海洋生物气溶胶增加可能导致晚新生代全球变冷的模型计算   总被引：1，自引：0，他引：1  

李高军  陈骏  季峻峰  盛雪芬  李涛 《高校地质学报》2009,15(2):171

整合海洋碳、锶、锇同位素记录的地球化学元素循环模型表明,晚新生代大陆化学风化通量随着全球物理侵蚀的增强而升高,促使更多的营养元素磷输入到海洋中,引起海洋生物生产力的爆发,而浮游生物产生大量的二甲基硫最终导致海洋上空的大气气溶胶浓度急剧上升。气溶胶浓度增加一方面会增加云的覆盖率和反射率,据初步估计,该效应导致距今7 Ma 内地表接收的太阳能减少了16.5 Wm-2,相当于全球平衡温度降低13 ℃;另一方面会抑止云层的降水效能,有利于水汽向高纬地区传输并形成降雪,最终促进两极冰盖生长,从而驱动新生代晚期全球性的气候变冷。  相似文献   

High-frequency rock temperature data from hyper-arid desert environments in the Atacama and the Antarctic Dry Valleys and implications for rock weathering   总被引：1，自引：0，他引：1  

Christopher P. McKay  Jamie L. Molaro  Margarita M. Marinova 《Geomorphology》2009,110(3-4):182-187

In desert environments with low water and salt contents, rapid thermal variations may be an important source of rock weathering. We have obtained temperature measurements of the surface of rocks in hyper-arid hot and cold desert environments at a rate of 1/s over several days. The values of temperature change over 1-second intervals were similar in hot and cold deserts despite a 30 °C difference in absolute rock surface temperature. The average percentage of the time dT/dt > 2 °C/min was ~ 8 ± 3%, > 4 °C/min was 1 ± 0.9%, and > 8 °C/min was 0.02 ± 0.03%. The maximum change over a 1-second interval was ~ 10 °C/min. When sampled to simulate data taken over intervals longer than 1 s, we found a reduction in time spent above the 2 °C/min temperature gradient threshold. For 1-minute samples, the time spent above any given threshold was about two orders of magnitude lower than the corresponding value for 1-second sampling. We suggest that a rough measure of efficacy of weathering as a function of frequency is the product of the percentage of time spent above a given threshold value multiplied by the damping depth for the corresponding frequency. This product has a broad maximum for periods between 3 and 10 s.  相似文献   

Phreatic drainage conduits within quartz sandstone: Evidence from the Jurassic Precipice Sandstone, Carnarvon Range, Queensland, Australia     

Robert A.L. Wray   《Geomorphology》2009,110(3-4):203-211

Discrete underground drainage conduits in quartz sandstones are far less common than in limestones. This paper provides field evidence from the quartzose Precipice Sandstone in the Carnarvon Range of south-central Queensland, Australia, for tubular underground drainage networks similar in many ways to limestone conduits. Diameters range from less than 1 or 2 cm to over 1.5 m, most display a near-circular to oval cross-section that seems to suggest phreatic or epiphreatic development, and the internal surfaces of many are case-hardened by secondary silica deposits. A number of the region's perennial springs appear to be fed by such tubes.The dominant vertical jointing of the quartz sandstone and relatively high permeability of the sandstone are important controls on tube formation. Solutional weathering of the sandstone is widespread, and is followed by the removal of loosened sand grains by flowing underground water, the process of ‘arenisation’. Tube development would appear to have been happening for a very long time, and may still be occurring. A model for tube network formation is proposed.These findings highlight our potentially poor understanding of groundwater flow within some quartz sandstones, and may have important groundwater management implications.  相似文献   

Reef corals bleach to resist stress     

Obura DO 《Marine pollution bulletin》2009,58(2):206-212

A rationale is presented here for a primary role of bleaching in regulation of the coral-zooxanthellae symbiosis under conditions of stress. Corals and zooxanthellae have fundamentally different metabolic rates, requiring active homeostasis to limit zooxanthellae production and manage translocated products to maintain the symbiosis. The control processes for homeostasis are compromised by environmental stress, resulting in metabolic imbalance between the symbionts. For the coral-zooxanthella symbiosis the most direct way to minimize metabolic imbalance under stress is to reduce photosynthetic production by zooxanthellae. Two mechanisms have been demonstrated that do this: reduction of the chlorophyll concentration in individual zooxanthellae and reduction of the relative biomass of zooxanthellae. Both mechanisms result in visual whitening of the coral, termed bleaching. Arguments are presented here that bleaching provides the final control to minimize physiological damage from stress as an adversity response to metabolic imbalance. As such, bleaching meets the requirements of a stress response syndrome/general adaptive mechanism that is sensitive to internal states rather than external parameters. Variation in bleaching responses among holobionts reflects genotypic and phenotypic differentiation, allowing evolutionary change by natural selection. Thus, reef corals bleach to resist stress, and thereby have some capacity to adapt to and survive change. The extreme thermal anomalies causing mass coral bleaching worldwide lie outside the reaction norms for most coral-zooxanthellae holobionts, revealing the limitations of bleaching as a control mechanism.  相似文献   

