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  • 1
    ISSN: 1539-6924
    Schlagwort(e): compliance certification application ; engineering analysis ; geochemistry ; geohydrology ; performance assessment ; probabilistic systems analysis ; radioactive waste ; scientific validity ; uncertainty ; 40 CFR 191
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Performance Assessment (PA) is the use of mathematical models to simulate the long-term behavior of engineered and geologic barriers in a nuclear waste repository; methods of uncertainty analysis are used to assess effects of parametric and conceptual uncertainties associated with the model system upon the uncertainty in outcomes of the simulation. PA is required by the U.S. Environmental Protection Agency as part of its certification process for geologic repositories for nuclear waste. This paper is a dialogue to explore the value and limitations of PA. Two “skeptics” acknowledge the utility of PA in organizing the scientific investigations that are necessary for confident siting and licensing of a repository; however, they maintain that the PA process, at least as it is currently implemented, is an essentially unscientific process with shortcomings that may provide results of limited use in evaluating actual effects on public health and safety. Conceptual uncertainties in a PA analysis can be so great that results can be confidently applied only over short time ranges, the antithesis of the purpose behind long-term, geologic disposal. Two “proponents” of PA agree that performance assessment is unscientific, but only in the sense that PA is an engineering analysis that uses existing scientific knowledge to support public policy decisions, rather than an investigation intended to increase fundamental knowledge of nature; PA has different goals and constraints than a typical scientific study. The “proponents” describe an ideal, six-step process for conducting generalized PA, here called probabilistic systems analysis (PSA); they note that virtually all scientific content of a PA is introduced during the model-building steps of a PSA; they contend that a PA based on simple but scientifically acceptable mathematical models can provide useful and objective input to regulatory decision makers. The value of the results of any PA must lie between these two views and will depend on the level of knowledge of the site, the degree to which models capture actual physical and chemical processes, the time over which extrapolations are made, and the proper evaluation of health risks attending implementation of the repository. The challenge is in evaluating whether the quality of the PA matches the needs of decision makers charged with protecting the health and safety of the public.
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  • 2
    ISSN: 1539-6924
    Schlagwort(e): risk assessment ; uncertainty ; formaldehyde ; decision analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract A call for risk assessment approaches that better characterize and quantify uncertainty has been made by the scientific and regulatory community. This paper responds to that call by demonstrating a distributional approach that draws upon human data to derive potency estimates and to identify and quantify important sources of uncertainty. The approach is rooted in the science of decision analysis and employs an influence diagram, a decision tree, probabilistic weights, and a distribution of point estimates of carcinogenic potency. Its results estimate the likelihood of different carcinogenic risks (potencies) for a chemical under a specific scenario. For this exercise, human data on formaldehyde were employed to demonstrate the approach. Sensitivity analyses were performed to determine the relative impact of specific levels and alternatives on the potency distribution. The resulting potency estimates are compared with the results of an exercise using animal data on formaldehyde. The paper demonstrates that distributional risk assessment is readily adapted to situations in which epidemiologic data serve as the basis for potency estimates. Strengths and weaknesses of the distributional approach are discussed. Areas for further application and research are recommended.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Risk analysis 19 (1999), S. 585-598 
    ISSN: 1539-6924
    Schlagwort(e): uncertainty ; threatened plants ; risk ; conservation ; rule sets ; IUCN
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Australian state and federal agencies use a broad range of methods for setting conservation priorities for species at risk. Some of these are based on rule sets developed by the International Union for the Conservation of Nature, while others use point scoring protocols to assess threat. All of them ignore uncertainty in the data. In this study, we assessed the conservation status of 29 threatened vascular plants from Tasmania and New South Wales using a variety of methods including point scoring and rule-based approaches. In addition, several methods for dealing with uncertainty in the data were applied to each of the priority-setting schemes. The results indicate that the choice of a protocol for setting priorities and the choice of the way in which uncertainty is treated may make important differences to the resulting assessments of risk. The choice among methods needs to be rationalized within the management context in which it is to be applied. These methods are not a substitute for more formal risk assessment.
