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1.
Owing to the defaults of MODIS sensor at 667 and 678 nm, data loss may occur when water bodies are highly turbid. A model for estimating MODIS signals at 667 and 678 nm from the signals at 645 nm (MMSS) is developed and constructed here to estimate the MODIS reflectance at top-of-atmosphere at 667 and 678 nm from the reflectance at 645 nm in highly turbid waters. The model is calibrated and validated by a dataset which consists of a bio-optical dataset and six MODIS images collected from the Yellow River Estuary, Changjiang River Estuary, and Taihu Lake, China. It is discovered that the linear relationships between signals above water surface are still available at top-of-atmosphere in a small region, even if atmospheric absorption and scattering are present in the process of photon transmission. The MODIS band at 645 nm is the optimal band for constructing the MMSS model. It may be rational that reflectance at 667 and 678 nm at top-of-atmosphere cannot be recorded by MODIS sensors while the values are larger than 0.76. The MMSS model produces strong performances in retrieving reflectance at top-of-atmosphere at 667 and 678 nm from the reflectance at 645 nm in turbid waters, with an uncertainty of less than 1.21 %. By comparison with the uncertainty of 2–3 % associated with “noise equivalent reflectance”, the uncertainty in the MMSS algorithm predictions (<1.21 %) is not significant. 相似文献
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Shuidonggou site has abundant Paleolithic remains of Late Pleistocene deposition. Studying the evolution of depositional environments is essential to the comprehensive understanding of the living conditions of ancient populations. To reconstruct the depositional environment at Shuidonggou, we carried out archaeological excavations and collected systematic deposition samples at the key position of Shuidonggou Locality 2 for grain size analysis and sporopollen statistics. The environmental evolution around the Shuidonggou site generally underwent four stages at ~72–18 kaBP. During the first stage (~72–41 kaBP), the river developed with gravel and sand stratums. During the second stage (41~34 kaBP), a swamp with numerous aquatic plants formed. In the third stage (34–29 kaBP), site formation was characterized by shallow lake depositional conditions; the climate was relatively warm and humid. The marginal bank depositional conditions deteriorated during the fourth stage (29–18 kaBP), and the site underwent several dry events; the climate also became drier and colder. 相似文献
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LIU Cheng LIU Ruiliang ZHOU Pengcheng LU Chun YANG Zengxin A. Mark POLLARD Peter HOMMEL MA Jian CUI Jianfeng Peter BRAY TONG Jianyi Jessica RAWSON 《《地质学报》英文版》2020,94(3):594-602
Tianshanbeilu is the largest Bronze Age site in eastern Xinjiang, China. Stretching across the entire second millennium BC, it performed a prominent role in connecting the Hexi corridor, Central China and the steppe. A further insight into the metallurgical tradition and the metal supply network is of vital importance to improve our understanding of its multi-connected nature. This paper offers a new set of chemical and isotopic data on the copper-based objects at Tianshanbeilu, including alloying elements, trace elements (impurities) and lead isotopes. Combining the concentrations of arsenic and antimony reveals that arsenic was introduced to copper partially due to the use of specific minerals tethrahedrite-tennantite. Lead isotopes demonstrate that multiple sources of copper were employed at Tianshanbeilu and a majority of them are characterized by common lead, which appears rather different from those of the Central Plains and the Hexi corridor, but highly consistent with local ores. Surprisingly, one object at Tianshanbeilu contains the well-known highly radiogenic lead. This object undoubtedly marks the westernmost boundary of the distribution of the highly radiogenic lead. We also anticipate that more lead isotopic analyses in NW China will further contribute to the study of the highly radiogenic lead in Central China. 相似文献
