Mesh size effects on mesozooplankton community structure in a semi‐enclosed coastal area and surrounding sea (South Adriatic Sea)     

Marijana Miloslavić  Davor Lučić  Barbara Gangai  Ivona Onofri 《Marine Ecology》2014,35(4):445-455

  相似文献   

Annual and seasonal variability of precipitation in Vojvodina,Serbia     

Ivana Tošić  Ivana Hrnjak  Milivoj B. Gavrilov  Miroslava Unkašević  Slobodan B. Marković  Tin Lukić 《Theoretical and Applied Climatology》2014,117(1-2):331-341

Annual and seasonal variability of precipitation observed at 92 stations in Vojvodina (Serbia) were analyzed during the period 1946–2006. The rainfall series were examined by means of the empirical orthogonal functions (EOF). The first set of singular vectors explains from 68.8 % (in summer) to 81.8 % (in winter) of the total variance. The temporal variability of the time series associated with the main EOF configurations (the principal components, PCs) was examined using the Mann–Kendall test and the spectral analysis. The time series of PC1 revealed decreasing trend in the winter and spring precipitation and increasing trend in the autumn, summer, and annual precipitation. The relationships between the first PC and circulation patterns, such as the North Atlantic Oscillation (NAO), the East Atlantic (EA) pattern, and East Atlantic/West Russia pattern, were also investigated. The PC1, displaying temporal behavior of the first mode, demonstrated evident correspondence with the NAO index in analysis of the annual, winter, and autumn precipitation. Power spectra of the PC1 show statistically significant oscillations of about 3.3 years for the spring precipitation and about 8 and 15 years for the winter precipitation. Comparisons with spectral analysis of authors for some regions in Europe, most of them in the Mediterranean domain, show that similar periodicities are detected.  相似文献   

Seasonal to yearly assessment of temperature and precipitation trends in the North Western Mediterranean Basin by dynamical downscaling of climate scenarios at high resolution (1971–2050)     

M. Gonçalves  A. Barrera-Escoda  D. Guerreiro  J. M. Baldasano  J. Cunillera 《Climatic change》2014,122(1-2):243-256

The complex topography and high climatic variability of the North Western Mediterranean Basin (NWMB) require a detailed assessment of climate change projections at high resolution. ECHAM5/MPIOM global climate projections for mid-21st century and three different emission scenarios are downscaled at 10 km resolution over the NWMB, using the WRF-ARW regional model. High resolution improves the spatial distribution of temperature and precipitation climatologies, with Pearson's correlation against observation being higher for WRF-ARW (0.98 for temperature and 0.81 for precipitation) when compared to the ERA40 reanalysis (0.69 and 0.53, respectively). However, downscaled results slightly underestimate mean temperature (≈1.3 K) and overestimate the precipitation field (≈400 mm/year). Temperature is expected to raise in the NWMB in all considered scenarios (up to 1.4 K for the annual mean), and particularly during summertime and at high altitude areas. Annual mean precipitation is likely to decrease (around ?5 % to ?13 % for the most extreme scenarios). The climate signal for seasonal precipitation is not so clear, as it is highly influenced by the driving GCM simulation. All scenarios suggest statistically significant decreases of precipitation for mountain ranges in winter and autumn. High resolution simulations of regional climate are potentially useful to decision makers. Nevertheless, uncertainties related to seasonal precipitation projections still persist and have to be addressed.  相似文献   

Basement lithostratigraphy of the Adula nappe: implications for Palaeozoic evolution and Alpine kinematics   总被引：1，自引：0，他引：1  

Mattia Cavargna-Sani  Jean-Luc Epard  François Bussy  Alex Ulianov 《International Journal of Earth Sciences》2014,103(1):61-82

The Adula nappe belongs to the Lower Penninic domain of the Central Swiss Alps. It consists mostly of pre-Triassic basement lithologies occurring as strongly folded and sheared gneisses of various types with mafic boudins. We propose a new lithostratigraphy for the northern Adula nappe basement that is supported by detailed field investigations, U–Pb zircon geochronology, and whole-rock geochemistry. The following units have been identified: Cambrian clastic metasediments with abundant carbonate lenses and minor bimodal magmatism (Salahorn Formation); Ordovician metapelites associated with amphibolite boudins with abundant eclogite relicts representing oceanic metabasalts (Trescolmen Formation); Ordovician peraluminous metagranites of calc-alkaline affinity ascribed to subduction-related magmatism (Garenstock Augengneiss); Ordovician metamorphic volcanic–sedimentary deposits (Heinisch Stafel Formation); Early Permian post-collisional granites recording only Alpine orogenic events (Zervreila orthogneiss). All basement lithologies except the Permian granites record a Variscan + Alpine polyorogenic metamorphic history. They document a complex Paleozoic geotectonic evolution consistent with the broader picture given by the pre-Mesozoic basement framework in the Alps. The internal consistency of the Adula basement lithologies and the stratigraphic coherence of the overlying Triassic sediments suggest that most tectonic contacts within the Adula nappe are pre-Alpine in age. Consequently, mélange models for the Tertiary emplacement of the Adula nappe are not consistent and must be rejected. The present-day structural complexity of the Adula nappe is the result of the intense Alpine ductile deformation of a pre-structured entity.  相似文献   

