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沟谷泥石流运动过程模型试验 总被引:2,自引:0,他引:2
泥石流运动过程是泥石流运动力学核心内容之一.以新疆天山公路K630泥石流为原型,选取几何相似比1:650,推导了泥石流质量、固液两相流速和泥石流冲击力相似比,以流通区为核心,建造了沟谷泥石流试验模型.试验结果表明,泥石流运动具有显著的阵流特性,阵流间隔时间为10s左右,其间嵌套2~3次弱阵现象;阵流期间,泥石流流速和冲击力均较大;从流通区的源头至沟口,流速呈现非线性增大趋势,且泥石流体中固液两相流速变化趋势相似,弯道处泥石流超高现象显著;泥石流运动初期由于泥石流体中固相和液相混和搅拌不均匀而呈现稀性泥石流特征,随后粘性特性增强.这些现象与现场观测结果基本一致. 相似文献
225.
A.J. Karabelas K.V. Plakas E.S. Solomou V. Drossou D.A. Sarigiannis 《Environment international》2009,35(7):1096-1107
The very significant impact of European legislation (Directive 91/414/EEC) on the authorization of plant protection products is reviewed herein, which has resulted in withdrawal of 704 active substances (AS) out of 889 assessed so far. The list of currently approved 276 AS includes 194 AS “existing” in the market before 1993 and 82 “new” AS introduced during the last 15 years. Results of toxicity characterization of the approved AS are also summarized, utilizing several well-known databases. Although significant data gaps exist for a rather large part of the approved AS, it is found that 84 AS are positive for at least one health effect (after chronic and/or acute exposure) including carcinogenicity, reproductive and neuro-developmental disorders, as well as endocrine disruption. The toxicity characterization results of this study are compared to those of recent assessments by other organizations (KemI, the Swedish Chemicals Agency, and the Pesticide Safety Directorate of the UK), where interpretation and use is made of AS “cut-off” criteria foreseen in new EU legislation. These studies report a comparatively smaller AS number with positive toxicity characterization. The possibility of some additional AS withdrawal in the near future, combined with the rather small rate of new AS introduction (approx. 5 per year) suggest that the list of approved AS over the next 10–15 years may not change very drastically. Consideration of the above trends is necessary and instructive in evaluating results of existing health impact assessment (HIA) studies, as well as in planning new ones. Due to the very drastic change in the number and type of marketed AS, that took place within the past 8–9 years, it is suggested that new HIA studies (based on epidemiological data after year 2000) should focus on a rather short time frame and, therefore, on appropriate cohort groups, e.g. young children. For the same reason, results of epidemiological studies of the past (involving banned AS) should be carefully interpreted and used with caution. 相似文献
226.
A majority of ongoing monitoring of persistent organic pollutants (POPs) is currently focused on chemicals emphasized in the Stockholm Convention. Quantitative detection of other substances (especially those with numerous anthropogenic sources such as polyaromatic hydrocarbons (PAHs)) is, however, also needed since their concentrations are usually several orders of magnitude higher. A goal of this study was to determine how various groups of compounds contribute to total human health risks at the variety of sampling sites in the region of Western Balkan. Distribution of the risks between the gas and particulate phases was also addressed. Results showed that inhalation exposure to organochlorine pesticides (OCPs) does not represent a significant risk to humans, while polychlorinated biphenyls (PCBs) re-volatilized to the atmosphere from contaminated soils and buildings can pose a problem. PCB evaporation from primary sources (currently used PCB-filled transformers or non-adequate storage facilities) generally resulted in much higher atmospheric concentrations than evaporation from the secondary sources (soils at the sites of war destructions). A majority of the human health risks at the urban sites were associated with PAHs. Between 83 and 94% of the cumulative risk at such sites was assigned to chemicals sorbed to particles, and out of it, PAHs were responsible for 99%. 相似文献
227.
