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31.
A vertebrate burrow-bearing layer of late Pleistocene age is commonly found at many Paleolithic archaeological sites in Korea. The burrows are straight to slightly curved in horizontal (plan) view and gently inclined in lateral (sectional) view. They are interpreted as having been produced by rodent-like mammals based on their size and architecture. The significance of such burrow-bearing layers as a characteristic stratigraphic marker unit is demonstrated by high burrow abundance, consistent stratigraphic position, lack of stratigraphic recurrence at these sites, and widespread geographic extent. Three dating methods, tephrochronology, radiocarbon, and OSL dating, were used to infer the age of these burrow-bearing layers. The dating results indicate that they were formed between ca. 40,000 and 25,000 yr (MIS 3−2), and this suggests that this layer can be used as a stratigraphic time-marker in late Pleistocene paleosol sequences for this region. 相似文献
32.
Yong Il Lee Hyoun Soo Lim Ho Il Yoon Andrzej Tatur 《Quaternary Science Reviews》2007,26(25-28):3167-3178
Several reworked tephra layers in gravity-flow deposits are present in lacustrine core sediments collected from Hotel and Rudy Lakes on King George Island, South Shetland Islands, maritime sub-Antarctica. This study tests the values of tephra for establishing regional tephrochronologies for lakes in ice-covered landscapes in the vicinity of volcanoes. The tephra record is more abundant in a long Hotel Lake core (515 cm long). This study uses volcanic glass samples from five tephra layers of Hotel Lake and from one tephra layer of Rudy Lake. Morphologically, tephras are mixtures of basaltic and pumice shards, both having various degrees of vesicularity. Major element analyses of glass shards reveal that the majority of the glass fragments belong to basic glass (<60 wt% SiO2), compositionally ranging from basalt to low-silica andesite and subalkaline series medium-K tholeiites, probably sourced from Deception Island located 130 km southwest of King George Island. Less than 20% of tephra belongs to silicic glass and occurs in three tephra horizons E of Hotel Lake. However, source volcano(es) for about 10% of basic tephra and silicic tephra are not readily identified from nearby volcanic centers. Except for the studied tephra in Rudy Lake, all tephra samples in Hotel Lake are not ashfall deposits but reworked and redeposited pyroclasts derived from retreating ice sheet, resulting in the occurrence of geochemically equivalent tephra samples in different tephra horizons. The dating of the studied tephra horizons represents the timing of deglaciation rather than that of volcanic eruptions. The result of this study implies that combined with sedimentological information more chemical criterion is necessary to study tephrochronology and regional correlation and to understand paleoenvironmental changes using tephra. 相似文献
33.
Dolomitic concretions in diatomaceous hemipelagic sediments of the Miocene Pohang Basin in the southwestern East Sea (Sea of Japan) preserve distinct signals of two independent sedimentary processes, which controlled the extents of isotopic compositions. Variable δ18O (−9.1‰ to +0.7‰) and high δ13C (+3.1‰ to +17.9‰) values suggest that the concretions formed in the methanogenic zone with alteration of the residual mid-Miocene seawater by volcanogenic sediments. Remarkable δ18O and δ13C values show a strong linear relationship, indicating that distinctly independent depositional processes operated during the formation of the concretions. The degree of methanogenesis was enhanced during rapid hemipelagic sedimentation of organic-rich particles, resulting in higher δ13C values, and the effect of volcaniclastics was diluted, maintaining the original properties of ambient mid-Miocene seawater. In contrast, lower δ18O and 87Sr/86Sr values characterize the effect of volcaniclastic sediments that were transported by intermittent gravity flows and interacted with mid-Miocene seawater. The input of volcaniclastic sediment probably degraded the role of methanogenesis by lowering the contents of organic matter and thereby decreased the δ13C values within the concretions. Isotopic signals recorded within the concretions highlight understanding of the depositional environment and evolution of the pore-water chemistry. 相似文献
34.
