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排序方式: 共有101条查询结果,搜索用时 15 毫秒
21.
苔藓Lophozia ventricosa挥发油化学成分研究 总被引:1,自引:0,他引:1
采用水蒸气蒸馏法提取苔藓Lophozia ventricosa挥发油,用毛细管色谱法对挥发油进行了分析,采用归-化法确定各组分的相对含量,并用GC—MS联用技术对分离的化学成分进行鉴定.经计算机检索并结合文献调研,共鉴定出28个化合物,占挥发油总量的93.3%,其中含1个单萜、23个倍半萜(15个为含氧倍半萜)和1个二萜,主要成分为Maalioxide(45.6%)和Eudesma-4.(15),7(11)-dien-8-one(28.9%).图2表1参12 相似文献
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6 ha, or 6% of the country's total area. The environmental implications of this large-scale conversion have so far received
little attention; the present study examined some of these implications. A review of research on soil physical and chemical
aspects of the conversion of permanent grassland into arable land reveals that such a large-scale conversion may have considerable
effects upon the environment. For example, due to the mineralization of soil organic matter a release of NO3 and CO2 into the environment can be expected on the order of 10 t N and 100 t C per hectare. Environmentally equally severe, if not
worse, is the increased amount of surface runoff that can be expected from converted grassland soils in arable land during
winter because of surface sealing and soil compaction. This increased surface runoff, in combination with the runoff from
other farmland, may be one of the reasons for the growing frequency of floods along major German rivers in recent years. In
view of the lasting adverse environmental effects of permanent grassland conversion and the subsidized agricultural surpluses
in Germany today, we conclude that a reconversion of arable land into permanent grassland may be beneficial both environmentally
and economically. 相似文献
25.
Schoenmuth BW Pestemer W 《Environmental science and pollution research international》2004,11(5):331-339
BACKGROUND, AIM AND SCOPE: Problems of long-term existence of the environmental contaminant 2,4,6-trinitrotoluene (TNT) and necessities for the use of trees ('dendroremediation') in sustainable phytoremediation strategies for TNT are described in the first part of this paper. Aims of the second part are estimation of [14C]-TNT uptake, localisation of TNT-derived radioactivity in mature tree tissues, and the determination of the degree of TNT-degradation during dendroremediation processes. METHODS: Four-year-old trees of hybrid willow (Salix spec., clone EW-20) and of Norway spruce (Picea abies) were cultivated in sand or ammunition plant soil (AP-soil) in wick supplied growth vessels. Trees were exposed to a single pulse application with water solved [U-14C]-TNT reaching a calculated initial concentration of 5.2 mg TNT per kg dry soil. Two months after application overall radioactivity and extractability of 14C were determined in sand/soil, roots, stem-wood, stem-bark, branches, leaves, needles, and Picea May sprouts. Root extracts were analysed by radio TLC. RESULTS: 60 days after [14C]-TNT application, recovered 14C is accumulated in roots (70% for sand variants, 34% for AP-soil variant). 15-28% of 14C remained in sand and 61% in AP-soil. 3.3 to 14.4% of 14C were located in aboveground tree portions. Above-ground distribution of 14C differed considerably between the angiosperm Salix and the gymnosperm Picea. In Salix, nearly half of above-ground-14C was detected in bark-free wood, whereas in Picea older needles contained most of the above-ground-14C (54-69%). TNT was readily transformed in tree tissue. Approximately 80% of 14C was non-extractably bound in roots, stems, wood, and leaves or needles. Only quantitatively less important stem-bark of Salix and Picea and May shoots of Picea showed higher extraction yields (up to 56%). DISCUSSION: Pulse application of [14C]-TNT provided evidence for the first time that after TNT-exposure, in tree root extracts, no TNT and none of the known metabolites, mono-amino-dinitrotoluenes (ADNT), diaminonitrotoluenes (DANT), trinitrobenzene (TNB) and no dinitrotoluenes (DNTs) were present. Extractable portions of 14C were small and contained at least three unknown metabolites (or groups) for Salix. In Picea, four extractable metabolites (or groups) were detected, where only one metabolite (or group) seemed to be identical for Salix and Picea. All unknown extractables were of a very polar nature. CONCLUSIONS: Results of complete TNT-transformation in trees explain some of our previous findings with 'cold analytics', where no TNT and no ADNT-metabolites could be found in tissues of TNT-exposed Salix and Populus clones. It is concluded that 'cold' tissue analysis of tree organs is not suited for quantitative success control of phytoremediation in situ. RECOMMENDATIONS AND OUTLOOK: Both short rotation Salicaceae trees and conifer forests possess a dendroremediation potential for TNT polluted soils. The degradation capacity and the large biomass of adult forest trees with their woody compartments of roots and stems may be utilized for detoxification of soil xenobiotics. 相似文献
26.
