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891.
Wang Jinwen Yuan Xiaohui Zhang Yongchuan Zhang Youquan 《Environmental Fluid Mechanics》2003,3(4):289-303
This paper proposes a reliability analysis system, which can be widely applied to the cases in which a reservoir is operated to meet several purposes such as flood control, energy generation, irrigation, domestic and industrial water supply, etc. The presented system has a structure of three levels.1. Decision-making.2. Tradeoff analysis.3. The third level that mainly consists of three subsystems:i – The reservoir flood risk analysis subsystem by flood control simulation.ii – The benefit promotion subsystem of reservoir operation using Stochastic Dynamic Programming. In this subsystem, the Lagrange multipliers are introduced into the objective function to take into account the water supply failures. This method guarantees that each run of the SDP will necessarily derive a non-inferior policy for reservoir operation.iii – The reservoir operation simulation subsystem to derive the performance indices associated with the reservoir operation policies. With the input and feedback between the second level and the subsystems of the third level, a great deal of efficient operation policies and the associated performance indices can be obtained. Then the tradeoff relationships between different performance indices can be derived for the decision makers. With application to Yudong Reservoir in Yunnan province of China, the presented analysis system is practically tested. 相似文献
892.
Robert C. Lee James R. Fricke William E. Wright Walt Haerer 《Environmental geochemistry and health》1995,17(4):169-181
A partially probabilistic blood lead prediction model has been developed, based on the US Environmental Protection Agency integrated exposure-uptake-biokinetic blood lead model (IEUBK model). This study translated the IEUBK model into a spreadsheet format. The uptake submodel incorporates uncertainty distributions for exposure and bioavailability parameters. The biokinetic submodel is duplicated with a table incorporating partitioning and decay of lead levels in the body. As a case study, the probabilistic model is applied to a lead exposure scenario involving a former smelter site in Sandy, Utah. The probabilistic model produces less biased estimates of means and standard deviations than the deterministic model. Parameter uncertainty is propagated in the model by the use of Monte Carlo simulation. Thus, sensitivity analysis is possible, and driving variables can be determined. 相似文献
893.
Frank Götmark 《Behavioral ecology and sociobiology》1997,40(1):41-49
Conspicuous color patterns in birds may lead to increased risk of predation. Alternatively, bright birds may be aposematic
or unprofitable prey, which leads to decreased predation. During four autumns, I examined whether the black-and-white plumage
of (stuffed) magpies Pica pica increases or reduces the risk of attack by migrating goshawks Accipiter gentilis. Attack risk was higher for normal magpies than for cryptic, brown magpies whether the mounts were placed near one another
or far apart. However, the brown magpie may have been avoided because of its novelty. For magpies and cryptic jays Garrulus glandarius exposed together, the attack risk was similar. In 2 years, magpie and jay mounts were also exposed far apart. In 1994, with
an invasion of migrating jays, attack risk was much higher for jays than for magpies. In 1995, with a normal density of jays,
hawks attacked the magpies more often. The results demonstrate frequency-dependent prey selection by goshawks, which would
influence any predation cost of bright plumage. The attacks on normally colored magpie mounts suggest that magpies are not
aposematic. Trials with photographs and human observers indicated that normal magpies were somewhat easier to detect than
jays. The plumage of the magpie possibly increases the risk of predation, but may be favoured by sexual or social selection.
Received: 18 January 1996 / Accepted after revision: 6 October 1996 相似文献
894.
广州市污水污泥堆肥在环境绿化中的应用 总被引:11,自引:1,他引:11
将广州市大坦沙污水处理厂产生的脱水生污泥与粉煤灰、稻草按质量比例4∶1.2∶1混合堆制而成的污泥堆肥,堆肥总养分含量高于农家肥中的鸡粪,无论单独施用或与化肥结合使用应用于草坪等园林绿地,均有明显效果。污泥堆肥在草坪土壤应用的肥效试验表明,污泥堆肥与化肥结合使用效果较好,能缩短草坪草出苗和成坪时间,显著提高建植初期草坪草的生物量,但每公顷施用纯污泥堆肥30t与60t比较两者草坪草生物量没有显著差异;污泥堆肥施用污染风险初步分析表明,土壤中的重金属含量、渗滤液中的NO3--N和全P含量随着污泥堆肥施用量的增加而明显提高,考虑到广东地处热带、亚热带,雨量丰富且暴雨多,土壤呈酸性的特点,在园林绿地等相对封闭的体系中施用本项目堆制的污泥堆肥,只要将年施用量控制在30t/hm2以下,是基本安全的。 相似文献
895.
