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441.
442.
沉积物磷原位钝化技术研究进展 总被引:1,自引:0,他引:1
水体磷含量是湖泊富营养化最主要的限制因子之一.伴随着湖泊流域工农业发展,外源污染物的长期输入致使沉积物中蓄积了大量的磷及其他污染物.湖泊沉积物一方面是水体磷重要的汇,但另一方面还是水体磷重要的源.在单纯控制湖泊外源污染条件下,沉积物磷的释放仍可导致水体持续富营养化,湖水水质得到明显改善通常需要数十年,因此控制湖泊沉积物内源污染释放是快速恢复湖泊水质必不可少的措施.沉积物内源污染控制技术包括生物修复、环保疏浚以及原位钝化技术.受水深等环境条件限制,生物修复技术和环保疏浚在深水、亚深水型湖泊难以实施.沉积物磷原位钝化技术具有生态、经济、快速和效果稳定等特点,在控制湖泊底泥内源污染中可望发挥重要作用,尤其适合于深水、亚深水型湖泊内源污染控制.系统阐述了不同沉积物原位钝化剂的钝化原理,对比分析了铝盐、铁盐、钙盐和粘度矿物作为磷钝化剂的优缺点和应用条件,概述了国内外沉积物原位钝化技术的应用现状,在此基础上提出了沉积物原位钝化技术未来的重点研究方向:一是研究发展新型钝化剂;二是因地制宜,探索适合不同类型湖泊的底泥原位钝化技术体系;三是加强底泥原位钝化技术与其他技术的联合应用研究与示范;四是加强钝化剂负面影响评价,建立科学的应用技术方案. 相似文献
443.
Yinhe Luo Jianghai Xia Yixian Xu Chong Zeng Richard D. Miller Qingsheng Liu 《Pure and Applied Geophysics》2009,166(3):353-374
Multichannel analysis of surface waves (MASW) method is a non-invasive geophysical technique that uses the dispersive characteristic
of Rayleigh waves to estimate a vertical shear (S)-wave velocity profile. A pseudo-2D S-wave velocity section is constructed
by aligning 1D S-wave velocity profiles at the midpoint of each receiver spread that are contoured using a spatial interpolation
scheme. The horizontal resolution of the section is therefore most influenced by the receiver spread length and the source
interval. Based on the assumption that a dipping-layer model can be regarded as stepped flat layers, high-resolution linear
Radon transform (LRT) has been proposed to image Rayleigh-wave dispersive energy and separate modes of Rayleigh waves from
a multichannel record. With the mode-separation technique, therefore, a dispersion curve that possesses satisfactory accuracy
can be calculated using a pair of consecutive traces within a mode-separated shot gather. In this study, using synthetic models
containing a dipping layer with a slope of 5, 10, 15, 20, or 30 degrees and a real-world example, we assess the ability of
using high-resolution LRT to image and separate fundamental-mode Rayleigh waves from raw surface-wave data and accuracy of
dispersion curves generated by a pair of consecutive traces within a mode-separated shot gather. Results of synthetic and
real-world examples demonstrate that a dipping interface with a slope smaller than 15 degrees can be successfully mapped by
separated fundamental waves using high-resolution LRT. 相似文献
444.
Introduction D’’ layer plays an important role in geodynamic process. And seismological research indicates that D’’ layer has large scale seismic anisotropy, however, most research concentrated on areas such as Northern Pacific, Central Pacific, Caribbean, Central America, Alaska etc. (Wookey et al, 2005; Garnero and Lay, 2003; Matzel et al, 1996; 相似文献
445.
