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排序方式: 共有1193条查询结果,搜索用时 15 毫秒
861.
Aalto P Hämeri K Paatero P Kulmala M Bellander T Berglind N Bouso L Castaño-Vinyals G Sunyer J Cattani G Marconi A Cyrys J von Klot S Peters A Zetzsche K Lanki T Pekkanen J Nyberg F Sjövall B Forastiere F 《Journal of the Air & Waste Management Association (1995)》2005,55(8):1064-1076
In this study, long-term aerosol particle total number concentration measurements in five metropolitan areas across Europe are presented. The measurements have been carried out in Augsburg, Barcelona, Helsinki, Rome, and Stockholm using the same instrument, a condensation particle counter (TSI model 3022). The results show that in all of the studied cities, the winter concentrations are higher than the summer concentrations. In Helsinki and in Stockholm, winter concentrations are higher by a factor of two and in Augsburg almost by a factor of three compared with summer months. The winter maximum of the monthly average concentrations in these cities is between 10,000 cm(-3) and 20,000 cm(-3), whereas the summer min is approximately 5000-6000 cm(-3). In Rome and in Barcelona, the winters are more polluted compared with summers by as much as a factor of 4-10. The winter maximum in both Rome and Barcelona is close to 100,000 cm(-3), whereas the summer minimum is > 10,000 cm(-3). During the weekdays the maximum of the hourly average concentrations in all of the cities is detected during the morning hours between 7 and 10 a.m. The evening maxima were present in Barcelona, Rome, and Augsburg, but these were not as pronounced as the morning ones. The daily maxima in Helsinki and Stockholm are close or even lower than the daily minima in the more polluted cities. The concentrations between these two groups of cities are different with a factor of about five during the whole day. The study pointed out the influence of the selection of the measurement site and the configuration of the sampling line on the observed concentrations. 相似文献
862.
Justus Kristine A. Murlis John Jones Chris Cardé Ring T. 《Environmental Fluid Mechanics》2002,2(1-2):115-142
The patterns of stimulus available to moths flying along pheromone plumes in a 3-m-long wind tunnel were characterized using a high frequency photoionization detector in conjunction with an inert tracer gas. Four contrasting flow regimes and source conditions were produced: odor released in pulses from a vertical and horizontal array of four sources, odor released continuously from a point source, and odor released continuously from a point source into an oscillatory wake. Although the four flow regimes produced plumes of intermittent and fluctuating concentration, there were considerable differences in the structure of the signal presented to the sensor. Pulses of tracer gas released at 10 Hz retained most of their longitudinal and lateral separation. The plume growing in the disturbed flow (`oscillatory'), was broader in its lateral extent than the plume growing in an undisturbed flow (`continuous'), and the concentrations in the former were lower at each downstream position. The signal recorded in the disturbed flow had higher intermittency, but the ratio between the peak concentration and the signal mean was lower than in the continuous plume. Time scales were typically longer in the tunnel than in a field setting, but length scales and the main features of intermittency and fluctuation were similar. Moths flying along plumes of pheromone in this and similar wind tunnels typically slow their velocity and narrow the lateral excursions of their flight track as they approach a pheromone source. Which features of the plumes measured in this study account for these behavioral reactions remains to be determined. 相似文献
863.