This study evaluated the potential toxicological risk posed to human health due to the exposure to heavy metals by water ingestion
in an area affected by tanneries – the Cadeia-Feitoria hydrographic basin (Brazil). River water was collected at 10 sites,
every 3 months, from July 1999 to April 2000. After acid digestion, total metal concentration was determined by inductively
coupled plasma optical emission spectrometry (Cd, Cu, Cr, Ni, Zn), flame atomic absorption (Al, Fe, Pb, Mn), or cold vapor
atomic absorption spectrometry (Hg). Cr(VI) was complexed with diphenyl-carbazide and detected by UV–vis spectrometry. In
order to quantify the risk of exposure, the risk assessment methodology employed by the Environmental Protection Agency of
the United States was applied at a screening level. The assumed scenarios included extreme exposure patterns (ingestion of
untreated water, conversion of Cr(III) to Cr(VI), temporal peaks of pollution). Fe, Al, Cd, Hg, and Pb were not included in
the risk analysis, since they showed a low toxicity potential or were undetected in the samples. The selected metals presented
Hazard Quotients < 1, in the following order of increasing risk: Cu < Cr(III) < Zn < Ni < Mn < Cr(VI). Hazard indexes, representing
the additive effect of contaminants, were also low in the basin (< 1), but comparatively increased in the lower reach of Feitoria
and Cadeia Rivers. Although noncarcinogenic risk levels did not suggest possible adverse toxicological effects to the human
population, a considerable deviation from background conditions was observed downstream the area where tanneries are mainly
located. 相似文献
896.
Risk taking during parental care: a test of three hypotheses applied to the pied flycatcher 总被引:2,自引:0,他引:2
According to life-history theory, there will often be a conflict between investment in current versus future reproduction.
If a predator appears during breeding, parents must make a compromise between ensuring the growth and survival of offspring
(nest defence, feeding and brooding of young), and reducing the risk of predation to ensure their own survival. We model three
hypotheses for the outcome of this conflict which are particularly relevant for altricial birds. They are not mutually exclusive,
but focus on different costs and benefits. (1) Parental investment is determined by the parents’ own risk of predation. This
hypothesis predicts that a lone parent should take smaller risks than a parent that has a mate. (2) Parental investment is
related to the reproductive value of the offspring: Parents are predicted to take greater risks for larger broods, larger-sized
or older offspring. (3) Finally, we present the new hypothesis that parental investment is related to the harm that offspring
would suffer during a period of no parental care (incubation, brooding, feeding). This hypothesis predicts that parents should
take greater risks for younger offspring, or for offspring in poorer condition, because the marginal benefit of parental care
is largest in such cases. Hence, one may also expect that lone parents should take greater risks than two parents because
their offspring are more in need of care. We tested these hypotheses on the pied flycatcher (Ficedula hypoleuca) by presenting a stuffed predator of the parents (a sparrowhawk, Accipiter nisus) close to the nest when parents were feeding the young. Risk taking was measured as the time that elapsed until the first
visit to the nest. Most support was found for the ‘‘harm to offspring’’ hypothesis. Previous studies have usually measured
the intensity of nest defence against typical nest predators, and have found evidence for the ‘‘reproductive value of offspring’’
hypothesis. However, our model predicts that the importance of the reproductive value of the offspring should decrease relative
to the harm that offspring would suffer if they were not cared for when the predator type changes from a nest predator to
a predator of adults, and when conditions for breeding turn from good to bad.
Received: 13 April 1995/Accepted after revision: 11 March 1996 相似文献
897.
