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排序方式: 共有198条查询结果,搜索用时 953 毫秒
51.
Dušan Žagar Nataša Sirnik Matjaž Četina Milena Horvat Jože Kotnik Nives Ogrinc Ian M. Hedgecock Sergio Cinnirella Francesco De Simone Christian N. Gencarelli Nicola Pirrone 《Environmental science and pollution research international》2014,21(6):4081-4094
Mass balance of contaminants can provide useful information on the processes that influence their concentrations in various environmental compartments. The most important sources, sinks and the equilibrium or non-equilibrium state of the contaminant in individual environmental compartments can also be identified. Using the latest mercury speciation data, the results of numerical models and the results of recent studies on mercury transport and transformation processes in the marine environment, we have re-evaluated the total mercury (HgT) mass balance in the Mediterranean Sea. New calculations have been performed employing three distinct marine layers: the surface layer, the thermocline and the deep sea. New transport mechanisms, deep water formation and density-driven sinking and upwelling, were included in the mass balance calculations. The most recent data have even enabled the calculation of an approximate methylmercury (MeHg) mass balance. HgT is well balanced in the entire Mediterranean, and the discrepancies between inputs and outputs in individual layers do not exceed 20 %. The MeHg balance shows larger discrepancies between gains and losses due to measurement uncertainties and gaps in our knowledge of Hg species transformation processes. Nonetheless, the main sources and sinks of HgT (deposition and evasion) and MeHg (fluxes from sediment, outflow through the Gibraltar Strait) are in accordance with previous studies on mercury in the Mediterranean Basin. Mercury in the Mediterranean fish harvest is the second largest MeHg sink; about 300 kg of this toxic substance is consumed annually with sea food. 相似文献
52.
A. Alexiou P. Kostarakis V. N. Christofilakis T. Zervos A. A. Alexandridis K. Dangakis C. Soras V. V. Petrović B. M. Kolundžija A. R. Dordević 《The Environmentalist》2005,25(2-4):215-221
Summary The performance of a cellular phone commercial helical antenna at 900~MHz band, both in free space and in the presence of
a human head phantom was studied. Numerical simulation of the phone model for the latter case has been performed giving 3D
radiation diagrams. The effect of the phantom head on radiation diagrams is presented. The relative amount of the EM power
absorbed in the head was obtained for several distances of the phone. Measurements were carried out in a RF anechoic chamber
using standard horn antennas and a calibrated measuring system. Absolute radiation patterns of the antenna gain were obtained
in the three principal planes. Significant reduction of the absorbed power could be achieved just by moving the phone 1 cm
away from the head. 相似文献
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55.
František Vožeh Antonín Doněk Jan Cendelín Ivana Korelusová Jan Vrba 《The Environmentalist》2007,27(4):501-504
The effect of long-term exposure to high frequency electromagnetic field (HF EMF) on some somatic and neural characteristics
was studied in neurodefective Lurcher mutant (+/Lc) and normal wild type mice (+/+). Both newborn and young adult (3 months)
animals derived from two strains (C3H, B6CBA) were exposed to HF EMF (870 MHz) from 1st to 21st day or from 91st to 120th
day respectively. In animals of both groups and controls we observed the development of body weight. Moreover, in the HF EMF
exposed adult B6CBA animals we studied spatial learning ability, motor functions and the CNS excitability. To investigate
specific energy absorption rate (SAR) in experimental animals we have done the basic 3D calculations of the electromagnetic
energy distribution in the simplified model of the mouse. The HF EMF exposed animals exhibited mild differences of body weight
between them and unexposed controls. The long-term exposure to HF EMF did not significantly influence the ability to learn
in the Morris water maze. However, significant lower swimming speed was found in the irradiated +/Lc as well as lower motor
activity of +/+ in the open field when compared to controls. No significant differences were found between HF EMF irradiated
animals and controls in examination of the CNS excitability and motor functions. 相似文献
56.
