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291.
随着社会经济的快速发展,城市河道水体污染日益严峻,已经破坏了现有水体生态环境的平衡。因此,对河道黑臭水体进行污染治理,已经成为了当前现代文明城市建设的一项重要的工作内容。本文通过分析黑臭水体的现状以及形成原因,提出了对应的黑臭水体污染治理技术,以更好地维护生态环境。 相似文献
292.
293.
Selective Patronage and Social Justice: Local Food Consumer Campaigns in Historical Context 总被引:1,自引:1,他引:0
C. Clare Hinrichs Patricia Allen 《Journal of Agricultural and Environmental Ethics》2008,21(4):329-352
In the early 2000s, the development of local food systems in advanced industrial countries has expanded beyond creation and
support of farmers’ markets and community supported agriculture farms and projects to include targeted Buy Local Food campaigns.
Non-governmental groups in many U.S. places and regions have launched such campaigns with the intent of motivating and directing
consumers toward more local food purchasing in general. This article examines the current manifestations and possibilities
for social justice concerns in Buy Local Food campaigns, by considering them within the more general category of “selective
patronage“ campaigns. Historical campaign examples, such as Buy Union, Buy American, and Buy Black campaigns, offer instructive
comparisons to contemporary consumer campaigns promoting local food. Through examining the construction of threats, intended
beneficiaries, products to be avoided, and those to be preferentially selected, the paper demonstrates how selective patronage
campaigns have emphasized social justice needs and concerns for designated groups in ways that have been potentially exclusionary
of other disadvantaged groups and thus undermining of social justice more broadly. As a contemporary instance of “selective
patronage,“ Buy Local Food campaigns exhibit similar contradictory impulses, which are intensified by the conceptual and practical
pitfalls in designating “local.“ The article concludes by considering how the challenges and prospects for commitments to
social justice in local food consumer campaigns reinforce the importance of emerging initiatives centered on domestic fair
trade. 相似文献
294.
295.
油页岩地下开采巷道围岩的流变特性及工程应用 总被引:1,自引:0,他引:1
为研究油页岩巷道围岩的流变特性,采用岩土SJ-1B三轴蠕变仪对油页岩进行了三轴蠕变试验。根据试验结果,建立了油页岩非线性蠕变方程。根据上述非线性蠕变方程,以吉林桦甸油页岩矿一井运输大巷为工程背景,分析了围岩的应力场和位移场,并对不同支护强度和应力状态下的蠕变变形进行了系统的分析。研究结果表明,油页岩蠕变具有非线性,控制油页岩巷道围岩过量变形的根本途径是改变围岩的应力状态,以及适当提高锚杆、锚索的初始预应力。本文为有效控制油页岩开采时巷道围岩的有害变形提供了理论依据。 相似文献
296.
297.
Yang L Xiaoye Z Sunling G Huizheng C Dan W Wenjun Q Junying S 《Environmental monitoring and assessment》2006,120(1-3):301-312
The concentrations of EC, BC and dust aerosols were determined for atmospheric samples collected from an observation station in Xi'an, China. The results show that the averaged correlation coefficient between EC and BC was founded to be 0.72 with 0.81 (n = 49) in autumn, 0.70 (n = 112) in winter and 0.69 (n = 57) in spring, respectively. Absorption coefficients of dust aerosol were estimated to be 2.7 m2 g−1 in autumn and 4.4 m2 g−1 in winter. The comparison of absorption coefficients of dust aerosol with those of BC implies that BC is the principal light-absorbing aerosol over Xi'an atmosphere. By combining thermal analysis of elemental carbon and dust contents in the aerosol samples, however, the fraction of dust absorption to total light absorption is estimated to be 19% in autumn and 31% in winter, respectively. 相似文献
298.
This study provides timber growers with silvicultural guidelines for establishing and maintaining nest-tree habitat for native black sparrowhawks (Accipiter melanoleucus) in commercial planted forests in South Africa. In this country, exotic eucalypts and pines are planted principally for pulpwood and sawlog production. Nineteen nests were sampled in indigenous forests and 58 nests in exotic forests. Although mean nest heights differed between indigenous and exotic trees, in all trees, nests were positioned, on average, at 64% of tree height. Black sparrowhawks nested near stand edges, probably seeking a compromise between nesting adjacent to open hunting habitat and selecting an insulated tree from within the forest. Black sparrowhawks nested in tall trees ( X- = 18-33 m for different tree species classes) with a large diameter (>60 cm). Unfortunately, the South African pulpwood and sawlog industry employ short rotations (<16 years) and high tree densities (>700 trees/ha) that do not allow the trees to attain the characteristics suitable for black sparrowhawk nesting sites. Eucalypt and pine nest stands must be of 25 x 25 m minimum size and incorporate 10 trees at minimum heights of 21 and 18 m and diameters of 37 and 35 cm, respectively. If such nest-tree stands are set aside as islands in a sea of commercial forests, and black sparrowhawks and other forest raptors nest in them, timber growers will improve the tree-nesting raptor diversity of planted forests. If, however, these raptors prey upon species of conservation importance, the management recommendations could be reversed to limit the potential for predation. 相似文献
299.
Don C. Erman 《Environmental management》1981,5(6):531-536
General surveys of the benthic macroinvertebrates from Piceance Creek and the White River were conducted for nearly a decade prior to oil-shale exploitation in north central Colorado, USA. Comparison of the taxa collected in four studies on Piceance Creek and five studies on the White River shows little similarity among most studies. Studies were generally consistent in methods, site selection, and time of year for collection. Lack of agreement among the studies on what constitutes a baseline of common taxa is probably a result of taxonomic difficulties and differences in technique. More emphasis should be placed on testing possible impacts than on repeated, expensive, and inconclusive baseline inventories. 相似文献
300.
The distribution of fly ash that is discharged in the form of slurry from a power plant situated on the southern coast of the Black Sea was simulated with a transport model that used the velocity fields produced by isopycnic modelling. It is shown that a significant amount of ash is deposited in the vicinity of the discharge location. The ash remaining in the water column settles in a manner dependent on the direction and intensity of the local current regime. Generally, summer and spring are found to be seasons when the circulation is weak and the ash dispersion is confined to the shore. The model results are conditional upon obtaining observational data for validation. 相似文献