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排序方式: 共有273条查询结果,搜索用时 15 毫秒
61.
This work describes the potential usability of neutralized red mud for the removal of organochlorine pesticides (OCPs) from aqueous solutions. After examination on the adsorption capability of neutralized red mud for all studied OCPs, the experiments were performed by employing aldrin as a model compound. The effect of several parameters, such as contact time, pH of the solution, initial aldrin concentration, and dosage of the adsorbent was evaluated by batch experiments. The determination of OCPs was carried out using traditional liquid–liquid extraction followed by a GC coupled with µ‐electron capture detector (GC‐µECD). The results showed that adsorption equilibrium time depended upon the initial aldrin concentration and adsorption followed the second‐order kinetic model. Kinetic study also indicated that the film diffusion mechanism was a main rate control mechanism. The removal was explained by considering the electrostatic interactions between metal oxides surface of the neutralized red mud and inductively charged centers (negative charge (d?) of chlorine atoms and positive charge (d+) of π‐cloud aromatic ring) of the aldrin molecules. In comparison to the Langmuir isotherm model, the Freundlich model better represented the adsorption data. The neutralized red mud was also succesfully employed for the removal of OCPs from real water samples, including tap water and surface (lake) water, fortified with studied OCPs. 相似文献
62.
In this study, the effect of the electron sound speed on the extraordinary wave propagation is calculated without an approximation
for either collisional or collisionless cases in the ionospheric plasma by using the real geometry of the Earth’s magnetic
field for the Northern Hemisphere. It is observed that there is no remarkable effect on the propagation of the extraordinary
wave, especially at reflection altitudes. But it is also observed that the magnitudes of k
2 (the square of the wave number) have changed every season, and the phase velocity of wave in warm ionospheric plasma has
increased. 相似文献
63.
Orkun I. Davutluoglu Galip Seckin Cagatayhan B. Ersu Turan Yilmaz Bulent Sari 《洁净——土壤、空气、水》2011,39(2):185-194
The aim of this study was to assess the level of heavy metals (Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) contamination and enrichment in the surface sediments of the Seyhan River, which is the receiving water body of both treated and untreated municipal and industrial effluents as well as agricultural drainage waters generated within Adana, Turkey. Sediment and water samples were taken from six previously determined stations covering the downstream of the Seyhan dam during both wet and dry seasons and the samples were then analyzed for the heavy metals of concern. When both dry and wet seasons were considered, metal concentrations varied significantly within a broad range with Al, 7210–33 967 mg kg?1 dw; Cr, 46–122 mg kg?1 dw; Cu, 6–57 mg kg?1 dw; Fe, 10 294–26 556 mg kg?1 dw; Mn, 144–638 mg kg?1 dw; Ni, 82–215 mg kg?1 dw; Pb, 11–75 mg kg?1 dw; Zn, 34–146 mg kg?1 dw in the sediments while Cd was at non‐detectable levels for all stations. For both seasons combined, the enrichment factor (EF) and the geo‐accumulation index (Igeo) for the sediments in terms of the specified metals ranged from 0.56 to 10.36 and ?2.92 to 1.56, respectively, throughout the lower Seyhan River. The sediment quality guidelines (SQG) of US‐EPA suggested the sediments of the Seyhan River demonstrated “unpolluted to moderate pollution” of Cu, Pb, and Zn, “moderate to very strong pollution” of Cr and Ni. The water quality data, on the other hand, indicated very low levels of these metals suggesting that the metal content in the surface sediments were most probably originating from fine sediments transported along the river route instead of water/wastewater discharges with high metal content. 相似文献
64.
Wet and dry spell analysis of Global Climate Model-generated precipitation using power laws and wavelet transforms 总被引:2,自引:2,他引:0
Ashok K. Mishra Mehmet ?zger Vijay P. Singh 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(4):517-535
Climate model simulations for the twenty-first century point toward changing characteristics of precipitation. This paper
investigates the impact of climate change on precipitation in the Kansabati River basin in India. A downscaling method, based
on Bayesian Neural Network (BNN), is applied to project precipitation generated from six Global Climate Models (GCMs) using
two scenarios (A2 and B2). Wet and dry spell properties of monthly precipitation series at five meteorologic stations in the
Kansabati basin are examined by plotting successive wet and dry durations (in months) against their number of occurrences
on a double-logarithmic paper. Straight-line relationships on such graphs show that power laws govern the pattern of successive
persistent wet and dry monthly spells. Comparison of power-law behaviors provides useful interpretation about the temporal
precipitation pattern. The impact of low-frequency precipitation variability on the characteristics of wet and dry spells
is also evaluated using continuous wavelet transforms. It is found that inter-annual cycles play an important role in the
formation of wet and dry spells. 相似文献
65.
