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31.
Mark C. Scott Gene S. Helfman Matthew E. McTammany E. Fred Benfield Paul V. Bolstad 《Journal of the American Water Resources Association》2002,38(5):1379-1392
ABSTRACT: Streams integrate biogeochemical processes operating at broad to local spatial scales and long term to short term time scales. Humans have extensively altered those processes in North America, with serious consequences for aquatic ecosystems. We collected data on Upper Tennessee River tributaries in North Carolina to: (1) compare landuse and landscape geomorphology with respect to their ability to explain variation in water quality, sedimentation measures, and large woody debris; (2) determine if landscape change over time contributed significantly to explaining present stream conditions; and (3) assess the importance of spatial scale in examining landuse influences on streams. Stream variables were related to both landuse and landscape geomorphology. Forest cover accounted for the most variation in nearly all models, supporting predictions of nutrient enrichment, thermal pollution, and sedimentation caused by landscape disturbance. Legacy effects from past catchment disturbance were apparent in sedimentation measures. Nitrogen and phosphorus concentrations, as well as stream temperature, were lower where riparian buffers had reforested. Models of stream physicochemistry fit better when predictors were catchment wide rather than more localized (i.e., within 2 km of a site). Cumulative impacts to streams due to changes in landuse must be managed from a watershed perspective with quantitative models that integrate across scales. 相似文献
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Keith V. Slack Rodger F. Ferreira Robert C Averett 《Journal of the American Water Resources Association》1986,22(2):237-248
ABSTRACT: Four different bottom-placed artificial substrates were compared with the Ponar grab for collecting benthic invertebrates. Artificial substrate samples of organisms were larger and more diverse than those of the grab. Barbeque Basket samplers caught the most taxa and individuals and Beak Trays caught the least. Chironomids and crustaceans were dominant in artificial substrate samples. Exposure habitat (left or right bank) determined taxa availability, whereas sampler design determined suitability for colonization by the taxa. Diversity for Beak Tray samples was lower than that for other artificial substrates but higher than for Ponar samples. The Barbeque Basket, Bull Basket, and Multiple Plate samples were taxonomically similar. Ponar samples were different, and Beak Trays were of intermediate similarity. As qualitative samplers, Barbeque Baskets were 63 percent efficient, followed by Bull Baskets (55 percent), Multiple Plates (48 percent), Beak Trays (38 percent), and Ponar Grabs (6–10 percent). Bull Baskets required the least and Beak Trays the most replicates to be within a preselected percentage error of the mean at the 95 percent probability level for numbers of taxa and individuals, and for diversity. Under conditions of the study, Bull Baskets ranked highest, followed by Barbeque Baskets and Multiple Plates, in selected performance criteria. Differences between grab and artificial substrate samples are explainable in terms of major riverine habitats and characteristics of the collection methods. 相似文献
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美国海岸带管理和环境评估的框架及启示 总被引:2,自引:0,他引:2
本文介绍了美国《海岸带管理法案》所反映的海岸带管理的基本问题,包括海岸带管理的目标、重点领域、方法、策略与政策框架;还介绍了美国的海岸带区划,以及海岸环境评估的指标体系和评估标准。在此基础上提出所受启示与借鉴之处。 相似文献
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介绍了美国大气固定源排放标准的体系、标准内容、标准制定程序与标准实施的有关规定。并分析了其特点。 相似文献
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国内外农药生态风险评价研究综述 总被引:4,自引:1,他引:3
从生态风险评价的准则、评价方法、风险评价模型及生态风险评价在农药登记管理中的重要作用等方面对比,阐述了美国、世界经济合作与发展组织(OECD)及我国农药生态风险评价的研究概况。指出了我国在农药生态风险评价方面存在的不足,并针对这些不足之处提出了对策建议。 相似文献
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Ronald J. Willey Daniel A. Crowl Wil Lepkowski 《Journal of Loss Prevention in the Process Industries》2005,18(4-6):365-374
The chemical accident at 12:45 AM on December 3, 1984 in Bhopal India had a profound effect on the practice of chemical process safety in the United States. Fearing the possibility of similar events occurring in the United States, the United States Congress convened several hearings and investigations into the causes of the disaster. The inquiries focused both on the state of process safety within the US chemical industry and on the readiness of communities located near chemical operations to respond to sudden and dangerous toxic discharges. Of equal significance were concerns over the safety of workers in chemical plants. This paper reviews the major legislative, academic, and industrial changes initiated in the area of process safety after the event, their influence on saving lives, and on improving living conditions surrounding chemical complexes in the United States. 相似文献