Refinement of genetic and structural models of the úrkút manganese ore deposit (W-Hungary, Europe) using statistical evaluation of archive data     

Lóránt Bíró  Márta Polgári  Tivadar M. Tóth  Tamás Vigh 《Central European Journal of Geosciences》2012,4(3):478-494

Although the úrkút manganese ore deposit in western placecountry-regionHungary has been exploited for at least 90 years, there are still numerous open questions concerning ore genetics as well as structure and geometry of the ore body. A large set of available archive data for the deposit have been reviewed and evaluated in order to solve some of the most crucial problems. For processing, besides diverse GIS approaches, univariate and multivariate statistical methods were used on the created unified database. The main aims of the mathematical treatment were giving a classification scheme for the wide spectrum of Mn-ores based on their chemical composition (Mn, Fe, Si, P) as well as evaluation of their spatial distribution. For the ore characterization and understanding the genetic processes, cluster and discriminant function analyses were used. Results of the multivariate treatment verified the existence of different ore types and provided an exact chemical definition for all of them. It alsoinferred that the main geochemical processes that took place in ore genesis were similar for all sample groups (ore types) with significantly different weights in each case. A 3D evaluation of the úrkút mine heading map system shows that the ore body covers the footwall surface as a stratiform sheet throughout the study area. Palaeo-relief studies suggest a significant difference between the footwall and hanging wall morphologies which clearly implies tectonic activity following ore deposition. The deposit was affected by an E-W compression stress field near the Aptian-Albian transition causing folding of the Mn deposit.  相似文献   

Mixed heavy metals tolerance and radial oxygen loss in mangrove seedlings   总被引：2，自引：0，他引：2  

Y. Liu  N.F.Y. Tam  J.X. Yang  N. Pi  M.H. Wong  Z.H. Ye 《Marine pollution bulletin》2009,(12):1843-1849

The effects of a mixture of heavy metals (Pb, Zn and Cu) on growth, radial oxygen loss (ROL) and the spatial pattern of ROL were investigated in mangrove seedlings of three species: Aegiceras corniculatum, Avicennia marina and Bruguiera gymnorrhiza. Heavy metals inhibited the growth of seedlings and led to decreased ROL and changes in the “tight” barrier spatial pattern of ROL. There was a significant positive correlation between the amount of ROL from the roots of seedlings and metal tolerance. The species with the highest ROL amount, B. gymnorrhiza, were also the most tolerant to heavy metals. The “tight” barrier spatial ROL pattern was also related to metal tolerance in the seedlings. Therefore, we conclude that both ROL amount and “tight” barrier spatial ROL pattern in the roots of the mangrove seedlings play an important role in resistance to heavy metal toxicity.  相似文献   

Biological risk and pollution history of polycyclic aromatic hydrocarbons (PAHs) in Nansha mangrove,South China     

Qihang Wu  Jonathan Y.S. Leung  Nora F.Y. Tam  Shejun Chen  Bixian Mai  Xizhen Zhou  Lihua Xia  Xinhua Geng 《Marine pollution bulletin》2014

Chinese government has taken various measures to alleviate pollution caused by polycyclic aromatic hydrocarbons (PAHs) in the region of Pearl River Delta since the economic reform in 1978, but the effectiveness of these measures remains largely unknown. This study aimed to elucidate the biological risk and pollution history of PAHs by measuring the concentrations of 28 PAHs in the surface and core sediments, respectively, in Nansha mangrove. Results found that the biological risk of PAHs was low without obvious spatial variation. The PAH concentration along the depth gradient indicated that PAH pollution was stabilized since the early 1990s while the source of PAHs has gradually changed from combustion of coal to petroleum products. This implied that the mitigation measures taken by the Chinese government were effective. Compared to marine bottom sediment, we propose that using mangrove sediment can provide a more accurate and precise estimate of pollution history of PAHs.  相似文献   

Intermittency analysis and spatial dependence of magnetic field disturbances in the fast solar wind     

Y.-H. Yang  Sunny W.Y. Tam 《Journal of Atmospheric and Solar》2010,72(1):97-108

Based on Helios measurements, seven quantities of normalized PDF (Probability Distribution Function) associated with magnetic field and its disturbances are utilized to characterize the intermittency in the fast solar wind using Castaing distributions and the idea of “Flatness”. The magnetic field fluctuations are found to be more intermittent at farther distances from the sun. The “Flatness” decreases with increasing time scales, with the corresponding PDF eventually approaching Gaussian distributions. Such a transition occurs at a relatively small time scale for the perpendicular component of perturbed field. The increase in “Flatness” with decreasing time scale is more apparent farther from the sun. By examining how the relative energy density of magnetic disturbances at various time scales changes with the mean field, our study supports the idea that the perturbed fields in the fast solar wind in the frequency range considered are consistent with cross-scale redistribution of wave energy favoring larger scales.  相似文献   

