154 resultados para 346.022


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基于1997~1999年野外实验,对高寒草甸小云雀和黄嘴朱顶雀两种雀形目鸟的窝雏数进行增减处理。结果表明,对照组的幼鸟生长率和离巢体重都大于增加组,说明窝雏数增加后,幼鸟质量下降。随着窝雏数增加,这两种幼鸟生长率显著下降(小云雀:r = -0.965, P = 0.035 < 0.05;朱顶雀:r = -0.828, P = 0.022 < 0.05)。窝雏数改变对小云雀幼鸟出飞重影响不显著(r = -0.418, P = 0.528 > 0.05),而对黄嘴朱顶雀有显著的影响(r = -0.901,P = 0.014 < 0.05)。

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From 30 June to 24 September in 2003 ecosystem respiration (Re) in two alpine meadows on the Tibetan Plateau were measured using static chamber- and gas chromatography- (GC) based techniques. Simultaneously, plant removal treatments were set to partition Re into plant autotrophic respiration (Ra) and microbial heterotrophic respiration (Rh). Results indicated that Re had clear diurnal and seasonal variation patterns in both of the meadows. The seasonal variability of Re at both meadow sites was caused mainly by changes in Ra, rather than Rh. Moreover, at the Kobresia humilis meadow site (K_site), Ra and Rh accounted for 54% and 46% of Re, respectively. While at the Potentilla fruticosa scrub meadow (P_site), the counterparts accounted for 61% and 39%, respectively. T test showed that there was significant difference in Re rates between the two meadows (t = 2.387, P = 0.022). However, no significant difference was found in Rh rates, whereas a significant difference was observed in Ra rates between the two meadows. Thus, the difference in Re rate between the two meadows was mainly attributed to plant autotrophic respirations. During the growing season, the two meadows showed relatively low Q(10) values, suggesting that Re, especially Rh was not sensitive to temperature variation in the growing season. Additionally, Re and Rh at the K_site, as well as Rh at the P_site was negatively correlated with soil moisture, indicating that soil moisture would also play an important role in respirations.

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土壤对疏水性有机污染物的吸附实际上是土壤中矿物和有机质两部分共同作用的结果。土壤有机质的作用相当重要,因为与矿物相比,它通常对疏水性有机污染物具有较大的热力学亲合力。因此,土壤吸附有机污染物机理的研究主要是从土壤有机质的角度进行的。土壤有机质组成复杂,主要包括非特异性有机质和腐殖质,其中腐殖质约占有机质总量的50%-80%,包括胡敏酸、富里酸和胡敏素。早期的实验研究认为疏水性有机污染物在土壤有机质相中表现为线性分配,可以用平衡分配系数来描述。但是,随着实验研究的深入,平衡分配模型不能合理解释疏水性有机污染物的一些吸附特征,如非线性吸附、溶质竞争吸附以及解吸过程的滞后现象等。后来,Weber和Huang提出土壤吸附有机污染物的三端元模型。同时Pignatello和Xing提出双模式吸附模型。都认为土壤有机质存在明显的不均匀性,并且提出了“软碳”与“硬碳”的概念.

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大兴安岭南段二叠系大石寨组发育两套火山岩,即林西地区拉斑玄武岩系列的细碧-角斑岩类和大石寨地区钙碱性岩石系列玄武岩和玄武安山岩类。细碧岩的主元素以富铁为特征,成分类似于N-MORB,微量元素表现为岛弧拉斑玄武岩的地球化学特征。细碧岩类形成于大石寨裂陷槽强烈拉张的中心位置,是地幔源区较高程度部分熔融的产生。大石寨地区玄武岩和玄武安山岩类的化学成分表现为大陆缘弧火山岩的地球化学特点,形成于大石寨裂隙槽拉张中心以外的环境,是地幔物质较低程度部分熔融和地壳物质严重混染的产物。大石寨裂隙槽中火山岩的这种独特的成分和组合特点可能反映了裂隙槽的形成是一个快速而短暂的强烈拉张过程。

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在湖北恩施渔塘坝土壤硒分布的调查过程中,发现不同地段田地土壤中存在异常高硒样品。其硒含量变化范围是346~2018mg/kg,平均(899±548)mg/kg(n=11),相对于坝内成土基岩和耕作土硒含量0.5mg/kg与3.5mg/kg的水平而言,表明这些土壤硒受到了外来源硒的严重污染。扫描电子显微镜的观察表明,这些土壤样品中均有大量晶体状自然硒的出现,其特征类似燃煤型成因的自然硒,证实了上世纪50年代后期恩施当地居民石煤火熏土作肥的耕作方式,并直接导致了田地土壤硒的骤然增加。渔塘坝当地居民在1963年间的硒中毒爆发性流行,乃至恩施地区人畜硒中毒的普遍流行,极可能是人为因素引起.