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  • 4
    ISSN: 1539-6924
    Schlagwort(e): Variability ; uncertainty ; maximum likelihood ; bootstrap simulation ; Monte Carlo simulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Variability arises due to differences in the value of a quantity among different members of a population. Uncertainty arises due to lack of knowledge regarding the true value of a quantity for a given member of a population. We describe and evaluate two methods for quantifying both variability and uncertainty. These methods, bootstrap simulation and a likelihood-based method, are applied to three datasets. The datasets include a synthetic sample of 19 values from a Lognormal distribution, a sample of nine values obtained from measurements of the PCB concentration in leafy produce, and a sample of five values for the partitioning of chromium in the flue gas desulfurization system of coal-fired power plants. For each of these datasets, we employ the two methods to characterize uncertainty in the arithmetic mean and standard deviation, cumulative distribution functions based upon fitted parametric distributions, the 95th percentile of variability, and the 63rd percentile of uncertainty for the 81st percentile of variability. The latter is intended to show that it is possible to describe any point within the uncertain frequency distribution by specifying an uncertainty percentile and a variability percentile. Using the bootstrap method, we compare results based upon use of the method of matching moments and the method of maximum likelihood for fitting distributions to data. Our results indicate that with only 5–19 data points as in the datasets we have evaluated, there is substantial uncertainty based upon random sampling error. Both the boostrap and likelihood-based approaches yield comparable uncertainty estimates in most cases.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Risk analysis 19 (1999), S. 1193-1204 
    ISSN: 1539-6924
    Schlagwort(e): multimedia modeling ; uncertainty ; variability ; exposure efficiency ; toxicity scoring ; toxics release inventory (TRI) ; life cycle assessment (LCA)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract The human toxicity potential, a weighting scheme used to evaluate toxic emissions for life cycle assessment and toxics release inventories, is based on potential dose calculations and toxicity factors. This paper evaluates the variance in potential dose calculations that can be attributed to the uncertainty in chemical-specific input parameters as well as the variability in exposure factors and landscape parameters. A knowledge of the uncertainty allows us to assess the robustness of a decision based on the toxicity potential; a knowledge of the sources of uncertainty allows us to focus our resources if we want to reduce the uncertainty. The potential dose of 236 chemicals was assessed. The chemicals were grouped by dominant exposure route, and a Monte Carlo analysis was conducted for one representative chemical in each group. The variance is typically one to two orders of magnitude. For comparison, the point estimates in potential dose for 236 chemicals span ten orders of magnitude. Most of the variance in the potential dose is due to chemical-specific input parameters, especially half-lives, although exposure factors such as fish intake and the source of drinking water can be important for chemicals whose dominant exposure is through indirect routes. Landscape characteristics are generally of minor importance.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Risk analysis 19 (1999), S. 995-1002 
    ISSN: 1539-6924
    Schlagwort(e): conditional ; uncertainty ; probability ; intervals ; risk analysis ; conservatism ; Waste Isolation Pilot Plant
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Uncertainty analyses and the reporting of their results can be misinterpreted when these analyses are conditional on a set of assumptions generally intended to bring some conservatism in the decisions. In this paper, two cases of conditional uncertainty analysis are examined. The first case includes studies that result, for instance, in a family of risk curves representing percentiles of the probability distribution of the future frequency of exceeding specified consequence levels conditional on a set of hypotheses. The second case involves analyses that result in an interval of outcomes estimated on the basis of conservative assumptions. Both types of results are difficult to use because they are sometimes misinterpreted as if they represented the output of a full uncertainty analysis. In the first case, the percentiles shown on each risk curve may be taken at face value when in reality (in marginal terms) they are lower if the chosen hypotheses are conservative. In the second case, the fact that some segments of the resulting interval are highly unlikely—or that some more benign segments outside the range of results are quite possible—does not appear. Also, these results are difficult to compare to those of analyses of other risks, possibly competing for the same risk management resources, and the decision criteria have to be adapted to the conservatism of the hypotheses. In this paper, the focus is on the first type (conditional risk curves) more than on the second and the discussion is illustrated by the case of the performance assessment of the Waste Isolation Pilot Plant in New Mexico. For policy-making purposes, however, the problems of interpretation, comparison, and use of the results are similar.
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Risk analysis 19 (1999), S. 135-152 
    ISSN: 1539-6924
    Schlagwort(e): Probability ; uncertainty ; data ; risk assessment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Risk assessors attempting to use probabilistic approaches to describe uncertainty often find themselves in a data-sparse situation: available data are only partially relevant to the parameter of interest, so one needs to adjust empirical distributions, use explicit judgmental distributions, or collect new data. In determining whether or not to collect additional data, whether by measurement or by elicitation of experts, it is useful to consider the expected value of the additional information. The expected value of information depends on the prior distribution used to represent current information; if the prior distribution is too narrow, in many risk-analytic cases the calculated expected value of information will be biased downward. The well-documented tendency toward overconfidence, including the neglect of potential surprise, suggests this bias may be substantial. We examine the expected value of information, including the role of surprise, test for bias in estimating the expected value of information, and suggest procedures to guard against overconfidence and underestimation of the expected value of information when developing prior distributions and when combining distributions obtained from multiple experts. The methods are illustrated with applications to potential carcinogens in food, commercial energy demand, and global climate change.
