新疆哈密侏罗纪几种成煤植物   总被引：3，自引：0，他引：3  

王士俊  唐修义  张井  于冰 《新疆地质》1994,(2)

对新疆哈密三道岭露天煤矿中林罗统西山窑组煤岩中几种成煤植物的角质层、丝炭化进行了研究，其中包括四种角质层：本内苏铁类、银杏类（Ⅰ）（可能属于Ｐｈｏｅｎｉｃｏｐｓｉｓ）、银杏类（Ⅱ）（可能属于Ｇｉｎｋｇｏ）和松柏类；一种半丝炭化的木材（属于松柏类的罗汉松木属Ｐｏｄｏｃａｒｐｏｘｙｌｏｎ）。在这几种成煤植物中，银杏类和松柏类植物较为丰富，而苏铁类则较贫乏，说明前两者是西山窑组主要的成煤植物，同时也反映出成煤时期的古气侯较为温凉。  相似文献   

Nutrient evaluation of some arid range plants in Saudi Arabia     

Ali A. Al-Jaloud  Shaukat A. Chaudhary  Isam I. Bashour  Salahuddin Qureshit  Abdullah Al-Shanghitti 《Journal of Arid Environments》1994,28(4)

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Regular wave pressures and forces on submerged pipelines near a sloping boundary     

K. A. Roopsekhar  V. Sundar 《Ocean Engineering》2004,31(17-18):2295-2317

The hydrodynamic pressures induced by regular waves around the circumference of a pipeline normal to the wave direction and near a rigid bed of slope 1:10 have been investigated in a wave flume. The pressures were integrated to obtain the force time history, from which the peak horizontal and vertical forces are evaluated. The maximum and root mean square horizontal and transverse force coefficients are correlated with the Keulegan–Carpenter (KC) number. The effect of the distance between the sloping bed and the pipeline on the force coefficients is discussed. The force coefficients are found to decrease with an increase in KC number and with the decrease in the relative clearance of the pipeline from the boundary. In addition, the reflection characteristics of the sloping bed in the presence of the pipeline as a function of surf similarity parameter and their comparison with the results from existing literature are also reported. The details of the model setup, experimental procedure, results and discussion are presented in this paper.  相似文献   

Xylem sap flows of irrigated Tamarix elongata Ledeb and the influence of environmental factors in the desert region of Northwest China     

Yanping Qu  Shaozhong Kang  Fusheng Li  Jianhua Zhang  Guimin Xia  Wangcheng Li 《水文研究》2007,21(10):1363-1369

Tamarix elongata Ledeb is a desert shrub found in the desert region of Northwest China and is commonly cultivated as a sand‐holding plant in this region. To understand its water requirement and the effects of climate conditions on its growth, trunk xylem sap flows of irrigated 8‐year‐old Tamarix elongata Ledeb plants were monitored continuously with heat‐pulse sap flow meters for the entire season. Soil moisture contents at 0–300 cm layer depth were also measured with a tube type time domain reflectometry (Tube‐TDR). Meteorological factors, i.e. solar radiation, air temperature, relative humidity and wind speed were simultaneously monitored by an automatic weather station at the site. Daily and seasonal variations of the trunk sap fluxes and their correlations with the meteorological factors, reference evapotranspiration and soil moisture contents in the root‐zone were analysed. The results indicated that frost influenced the trunk sap flux greatly under irrigated conditions, although the flux generally fluctuated with the variation of environmental factors and showed a mean trunk sap flux of 4·18 l d^?1. There was a significantly exponential relationship between sap flux and the reference value of crop evapotranspiration, with a correlation coefficient of R² = 0·7172. The sap flux also had a significant correlation with the soil water contents at a depth of 150–300 cm from soil surface (R² = 0·5014). The order of the main meteorological factors affecting the sap flux of Tamarix elongata Ledeb trees was solar radiation > air temperature > vapour pressure deficit > relative humidity > wind speed. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

