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531.
Thuyet D. Bui Jim Luong-Van Stefan W. Maier Chris M. Austin 《Environmental monitoring and assessment》2013,185(10):8715-8731
Coastal shrimp farming may lead to the contamination of sediments of surrounding estuarine and marine ecosystems as shrimp farm effluent often contains high levels of pollutants including a range of organic compounds (from uneaten feed, shrimp feces, and living and dead organisms) which can accumulate in the sediments of receiving waterways. The assessment and monitoring of sediment quality in tidal creeks receiving shrimp farm effluent can support environmental protection and decision making for sustainable development in coastal areas since sediment quality often shows essential information on long-term aquatic ecosystem health. Within this context, this paper investigates nutrient loadings in the sediments of tidal creeks receiving shrimp farm effluent in Quang Ninh, Vietnam, which now have a high concentration of intensive and semi-intensive shrimp farms. Sediment samples taken from inside creek sections directly receiving effluent from concentrated shrimp farms (IEC), from main creeks adjacent to points of effluent discharge outside concentrated shrimp farms (OEC), and few kilometers away from shrimp farms (ASF) as reference sites were collected and analyzed before and after shrimp crops to investigate spatial and temporal variation. The results showed that there were statistically significant differences in the concentrations of total nitrogen, total phosphorus, and total organic carbon among IEC, OEC, and ASF sites while the seasonal variation being limited over study times. A sediment nutrient index (SNI) computed from coefficient scores of the factor analysis efficiently summarizes sediment nutrient loads, which are high, albeit quite variable, in canals directly receiving effluents from farms but then decline sharply with distance from shrimp farms. The visualization and monitoring of sediment quality data including SNI on maps can strongly support managers to manage eutrophication at concentrated shrimp farming areas, contributing to sustainable development and management at coastal zones. 相似文献
532.
533.
Gheorghe Maria Dragos-Nicolae Stefan 《Journal of Loss Prevention in the Process Industries》2010,23(1):112-126
The safety in operation of a fixed-bed catalytic reactor remains a sensitive issue when a highly exothermic reaction is conducted and various process development elements such as controllability, stability, risk, and economic aspects are considered. Several model-based methods are used to estimate the safe operating region limits. Nominal conditions are set to limit the hot spot in the tubular reactor and avoid excessive thermal sensitivity to variations in the process parameters. When the catalyst or its characteristics are changed, the operating conditions have to be adjusted accordingly. The safety problem becomes more important when the production optimization requires setting the nominal operating point in the vicinity of the safety limits. This paper investigates the advantages as well as the precautions that need to be taken when using a more sophisticated model-based global sensitivity criterion (MV of Morbidelli & Varma) to routinely update the runaway critical conditions when changes in the investigated system frequently occur. A concrete example is provided for the case of an industrial fixed-bed catalytic reactor for nitrobenzene hydrogenation in vapour-phase. The analysis points out the discrepancies in predicting the runaway boundaries for complex processes between precise sensitivity-based MV-method and shortcut methods, and the importance of accounting for parameter uncertainty for both evaluation of the confidence region around the runaway boundaries and for the optimal set-point location. The close connection between the operating risk limits and the process kinetics is also highlighted even if the reactor geometry and the main flow conditions are kept unchanged. 相似文献
534.
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
535.
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
536.
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
537.
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538.
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
539.
The input of acidity to Swedish forest soils through forestry between 1955 and 2010 is compared with the acid input from atmospheric deposition. Depending on region, input of acidity from forestry was the minor part (25–45%) of the study period’s accumulated acid input but is now the dominating source (140–270 molc ha−1 year−1). The net uptake of cations due to the increase in standing forest biomass, ranged between 35 and 45% of the forestry related input of acidity while whole-tree harvesting, introduced in the late 1990s, contributed only marginally (< 2%). The geographical gradient in acid input is reflected in the proportion of acidified soils in Sweden but edaphic properties contribute to variations in acidification sensitivity. It is important to consider the acid input due to increases in standing forest biomass in acidification assessments since it is long-term and quantitatively important.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01540-y. 相似文献
540.
Medić Dragana V. Sokić Miroslav D. Nujkić Maja M. Đorđievski Stefan S. Milić Snežana M. Alagić Slađana Č. Antonijević Milan M. 《Journal of Material Cycles and Waste Management》2023,25(2):1008-1018
Journal of Material Cycles and Waste Management - To increase the degree of cobalt (Co) extraction, the process of the cathode material leaching was performed in a sulfuric acid (H2SO4) solution... 相似文献