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  • 8
    ISSN: 1573-0956
    Schlagwort(e): (AGI) ; heat flow ; lithosphere ; thermal conductivity ; thermal diffusivity ; models ; uncertainty
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Measurements on thermal conductivity and diffusivity as functions of temperature (up to 1150 K) and pressure (up to 1000 MPa) are presented for Archaean and Proterozoic mafic high-grade rocks metamorphosed in middle and lower crustal pressures, and situated in eastern Finland, central Fennoscandian Shield. Decrease of 12–20% in conductivity and 40–55% in diffusivity was recorded between room temperature and 1150 K, which can be considered as typical of phonon conductivity. Radiative heat transfer effects were not detected in these samples. Pressure dependencies of the samples are weak if compared to crystalline rocks in general, but relatively typical for mafic rocks. The temperature and pressure dependencies of thermal transport properties (data from literature and the present study) were applied in an uncertainty analysis of lithospheric conductive thermal modellings with random (Monte Carlo) simulations using a 4-layer model representative of shield lithosphere. Model parameters were varied according to predetermined probability functions and standard deviations were calculated for lithospheric temperature and heat flow density after 1500 independent simulations. The results suggest that the variations (uncertainties) in calculated temperature and heat flow density values due to variations in the temperature and pressure dependencies of conductivity are minor in comparison to the effects produced by typical variations in the room temperature value of conductivity, heat production rate or lower boundary condition values.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Environmental and resource economics 14 (1999), S. 75-94 
    ISSN: 1573-1502
    Schlagwort(e): CGE ; Costa Rica ; environmental indicators ; Monte Carlo ; parameter values ; trade policy ; uncertainty
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik , Wirtschaftswissenschaften
    Notizen: Abstract This study explores the role of parameter uncertainty in CGE modeling of the environmental impacts of macroeconomic and sectoral policies, using Costa Rica as a case for study. A CGE model is constructed which includes eight environmental indicators covering deforestation, pesticides, overfishing, hazardous wastes, inorganic wastes, organic wastes, greenhouse gases, and air pollution. The parameters are treated as random variables drawn from prespecified distributions. Evaluation of each policy option consists of a Monte Carlo experiment. The impacts of the policy options on the environmental indicators are relatively robust to different parameter values, in spite of the wide range of parameter values employed.
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Biogeochemistry 44 (1999), S. 119-134 
    ISSN: 1573-515X
    Schlagwort(e): atmospheric ; cloud water ; deposition ; ecosystem ; fixed nitrogen ; volcano
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract Precipitation, dry deposition, and cloud water deposition of fixed nitrogen (nitrate and ammonium ions) were measured on the Island of Hawaii. The first two were small N inputs, averaging 0.6±0.2 and 0.15±0.08 kg N ha-1 yr- 1 respectively. We estimate cloud water deposition to be 8–22 kg inorganic N ha-1 yr-1. If an estimate of organic N is included, it may be as high as 50 kg N ha-1 yr-1. Additionally, cloud water deposition is of hydrological significance as it comprised 37% of the total water input. Cloud water interception was certainly lower in the past, as the developing ecosystem would have had less collection surface area. Cloud water samples that were associated with volcanic haze events were very concentrated in NO3- and constituted 60% of the annual cloud water N deposition. This NO3- probably originated from atmospheric N fixed thermally at the hot lava surface or from an interaction between lava and the ocean. If volcanically influenced samples are excluded from the analysis, the resulting cloud water deposition would have been 4–9 kg N ha-1 yr-1. The Pacific Ocean and Kilauea volcano may have a profound impact on the development of this terrestrial ecosystem, as sources of fixed nitrogen.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Biogeochemistry 47 (1999), S. 111-118 
    ISSN: 1573-515X
    Schlagwort(e): cloud water ; deposition ; ecosystem ; fixed nitrogen ; nutrients ; volcano
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract Hawaiian montane ecosystems developing on recent tephra deposits contain more fixed nitrogen than conventional sources can explain. Heath and Huebert (1999) demonstrated that cloud water interception is the mechanism by which this extra nitrogen is deposited, but could not identify its source. We show here that atmospheric dinitrogen is fixed at the surface of active lava flows, producing concentrations of NO which are higher than those found in most urban rush hour air pollution. Over a period of hours this NO is blown away from the island and oxidized to nitrate. Interruptions in the trade wind flow can return this nitrate to the island to be deposited in cloud water. Thus, fixation on active lava flows is able to provide nitrogen to developing ecosystems on flows emplaced earlier.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Biogeochemistry 47 (1999), S. 111-118 
