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541.
Ines Dombrowsky Ram Almog Nir Becker Eran Feitelson Simone Klawitter Stefan Lindemann Natalie Mutlak 《Environmental management》2010,45(5):1112-1126
The basin scale has been promoted universally as the optimal management unit that allows for the internalization of all external
effects caused by multiple water uses. However, the basin scale has been put forward largely on the basis of experience in
temperate zones. Hence whether the basin scale is the best scale for management in other settings remains questionable. To
address these questions this paper analyzes the economic viability and the political feasibility of alternative management
options in the Kidron/Wadi Nar region. The Kidron/Wadi Nar is a small basin in which wastewater from eastern Jerusalem flows
through the desert to the Dead Sea. Various options for managing these wastewater flows were analyzed ex ante on the basis
of both a cost benefit and a multi-criteria analysis. The paper finds that due to economies of scale, a pure basin approach
is not desirable from a physical and economic perspective. Furthermore, in terms of political feasibility, it seems that the
option which prompts the fewest objections from influential stakeholder groups in the two entities under the current asymmetrical
political setting is not a basin solution either, but a two plant solution based on an outsourcing arrangement. These findings
imply that the river basin management approach can not be considered the best management approach for the arid transboundary
case at hand, and hence is not unequivocally universally applicable. 相似文献
542.
Saleh K. Al Mansoori Endurance Itsekiri Stefan Iglauer Christopher H. Pentland Branko Bijeljic Martin J. Blunt 《International Journal of Greenhouse Gas Control》2010,4(2):283-288
We measure the trapped non-wetting phase saturation as a function of the initial saturation in sand packs. The application of the work is for CO2 storage in aquifers where capillary trapping is a rapid and effective mechanism to render injected CO2 immobile. The CO2 is injected into the formation followed by chase brine injection, or natural groundwater flow, which displaces and traps CO2 on the pore scale as a residual immobile phase. Current models to predict the amount of trapping are based on experiments in consolidated media, while CO2 may be stored in relatively shallow, poorly consolidated systems. We use analogue fluids at ambient conditions. The trapped saturation initially rises linearly with initial saturation to a value of approximately 0.13 for oil/water systems and 0.14 for gas/water systems. There then follows a region where the residual saturation is constant with further increases in initial saturation. This behaviour is not predicted by the traditional literature trapping models, but is physically consistent with unconsolidated media where most of the larger pores can easily be invaded at relatively low saturation and there is, overall, relatively little trapping. A good match to our experimental data was achieved with the trapping model proposed by Aissaoui. 相似文献
543.
Acidification of soils and surface waters caused by acid deposition is still a major problem in southern Scandinavia, despite
clear signs of recovery. Besides emission control, liming of lakes, streams, and wetlands is currently used to ameliorate
acidification in Sweden. An alternative strategy is forest soil liming to restore the acidified upland soils from which much
acidified runoff originates. This cost–benefit analysis compared these liming strategies with a special emphasis on the time
perspective for expected benefits. Benefits transfer was used to estimate use values for sport ffishing and nonuse values in terms of existence values. The results show that large-scale forest soil liming is not socioeconomically profitable, while
lake liming is, if it is done efficiently—in other words, if only acidified surface waters are treated. The beguiling logic
of “solving” an environmental problem at its source (soils), rather than continuing to treat the symptoms (surface waters),
is thus misleading. 相似文献
544.
Stefan Fiedler Gerd Pfister Karl-Werner Schramm 《Environmental science and pollution research international》2010,17(2):420-428
Background, aim, and scope
Fluorotelomer alcohols (FTOH) are widely used substances that were detected even in remote regions of the world. For the determination of FTOH in the atmosphere, appropriate sampling techniques are needed. In this study, triolein-filled low-density polyethylene tubes were used as semipermeable membrane devices (SPMD) and tested for their suitability as passive air samplers for FTOH. 相似文献545.
