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221.
222.
Examining Source-Receptor Relationships for Mercury in Scandinavia Modelled and Empirical Evidence 总被引:1,自引:0,他引:1
Munthe John Kindbom Karin Kruger Olaf Petersen Gerhard Pacyna Jozef Iverfeldt Åke 《Water, Air, & Soil Pollution: Focus》2001,1(3-4):299-310
The atmosphere remains the major source of mercuryin Swedish ecosystems. Since the late eighties,atmospheric emissions of mercury have drasticallydecreased in Europe. Wet deposition of mercury hasdecreased over the last decade but still exhibitsa clear south-to-north gradient, greatlyinfluenced by source areas in northern and centralEurope. The decreases in emissions can beattributed to both direct measures to close knownpoint sources and a declining economy and energyconsumption in many East European countries.Further reductions of mercury emissions willrequire that other source categories such asindirect emissions from mercury-containingproducts and crematories are be considered. 相似文献
223.
A large-scale experiment on mass transfer of trichloroethylene from the unsaturated zone of a sandy aquifer to its interfaces 总被引:4,自引:0,他引:4
Jellali S Benremita H Muntzer P Razakarisoa O Schäfer G 《Journal of contaminant hydrology》2003,60(1-2):31-53
A large-scale experiment was conducted to investigate the transport of trichloroethylene (TCE) vapors in the unsaturated zone and to determine the mass transfer to the groundwater and the atmosphere. The experiment involved injection of 5 1 of TCE in the unsaturated zone under controlled conditions, with multidepth sampling of gas and water through the unsaturated zone and across the capillary zone into underlying groundwater. The mass transfer of TCE vapors from the vadose zone to the atmosphere was quantified using a vertical flux chamber. A special soil water sampler was used to monitor transport across the capillary fringe. Experimental data indicated that TCE in the unsaturated zone was mainly transported to the atmosphere and this exchange reduced significantly the potential for groundwater pollution. The maximum measured TCE flux to the atmosphere was about 3 g/m(2)/day. Observed and calculated fluxes based on vertical TCE vapor concentration gradients and Fick's law were in good agreement. This confirms that TCE vapor transport under the experimental conditions was governed essentially by molecular diffusion. TCE vapors also caused a lower, but significant contamination of the underlying groundwater by dispersion across the capillary fringe with a corresponding maximum flux of about 0.1 g/m(2)/day. This mass transfer to groundwater is partly uncertain due to an inadvertent entry of some nonaqueous phase liquid (NAPL) from the source area into the saturated zone. Application of an analytical solution to estimate the TCE flux from the unsaturated zone to the groundwater indicated that this phenomenon is not only influenced by molecular diffusion but also by vertical dispersion. The mass balance indicates that, under the given experimental conditions (e.g. proximity of the source emplacement relative to the soil surface, relatively high permeable porous medium), nearly 95% of the initial TCE mass was transferred to the atmosphere. 相似文献
224.
Gerhard Lammel V. S. Semeena Francesca Guglielmo Tatjana Ilyina Adrian Leip 《Environmental Sciences Europe》2006,18(4):254-261
Background, Aim and Scope
Many environmental pollutants are slowly degrading (persistent) and very mobile. They are semivolatile, i.e. they are partitioned between the environmental media of soil, water and air, and undergo long-range transport. The combined action of climate and substance properties determines the distributions and fate of these substances, among them as the persistent organic pollutants (POPs), other pesticides and industrial chemicals.Main Features
Multicompartment chemistry-transport models are under development in order to study environmental exposure models.Results
The investigation of transport and fate of some POPs on the global scale has emphasized the significance of historically explicit and geo-referenced simulations for substance distributions, persistence and long-range transport potential. Apart from the substance properties, it is the regional climate which is most important. This was illustrated by studies into the regional cycling of DDT and γ-HCH in selected tropical and extra-tropical regions.Discussion
The isolation of individual steps of subsequent cycles of emission, transport and deposition (a so-called grasshopper effect) in model experiments shows the potential to elucidate the complex superposition of substance properties and environmental conditions, variable in time and space.Conclusions
The results suggest that the grasshopper effect enhances the long-range transport potential, but is not required to explain an accumulation in polar regions (at least for γ-HCH).Perspectives
A number of relevant scientific questions should be addressed by exposure modelling. 相似文献225.
Johann Fellner Gernot Döberl Gerhard Allgaier Paul H. Brunner 《Waste management (New York, N.Y.)》2009,29(6):1844-1851
Investigations into laboratory reactors and landfills are used for simulating and predicting emissions from municipal solid waste landfills. We examined water flow and solute transport through the same waste body for different volumetric scales (laboratory experiment: 0.08 m3, landfill: 80,000 m3), and assessed the differences in water flow and leachate emissions of chloride, total organic carbon and Kjeldahl nitrogen. The results indicate that, due to preferential pathways, the flow of water in field-scale landfills is less uniform than in laboratory reactors. Based on tracer experiments, it can be discerned that in laboratory-scale experiments around 40% of pore water participates in advective solute transport, whereas this fraction amounts to less than 0.2% in the investigated full-scale landfill. Consequences of the difference in water flow and moisture distribution are: (1) leachate emissions from full-scale landfills decrease faster than predicted by laboratory experiments, and (2) the stock of materials remaining in the landfill body, and thus the long-term emission potential, is likely to be underestimated by laboratory landfill simulations. 相似文献
226.
