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831.
832.
正镶白旗火山杂岩为一不规则的穹丘状地质体,它是由渐变过渡的火山碎屑岩、流纹质碎斑熔岩和次火山岩构成的一个整体.可初步划分出三个近似同心环带.中环的流纹质碎斑熔岩是火山杂岩的主体,它的众多特征反映出初始岩浆含有较多的挥发分.岩浆在地下经过了较好的结晶分异,在地下——地上某个范围内存在隐爆——侵出区.火山作用是以小规模隐爆伴随缓慢的向上侵出为主.作用时间长,形成了规模较大的火山岩.正镶白旗火山杂岩属太平洋岩系钙碱质系列,原始岩浆由来源于上地幔和下地壳熔体的混熔作用形成. 相似文献
833.
D.H.?WardropEmail author J.A.?Bishop M.?Easterling K.?Hychka W.?Myers G.P.?Patil Charles?Taillie 《Environmental and Ecological Statistics》2005,12(2):209-223
The Atlantic Slope Consortium (ASC) is a project designed to develop and test a set of indicators in coastal systems that are ecologically appropriate, economically reasonable, and relevant to society. The suite of indicators will produce integrated assessments of the condition, health and sustainability of aquatic ecosystems based on ecological and socioeconomic information compiled at the scale of estuarine segments and small watersheds. The research mandate of the ASC project is the following:
Using a universe of watersheds, covering a range of social choices, we ask two questions:
As a basis for compiling ecological indicators, a watershed classification system was required for the experimental design. The goal was to develop approximately five categories of watersheds for each physiographic province, utilizing landscape and land use parameters that would be predictive of aquatic resource condition. All 14-digit Hydrologic Unit Code (HUC) watersheds in the Mid-Atlantic region would then be classified according to the regime. Five parameters were utilized for the classification: three land cover categories, consisting of forested, agricultural, and urban, median slope or median elevation, and total variance of land covers in 1-km-radius circles positioned on all stream convergence points in a specified 14-digit?HUC watershed. Cluster analysis utilizing these five parameters resulted in approximately five well-defined watershed classes per physiographic province. The distribution of all watersheds in the Mid-Atlantic region across these categories provides a unique report on the probable condition of watersheds in the region. 相似文献
- ? How “good” can the environment be, given those social choices?
- ? What is the intellectual model of condition within those choices, i.e., what are the causes of condition and what are the steps for improvement?
834.
介绍了原子吸收光谱仪的5种主要的背景校正技术(邻近谱线技术,连续光源法,塞曼法,自吸法及连续光源单色器波长调节法CEWM)及其主要产品,分析评述了各种校正技术的原理,特点及其应用状况。 相似文献
835.
A study has been made of the relationships between the characteristics of the riparian vegetation (floristic composition,
structure and diversity) and the spatial–temporal variation of the quality of the stream waters in a basin under a semiarid
Mediterranean climate in the southeastern Iberian Peninsula. The plant communities of the high reaches present greater specific
richness and diversity (S
mean= 7.0 ± 3.4 and H′mean= 2.0 ± 0.7) than do those of the middle and low reaches (S
mean= 4.5 ± 1.6 and H′mean= 1.8 ± 0.6). One zone reached the highest specific richness (S= 12, H′= 3.2), which, apart from being situated in the intermediate stretch of the basin, represents a transitional state (ecotone)
between the Salix and Tamarix communities. The characteristics of the waters analyzed indicate very high rates of erosion and runoff due to the nature
of the soils (easily eroded marls) and to agricultural expansion and mining since the 16th century. The present-day riparian
vegetation is not adequate to absorb the nitrates added to the basin by crop fertilization, reaching extremely high values,
particularly during the dry period (between 1.2 and 42.5 mg/liter). Sewage dumping at three sampling stations did not appear
to affect the specific composition of the woody vegetation. In the zones with watercourses, water salinity was low during
the period of greater water flow, but considerably higher in the dry season (the upper limit was some 1.2 mS/m), resulting
in a predominance of salt cedars over willows. Three types of saltcedar areas were distinguished: subhalophilous, which barely
changes its chemical composition over the season; halophilous, which develops over strongly mineralized waters and markedly
alters in chemical composition during the dry season; and hyperhalophilous, where salinity is extraordinarily high and quite
constant throughout the year. A direct relationship was found between the dominance of Tamarix africana and abundance of NaCl. 相似文献
836.
