The application of δ¹³C and C/N ratios as indicators of organic carbon sources and paleoenvironmental change of the mangrove ecosystem from Ba Lat Estuary, Red River, Vietnam     

Nguyen Tai Tue  Hideki Hamaoka  Atsushi Sogabe  Tran Dang Quy  Mai Trong Nhuan  Koji Omori 《Environmental Earth Sciences》2011,64(5):1475-1486

In this study, two sediment cores (~70 cm) were collected from separate mangrove forests straddling the Ba Lat Estuary, Red River of northern Vietnam, to examine the origins of sedimentary organic carbon (SOC) and reconstruct the paleoenvironment. In addition, mangrove leaves and particulate organic matter were collected and measured for δ¹³C to trace the origins of SOC. The cores were analyzed by high-resolution sections for δ¹³C, TOC, C/N ratios, sediment grain size, water content, and porosity, with values of δ¹³C, TOC, and C/N ratios ranging from −28.19 to −22.5‰, 2.14–30.94 mg/g, and 10.29–18.32, respectively. The δ¹³C and TOC relationship indicated that there were some small residual effects of diagenetic processes on TOC and δ¹³C values in mangrove sediments. However, the shifts of δ¹³C and C/N ratios from the bottom to the surface sediment of the cores explained the change in organic matter sources, with values of C/N > 12 and δ¹³C < −25‰, and C/N < 12 and δ¹³C > −25‰ indicated terrestrial (e.g., mangrove litter) and marine phytoplankton sources, respectively. The covarying δ¹³C, C/N ratios, and sediment grain sizes during the past 100 years in sediment cores showed that the paleoenvironment may be reconstructed into three environments (subtidal, tidal flat, and intertidal mangrove). General trends in δ¹³C and C/N followed a gradual increase in the C/N ratio and a concomitant decrease in δ¹³C from the subtidal, through to tidal flat, and to the intertidal mangrove. δ¹³C and C/N ratios are therefore effective in measuring the continuum of environmental change in mangrove ecosystem.  相似文献   

老挝爬奔金矿构造地质特征与金矿的关系①     

张泰  刘运纪  周琳  梁立民 《矿产与地质》2013,(2)

爬奔金矿是近年来在老挝琅勃拉邦新发现的大型金矿床。研究表明该区有含铁碳酸岩型金矿和石英脉型金矿两种矿化类型,前者金矿体产在灰岩中,主要受NW-NNW向断裂构造蚀变带控制;后者金矿体产在韧性剪切带旁侧的次级平行断裂或片理化带中,受NE向韧脆性剪切带控制。矿床成因类型应属沉积-韧脆性剪切多期构造活动和热水溶液叠加改造型金矿床。  相似文献   

A bounding surface model for saturated and unsaturated soil-structure interfaces     

Chao Zhou  Pei Tai  Jian-Hua Yin 《国际地质力学数值与分析法杂志》2020,44(18):2412-2429

In many geotechnical systems, such as reinforced slopes and embankments, soil-structure interfaces are often unsaturated. Shear behaviour of unsaturated interfaces is strongly dependent on their matric suctions, as revealed by the results of extensive laboratory tests. So far, constitutive models for unsaturated interfaces are very limited in the literature. This paper reports a new bounding surface model for saturated and unsaturated interfaces. New formulations were developed to incorporate suction effects on the flow rule and plastic modulus. To examine the capability of the proposed model, it was applied to simulate suction- and stress-controlled direct shear tests on unsaturated soil–cement, soil–steel and soil–geotextile interfaces. Measured and computed results are well matched, demonstrating that the proposed model can well capture key features of the shear behaviour of unsaturated interfaces, including suction-dependent dilatancy, stress–strain relation and peak and critical state shear strengths.  相似文献   

九段沙湿地自然保护区执法模式初探     

孙瑛  张泰 《湿地科学与管理》2010,6(4):38-41

湿地执法管理是湿地保护的重要手段,探讨了九段沙湿地执法管理的3种模式:单一执法、联合执法、综合执法。根据九段沙湿地现状,认为综合执法是九段沙湿地保护和管理的最佳模式,它将为上海市的国际化生态城市的建设和经济的可持续发展起到积极作用。  相似文献   

滇池盆地东缘白邑-横冲断裂南段的浅层地震勘探研究   总被引：1，自引：0，他引：1  

胡毅力  温一波  段继平  太树刚  王刚  李建有  王朝进  杨江华 《震灾防御技术》2010,5(4):451-460

本文用浅层地震反射波法对可能穿越昆明新城区东部第四系覆盖区的白邑-横冲断裂南段进行了探测,结果表明:采用浅层地震反射波法探测隐伏断层是有效的,在滇池盆地东缘,白邑-横冲断裂南段东支在隐伏区存在,断面接近直立,视倾角约80°,具有高倾角张性正断性质,基岩垂直错距为10—13m,断裂规模由北向南减小;同时,没有发现西支次级断层存在迹象。据土层测龄结果,东支断裂最新活动时代为第四纪中更新世晚期。  相似文献   