This study describes the stratigraphic and palaeoenvironmental significance of the Lower-“middle” Oligocene sediments based on the fauna from the Delikarkas? Formation and the microflora from the ?ncesu Formation of the ?ncesu area (northern part of the western Taurides, Isparta province, Turkey). In the area, the Oligocene sediments show a regressive succession, which begins with the limestones of the Delikarkas? Formation indicating marine conditions followed by conglomerates, sandstones and coaly mudstones of alluvial and fluvial (shallow marine-continental) origin. A well preserved foraminiferal assemblage including Nummulites intermedius, Nummulites vascus and Halkyardia maxima proves an Early Oligocene age for the Delikarkas? Formation. Due to palynological markers such as Boehlensipollis hohli, Slowakipollis hippophaëoides, Dicolpopollis kockelii, Magnolipollis neogenicus ssp. minor, Plicapollis pseudoexcelsus, Caryapollenites simplex and Intratriporopollenites instructus the ?ncesu Formation, which concordantly rests on the Delikarkas? Formation, may be assigned to the Early-“middle” Oligocene. From the palynomorph assemblage, three zones have been recognised according to abundance of species. Zone 1 is characterized by predominance of C. simplex and Momipites punctatus and rarely presence of tricolpate and tricolporate pollen. Zone 2 consists mainly of Inaperturopollenites dubius, Leiotriletes maxoides ssp. maximus, Verrucatosporites favus, Verrucatosporites alienus and infrequently marine dinoflagellate cysts. Zone 3 is characterized by a high percentage of ferns such as Echinatisporis?chattensis and Polypodiaceoisporites saxonicus. The presence of marine dinoflagellate cysts like Apectodinium sp. and Cleistosphaeridium sp., back-mangrove elements such as Acrostichum aureum and lepidocaryoid palms (e.g. Longapertites discordis, Longapertites punctatus and Longapertites psilatus) in the sediments of the ?ncesu Formation imply coastal or near-coastal conditions. Terrestrial palynomorphs in more inland settings were transported by running water towards the sea. Conifers are represented by poorly preserved and rare pollen grains of Pityosporites, Cathayapollis and Piceapollis which may have been transported by wind. In this study, the terrestrial climate of the ?ncesu Formation is also discussed on the basis of the Coexistence Approach method. The climate was warm at the coast (over 20 °C), as evidenced by A. aureum and lepidocaryoid palms, whereas there was a mean annual temperature of 17.2–17.4 °C must be assumed for the upland environment(s). 相似文献
66.
The effect of welding degree on geotechnical properties of an ignimbrite flow unit: the Bitlis castle case (eastern Turkey) 总被引:1,自引:0,他引:1
Tamer Koralay Mehmet ?zkul Halil Kumsar Sefer Beran ?elik Kadir Pekta? 《Environmental Earth Sciences》2011,64(3):869-881
Ignimbrites are associated with nearly most of the world’s volcanoes and are defined as a deposit from pyroclastic density
currents. They consist predominantly of pumiceous lapilli and blocks, and glass shards, which shows evidence of having been
emplaced as a concentrated hot and dry particulate flow. These rocks are widely used as building stone especially in ancient
buildings. Bitlis valley is covered by ignimbritic products, derived from Nemrut stratovolcano, one of the significant volcanic
centers in Eastern Anatolia. The Bitlis ignimbrite is separated into lower level (LL), middle level (ML) and upper level (UL)
according to color, welding degree and structural features. All three levels were used extensively in many parts of the Bitlis
castle as masonry materials. Studies were carried out on mineralogical and geochemical composition and on physical and mechanical
properties of the ignimbrites. In addition, a freeze–thaw cycle test was executed. There are no considerable differences in
mineralogical composition among the levels of ignimbrite. All levels contain plagioclase, sanidine, pyroxene, and opaque mineral.
In addition, anorthoclase and quartz are seen. In general, the LL of ignimbrite shows relic perlitic and eutaxitic texture,
whereas eutaxitic and vesicular texture are commonly developed in the ML and UL, respectively. Lower, middle, and upper level
ignimbrite samples display similar and limited compositional spread in terms of major oxide elements. They have trachyte composition.
