首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5篇
  完全免费   1篇
  评价与监测   6篇
  2016年   1篇
  2015年   1篇
  2005年   1篇
  2002年   1篇
  2001年   1篇
  1993年   1篇
排序方式: 共有6条查询结果,搜索用时 62 毫秒
1
1.
区域生态质量评价指标选择基础框架及其实现   总被引:9,自引:0,他引:9  
论述了区域生态质量评价的理论基础、基本单元、指标选择原则及方法、基本评价指标及其实现 ,旨在为区域生态质量评价指标框架的建立打下基础  相似文献
2.
Many studies are based on the assumption that an area and its surrounding (buffer) area present similar environmental conditions and can be compared. For example, in order to assess the effectiveness of a protected area, the land use/cover changes are compared inside the park with its surroundings. However, the heterogeneity in spatial variables can bias this assessment: we have shown that most of the protected areas in Mexico present significant environmental differences between their interior and their surroundings. Therefore, a comparison that aims at assessing the effectiveness of conservation strategies, must be cautioned. In this paper, a simple method which allows the generation of a buffer area that presents similar conditions with respect to a set of environmental variables is presented. The method was used in order to assess the effectiveness of the Calakmul Biosphere Reserve, a protected area located in the south-eastern part of Mexico. The annual rate of deforestation inside the protected area, the standard buffer area (based upon distance from the protected area only) and the similar buffer area (taking into account distance along with some environmental variables) were 0.3, 1.3 and 0.6%, respectively. These results showed that the protected area was effective in preventing land clearing, but that the comparison with the standard buffer area gave an over-optimistic vision of its effectiveness.  相似文献
3.
江苏省高宝湖区湖泊群富营养化特征分析   总被引:1,自引:0,他引:1       下载免费PDF全文
对江苏省高宝湖区高邮湖、宝应湖、邵伯湖和白马湖湖泊富营养化共性与差异性特征进行了分析。结果表明,2009—2014年,4个湖泊总体处于中营养—轻度富营养之间,综合富营养状态指数值在年内均呈波动变化,丰水期明显大于枯水期;主要营养因子水平在4个湖泊之间均存在较明显的差异,尤其是TN和SD 2项指标阶梯状差异较为明显,Chl-a也呈现不同程度的年内分布水平差异,并在春、夏季存在藻类暴发风险;各湖泊Chl-a与环境因子相关性差异较大,宝应湖、白马湖以及总体分析的高宝湖群Chl-a均与水温、TP相关性显著,TP应是高宝湖群藻类生长限制的主导营养因子;各湖泊富营养化特征存在差异性,总体上宝应湖与白马湖富营养化特征较为类似,与高邮湖差异较大,邵伯湖富营养化特征与高邮湖接近,又兼有与宝应湖、白马湖相似性特征。  相似文献
4.
The varying traffic parameters such as traffic volume, speed, shape and size, and terrain roughness conditions play a vital role on dispersion of pollutants in the near field of roadways. Simulation experiments were carried out in the Environmental Wind Tunnel (EWT) to evaluate the traffic induced effects on vertical dispersion parameter (σ z ) for heterogeneous traffic conditions in the near field of roadways for evaluating the effect of variations in traffic volume, terrain roughness condition and approaching wind direction. The model vehicle movement system was fabricated and made operational in the EWT, which allowed the variation in traffic volume, speed and wind road inclination. Sixty-six hydrocarbon tracer experiments were performed to evaluate σ z in the near field of roadways for variable traffic volume, three terrain roughness conditions and two approaching wind directions (i.e., 90° and 60°). The values of σ z for heterogeneous traffic conditions were found to be higher for low roughness conditions in comparison to other two higher roughness conditions for various traffic volumes and approaching wind directions. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献
5.
An investigation was carried out to select locations for long-term monitoring of inputs of contaminants into Lake Ontario using fine-grained bottom sediments as an historical record of pollution. The sediment sampling program was designed to determine sediment heterogeneity in the western, central and eastern depositional basins of the lake. Surficial sediments and sediment cores were collected in each basin to obtain information on horizontal distribution and concentration profiles of major and trace elements in the sediments (Si, Al, Ca, Mg, Fe, Na, K, Ti, Mn, P, As, Co, Cu, Cr, Ni, Pb and Zn). The results of the investigation indicated that fine-grained sediments in three Lake Ontario depositional basins are homogeneous to a high degree, and that only a few sediment cores need to be collected within each basin for the long-term monitoring of inputs of contaminants to the lake.  相似文献
6.
综述大气中有机胺可能的来源、健康危害及其在大气中的均相和非均相化学转化机制,阐述有机胺的反应产物对二次有机气溶胶及其对大气气溶胶的物理和化学性质的改变,此类改变增强大气气溶胶间接气候效应(如成云结核能力等)。大气中的有机胺主要通过与大气氧化剂的反应和非均相反应过程的溶解或置换进入颗粒相,而后随着湿沉降(如云滴、雾滴、雨滴等)到达地面或海面。  相似文献
1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号