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161.
Recent state of forest biodiversity at the European level was reviewed and analysed with respect to the current requirements from the environmental policies as well as with respect to scientific findings in the field. The analysis reveals the main deficits and development needs, and outlines some possible courses for future action. Specific reference is given to the boreal, Atlantic and continental regions of Europe.Especially the operational definition of biodiversity, the selection of the scale and consideration of the most appropriate indicators and data collection methods are of primary importance when defining a monitoring approach. The results of a recent assessment at national scale contribute to an improved understanding, but show some shortcomings with respect to the level of detail. The high variability of the distribution, structure and composition of forests in Europe can be comprised only partially when the monitoring follows national borders. To detect changes in time for corrective measures and to be able to apply appropriate threshold values for biodiversity indicators a more detailed approach, which takes into account different bio-geographical regions and forest ecosystem types, is needed. Technically, this could be based on aggregation national forest inventories or European-wide sampling scheme combined with remote sensing data and distinct forest types or categories. 相似文献
162.
The effects of iron oxides and organic matter on the partitioning and chemical lability of U and Ni were examined for contaminated riparian sediments from the U.S. Department of Energy's Savannah River Site. In sequential extractions of four sediments that ranged from 12.7 to 82.2 g kg(-1) in organic carbon, U was found almost exclusively in moderately labile fractions (93% in acid-soluble + organically bound). Nickel was distributed across all operationally defined fractions, including substantial amounts in the very labile fractions (4-15% in water-soluble + exchangeable), noncrystalline and crystalline iron oxides (38-49%), and in the nonlabile residual fraction (25-34%). Aqueous U concentrations in 1:1 sediment-water extracts were highly correlated to dissolved organic carbon (DOC) (R2 = 0.96; p < 0.0001) and ranged from 29 to 410 microg L(-1). Aqueous concentrations of Ni exceeded U by two to three orders of magnitude (124-2227 microg L(-1)) but were not correlated with DOC (R2 = 0.04; p = 0.53). Partitioning and solubility trends suggest that Ni availability is controlled primarily by iron-oxide phases, whereas U availability is dominated by naturally occurring organic carbon. Discrete mineral phases were also identified as nonlabile reservoirs of anthropogenic metals. In spite of comparably high sediment concentrations, Ni appears to be significantly more available than U in riparian sediments and therefore warrants greater consideration in terms of environmental consequences (i.e., transport, biological uptake, and toxicity). 相似文献
163.
Since the announcement by Fleischmann and Pons that the excess enthalpy generated in the negatively polarized Pd–D-D2O system was attributable to nuclear reactions occurring inside the Pd lattice, there have been reports of other manifestations
of nuclear activities in this system. In particular, there have been reports of tritium and helium-4 production; emission
of energetic particles, gamma or X-rays, and neutrons; as well as the transmutation of elements. In this communication, the
results of Pd–D co-deposition experiments conducted with the cathode in close contact with CR-39, a solid-state nuclear etch
detector, are reported. Among the solitary tracks due to individual energetic particles, triple tracks are observed. Microscopic
examination of the bottom of the triple track pit shows that the three lobes of the track are splitting apart from a center
point. The presence of three α-particle tracks outgoing from a single point is diagnostic of the 12C(n,n′)3α carbon breakup reaction and suggests that DT reactions that produce ≥9.6 MeV neutrons are occurring inside the Pd
lattice. To our knowledge, this is the first report of the production of energetic (≥9.6 MeV) neutrons in the Pd–D system.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
164.
Rolón Eugenia Rosso Juan José Mabragaña Ezequiel Tripodi Pamela Bavio Marta Bidone Camila Volpedo Alejandra V. Avigliano Esteban 《Environmental science and pollution research international》2022,29(39):58843-58868
Environmental Science and Pollution Research - Environmental pollution affects the quality of the natural environment where major and trace elements have been commonly found to accumulate in biotic... 相似文献
165.
氮沉降的全球化:对于陆地生态系统的意义 总被引:56,自引:0,他引:56
Pamela Matson Kathleen A. Lohse Sharon J. Hall 《Ambio-人类环境杂志》2002,31(2):113-119
人类活动产生的氮(N),包括农田氮肥施肥和矿物燃料燃烧过程中所固定的氮,其来源和分布正在迅速地扩展到全球范围.这部分氮进入到陆地生态系统中,将会促进植物的生长,并产生过量的氮,最终通过淋溶和痕量气体排放的形式,增加了氮的损失.在某种情况下,还会导致物种组成的变化和生态系统功能的衰减.但并非所有的生态系统都对氯沉降具有类似的响应.它们的响应情况,取决于氮沉降的连续性、生态系统的类型,生态系统对氮的需求或保持能力、土地利用的历史、土壤状况、地形条件、气候背景以及氮沉降的速度、时间和类型等因素.我们认为,起重要作用的是:一些对人类影响具有显著意义的条件、一些控制生态系统响应变化的因素以及一些由于资料缺乏而使不确定性增大的地方. 相似文献