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International Journal of Earth Sciences - One of the key requirements for a Global Stratotype Section and Point (GSSP) is the absence of tectonic disturbance. The GSSP for the... 相似文献
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In order to investigate the effect of Thiobacillusferrooxidans on the oxidation of pyrite, two parallel experiments, which employed H2SO4 solutions and acidic solutions inoculated with ThiobaciUus ferrooxidans, were designed and carried out at 30℃. The initial pH of the two solutions was adjusted to 2.5 by dropwise addition of concentrated sulphuric acid. The surfaces of pyrite before exposure to leaching solutions and after exposure to the H2SO4 solutions and acidic solutions inoculated with Thiobacillus ferrooxidans were observed by scanning electron microscopy （SEM）. There were a variety of erosion patterns by Thiobacillusferrooxidans on the bio-leached pyrite surfaces. A conclusion can be drawn that the oxidation of pyrite might have been caused by erosion of the surfaces. Attachment of the bacteria to pyrite surfaces resulted in erosion pits, leading to the oxidation of pyrite. It is possible that the direct mechanism plays the most important role in the oxidation of pyrite. The changes in iron ion concentrations of both the experimental solutions with time suggest that ThiobaciUus ferrooxidans can enhance greatly the oxidation of pyrite. 相似文献
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The spectral AOD measurements have been made for the first time over Patiala during multi-platform field campaign ICARB—2006 using a Multi-Wavelength Radiometer (MWR) along with the suspended particulate matter measurements with a high volume sampler. Spectral AOD has higher values in May in comparison to March and April. The monthly mean AOD values at 500 nm are 0.26 ± 0.08, 0.36 ± 0.19 and 0.58 ± 0.20 for the months of March, April and May respectively. The mean AOD is more during afternoon in comparison to forenoon at all wavelengths. The atmospheric turbidity is higher in May and is attributed to dust transported by southerly winds prevailing during this month. The Ångström parameter α varies between zero and 0.68 while β ranges from 0.1 to 0.9. The columnar water vapour content ranges from 0.12 to 2.92 cm, having a mean value of 1.06 ± 0.648 cm. The mean total suspended particulate matter is 334.41 ± 97.56 μgm/m3, an indication of high aerosol loading over Patiala during the campaign period. 相似文献
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Samodurov V. A. Tyul’bashev S. A. Toropov M. O. Logvinenko S. V. 《Astronomy Reports》2022,66(4):341-347
Astronomy Reports - A search for pulse signals was carried out in a new sky area included in the monitoring program for the search for pulsars and transients. Processing of several months data... 相似文献
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《Applied Geochemistry》1999,14(7):953-962
Isotopic compositions of C (δ13C), O (δ18O) and Sr (δ87Sr) were determined for calcite fracture fillings in the crystalline rock penetrated by a 1.6 km drill hole at Laxemar, near the Äspö Hard Rock Laboratory (ÄHRL) in southern Sweden. These calcites precipitated from groundwater some time in the past, and their δ13C, δ18O and δ87Sr values reflect those of the source waters. The present-day groundwater system is hydrochemically stratified with highly saline water underlying more shallow brackish and fresh water. The origin of this stratified system is probably related to past glaciations although the ultimate origin of the deep, highly saline water is still problematical. None of the calcite fracture fillings sampled below 900 m could have precipitated from any of the present-day ground waters which in view of the glacial history of the region is not surprising. However, several shallow calcite fracture fillings are formed by precipitation from the present-day groundwater. Coupled variations in δ13C, δ18O and δ87Sr isotopes at depths in excess of 900 m suggest that these isotope systems in calcite are recording a time-dependent evolution of groundwater composition. 相似文献
12.