    ISSN: 1573-515X
    Schlagwort(e): cloud water ; deposition ; ecosystem ; fixed nitrogen ; nutrients ; volcano
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract Hawaiian montane ecosystems developing on recent tephra deposits contain more fixed nitrogen than conventional sources can explain. Heath and Huebert (1999) demonstrated that cloud water interception is the mechanism by which this extra nitrogen is deposited, but could not identify its source. We show here that atmospheric dinitrogen is fixed at the surface of active lava flows, producing concentrations of NO which are higher than those found in most urban rush hour air pollution. Over a period of hours this NO is blown away from the island and oxidized to nitrate. Interruptions in the trade wind flow can return this nitrate to the island to be deposited in cloud water. Thus, fixation on active lava flows is able to provide nitrogen to developing ecosystems on flows emplaced earlier.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Environmental and resource economics 13 (1999), S. 435-458 
    ISSN: 1573-1502
    Schlagwort(e): bioeconomics ; multiple stocks ; humane values ; Minke whales ; Monte Carlo analysis ; uncertainty
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik , Wirtschaftswissenschaften
    Notizen: Abstract Most bioeconomic models of efficient renewable resource management are constructed for a single harvesting ground. A bioeconomic model is developed in this paper to study the optimal management of renewable resources that are found in spatially distinct harvesting grounds. The model is applied to Minke whale management. Important inter-regional substitution effects are shown to exist. In addition, comparison with previous studies shows that multiple stock management is necessary for efficient management. Finally, the current Minke whale moratorium is shown to be inefficient unless significant nonmarket values exist.
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Mitigation and adaptation strategies for global change 4 (1999), S. 267-281 
    ISSN: 1573-1596
    Schlagwort(e): societal adaptation ; globalisation ; institutional capacity ; resilience ; uncertainty ; vulnerability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik , Geographie
    Notizen: Abstract Institutions in many wealthy industrialised countries are robust and their societies appear to be relatively well insulated against the impacts of climate variability, economic problems elsewhere and so on. However, many countries are not in this position, and there is a growing group of humanity which is not benefiting from the apparent global adaptive trends. Worst case scenarios reinforce the impact of this uneven distribution of adaptive capacity, both between and within countries. Nevertheless, at the broad global scale human societies are strongly adaptive and not threatened by climate change for many decades. At the local level the picture is quite different and the survival of some populations at their present locations is in doubt. In the absence of abatement, the longer term outlook is highly uncertain. Adaptation research needs to begin with an understanding of social and economic vulnerability. It requires a different approach to the traditional IPCC impacts assessment, as human behaviour, institutional capacity and culture are more important than biophysical impacts. This is consistent with the intellectual history of the IPCC which has gradually embraced an increasing range of disciplines.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Mitigation and adaptation strategies for global change 4 (1999), S. 319-329 
    ISSN: 1573-1596
    Schlagwort(e): uncertainty ; risk ; adaptation ; extreme events ; (credible) information ; integrated assessment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik , Geographie
    Notizen: Abstract This paper draws ten lessons from analyses of adaptation to climate change under conditions of risk and uncertainty: (1) Socio-economic systems will likely respond most to extreme realizations of climate change. (2) Systems have been responding to variations in climate for centuries. (3) Future change will effect future citizens and their institutions. (4) Human systems can be the sources of surprise. (5) Perceptions of risk depend upon welfare valuations that depend upon expectations. (6) Adaptive decisions will be made in response to climate change and climate change policy. (7) Analysis of adaptive decisions should recognize the second-best context of those decisions. (8) Climate change offers opportunity as well as risk. (9) All plausible futures should be explored. (10) Multiple methodological approaches should be accommodated. These lessons support two pieces of advice for the Third Assessment Report: (1) Work toward consensus, but not at the expense of thorough examination and reporting of the "tails" of the distributions of the future. (2) Integrated assessment is only one unifying methodology; others that can better accommodate those tails should be encouraged and embraced.
