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排序方式: 共有253条查询结果,搜索用时 15 毫秒
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Monika Schaffner Hans-Peter Bader Ruth Scheidegger 《Environment, Development and Sustainability》2011,13(2):403-422
With the worldwide intensification of agriculture, non-point source pollution of surface waters has become a pressing issue.
Conventional river water quality models consider non-point sources as accumulated entries into the rivers and do not investigate
into the processes generating the pollution at its source, thus preventing the determination of effective mitigation measures.
The models require extensive data inputs, which is a deficiency in many developing and emerging countries with limited data
availability. The current study applies a Material Flow Model as a complementary approach to quantify non-point source pollution
from agricultural areas. Rice farming in the Thachin River Basin is presented as a case study, with a focus on nutrients.
The total nitrogen and phosphorus flows from rice farming to the river system are quantified, the key parameters influencing
these flows are determined and potential mitigation measures are discussed. The results show that rice contributes considerable
nutrient loads to the Thachin River Basin. Scenario simulations demonstrate that a significant nutrient load reduction could
be achieved by following the official recommendations for fertilizer application, thus confirming the local efforts to introduce
best management practice. Our results underline the importance of non-point source pollution control in intensive agricultural
areas, particularly of tropical lowland delta areas such as the Central Plains of Thailand. The specific benefit of applying
a Material Flow Model in this context is that with limited data availability, one can reach an understanding of the system
and gain a first overview over its key pollution problems. This can serve as supportive basis for determining consecutive
in-depth research requirements. 相似文献
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Confronting limitations: new solutions required for urban water management in Kunming City 总被引:1,自引:0,他引:1
Huang DB Bader HP Scheidegger R Schertenleib R Gujer W 《Journal of environmental management》2007,84(1):49-61
Despite continuous investment and various efforts to control pollution, urban water environments are worsening in large parts of the developing world. In order to reveal potential constraints and limitations of current practices of urban water management and to stimulate proactive intervention, we conducted a material flow analysis of the urban water system in Kunming City. The results demonstrate that the current efficiency of wastewater treatment is only around 25% and the emission of total phosphorous from the city into its receiving water, Dianchi Lake, is more than 25 times higher than its estimated tolerance. With regard to the crisis of water quantity and quality, the goal of a sustainable urban water environment cannot be attained with the current problem-solving approach in the region due to the technical limitations of the conventional urban drainage and treatment systems. A set of strategies is therefore proposed. The urban drainage system in Zurich is used as a reference for a potential best-available technology for conventional urban water management (BAT) scenario in terms of its low combined frequency of sewer overflow. 相似文献
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This paper develops and tests hypotheses concerning some psychological correlates of role ambiguity and role conflict in a population that has not been extensively studied in relation to stress, union stewards. Survey data on role ambiguity and role conflict, the indicators of stress, were collected from 285 stewards at the local union steward meeting, with the stewards perceiving a moderate amount of role ambiguity and perceiving a lesser amount of role conflict. The stewards were also asked about their role expectations, their motivations for remaining a steward, their grievance handling strategies, and their affective commitment toward the union and employer. Each of those four sets of variables was hypothesized to be related to role ambiguity and role conflict and each was influential in explaining variance. As predicted, those stewards who were more motivated to remain stewards for personal reasons had both higher role ambiguity and higher role conflict. Further, the conditions of being more motivated to remain a steward to help the union and employees and having higher union commitment were associated with lower role conflict, but, opposite to the hypotheses, higher role ambiguity. 相似文献
69.
Christopher J. Richards Honesto Roaza Ruth Montgomery Roaza 《Journal of the American Water Resources Association》1993,29(5):847-853
ABSTRACT: The Floridan Aquifer is the primary source of water in the coastal area of Santa Rosa County, Florida. In order to optimize well field design and analyze aquifer stress problems, the USGS MODFLOW code (McDonald and Harbaugh, 1988) is applied to develop a numerical computer model of the aquifer. The Geographical Information System (GIS) is the primary tool used in the development of the model grid, performance of the modeling procedure, and model analysis. The GIS is used in generating multiple grids in which to simulate both regional scale and local scale flow. The grid topology is recorded in geographic coordinates which facilitates geo-referencing and orientation of the grid to base maps and data coyerages. The GIS allows data transfer from various coverages to the nodes of the block centered grid where hydrogeologic information is stored as attributes to the grid coverage. From this grid coverage, pertinent information is queried within the GIS environment and used to generate the input files for the MODFLOW simulation. After MODFLOW execution, simulated heads and drawdown are imported into the grid coverage where residual error and recharge rates can be calculated. Contoured surfaces are then created for selected data sets including simulated heads, drawdown, residual error, and recharge rates. Model calibration is conducted utilizing the GIS to generate and process data sets associated with model simulations. 相似文献
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Investigations using chlorophyll fluorescence induction kinetics provide the parameters Rfd, L, and Ap to characterize different specifications of the photosynthetic system (PS). The application of ozone, with concentrations between 100 microg m(-3) and 2000 microg m(-3) to spruce in closed chambers yields a reduction of Rfd between 6% and 23% for the current year's needles, which indicates a reduced potential photosynthetic capacity. Further measurements on the current year's needles of spruce of the damage classes S0/S1, S2 and S3 show also a reduction of Rfd of between 7% and 14% in 2 successive years. In addition, the parameter L increases for damaged trees by between 11% and 49%, indicating a change of the chlorophyll content and of the internal energy distribution between PSI and PSII. As no effect of L can be observed with ozone fumigation, it is concluded that the change of some specifications of the PS can be simulated well by ozone fumigation (e.g. Rfd) while other specifications cannot (e.g. L). 相似文献