城市游憩场点系统结构分形及优化——以苏州市区为例   总被引：4，自引：0，他引：4  

黄泰  保继刚  刘艳艳  王行风 《地理研究》2010,29(1):79-92

以苏州市区为例,采用Zipf分维数、空间关联维数以及交通长度－半径维数三个指标,分别对城市游憩场点系统的等级结构、空间结构及交通网络通达性进行分维刻画。研究发现:首先,苏州游憩场点系统及其交通道路支持系统都具有较好的分形特性;其次,各分维指标能够准确地刻画城市游憩场点系统及交通道路支持系统的结构分异,可以为游憩场点系统的结构优化提供标准依据并指明方向;其三,苏州游憩场点系统的等级结构和空间结构均呈现出一种核心松散、外围紧致的结构递变趋势,自组织能力的离心化现象比较突出;最后,从分形几何和系统论的角度揭示、证实了游憩场点系统和旅游景点系统在结构分形及自组织演化上存在着显著差异。  相似文献   

自重可压缩层状球体地球模型下地震变形算法的优化研究     

刘泰  唐河  佘雅文  付广裕  孟国杰 《地球物理学报》2022,65(4):1229-1239

本文利用龙格库塔法求解球坐标系下微分方程组,基于自重、可压缩和连续分层地球模型研究地震引起的地球变形,优化相关算法.首先对传统的两次同向积分法进行调整,对微分方程的齐次部分进行两次相向积分,分别由地心向上积分至震源和由地表向下积分至震源.接着利用震源间断条件求解震源上方和震源下方通解的组合系数,得到微分方程组的解矢量....  相似文献   

Comparison of Chemical Toxicity to Different Algal Species Based on Interspecies Correlation,Species Sensitivity,and Excess Toxicity          下载免费PDF全文

Xiao H. Wang  Yang Yu  Ling Fu  Hong W. Tai  Wei C. Qin  Li M. Su  Yuan H. Zhao 《洁净——土壤、空气、水》2016,44(7):803-808

  相似文献   

Shear-wave splitting in the crust: Regional compressive stress from polarizations of fast shear-waves          下载免费PDF全文

Yuan Gao  Yutao Shi  Jing Wu  Lingxue Tai 《地震科学（英文版）》2012,25(1):35-45

When propagating through anisotropic rocks in the crust, shear-waves split into faster and slower components with almost orthogonal polarizations. For nearly vertical propagation the polarization of fast shearwave (PFS) is parallel to both the strike of the cracks and the direction of maximum horizontal stress, therefore it is possible to use PFS to study stress in the crust. This study discusses several examples in which PFS is applied to deduce the compressive stress in North China, Longmenshan fault zone of east edge of Tibetan plateau and Yunnan zone of southeast edge of Tibetan plateau, also discusses temporal variations of PFS orientations of 1999 Xiuyan earthquake sequences of northeastern China. The results are consistent to those of other independent traditional stress measurements. There is a bridge between crustal PFS and the crustal principal compressive stress although there are many unclear disturbance sources. This study suggests the PFS results could be used to deduce regional and in situ principal compressive stress in the crust only if there are enough seismic stations and enough data. At least, PFS is a useful choice in the zone where there are a large number of dense seismic stations.  相似文献   

近50 a博斯腾湖逐年水量收支估算与水平衡分析   总被引：2，自引：0，他引：2       下载免费PDF全文

刘丽梅  赵景峰  张建平  彭文甫  范敬龙  张太西 《干旱区地理》2013,36(1):33-40

据博斯腾湖流域1958-2010年期间主要河流开都河、黄水沟、清水河、孔雀河的逐年流量资料,结合焉耆盆地降水、蒸发要素的同期观测资料,对大湖区的逐年水量收支进行计算,并依据水量平衡原理对博湖大湖区残差水量进行了逐年分析。结果表明：（1）1958-2010年期间年均入湖水量14.34×10⁸ m³/a,其中入湖河水约占95%;年均输出水量13.96×10⁸ m³/a,其中大湖区输入孔雀河水量约占43%,湖面蒸发耗水量占57%;湖区年均蓄水量71.57±3.92×10⁸ m³10⁸ m³/a,湖水年均水位为1 047.01±0.94 m;（2）极端水文年度水量平衡分析指出：1986年为最枯年份,入湖河水是多年平均值的62%,而出湖河水量是多年平均值的153%,导致年内湖区水位下降0.94 m;2002年最丰年份入湖河水是多年平均值的2.6倍,致使年内水位上升0.80 m;（3）残差水量逐年“正负”变化指出,湖水与地下水之间存在互补关系,过去53 a间湖水补给地下水的年均水量为0.87×10⁸ m³/a。  相似文献