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Biogeochemistry 44 (1999), S. 119-134 
    ISSN: 1573-515X
    Schlagwort(e): atmospheric ; cloud water ; deposition ; ecosystem ; fixed nitrogen ; volcano
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract Precipitation, dry deposition, and cloud water deposition of fixed nitrogen (nitrate and ammonium ions) were measured on the Island of Hawaii. The first two were small N inputs, averaging 0.6±0.2 and 0.15±0.08 kg N ha−1 yr−1 respectively. We estimate cloud water deposition to be 8–22 kg inorganic N ha−1 yr−1. If an estimate of organic N is included, it may be as high as 50 kg N ha−1 yr−1. Additionally, cloud water deposition is of hydrological significance as it comprised 37% of the total water input. Cloud water interception was certainly lower in the past, as the developing ecosystem would have had less collection surface area. Cloud water samples that were associated with volcanic haze events were very concentrated in NO 3 − and constituted 60% of the annual cloud water N deposition. This NO 3 − probably originated from atmospheric N fixed thermally at the hot lava surface or from an interaction between lava and the ocean. If volcanically influenced samples are excluded from the analysis, the resulting cloud water deposition would have been 4–9 kg N ha−1 yr−1. The Pacific Ocean and Kilauea volcano may have a profound impact on the development of this terrestrial ecosystem, as sources of fixed nitrogen.
    Materialart: Digitale Medien
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Environmental monitoring and assessment 58 (1999), S. 151-172 
    ISSN: 1573-2959
    Schlagwort(e): GIS ; ground water vulnerability ; leaching index ; nitrate ; pesticide ; phosphorus ; potassium ; statistical analysis ; uncertainty
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Statistical methods and a Geographic Information System (GIS) were used to investigate potential indicators of ground water vulnerability to agricultural chemical contamination in a representative area of the Mississippi River alluvial aquifer. A total of 47 wells were sampled for analysis of nitrate, phosphorus, potassium, and 13 pesticides commonly-used in the area. Ten soil and hydrogeologic variables and five ground water vulnerability indices were examined to explain the variations of chemical concentrations. The results showed that no individual soil or hydrogeologic variables or their linear combinations could explain more than 25% of the variation of the chemical concentrations. A quadratic response surface model with the values of confining unit thickness, slope, soil permeability, depth to ground water, and recharge rate accounted for 62% of the variation of nitrate, 43% of P, and 83% of K, suggesting that the interactions among soil and hydrogeologic variables were significant. Observed trends of decreasing nitrate and P concentrations with increasing well depth and/or depth to ground water seemed to correlate with carbonate equilibrium in the aquifer and more reduced environment with depth. In view of uncertainties involved, it was recognized that the limitations associated with input data resolution used in GIS and the formulation of leaching indices limited their use for predicting ground water vulnerability. Misuse of pesticides could be another factor that would complicate the relationships between pesticide concentrations and the vulnerability indices.
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Environmental monitoring and assessment 58 (1999), S. 201-212 
    ISSN: 1573-2959
    Schlagwort(e): biomonitoring ; deposition ; metal smelter ; moss ; serial elution procedure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Heavy metal concentrations in Hylocomium splendens collected around a metal smelter in Latvia showed very high concentrations of Zn (〉200 μg/g), and elevated concentrations of Pb (38.3 μg/g) and Cu (18.3 μg/g). In an attempt to better evaluate the potential toxicity of the high Zn concentrations, a serial elution method was used to determine the concentrations of zinc in intercellular, extracellular exchangeable cell wall, intracellular, and particle fractions. The intercellular Zn concentrations represent the water soluble component of the total concentrations, and were low with no clear trends. Zn concentrations in the extra- and intracellular and particle fractions decreased exponentially from the pollutant source. Intracellular Zn concentrations in moss close to the emission source are within the range considered to be potentially toxic, from other single element exposure studies. The proportion of Zn in the relatively insoluble particle fraction, which is least associated with environmental risk, was greater closer to the pollution source, reaching 〉 30% in the oldest Hylocomium splendens segments.
