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51.
Jann Peyrat Małgorzata Braun Christian Dolnik Maike Isermann Hartmut Roweck 《Journal of Coastal Conservation》2009,13(4):235-246
Coastal dune ecosystems are among the most dynamic habitats with high conservation value in Europe but are also under strong
anthropogenic pressure regarding coastal protection and recreation. Hence, it is of high importance to know about long-term
natural and anthropogenic changes and development of protected dune habitats for nature conservation, as well as for coastal
management. This paper aims to identify the vegetation dynamics on the Łeba Bar/Poland over a period of 74 years by cartometric
comparison using modern Geographical Information System (GIS). To quantify the rate of vegetation dynamics two aerial photographs
dating from 1932 and 2006 were digitalized and analyzed with GIS to produce digital vegetation maps. Information about decrease,
increase and stability of vegetation types of this area are discussed. The results show that there has been a clear reduction
in the total area of bare sand and a considerable increase of woodlands and dense grass communities. Nevertheless, the remaining
extensive drift sand areas and deflation hollows on the Łeba Bar offer one of the most important habitats for pioneer vegetation
on bare sand of migrating dunes and dunes at the Southern Baltic coast. The present work proved the need to observe the future
development of the vegetation communities and to implement management measures to maintain the dynamic of this unique dune
landscape. 相似文献
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Nuclear Magnetic Resonance (NMR) spectroscopy was applied to directly study the interactions between the alkaline phosphatase enzyme (AP) and two different humic acids from a volcanic soil (HA-V) and a Lignite deposit (HA-L). Addition of humic matter to enzyme solutions caused signals broadening in 1H-NMR spectra, and progressive decrease and increase of enzyme relaxation (T1 and T2) and correlation (τC) times, respectively. Spectroscopic changes were explained with formation of ever larger weakly-bound humic–enzyme complexes, whose translational and rotational motion was increasingly restricted. NMR diffusion experiments also showed that the AP diffusive properties were progressively reduced with formation of large humic–enzyme complexes. The more hydrophobic HA-L affected spectral changes more than the more hydrophilic HA-V. 1H-NMR spectra also showed the effect of progressively greater humic–enzyme complexes on the hydrolysis of an enzyme substrate, the 4-nitrophenyl phosphate disodium salt hexahydrate (p-NPP). While AP catalysis concomitantly decreased NMR signals of p-NPP and increased those of nitrophenol, addition of humic matter progressively and significantly slowed down the rate of change for these signals. In agreement with the observed spectral changes, the AP catalytic activity was more largely inhibited by HA-L than by HA-V. Contrary to previous studies, in which humic–enzyme interactions were only indirectly assumed from changes in spectrophotometric behavior of enzyme substrates, the direct measurements of AP behavior by NMR spectroscopy indicated that humic materials formed weakly-bound host–guest complexes with alkaline phosphatase, and the enzyme catalytic activity was thereby significantly inhibited. These results suggest that the role of extracellular enzymes in soils may be considerably reduced when they come in contact with organic matter dissolved in the soil solution. 相似文献
57.
Results of analysis of 7Be, 137Cs and 210Pb on aerosol filters carried out from 1998 to 2010 in Monaco show that a weak correlation between activity concentrations of these radionuclides in the atmosphere and meteorological parameters has been found for 7Be and temperature (r = 0.50), 210Pb and temperature and humidity (r = 0.43 and 0.41, respectively), and 137Cs and precipitation (r = 0.51). The minimum and maximum 7Be activity concentrations were observed during 2000 and 2009, corresponding with the maximum and minimum solar activity, respectively. The maximum 137Cs activity concentration found in May-June 1998 was due to the accident at Algeciras in Spain. The deposition velocities of 7Be, 137Cs and 210Pb depended on the precipitation rate, and attained maximum values during dry seasons. The investigated radionuclides may be used as atmospheric tracers, especially in long-term periods. 相似文献
58.
For wide-area atmospheric monitoring, krypton-85 is the best indicator for clandestine plutonium separations. The detection and false alarm rates were determined from weekly samples at five different distances from the Karlsruhe reprocessing plant between 1985 and 1988. The detection rate for the separation of 4 kg of plutonium per week was found to be as high as 80-90% at a distance of less than 1 km, 70% at 5 km, 40% at 39 km, and 15% at 130 km. At distances up to 40 km, the false alarm rate is less than 3.5%. On average, the fuel released 28 TBq krypton-85 per kg plutonium. For weapons-grade plutonium, the krypton signal would be lower by a factor of 2. Hence, the given percentages correspond to the detection probabilities for the separation of a significant quantity (8 kg) of plutonium per weekly sample under the specific meteorological conditions of the WAK. The minimum separation rates that could have been detected are 2 gram of weapons-grade plutonium per week at a distance of less than 1 km, 40 g/week at 5 km, 200 g/week at 39 km, and 1000 g/week at 130 km. 相似文献
59.
Temperature-dependent ranges of coexistence in a model of a two-prey-one-predator microbial food web
Mar Monsonís Nomdedeu Christine Willen Andre Schieffer Hartmut Arndt 《Marine Biology》2012,159(11):2423-2430
The objective of our study was to analyze the effects of temperature on the population dynamics of a three-species food web consisting of two prey bacteria (Pedobacter sp. and Acinetobacter johnsonii) and a protozoan predator (Tetrahymena pyriformis) as model organisms. We assessed the effects of temperature on the growth rates of all three species with the objective of developing a model with four differential equations based on the experimental data. The following hypotheses were tested at a theoretical level: Firstly, temperature changes can affect the dynamic behavior of a system by temperature-dependent parameters and interactions and secondly, food web response to temperature cannot be derived from the single species temperature response. The main outcome of the study is that temperature changes affect the parameter range where coexistence is possible within all three species. This has significant consequences on our ideas regarding the evaluation of effects of global warming. 相似文献
60.
Björn P. Zietz Patrick Paufler Barbara Keßler-Gaedtke Hartmut Dunkelberg 《Environmental Sciences Europe》2001,13(3):153-157
There are many acute and chronic adverse effects of lead on human beings. This is especially true for infants and children. In Germany, the intake of lead through drinking water is commonly due to metal corrosion of the user’s plumbing. In the last years and decades, many lead pipes in Germany were replaced by pipes made of alternative materials. The aim of this study was to assess the present state of drinking water contamination and the resulting lead exposure in infants, the most sensitive population group. For this purpose, mothers of newborn babies were offered a free examination of their drinking water. After a written declaration of consent had been received, two composite samples collected during the day were obtained from the families. The samples were analyzed for their lead concentration using atomic absorption spectrometry. A total of 2109 samples from house holds in the area of Berlin, Germany were collected. From the first composite samples 5.6% and 7.0% of the second composite samples demonstrated lead concentrations higher than 0.01 mg/l (recommended limit of the WHO). 0.95% of the first composite samples and 1.3% of the second composite samples had concentrations above the limit of the German drinking water regulation (0.04 mg/l). The highest measured lead concentrations is the first and second composite samples were 0.19 and 0.13 mg/l, respectively. By region, the suburbs of Charlottenburg, Neukölln, Schöneberg, Wilmersdorf and Zehlendorf were particularly severley affected with more than 10% and their samples being elevated above 0.01 mg/l. 相似文献