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11.
本文从土地资源禀赋、土地利用效益、土地保护水平三个方面,初步建立了生态城市建设土地利用评价指标体系,并以扬州市为研究案例,得出扬州市2000~2008年的土地利用与保护综合水平。研究结果表明:2000年,扬州市土地利用与保护综合评价分值为52.9,处于生态恢复阶段中的治理小于破坏阶段;自2000~2008年扬州市土地利用与保护综合水平随时间呈递增趋势,特别是2004年以来递增速度明显加快,到2008年扬州市土地利用与保护综合分值为74.7,处于生态恢复阶段的末期,即将跨入生态保育阶段。最后,根据评价结论,提出了今后一段时期扬州生态城市建设土地利用与保护的建议。 相似文献
12.
Transition from platemargin to intraplate environment: Geochemistry of basalts in Paleogene Liaohe basin,northeastern China 总被引:3,自引:0,他引:3
WU Changzhi GU Lianxing REN Zuowei ZHANG Zunzhong CHEN Zhenyan & ZHAO Ming . State Key Laboratory of Mineral Deposit Research 《中国科学D辑(英文版)》2005,48(12):2069-2080
Mesozoic and Cenozoic volcanic rocks are widely distributed in the circum-Pacific area of eastern China. These rocks have long been genetically linked to westward subduction of the paleo-Pacific oceanic plate to the eastern Asia continent[1,2]. Research in re-cent years[3―6] has attained conclusions that a simple paleo-Pacific subduction model does not work well in interpreting all the volcanic rocks in eastern China, although some of them could be attributed to circum-Pacific interaction … 相似文献
13.
Effects of an ecological conservation and restoration project in the Three-River Source Region,China 总被引:3,自引:3,他引:3
The first-stage of an ecological conservation and restoration project in the Three-River Source Region (TRSR), China, has been in progress for eight years. However, because the ecological effects of this project remain unknown, decision making for future project implementation is hindered. Thus, in this study, we developed an index system to evaluate the effects of the ecological restoration project, by integrating field observations, remote sensing, and process-based models. Effects were assessed using trend analyses of ecosystem structures and services. Results showed positive trends in the TRSR since the beginning of the project, but not yet a return to the optima of the 1970s. Specifically, while continued degradation in grassland has been initially contained, results are still far from the desired objective, ‘grassland coverage increasing by an average of 20%–40%’. In contrast, wetlands and water bodies have generally been restored, while the water conservation and water supply capacity of watersheds have increased. Indeed, the volume of water conservation achieved in the project meets the objective of a 1.32 billion m3 increase. The effects of ecological restoration inside project regions was more significant than outside, and, in addition to climate change projects, we concluded that the implementation of ecological conservation and restoration projects has substantially contributed to vegetation restoration. Nevertheless, the degradation of grasslands has not been fundamentally reversed, and to date the project has not prevented increasing soil erosion. In sum, the effects and challenges of this first-stage project highlight the necessity of continuous and long-term ecosystem conservation efforts in this region. 相似文献
14.
The Velenje area (almost 200 km2 with over 31,000 inhabitants) is based on the Šalek Valley, which became a leading area of industrialisation and urbanisation
after the Second World War, with consequent pollution problems. Various industrial plants polluted the river Paka while more
serious hazards arose through the coal mine which is a still causing landscape subsidence and the thermal power station in
the neighbourhood of Šoštanj which is a major source of sulphur dioxide and nitrogen oxide pollution. In 1987 there was an
ecological protest which marked the beginning of a sustainable development strategy for the community. During the past decade
programmes have dealt with the degradation of air, soil and water to achieve cleaner air, a transformation in landuse and
enhancement the river's formerly weak self-purifying capabilities. This article examines the changes in the valley since the
attention of the authorities was drawn to the deterioration of living conditions. Despite the pressures of transition which
have seen unemployment rising to over ten percent, significant environmental improvements have been made and the area stands
as a model for the rest of the country.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
悬浮液进样—石墨炉原子吸收测定钒钛磁铁矿中痕量镓 总被引:5,自引:0,他引:5
研究了悬浮液进样_石墨炉原子吸收测定钒钛磁铁矿中痕量镓的分析方法。以Ni(Ⅱ)作为基体改进剂时,可直接用镓标准溶液进行校准。样品粒度<38μm、悬浮液中试样质量浓度在01~80g/L、含镓质量浓度不超过100μg/L时呈良好线性关系,检出限为24μg/L镓。用所拟方法测定了含镓量在16~42μg/g的标准矿样,结果与标准值相符,6次平行测定的相对标准偏差不超过9%,满足痕量分析的要求。 相似文献
16.
