钙华生物沉积作用研究进展与展望     

汪智军  殷建军  蒲俊兵  袁道先 《地球科学进展》2019,(6):606-617

弄清钙华生物沉积作用有助于更好地理解钙华微岩相结构和地球化学特征的气候环境指示意义。总结和综述了与钙华沉积相关的生物群落、生物成因钙华微岩相结构、钙华生物沉积作用过程及其对钙华地球化学特征影响的研究进展,并展望了未来的研究重点。细菌、藻类和苔藓等广泛参与到钙华沉积中,形成了许多不同类型的孔隙结构、晶体结构和纹层结构。生物沉积过程主要包括:①生物生长扰动水流使得CO2逸出;②代谢作用(如光合作用)过程诱导碳酸钙沉积;③"表面控制"过程影响晶体成核及生长。生物沉积作用驱动了元素的迁移转化,对沉积水体和钙华地球化学特征具有重要影响。钙华在地球生物学研究中具有重要潜力,未来需要加强现代钙华沉积中的物理化学和生物过程相互作用机制及其各自贡献的量化研究,以便准确地解译钙华沉积记录。  相似文献   

柴达木盆地西部古近系石膏及其硫同位素分布特征          下载免费PDF全文

郑希民  杨柳  易定红  王朴 《沉积与特提斯地质》2019,39(4):65-70

石膏是柴达木盆地油气圈闭的盖层之一。根据石膏层含量统计和石膏~(34)S_(V-CDT)分析,发现柴达木盆地古近系石膏主要分布于靠近阿尔金山的狮子沟凹陷和小梁山凹陷,石膏含量在垂向上具有旋回性。石膏的~(34)S_(V-CDT)值分布范围很大,为-23.3～71.4%,属国内外罕见。其原因是来自阿尔金山的硫酸盐~(34)S值很低,而由盆缘向盆内随着还原环境的强化,细菌的分馏作用逐渐强烈,导致~(34)S_(V-CDT)值的巨大差异。石膏~(34)S_(V-CDT)值的主控因素为硫酸盐~(34)S_(V-CDT)初始值、硫酸盐补给速率和还原菌分馏作用的强度。形成石膏的硫酸盐来自阿尔金山,经由狮子沟凹陷进入盆地,然后向盆地其它方向扩散。  相似文献   

对地强耦合拖曳式检波系统的研制     

张燕生  冷广昇  赵镨  王秀荣 《中国煤炭地质》2019,(3):72-76

因城市地下浅层空间探测要求在硬化路面上进行无损检测,而传统的采集方法是采用石膏或其它粘合剂固定检波器进行数据采集,施工效率较低,为此开发研制了一种对地强耦合拖曳式检波系统。该系统通过信号线缆和装配在耦合底盘上的检波装置形成单条或多条24道的拖曳式检波串,从而实现二、三维数据采集。通过拖拽式检波系统和粘接式检波系统在相同激发条件下数据对比,其在波形能量、频谱、功率谱、相位谱及叠加效果等方面具有较高的一致性,且拖拽式检波系统无明显的共振现象。试验证明该系统对地耦合性能良好,施工效率高,适用于城市浅层地震勘探。  相似文献   

Changes of Monsoonal Temperate Glaciers in China during the Past Several Decades under the Background of Global Warming     

Yuanqing He  Zongxing Li  Bo Song  Ningning Zhang  Xianzhong He  Wilfred H.Theakstone  Tao Pu  Qiao Liu 《寒旱区科学》2008,(1):0059-0067

Based on various data,it can be concluded that eight monsoonal temperate glaciers in China were in stationary or ad-vancing between 1900s~1930s and 1960s~1980s,and were in retreating during 1930s~1960s and 1980s~present under the background of climate warming.The total glacier area has reduced by 3.11 km2 with a mean front altitude rise of 3.2 m/yr and 4 glaciers have disappeared in Mt.Yulong during 1957~1999.Mass balance records indicated that glaciers had suf-fered a constant mass loss of snow and ice during the last several decades,and the accumulated mass balance in Hailuogou basin in Mt.Gongga was 10.83 m water equivalent in the past 45 years with a annual mean value of-0.24 m,and the value at Baishui glacier No.1 was-11.38 m water equivalent in the past 52 years with-0.22 m/yr.The inverse variation between mass balance and temperature in China and the Northern Hemisphere reflected that climate warming is mainly corresponding to constant ice and snow mass loss in the past 50 years.The change of the glaciers’ surface mor-phology has occurred since the 1980s,such as enlargement of glacier-lake and ice falls,resulted from the accelrative cli-mate warming.  相似文献   