Peter M van Bodegom Annelies Oosthoek Rob Broekman Chris Bakker Rien Aerts 《Ecological applications》2006,16(5):1785-1795
The experience with restoring high water levels (i.e., rewetting) within restoration ecology is limited, and information on changes in soil nutrient supply is scarce. A reduction in nutrient supply is needed to restore the desired oligotrophic vegetation. We determined the effects of restoration of high water levels on decomposition and net carbon (C), nitrogen (N), and phosphorus (P) mineralization rates in wet dune slacks and its consequences for the relative abundance of eutrophic vs. oligotrophic species in the vegetation. This was done by analyzing these variables for valleys that experienced a large groundwater rise vs. valleys that had a small groundwater rise but the same current water level. In addition, the influences of underlying factors (waterlogging, vegetation dieback, and soil dynamics prior to groundwater rise) were separated in a transplantation experiment. Short-term effects of large groundwater rise were a massive dieback of vegetation, increased thickness of the fermentation layer, increased microbial decomposition activity, increased C mineralization, and decreased net N mineralization. Net P mineralization was not affected. The relative abundance of oligotrophic vs. eutrophic species was greater at large groundwater rise. Changes in decomposition and mineralization by large groundwater rise were, however, not caused by the vegetation dieback, but due to previous soil conditions. Soils experiencing waterlogged conditions for 3-4 years or more prior to large groundwater rise had lower C and higher net N mineralization rates at waterlogged conditions than soils that had experienced aerobic conditions, presumably due to differences in labile soil C contents. Contrary to expectations induced by previously determined nutrient pulses and measured vegetation dieback, large groundwater rise resulted in lower soil nutrient supply rates and more oligotrophic vegetation. If these trends continue on the longer term, restoration of high water levels may be effective in restoration ecology to establish oligotrophic, wet vegetation in dune slacks. 相似文献
864.
Pieter Bloemen Tim Reeder Chris Zevenbergen Jeroen Rijke Ashley Kingsborough 《Mitigation and Adaptation Strategies for Global Change》2018,23(7):1083-1108
Worldwide, an increase in flood damage is observed. Governments are looking for effective ways to protect lives, buildings, and infrastructure. At the same time, a large investment gap seems to exist—a big difference between what should necessarily be done to curb the increase in damage and what is actually being done. Decision-makers involved in climate adaptation are facing fundamental (so-called deep) uncertainties. In the course of time, the scientific community has developed a wide range of different approaches for dealing with these uncertainties. One of these approaches, adaptation pathways, is gaining traction as a way of framing and informing climate adaptation. But research shows that “very little work has been done to evaluate the current use of adaptation pathways and its utility to practitioners and decision makers” (Lin et al. 2017, p. 387). With this paper, the authors, as action researchers and practitioners involved in two of the world’s largest real-life applications of this approach in flood risk management, aim to contribute to filling in that gap. Analysis of the experience in the United Kingdom and the Netherlands in long-term planning in flood risk management shows that the adaptation pathways approach is effective in keeping decision processes going forward, to the final approval of a long-term plan, and helps increase awareness about uncertainties. It contributes to political support for keeping long-term options open and motivates decision-makers to modify their plans to better accommodate future conditions. When it comes to implementing the plans, there are still some major challenges, yet to be addressed, amongst others: the timely detection of tipping points in situations with large natural variability, the inclusion of measures that prepare for a switch to transformational strategies, and the retention of commitment of regional and local authorities, non government organizations, and the private sector, to climate adaptation as national policies move from blueprint planning to adaptive plans. In delivering this feedback, the authors hope to motivate the scientific community to take on these challenges. 相似文献
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868.
G. H. R. von Koenigswald 《Die Naturwissenschaften》1953,40(4):128-137
869.
870.
In Australia, local communities often enact Community-Based Initiatives (CBIs) to respond to climate change through Climate Change Adaptation (CCA). CBIs can also be integrated into the Disaster Risk Reduction (DRR) agenda. The paper explores the extent to which CBIs promote the mainstreaming of CCA into DRR. Primary data were obtained from interviews with representatives of CBIs and supporting organisations in three local governments of the Hunter Valley (New South Wales, Australia). Findings show that CBIs recognise the potential contribution of climate change in modifying the local hazard profile. CBIs mainstream CCA into DRR by following four approaches: environmental and social justice; sustainability and transition; ecosystem-based approach; and adaptive planning. Partnerships were identified both among CBIs and between CBIs and City Councils; however, conflicts between CBIs, City Councils and business actors emerged, and a lack of commitment by multi-level governments in responding to climate change was revealed. The findings show that CBIs consider CCA and DRR within a broad everyday context related to vulnerability and local development. But we argue that assigning responsibility for climate change issues to CBIs is not a panacea and should not be the only local climate change response. Instead, CBIs need to be included in a larger and long-term commitment by actors that possess access to resources, such as higher levels of government. The paper provides a local Australian perspective on the effectiveness of mainstreaming CCA into DRR and furthers the conversation for the benefit of other communities facing similar challenges. 相似文献