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Bruce W.MELVILLE 《国际泥沙研究》2002,17(4)
The authors present new measurements of maximum (equilibrium) local scour depth at bridge abutments, the new data being analysed in terms of the multiplying factors given in Melville (1992,1997) and Melville and Coleman (2000). The design method presented in these publications is referred to here as the University of Auckland (UoA) Method. The authors' data apply to the following factors:∏f (flow intensity), ∏θ (abutment alignment) and ∏g (approach channel geometry). 相似文献
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2.2) Lake Caviahue, Patagonia, ArgentinaDuring the warm seasons of 1998–2004, the naturally-acidic (pH2.2) Lake Caviahue was sampled for conductivity, temperature, oxygen, light, nutrients, and phytoplankton (density, biomass and chlorophyll a) with a view to studying the summer phytoplankton population changes with relation to environmental factors, as well as the significance of nitrogen limitation on the phytoplankton yield. Lake Caviahue is characterized by its low transparency, CO2, and N concentration; significant P values; a distinctive vertical distribution of phytoplankton biomass with high values along the water column; and sometimes maximum meta-hypolimnion values. Biodiversity is very low as a result of extreme environmental conditions, Chlorophyceae being the prevailing algae group. Two types of bioassays were carried out to assess nitrogen limitation. For the first bioassay, a solution of ammonium–nitrogen chloride and/or wastewater (rich in ammonium and phosphorus) was used, while one of the lake's sediments was the source of nutrients for the second bioassay. Contrary to the case of acidic mining lakes, N-ammonium proved to be a significant supportive capacity limiting factor as to phytoplankton yield. The present paper provides for the first time information on phytoplankton nitrogen limitation in a naturally-acidic lake. 相似文献
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