Impacts of Kelvin wave forcing in the Peru Humboldt Current system: Scenarios of spatial reorganizations from physics to fishers   总被引：2，自引：1，他引：1  

Sophie Bertrand  Boris Dewitte  Jorge Tam  Erich Díaz  Arnaud Bertrand   《Progress in Oceanography》2008,79(2-4):278

Because climate change challenges the sustainability of important fish populations and the fisheries they support, we need to understand how large scale climatic forcing affects the functioning of marine ecosystems. In the Humboldt Current system (HCS), a main driver of climatic variability is coastally-trapped Kelvin waves (KWs), themselves originating as oceanic equatorial KWs. Here we (i) describe the spatial reorganizations of living organisms in the Humboldt coastal system as affected by oceanic KWs forcing, (ii) quantify the strength of the interactions between the physical and biological component dynamics of the system, (iii) formulate hypotheses on the processes which drive the redistributions of the organisms, and (iv) build scenarios of space occupation in the HCS under varying KW forcing. To address these questions we explore, through bivariate lagged correlations and multivariate statistics, the relationships between time series of oceanic KW amplitude (TAO mooring data and model-resolved baroclinic modes) and coastal Peruvian oceanographic data (SST, coastal upwelled waters extent), anchoveta spatial distribution (mean distance to the coast, spatial concentration of the biomass, mean depth of the schools), and fishing fleet statistics (trip duration, searching duration, number of fishing sets and catch per trip, features of the foraging trajectory as observed by satellite vessel monitoring system). Data sets span all or part of January 1983 to September 2006. The results show that the effects of oceanic KW forcing are significant in all the components of the coastal ecosystem, from oceanography to the behaviour of the top predators – fishers. This result provides evidence for a bottom-up transfer of the behaviours and spatial stucturing through the ecosystem. We propose that contrasting scenarios develop during the passage of upwelling versus downwelling KWs. From a predictive point of view, we show that KW amplitudes observed in the mid-Pacific can be used to forecast which system state will dominate the HCS over the next 2–6 months. Such predictions should be integrated in the Peruvian adaptive fishery management.  相似文献   

Further development in theory/data closure of the photoelectron-driven polar wind and day-night transition of the outflow     

S. W. Y. Tam  F. Yasseen  T. Chang 《Annales Geophysicae》1998,16(8):948-968

Recent in situ observations have revealed novel features in the polar wind. Measurements between 5000 and 9000 km altitude by the Akebono satellite indicate that both H⁺ and O⁺ ions can have remarkably higher outflow velocities in the sunlit region than on the nightside. Electrons also display an asymmetric behavior: the dayside difference in energy spread, greater for upward-moving than downward-moving electrons, is absent on the nightside. Here, we discuss the further development of a theory by Tam et al. that can explain most of these observed peculiar properties by properly taking into account the global, kinetic, collisional effects of the sunlit photoelectrons, on the background polar wind and the electric field. Quantitative comparisons of the calculated results with actual data will be described. In addition, transition from the daytime photoelectron-driven polar wind to the night-time polar wind will be discussed.  相似文献   

Study on the relationship between lineaments and borehole specific capacity in a fractured and karstified limestone area in Vietnam   总被引：3，自引：0，他引：3  

V.?T.?Tam  F.?De?Smedt  O.?BatelaanEmail author  A.?Dassargues 《Hydrogeology Journal》2004,12(6):662-673

For a karstified limestone area in NW Vietnam, the relationship between the distribution of lineaments and borehole specific capacity is determined, resulting in the conclusion that not only the borehole geomorphological-hydrogeological position but also the lineament distribution influences the specific capacity.No significant spatial well yield patterns are evident in this highly fractured-karstified region. The supposition is that lineaments caused by geotectonic activities affect the local variability in borehole specific capacity. Sixteen pumping tests in conjunction with a comprehensive lineament analysis are used to prove this relationship. The boreholes and lineaments are classified into two groups according to their similarity in geomorphological-hydrogeological features. Lineaments tend to be less detectable in discharge areas (lowland, wide and flat valleys) in contrast to the high density in recharge areas (highland narrow-mountainous ravines). In addition, the presence of a stream network in the former can act as a recharge source to the underlain karstic groundwater system. Consequently, boreholes that are in the discharge areas with a lower density of lineaments often produce high yield. For recharge areas with a high density of lineaments, a good correlation is found between lineament density and borehole specific capacity.

