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11.
Sander P. M. Ganzevles Fons S. W. van Nuland Leo R. M. Maas Huub M. Toussaint 《Die Naturwissenschaften》2009,96(4):449-456
In nautical literature, ‘dead-water’ refers to the obstructive effect encountered by ships moving in stratified water due
to the ship generating waves on an interface that separates different water masses. To investigate the hypothesis that open
water swimming may also be obstructed by an encounter of dead-water, possibly causing drowning, we performed two experiments
that assess the impact of stratified water on swimming. In the first experiment, subjects made a single front-crawl stroke
while lying on a carriage that was rolling just above the water surface. The gain in kinetic energy, as a result of the stroke,
was far less in stratified than in homogeneous water. In the second experiment, four subjects swam a short distance (5 m)
in homogeneous and in two different settings of stratified water. At the same stroke frequency, swimming in stratified conditions
was slower by 15%, implying a loss in propulsive power by 40%. Although in nature stratification will be less strong, extrapolation
of the results suggests that dead-water might indeed obstruct swimming in open water as well. This effect will be most pronounced
during fair weather, when stratification of a shallow surface layer is most easily established. Our findings indicate that
swimmers’ anecdotal evidence on ‘water behaving strangely’ may have to be taken more seriously than previously thought. 相似文献
12.
J. G. J. Olivier A. F. Bouwman C. W. M. van der Maas J. J. M. Berdowski 《Environmental monitoring and assessment》1994,31(1-2):93-106
Atmospheric chemistry and climate modellers require gridded global emissions data as input into their models. To meet this urgent need a global emissions source database called EDGAR is being developed by TNO and RIVM to estimate for 1990, on a regional and on a grid basis, annual emissions of greenhouse gases (CO2, CH4, N2O, CO, NOx, non-methane VOC, SOx), of NH3, and of ozone depleting compounds (halocarbons) from all known sources. The aim is to establish at due levels of spatial, temporal and source aggregation the emissions from both anthropogenic and biogenic sources: a complete set of data required to estimate the total source strength of the various gases with a 1×1 ° resolution (altitude resolution of 1 km) and a temporal resolution of a month, supplemented by diurnal variation, as agreed upon in the Global Emissions Inventory Activity (GEIA) of the International Atmospheric Chemistry Programme (IGAC). In this way EDGAR will meet the requirements of present and future developments in the field of atmospheric modelling. The data comprise demographic data, social and economic factors, land use distributions and emission factors (with due emphasis on the uncertainty). As understanding in this field is still changing, due attention is paid to flexibility regarding the disaggregation of sources, spatial and temporal resolution and species. The objective and methodology chosen for the construction of the database and the structural design of the database system are presented, as well as the type and sources of data and the approach used for data collection. As an example, the construction of the N2O inventory is discussed. 相似文献
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Spatial distribution of heavy metal concentrations in urban, suburban and agricultural soils in a Mediterranean city of Algeria 总被引:2,自引:0,他引:2
S. Maas R. Scheifler N. Crini Z. Brahmia P. Giraudoux 《Environmental pollution (Barking, Essex : 1987)》2010,158(6):2294-2301
As part of a larger program aiming at assessing transfer and effects of metals in food webs, this work studied the spatial distribution of Cd, Cr, Cu, Pb, and Zn in 101 sub-surface soils, systematically sampled (1 × 1 km regular grid) over a large area around Annaba, the fourth most-populated city of Algeria. Cd and Cr exhibited only one abnormally high value, with all other concentrations being close to pedogeological background. Some places in the centre of the city were polluted by Pb (up to 823 mg kg−1), probably due to aerial deposition from gasoline exhausts. Zn never exceeded regulatory limits over the whole sampling area. Cu was the only element for which a spatial autocorrelation occurred. A spatial interpolation by cokriging allowed the identification of agricultural activities as the main Cu pollution source. Our approach revealed various anthropogenic pollution sources, more efficiently for large-scale patterns than for local abnormalities. 相似文献
17.