Designatable Units for Status Assessment of Endangered Species 总被引:8,自引:1,他引:8
DAVID M. GREEN 《Conservation biology》2005,19(6):1813-1820
Abstract: Species status assessment and the conservation of biological diversity may require defining units below the species level to portray probabilities of extinction accurately and to help set priorities for conservation efforts. What those units should be has been debated in the scientific literature largely in terms of evolutionarily significant units (ESUs), but this discourse has had little impact on government policy with regard to status assessment. As with species concepts, the variously proposed ESU concepts have not been resolvable into a single approach. The need for a practicable procedure to identify infraspecific entities for status assignment is the motivation behind employing designatable units (DUs). In aid of a policy to prevent elements of biodiversity from becoming extinct or extirpated, DUs are determined during the process of resolving a species' conservation status according to broadly applicable guidelines. The procedure asks whether putative DUs are distinguishable based on a reliably established taxonomy or a well-corroborated phylogeny, compelling evidence of genetic distinction, range disjunction, and/or biogeographic distinction as long as extinction probabilities also differ. The language of the DU approach avoids wording that implies value judgments concerning evolutionary importance or significance. Because species conservation status assessment is not science but, rather, the use of science to further policy, DUs contribute to a precautionary approach to listing whereby status may be assessed even though knowledge of systematic relationships below the species level may be lacking or unresolved. The pragmatic approach of using DUs has been adopted by the Committee on the Status of Endangered Wildlife in Canada for status assessment of species under the Canadian Species at Risk Act. 相似文献
898.
Market responses to hurricanes 总被引:7,自引:0,他引:7
Daniel G. Hallstrom V. Kerry Smith 《Journal of Environmental Economics and Management》2005,50(3):541-561
This paper uses one of the strongest hurricanes to hit the US, Andrew in 1992, to define a quasi-random experiment that permits estimation of the responses of housing values to information about new hurricanes. Lee County, Florida did not experience damage from Andrew. The storm was a “near-miss.” We hypothesize that Andrew conveyed risk information to homeowners in the county. A difference-in-differences (DND) framework identifies the effect of this information on property values in areas likely to experience significant storm damage. The DND findings indicate at least a 19 percent decline in property values. 相似文献
899.
Predation and hunger are threats for most organisms, and appropriate behavioural responses to both factors should be shaped by natural selection. In combination, however, the behavioural demands of predation avoidance and effective foraging often cannot be satisfied at the same time and lead to a conflict within organisms. We examined the behavioural responses of two closely-related species of tadpoles, Rana lessonae and R. esculenta, to simulated predation by fish and hunger. Tadpoles, hatched and reared in the laboratory, were tested in a three-way factorial (predation risk × hunger × species) experiment with four predation levels and four hunger levels. Both species decreased their swimming activity with increasing predation risk. Predation risk did not influence the amount of activity time invested in feeding but caused the tadpoles to spend less time in patches with food. Refuges were not used to avoid predation. R. esculenta was more sensitive to predation risk than R. lessonae. Hunger increased both the activity of tadpoles and the amount of activity time invested in feeding, thus indicating an increased energy intake. No interactions were observed between predation risk and hunger. These results show that tadpoles possess genetically-based behavioural mechanisms that allow them to respond in a graded manner to predation and hunger. However, they did not balance the two conflicting demands of predation avoidance and effective foraging; the two mechanisms appeared to act independently.
Correspondence to: R.D. Semlitsch 相似文献
900.
An important topic in the registration of pesticides and the interpretation of monitoring data is the estimation of the consequences of a certain concentration of a pesticide for the ecology of aquatic ecosystems. Solving these problems requires predictions of the expected response of the ecosystem to chemical stress. Up until now, a dominant approach to come up with such a prediction is the use of simulation models or safety factors. The disadvantage of the use of safety factors is a crude method that does not provide any insight into the concentration–response relationships at the ecosystem level. On the other hand, simulation models also have serious drawbacks like that they are often very complex, lack transparency, their implementation is expensive and there may be a compilation of errors, due to uncertainties in parameters and processes. In this paper, we present the expert model prediction of the ecological risks of pesticides (PERPEST) that overcomes these problems. It predicts the effects of a given concentration of a pesticide based on the outcome of already performed experiments using experimental ecosystems. This has the great advantage that the outcome is more realistic. The paper especially discusses how this model can be used to translate measured and predicted concentrations of pesticides into ecological risks, by taking data on measured and predicted concentrations of atrazine as an example. It is argued that this model can be of great use to evaluate the outcome of chemical monitoring programmes (e.g. performed in the light of the Water Framework Directive) and can even be used to evaluate the effects of mixtures. 相似文献