Pyrite Surface after Thiobacillus ferrooxidans Leaching at 30℃ 总被引：4，自引：0，他引：4
LU Jianjun LU Xiancai WANG Rucheng LI Juan ZHU Changjian GAO Jianfeng Department of Earth Sciences State Key Laboratory for Mineral Deposits Research Nanjing University Nanjing Jiangsu 《《地质学报》英文版》2006,80(3)
In order to investigate the effect of Thiobacillus ferrooxidans on the oxidation of pyrite, two parallel experiments, which employed H2SO4 solutions and acidic solutions inoculated with Thiobacillus ferrooxidans, were designed and carried out at 30℃. The initial pH of the two solutions was adjusted to 2.5 by dropwise addition of concentrated sulphuric acid. The surfaces of pyrite before exposure to leaching solutions and after exposure to the H2SO4 solutions and acidic solutions inoculated with Thiobacillus ferrooxidans were observed by scanning electron microscopy (SEM). There were a variety of erosion patterns by Thiobacillus ferrooxidans on the bio-leached pyrite surfaces. A conclusion can be drawn that the oxidation of pyrite might have been caused by erosion of the surfaces. Attachment of the bacteria to pyrite surfaces resulted in erosion pits, leading to the oxidation of pyrite. It is possible that the direct mechanism plays the most important role in the oxidation of pyrite. The changes in iron ion concentrations of both the experimental solutions with time suggest that Thiobacillus ferrooxidans can enhance greatly the oxidation of pyrite. 相似文献
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Peng Yuanqiao Tong Jinnan Faculty of Earth Sciences China University of Geosciences Wuhan Gao Yongqun China University of Geosciences Press Wuhan 《中国地质大学学报(英文版)》2001,12(1)
INTRODUCTIONAs a large regression continued over the world at the endof the Paleozoic, a new remarkable transgression was intrudinginto the Lower Yangtze located in the eastern Tethys duringthe Late Permian, resulting in many excellent continuous marine Permian-Triassic sequences in this region. But the middleTriassic indosinian movement transformed this region from marine to continental factes, resulting in the deposition of theLower Triassic in the marked regression setting prior to … 相似文献
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P. F. Zanazzi P. Comodi S. Nazzareni N. Rotiroti S. van Smaalen 《Physics and Chemistry of Minerals》2007,34(1):23-29
The thermal evolution of 10-Å phase Mg3Si4O10(OH)2·H2O, a phyllosilicate which may have an important role in the storage/release of water in subducting slabs, was studied by X-ray single-crystal diffraction in the temperature range 116–293 K. The lattice parameters were measured at several intervals both on cooling and heating. The structural model was refined with intensity data collected at 116 K and compared to the model refined at room temperature. As expected for a layer silicate on cooling in this temperature range, the a and b lattice parameters undergo a small linear decrease, α a = 1.7(4) 10?6 K?1 and α b = 1.9(4) 10?6 K?1, where α is the linear thermal expansion coefficient. The greater variation is along the c axis and can be modeled with the second order polynomial c T = c 293(1 + 6.7(4)10?5 K?1ΔT + 9.5(2.5)10?8 K?2(ΔT)2) where ΔT = T ? 293 K; the monoclinic angle β slightly increased. The cell volume thermal expansion can be modeled with the polynomial V T = V 293 (1 + 8.0 10?5 K?1 ΔT + 1.4 10?7 K?2 (ΔT)2) where ΔT = T ? 293 is in K and V in Å3. These variations were similar to those expected for a pressure increase, indicating that T and P effects are approximately inverse. The least-squares refinement with intensity data measured at 116 K shows that the volume of the SiO4 tetrahedra does not change significantly, whereas the volume of the Mg octahedra slightly decreases. To adjust for the increased misfit between the tetrahedral and octahedral sheets, the tetrahedral rotation angle α changes from 0.58° to 1.38°, increasing the ditrigonalization of the silicate sheet. This deformation has implications on the H-bonds between the water molecule and the basal oxygen atoms. Furthermore, the highly anisotropic thermal ellipsoid of the H2O oxygen indicates positional disorder, similar to the disorder observed at room temperature. The low-temperature results support the hypothesis that the disorder is static. It can be modeled with a splitting of the interlayer oxygen site with a statistical distribution of the H2O molecules into two positions, 0.6 Å apart. The resulting shortest Obas–OW distances are 2.97 Å, with a significant shortening with respect to the value at room temperature. The low-temperature behavior of the H-bond system is consistent with that hypothesized at high pressure on the basis of the Raman spectra evolution with P. 相似文献