从洋壳俯冲到陆壳俯冲和碰撞:来自羌塘中西部地区榴辉岩和蓝片岩地球化学的证据 总被引:3,自引:2,他引:3
羌塘中部晚三叠世低温/高压变质带是目前青藏高原内部延伸规模最大的高压变质带,但大量关键高压变质岩石出露地区地球化学资料匮乏,严重制约了对高压变质带原岩建造以及构造演化的全面认识。本文以羌塘中西部地区尚无地球化学资料的果干加年山榴辉岩和红脊山蓝片岩为研究对象,进行了系统的地球化学以及原岩恢复工作。研究表明,果干加年山榴辉岩呈透镜状产于围岩石榴石多硅白云母片岩和少量大理岩中,其原岩为亚碱性玄武岩,具有较低的稀土总量(∑REE=51.19×10-6~59.43×10-6)和轻稀土亏损的特征[(La/Yb)N=0.59~0.70],不具有Nb、Ta、Ti的亏损,与典型的N-MORB特征一致,暗示其原岩可能来源于亏损的地幔源区,形成于洋中脊环境。红脊山地区基性蓝片岩的原岩为碱性玄武岩-亚碱性玄武岩,具有高的TiO2(2.97%~4.14%)和P2O5(0.29%~0.48%)含量,富集轻稀土元素[(La/Yb)N=6.10~11.6]和高场强元素,地球化学特征类似于OIB。但是这些基性蓝片岩与大量的陆源碎屑岩伴生产出,且具有明显的硅铝质上地壳物质混染的特征,与南羌塘地区二叠纪大陆板内基性岩墙的产出特征以及地壳混染特征一致,可能是其俯冲消减的产物。通过本文研究结果并结合区域内已识别出的E-MORB型洋壳和洋岛/海山物质深俯冲的证据,我们认为羌塘中部晚三叠世高压变质带以洋壳物质深俯冲为主,同时亦保留了部分陆壳物质俯冲的证据,暗示大洋向北俯冲消减结束之后,又牵引至少一部分南羌塘北缘陆壳物质经历了随后的俯冲过程。 相似文献
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Marine algae contain various bromophenols with a variety of biological activities,including antimicrobial,anticancer,and anti-diabetic effects.Here,we briefly review the recent progress in researches on the biomaterials from marine algae,emphasizing the relationship between the structure and the potential anti-diabetic applications.Bromophenols from marine algae display their hyperglycemic effects by inhibiting the activities of protein tyrosine phosphatase 1B,α-glucosidase,as well as other mechanisms. 相似文献
20.
Fluid permeability in fractured rocks is sensitive to pore-pressure changes. This dependence can have large effects on the flow of fluids through rocks. We define the permeability compliance γ= 1/k(k/δpp)pc, which is the sensitivity of the permeability k to the pore pressure pp at a constant confining pressure pc, and solve the specific problems of constant pressure at the boundary of a half-space, a cylindrical cavity and a spherical cavity. The results show that when the magnitude of permeability compliance is large relative to other compliances, diffusion is masked by a piston-like pressure profile. We expect this phenomenon to occur in highly fractured and compliant rock systems where γ may be large. The pressure profile moves rapidly when fluids are pumped into the rock and very slowly when fluids are pumped out. Consequently, fluid pressure, its history and distribution around injection and production wells may be significantly different from pressures predicted by the linear diffusion equation. The propagation speed of the pressure profile, marked by the point where δpp/δx is a maximum, decreases with time approximately as and the amplitude of the profile also dissipates with time (or distance). The effect of permeability compliance can be important for fluid injection into and withdrawal from reservoirs. For example, excessive drawdown could cause near-wellbore flow suffocation. Also, estimates of the storage capacity of reservoirs may be greatly modified when γ is large. The large near-wellbore pressure gradients caused during withdrawal by large γ can cause sanding and wellbore collapse due to excessive production rates. 相似文献