Responses of primary productivity to current and climate changes in the mud area to the southwest of Cheju Island during the past 800 years

The biogenic silica (BSi), total organic carbon (TOC), total nitrogen (TN) and grain size were analyzed with a gravity core (3250-6) collected from the mud area in the north East China Sea. The average deposition rate of the upper core was about 0.078 cm yr^?1 based on the results of ²¹⁰Pb_ex. The mean grain size increased with depth in general. The frequency distribution of grain size showed that two marked changes of deposition environment occurred at 30 cm and 50 cm depths (about 1550 AD and 1300 AD, respectively). The variations of BSi and TOC indicated two distinct major periods of primary productivity over the past 800 years: a stage of low primary productivity corresponding to weak upwelling and low nutrient input below 30 cm depth (about 1200–1550 AD), and a stage of high primary productivity with strong currents and upwelling above 30 cm depth (about 1550–1950 AD). The stage with high primary productive appeared to be due to the northward-expanded muddy area caused by strong Asian Winter Monsoon and enhanced Yellow Sea Warm Current in winter. In conclusion, the BSi and TOC in the muddy sediments, the symbols of marine primary productivity, can be then used to investigate the evolution history of currents and relative climate change in the offshore areas.     

基于COSMIC掩星探测资料的云底高反演研究

本文基于相对湿度廓线进入云层时的突变实现云底高反演的思想,采用2008年11月至2009年1月的COSMIC掩星湿空气数据反演全球云底高度,并与探空资料反演结果进行对比分析,得出以下重要结论:(1)当温度－40 ℃相似文献   

青藏高原东南缘地震活动与地壳运动所反映的块体特征及其动力来源

通过分析青藏高原东南缘活动断裂带的活动特征和GPS资料显示的现今地壳形变场,辅以历史地震及地表破裂、震源机制解类型等资料,将青藏高原东南缘地区分成了11个次级块体.其中包括了西秦岭次级块体、阿坝次级块体、龙门山次级块体、藏东次级块体、雅江次级块体,香格里拉次级块体、滇中次级块体、保山次级块体、景谷次级块体、勐腊次级块体和西盟次级块体;并利用这些次级块体内的GPS站点速率计算出了这些块体现今运动情况及各块体之间断裂的滑动速率,分析认为各次级块体均受到了一种来自其相邻块体的主要应力作用而发生了旋转,其中保山次级块体、藏东次级块体、雅江次级块体、香格里拉次级块体、滇中次级块体的旋转尤为显著;同样,相邻块体之间的边界断裂带也呈现了相应的挤压或拉张活动特征,而藏东次级块体与雅江次级块体、雅江次级块体与滇中次级块体之间的挤压最为明显.利用上述结果,本文讨论了该地区的现今地壳形变特征,认为刚性块体的挤出作用与重力滑塌作用并存于该区域内,下地壳"管道流"的拖曳作用是该地区刚性块体挤出作用和重力滑塌的主要原因, 另外缅甸板块相对于自身的逆时针旋转作用在其北部引起的拉张作用也是重要因素之一.     

应用三分量浅层地震反射方法探测隐伏活动断裂

多波多分量地震勘探方法在油气田勘探开发中日益受到重视,但在工程和活动断裂探测中过去还没有开展多波多分量地震勘探的先例.本文简要介绍了在北京黄庄—高丽营断裂上开展的三分量浅层地震反射试验数据采集和资料处理方法,以及取得的初步结果.试验结果表明,采用纵波震源或横波震源激发、三分量接收的浅层地震勘探方法,可获得较高信噪比的浅层地震纵波、横波和转换波剖面,特别是水平分量采集的横波和转换波可提供很有意义的地下结构和构造信息.综合利用纵波、横波和转换波剖面特征进行的地质分层和断层解释结果取得了与跨断层的钻孔联合地质剖面结果较好的一致性.     

Distribution and sources of polycyclic aromatic hydrocarbons (PAHs) in sediments from Zhanjiang Bay and Leizhou Bay, South China

The concentrations and spatial distribution of polycyclic aromatic hydrocarbons have been investigated in two adjacent bays of Zhanjiang and Leizhou, China. The total concentrations of the 16 USEPA priority PAHs were ranged from 41.96 to 933.90ng/g dry weight with an average concentration of 315.98ng/g and ranged from 21.72 to 319.61ng/g with an average concentration of 103.91ng/g in Zhanjiang and Leizhou Bays, respectively. The spatial distribution of PAHs was site-specific and appeared to be somewhat positively correlated with TOC and negatively correlated with sediment grain size in the two bays. The values of Phe/Ant, BaA/228 and InP/276 were higher than 10, less than 0.2, and from 0.2 to 0.5, respectively, indicating that the sources of PAHs in the two bays were mainly from petroleum and its combustion, which predominantly originated from those ships and boats coming and going in the two bays.     

