Effects of river damming on biogenic silica turnover: implications for biogeochemical carbon and nutrient cycles     

Nan Ma  Zhaoliang Song  Baoli Wang  Fushun Wang  Xiaomin Yang  Xiaodong Zhang  Qian Hao  Yuntao Wu 《中国地球化学学报》2017,36(4):626-637

Rivers link terrestrial ecosystems and marine ecosystems, and they transport large amounts of substances into oceans each year, including several forms of silicon (Si), carbon (C), and other nutrients. However, river damming affects the water flow and biogeochemical cycles of Si, C, and other nutrients through biogeochemical interacting processes. In this review, we first summarize the current understanding of the effects of river damming on the processes of biogeochemical Si cycle, especially the source, composition, and recycling process of biogenic silica (BSi). Then, we introduce dam impacts on the cycles of C and some other nutrients. Dissolved silicon in rivers is mainly released from phytolith dissolution and silicate weathering. BSi in suspended matter or sediments in most rivers mainly consists of phytoliths and mainly originates from soil erosion. However, diatom growth and deposition in many reservoirs formed by river interception may significantly increase the contribution of diatom Si to total BSi, and thus significantly influence the biogeochemical Si, C, and nutrient cycles. Yet the turnover of phytoliths and diatoms in different rivers formed by river damming is still poorly quantified. Thus, they should be further investigated to enhance our understanding about the effects of river damming on global biogeochemical Si, C and nutrient cycles.  相似文献   

南海中西部地貌单元划分及其特征和成因分析   总被引：1，自引：0，他引：1  

祝嵩  姚永坚  罗伟东  徐子英  鞠东  刘胜旋 《地球学报》2017,38(6):897-909

南海中西部处于南海北部和南部的过渡带,夹持于印支地块和南海海底扩张中心之间,其特殊的地貌对于研究整个南海地质地貌有重要意义。本文基于广州海洋地质调查局在南海中西部海洋地质调查项目获取的水深、底质调查及地震剖面数据,结合该海域以往研究成果,提取了有关地貌的信息,编制了南海中西部地貌图。把研究区划分出陆架、陆坡和深海盆地三个二级地貌单元,以及水下岸坡、水下浅滩、海岭、峡谷、麻坑、阶地、盆地、海台、海山、深海扇、深海平原等众多次级地貌单元。文章详细描述了该海域各地貌单元的特征,提出了断层、火山、构造隆起和浊流等地质作用是本区地貌形成的主要因素。  相似文献   

浅层地震反射在郧西盆地断层探测中的应用与研究     

林松  罗登贵  李媛  周欣 《大地测量与地球动力学》2017,37(2):146-148

在前期详细地质调查的基础上,对郧西盆地进行针对性的浅层地震反射勘探,并利用地震发射结果来确定断层位置及构造特征。该研究对南水北调中线核心水源区地震安全系统的建设有一定意义。  相似文献   

台湾美浓M_W6.4地震InSAR形变场初步分析     

董景龙  沈强  汪汉胜  江利明  毛松 《大地测量与地球动力学》2017,37(9):893-897

利用欧洲航天局最新发射的宽刈幅、高分辨率Sentinel-1A卫星,第一时间获取2016-02-06台湾美浓MW6.4地震干涉像对,使用D-InSAR技术获取美浓地区的同震形变场。利用震中附近39个同震GPS观测进行对比验证后显示,InSAR获取的同震形变场精度优于1 cm（3σ）。形变发生在宏观震中30 km×30 km范围内,主要表现为沿雷达视线向抬升,最大抬升约12 cm。从形变场空间分布特征可以看出,空间连续性较好,说明宏观震中附近地表未发生明显破裂。宏观震中并不与震中位置重合,而是位于震中西部约15 km处。  相似文献   

利用SLR数据检核GLONASS卫星最终轨道     

杨红雷  加松  徐天河 《大地测量与地球动力学》2017,37(9):956-960

采用由EDC提供的2015-01-01～2015-12-31的SLR标准点观测数据进行GLONASS卫星最终轨道（CODE提供）检核,分别按照卫星PRN号和不同测站对检核结果进行统计分析。结果表明,不同卫星的检核效果参差不齐,跟卫星的服役年限有关,较新的卫星检核结果较好,第一轨道面的卫星检核结果最好;检核结果中存在一定的系统误差,且大部分的激光测距比最终轨道反算的站星距要短;利用SLR检核2015年全年GLONASS轨道精度总体优于3.3 cm,激光观测精度总体优于1.2 cm。  相似文献   

Effect of climate change on seasonal water use efficiency in subalpine <Emphasis Type="Italic">Abies fabri</Emphasis>     

Xiang-yang Sun  Gen-xu Wang  Mei Huang  Zhao-yong Hu  Chun-lin Song 《山地科学学报》2017,14(1):142-157

Abies fabri is a typical subalpine dark coniferous forest in southwestern China. Air temperature increases more at high elevation areas than that at low elevation areas in mountainous regions, and climate change ratio is also uneven in different seasons. Carbon gain and the response of water use efficiency (WUE) to annual and seasonal increases in temperature with or without CO₂ fertilization were simulated in Abies fabri using the atmospheric-vegetation interaction model (AVIM2). Four future climate scenarios (RCP2.6, RCP4.5, RCP6.0 and RCP8.5) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) were selectively investigated. The results showed that warmer temperatures have negative effects on gross primary production (GPP) and net primary production (NPP) in growing seasons and positive effects in dormant seasons due to the variation in the leaf area index. Warmer temperatures tend to generate lower canopy WUE and higher ecosystem WUE in Abies fabri. However, warmer temperature together with rising CO₂ concentrations significantly increase the GPP and NPP in both growing and dormant seasons and enhance WUE in annual and dormant seasons because of the higher leaf area index (LAI) and soil temperature. The comparison of the simulated results with and without CO₂ fertilization shows that CO₂ has the potential to partially alleviate the adverse effects of climate warming on carbon gain and WUE in subalpine coniferous forests.  相似文献   