基于抽样调查的安徽农村民居震害预测与减灾对策周安   总被引：2，自引：0，他引：2       下载免费PDF全文

周安  孙洁  杨勇 《地震学报》2009,31(1):100-107

在安徽省的皖北、皖中和皖南地区,分别抽样4个乡镇总计781户农村民居,进行抗震性能调查,得出安徽省农村住宅在建筑年代、结构形式、建筑材料、地基基础及构造连接等方面的统计数据．在此基础上,运用建筑物地震易损性的概率分析法,对所调查的民居进行震害预测．分析表明,安徽农村民居在基本设防烈度地震作用下,尚不会发生毁灭性破坏,但中等破坏将较大面积发生．提出了农村民居防震减灾的政府管理和技术措施等对策．经济分析认为,增加约3％——4％建房投资,即可基本实现国务院的防震减灾目标．   相似文献   

谈地电场地埋电缆出现漏电现象快速检测的方法     

王新胜  曹文强  陈常俊  魏锦龙 《山西地震》2009,(2):28-30

文章简要介绍了如何利用接地电阻测试仪来快速检测地电场地埋电缆漏电的原理和方法,对地震台站地电观测排除故障,提高观测质量具有一定的可行性和实用性。  相似文献   

内蒙古6种沙生柳树叶片解剖结构的抗旱性分析   总被引：8，自引：4，他引：4  

董建芳  李春红  刘果厚  周世权  苏亚拉图 《中国沙漠》2009,29(3):480-484

利用常规石蜡切片、光学显微镜观察的方法,对内蒙古地区6种沙生柳树叶片的解剖结构进行比较分析。结果表明,6种柳树的叶片结构具有相似性,均为全栅型的等面叶,表皮均具有角质层,主脉为双韧维管束,栅栏组织发达,5～6层。差异表现在角质层和表皮厚度、主脉和叶片厚度、栅栏组织的厚度等方面。应用SAS和SPSS软件进行分析,根据几种柳树叶片的结构特征,得出抗旱性大小顺序依次为：黄柳、砂杞柳、沙柳、乌柳、筐柳、小红柳。  相似文献   

南极格罗夫山100块陨石的矿物-岩石学特征          下载免费PDF全文

戴德求  王道德  王桂琴 《极地研究》2009,21(4):153-166

本文主要报道了南极格罗夫山新回收的100块陨石的岩石学和矿物化学特征。并根据矿物-岩石学特征,划分了它们的化学-岩石类型:6块属于非平衡型普通球粒陨石(H3和L3群各3块);92块属于平衡型普通球粒陨石,包括:H群24块(13块H4,10块H5,1块H6),L群64块(2块L4,44块L5,18块L6),LL群4块(3块LL4,1块LL5);另外两块属于石-铁陨石。6块非平衡型普通球粒陨石保存了原始的岩石学和矿物化学特征,包括:清晰的球粒结构、橄榄石和低钙辉石具有明显的成分环带以及极不均一的化学组成等。92块平衡型普通球粒陨石中的橄榄石和低钙辉石显示出均一的化学组成,表明它们达到了一定的热力学平衡。这些普通球粒陨石受到的风化作用以W1和W2为主,所占比例高于90%,表明南极陨石受到的风化作用不强烈。有约40%的陨石样品受到了强烈的冲击作用,并产生冲击脉或者冲击囊,它们是研究高压冲击矿物和冲击作用的理想样品。  相似文献   

镜泊湖火山台网防雷地网的建设     

崔东源  马宝君  李英波 《地震地磁观测与研究》2009,30(3):94-97

镜泊湖火山台网位于崇山峻岭之中,经常遭到强雷电袭击。为了使台网设备稳定高效运转,减轻雷电地干扰,我们对台网的防雷设施进行了建设,取得了非常好的防雷效果。  相似文献   

扩底桩抗拔承载特性数值分析     

张金利  ;阮孝政  ;蔡桂林 《地震学刊》2009,(6):624-631

基于通用软件ABAQUS,建立了扩底抗拔桩三维弹塑性有限元模型,通过对模型的计算与分析,探讨了扩底桩的抗拔承载特性。为验证数值模型的可靠性,将数值计算得到的荷载－位移关系曲线与试桩资料进行比较,两者吻合较好,表明本文所建立的模型可较好地模拟扩底抗拔桩的工作性状。通过计算与分析,探讨了扩底抗拔桩的轴力、侧摩阻力分布特征,桩身和扩大头周围土体变形与塑性应变的发展规律,以及扩大头的挤压作用对扩大头周围土体竖向应力的影响。同时,通过变动参数研究了扩大头的形状、土体的性质对扩底桩抗拔承载力的影响,结果表明,扩大头直径和扩大头周围土体的性质对抗拔承载力的影响较大,而扩底高度的影响相对较小。  相似文献