Irena Ciglenečki Srđan Pichler Esad Prohić Božena Ćosović 《Water, Air, & Soil Pollution: Focus》2006,6(5-6):537-545
Geochemical, mineralogical and sedimentological analyses were carried out to contrast two different sites (respectively characterized
by permanently oxic and anoxic conditions) in a small, meromictic, seawater lake. In fact, due to relatively high organic
matter content, and reduced water exchange, the Rogoznica Lake has almost permanent anoxic conditions below the depth of 12 m,
where sediment can be considered an anoxic–sulphidic sedimentary environment. Different water column and sediments redox conditions
affect the distribution and speciation of major redox-sensitive metals (Fe, Mn, Mo), reduced sulphur species (RSS) and dissolved
organic C (DOC). Trace metals, especially those that accumulate in anoxic–sulphidic environments (Fe, Mo) showed a marked
enrichment in the solid phase, whereas the low solubility of sulphides leads to low porewater concentrations. The relatively
high sedimentary enrichment of Mo (up to 81 mg/kg) also confirms highly anoxic conditions within the Rogoznica Lake sediments.
Results clearly show that chemical species within the sediments will tend towards equilibrium between porewater and solid
phase according the prevailing environment conditions such as redox, pH, salinity, DOC. 相似文献
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58.
Journal of Material Cycles and Waste Management - Recycling possibilities were evaluated for a composite waste composed of glass fiber reinforced polyester bound to a layer of crosslinked... 相似文献
59.
The architecture of vertical aerial orb webs may be affected by spider size and gravity or by the available web space, in
addition to phylogenetic and/or developmental factors. Vertical orb web asymmetry measured by hub displacement has been shown
to increase in bigger and heavier spiders; however, previous studies have mostly focused on adult and subadult spiders or
on several size classes with measured size parameters but no mass. Both estimations are suboptimal because (1) adult orb web
spiders may not invest heavily in optimal web construction, whereas juveniles do; (2) size class/developmental stage is difficult
to estimate in the field and is thus subjective, and (3) mass scales differently to size and is therefore more important in
predicting aerial foraging success due to gravity. We studied vertical web asymmetry in a giant orb web spider, Nephila pilipes, across a wide range of size classes/developmental stages and tested the hypothesis that vertical web asymmetry (measured
as hub displacement) is affected by gravity. On a sample of 100 webs, we found that hubs were more displaced in heavier and
larger juveniles and that spider mass explained vertical web asymmetry better than other measures of spider size (carapace
and leg lengths, developmental stage). Quantifying web shape via the ladder index suggested that, unlike in other nephilid
taxa, growing Nephila orbs do not become vertically elongated. We conclude that the ontogenetic pattern of progressive vertical web asymmetry in
Nephila can be explained by optimal foraging due to gravity, to which the opposing selective force may be high web-building costs
in the lower orb. Recent literature finds little support for alternative explanations of ontogenetic orb web allometry such
as the size limitation hypothesis and the biogenetic law. 相似文献
60.
Davor Antanasijević Viktor Pocajt Ivanka Popović Nebojša Redžić Mirjana Ristić 《Sustainability Science》2013,8(1):37-46
The feasibility of modeling municipal waste generation (MWG) for countries at different levels of development using artificial neural networks (ANN) and selected generic indicators of sustainability was investigated. The main goals of this research were to develop ANN-based models for predicting MWG, to overcome the problem of incomplete MWG data, which is notable in developing countries, and to provide a new method for the planning of municipal solid waste management systems as well as for the simulation of various other scenarios. Data from 26 European countries was used in this study as training, test and validation datasets for the developing of ANN models. Since this kind of modeling is particularly important for developing countries where MWG data is missing or incomplete, emphasis was placed on modeling of MWG for Bulgaria and Serbia. Based on a comparison of actual MWG data with predictions given by the model, we show that ANNs can be applied successfully to modeling and forecasting MWG on a national scale. Moreover, the scope for possible application of the model is broad, since it uses generic indicators of sustainability such as gross domestic product, domestic material consumption and resource productivity, and performs well for countries with highly diversified levels of economic development, industrial structure, productivity and output. 相似文献