西藏普莫雍错不同岩芯环境指标的对比研究及其反映的近200年来环境变化   总被引：4，自引：1，他引：3  

王君波  朱立平  鞠建廷  谢曼平  汪勇 《湖泊科学》2009,21(6):819-826

在西藏南部普莫雍错不同位置处采集了四支岩芯沉积物,对其中一支利用~(210)pb和~(137)Cs方法建立了沉积物的年代序列,并对其他三支岩芯的上部沉积物进行了总有机碳、无机碳、粒度及化学元素含量的分析.结合沉积物年代,对不同岩芯的环境代用指标进行对比,讨论了该地区近200年来的环境变化状况.结果表明,不同位置处采集的岩芯其环境指标变化趋势在整体上具有一定的可比性,但在细节变化与环境指标的数值上仍具有明显的差异,显示了湖泊内部沉积状况的空间差异性,这可能是由于采样点水深、水下地形以及与主要补给河流距离的不同而造成的.PY04岩芯环境指标显示普莫雍错湖区环境在约1900AD之前较为稳定;在约1900-1940AD之间湖区环境波动加剧,地表侵蚀增强,沉积速率加快;湖区环境在1940AD左右发生了明显的变化,温度显著升高,沉积物粒度增大,湖泊处于退缩状态,表明湖泊环境向暖干化方向发展.  相似文献   

Using triple oxygen isotopes and oxygen-argon ratio to quantify ecosystem production in the mixed layer of northern South China Sea slope region     

Zhuoyi Zhu  Jun Wang  Guiling Zhang  Sumei Liu  Shan Zheng  Xiaoxia Sun  Dongfeng Xu  Meng Zhou 《海洋学报(英文版)》2021,40(6):1-2

Quantifying the gross and net production is an essential component of carbon cycling and marine ecosystem studies.Triple oxygen isotope measurements and the O_2/Ar ratio are powerful indices in quantifying the gross primary production and net community production of the mixed layer zone,respectively.Although there is a substantial advantage in refining the gas exchange term and water column vertical mixing calibration,application of mixed layer depth history to the gas exchange term and its contribution to reducing indices error are unclear.Therefore,two cruises were conducted in the slope regions of the northern South China Sea in October 2014(autumn) and June 2015(spring).Discrete water samples at Station L07 in the upper 150 m depth were collected for the determination of δ~(17)0,δ~(18)O,and the O_2/Ar ratio of dissolved gases.Gross oxygen production(GOP) was estimated using the triple oxygen isotopes of the dissolved O_2,and net oxygen production(NOP) was calculated using O_2/Ar ratio and O_2 concentration.The vertical mixing effect in NOP was calibrated via a N_2O based approach.GOP for autumn and spring was(169±23) mmol/(m~2·d)(by O_2) and(189±26) mmol/(m~2·d)(by O_2),respectively.While NOP was 1.5 mmol/(m~2·d)(by O_2) in autumn and 8.2 mmol/(m~2·d)(by O_2) in spring.Application of mixed layer depth history in the gas flux parametrization reduced up to 9.5% error in the GOP and NOP estimations.A comparison with an independent O_2 budget calculation in the diel observation indicated a26% overestimation in the current GOP,likely due to the vertical mixing effect.Both GOP and NOP in June were higher than those in October.Potential explanations for this include the occurrence of an eddy process in June,which may have exerted a submesoscale upwelling at the sampling station,and also the markedly higher terrestrial impact in June.  相似文献   

Planetary core size: A seismological approach     

Martin Knapmeyer 《Planetary and Space Science》2011,59(10):1062-1068

A key parameter for understanding the geodynamics of a terrestrial planet is the size of its core. Numerical evaluation of 28 different interior structure models of Mercury, Venus, Earth, the Moon, and Mars suggests that there is an almost linear relationship between the core radius and the extent of the seismic P-wave core shadow. A scaling law is derived from a simple mantle density and velocity model that permits the interpretation of respective seismic measurements on terrestrial planetary bodies.  相似文献   

长江水下三角洲沉积物柱状样重金属垂向分布特征   总被引：6，自引：1，他引：5  

李亚南  高抒 《海洋通报》2012,31(2):154-163

对长江水下三角洲3个沉积物柱状样进行粒度分析、²¹⁰Pb测年,并测定其中Cr、Cu、Pb、Zn等重金属元素和Al等常量元素的含量,得到了沉积物粒度、粘土含量、重金属含量的垂向分布曲线和沉积物测年数据。通过相关分析来研究沉积物中的Cr、Cu、Pb、Zn等重金属、粒度、Al相互之间的关系;以Al为参照元素对这4种重金属进行归一化处理,分析其归一化前后的垂向分布特征。结果表明,Cr、Cu、Pb、Zn 4种重金属元素在此区域的地球化学行为相似,其分布受细颗粒沉积物的吸附和胶体的絮凝作用共同控制;近一二十年来,该区域的Cr、Cu、Pb含量并没有显著增加,Zn有轻微污染。此外,CJ19柱中Cu存在异常峰值,可能是特大风暴潮事件对研究区浅水区底质沉积物中重金属的分布造成的影响。  相似文献   