Modeling of air pollutant dispersion has been undertaken for emissions of sulfur dioxide (SO2) at the Mina Al-Fahal refinery in the Sultanate of Oman. The study was conducted during the period of November 1999 to October
2000. The Industrial Source Complex Short-Term (ISCST32) air pollution model was adopted to predict the ground level concentration
of SO2 in and around the refinery. The modeling results were validated against measured data during the study period. The comparison,
based on the monthly average measurements, showed that the model underestimates the observed SO2 concentrations. However, the predicted ground level concentrations of SO2 during the months of September, October, November, and June were in better agreement with the observations. The predicted
SO2 values are presented in the form of concentration contours to determine the spatial distribution of SO2 and to assess the impact on air quality over the survey area. Predicted SO2 concentrations were found lower than the World Health Organisation (WHO) guideline value of 365 μg/m3, with the maximum ground level concentrations being found to occur relatively close to the sources of emission. Moreover,
concentration contour patterns for the modeled area vary with changes in meteorological conditions. On the basis of this study,
the refinery is not likely to cause any significant deterioration in air quality, and predicted concentrations of SO2 are well below those likely to influence health. 相似文献
837.
本文采用邻苯三酚自氧化法,测定了大亚湾核电站Ⅰ、Ⅱ号机组运转前与后第1年、第2年附近地区动物体肝组织及红细胞中超氧物歧化酶(EC1.15.1.1Superoxidedismutase,SOD)活性变化,结果发现Ⅰ、Ⅱ号机组运转后第1年与第2年,鱼类,细鳞(TheraponJarbua)红细胞与肝组织中SOD活性较运转前明显升高(P<0.05),血红蛋白略有下降,肝组织蛋白无明显变化,两栖类动物蟾蜍(Bufomelanostictus)红细胞SOD活性运转后亦明显升高(P<0.01),但肝组织中SOD活性呈现下降(P<0.05),血红蛋白及肝组织蛋白无明显性变化,本文对其变化可能原因进行了讨论。 相似文献
838.
/ The Council on Environmental Quality's (CEQ's) principal aims in implementing the National Environmental Policy Act (NEPA) are (1) to reduce paperwork, (2) to avoid delay, and most importantly (3) to produce better decisions that protect, restore, and enhance the environment. This paper presents four strategies for improving the NEPA process along with tools that can be used to implement each strategy. The tools include guidelines for project management and problem definition, tips for acquiring existing information and identifying issues of public concern, worksheets on how to identify and analyze potential impacts on resources, ideas for enhancing NEPA documents, and a NEPA process checklist. The tools can be used at various stages of the NEPA process and provide a toolbox of guidelines and techniques to improve implementation of the NEPA process by focusing the pertinent information for decisionmakers and stakeholders. KEY WORDS: National Environmental Policy Act; NEPA; Environmental impact assessment; Ecosystem management 相似文献
839.
Isla Victoria (Nahuel Huapi National Park, Argentina), a large island dominated by native Nothofagus and Austrocedrus forest, has old plantations of many introduced tree species, some of which are famed invaders of native ecosystems elsewhere.
There are also large populations of introduced deer and shrubs that may interact in a complex way with the introduced trees,
as well as a recently arrived population of wild boar. Long-standing concern that the introduced trees will invade and transform
native forest may be unwarranted, as there is little evidence of progressive invasion, even close to the plantations, despite
over 50 years of opportunity. Introduced and native shrubs allow scattered introduced trees to achieve substantial size in
abandoned pastures, but in almost all areas neither the trees nor the shrubs appear to be spreading beyond these sites. These
shrub communities may be stable rather than successional, but the technology for restoring them to native forest is uncertain
and probably currently impractical. Any attempt to remove the exotic tree seedlings and saplings from native forest would
probably create the very conditions that would favor colonization by exotic plants rather than native trees, while simply
clear-cutting the plantations would be unlikely to lead to regeneration of Nothofagus or Austrocedrus. The key to maintaining native forest is preventing catastrophic fire, as several introduced trees and shrubs would be favored
over native dominant trees in recolonization. Deer undoubtedly interact with both native and introduced trees and shrubs,
but their net effect on native forest is not yet clear, and specific management of deer beyond the current hunting by staff
is unwarranted, at least if preventing tree invasion is the goal. The steep terrain and shallow soil make the recently arrived
boar a grave threat to the native forest. Eradication is probably feasible and should be attempted quickly. 相似文献
840.
The aim of this paper is to assess the conditions that influence foreign direct investment in the mineral industries of China and India. The paper first surveys literature on the determinants of foreign direct investment to identify key conditions, under which host countries attract mining FDI. It then builds an evaluative framework which allows for comparative analysis. The paper then comparatively evaluates the performance of foreign investment regimes that govern mineral industries in China and India. Its findings show that the overall conditions for foreign mining investment in China and India are not favourable and that substantial policy, regulatory and other changes in both countries need to be made if more investment is to flow. 相似文献