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U. M. Eidsvig Z. Medina-Cetina V. Kveldsvik S. Glimsdal C. B. Harbitz F. Sandersen 《Natural Hazards》2011,56(2):529-545
This paper introduces the application of a simple and practical method for estimating the risk associated with a potential tsunamigenic rockslide, by assessing quantitatively hazard, vulnerability, and elements at risk. The proposed method introduces empirical relations between the risk components and illustrates the uncertainty propagation through the steps in the risk analysis. A case study is presented, showing the applicability of the method for estimating the risk associated with the tsunamigenic Åknes rockslope in Stranda municipality in western Norway. Results show, preliminary risk estimates that will be of significant value for future policy and decision making. 相似文献
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Alyson E. Santoro 《Hydrogeology Journal》2010,18(1):187-202
Microbial communities inhabiting “subterranean estuaries” along the subsurface freshwater–saltwater continuum determine the fate of nitrogen discharged to coastal waters. Little is known about the microbes that comprise these communities, or what their ecological and biogeochemical responses will be to increased salinity resulting from saltwater intrusion and aquifer salinization. This review covers basic aspects of the nitrogen cycle relevant to the coastal subsurface and provides a framework for predicting the types of microbes and nitrogen transformations that exist in different subterranean estuary systems. Literature concerning the freshwater–saltwater mixing zones of surficial estuaries, where microbial communities are better characterized, is also reviewed to explore what is known about the impact of increasing salinity on both the community composition and biogeochemical function of the microbial assemblage. Collectively, these studies suggest that salinization will alter microbial community composition for all functional groups involved in nitrogen cycling, and may lead to decreases in nitrification and coupled nitrification-denitrification, and increases in dissimilatory nitrate reduction to ammonium (DNRA). Future collaboration between hydrogeologists and microbial ecologists is needed to fully predict the impact of saltwater intrusion on subsurface microbial communities. 相似文献
19.
《Quaternary Research》2013,80(2):218-234
Previous geochronological and archaeological studies on the rock shelter Jarama VI suggested a late survival of Neanderthals in central Iberia and the presence of lithic assemblages of Early Upper Paleolithic affinity. New data on granulometry, mineralogical composition, geochemical fingerprints and micromorphology of the sequence corroborate the previous notion that the archaeological units JVI.2.1 to JVI.2.3 are slackwater deposits of superfloods, which did not experience significant post-depositional changes, whereas the artifact-rich units JVI.3 and JVI.1 mainly received sediment inputs by sheetwash and cave spall. New AMS radiocarbon measurements on three samples of cut-marked bone using the ultrafiltration technique yielded ages close to, or beyond, the limit of radiocarbon dating at ca. 50 14C ka BP, and hence suggest much higher antiquity than assumed previously. Furthermore, elevated temperature post-IR IRSL luminescence measurements on K feldspars yielded burial ages for subunits JVI.2.2 and JVI.2.3 between 50 and 60 ka. Finally, our reappraisal of the stone industry strongly suggests that the whole sequence is of Mousterian affinity. In conclusion, Jarama VI most probably does not document a late survival of Neanderthals nor an Early Upper Paleolithic occupation in central Iberia, but rather indicates an occupation breakdown after the Middle Paleolithic. 相似文献
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The results of observations on the Large Phased Array of the Lebedev Physical Institute made as part of a survey of the northern sky at 102.5 MHz are reported. Survey source lists for the declination ranges 27.5°–33.5° and 67.5°–70.5° are given, together with their coordinates, flux densities, and identifications with 4C objects. In total, there are 920 sources with flux densities S 102.5≥3.0 Jy in the two zones, which cover 0.73 star. The observing and data-reduction methods are described, and the reliability and completeness of the catalog are estimated. 相似文献