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301.
Assessing Ecological Integrity of Ozark Rivers to Determine Suitability for Protective Status 总被引:3,自引:0,他引:3
Preservation of extraordinary natural resources, protection of water quality, and restoration of impaired waters require a strategy to identify and protect least-disturbed streams and rivers. We applied two objective, quantitative methods to determine stream ecological integrity of headwater reaches of 10 Ozark rivers, 5 with Wild and Scenic River federal protective status. Thirty-four variables representing macroinvertebrate and fish assemblage characteristics, in-stream habitat, riparian vegetation, water quality, and watershed attributes were quantified for each river and analyzed using two multivariate approaches. The first approach, cluster and discriminant analyses, identified two groups of river with only one variable (% forested watershed) reliably distinguishing groups. Our second approach employed ordinal scaling to compare variables for each river to conceptually ideal conditions that were developed as a composite of optimal attributes among the 10 rivers. The composite distance of each river from ideal was then calculated using a unidimensional ranking technique. Two rivers without Wild and Scenic River designation ranked highest relative to ideal (highest ecological integrity), and two others, also without designation, ranked most distant from ideal (lowest ecological integrity). Fish density, number of intolerant fish species, and invertebrate density were influential biotic variables for scaling. Contributing physical variables included riparian forest cover, water nitrate concentration, water turbidity, percentage of forested watershed, percentage of private land ownership, and road density. These methods provide a framework for refinement and application in other regions to facilitate the process of establishing least-disturbed reference conditions and identifying rivers for protection and restoration. 相似文献
302.
Xin-Rui Li Hiroshi Koseki 《Journal of Loss Prevention in the Process Industries》2005,18(4-6):455-459
In this paper, compared with a UN cylindrical 500 mL Dewar (H.4 in the UN tests), a spherical 1 L Dewar vessel was used to study the early stages of runaway reactions of several liquid and solid samples, including three organic peroxides and a reactive material. The samples were filled in the vessels and the temperature profiles versus times at different positions of the samples were measured. As a result, the minimum temperatures, defined as the SADT, were averagely 10 K lower than those measured in the cylindrical Dewar vessels. At the same time, the temperature profiles of solids in the spherical Dewars tended to be homogeneous. The heat transfer coefficient of a spherical Dewar is only 0.18 W/K/m, one-eighth of a conventional cylindrical Dewar vessel. Meanwhile it has a low phi factor. These factors are essential to simulate low heat loss bulk conditions in the equilibrium process and at the early stage of a runaway reaction. To characterize the ability of the adiabaticity of a storage vessel, it can be seen that a spherical Dewar could simulate the plant process having critical storage size of a reactive-material, r0, approximately 0.6 m. It is recommended that such a technique is used to investigate the SADT of an unstable material in larger scale packaging or a material with very weak heat release in industry. 相似文献
303.
Füreder L. Vacha C. Amprosi K. Bühler S. Hansen C. M. E. Moritz C. 《Water, Air, & Soil Pollution: Focus》2002,2(2):275-294
Natural and near-natural streams are rare in the densely populated areas of the Alps. A variety of anthropogenic impacts have resulted in the alteration and sometimes even complete destruction of these systems. Nowadays it is difficult to find un-impacted streams that are strongly needed to define the natural variability and ecosystem processes. The results from freshwater inventories and habitat assessments conducted in protected areas in Austria (Nationalpark Hohe Tauern) and Italy (Naturpark Rieserferner-Ahrn) were used to develop a comprehensive typology of Alpine streams. Three different levels were used to discriminate between the distinct stream/river types: source (glacial vs. non-glacial), hierarchy (i.e. location within the stream system) and topography/ channel morphology. Important characters defining the structure and function of these stream types are gradient, substrate composition, flow pattern and riparian vegetation. Benthic fauna assemblages from 99 near-natural stream segments in glacial and non-glacial systems demonstrated the effect of glaciation on abundance levels of the total macroinvertebrate fauna, EPT taxa (Ephemeroptera, Plecoptera and Trichoptera) and the chironomid subfamily Diamesinae in different altitudes. A general decrease of abundances with increasing altitude was found. While stream segments with a degree of glaciation >10% primarily showed reduced abundances at all altitudes, lower (<10%) or no glaciation did not influence invertebrate abundances at lower reaches. Due to the near-natural conditions of the selected stream segments, a valuable definition of reference conditions of Alpine streams based on habitat characteristics is available. As a basis it offers excellent opportunities to conduct holistic interdisciplinary studies in protected areas in the future. 相似文献
304.
