Meteoric smoke particle properties derived using dual-beam Arecibo UHF observations of D-region spectra during different seasons     

J.T. Fentzke  D. Janches  I. Strelnikova  M. Rapp 《Journal of Atmospheric and Solar》2009,71(17-18):1982-1991

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Evidence for an early land use in the Rhône delta (Mediterranean France) as recorded by late Holocene fluvial paleoenvironments (1640–100 BC)     

《Geodinamica Acta》2000,13(6):377-389

The overall objective of this paper is to describe the late Holocene (1640–100 BC) sedimentary and biological evolution of the Rhône–delta–plain, to interpret the sedimentary facies and palynofacies as the result of the effects of fluvial dynamic fluctuations and relative sea level change and to evaluate the paleohydrological constraints in the development of the land use and settlements of the Camargue. Focus is made on the upper part of V_III core drilled on NE of the Vaccarès lagoon. By combining sedimentology, palynology, magnetic susceptibility and archeological data, this study allowed to identify the superposition of three types of paleo-environments (marsh, fluvial floodplain, levee/crevasse splay). This sequence indicates a gradual extension of fluvial environments between the end of the second millennium BC and the 1st century BC. The variability of fluvial dynamic is evident during this period with important flood events which contrast with periods of low flow. Pollen record can be a good marker of the fluvial dynamic variability. The expression of the riparian tree pollen grains in the coarser floodplain deposits could correspond to increased fluvial influence and probably to erosion of riverbank during flood events. The local plants are associated to the low energy sedimentary environments. Focuses are made on the relations between the evolution of the environment and land use. The development of the cereal culture in the floodplain of the Rhône delta has been demonstrated between 1640–1410 and 100 BC. The last alluviation of the Rhône perturbs the research of the archaeological sites in the central part of the delta but the existence of the rural villages from the first part of the first millennium BC is highly possible.  相似文献   

Salt Accumulation and Flushing in Unsaturated Fractures in an Arid Environment   总被引：2，自引：0，他引：2  

Noam Weisbrod  Ronit Nativh  Kilon M. Adar  Daniel Ronend 《Ground water》2000,38(3):452-461

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The observed evolution of galaxy clustering versus epoch-dependent biasing models     

M. Magliocchetti  J. S. Bagla  S. J. Maddox  O. Lahav 《Monthly notices of the Royal Astronomical Society》2000,314(3):546-556

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Export production in the Bay of Biscay as estimated from barium – barite in settling material: a comparison with new production     

《Deep Sea Research Part I: Oceanographic Research Papers》2000,47(4):583-601

We present barium data for sediment traps deployed in a northeast Atlantic margin environment (Bay of Biscay). Fluxes of excess barium were measured with the objective of calculating carbon export production rates from the surface mixed layer and thus contribute to the understanding of organic carbon transport in a margin environment. Therefore, it was necessary to properly understand the different processes that affected the barium fluxes in this margin environment. Seasonal variability of POC/Ba flux ratios and decrease of barium solubilisation in the trap cups with increasing depth in the water column probably indicate that the efficiency of barite formation in the organic micro-environment varies with season and that the process is relatively slow and not yet completed in the upper 600 m of water column. Thus barite presence in biogenic aggregates will significantly depend on water column transit time of these aggregates. Furthermore, it was observed that significant lateral input of excess-Ba can occur, probably associated with residual currents leaving the margin. This advected excess-Ba affected especially the recorded fluxes in the deeper traps (>1000 m) of the outer slope region. We have attempted to correct for this advected excess-Ba component, using Th (reported by others for the same samples) as an indicator of enhanced lateral flux and assigning a characteristic Ba/Th ratio to advected material. Using transfer functions relating excess-Ba flux with export production characteristic of margin areas, observed Ba fluxes indicate an export production between 7 and 18 g C m⁻² yr⁻¹. Such values are 3–7 times lower than estimates based on N-nutrient uptake and nutrient mass balances, but larger and more realistic than is obtained when a transfer function characteristic of open ocean systems is applied. The discrepancy between export production estimates based on excess-Ba fluxes and nutrient uptake could be resolved if part of the carbon is exported as dissolved organic matter. Results suggest that margin systems function differently from open ocean systems, and therefore Ba-proxy rationales developed for open ocean sites might not be applicable in margin areas.  相似文献   

Monitoring of Water Flow and Solute Transport Through the Unsaturated Zone Using a Large-Diameter Borehole   总被引：2，自引：0，他引：2  

Michael Zilberbrand  Haim Gvirtzm 《Ground water》1996,34(1):57-65

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Continual fire-making by Hominins at Gesher Benot Ya‘aqov, Israel     