Variations of albedo and spectral reflectance on Qiyi Glacier in Qilian Mountains during the ablation season     

Xi Jiang  NingLian Wang  JianChen Pu  JianQiao He  Liang Chen 《寒旱区科学》2009,1(1):0059-0070

Based on the data observed at two sites (site H1, 4,473 m a.s.l., and site H2, 4,696 m a.s.l.) on Qiyi Glacier in Qilian Mountains, China, by automatic weather station and spectral pyranometer during the period of June 9 through September 27, 2006, we investigated the temporal and spatial variations in surface albedo and spectral reflectance on the glacier. At site H1, the daily mean surface albedos fluctuated between 0.233 and 0.866, which were significantly affected by the air temperature on the glacier. It was found that the albedos clearly showed a diurnal cycle with the lowest value at noon at the two observation sites over the study period, and the difference of albedos between the upper site H2 and the lower site H1 also showed diurnal cycle but with the highest value at noon. The reflectance on the glacier was higher in the ultraviolet (0.28-0.4 μm) and visible (0.4-0.76 μm) wavelengths, lower in the near infrared wavelength (0.76-3 μm), which is quite contrary to the spectral reflectance on other ground surfaces. At the two observation sites, the spectral reflectance declined in all wavelengths with the ablation of snow generally. However, it declined drastically in ultraviolet (0.28-0.4 μm) and 0.6-0.7 μm wavelength, and declined less in 0.4-0.5 μm wavelength. On fresh snow surface, the spectral reflectance had the high values of 0.983 and 0.815 in the ultraviolet and visible (0.4-0.76 μm) wavelengths, respectively; but it had a relatively lower value of 0.671 in near infrared (0.76-3 μm) wavelengths. However, on dirty and melting ice surfaces, the reflectance had the very low values of 0.305 and 0.256 in the ultraviolet and visible wavelengths, with the lowest value of 0.082 in near infrared wavelengths. The spectral reflectance also showed a diurnal cycle like that of albedo. The diurnal variations of spectral reflectance on snow surface in ultraviolet and visible wavelength changed to a greater degree than that on ice surface. The diurnal variation curves were asymmetrical before and after t  相似文献   

印度洋二维碳循环模式中表层CO2分压分布对物理和生化过程的敏感性试验   总被引：1，自引：0，他引：1  

浦一芬 《气候与环境研究》2009,14(3):301-308

利用二维印度洋碳循环模式的模拟结果,集中对表层海洋中的CO2分压分布及其控制因子、海洋生物对海气CO2交换的影响、海洋营养物含量的改变和海洋环流的改变对大气CO2浓度的影响等进行了深入的分析和讨论,并与实际的GEOSECS观测数据的分析结果做比较;研究了与表层海洋CO2分压相关的海洋条件,较详细讨论了形成海洋表层CO2源与汇系统的决定因素及其相对重要性,得到了海洋热力因子和海洋环流对海洋表层的CO2化学过程起着决定性作用而生物过程仅处于次要地位的重要结论。此外,还利用建立的海洋碳模式进行了一些有意义的数值试验,详细讨论了海洋的物理化学因子改变对大气CO2浓度的可能影响。    相似文献   

