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141.
中国热带东,西部地区冬季气候的差异与橡胶树的引种 总被引:8,自引:0,他引:8
由于青藏高原的动力影响,使得西部地区冬季出现下沉气流,多日照,利于橡胶树的越冬,而东部则出现上升气流,少日照,不利越冬,又由于青藏高原大山体,冬季明显地阻挡低层空气平流,导致高原南侧的西部地区冬季降温和缓,有利橡胶树越冬,而东部地区因无高大山体阻挡,寒潮初期降温剧烈,后期低温阴雨天气持续甚久,易导致橡胶树的严重寒害。 相似文献
142.
在未来的亚洲中中气候变冷过程中,从咸海干涸海底和卡拉博加戈尔湾等等内陆湖泊和地区吹起的盐粒,农田排出的农药残余物,尘埃微粒等-固态大陆型气溶胶具有主要的作用。在这一过程中,环流及该区域的生物系统对气候的变化可能起着相反的影响。 相似文献
143.
未来全球气候变化是人们关注的重大课题。从内蒙古盐湖近20ka气候演变的研究可知,地质时期和历史时期气候波动变化是有规律可循的。用已经了解的这种变化规律来予测未来气候变化是有价值的。研究表明,未来1ka左右全球为暖期,之后将进入下一个冰期。 相似文献
144.
Secondary ferrimagnetic minerals in Welsh soils: a comparison of mineral magnetic detection methods and implications for mineral formation 总被引:20,自引:0,他引:20
J. A. Dearing P. M. Bird R. J. L. Dann S. F. Benjamin 《Geophysical Journal International》1997,130(3):727-736
A study of mineral magnetic parameters was carried out on a Late Pleistocene and Holocene sedimentary sequence (of nearly 18 m) from Lake Bledowo (central Poland). Sediments of Lake Bledowo have already been analysed for bulk sediment mineralogy and biogenic materials. The mineral magnetic stratigraphy confirms the major changes in palaeo-environmental conditions that have been deduced from other methods. The most important mineral magnetic change results from the authigenetic formation of ferrimagnetic greigite, Fe3 S4 , during the beginning of lacustrine conditions (± 12 000 yr BP). Our data also indicate a detrital origin of overlying ferrimagnetic iron oxides. It is suggested that they originate from brown soils developed on the boulder clay constituting the west side of the lake shore. Variations of ferrimagnetic iron oxide size are related to the early diagenetic processes in the sediment. Larger particles are present in periods with early diagenesis of organic matter in anoxic conditions. This indicates the dissolution of fine magnetic particles by iron-oxide-reducing bacteria and results in homogeneous magnetic grain sizes, despite their origin from soils, characterized by a multimodal grain-size distribution. 相似文献
145.
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147.
本文剖析了柿竹园钨锡钼铋矿床地勘阶段地质观察粗浅,勘探投入超前,探明储量积压、B+C级储量比例偏大等不合理的勘查工作及其原因。在此基础上,探讨矿区合理的勘探程度,储量比例及由此带来的经济效益。 相似文献
148.
Summary This paper explores an approach to estimation of the viscoelastic parameters of weak floor strata using plate-loading tests. Mathematical equations are derived to describe deformation-time history for the standard Burgers model under three-dimensional stress-strain conditions, which are verified with a finite element model. A number of time-dependent in-mine plate-loading tests were conducted and the values of the viscoelastic parameters were estimated based on the derived equation. It is shown that large discrepancies between the parameter values estimated from the plate-loading tests and those acquired from the in-mine convergence data are the results of neglecting adjacent pillar interaction. Finite element modelling was conducted to investigate the effects of adjacent pillar interactions upon the pillar settlement. Based on the finite element analyses, a correction curve was developed to adjust the viscoelastic parameter values to take into account the interaction between adjacent pillars. With the correction, the parameter values estimated from the plate-loading tests compared favourably with those acquired from the in-mine convergence results. 相似文献
149.
Acid mine drainage (AMD) occurs when sulfide minerals are exposed to an oxidizing environment. Most of the methods for preventing
AMD are either short-term or high cost solutions. Coating with iron phosphate is a new technology for the abatement of AMD.
It involves treating the sulfide with a coating solution composed of H2O2, KH2PO4, and sodium acetate as a buffer agent. The H2O2 oxidizes the sulfide surface and produces Fe3+ so that iron phosphate precipitates as a coating on the sulfide surface. Experiments performed under laboratory conditions
prove that an iron phosphate coating can be established on pyrrhotite surfaces with optimal concentrations of the coating
solution in the range of: 0.2M/0.01M H2O2, 0.2M KH2PO4, and 0.2M sodium acetate NaAc, depending on the experimental scale. Iron phosphate coating may be a long-term solution to
the problem of AMD. The method would be easy to implement; the reagent cost, however, is not low enough, although it is lower
than the conventional treatment with lime.
Received: 30 March 1995 · Accepted: 6 September 1995 相似文献
150.
N. F. Gray 《Environmental Geology》1996,27(4):358-361
Both sulfate and conductivity are useful indicators of acid mine drainage (AMD) contamination. Unlike pH, they are both extremely sensitive to AMD even where large dilutions have occurred. The advantage of using sulfate to trace AMD is that unlike other ions it is not removed to any great extent by sorption or precipitation processes, being unaffected by fluctuations in pH. These two parameters are also closely associated as would be expected, as conductivity is especially sensitive to sulfate ions. Therefore, as sulfate analysis is difficult in the field, conductivity can be used to predict sulfate concentration in both AMD and contaminated surface waters using regression analysis. Most accurate predictions are achieved by using equations given for specific conductivity ranges or AMD sources. There is also potential to use conductivity to predict approximate concentrations of key metals when the pH of the water is within their respective solubility ranges. 相似文献