Building stones can be classified according to mineralogy, mechanical and physical properties and processing types. Mechanical
and physical properties are very important with respect to stone quality/durability. The mechanical and physical properties
of the ignimbrites are controlled by the welding degree. It was found that increasing welding degree from UL to LL correlates
with increasing density, compressive strength and slake durability index and with decreasing porosity. The Bitlis ignimbrites
have turned out as susceptible to freeze–thaw cycles. 相似文献
67.
Maren Brehme Traugott Scheytt Mehmet Çelik Uğur Erdem Dokuz 《Environmental Earth Sciences》2011,63(6):1395-1408
The degradation of ground water quality due to human activities is a widespread environmental problem. Furthermore, coastal aquifers are threatened by sea water intrusion as a result of increasing water exploitation. The investigation area near Dörtyol is located at the Mediterranean coast, southern Turkey, and dominated by agricultural land use. Drinking, domestic and agricultural purposes require different amounts of uncontaminated water. In this study the hydrogeological characteristics of the coastal plain were investigated. Discharge and ground water level measurements as well as geological investigations were undertaken in field in addition to anion and cation analyses of ground and surface water. The results show geological and anthropogenic influence on ground and surface water composition. In spite of a large number of wells in the coastal area sea water intrusion was not detected. With the goal of devising sustainable water use regulations, more emphasis and research needs to be directed to the long-term observation of ground and surface water quality as well as the detailed investigation of hydraulic characteristics of the local aquifer. 相似文献
68.
Comparative analysis of fuzzy inference systems for water consumption time series prediction 总被引:1,自引:0,他引:1
Two types of fuzzy inference systems (FIS) are used for predicting municipal water consumption time series. The FISs used include an adaptive neuro-fuzzy inference system (ANFIS) and a Mamdani fuzzy inference systems (MFIS). The prediction models are constructed based on the combination of the antecedent values of water consumptions. The performance of ANFIS and MFIS models in training and testing phases are compared with the observations and the best fit model is identified according to the selected performance criteria. The results demonstrated that the ANFIS model is superior to MFIS models and can be successfully applied for prediction of water consumption time series. 相似文献
69.
Design and commissioning of a laminar soil container for use on small shaking tables 总被引:2,自引:0,他引:2
This paper describes the design, fabrication and commissioning of a single axis laminar shear box for use in seismic soil–structure interaction studies. A laminar shear box is a flexible container that can be placed on a shaking table to simulate vertical shear-wave propagation during earthquakes through a soil layer of finite thickness. The laminar shear box described in this paper was designed to overcome the base shear limitations of a small shaking table at The University of Western Ontario. The design details of the box are provided in addition to results of dynamic tests performed to commission the box. A synthetic clay comprising sodium bentonite mixed with diluted glycerin was used as the model soil and 1-G similitude theory was employed to maintain model to prototype similarity. The model soil was compacted into the container in lifts to achieve soil stiffness that increased with depth. A series of shaking table tests and numerical analyses that were performed to study the performance of the laminar box and non-linear seismic behavior of the model clay are described. The results of this study show that the laminar box does not impose significant boundary effects and is able to maintain 1-D soil column behavior. In addition, the dynamic behavior of the model clay during scaled model tests was found to be consistent with the behavior measured during cyclic laboratory tests. 相似文献
70.
Pelin Tohumcu Özener Kutay Özaydın Mehmet M. Berilgen 《Bulletin of Earthquake Engineering》2009,7(1):199-219
This paper presents the results of shaking table model tests which were carried out to investigate the pore water pressure
generation and related liquefaction mechanism in layered sand deposits. The experiments were performed on uniform sand columns,
silt interlayered sand columns and two layered sand columns deposited at various relative densities and subjected to different
input excitations. During the experiments excess pore water pressures were measured by pore pressure transducers installed
at three different depths and, surface settlements and thickness of water film developed under less permeable inclusions were
measured by a digital camera. The experimental results are discussed and compared to demonstrate the effects of relative density,
input acceleration and presence of a silt seam on the generation of excess pore water pressure in sand deposits subjected
to dynamic loading. The results showed that the presence of a less permeable silt interlayer within the sand deposit and existence
of a loose sand layer underlying dense sand deposits can have significant effect on the pore water pressure generation mechanism. 相似文献