 相似文献
972.
Trace elements and cathodoluminescence of quartz in stockwork veins of Mongolian porphyry-style deposits 总被引:1,自引:0,他引:1
Axel Müller Richard Herrington Robin Armstrong Reimar Seltmann Douglas J. Kirwin Nina G. Stenina Andreas Kronz 《Mineralium Deposita》2010,45(7):707-727
The combination of scanning electron microscope–cathodoluminescence (CL), fluid inclusion analysis and high-resolution electron
probe microanalysis of Al, Ti, K and Fe in vein quartz has yielded results permitting a greater understanding of the complex
mineralisation of the Central Oyu Tolgoi and Zesen Uul porphyry-style deposits, southern Mongolia. These data demonstrate
the relationship between quartz precipitation, dissolution and ore deposition as the mineralising fluid chemistry changed
through time. Four major quartz generations are identified in the A-type veins from the stockworks of both the Central Oyu
Tolgoi (OTi to OTiv) and Zesen Uul deposits (ZUi to ZUiv). Despite differences in the associated alteration and mineralisation
style, the observed CL textures and trace element signatures of the quartz generations are comparable between deposits. The
OTi and ZUi stage formed both the primary network of A-type veins and pervasive silicification of the host rock. Using the
Ti-in-quartz geothermometer, crystallisation temperatures for OTi and ZUi of between 598°C and 880°C are indicated. The main
stage of sulphide mineralisation was accompanied by the dissolution of pre-existing quartz (OTi and ZUi) and precipitation
of a weakly luminescent generation of quartz (OTii and ZUii) with a low Ti content, reflected in a calculated temperature
drop from approximately 700°C to 340°C in Central Oyu Tolgoi and 445°C in Zesen Uul. OTii and ZUii stage quartzes show high
and variable Al concentrations. The next stage of quartz in both deposits (OTiii and ZUiii) forms a fine network of veins
in cracks formed in pre-existing quartz. OTiii and ZUiii quartz contain measurable fluid inclusions of moderate salinity (3–17.1 wt.%
NaCl eq.), entrapped in the temperature range 256°C to 385°C. OTiii and ZUiii are not related to any sulphide mineralisation.
The final OTiv and ZUiv stages are characterised by quartz–calcite micro-breccias that penetrate the A-type veins. Based on
the calculated entrapment temperatures, the OTiv/ZUiv stage crystallised between 212°C and 335°C, and the quartz is characterised
by elevated but variable Al and Fe contents. The CL and trace element signatures of the OTi to OTiii and ZUi to ZUiii stages
of the two Mongolian porphyries show similar features to those observed in porphyry-style deposits from other regions. This
suggests that a common sequence of quartz crystallisation occurs during the formation of early veins in many porphyry copper
systems. 相似文献
973.
974.
Soil contamination by heavy metals and organic pollutants around industrial premises is a problem in many countries around
the world. Delineating zones where pollutants exceed tolerable levels is a necessity for successfully mitigating related health
risks. Predictions of pollutants are usually required for blocks because remediation or regulatory decisions are imposed for
entire parcels. Parcel areas typically exceed the observation support, but are smaller than the survey domain. Mapping soil
pollution therefore involves a local change of support. The goal of this work is to find a simple, robust, and precise method
for predicting block means (linear predictions) and threshold exceedance by block means (nonlinear predictions) from data
observed at points that show a spatial trend. By simulations, we compared the performance of universal block kriging (UK),
Gaussian conditional simulations (CS), constrained (CK), and covariance-matching constrained kriging (CMCK), for linear and
nonlinear local change of support prediction problems. We considered Gaussian and positively skewed spatial processes with
a nonstationary mean function and various scenarios for the autocorrelated error. The linear predictions were assessed by
bias and mean square prediction error and the nonlinear predictions by bias and Peirce skill scores. 相似文献
975.
Manuel Stark Tobias Heckmann Livia Piermattei Fabian Dremel Andreas Kaiser Patrick Machowski Florian Haas Michael Becht 《地球表面变化过程与地形》2021,46(10):2019-2043
Uncrewed aerial systems (UAS), combined with structure-from-motion photogrammetry, has already proven to be very powerful for a wide range of geoscience applications and different types of UAS are used for scientific and commercial purposes. However, the impact of the UAS used on the accuracy of the point clouds derived is not fully understood, especially for the quantitative analysis of geomorphic changes in complex terrain. Therefore, in this study, we aim to quantify the magnitude of systematic and random error in digital elevation models derived from four commonly used UAS (XR6/Sony α6000, Inspire 2/X4s, Phantom 4 Pro+, Mavic Pro) following different flight patterns. The vertical error of each elevation model is evaluated through comparison with 156 GNSS reference points and the normal distribution and spatial correlation of errors are analysed. Differences in mean errors (−0.4 to −1.8 cm) for the XR6, Inspire 2 and Phantom 4 Pro are significant but not relevant for most geomorphological applications. The Mavic Pro shows lower accuracies with mean errors up to 4.3 cm, thus showing a higher influence of random errors. QQ plots revealed a deviation of errors from a normal distribution in almost all data. All UAS data except Mavic Pro exhibit a pure nugget semivariogram, suggesting spatially uncorrelated errors. Compared to the other UAS, the Mavic Pro data show trends (i.e. differences increase with distance across the survey—doming) and the range of semivariances is 10 times greater. The lower accuracy of Mavic Pro can be attributed to the lower GSD at the same flight altitude and most likely, the rolling shutter sensor has an effect on the accuracy of the camera calibration. Overall, our study shows that accuracies depend highly on the chosen data sampling strategy and that the survey design used here is not suitable for calibrating all types of UAS camera equally. 相似文献
976.