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  • 19
    ISSN: 1573-2932
    Schlagwort(e): critical load ; deposition ; heavy metals ; persistent organic pollutants ; soil quality ; water quality
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract In the pilot study ESQUAD the impact of atmospheric deposition of three heavy metals (cadmium, copper and lead) and two persistent organic pollutants (benzo(a)-pyrene and lindane) on the quality of European soils and seawater has been calculated. Calculations have been made of atmospheric transport and deposition using a detailed emissions database for Europe. This enabled deposition maps to be produced to a resolution of approximately 50 km. The distribution of pollutant concentrations in forest soils was calculated for each grid cell using a database of soil property parameters in Europe. For the North Sea, a model was used to map long-term concentrations in water and sediment, which are due to atmospheric deposition and other, non-atmospheric sources. The model calculations allowed detailed comparisons of deposition fluxes and concentrations of the substances studied with critical loads and environmental quality threshold values, including critical loads. Although significant uncertainties were identified, the study gives insight in how threshold exceedance rates in Europe relate to pollutant type, threshold type, environmental compartment and chemophysical phase (adsorbed, dissolved). For all pollutants and for all compartments exceedances were calculated for at least some of the quality thresholds that were chosen.
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Water, air & soil pollution 115 (1999), S. 167-182 
    ISSN: 1573-2932
    Schlagwort(e): pesticides ; atmospheric transport ; modelling ; deposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Modelling of atmospheric transport and deposition of pesticides is presented and discussed. Modelling on regional scale builds on the existing knowledge gained in other air pollution fields. An overview of current modelling studies on transport and deposition on a regional scale (typically 30-3000 km) is given. From these studies it is concluded that the models are capable in simulating the spatial distribution of the concentrations and depositions. However, large uncertainties are present in this type of modelling and are for the greater part induced by the uncertainty in the emissions and subsequently in the exchange process parameterisations and the physicochemical properties needed in the parameterisations. Many more measurement data are needed to validate the models.
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  • 21
    ISSN: 1573-2932
    Schlagwort(e): atmospheric transport ; surface exchange ; deposition ; pesticides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract The current knowledge on atmospheric transport and deposition of pesticides is reviewed and discussed by a working group of experts during the Workshop on Fate of pesticides in the atmosphere; implications for risk assessment, held in Driebergen, the Netherlands, 22-24 April, 1998. In general there is a shortage of measurement data to evaluate the deposition and re-emission processes. It was concluded that the mechanisms of transport and dispersion of pesticides can be described similarly to those for other air pollution components and these mechanisms are rather well-known. Large uncertainties are present in the exchange processes at the interface between air and soil/water/vegetation. In all process descriptions the uncertainty in the physicochemical properties play an important role. Particularly those in the vapour pressure, Henry's law constant and its temperature dependency. More accurate data on physicochemical properties and particularly the temperature dependencies is needed.
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Environmental modeling and assessment 4 (1999), S. 217-234 
    ISSN: 1573-2967
    Schlagwort(e): climate change ; climate policy ; integrated assessment ; inverse modeling ; uncertainty
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract The Tolerable Windows Approach (TWA) to Integrated Assessments (IA) of global warming is based on external normative specifications of tolerable sets of climate impacts as well as proposed emission quotas and policy instruments for implementation. In a subsequent step, the complete set of admissible climate protection strategies which are compatible with these normative inputs is determined by scientific analysis. In doing so, minimum requirements concerning global and national greenhouse gas emission paths can be determined. In this paper we present the basic methodological elements of TWA, discuss its relation to more conventional approaches to IA like cost–benefit analyses, and present some preliminary results obtained by a reduced-form climate model.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Water, air & soil pollution 110 (1999), S. 313-333 
    ISSN: 1573-2932
    Schlagwort(e): Florida Everglades ; Lake Erie ; mercury ; paleoecology ; sediment cores ; uncertainty