L. A. Bollinger C. W. J. Bogmans E. J. L. Chappin G. P. J. Dijkema J. N. Huibregtse N. Maas T. Schenk M. Snelder P. van Thienen S. de Wit B. Wols L. A. Tavasszy 《Regional Environmental Change》2014,14(3):919-931
Infrastructures are critical for human society, but vulnerable to climate change. The current body of research on infrastructure adaptation does not adequately account for the interconnectedness of infrastructures, both internally and with one another. We take a step toward addressing this gap through the introduction of a framework for infrastructure adaptation that conceptualizes infrastructures as complex socio-technical “systems of systems” embedded in a changing natural environment. We demonstrate the use of this framework by structuring potential climate change impacts and identifying adaptation options for a preliminary set of cases—road, electricity and drinking water infrastructures. By helping to clarify the relationships between impacts at different levels, we find that the framework facilitates the identification of key nodes in the web of possible impacts and helps in the identification of particularly nocuous weather conditions. We also explore how the framework may be applied more comprehensively to facilitate adaptation governance. We suggest that it may help to ensure that the mental models of stakeholders and the quantitative models of researchers incorporate the essential aspects of interacting climate and infrastructure systems. Further research is necessary to test the framework in these contexts and to determine when and where its application may be most beneficial. 相似文献
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Lilliana Abarca Guerrero Ger Maas William Hogland 《Waste management (New York, N.Y.)》2013,33(1):220-232
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Cycling of volatile organic sulfur compounds in anaerobically digested biosolids and its implications for odors. 总被引:4,自引:0,他引:4
Matthew J Higgins Yen-Chih Chen Douglas P Yarosz Sudhir N Murthy Nick A Maas Dietmar Glindemann John T Novak 《Water environment research》2006,78(3):243-252
The objectives of this research were to elucidate the mechanisms for production and degradation of volatile organic sulfur compounds (VOSCs), key odor causing compounds produced by biosolids. These compounds included methanethiol (MT), dimethyl sulfide (DMS), and dimethyl disulfide (DMDS). A series of experiments were used to probe various pathways hypothesized to produce and degrade these VOSCs. The production of MT was found to mainly occur from degradation of methionine and the methylation of hydrogen sulfide. DMS was formed through the methylation of MT. DMDS was formed by MT oxidation. All three of the VOSCs were readily degraded by methanogens and a cyclic pathway was proposed to describe the production and degradation of VOSCs. The research demonstrated that the main source of VOSCs was the biodegradation of protein within the biosolids and the results provided a framework for understanding the production of odor from anaerobically digested sludges before and after dewatering. 相似文献
20.
Assessing the susceptibility of societies to droughts: a political science perspective 总被引:3,自引:2,他引:1
In this article we develop a concept for the assessment of state’s susceptibility to drought based on a political science
perspective. Different sources of capacities and sensitivities need to be taken into account to assess the overall susceptibility
of states as political systems. We argue that the overall susceptibility of a society depends on an interplay of state capacity
and readiness as main elements of political susceptibility, wealth and economic sensitivity as elements of economic susceptibility
and the degree of social integration. To transform the conceptual model into a susceptibility assessment we developed an inference
model in order to generate quantitative indices. For this purpose we apply fuzzy set theory using data from our case study
regions, namely Andhra Pradesh (India), the Volga region (Russia) and (Southern) Portugal. The resulting computed trends for
Portugal suggest that the society will be able to deal even with severe natural conditions due to existing political, economic,
and social conditions. The assessment results for the Indian and Russian case study regions, in contrast, give reason for
precaution since the occurrence of drought-induced crisis events seems much more likely in the light of more crucial, overall
conditions, namely lower degrees of state capacity and readiness as well as, in the case of India, a high economic susceptibility.
However, further improvements are possible given the improved availability of data and the integration of more qualitative
information. Additionally, the expansion to further case study regions could help validate the overall concept. 相似文献