Stephanie Hänsel Wilfried Küchler Jörg Matschullat 《Environmental Sciences Europe》2005,17(3):159-165
Goal and Background
Since consequences of global climate change include even contradicting directions and trends in different regions and seasons, regional studies are a necessity to understand regional problems and risks. Extreme precipitation is a highly variable climate element in time and space with serious economic and ecological impacts. The analysis of changes in the Saxonian precipitation characteristics is one constituent in our understanding of global climate change and regional climate-related risk assessment.Methods
Changes of regional precipitation patterns and their extremes were analysed based upon data from 21 stations in Saxony from 1934 to 2000. Eighteen stations delivered 50-year data sets (1951–2000) and three stations (Altmörbitz, Chemnitz, Neuhausen) delivered daily precipitation data over 67 years (1934–2000). Differentiated by season and half-year periods, trends were calculated for the relevant parameters by linear regression. The trend significance was determined by the non-parametric Mann-Kendall-trend test.Results and Conclusion
In the summer half of the year, distinctively more dry conditions developed. Over the same period, the winter half of the year became more wet. Regarding trends of extreme precipitation, a strong dependency to the size of the choosen treshold value exists. During the summer, size and excess frequency of the 90th and 95th percentiles have increased, whereas they decreased in the winter. On the other hand, the half year trends of the 99th percentile are predominantly positive. Particularly the trend towards more dry conditions in summer is of substantial relevance for the economy and water management.Recommendations and Perspective
The additional analysis of further precipitation data sets, provided by the Saxonion Climate database, will advance the regional accuracy of the presented findings. In addition work on the adjustment of an extreme distribution to daily and monthly precipitation sums is needed, and an effect-related definition of dry periods needs to be developed. 相似文献27.
Marc D. Hauser 《Behavioral ecology and sociobiology》1986,19(1):65-71
Summary Playback experiments were conducted of five groups of free-ranging vervet monkeys (Cercopithecus aethiops) to determine whether an adult male's responsiveness to infant distress calls was a function of (1) paternal certainty, (2) dominance rank, (3) predator presence, (4) number of males, (5) number of infants, (6) infant's mother's rank and/or (7) infant's age. Results from these experiments reveal that paternal certainty was the only factor that could directly explain the differences between males in the duration of response to distress calls. 相似文献
28.
Wolfgang Rotard Wilfried Christmann Wilhelm Knoth Wolfgang Mailahn 《Environmental Sciences Europe》1995,7(1):3-9
For the estimation of intestinal absorption of polychlorianted dibenzodioxins/dibenzofurans (PCDD/F), ain-vitro model was developed in order to study PCDD/F mobilization by digestion of technogenic soils using ?Kieselrot” (red slag) as substrate and digestive juice model mixtures. Red slag samples were shaken successively with model mixtures of saliva, gastric juice, duodenal juice and bile. The solids were separated, the aqueous phase was extracted with hexane, the hexane extract analyzed for PCDD/F. Additionally, the PCDD/F-content of the red slag was determined. Extraction efficiency was tested with three different digestive juice model mixtures and also tap water for comparision. The percentage of PCDD/F transferred from the red slag sample into the digestive juice mixture was defined as absorption availability. In our experiments, a maximum absorption availability of 2 % was found. 相似文献
29.
Thomas?WinklerEmail author Wilfried?Winiwarter 《Mitigation and Adaptation Strategies for Global Change》2016,21(8):1181-1196
In the present paper, national and externally organized projections of greenhouse gas emissions for Austria were compared to gain insight on the underlying scenario data assumptions. National greenhouse gas emission trends extend until 2030, an assessment of European Union (EU) countries to 2050. In addition, data for 2000–2100 was extracted from the global emission database described by the Representative Concentration Pathways (RCP). By identifying trends in these projections, it was possible to produce (a) a long-term assessment of national scenarios until 2100, (b) an assessment of the ambition level toward national climate strategies, and (c) a standardized method to compare trends across countries. By extracting RCP data, Austrian’s methane, nitrous oxide, and carbon dioxide emissions up to 2100 could be projected for all sources as well as specific sectors. With respect to the RCP scenario emission data, national projections did not seem to employ the mitigation potentials available for the most stringent RCP scenario, RCP2.6. Comparing projections that supported the EU Climate Strategy 2030 with national projections revealed similar trends. Because RCP2.6 is the only scenario consistent with a 2 °C global warming target, and it is much more ambitious than any of the national or European projections, further measures will be required if Austria is to adequately contribute to this widely accepted policy goal. 相似文献
30.
Animal eyes generally fall into two categories: (1) their photoreceptive array is convex, as is typical for camera eyes, including
the human eye, or (2) their photoreceptive array is concave, as is typical for the compound eye of insects. There are a few
rare examples of the latter eye type having secondarily evolved into the former one. When viewed in a phylogenetic framework,
the head morphology of a variety of male scale insects suggests that this group could be one such example. In the Margarodidae
(Hemiptera, Coccoidea), males have been described as having compound eyes, while males of some more derived groups only have
two single-chamber eyes on each side of the head. Those eyes are situated in the place occupied by the compound eye of other
insects. Since male scale insects tend to be rare, little is known about how their visual systems are organized, and what
anatomical traits are associated with this evolutionary transition. In adult male Margarodidae, one single-chamber eye (stemmateran
ocellus) is present in addition to a compound eye-like region. Our histological investigation reveals that the stemmateran
ocellus has an extended retina which is formed by concrete clusters of receptor cells that connect to its own first-order
neuropil. In addition, we find that the ommatidia of the compound eyes also share several anatomical characteristics with
simple camera eyes. These include shallow units with extended retinas, each of which is connected by its own small nerve to
the lamina. These anatomical changes suggest that the margarodid compound eye represents a transitional form to the giant
unicornal eyes that have been described in more derived species. 相似文献