Humans can consume a number of types of biota tissues, which have varying propensities to accumulate radionuclides. As a result, depending upon the biota species, the radionuclide and the tissue under consideration, it may be necessary to estimate the percent radionuclide load in specific edible tissues, and in cases where whole organisms are consumed, to estimate the radionuclide load in the whole body of an organism, based on data that have been collected for individual tissues. To accomplish this, data were compiled that can be used to estimate the partitioning patterns and percent loads of various groups of elements in edible tissues of freshwater fishes. General trends in partitioning, such as those provided in this paper, can be used to predict radionuclide transfer to humans and the corresponding potential radiological dose to humans via dietary pathways, in this case following the consumption of fish. 相似文献
228.
结合模糊优选理论和灰色关联分析方法,提出灰色模糊综合评价法,该方法将灰色关联分析作为优属度确定的隶属度计算方法;提出理想环境序列建立遵循的原则,引入梯形模糊数实现定性指标量化并采用变异系数法确定评价指标权重.应用灰色模糊综合评价法对黄河流域河段水电规划的高坝方案和多级开发方案进行了比选研究,计算了两个方案的优属度及其开发性因子、稳定性因子、保护性因子、经济活力因子、社会可接受因子、环境风险因子等6个指标层优属度,结果表明,多级开发方案总体优于高坝方案;多级开发方案的保护性远好于高坝开发方案,而高坝方案的开发性略好于多级开发方案,稳定性、经济活力、社会可接受、环境风险等因子两种方案比较接近.评价结果与流域实际情况比较符合,证明该方法是一种有效的方法. 相似文献
229.
Himayatullah Khan Ehsan Inamullah Khadija Shams 《Environment, Development and Sustainability》2009,11(2):375-392
This study explores the interlinkages among population, environment and poverty and presents empirical evidence in a developing
country like Pakistan. It gives alternative views on population environment linkages. It explains poverty trap, market based
harmony, and dual effect of poverty on the basis of a link between population growth and natural resource degradation. In
addition, the paper also highlights social and political instability through population-poverty-environment spiral. It also
presents empirical evidence on population-environment-poverty nexus in Pakistan. It also compares environmental sustainability
index and human development index for selected Asian countries. The paper also gives scores for different components of environmental
sustainability index for Pakistan and compares these with India. The paper concludes that the causal relationship between
poverty and environment works in both directions, often through changes in GDP and population. Population stress does not
have any significant direct effect on all aspects of environmental status in Pakistan.
相似文献
Himayatullah KhanEmail: |
230.
Ismet ok Menekse Keski Donmez Mine Uner Erkan Demirkaya Bernhard Henkelmann Heqing Shen Jarmila Kotalik Karl-Werner Schramm 《Chemosphere》2009,76(11):1563-1571
Human breast milk offers the optimal nutrition for all infants and have been widely used in biomonitoring programs to assess human exposure to lipophylic environmental contaminants such as polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF) and polychlorinated biphenyls (PCB). There are no previous reports from Turkey on chemically determined levels of PCDDs, PCDFs, and PCBs in human breast milk expressed as World Health Organization (WHO) toxic equivalents (TEQ). To get an overview of the levels of these contaminants in Turkish human milk, samples from 51 Turkish women living in the Ankara, İstanbul, Antalya, Kahramanmaraş, and Afyon provinces were analyzed by high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) throughout 2007. The mean concentrations of WHOPCDD/F-TEQ and WHOPCB-TEQ of all samples from the five regions were 7.5 and 3.1 pg g−1 on a lipid basis, respectively. PCDD/F concentrations ranged between 0.78 and 29.3 pg WHO-TEQ g−1 fat (1.7 and 36.2 pg WHO-TEQ g−1 fat, respectively, including PCB). Of the five studied locations, the lowest levels of ∑TEQs (PCDD/F + PCB) were found in the Afyon (6.8 pg WHO-TEQ g−1 fat) and the highest in the Antalya (15.6 pg WHO-TEQ g−1 fat) province. The results have been discussed in terms of regions and PCDD/F and PCBs for which analyses had been made. The mean levels of PCDD/Fs and PCBs in Turkish human milk are comparable to that found in other countries. 相似文献