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硒同位素作为非传统稳定同位素的重要组成部分,由于具多价态、多质量数、同位素分馏效应大的特点,已成为目前发展最迅速的同位素之一。本文在综合前人研究成果基础上,结合笔者最新的研究成果,对硒同位素的测试技术做了较全面总结,内容包括样品的化学前处理(TCF技术)、在线的氢化物发生器系统、质谱测试技术、参考物质的标定等,并就自然界中硒同位素的组成、分馏机制及应用潜力做了评述。

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金宝山镁铁一超镁铁岩体是峨眉山大火成岩省一个典型的岩浆Cu-Ni—PGE成矿岩体。在根据成岩机制概算原始岩浆微量元素含量的基础上,通过模式计算,表明原始岩浆强不相容元素相对富集型式不可能由现有原始地幔或亏损地幔模型的单一源区熔融或融体混合作用形成,原始岩浆起源于类似OIB源的地幔柱高程度熔融,熔融程度在2o%左右。

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通过野外调查在渔塘坝硒矿区首次发现了一种新的硒超富集植物-遏蓝菜(Thlaspi arvense L.)。调查结果发现,在自然生长条件下,一年生遏蓝菜叶子中富集硒可高达1427mg/kg,生物富集硒系数可高达68,地上部硒含量最低也超过了500mg/kg,生物富集硒系数最低也超过了10,表现为叶〉根〉叶柄的硒富集特征。多年生遏蓝菜叶、茎和根的硒含量分别为104~163;231~346;444~459mg/奴,生物富集硒系数为2.6~12.4,均大于1,显示出根〉茎〉叶的硒富集特征。尽管多年生遏蓝菜远没有一年生遏蓝菜的硒含量高,但远比一般植物硒含量高,达到了次生硒蓄积植物富集硒的水平,显示遏蓝菜植物可以超富集硒。渔塘坝遏蓝菜的发现将为研究硒在植物中的吸收、转化、富集机理以及提取有效抗癌有机硒化物和修复硒污染生态环境提供新的材料。

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依据新获得的同位素年代学资料和构造岩石地层单元,重新认识了云南哀牢山造山带形成与演化历史。认为:在哀牢山地区元古界深变质岩系属基底的造层;前造山期岩石组合及构造演化为扬子地块西缘被动大陆边缘志留纪深水相碎屑岩→陆缘泥盆纪被动裂谷盆地中火山-沉积岩→石炭纪哀牢山有限洋盆及蛇绿岩石组合→晚二叠世-早三叠世哀牢山洋-陆碰撞成陆及弧火山岩-陆相碎屑岩组合。燕山期主造山期及岩石级合为晚三叠世-侏罗纪前陆盆地磨拉石建造-同造山期中酸性侵入岩-燕山期脆性剪切带及构造岩,喜马拉雅山期陆内造山成原的岩石组合为第三-第四纪陆内山间盆地中磨拉石建造-红河韧性剪切带及构造岩-富碱侵入岩和煌斑岩。

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简述游离烃技术的方法及其特点,并介绍其在沙漠覆盖区构造含油气性评价中的应用实例。

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The applicability of capillary electrophoresis/frontal analysis (CE/FA) for determining the binding constants of the drugs propranolol (PRO) and verapamil (VER) to human serum albumin (HSA) was investigated. After direct hydrodynamic injection of a drug-HAS mixture solution into a coated capillary (32 cm x 50 mu m i.d.), the basic drug was eluted as a zonal peak with a plateau region under condition of phosphate buffer (pH 7.4; ionic strength 0.17) at 12 kV positive running voltage. The unbound drug concentrations measured from the plateau peak heights had good correlation coefficients, r > 0.999. Employing the Scatchard plot, the Klotz plot and nonlinear regression, the drug protein binding parameters, the binding constant and the number of binding sites on one protein molecule, were obtained. The binding constant obtained was compared to a reported equilibrium dialysis result and they are basically in good agreement.

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The heat capacities of crystalline and liquid n-hexatriacontane were measured with an automatic adiabatic calorimeter over the temperature range of 80-370 K. Two solid-to-solid phase transitions at the temperatures of 345.397 and 346.836 K, and a fusion at the temperature of 348.959 K have been observed. The enthalpies and entropies of these phase transitions as well as the chemical purity of the substance were determined on the basis of the heat capacity measurements. Thermal decomposition temperatures of the compound were measured by thermogravimetric analysis. (C) 1999 Elsevier Science B.V. All rights reserved.