Nicole Schütze Xiaoyin Zhong Stefan Kirschbaum Iustinian Bejan Ian Barnes Thorsten Benter 《Atmospheric environment (Oxford, England : 1994)》2010,44(40):5407-5414
Relative kinetic studies have been performed on the reactions of Cl atoms with a series of methyl alkyl esters in a 405-liter borosilicate glass chamber at (298 ± 3) K and one atmosphere of synthetic air using in situ FTIR spectroscopy to monitor the reactants. Rate coefficients (in units of cm3 molecule?1 s?1) were determined for the following compounds: methyl acetate (2.48 ± 0.58) × 10?12; methyl propanoate (1.68 ± 0.36) × 10?11; methyl butanoate (4.77 ± 0.87) × 10?11; methyl pentanoate (7.84 ± 1.15) × 10?11; methyl hexanoate (1.09 ± 0.31) × 10?10; methyl heptanoate (1.56 ± 0.37) × 10?10; methyl cyclohexane carboxylate (3.32 ± 0.76) × 10?10; methyl-2-methyl butanoate (9.41 ± 1.39) × 10?11.In addition rate coefficients (in units of 10?11 cm3 molecule?1 s?1) have been obtained for the reactions of OH radicals with the following compounds: methyl butanoate (3.55 ± 0.71), methyl pentanoate (5.41 ± 1.08), and methyl-2-methyl butanoate (4.08 ± 0.82).Using the kinetic rate data tropospheric lifetimes for the methyl alkyl esters with respect to their reactions with OH, and Cl have been estimated for typical ambient air concentrations of these oxidants. 相似文献
546.
William R. Herb Omid Mohseni Heinz G. Stefan 《Journal of the American Water Resources Association》2009,45(5):1164-1178
Abstract: A numerical model has been developed to simulate the hydraulic and heat transfer properties of a stormwater detention pond, as part of a simulation tool to evaluate thermal pollution of coldwater streams from stormwater runoff. The model is dynamic (unsteady) and based on principles of fluid mechanics and heat transfer. It is driven by hourly weather data, and specified inflow rates and temperatures. To calibrate and validate the pond model field data were collected on a commercial site in Woodbury, Minnesota. The relationship between pond inflow and outflow rates to precipitation was effectively calibrated using continuously recorded pond levels. Algorithms developed for surface heat transfer in lakes were found to be applicable to the pond with some modification, resulting in agreement of simulated and observed pond surface temperature within 1.0°C root mean square error. The use of an unshaded pond for thermal mitigation of runoff from paved surfaces was evaluated using the pond model combined with simulated runoff from an asphalt parking lot for six years of observed rainfall events. On average, pond outflow temperature was 1.2°C higher than inflow temperature, but with significant event‐to‐event variation. On average, the pond added heat energy to runoff from an asphalt parking lot. Although the pond added total heat energy to runoff, it did reduce the rate of heat outflow from the pond by an order of magnitude due to reductions in volumetric outflow rate compared with the inflow rate. By reducing the rate of heat flow, the magnitude of temperature impacts in a receiving stream were also reduced, but the duration of impacts was increased. 相似文献
547.
Two sets of experiments on typical Class G well cement were carried out in the laboratory to understand better the potential processes involved in well leakage in the presence of CO2. In the first set, good-quality cement samples of permeability in the order of 0.1 μD (10?19 m2) were subjected to 90 days of flow through with CO2-saturated brine at conditions of pressure, temperature and water salinity characteristic of a typical geological sequestration zone. Cement permeability dropped rapidly at the beginning of the experiment and remained almost constant thereafter, most likely mainly as a result of CO2 exsolution from the saturated brine due to the pressure drop along the flow path which led to multi-phase flow, relative-permeability effects and the observed reduction in permeability. These processes are identical to those which would occur in the field as well if the cement sheath in the wellbore annulus is of good quality. The second set of experiments, carried out also at in situ conditions and using ethane rather than CO2 to eliminate any possible geochemical effects, assessed the effect of annular spaces between wellbore casing and cement, and of radial cracks in cement on the effective permeability of the casing-cement assemblage. The results show that, if both the cement and the bond are of good quality, the effective permeability of the assemblage is extremely low (in the order of 1 nD, or 10?21 m2). The presence of an annular gap and/or cracks in the order of 0.01–0.3 mm in aperture leads to a significant increase in effective permeability, which reaches values in the range of 0.1–1 mD (10?15 m2). The results of both sets of experiments suggest that good cement and good bonding with casing and the surrounding rock will likely constitute a good and reliable barrier to the upward flow of CO2 and/or CO2-saturated brine. The presence of mechanical defects such as gaps in bonding between the casing or the formation, or cracks in the cement annulus itself, leads to flow paths with significant effective permeability. This indicates that the external and internal interfaces of cements in wells would most probably constitute the main flow pathways for fluids leakage in wellbores, including both gaseous/supercritical phase CO2 and CO2-saturated brine. 相似文献
548.