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Resumen El resultado ha sido la conclusión de que tanto la distribución de lineamientos como el nivel base local de erosión, i. e. la red de arroyos, influyen el rendimiento de los pozos. No hay ningún patrón evidente significativo de rendimiento de pozos según parámetros espaciales en esta región altamente karstificada y fracturada. La suposición es que los lineamientos causados por actividad geotectónica afectan la variabilidad local de rendimiento de los pozos. Se han utilizado dieciséis pruebas de bombeo en conjunción con un análisis de lineamientos amplio para descubrir la relación. Los pozos y lineamientos se han clasificado en dos grupos de acuerdo con sus similitudes en rasgos geomorfológicos-hidrogeológicos. Se tiende a detectar menos lineamientos en valles anchos y planos en contraste con la alta densidad en áreas de valles montaosos angostos. Adicionalmente, la presencia de una red de arroyos en estos últimos puede actuar como fuente de recarga del sistema de aguas subterráneas kárstico subyacente. En consecuencia, los pozos que se encuentran en el área con una menor densidad de lineamientos pero cercanos a un nivel local base de erosión frecuentemente tienen un rendimiento alto. En el caso de los valles angostos con una alta densidad de lineamientos, se ha encontrado una correlación alta entre densidad de lineamientos y rendimiento de pozos.

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Résumé La relation entre la distribution des linéaments et le rendement des puits est déterminée pour une région dans le nord ouest du Vietnam composée de calcaires karstiques. La conclusion qui résulte de lanalyse de cette relation est que la distribution des linéaments ainsi que leur niveau local dérosion affectent le rendement des puits. Aucune tendance na été observée dans la distribution spatiale des puits selon leur rendement au sein de cette région karstique grandement fracturée. On suppose que les linéaments produits par lactivité géotectonique ont une influence sur la variabilité locale du rendement des puits. Les résultats de seize essais de pompage et une analyse complète des linéaments sont utilisés pour établir la relation. Les puits et les linéaments sont classés en deux groupes selon la similarité de leur caractéristiques géomorphologiques et hydrogéologiques. Les linéaments sont plus difficilement repérables dans les grandes vallées plates que dans les étroites vallées de montagne, qui présentent une densité élevée de linéaments. De plus, la présence de rivières dans les premières peut contribuer à la recharge du système découlement souterrain karstique sous-jacent. Par conséquent, les puits situés dans les régions à faible densité en linéaments, mais qui se trouvent près de linéaments à niveau local dérosion élevé présentent souvent un rendement élevé. Dans les vallées étroites ayant une grande densité de linéaments, il y a généralement une corrélation élevée entre la densité des linéaments et le rendement des puits.

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Impact assessment of climate change on a coastal groundwater system,Central Vietnam     

Vu Thanh Tam  Okke Batelaan  Ine Beyen 《Environmental Earth Sciences》2016,75(10):908

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Magnetic susceptibility as a possible correlation tool in Quaternary alluvial stratigraphy          下载免费PDF全文

Zoltán Püspöki  István J. Kovács  Tamás Fancsik  Annamária Nádor  Edit Thamó‐Bozsó  Ágnes Tóth‐Makk  Beatrix Udvardi  Péter Kónya  Judit Füri  Zsolt Bendő  László Zilahi‐Sebess  Ferenc Stercel  Ágnes Gulyás  Richard W. Mcintosh 《Boreas: An International Journal of Quaternary Research》2016,45(4):861-875

Correlation of the fluvial magnetic susceptibility (MS) record of borehole Devavanya‐1 in the Körös Basin (eastern Hungary) with Chinese aeolian MS records (Jingbian, Lingtai) and the marine δ¹⁸O record from the Equatorial Pacific (V28‐239) is established here based on cross‐correlations and singular spectral analysis. A basin‐scale well‐to‐well correlation based on magnetic susceptibility records was also performed involving unpublished cores. To refine the age model, a Monte Carlo simulation was conducted using the Chinese Jingbian section as a tuning target. Spectral analysis of the tuned record revealed c. 400, c. 100 and c. 41 ka cycles over the 2.5 million years of the Quaternary fluvial succession. To ensure a complementary palaeoclimate proxy, the full width at half maximum of smectites was measured as a facies‐independent indicator of weathering intensity. This investigation was carried out on a subset of samples involved in MS measurements representing a c. 400 ka time interval across the top of the Olduvai subchron. A phase‐shift between MS and weathering intensity recorded in the clay mineralogy indicates different response times of the considered proxies. The fluvial MS record is determined by the climatic control on delivery and preservation of magnetic minerals, mainly of magnetite. Under cold‐and‐dry climate these minerals were released owing to frost shattering in the adjacent hinterlands and were transported to alluvial plains in the early postglacial periods thanks to the increasing discharge of rivers. With further warming the weathering‐sensitive magnetic minerals soon disappeared from the soils of the catchment area and thus from the fluvial load. As a result, in fluvial successions early postglacial warmings are expressed by the occurrences of MS maxima (magnetic episodes), while the palaeotemperature maximum and the subsequent cooling remain concealed within the tract of low MS values. The early postglacial magnetic episodes may serve as ideal stratigraphical markers in regional and global correlations.  相似文献   

Global instability in the Ghil–Sellers model     

Tamás Bódai  Valerio Lucarini  Frank Lunkeit  Robert Boschi 《Climate Dynamics》2015,44(11-12):3361-3381

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