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771.
Developing a spatial framework of common ecological regions for the conterminous United States 总被引:5,自引:1,他引:4
McMahon G Gregonis SM Waltman SW Omernik JM Thorson TD Freeouf JA Rorick AH Keys JE 《Environmental management》2001,28(3):293-316
In 1996, nine federal agencies with mandates to inventory and manage the nation's land, water, and biological resources signed
a memorandum of understanding entitled “Developing a Spatial Framework of Ecological Units of The United States.” This spatial
framework is the basis for interagency coordination and collaboration in the development of ecosystem management strategies.
One of the objectives in this memorandum is the development of a map of common ecological regions for the conterminous United
States. The regions defined in the spatial framework will be areas within which biotic, abiotic, terrestrial, and aquatic
capacities and potentials are similar. The agencies agreed to begin by exploring areas of agreement and disagreement in three
federal natural-resource spatial frameworks—Major Land Resource Areas of the US Department of Agriculture (USDA) Natural Resources
Conservation Service, National Hierarchy of Ecological Units of the USDA Forest Service, and Level III Ecoregions of the US
Environmental Protection Agency. The explicit intention is that the framework will foster an ecological understanding of the
landscape, rather than an understanding based on a single resource, single discipline, or single agency perspective. This
paper describes the origin, capabilities, and limitations of three major federal agency frameworks and suggests why a common
ecological framework is desirable. The scientific and programmatic benefits of common ecological regions are described, and
a proposed process for development of the common framework is presented. 相似文献
772.
社区参与旅游发展运行框架的初步研究 总被引:2,自引:0,他引:2
社区参与旅游发展是旅游可持续发展宏观系统中不可或缺的机制。提出了社区参与旅游的新目标观、新组织观、新系统观等理念,并尝试运用区域经济学的理论,对社区参与旅游发展运行框架进行了新的探讨,旨在为我国社区参与的有效实施和社区旅游的可持续发展提供借鉴。 相似文献
773.
用聚乙烯醇-海藻酸钠(PVA-SA)将金针菇(Flammulina velutipes)、毛木耳(Auricularia polytricha)、杏鲍菇(Pleurotus eryngii)和平菇(Pleurotus ostreatus)加工废弃物固定制成吸附小球,研究初始p H值、反应时间对Cu~(2+)吸附的影响及吸附特性,并应用到实际废水的处理中。结果表明:固定金针菇、毛木耳、杏鲍菇和平菇废弃物吸附小球的最大吸附率分别为81.3%、60.8%、42.8%和50.0%;伪二级动力学模型比颗粒内扩散模型能更好地描述固定食用菌加工废弃物吸附小球对Cu~(2+)的吸附过程;固定金针菇、毛木耳和平菇废弃物吸附小球的等温吸附过程与Langmuir等温模型拟合度高,吸附过程主要是单层吸附,固定杏鲍菇废弃物小球的等温吸附过程则更符合Freundlich等温模型;扫描电镜(SEM)分析显示,固定金针菇废弃物吸附小球吸附Cu~(2+)后,细胞壁增厚,细胞壁上形成了明显的Cu~(2+)无机沉淀或晶体,表现为物理性吸附。研究表明,固定金针菇废弃物吸附小球对自然废水中Cu~(2+)的去除率为73.11%,具有一定的实际应用价值。 相似文献
774.
775.
776.
主要研究了不同浓度的Cu^2+对螺旋藻生长的影响,结果表明:Cu^2+浓度为0.079mg/L时对螺旋藻的生长具有明显的促进作用,当浓度大于0.395mg/L时则对螺旋藻的生长产生抑制作用,而且抑制作用随着铜离子浓度的增加而增强;铜离子对螺旋藻的完全抑制质量浓度为39.50mg/L。 相似文献
777.
将壳聚糖、聚醚多元醇、甲苯二异氰酸酯混合发泡,制备了壳聚糖/聚氨酯(Cs/PU)多孔复合材料,利用原子吸收光谱研究了Cs/PU对水中Cu2+、Cd2+的吸附能力。结果表明:在28℃条件下,当吸附时间为30min,溶液pH=4~5时,Cu2+的最高去除率为96.67%,溶液pH=6~7时,Cd2+的去除率为95.67%。Cd2+、Cu2+的饱和吸附率容量分别为28.78mg/g和25.32mg/g。两种金属离子共存时,Cs/PU对Cu2+的选择性大于Cd2+。 相似文献
778.