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Increased recognition of the ecological damage of mercury (Hg) has focused attention on quantifying spatial and temporal patterns of Hg deposition. Studies are commonly based on core chronologies and use a combination of techniques to measure parameters such as bulk density, percent solids, Hg concentration, and radionuclide activity. Little attention is generally devoted to the propagated error associated with these measurements. We identified the impact of sources of uncertainty on stratigraphic Hg determinations for Florida Everglades and Lake Erie cores. Large errors may be introduced by converting wet sample Hg content to dry-weight concentrations. Drying of sediments at 55 °C caused Hg losses of 18%. Samples, air-dried at room temperature, retained considerable moisture and required corrections for remaining water content. Frozen sediments did not lose Hg during a 72-day storage. Random error in radionuclide analysis of cores resulted in dating uncertainty of ±1.2 yr in 10 yr old deposits. This error increased to ±20 yr in 100 yr old sediments. Propagation of small errors in each step of the analysis (while adhering to strict QA/QC criteria) produced compounded uncertainties of ±11 and ±29% in Hg concentrations under different analytical rigor, and errors of up to ±73% in Hg accumulation rates in older sediments. Enrichment factors, comparing uncertain recent and historic Hg accumulation rates, differed by as much as ±48%. Uncertainty in paleoecological studies of mercury needs to be documented in order to correctly evaluate trends and remediation efforts.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 24
    ISSN: 1573-2932
    Schlagwort(e): acari ; alkaline ; deposition ; epiphytes ; Gamasida ; Oribatida ; Scots pine forest
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract The effect of alkaline deposition produced by the ‘Kujawy’ cement and lime factory in Bielawy, Poland, on the mites in young Scots pine forests (plants class Vaccinio-Piceetea) was investigated. The concentration of calcium in tree bark and epiphytes, which provide a habitat for mites, as well as in soil was the lowest in the control plot, and increased in the direction of the factory. A high concentration of calcium correlated with an absence of lichens from tree bark, but a medium concentration was associated with a higher species number of lichens. The density of arboreal mites and the species number of Oribatida were the highest in the control plot and decreased when getting closer to the factory. In a highly contaminated plot, the density of soil mites was lower, while in a medium contaminated plot it was higher than in the control plot. In the contaminated plots, the species number of soil Oribatida and Gamasida was lower than in the control plot, except in a least contaminated plot where the number of gamasid species was higher than in the control plot. Some species were sensitive to calcium, others were sensitive to a high concentration but tolerated medium and small concentrations of this element, and yet others tolerated calcium. The arboreal mites reacted to alkaline deposition more distinctly than soil mites.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 25
    ISSN: 1573-2932
    Schlagwort(e): anthropogenic sources ; deposition ; fossil fuels ; particulates ; precipitation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Precipitation was collected on an event basis from July 1994 to August 1995 at towns around the capital Dhaka of Bangladesh. The major chemical components were determined by atomic absorption spectrophotometry, UV-Visible spectrophotometry and ion selective electrode method. The concentrations of nitrate and sulphate were found to be below the minimum detection limit of 1.0 mg L- 1; the concentrations of Cl-, Na+, K+, Ca+2, Mg+2 and NH4+ ranged from 〈1.0–3.03, 0.14–1.70, 0.04–0.37, 0.04–1.30, 〈0.02–0.20 and 〈0.10–2.33 mg L-1, respectively. The values of pH and conductivity ranged from 4.80–6.74 and 3.3–37.5 μS cm-1, respectively.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Water, air & soil pollution 112 (1999), S. 1-19 
    ISSN: 1573-2932
    Schlagwort(e): circular flume ; deposition ; flocculation ; harbour mud
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract The deposition and floc formation of fine sediment from Port Stanley harbour were investigated using a rotating circular flume. Seasonal effects, storage time and shear stress were varied. Biological activity was monitored as an aid to explain the results. Sample storage in the flume resulted in increased flocculation for the two fines samples. A sample with a higher percentage of silt did not flocculate to the same extent as the finer samples. Flocculation was also influenced by the presence of bacteria; however further investigation is required to determine their relative importance compared to the presence of fines.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 27
    ISSN: 1573-2932
    Schlagwort(e): canopy resistance ; deposition ; emission ; micro-meterological approach ; nitrogen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract The present study aims to establish the annual NH3 deposition to an inland heathland in Denmark using a micro-meterological approach with passive wind-vane flux samplers. The integrating samplers were replaced at weekly intervals from May 1995 to May 1996. The average concentration, 2.05 μg m-3 at the heathland is at a moderate level when compared to heathlands in other parts of Europe. The average deposition velocity was 0.83 cm s-1 which is within the range of depositon velocities found for other heathlands in Europe. The average canopy resistance was found to be relatively high, 61 s -1. The measurements yielded a total NH3-N deposition of 2.4 (± 0.9) kg ha-1 yr-1 with a data coverage of 71% for 1995/1996. In 40% of this time the flux is regarded as zero because the flux is not significant different from zero. In 60% of this time the significant fluxes varied from –0.052 μg m-2 s-1 (deposition equal 16.4 kg N ha-1 yr-1) to 0.089 μg m-2 s-1 (emission equal 28.2 kg N ha-1 yr-1). The method is only able to direct measure significant fluxes down to the equivalence of 0.010 μg m-2 s-1 (approximately 3.2 kg ha-1 yr-1). Therefore the exact deposition cannot be determined by the applied method at very low deposition sites such as a coastal heathland in Denmark. In a high-deposition area as in the central Netherlands the method gave significant fluxes with a 100% data coverage for a two month period.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 28