GuoLiang Zhang ZhiGang Zeng XueBo Yin DaiGeng Chen XiaoYuan Wang XiaoMei Wang 《中国科学D辑(英文版)》2008,51(12):1786-1801
Thirty-six basalt samples from near East Pacific Rise 13°N are analyzed for major and trace elements. Different types of zoned plagioclase phenocrysts in basalts are also backscatter imaged, and major element profiles scanned and analyzed for microprobe. Basalts dredged from a restricted area have evolved to different extents (MgO=9.38wt%—6.76wt%). High MgO basalts are modeled for crystalliza-tion to MgO of about 7wt%, and resulted in the Ni contents (≈28 ppm) that are generally lower than that in observed basalts (>60 ppm). It suggests that low MgO basalts may have experienced more intensive magma mixing. High MgO (9.38wt%) basalt is modeled for self-"mixing-crystallization", and the high Ni contents in low MgO basalts can be generated in small scale and periodical self-mixing of new magma (high MgO). "Mixing-crystallization" processes that low MgO magmas experienced accord with recent 226Ra/230Th disequilibria studies for magma residence time, in which low MgO magmas have experi-enced more circles of "mixing-crystallization" in relatively longer residence time. Magma mixing is not homogeneous in magma chamber, however, low MgO magmas are closer to stable composition pro-duced by periodical "mixing-crystallization", which is also an important reason for magma diversity in East Pacific Rise. Zoned plagioclase phenocrysts can be divided into two types: with and without high An# cores, both of which have multiple reversed An# zones, suggesting periodical mixing of their host magmas. Cores of zoned plagioclase in low MgO (7.45wt%) basalt differ significantly with their mantle in An#, but are similar in An# with microlite cores (products of equilibrium crystallization) in high MgO (9.38wt%) basalt, which further shows that plagioclase phenocryst cores in low MgO basalts may have formed in their parental magmas before entering into the magma chamber. 相似文献
446.
海南省“十五”测震台网是集数字化、综合化、自动化技术为一体的大动态、宽频带地震观测系统,在地震速报、预报和地震科学研究中发挥重要的作用。本文通过对海南省测震台站故障情况的分析和总结,介绍地震台站维护的一些经验和方法。 相似文献
447.
448.
Real-time seismology for the 05/12/2008 Wenchuan earthquake of China: A retrospective view 总被引:2,自引:0,他引:2
Paul SOMMERVILLE 《中国科学D辑(英文版)》2009,52(2):155-165
The devastating 05/12/2008 Wenchuan earthquake (Mw7.9) in Sichuan Province of China showed very few precursory phenomena and occurred on a fault system once assigned to be
of moderate long term seismic risk. Given the existing coverage of seismograph stations in Sichuan Province, real-time seismology
could have been effective in avoiding some earthquake damage and helping post-earthquake emergency response. In a retrospective
view, we demonstrated that the epicenter can be located with 20 km accuracy using just two broadband stations with three-component,
which takes only about 10 s after the onset of the earthquake. Initial magnitude is estimated to be M7 with the Tc measurement
over first 4 seconds of P waves. Better magnitude estimate can be obtained within 2 min by modeling Pnl waves for stations
about 500 km away where the S waveforms are clipped. The rupture area is well revealed by teleseismically-recorded >M5 early
aftershocks within two hours after the mainshock. Within a few hours, teleseismic body waves were inverted to derive a more
detailed rupture process and the finite fault model can be readily used to calculate ground motions, thus providing vital
information for rescue efforts in the case where no real-time strong motion records are available.
Supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-116-1) and National Key
Technology Research and Development Program of China (Grant No. 2006BAC03B00) 相似文献
449.
450.
盆山沉积耦合原理在定量恢复造山带隆升剥蚀过程中的应用 总被引:4,自引:1,他引:3
造山带的隆升剥蚀过程研究一直是地学界研究的热点和难点,而与造山带毗邻的沉积盆地则真实地记录了造山带隆升剥蚀演化历史。因此,通过对沉积盆地中沉积物的研究可以反演山地隆升剥蚀历史。基于这种思路,介绍了两种定量恢复造山带隆升剥蚀的方法,即裂变径迹热年代学方法和质量平衡法。前者利用样品碎屑单颗粒的裂变径迹年龄的统计分析确定其源区,并量化源区的抬升剥露及热演化历史,但要求对样品的沉积时代有很好的年代学控制,沉积后样品没有遭受热重置。后者则假定在一定时间间隔内,盆山耦合系统中物源区的地形变化总和与沉积区的碎屑沉积质量总和成正比,即隆升过程中产生侵蚀总量与毗邻盆地的沉积总量之间质量守恒,从而通过研究盆地中相应时间段的沉积总量、沉积速度来定量恢复古地形,反演造山带的演化,但盆山系统的界定以及地层定年的精度直接影响到恢复造山带隆升剥蚀过程的可靠性。 相似文献