基于Ls-Dyna的高能射流式冲击器活塞杆回程应力分析     

王福平  李鹏  李国琳  彭枧明 《吉林大学学报(地球科学版)》2016,46(5):1482-1489

针对在钻探实践中高能射流式冲击器的活塞杆频繁出现尾部塑性变形严重影响冲击器工作性能和整体寿命的现象,拟对活塞杆进行优化改进。利用非线性动力学仿真软件Ls-Dyna对活塞杆的回程撞击缸体进行数值模拟和优化分析,并进行了室内试验,结果表明：冲击末速度为4 m/s,活塞杆回程撞击缸体强制停止运动瞬间,尾部产生的应力集中值为3 339.28 MPa,导致其破坏;优化改进后,活塞杆上下端直径比为17/16、尾部圆弧直径为60 mm,活塞杆体内的应力集中值为1 419.66 MPa,较改进前活塞杆的应力集中值减小58%。试验验证表明,优化后的活塞能大幅提高使用寿命和耐久性。  相似文献   

CJ-130型双向气动潜孔锤的研制          下载免费PDF全文

马利东  隆威  苏冬九 《探矿工程》2009,36(1):31-33

针对以往锚固孔钻机在滑坡地层极易引起卡钻事故,无法退出而报废的问题,研制了一种可进行双向冲击的气动潜孔锤。介绍了该潜孔锤的性能参数、工作原理及结构组成,并结合其能够进行双向冲击的结构特点,阐明了该气动潜孔锤的设计思路,同时对虚拟样机进行了性能校核计算,验证了该设备的可行性。经现场使用,效果良好。  相似文献   

TK-1型压入活塞式取样器运动阻力计算及海上取样试验     

吴秋云  赵尔信 《探矿工程》2012,39(6):16-19

在海上采用压入活塞取样器取砂、土样在国内尚属首次。经过对取样器进行科学的模拟计算,获得了取样器运动阻力和压入地层所需的压力,试验表明,这些数据符合海上取样的实际情况。所设计的密封装置、翻板取样器及PC取样管等满足了海上取样要求。  相似文献   

Stratigraphy of multiple piston-core sediments for the last 30,000 years from Lake Biwa, Japan     

Keiji Takemura  Akira Hayashida  Makoto Okamura  Hiromi Matsuoka  Mohammed Ali  Mohammed Ali  Yoshiki Kuniko  Masayuki Torii  Masayuki Torii 《Journal of Paleolimnology》2000,23(2):185-199

  相似文献   

Influence of late holocene pyroclastic eruptions on the sedimentary geochemistry of Lake Rotoiti,North Island,New Zealand     

R. A. Pickrill  C. S. Nelson  P. Stoffers  G. G. P. Craig 《Journal of Paleolimnology》1991,6(3):173-192

Lake Rotoiti in Taupo Volcanic Zone was formed by damming of the drainage system through the floor of Okataina Caldera. Basin sediments are predominantly silt or sand, with mineralogy consistent with derivation from local silicic rocks and airfall tephras. Sandy lithofacies around the shoreline are wave worked deposits. Sand and gravel lithofacies in deeper water and on steep slopes are largely relict or airfall tephras, or both. Profundal sediments are diatomaceous silts. Organic-rich diatomaceous silts also accumulate in near-shore wave-damped zones under weed beds.Short cores penetrated the Tarawera (1886 AD) and Kaharoa (1180 AD) Tephras, identified by their stratigraphic position, geochemistry and mineralogy. Localised slumping is evidenced from secondary tephras interbedded and redeposited within the basin silts. Sedimentation rates in the basins, estimated from the age of bounding tephras, are 0.9 to 4.0 mm y^-1, and are highest under the influence of inflowing water from adjacent Lake Rotorua. For several hundred years prior to the Tarawera eruption sediment accumulation rates and the sediment geochemistry remained unchanged; deposition was predominantly biogenic opaline silica with a small terrestrial component. The Tarawera eruption deposited a terrestrial-silica, aluminum-rich primary tephra across the lake, which was followed by reworked tephra from within the catchment, the effects of which were progressively diluted by biogenic opaline silica as conditions stabilised. While the major effects of the eruption have been rapidly absorbed the lake has not returned to pre-eruption background conditions. A new equilibrium has been attained in which Tarawera Tephra continues to be eroded into the lake and is the principal source for a doubling of sedimentation rates following the eruption. High arsenic levels in some diatomaceous silts are attributed to episodic venting of hydrothermal fluids or gases into the water column.  相似文献   

Retention of mercury in sediments of the Baltic Sea near Oulu,Finland     

Kimmo Tolonen  Erkki Alasaarela  Anita Liehu 《Journal of Paleolimnology》1988,1(2):133-140

Several cores were compared to elucidate the grade of mercury retention in sediments of the Baltic Sea near Oulu, Finland. The known history of the mercury discharge to waste water from a chlor-alkali plant, the primary pollution source, was compared to that in the sedimentary record. One core was dated by lead-210 and varve counts. During the past thirty years, the rate of sedimentation was up to 10 mm per year corresponding to a dry matter accumulation rate of about 3 kg m^–2a^–1. Under these conditions, most of the mercury reaching the sediment was retained. Correspondingly, the mercury levels in fish were considerably lower, with a delay of some five years.The present mercury content of the upper layers is some 1/4 or 1/5 that of the late 1970's, but it is still some twentyfold compared to levels at the beginning of the century. The extent to which the present mercury level in the sediment represents the various phases of industrial emission remains unsolved due to the origin of mercury in this sea area from several other sources and due to difficulties in exact core correlations from different years.  相似文献