The effect of relative crest submergence on wave breaking over submerged slopes     

C.E. Blenkinsopp  J.R. Chaplin   《Coastal Engineering》2008,55(12):967-974

Experiments were performed in a wave flume to measure the intensity, transmission and reflection of waves breaking over a submerged reef with an offshore gradient of 1:10. The results demonstrate that the relative water depth over the reef crest (h_c/H_o) is a dominant factor affecting the breaking characteristics. In particular it is found that as the relative crest submergence is reduced, there is a considerable increase in the intensity of wave breaking over the reef that can be quantified through measurements of the air cavity enclosed beneath the plunging jet. It is also shown that there is a corresponding decrease in wave transmission and reflection as the submergence is reduced.  相似文献   

Early human impact in the forest ecotone of southern High Asia (Hindu Kush, Himalaya)     

Georg Miehe  Sabine Miehe  Frank SchlützAuthor vitae 《Quaternary Research》2009,71(3):255-265

The vegetation of the treeline ecotone of the southern declivity of arid High Asia (Hindu Kush, northern areas of Pakistan; Himalaya, northern central Nepal) is dominated by hedgehog-like open dwarf shrublands of thorny cushions. Since climatically sensitive ecotones are always also sensitive to human impact, the question arises whether the current lack of forests is a result of the Subboreal climate decline or of human impact. Due to inadequate knowledge of the pollen flora and of ecological indicator values of the plants, pollen analyses in High Asia have mainly been limited to the regional verification of globally known climatic impulses. However, the role of human impact on regional vegetation patterns has been widely neglected. We postulate that today's open dwarf shrublands replace woodlands and forests. Isolated vigorous juniper trees and successful reforestation appear to confirm our hypothesis. An abrupt decline of Pinus forests before 5700 and 5400 ka cal yr BP can be demonstrated. As the first indicator pollen of human impact appeared at both sites synchronous with the forest pollen decline, we infer human impact to be a more decisive cause for this environment change superimposing the effects of a climatic deterioration. The forests were displaced by open dwarf shrublands.  相似文献   

Environmental assessment of elements and polyaromatic hydrocarbons emitted from a Canadian coal-fired power plant   总被引：1，自引：0，他引：1  

F. Huggins  F. Goodarzi   《International Journal of Coal Geology》2009,77(3-4):282-288

A detailed assessment of elements was carried out at a power plant rated at approximately 760 MW of electricity using western Canadian subbituminous coal. The concentrations of elements of environmental concern (As, Cd, Cr, Hg, Ni, and Pb) in milled coals, ashes, stack-emitted materials. Speciation of As, Cr, and Ni were determined. The polyaromatic hydrocarbons (PAHs) emitted from the stack were also measured. The rates of input of elemental input for As, Cd, Cr, Hg, Ni, and Pb were 28, 0.94, 230, 0.44, 44, and 88 kg/day, respectively; of which only 0.16, 0.01, 0.40, 0.27, 0.15, and 0.04 kg/day, respectively, were stack emitted. The total stack emission of toxic elements is 1.02 kg/day, with Cr being the highest contributor to this group with 0.4 kg/day. However, Hg at 0.27 kg/day has the highest percentage rate of emission at about 60%, while Cd has the lowest at about 1%. The electrostatic precipitator (ESP) removes a significant portion of the elements indicated by their relative enrichment (RE) ratios greater than 0.7. The results show that most of the elements in milled coal are low compared to world coals and other Canadian milled coals.Mercury is mostly ( 81%) emitted as gaseous elemental mercury (GEM), with 19% as reactive gaseous mercury (RGM). Particulate mercury is very low and averages about 0.1% of the total mercury at this station. Most of the arsenic in the milled coal is primarily associated with pyrite or as arsenate in its less toxic form of As⁺⁵ (> 95%). In both bottom and fly ashes, more than 95% of the total arsenic is present as As⁺⁵. Chromium in the milled coal and bottom ash is mostly non-toxic (Cr⁺³). The more toxic Cr⁺⁶ comprise less than 5% of the total Cr in the ESP fly ash and the stack-emitted ash. Nickel in milled coal and ashes is in the form of non-toxic Ni⁺², predominantly in coordination with oxygen.The emitted PAHs include acenapthene, fluorene, 2-methyl-fluorene, phenathrene, anthracene, fluoanthene, and pyrene; which are emitted from stack at the combined rate of 3.6 g/day. The concentrations of elements of environmental concern (As, Cd, Hg, Ni, and Pb) emitted to the atmosphere by the power plant in the zone of maximum impact at ground level are lower than those listed in the Health Guidelines of the USEPA and Canadian National Air Pollution Surveillance. This is based on stable meteorological conditions, down wind from the power plant for a maximum distance of 3 km.  相似文献   