Nira Alperson-Afil   《Quaternary Science Reviews》2008,27(17-18):1733-1739

This paper presents the culmination of an extensive study of fire-use at the Early and early Middle Pleistocene site of Gesher Benot Ya‘aqov. Using software available in the GIS package, we have examined the spatial distribution of burned and unburned flint microartifacts from eight Acheulian archaeological horizons. The results of this study demonstrate that the burned microartifacts are never evenly distributed and dense concentrations are observed. The circumstances that introduced these burned flint artifacts to the archaeological layers are examined, suggesting that anthropogenic rather than natural fires are responsible for the observed patterns. As the evidence for the use of fire is recorded throughout the long stratigraphic sequence, it seems that fire was continually used by the Acheulian hominins of the site. This repetitive use of fire indicates that the hominins of Gesher Benot Ya‘aqov had a profound knowledge of fire-making, enabling them to make fire at will.  相似文献   

PPGIS approach for defining multimodal travel thresholds: Accessibility of popular recreation environments by the water     

《Applied geography (Sevenoaks, England)》2017

It is essential to ensure equal accessibility to services, such as sport and recreation facilities or green and water environments. Differences in accessibility can potentially cause negative health and social welfare implications. Accessibility and service area analyses from the perspective of access equality are typically rather simple. They are often based on arbitrary travel-distance thresholds and made only with a single mode of transport in mind. Thus, they exclude the multidimensional nature of accessibility where individuals' travel behavior and perceived accessibility also play an important role. In this paper, a PPGIS method was used to empirically investigate distances and durations that respondents travel with different modes of transport to access popular water environments. Service area analyses were built on person-based and objectively measured threshold values that not only take into account the spatio-temporal elements of transport networks and a land use component but also recognize the requirements and preferences of individuals and their capacity to access and participate. The results showed that the most common mode of transport to access waters is walking. Generally, the residents travel by foot for 1.7 km to access water environments. Cars were found as the second most common mode of transport used, and most of the popular water environments are accessible by car from every corner of the study area in a given travel threshold time. The results demonstrate the importance of deriving local parameters and the potential of the PPGIS approach for accessibility and service area delineation.  相似文献   

Paleoecological Relations of Foraminifera in a Desert-Enclosed Sea -The Gulf of Aqaba (Elat), Red Sea     

E. Halicz  Z. Reiss 《Marine Ecology》1981,2(1):15-34

Abstract. Planktonic and benthonic foraminifera live in the desert-enclosed, hypersaline and oligotrophic Gulf of Aqaba and northernmost Red Sea near the edge of their ecological tolerance. Marked changes in foraminiferal abundance patterns in the past, resulting from hydrological shifts related to global climatic fluctuations, facilitate a high-resolution ecostratigraphic subdivision of deep-sea records covering the last 150,000 years. Of particular significance are the foraminiferal plankton/benthos ratios, the presence/absence pattern of such species as Globigerinoides sacculifer , as well as the frequency variation of Globigerina bulloules-falconensis, Buliminacea, Miiiolacea and various "rotaliform" species. Paleoceanographic interpretation of the shifts in assemblage composition and of stable oxygen isotope data obtained on planktonic foraminifera and pteropods indicates that during glacial intervals - because of global cooling, lowered sea-level and reduced water exchange at the straits of Bab-el-Mandeb - the temperature of the upper waters fell by about 4–6 ^oC (to 15–17 ^oC), salinity rose by about 10%o to more than 50%₀ while residence time of the water became longer and the input/output ratio of nutrients became higher. As a consequence, fertility of the photic zone was higher, the organic content of the sediments increased and oxygen levels in the deep basin became reduced. Thus, sea level-oscillations and strait-dynamics played a major role in the foraminiferal paleoecology of the Red Sea.  相似文献   

Salinity-Temperature Relations and Morphotypes of a Mixed Population of Coccoid Cyanobacteria from a Hot, Hypersaline Pond in Israel     

Inka  Dor Miriam  Hornoff 《Marine Ecology》1985,6(1):13-25

Abstract. A mixed population of unicellular and colonial cyanobacteria was transferred into culture from a hypersaline helio-thermal pond in the vicinity of the Dead Sea. The entire complex of strains, incubated in Dead Sea water of varying salinity and temperature, showed a pronounced shift of the maximal growth from a salinity of 72 g l^-1 at 30 ^oC up to 142 g 1^-1 at 50 ^oC. Over the above range of salinities and temperatures, these cyanobacteria were capable of about four divisions per day, providing that any increase in salinity was coupled with the suitable increase in temperature. The above peculiar adaptation can explain the prominent success of this group of microorganisms in the extreme and unstable ecological conditions of hypersaline habitats. Amounts of slime accumulating in the cultures were proportional to the incubation temperature.  相似文献