A critical evaluation of using bulk sediment instead of fine fraction in environmental marine studies, investigated on example of Rijeka harbor, Croatia     

Stanislav Frančišković-Bilinski  Neven Cukrov 《Environmental Earth Sciences》2014,71(1):341-356

This work tested the preferential use of fine (<63 μm) or bulk sediment (<2 mm) in environmental research of marine sediments in the Eastern Adriatic. Fine fraction sediment containing silt and clay (<63 μm), predominating in the studied area, was examined to evaluate past and present anthropogenic inputs and to test our hypothesis that investigation of bulk sediment should be preferred. Following aqua regia digestion, chemical analyses of 58 elements were performed by ICP/OES, ICP-MS and cold vapor AAS, and statistical analysis was performed. The concentrations of the majority of the analyzed elements increased with age of the sediment, except for Ag and Sn, which had higher concentrations in recent sediments. The previous main sources of metal contamination in Rijeka harbor were now abandoned municipal-sewage outflow and oil refinery, and continuing harbor activities and antifouling paint use. All activities except of antifouling paint use have been decreasing significantly. Anomalies of selected elements were determined by the box-plot method. More anomalies were found in the bulk sediment than in the fine fraction. Results of Q-modality clustering and factor analysis in the fine fraction almost correlate with that applied on bulk sediments. Thus, it can be said that the differences between the element distribution in the bulk and fine fraction are not statistically significant. Our conclusion is that analysis of bulk marine sediment gives a better insight into the state of pollution and supports previous recommendations to use bulk sediment as a chosen media for environmental studies.  相似文献   

Effects of sinuosity factor on hydrodynamic parameters estimation in karst systems: a dye tracer experiment from the Beyyayla sinkhole (Eskişehir,Turkey)     

Harun Aydin  Mehmet Ekmekçi  Mehmet Evren Soylu 《Environmental Earth Sciences》2014,71(9):3921-3933

The sinuosity factor (SF) is a critical value in karst systems in terms of estimating their hydrodynamic parameters including groundwater velocity, coefficient of dispersion, etc., through dye tracer experiments. SF has been used in a number of different dye tracer experiments in karstic systems to estimate a representative flow path. While knowing SF is crucially important in the estimation of hydrodynamic parameters, its calculation is associated with significant uncertainty due to the complexity of subsurface karstic features. And yet, only a few studies have discussed its uncertainties, which might lead some errors in estimation of hydrodynamic parameters from dye tracer experiment. In this study, dye tracer experiments were conducted in two consecutive years (2003 and 2004) representing low and high flow conditions in the Beyyayla sinkhole (Eski?ehir, Turkey) where the flow path is well known. Uranine was used in experiments as a tracer and QTRACER computer program was used to determine the hydrodynamic properties of the Beyyayla karst system as well as to gain insights into the effects of SF from dye tracer experiments on estimated parameters. The results showed that the breakthrough curve follows a unimodal and a bimodal distribution in low and high flow conditions, respectively. These different distributions stem from the water transport mechanisms, where velocities were calculated as 58.2 and 93.6 m h^?1 during low and high flow conditions observed in a spring emerging from the south side of the studied system. The results also show that the coefficient of dispersion, Reynolds number, and Peclet number increased and longitudinal dispersivity decreased with the higher flow rate. Furthermore, the estimated parameters did not vary with either the flow conditions or the tracer transit time, but they have shown some variations with SF. When SF was increased by 50 %, a change in these parameters was obtained in the range of 50–125 %.  相似文献   

The effect of the geomagnetic activity to the hourly variations of ionospheric foF2 values at low latitudes     

Erdinç Timoçin  Ali Yeşil  İbrahim Ünal 《Arabian Journal of Geosciences》2014,7(10):4437-4442

In this study, the relationship between the hourly changes of the ionospheric critic frequency values of F2 layers in low latitudes and geomagnetic activity is examined by using statistical methods. The ionospheric critical frequency data has been taken from the Manila (121.1° E, 14.7° N) ionosonde station. In order to investigate the effect of sun activity on ionospheric critical frequency, the data of 1981 when the sun was active and of 1985 when the sun was less active has been used. According to the Granger causality test results, on 5 % significance level, a causality relationship from disturbance storm time (Dst) index values to ionospheric critical frequency values direction has been observed. However, a causality relationship from ionospheric critical frequency values to Dst values has not been observed. From the results of cause-and-effect analysis, it is evaluated that the effect of a shockwave occurring in geomagnetic activity on ionospheric critical frequency continues along 72 h, that is, geomagnetic activity has a long-term effect on ionospheric critical frequency. The response of ionospheric critical frequency to geomagnetic activity substantially depends on seasons. This response is more observed especially in equinox period when the sun is active and in winter months. The increase in geomagnetic activity causes ionospheric critical frequency to decrease in night hours and increase in day hours. The same relationship has not been observed exactly, though observed very little in winter months, for 1985 when the sun was less active.  相似文献   

