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排序方式: 共有120条查询结果,搜索用时 15 毫秒
111.
论述了纤维球过滤技术用于给水处理和废水处理的效果和适应情况,并和砂滤进行了同步比较试验.同时,探讨了纤维球滤料的反冲洗条件和反冲效果,并经长期运行以观察纤维球过滤的稳定性. 相似文献
112.
Benjamin K. Jessup Philip R. Kaufmann Forrest John Lynette S. Guevara Seva Joseph 《Journal of the American Water Resources Association》2014,50(6):1558-1574
Excess fine sediments in streambeds are among the most pervasive causes of degradation in streams of the United States. Simple criteria for acceptable streambed fines are elusive because streambed fines and biotic tolerances vary widely in the absence of human disturbances. In response to the need for sediment benchmarks that are protective of minimum aquatic life uses under the Clean Water Act, we undertook a case study using surveys of sediment, physical habitat, and macroinvertebrates from New Mexico streams. Our approach uses weight of evidence to develop suggested benchmarks for protective levels of surficial bedded sediments <0.06 mm (silt and finer) and <2.0 mm (sand and finer). We grouped streams into three ecoregions that were expected to produce similar naturally occurring streambed textures and patterns of response to human disturbances. Within ecoregions, we employed stressor response models to estimate fine sediment percentages and bed stability that are tolerated by resident macroinvertebrates. We then compared individual stream sediment data with distributions among least‐disturbed reference sites to determine deviation from natural conditions, accounting for natural variability across ecoregion, gradient, and drainage area. This approach for developing benchmark values could be applied more widely to provide a solid basis for developing bedded sediment criteria and other protective management strategies in other regions. 相似文献
113.
环境影响评价制度和社会稳定风险评估制度作为预防和控制环境影响、创新社会风险管理的重要制度,实施以来发挥了重要作用,但也出现了工作边界和内容范围交叉的问题。尤其是近年来,环境污染焦虑引发社会风险事件的建设项目不断增多,导致两者的"天然联系"愈发紧密,工作存在模糊地带的问题愈发凸显,致使建设项目行政审批繁复、执行力差。在梳理环评、稳评的发展历程和存在问题的基础上,深入分析了环评和稳评的法律地位、适用范围、评价目标、评价内容、实施主体和程序上的异同,剖析了两者在制度设计和内容衔接方面的关系,并从理清工作边界职责、环境社会风险评估结果共享、强化稳评公众参与等方面提出了环评和稳评政策衔接的建议,为政府有效实施建设项目环境、社会监管提供决策参考。 相似文献
114.
飞机操纵系统是一个控制飞机飞行安全的关键系统。笔者介绍了飞机操纵系统的发展过程 ,重点讨论了为了提高飞行安全性及在保证飞行安全的前提下 ,提高飞机操纵性而对飞机操纵系统进行的改进、完善的方法 ,进而对操作系统的未来发展提出了看法。 相似文献
115.
It is well known that calcium arsenates may not be a good choice for arsenic removal and immobilization in hydrometallurgical practices. However, they are still produced at some plants in the world due to various reasons. Furthermore, calcium arsenates can also naturally precipitate under some specific environments. However, the transformation process of poorly crystalline calcium arsenates (PCCA) and the stability of these samples under atmospheric CO2 are not yet well understood. This work investigated the transformation process of PCCA produced by using different neutralization reagents (CaO vs. NaOH) with various Ca/As molar ratios at pH?7–12 in the presence of atmospheric CO2. After aging at room temperature for a period of time, for samples neutralized with NaOH and precipitated at pH?10 and 12, release of arsenic back into the liquid phase occurred. In contrast, for the samples precipitated at pH?8, the aqueous concentration of arsenic was observed to decrease. XRD, Raman, and SEM results suggested that the formation of various types of crystalline calcium carbonates and/or calcium arsenates controls the arsenic behavior. Moreover, the application of lime may enhance the stability of the generated PCCA. However, no matter what neutralization reagent is used, the stability of the generated PCCA is still of concern. 相似文献
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Raquel Barrena Xavier Font Xavier Gabarrell Antoni Sánchez 《Waste management (New York, N.Y.)》2014,34(7):1109-1116
Stability is one of the most important properties of compost obtained from the organic fraction of municipal solid wastes. This property is essential for the application of compost to land to avoid further field degradation and emissions of odors, among others. In this study, a massive characterization of compost samples from both home producers and industrial facilities is presented. Results are analyzed in terms of chemical and respiration characterizations, the latter representing the stability of the compost. Results are also analyzed in terms of statistical validation. The main conclusion from this work is that home composting, when properly conducted, can achieve excellent levels of stability, whereas industrial compost produced in the studied facilities can also present a high stability, although an important dispersion is found in these composts. The study also highlights the importance of respiration techniques to have a reliable characterization of compost quality, while the chemical characterization does not provide enough information to have a complete picture of a compost sample. 相似文献
120.
Intraguild predation constitutes a widespread interaction occurring across different taxa, trophic positions and ecosystems, and its endogenous dynamical properties have been shown to affect the abundance and persistence of the involved populations as well as those connected with them within food webs. Although optimal foraging decisions displayed by predators are known to exert a stabilizing influence on the dynamics of intraguild predation systems, few is known about the corresponding influence of adaptive prey decisions in spite of its commonness in nature. In this study, we analyze the effect that adaptive antipredator behavior exerts on the stability and persistence of the populations involved in intraguild predation systems. Our results indicate that adaptive prey behavior in the form of inducible defenses act as a stabilizing mechanism and show that, in the same direction that adaptive foraging, enhances the parameter space in which species can coexist through promoting persistence of the IG-prey. At high levels of enrichment, the intraguild predation system exhibits unstable dynamics and zones of multiples attractors. In addition, we show that the equilibrium density of the IG-predator could be increased at intermediate values of defense effectiveness. Finally we conclude that adaptive prey behavior is an important mechanism leading to species coexistence in intraguild predation systems and consequently enhancing stability of food webs. 相似文献