The Wüstebach catchment belongs to the German TERENO (Terrestrial Environmental Observatories) network and was partially deforested (~21%) by the Eifel National Park in 2013. In this data paper, we provide 11-year precipitation and stream water isotope data and the corresponding runoff discharge rates recorded in the Wüstebach catchment (from 2009 to 2019). In addition, we provide an overview of available datasets and access information for environmental data of the Wüstebach catchment that are discoverable with associated metadata at the Web-based TERENO data portal. We anticipate that this comprehensive data set will give new insights in how deforestation influences the hydrological system, for exampole, in terms of transit time distribution, fraction of young water and water flow paths at the catchment scale. 相似文献
977.
Onur ?al??kan ?hsan ?i?ek Andreas Matzarakis 《Theoretical and Applied Climatology》2012,107(3-4):417-425
Climate is an important resource for tourism and an equally important element that needs to be included in tourism promotions. This study reveals Bursa’s bioclimatological conditions. These conditions were identified by using physiologically equivalent temperature and a Climate–Tourism–Information–Scheme over 10-day periods and analyzing the mean thermal perception values that emerged. Evaluating bioclimatic conditions and meteorological parameters such as air temperature, duration of sunshine, number of wet days, amount of precipitation, and wind from the perspective of tourism will help people choose the best holiday times depending on their individual needs and circumstances. 相似文献
978.
Andreas Richter Marta Marcos Sebastià Monserrat Damià Gomis Simon Ruiz Gunter Liebsch 《Marine Geodesy》2013,36(4):271-289
Two sea-level records, spanning eight months of simultaneous data in 2002, have been derived from pressure tide gauge measurements at Sant Antoni harbor (Eivissa Island, Western Mediterranean) and off Es Vedrà island, 15 km SW from Sant Antoni. The two time series are compared and used to characterize the sea-level variability in the Balearic Sea. The main forcings for the observed variations, astronomic tides, and meteorologic forcing by the inverse barometer effect are quantified. In a further step, an amplitude transfer function is determined, reflecting the frequency dependent amplification or damping of the nontidal sea-level residuals between both locations due to their local topography. The interpretation of the obtained transfer function indicates sea-level modulating topographic specifics not only for the coastal record at Sant Antoni, but also at the Es Vedrà site. In general, the application of such a transfer function allows the prediction of off-shore sea-level variations from coastal tide gauge measurements. In the present study, ellipsoidal sea-surface heights for Es Vedrà are inferred from Sant Antoni tide gauge data with an accuracy of about 1.5 cm by applying the determined transfer function and a geoid model. 相似文献
979.
We present methods for terrain classification on 4 Vesta using Dawn Framing Camera (FC) color information derived from laboratory spectra of HED meteorites and other Vesta-related assemblages. Color and spectral parameters have been derived using publicly available spectra of these analog materials to identify the best criteria for distinguishing various terrains. We list the relevant parameters for identifying eucrites, diogenites, mesosiderites, pallasites, clinopyroxenes and olivine + orthopyroxene mixtures using Dawn FC color cubes. Pseudo Band I minima derived by fitting a low order polynomial to the color data are found to be useful for extracting the pyroxene chemistry. Our investigation suggests a good correlation (R2 = 0.88) between laboratory measured ferrosilite (Fs) pyroxene chemistry vs. those from pseudo Band I minima using equations from Burbine et al. (Burbine, T.H., Buchanan, P.C., Dolkar, T., Binzel, R.P. [2009]. Planetary Science 44, 1331–1341). The pyroxene chemistry information is a complementary terrain classification capability beside the color ratios. We also investigated the effects of exogenous material (i.e., CM2 carbonaceous chondrites) on the spectra of HEDs using laboratory mixtures of these materials. Our results are the basis for an automated software pipeline that will allow us to classify terrains on 4 Vesta efficiently. 相似文献
980.
Sea ice induced changes in ocean circulation during the Eemian 总被引:1,自引:1,他引:0
We argue that Arctic sea ice played an important role during early stages of the last glacial inception. Two simulations of the Institut Pierre Simon Laplace coupled model 4 are analyzed, one for the time of maximum high latitude summer insolation during the last interglacial, the Eemian, and a second one for the subsequent summer insolation minimum, at the last glacial inception. During the inception, increased Arctic freshwater export by sea ice shuts down Labrador Sea convection and weakens overturning circulation and oceanic heat transport by 27 and 15%, respectively. A positive feedback of the Atlantic subpolar gyre enhances the initial freshening by sea ice. The reorganization of the subpolar surface circulation, however, makes the Atlantic inflow more saline and thereby maintains deep convection in the Nordic Seas. These results highlight the importance of an accurate representation of dynamic sea ice for the study of past and future climate changes. 相似文献