Distributions and removal fluxes of trace metals in the water column of the Hung-Tsai Trough off southwestern Taiwan

Vertical profiles of dissolved and particulate Mn, Fe, Ni, Cu, Zn, Cd, Pb, and (234)Th were determined in the Hung-Tsai Trough off southwestern Taiwan during 19-23 November, 2004. Except in the case of Cd, the distribution coefficient (K(d)) of the trace elements showed a negative correlation with the suspended particle concentration. Based on the average K(d) values, the general sequence of particle affinities for the eight trace elements is, from highest to lowest, Fe>Mn≈Pb>Zn≈Th>Cd≈Cu≈Ni. The trace metal data was coupled with the particle removal flux estimated from (234)Th/(238)U disequilibrium to investigate metal removal by particle sinking from the euphotic layer. The residence time of trace elements with respect to particle removal from the euphotic layer was estimated. A negative correlation between the residence time and the distribution coefficient for the trace metals was found.     

军队参与国际重大自然灾害救援行动工作机制建设的思考

向遭受严重自然灾害的国家或地区提供人道主义紧急支援,是各国军队在和平时期的重要使命。目前中国军队还没有成建制地出国参加过重大自然灾害的国际救援。本文介绍了联合国重大自然灾害国际救援行动协调工作机制、联合国框架下的军队资源参与灾害救援的工作机制。结合印尼地震海啸、海地地震等灾害中各国军队救援的情况,对我国军队将来参与国际重大自然灾害救援,在法律、预案和工作机制准备方面进行了分析,并提出了建议。     

单一均质土覆盖层厚度对地表峰值加速度和反应谱平台值的影响

选择粘土、粉土、砂土、砾石4类土场地构造了140个单一均质土剖面,输入峰值分别为50、100、150、200、300 Gal的各3条人工合成地震动时程,使用一维等效线性波动法,进行了土层地表地震反应计算,并对计算得到的地表峰值加速度和反应谱平台值做了统计分析和讨论.结果表明:不同土类地表峰值加速度和反应谱平台值随覆盖层增大达到最大值的厚度不同;不同幅值的基底输入,不同土类的覆盖层情况下,地表峰值加速度相对于基岩值加速度的放大倍数并不具有规律性,同是Ⅱ类场地,中软和中硬场地土条件下放大倍数的差异也是明显的.     

内蒙古锡林浩特I型花岗岩的时代及构造意义

在内蒙古锡林浩特水库地区出露的花岗岩确定为I型花岗岩,具有较高的Cr、Co、Ni丰度。Ca、Al含量和N2O／K2O比值较高,Fe、Mg含量较低。微量元素蛛网图中显示出明显的Nb、Ta、P、Ti负异常。在SiO2-K2O及AFM图中,花岗质岩石投在钙碱性系列区;在构造环境判别图中,花岗质岩石样品都投在火山弧＋同碰撞花岗岩区。锆石测年结果显示平均年龄为317．0±4．0Ma,属晚石炭世。这套晚石炭世岛弧花岗岩的存在,表明加里东期古亚洲洋并未完全关闭,晚石炭世时仍然存在洋壳的俯冲消减事件。从区域上看,是北侧的贺根山洋盆向南俯冲的结果。     

Dynamic performance analysis of a seismically isolated bridge under braking force

In order to study the dynamic performance of seismically isolated bridges under the most unfavorable loads in the longitudinal direction,a dynamic equation for vehicle braking in the longitudinal direction is established.A four or fiveorder Runge-Kutta method is adopted to obtain the time-history response of a wheel set under braking force.The quadratic discretization method is then used to transform this time-history into a braking and bending force time-history of a structural fixed node,and a dynamic response analysis of the seismically isolated bridge under the vehicle’s braking force is carried out using ANSYS,a universal finite element analysis software.According to the results,seismic isolation design results in a more rational distribution of braking force among piers;the influence of the initial braking velocity on the vehicle braking force is negligible;the location where the first wheel set leaves the bridge is the most unfavorable parking location;a seismic isolation bridge bearing constructed according to typical design methods enters into a yield stage under the braking force, while the shearing force at the bottom of the pier declines as the isolation period is extended;the design requirements can be met when the yield displacement of the seismic isolation bearing is less than 5 mm and the yield strength is greater than the braking force.