35.
Chang‐Soo Rim 《水文研究》2008,22(5):703-714
Meteorological and environmental data measured in semiarid watersheds during the summer monsoon and winter periods were used to study the interrelationships among flux, meteorological and soil water variables, and to evaluate the effects of these variables on the daily estimation of actual evapotranspiration (AET). The relationship between AET and potential evapotranspiration (PET) as a function of soil water content, as suggested by Thornthwaite–Mather and by Morton, was studied to determine its applicability to the study area. Furthermore, multiple linear regression (MLR) analysis was employed to evaluate the order of importance of the meteorological and soil water factors involved. The results of MLR analysis showed that the combined effects of available energy, soil water content and wind speed were responsible for more than 70% of the observed variations in AET during the summer monsoon period. The analyses also indicate that the combined effects of available energy, vapour pressure deficit and wind speed were responsible for more than 70% of the observed variations in AET during the winter period. However, the test results of two different approaches, using the relationships between AET and PET as a function of soil water content, indicated some inadequacy. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
36.
JUN Ki Cheon JEONG Weon Mu CHOI Jin Yong PARK Kwang Soon JUNG Kyung Tae KIM Mee Kyung CHAE Jang Won QIAO Fangli 《海洋学报(英文版)》2015,34(12):19-28
Record-breaking high waves occurred during the passage of the typhoon Bolaven (1215) (TYB) in the East China Sea (ECS) and Yellow Sea (YS) although its intensity did not reach the level of a super typhoon. Winds and directional wave measurements were made using a range of in-situ instruments mounted on an ocean tower and buoys. In order to understand how such high waves with long duration occurred, analyses have been made through measurement and numerical simulations. TYB winds were generated using the TC96 typhoon wind model with the best track data calibrated with the measurements. And then the wind fields were blended with the reanalyzed synoptic-scale wind fields for a wave model. Wave fields were simulated using WAM4.5 with adjustment of Cd for gust of winds and bottom friction for the study area. Thus the accuracy of simulations is considerably enhanced, and the computed results are also in better agreement with measured data than before. It is found that the extremely high waves evolved as a result of the superposition of distant large swells and high wind seas generated by strong winds from the front/right quadrant of the typhoon track. As the typhoon moved at a speed a little slower than the dominant wave group velocity in a consistent direction for two days, the wave growth was significantly enhanced by strong wind input in an extended fetch and non-linear interaction. 相似文献
37.
Hans-Uwe Dahms Hyoung-Min Joo Jae Hyung Lee Mi Sun Yun So Hyun Ahn Sang Heon Lee 《Ocean Science Journal》2015,50(4):639-648
Demersally drifting organisms were collected at Ny Ålesund (Svalbård–Arctic Ocean) to study the taxon composition and relative abundances in the Arctic summer. Catch potentials of two collection devices for demersal drift were compared. A lowvolume submersible drift-pump and a drift-net unit were employed for the collection of demersally drifting biota, particularly for shallow aquatic habitats. With the exception of Appendicularia, Chaetognatha, Coelenterata, and Ctenophora, which were damaged at times, the pump catches were in good condition and sufficient for identification and quantification of less mobile fauna. A comparison of the two devices revealed that the drift-pump collected more specimens than the drift-net. However, the drift-net may have caused an underestimation of the abundances of invertebrates. No differences in identified taxon number and indices of richness, evenness and diversity were found. However, the proportion of invertebrate animals in the two devices was different for the three groups: zooplankton, macrofauna and meiofauna. At Svalbård, zooplankton, larvae of macrofauna, and meiofauna were successfully collected by the two collecting devices. However, the catchibility of the two devices in collecting various invertebrate taxa was different and, therefore, a sound ‘Device Effect’ was revealed. 相似文献
38.
39.