Combined adaptive multiple subtraction based on optimized event tracing and extended wiener filtering     

Jun Tan  Peng Song  Jinshan Li  Lei Wang  Mengxuan Zhong  Xiaobo Zhang 《中国海洋大学学报(英文版)》2017,16(3):411-421

The surface-related multiple elimination (SRME) method is based on feedback formulation and has become one of the most preferred multiple suppression methods used. However, some differences are apparent between the predicted multiples and those in the source seismic records, which may result in conventional adaptive multiple subtraction methods being barely able to effectively suppress multiples in actual production. This paper introduces a combined adaptive multiple attenuation method based on the optimized event tracing technique and extended Wiener filtering. The method firstly uses multiple records predicted by SRME to generate a multiple velocity spectrum, then separates the original record to an approximate primary record and an approximate multiple record by applying the optimized event tracing method and short-time window FK filtering method. After applying the extended Wiener filtering method, residual multiples in the approximate primary record can then be eliminated and the damaged primary can be restored from the approximate multiple record. This method combines the advantages of multiple elimination based on the optimized event tracing method and the extended Wiener filtering technique. It is an ideal method for suppressing typical hyperbolic and other types of multiples, with the advantage of minimizing damage of the primary. Synthetic and field data tests show that this method produces better multiple elimination results than the traditional multi-channel Wiener filter method and is more suitable for multiple elimination in complicated geological areas.  相似文献   

A new record of ponyfish <Emphasis Type="Italic">Deveximentum megalolepis</Emphasis> (Perciformes: Leiognathidae) in Beibu Gulf of China     

Yuman Ju  Na Song  Guobao Chen  Dianrong Sun  Zhiqiang Han  Tianxiang Gao 《中国海洋大学学报(英文版)》2017,16(3):468-472

A new record ponyfish, Deveximentum megalolepis Mochizuki and Hayashi, 1989, was documented based on its morphological characteristics and DNA barcode. Fifty specimens were collected from Beibu Gulf of China and identified as D. megalolepis by morphological characterization. The coloration, meristic traits, and morphometric measurements were consistent with previously published records. In general, it is a silver-white, laterally compressed and deep bodied ponyfish with 6–9 rows of scales on cheek; scale rows above lateral line 6–8; scale rows below lateral line 14–17. Mitochondrial cytochrome oxidase I subunit (COI) gene fragment was sequenced for phylogenetic analysis. There is no sequence variation of COI gene between the specimens collected in this study. The genetic distances between D. megalolepis and other congeneric species range from 3.6% to 14.0%, which were greater than the threshold for fish species delimitation. The COI sequence analysis also supported the validity of D. megalolepis at genetic level. However, the genetic distance between Chinese and Philippine individuals was about 1.2% and they formed two lineages in gene tree, which may be caused by the geographical distance.  相似文献   

滑坡监测的自适应约束抗差滤波算法研究     

左廷英  吴芸芸  宋迎春 《大地测量与地球动力学》2011,31(6):94-99

在滑坡的动态监测中通常存在先验几何信息和物理信息,现有的滤波算法并不能够充分利用这些信息,为控制几何观测异常对形变参数估计的影响,提出一种利用滑坡力学状态信息的约束滤波模型.同时,利用约束方程获得有益信息,精确地确定测量的等价权,给出相应的自适应约束抗差滤波算法,并通过实例说明了带有约束的滤波算法更能提高状态参数估计的...  相似文献   

峨眉山超级地幔柱对四川盆地烃源岩热演化的影响   总被引：9，自引：1，他引：8       下载免费PDF全文

朱传庆  田云涛  徐明  饶松  袁玉松  赵永庆  胡圣标 《地球物理学报》2010,53(1):119-127

四川盆地的构造、热演化与峨眉山超级地幔柱有密切关系.峨眉山超级地幔柱对四川盆地中二叠统之下的烃源岩热演化有着十分重要的影响.在四川盆地热历史恢复的基础上,研究了峨眉山超级地幔柱对盆地内烃源岩,特别是中二叠统之下的古生界烃源岩热演化的影响.结果表明,中二叠统及下伏烃源岩的热演化受中晚二叠世发生在盆地西南方向的峨眉山超级地幔柱的影响巨大,且具地区差异性.即在靠近峨眉山地幔柱中心的地区,有机质迅速成熟并达到其成熟度的最高值(以H1井为代表),古生界烃源岩迅速进入过成熟,此后未有二次生烃;而远离峨眉山地幔柱的盆地大部分地区,古生界烃源岩在二叠纪以来具有多次生烃过程.中生界烃源岩热演化,主要和前陆盆地阶段的构造过程包括前陆沉积和断裂的逆冲推覆等相关. 在烃源岩有机质成熟度演化史的基础上,从盆地热史和烃源岩热演化的角度指出了下二叠统及之下烃源层在四川盆地不同地区油气勘探中的不同意义.  相似文献