    ISSN: 1573-2932
    Schlagwort(e): atmospheric fate ; atmospheric transport ; deposition ; emission ; long-range transport ; pesticides ; registration ; remote area ; risk assessment ; transformation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract The Health Council of the Netherlands organised an international workshop on the fate of pesticides in the atmosphere and possible approaches for their regulatory environmental risk assessment. Approximately forty experts discussed what is currently known about the atmospheric fate of pesticides and major gaps in our understanding were identified. They favoured a tiered approach for assessing the environmental risks of atmospheric dispersion of these chemicals. In the first tier a pesticide's potential for emission during application, as well as its volatilisation potential should be assessed. Estimates of the former should be based on the application method and the formulation, estimates of the latter on a compound's solubility in water, saturated vapour pressure and octanol/water partition coefficient. Where a pesticide's potential for becoming airborne exceeds critical values, it should be subjected to a more rigorous second tier evaluation which considers its toxicity to organisms in non-target areas. This evaluation can be achieved by calculating and comparing a predicted environmental concentration (PEC) and a predicted no-effect concentration (PNEC). By applying an extra uncertainty factor the PNEC can be provisionally derived from standard toxicity data that is already required for the registration of pesticides. Depending on the distance between the source and the reception area, the PEC can be estimated for remote areas using simple dispersion, trajectory type models and for nearby areas using common dispersion models and standard scenarios of pesticide use. A pesticide's atmospheric transport potential is based on factors such as its reaction rate with OH radicals. It should be used to discriminate between those compounds for which only the risks to nearby ecosystems have to be assessed, and those for which the risks to remote ecosystems also have to be determined. The participants were of the opinion that this approach is, in principle, scientifically feasible, although the remaining uncertainties are substantial. Further field and laboratory research is necessary to gain more reliable estimates of the physico-chemical properties of pesticides, to validate and improve environmental fate models and to validate the applicability of standard toxicity data. This will increase both the accuracy of and our confidence in the outcome of the risk assessment.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 29
    Digitale Medien
    Digitale Medien
    Springer
    Water, air & soil pollution 115 (1999), S. 21-70 
    ISSN: 1573-2932
    Schlagwort(e): atmospheric transport ; current-use pesticides ; deposition ; field measurements ; long-range transport ; monitoring ; organochlorine pesticides ; pesticides ; rainwater
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Recently, evidence has accumulated that the extensive use of modern pesticides results in their presence in the atmosphere at many places throughout the world. In Europe over 80 current-use pesticides have been detected in rain and 30 in air. Similar observations have been made in North America. The compounds most often looked for and detected are the organochlorine insecticide lindane and triazine herbicides, especially atrazine. However, acetanilide and phenoxyacid herbicides, as well as organophosphorus insecticides have also frequently been found in rain and air. Concentrations in air normally range from a few pg/m3 to many ng/m3. Concentrations in rain generally range from a few ng/L to several µg/L. In fog even higher concentrations are observed. Deposition varies between a few mg/ha/y and more than 1 g/ha/y per compound. However, these estimates are usually based on the collection and analysis of (bulk) precipitation and do not include dry particle deposition and gas exchange. Nevertheless, model calculations, analysis of plant tissue, and first attempts to measure dry deposition in a more representative way, all indicate that total atmospheric deposition probably does not normally exceed a few g/ha/y. So far, little attention has been paid to the presence of transformation products of modern pesticides in the atmosphere, with the exception of those of triazine herbicides, which have been looked for and found frequently. Generally, current-use pesticides are only detected at elevated concentrations in air and rain during the application season. The less volatile and more persistent ones, such as lindane, but to some extent also triazines, are present in the atmosphere in low concentrations throughout the year. In agricultural areas, the presence of modern pesticides in the atmosphere can be explained by the crops grown and pesticides used on them. They are also found in the air and rain in areas where they are not used, sometimes even in remote places, just like their organochlorine predecessors. Concentrations and levels are generally much lower there. These data suggest that current-use pesticides can be transported through the atmosphere over distances of tens to hundreds, and sometimes even more than a thousand kilometres. The relative importance of these atmospheric inputs varies greatly. For mountainous areas and remote lakes and seas, the atmosphere may constitute the sole route of contamination by pesticides. In coastal waters, on the other hand, riverine inputs may prevail. To date, little is known about the ecological significance of these aerial inputs.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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