Investigation of surface and subsurface displacements due to multiple tunnels excavation in urban area     

Alireza Talebinejad  Hamid Chakeri  Mahdi Moosavi  Yılmaz Özçelik  Bahtiyar Ünver  Mehmet Ali Hindistan 《Arabian Journal of Geosciences》2014,7(9):3913-3923

Underground structures are currently widely used and are built as urbanism develops. The interactions between perpendicularly crossing and parallel tunnels in the Tehran region are investigated by using a full three-dimensional (3D) finite difference analysis with elastic-plastic material models. Special attention is paid to the effect of subsequent tunneling on the support system, i.e., the shotcrete lining and rock bolts of the existing tunnel. Eventually, as the tunnels are excavated at certain levels, the interaction between the tunnels will certainly have a significant influence on both stress distribution and consequently deformations. Since multilayer tunneling is a three-dimensional phenomenon in nature, 3D numerical solutions must be utilized for analyzing effect of perpendicularly crossing tunnels at various levels. As Tohid twin tunnels and Line 7 pass beneath the Line 4 metro tunnel, changes in stress distribution, deformations, and surface settlements are studied for various conditions and the results are presented in this paper. Consequently, it is shown that there is a significant interaction between tunnels that necessitate certain preventive measures to maintain a stable tunneling operation.  相似文献   

Sedimentological and stratigraphic evolution of northern Lebanon since the Late Cretaceous: implications for the Levant margin and basin     

Nicolas Hawie  Remy Deschamps  Fadi H. Nader  Christian Gorini  Carla Müller  Delphine Desmares  Ahmed Hoteit  Didier Granjeon  Lucien Montadert  François Baudin 《Arabian Journal of Geosciences》2014,7(4):1323-1349

This paper presents an updated review of the Upper Mesozoic and Cenozoic sedimentological and stratigraphic evolution of the Levant margin with a focus on the northern Lebanon. Facies and microfacies analysis of outcrop sections and onshore well cores (i.e., Kousba and Chekka) supported by nannofossil and planktonic foraminifers biostratigraphy, allowed to constrain the depositional environments prevailing in the Turonian to Late Miocene. The “Senonian” (a historical term used to define the Coniacian to Maastrichtian) source rock interval was subdivided into four sub-units with related outer-shelfal facies: (1) Upper Santonian, (2) Lower, (3) Upper Campanian, and (4) Lower Maastrichtian. This Upper Cretaceous rock unit marks the major drowning of the former Turonian rudist platform. This paper confirms the Late Lutetian to Late Burdigalian hiatus, which appears to be a direct consequence of major geodynamic events affecting the Levant region (i.e., the continued collision of Afro-Arabia with Eurasia), potentially enhanced by regressional cycles (e.g., Rupelian lowstand). The distribution of Late Burdigalian–Serravallian rhodalgal banks identified in northern Lebanon was controlled by pre-existing structures inherited from the pulsating onshore deformation. Reef barriers facies occur around the Qalhat anticline, separating an eastern, restricted back-reef setting from a western, coastal to open marine one. The acme of Mount Lebanon’s uplift and exposure is dated back to the Middle–Late Miocene; it led to important erosion of carbonates that were subsequently deposited in paleo-topographic lows. The Late Cretaceous to Cenozoic facies variations and hiatuses show that the northern Lebanon was in a higher structural position compared to the south since at least the Late Cretaceous.  相似文献   

Preservation of diagenetic products of β-carotene in sedimentary rocks from the Lopare Basin (Bosnia and Herzegovina)     

Nenad Grba  Aleksandra Šajnović  Ksenija Stojanović  Vladimir Simić  Branimir Jovančićević  Goran Roglić  Vladisav Erić 《Chemie der Erde / Geochemistry》2014

Sedimentary rocks from the saline formation of the Lopare Basin were investigated. Sediments contain a moderate amount of immature to marginally mature algal organic matter deposited under slightly reducing to anoxic and slightly saline to hypersaline conditions. Almost all of the samples contain β-carotane in a relatively high quantity, and in some, it represents the most abundant compound in the total distribution of hydrocarbons. The objective of the study was to determine the conditions that are favourable to precursors of β-carotene and/or the preservation of the carotenoid hydrocarbon skeleton. Moreover, the dominant transformation pathways of β-carotene under different redox and salinity conditions, which lead to the formation of aromatic carotenoids were defined.  相似文献