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691.
692.
In the investigation of soil cover design options for final decommissioning of reactive mine waste, it is often necessary to analyze or predict the anticipated cover performance as a function of the cost of implementation, which is governed by the type, number and thickness of the layers in the cover system. An example of such investigation is presented in this study where one-dimensional evaporation from hypothetical moisture-retaining cover systems is simulated to assess the influence of several cover properties and hydrogeologic parameters on performance. The commercially available transient flow model, SoilCover, was used to compute suction and water content profiles for different cover design scenarios. The predicted water content profile and porosity of layers were then used to estimate the oxygen diffusion coefficients of the various layers. The oxygen diffusion coefficients were used to estimate oxygen flux through the cover systems. The oxygen flux was, in turn, related to the maximum acid flux. The studied cover and hydrogeologic parameters included soil type, thickness of barriers, and water table elevation. Two types of infiltration and oxygen barrier and two types of capillary layer with different thicknesses were studied. The water table was either kept constant at the base of the waste (tailings) or dropped by 0.5, 1, 2, and 3m over 120 days. The results showed that the relationship between water table depression and the thickness of capillary layers, on one hand, and desaturation of the infiltration and oxygen barrier, on the other, is not linear. Relationships between oxygen flux and barrier thickness and between cost increase and performance improvement of the studied cover systems are presented. Finally, a method that outlines steps for site-specific and economically feasible design of multi-layer cover systems is introduced. 相似文献
693.
Fast economic and social changes in recent years in China have brought massive expansion, redevelopment, and restructuring
of cities. These changes offer cities the opportunity to improve environmental quality through urban green spaces (UGSs) and
to address the challenges of meeting community aspirations. This study explored peoples’ minds concerning UGSs in Guangzhou
city in south China in relation to the following: (1) knowledge and perception of 25 ecosystem services and 8 negative impacts;
(2) attitude toward site condition and management; (3) expectation of landscape design; and (4) preference ranking of venues.
A questionnaire was designed to solicit opinions from 340 respondents randomly chosen from residents living in the study area.
The results indicated widespread recognition of ecosystem services and strong support of UGS programs. Negative responses
were weakly expressed. Amelioration of urban microclimate and environmental quality were emphasized. Environmental functions
stressed in publicity programs, together with aggravating environmental problems in the city, tended to focus respondents’
attention on UGS benefits. Wildlife habitat, species conservation and other natural ecosystem services drew limited concerns.
Awareness of economic benefits was very low. Visual-landscape contributions with strong preference for naturalistic design
and recreational benefits were highlighted. Compared with other countries, Guangzhou residents were characterized by visual–scenic–recreation
orientation and pragmatic–utilitarian perception of UGSs, reflecting underlying differences in the understanding of inherent
ecosystem services of green spaces. Relevant UGS policies and practices could adopt the approaches of market survey, citizen
participation, and precision planning in order to meet increasingly mature and refined demands. Citizens’ understanding of
high-order ecosystem services could be enhanced to encourage appreciation of nature and their associated benefits. 相似文献
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695.
A water quality monitoring network design methodology for the selection of critical sampling points: Part II 总被引:1,自引:0,他引:1
Strobl RO Robillard PD Day RL Shannon RD McDonnell AJ 《Environmental monitoring and assessment》2006,122(1-3):319-334
In order to resolve the spatial component of the design of a water quality monitoring network, a methodology has been developed to identify the critical sampling locations within a watershed. This methodology, called Critical Sampling Points (CSP), focuses on the contaminant total phosphorus (TP), and is applicable to small, predominantly agricultural-forested watersheds. The CSP methodology was translated into a model, called Water Quality Monitoring Station Analysis (WQMSA). It incorporates a geographic information system (GIS) for spatial analysis and data manipulation purposes, a hydrologic/water quality simulation model for estimating TP loads, and an artificial intelligence technology for improved input data representation. The model input data include a number of hydrologic, topographic, soils, vegetative, and land use factors. The model also includes an economic and logistics component. The validity of the CSP methodology was tested on a small experimental Pennsylvanian watershed, for which TP data from a number of single storm events were available for various sampling points within the watershed. A comparison of the ratios of observed to predicted TP loads between sampling points revealed that the model's results were promising. 相似文献
696.
The Stream and Its Altered Valley: Integrating Landscape Ecology into Environmental Assessments of Agro-Ecosystems 总被引:2,自引:0,他引:2
Little is known about the importance of landscape and land cover to the implementation and performance of agricultural conservation projects designed to improve stream quality. In our study, we addressed the potential importance of landscape and land cover to conservation projects by measuring variation across 191 μ-basins (100–2400 ha) and integrating the observed variation into a study design aimed at determining the effectiveness of conservation projects. Our findings indicate that there are strong gradients across which landscape and land cover attributes vary. Land cover varied along a gradient of agricultural intensity, basin morphometry across gradients of stream closure and basin size, basin substrate was described by variation in drumlin formation, glacial landform type, and soil drainage, while agricultural conservation projects varied according to the level of project implementation. Correlation of these gradients found several associations between landscape and land cover, indicating that agricultural intensity was being constrained predominantly by drumlin formation and glacial landform type. Landscape and land cover did not appear to be determining factors in the implementation of conservation projects by land owners. Based on these findings we chose 32 μ-basins which represented the variability along each of the defined gradients for further study. We conclude that landscape scale variables demonstrate important variation and covariation that can and should be integrated into study designs for the assessment of streams and human activities affecting streams. 相似文献
697.
698.
针对小型污水处理系统的特点,着眼于提高处理效率、降低能耗、减少产泥、方便管理、节省占地等原则,对其构筑物、设备及工艺的设计经验和发展趋势进行了较为全面的总结,并提出了相应的具体设计建议. 相似文献
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700.