A series of single-phase T-structured NdSrCu1??xCoxO4?? with oxygen vacancies and T0-structured Sm1:8Ce0:2Cu1??xCoxO4?? (x:
0–0.4) with oxygen excess were prepared using ultrasound-assisted citric acid complexing method, and characterized by means of
techniques such as thermogravimetric analysis and NO temperature-programmed desorption (NO-TPD). The catalytic activities of these
materials were evaluated for the decomposition of NO. It was found that the NdSrCu1??xCoxO4?? catalysts were of oxygen vacancies
whereas the Sm1:8Ce0:2Cu1??xCoxO4?? ones possessed excessive oxygen (i.e., over-stoichiometric oxygen); with a rise in Co doping level,
the oxygen vacancy density of NdSrCu1??xCoxO4?? decreased while the over-stoichiometric oxygen amount of Sm1:8Ce0:2Cu1??xCoxO4??
increased. The NO-TPD results revealed that NO could be activated much easier over the oxygen-deficient perovskite-like oxides
than over the oxygen-excessive perovskite-like oxides, with the NdSrCuO3:702 catalyst showing the best e ciency in activating NO
molecules. Under the conditions of 1.0% NO/helium, 2800 hr??1, and 600–900°C, the catalytic activity of NO decomposition followed
the order of NdSrCuO3:702 > NdSrCu0:8Co0:2O3:736 > NdSrCu0:6Co0:4O3:789 > Sm1:8Ce0:2Cu0:6Co0:4O4:187 > Sm1:8Ce0:2Cu0:8Co0:2O4:104
> Sm1:8Ce0:2CuO4:045, in concord with the sequence of decreasing oxygen vacancy or oxygen excess density. Based on the results,
we concluded that the higher oxygen vacancy density and the stronger Cu3+/Cu2+ redox ability of NdSrCu1??xCoxO4?? account for the
easier activation of NO and consequently improve the catalytic activity of NO decomposition over the catalysts. 相似文献
779.
Effects of free iron oxyhydrates (Fed) and soil organic matter (SOM) on copper (Cu2+) sorption-desorption behavior by size fractions of aggregates from two typical paddy soils (Ferric-Accumulic Stagnic Anthrosol (Soil H) and Gleyic Stagnic Anthrosol (Soil W)) were investigated with and without treatment of dithionite-citrate-bicarbonate and of H2O2. The size fractions of aggregates were obtained from the undisturbed bulk topsoil using a low energy ultrasonic dispersion procedure. Experiments of equilibrium sorption and subsequent desorption were conducted at soil water ratio of 1:20, 25℃. For Soil H, Cu2+ sorption capacity of the DCB-treated size fractions was decreased by 5.9% for fine sand fraction, by 40.4% for coarse sand fraction, in comparison to 2.9% for the bulk sample. However, Cu2+ sorption capacities of the H2O2-treated fractions were decreased by over 80% for the coarse sand fraction and by 15% for the clay-sized fraction in comparison to 88% for bulk soil. For Soil W, Cu2+ sorption capacity of the DCB-treated size fraction was decreased by 30% for the coarse sand fraction and by over 75% for silt sand fraction in comparison to 44.5% for the bulk sample. Cu2+ sorption capacities of the H2O2-treated fractions were decreased by only 2.0% for the coarse sand fraction and by 15% for the fine sand fraction in comparison to by 3.4% for bulk soil. However, Cu2+ desorption rates were increased much in H2O2-treated samples by over 80% except the clay-sized fraction (only 9.5%) for Soil H. While removal of SOM with H2O2 tendend to increase desorption rate, DCB- and H2O2-treatments caused decrease in Cu2+ retention capacity of size fractions. Particularly, there hardly remained Cu2+ retention capacity by size fractions from Soil H after H2O2 treatment except for clay-sized fraction. These findings supported again the dominance of the coarse sand fraction in sorption of metals and the preference of absorbed metals bound to SOM in differently stabilized status among the size fractions. Thus, enrichment and turnover of SOM in paddy soils may have great effects on metal retention and chemical mobility in paddy soils. 相似文献
780.