Markus Hengstschläger Dieter Bettelheim Regina Drahonsky Josef Deutinger Gerhard Bernaschek 《黑龙江环境通报》2001,21(6):477-480
Marker chromosomes are supernumerary chromosomes of unknown origin and are seldom found in prenatal diagnosis. Application of fluorescent in situ hybridization (FISH) allows the identification of the chromosomal origin of markers. Estimation of the risk of an abnormal phenotype outcome can be enabled by collecting data on phenotypes associated with markers of the same chromosomal origin. So far only very few cases of prenatal diagnosis of de novo supernumerary markers derived from chromosome 16 have been reported. Here the prenatal diagnosis of a de novo supernumerary marker chromosome 16 is described and the relevant literature discussed. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
227.
Climate change is predicted to increase temperature extremes and thus thermal stress on organisms. Animals living in hot deserts are already exposed to high ambient temperatures (T a) making them especially vulnerable to further warming. However, little is known about the effect of extreme heat events on small desert mammals, especially tree-roosting microbats that are not strongly protected from environmental temperature fluctuations. During a heat wave with record T as at Sturt National Park, we quantified the thermal physiology and behaviour of a single free-ranging little broad-nosed (Scotorepens greyii, henceforth Scotorepens) and two inland freetail bats (Mormopterus species 3, henceforth Mormopterus) using temperature telemetry over 3 days. On 11 and 13 January, maximum T a was ~45.0 °C, and all monitored bats were thermoconforming. On 12 January 2013, when T a exceeded 48.0 °C, Scotorepens abandoned its poorly insulated roost during the daytime, whereas both Mormopterus remained in their better insulated roosts and were mostly thermoconforming. Maximum skin temperatures (T skin) ranged from 44.0 to 44.3 °C in Scotorepens and from 40.0 to 45.8 °C in Mormopterus, and these are the highest T skin values reported for any free-ranging bat. Our study provides the first evidence of extensive heat tolerance in free-ranging desert microbats. It shows that these bats can tolerate the most extreme T skin range known for mammals (3.3 to 45.8 °C) and delay regulation of T skin by thermoconforming over a wide temperature range and thus decrease the risks of dehydration and consequently death. 相似文献
228.
Sebastian Busse Dominik Lutter Gerhard Heldmaier Martin Jastroch Carola W. Meyer 《Die Naturwissenschaften》2014,101(11):1003-1006
The grey short-tailed opossum, Monodelphis domestica, has been an established research animal for more than five decades, but relatively, little is known about its thermophysiology. Here we studied core body temperature (T b) and metabolic rate (MR) of female adult M. domestica housed in the laboratory at an ambient temperature (T a) of 26 °C. In expanding previous reports, the average recorded core T b of M. domestica was 34.3 °C. The T b of an individual M. domestica can drop below 30 °C (minimal T b: 28.6 °C) accompanied by a reduction in MR of up to 52 % even while having ad libitum access to food. These findings demonstrate for the first time the presence of spontaneous torpor in M. domestica. Metabolic suppression at relatively high T a and T b furthermore broadens our perspective on the use of torpor as a metabolic strategy not just restricted to cold climates. 相似文献
229.
Caroline Regina Schöner Michael Gerhard Schöner Gerald Kerth 《Behavioral ecology and sociobiology》2010,64(12):2053-2063
Many bat species regularly need to find new day roosts as they require numerous shelters each breeding season. It has been
shown that bats exchange information about roosts among colony members, and use echolocation and social calls of conspecifics
in order to find roosts. However, it is unclear if wild bats discriminate between social calls of conspecifics and other bat
species while searching for roosts. Furthermore, the extent that bats are attracted to potential roosts by each of these two
call types is unknown. We present a field experiment showing that social calls of conspecifics and other bat species both
attract bats to roosts. During two summers, we played back social calls of Bechstein’s bats (Myotis bechsteinii) and Natterer’s bats (Myotis nattereri) from different bat boxes that can serve as roosts for these species. All experimental bat boxes were monitored with infrared
video to identify the approaching bat species. Three species (M. bechsteinii, M. nattereri, and Plecotus auritus) approached the boxes significantly more often during nights when bat calls were played compared to nights without playbacks.
Bechstein’s bats and Natterer’s bats were both more attracted to social calls of conspecifics than of the other species, whereas
P. auritus did not discriminate between calls of either Myotis species. Only Bechstein’s bats entered experimental boxes and only at times when calls from conspecifics were played. Our
findings show that wild bats discriminate between social calls of conspecifics and other bat species although they respond
to both call types when searching for new roosts. 相似文献
230.
An account is given about the development of the gametes of the holopelagic coronate scyphomedusa Periphylla periphylla (Péron and Lesueur 1809). The gonads of the species are complex and differ from those thus far described in Scyphozoa in
having this characteristic composition of trophocytes, follicle cells, gamete-releasing pores, mucus cells, and resorption
cells. Our results differ from those of previous coronate studies with respect to the contact of the oocytes with the gonad
tissue throughout the duration of development. Among the Medusozoa, follicle cells have thus far been considered as an apomorphy
for the Staurozoa, but their presence in the Scyphozoa casts some doubts on this assumption. From morphological structure
and examination of the gonads and gametes, it can be deduced that P. periphylla has true organs and that gamete release is continuous. These results supplement our knowledge of the reproductive biology
of this mesopelagic species. 相似文献