In line with the aims of waste management, the handling of waste should hinder any damage to the environment as much as possible. There are a number of approaches for solving this action in practice, e.g. different treatment technologies for residual waste, from which the most favourable should be chosen. We have several different methods for supporting such choices. An evaluation of studies published in recent years that assess waste management measures has clearly showed that the impact on the environment alone is not a sufficient basis for decision-making. In most cases, the cost aspect is also of primary concern while the technical implementation and social aspects also have to be taken into consideration. In recent years a great number of assessment methods have been developed as tools in the decision-making process. However, the multitude of methods leads to different results depending on the methods, parameters and criteria of the research. The following paper will characterise the most important decision-making concepts, such as the Life Cycle Assessment, Product Line Analysis, Cost-Benefit Analysis, Scoring Model, etc. Examples will show how these methods can be applied to the issues of waste management. The conclusion will describe the current state of development for waste management applications. 相似文献
549.
Lars C. Larsen Kim C. Zambrano Helle Christiansen Almut Köhler Ulrich Karlson Stefan Trapp 《Environmental Sciences Europe》2001,13(4):227-236
In Axelved, Denmark, an abandoned gas filling station serves as a test field for phytoremediation. Laboratory studies accompany the project. The toxicity of fresh and weathered gasoline and diesel to willow and poplar trees was studied by use of a tree transpiration toxicity test. The correlation between diesel content in soil and decrease in willow tree transpiration (Salix viminalis x schwerinii) was highly significant (r 2=0.81, n=19). the EC50 (50% inhibition of transpiration) for the sum of hydrocarbons (HC) was determined to be 3910 mg/kg (95% confidence interval from 2900 to 5270 mg/kg). The EC10 was 810 mg/kg (95% confidence interval 396 to 1660 mg/kg). The results were verified with artificially mixed diesel and gasolinecontaminated soils and two willow and one poplar species (S. viminalis, S. alba andPopulus nigra). The degradation of radiolabeledm-xylene was studied with and without willows. The compound was readily degraded. Willow trees accelerated the elimination, but mainly due to the volatilization ofm-xylene. Model studies provided the result that biodegradation in soil is the fastest elimination process at the site, but it is limited by the availability of electron acceptors. The pollutants are almost persistent in the groundwater, but in aerated soil, 10000 mg/kg hydrocarbons at 1 m depth are degraded within 13 years. The main effect of willows on the pollutants’ persistence is that willows transpire water, lower the groundwater level and aerate the soil, hereby speeding up biodegradation. 相似文献
550.
Transformation of diclofenac by the indigenous microflora of river sediments and identification of a major intermediate 总被引:1,自引:0,他引:1
Diclofenac is a non-steroidal anti-inflammatory drug, which tends to be relatively persistent in the environment. Now, a fixed-bed column bioreactor filled with sediment from the creek Münzbach (Freiberg/Saxony) under aerobic conditions showed rapid removal of diclofenac in a concentration range of 3-35 microM without previous adaptation. The conversion of higher concentrations up to 260 microM was accompanied by conspicuously decreased turnover rates indicating a toxic effect of this drug or its resulting metabolic burden on the indigenous microflora. A major metabolite occurred transiently and was identified by NMR and MS to be the p-benzoquinone imine of 5-hydroxydiclofenac. Abiotic adsorption to the biofilm was shown to determine the further fate of this reactive product of 5-hydroxydiclofenac (aut-)oxidation. The apparent lack of a degradative potential for this compound as well as the failure to detect an enrichment of diclofenac-depleting microbial activity both indicate a cometabolic nature of diclofenac transformation. 4'-Hydroxy-diclofenac, the favoured transformation product of eucaryotic diclofenac metabolism, could not be identified. The ability to convert diclofenac was shown to be widespread among biofilms from different river sediments, but measured rates obviously do not correlate with the total microbial activity. In addition, application of sediments from locations exposed to communal waste water effluents did not indicate any form of adaptation measured as an increased specific diclofenac depletion rate. 相似文献