Fluvial hydraulics of hyperconcentrated floods in Chinese rivers     

Zhao‐Yin Wang  Pu Qi  Charles Steven Melching 《地球表面变化过程与地形》2009,34(7):981-993

Hyperconcentrated floods, with sediment concentrations higher than 200 kg/m³, occur frequently in the Yellow River and its tributaries on the Loess Plateau. This paper studies the fluvial hydraulics of hyperconcentrated floods by statistical analysis and comparison with low sediment concentration floods. The fluvial process induced by hyperconcentrated floods is extremely rapid. The river morphology may be altered more at a faster rate by one hyperconcentrated flood than by low sediment concentration floods over a decade. The vertical sediment concentration distribution in hyperconcentrated floods is homogeneous. The Darcy–Weisbach coefficient of hyperconcentrated floods varies with the Reynolds number in the same way as normal open channel flows but a representative viscosity is used to replace the viscosity, η. If the concentration is not extremely high and the Reynolds number is larger than 2000, the flow is turbulent and the Darcy–Weisbach coefficient for the hyperconcentrated floods is almost the same as low sediment concentration floods. Serious channel erosion, which is referred to as ‘ripping up the bottom’ in Chinese, occurs in narrow‐deep channels during hyperconcentrated floods. However, in wide‐shallow channels, hyperconcentrated floods may result in serious sedimentation. Moreover, a hyperconcentrated flood may cause the channel to become narrower and deeper, thus, reducing the flood stage by more than 1 m if the flood event lasts longer than one day. The fluvial process during hyperconcentrated floods also changes the propagation of flood waves. Successive waves may catch up with and overlap the first wave, thus, increasing the peak discharge of the flood wave during flood propagation along the river course. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

矿井物探技术应用现状与发展展望   总被引：3，自引：1，他引：2       下载免费PDF全文

韩德品  赵镨  李丹 《地球物理学进展》2009,24(5):1839-1849

通过回顾近六十年来矿井物探的发展历程,简要分析总结了国内外现有的煤矿矿井物探技术的分类与特点、研究现状与应用成果,详细介绍了主要矿井物探方法技术（矿井地震法、矿井电磁法）的研究应用新进展,提出了目前我国矿井物探技术存在的一些迫切需要解决的问题和今后的发展方向.结果表明：矿井物探是地面勘探技术的重要补充,是矿井地质工作的重要手段,它相对于常规的矿井地质手段而言,具有更准确、更快捷、更方便等特点,已成为我国煤矿现代化安全生产中必备的探测技术手段,具有广阔的发展前景.  相似文献   

准噶尔盆地积雪储量的遥感反演及变化特征分析   总被引：2，自引：0，他引：2  

李杨  顾建丽  张璞  刘艳  马丽云 《干旱区地理》2010,33(4)

利用被动微波遥感SSM/I亮温数据反演的积雪深度,采用积雪密度经验算法,计算了准噶尔盆地1987-2008年逐日雪储量及其分布状况。结果表明:(1)准噶尔盆地年最大雪储量22 a平均为4.53×109m3,最大年份为1994/1995年冬季,雪储量达7.13×109m3,最小年份为1995/1996年冬季,雪储量为2.74×109m3。(2)准噶尔盆地冬季雪储量空间分布不均匀,雪储量较大的区域分布在阿尔泰山南麓和天山北麓,且由盆地边缘向中心逐渐减少,两个明显的低值区分别位于盆地西部克拉玛依地区附近和盆地东部北沙窝附近。(3)季节内变化特征表现为:11月上旬至2月中旬为雪储量缓慢累积的过程,3月上旬雪储量达到峰值,持续时间很短(约15 d),3月中旬至4月下旬雪储量迅速消退,季节内变化主要受降雪和气温年内分配的影响。(4)1987-2008年准噶尔盆地雪储量的年际变化较大,65%的区域呈现线性增加趋势,但不显著。(5)冬季降水量和气温是影响雪储量变化的主要因素,雪储量与冬季降水量呈显著正相关,与气温呈显著负相关关系。  相似文献   

中国旅游气候学研究综述   总被引：9，自引：0，他引：9  

吴普  席建超  葛全胜 《地理科学进展》2010,29(2):131-137

随着全球气候变化的加剧和旅游业的快速发展,气候变化对旅游业的影响逐渐为各界所重视,旅游气候学也因此成为旅游和气候学界研究的热点。文章从文献总量、结构,研究阶段划分,研究内容和方法4个方面回顾我国旅游气候学的研究进展。对我国旅游气候学研究的综述表明：目前,我国旅游气候学研究尚处在初级阶段,方法体系还没建立;旅游气候学研究也没得到旅游学界充分认可,研究领域“留白”较多。未来旅游界要更加充分认识气候变化对旅游业的影响,更多地投入到该领域研究中来;加强旅游气候学理论研究,不断拓宽研究的领域、视角,深入研究旅游者对气候变化的响应;厘清气候变化对旅游业的影响,提出旅游业对气候变化的适应与对策,不断丰富、完善旅游气候学研究。  相似文献