305.
Optimization of the electrocoagulation process for the removal of copper, lead and cadmium in natural waters and simulated wastewater 总被引:3,自引:0,他引:3
Chemical, electrochemical and flow variables were optimized to examine the effectiveness of the electrocoagulation process for the removal of copper, lead and cadmium. The electrochemical process, which uses electrodes of commercial laminate steel, was applied to simulated wastewater containing 12 mg dm(-3) of copper, 4 mg dm(-3) of lead and 4 mg dm(-3) of cadmium. The optimum conditions for the process were identified as pH=7, flow rate=6.3 cm(3) min(-1) and a current density between 31 and 54 A m(-2). When the electrode geometric area and time of electrolysis reached critical values, the copper removal reached a maximum value of 80%. A linear relationship was identified between the current density and the mass of generated sludge. In addition, a linear relationship was found between specific energy consumption and current density. The results of this investigation provide important data for the development of an industrial-scale electrolytic reactor. 相似文献
306.
pH对剩余污泥厌氧发酵产生的COD、磷及氨氮的影响 总被引:26,自引:2,他引:24
城市污水处理厂产生的污泥按照来源的不同可以分为初沉污泥和剩余污泥,通过采用控制pH值的方法,在20~22℃条件下,研究了剩余污泥在不同pH条件下厌氧发酵的情况.结果表明:将剩余污泥的pH值控制为8.0~10.0,在20d的厌氧发酵时间内,溶出的COD(SCOD)要大于pH为5.0~7.0,特别是pH=10.0和pH=11.0时的SCOD值是pH=6.0时的10倍左右,并且第8d产生的挥发性脂肪酸(VFA)也为碱性条件大于酸性条件;但酸性条件下溶出的磷及氨氮大于碱性条件. 相似文献
307.
Introduction D istillery w astew ater m ainly includes spent w ash, w hich is one of the m ost com plex, troublesom e industrial organic effluents. This kind of w astew ater has previously been treated aerobically after dilution w ith other w ash w aters.… 相似文献
308.
常亮 《铁路节能环保与安全卫生》2021,(1):13-17
随着城市的发展,轨道交通在各大城市中得到迅速发展,但与之相伴的环境振动问题也日益突显.为研究城市轨道交通地下线列车运行速度、线路条件、减振措施等运营条件对环境振动影响,在某地铁线路隧道内进行了环境振动源强测试.结果表明,隧道壁源强位置处Z振级随着速度的增加而增大,列车通过速度在57~75 km/h变化时,列车速度每增加... 相似文献
309.
310.
为了研究海底油气管道多个裂纹间相互作用对管道产生的影响,针对海底悬跨管道表面双裂纹的相互作用,采用有限元方法建立双环向表面裂纹模型,采用围道积分法求解双裂纹下的应力强度因子,研究了不同边界条件下,不同尺寸裂纹间的相互影响规律,并对比了单裂纹下应力强度因子的变化情况。研究结果表明:不同尺寸的裂纹对双裂纹的相互影响规律有一定影响,且双裂纹应力强度因子最大值均出现在裂纹最深点处;弹簧边界下双裂纹相互影响规律与简单边界下相互影响规律明显不同;不同边界条件对悬跨管道双裂纹应力强度因子的影响较大。研究结果可为海底悬跨管道的失效分析提供参考依据。 相似文献