A two-dimensional cloud model with bin microphysics was used to investigate the effects of cloud condensation nuclei (CCN) concentrations and thermodynamic conditions on convective cloud and precipitation developments. Two different initial cloud droplet spectra were prescribed based on the total CCN concentrations of maritime (300 cm− 3) and continental (1000 cm− 3) air masses, and the model was run on eight thermodynamic conditions obtained from observational soundings. Six-hourly sounding data and 1-hourly precipitation data from two nearby weather stations in Korea were analyzed for the year 2002 to provide some observational support for the model results.For one small Convective Available Potential Energy (CAPE) ( 300 J kg− 1) sounding, the maritime and continental differences were incomparably large. The crucial difference was the production of ice phase hydrometeors in the maritime cloud and only water drops in the continental cloud. Ice phase hydrometeors and intrinsically large cloud drops of the maritime cloud eventually lead to significant precipitation. Meanwhile negligible precipitation developed from the continental cloud. For the three other small CAPE soundings, generally weak convective clouds developed but the maritime and continental clouds were of the same phases (both warm or both cold) and their differences were relatively small.Model runs with the four large CAPE ( 3000 J kg− 1) soundings demonstrated that the depth between the freezing level (FL) and the lifting condensation level (LCL) was crucial to determine whether a cloud becomes a cold cloud or not, which in turn was found to be a crucial factor to enhance cloud invigoration with the additional supply of freezing latent heat. For two large CAPE soundings, FL–LCL was so deep that penetration of FL was prohibitive, and precipitation was only mild in the maritime clouds and negligible in the continental clouds. Two other soundings of similarly large CAPE had small FL–LCL, and both the maritime and continental clouds became cold clouds. Precipitation was strong for both but much more so in the maritime clouds, while the maximum updraft velocity and the cloud top were slightly higher in continental clouds. Although limited to small CAPE cases, more precipitation for smaller FL–LCL for a selected group of precipitation and thermodynamic sounding data from Korea was in support of these model results in its tendency.These results clearly demonstrated that the CCN effects on cloud and precipitation developments critically depended on the given thermodynamic conditions and not just the CAPE but the entire structure of the thermodynamic profiles had to be taken into account. 相似文献
40.
Effects of natural and calcined oyster shells on Cd and Pb immobilization in contaminated soils 总被引:5,自引:0,他引:5
Yong Sik Ok Sang-Eun Oh Mahtab Ahmad Seunghun Hyun Kwon-Rae Kim Deok Hyun Moon Sang Soo Lee Kyoung Jae Lim Weon-Tai Jeon Jae E. Yang 《Environmental Earth Sciences》2010,61(6):1301-1308
In Korea, soils adjacent to abandoned mines are commonly contaminated by heavy metals present in mine tailings. Further, the
disposal of oyster shell waste by oyster farm industries has been associated with serious environmental problems. In this
study, we attempted to remediate cadmium (Cd)- and lead (Pb)-contaminated soils typical of those commonly found adjacent to
abandoned mines using oyster shell waste as a soil stabilizer. Natural oyster shell powder (NOSP) and calcined oyster shell
powder (COSP) were applied as soil amendments to immobilize Cd and Pb. The primary components of NOSP and COSP are calcium
carbonate (CaCO3) and calcium oxide (CaO), respectively. X-ray diffraction, X-ray fluorescence and scanning electron microscope analyses conducted
in this study revealed that the calcination of NOSP at 770°C converted the less reactive CaCO3 to the more reactive CaO. The calcination process also decreased the sodium content in COSP, indicating that it was advantageous
to use COSP as a liming material in agricultural soil. After 30 days of incubation, we found that the 0.1 N HCl-extractable
Cd and Pb contents in soil decreased significantly as a result of an increase in the soil pH and the formation of metal hydroxides.
COSP was more effective in immobilizing Cd and Pb in the contaminated soil than NOSP. Overall, the results of this study suggest
that oyster shell waste can be recycled into an effective soil ameliorant. 相似文献