贵州某电厂大型山体滑坡对工程场地适宜区域划定的影响研究     

余凤先  李渝生  曹卫东  谭光杰 《地质灾害与环境保护》2009,20(4):67-70

随着中国经济高速发展和加强对基本农田的保护,越来越多的大型火电厂建设于山区且多数为坑口电厂,一般会涉及到西南地区主要含煤地层二叠系上统龙潭组（P2l）。龙潭组是由海陆交替相含煤砂、页岩等软质、易滑地层构成的,在龙潭组岩层区建设坑口电厂大型山体滑坡等不良地质作用是不可回避的工程地质问题。本文以贵州省某电厂大型山体滑坡对工程场地适宜区域划定的影响研究为出发点,认为山区坑口电厂建设中对大型山体滑坡的分析评价只要遵守查明基本地质条件,评价滑坡稳定性,划定适宜建设区域,提出处理建议的基本工作流程,大型火力电厂在大型山体滑坡附近建设是可行的。  相似文献   

长白山哈泥泥炭地7种苔藓分布与环境关系研究   总被引：1，自引：1，他引：0  

陈旭  卜兆君  王升忠  李鸿凯  姜丽红 《湿地科学》2008,6(2)

在长白山哈泥泥炭地调查7种苔藓的典型生境,共计93个样方,计测样方中苔藓植物的盖度和包括泥炭全氮（TN）、全磷（TP）、K^＋和Ca^2＋等在内的9个环境因子,应用典范对应分析对数据进行处理,做出样方、物种与环境因子关系二维排序图,排序图直观地反映苔藓植物与环境因子间的关系。结果表明,排序图中同种苔藓为主的样方多数集中分布,个别分散分布;水位埋深、沼泽水pH以及乔木郁闭度和灌木盖度是影响泥炭地苔藓植物生态位分异的主要环境因子,泥炭全磷（TP）对苔藓植物分布影响较大。7种苔藓中,尖叶泥炭藓（Sphagnum capilifolium）、大泥炭藓（S．palustre）在乔木郁闭度和pH梯度上,喙叶泥炭藓（S．fallax）、沼泽皱缩藓（Aulacomnium palustre）在水位埋深和灌木盖度梯度上,生态位分异明显。锈色泥炭藓（S．fuscum）、桧叶金发藓（Polytrichum juniperinum）和中位泥炭藓（S．magellanicum）在各个环境梯度上生态位都比较相似。  相似文献   

喀斯特山区植物碳同位素组成特征及其对水分利用效率的指示——以贵州花溪杨中小流域为例   总被引：7，自引：1，他引：6  

杨成  刘丛强  宋照亮  郑厚义  刘占民 《中国岩溶》2007,26(2):105-110

测定了贵州喀斯特山区灌丛12种主要植物叶片的δ13 C值,研究了植物叶片碳同位素组成特征,并分析了植物的水分利用效率。结果表明: 该区植物叶片的碳同位素组成的变化范围为- 26. 98‰～ - 29. 15‰ ,平均值为- 28. 14‰。研究区δ13 C值的分布相对均匀,除高于我国热带雨林区植物外,低于其它地区。此外,植物的碳同位素组成存在较大的种间差异,生境的变化对植物的碳同位素组成有着一定的影响,但不同植物种对生境的响应不同。植物的δ13 C值从生长初期到末期有降低的趋势,但不同植物种的变化趋势存在差异。植物δ13 C值随海拔的增加而增大,但不同植物种δ13 C值随海拔增加的程度存在差异。不同植物种之间的水分利用效率不同,相同植物种在不同的生境条件下其水分利用效率也有差异。植物生长初期的水分利用效率要比后期的高; 高海拔处植物水分利用效率要比低海拔处植物的高。   相似文献