A cross-system analysis of sedimentary organic carbon in the mangrove ecosystems of Xuan Thuy National Park, Vietnam

A cross-system analysis of bulk sediment composition, total organic carbon (TOC), atomic C/N ratio, and carbon isotope composition (δ¹³C) in 82 surface sediment samples from natural and planted mangrove forests, bank and bottom of tidal creeks, tidal flat, and the subtidal habitat was conducted to examine the roles of mangroves in sedimentation and organic carbon (OC) accumulation processes, and to characterize sources of sedimentary OC of the mangrove ecosystem of Xuan Thuy National Park, Vietnam. Sediment grain sizes varied widely from 5.4 to 170.2 μm (mean 71.5 μm), with the fine sediment grain size fraction (< 63 μm) ranging from 11 to 99.3% (mean 72.5%). Bulk sediment composition suggested that mangroves play an important role in trapping fine sediments from river outflows and tidal water by the mechanisms of tidal current attenuation by vegetation and the ability of fine roots to bind sediments. The TOC content ranged from 0.08 to 2.18% (mean 0.78%), and was higher within mangrove forests compared to those of banks and bottoms of tidal creeks, tidal flat, and subtidal sediments. The sedimentary δ¹³C ranged from − 27.7 to − 20.4‰ (mean − 24.1‰), and mirrored the trend observed in TOC variation. The TOC and δ¹³C relationship showed that the factors of microbial remineralization and OC sources controlled the TOC pool of mangrove sediments. The comparison of δ¹³C and C/N ratio of sedimentary OC with those of mangrove and marine phytoplankton sources indicated that the sedimentary OC within mangrove forests and the subtidal habitat was mainly composed of mangrove and marine phytoplankton sources, respectively. The application of a simple mixing model showed that the mangrove contribution to sedimentary OC decreased as follows: natural mangrove forest > planted mangrove forest > tidal flat > creek bank > creek bottom > subtidal habitat.     

古尔班通古特沙漠南缘苔藓结皮中可培养真菌的多样性

为了解古尔班通古特沙漠南缘苔藓结皮中可培养真菌的多样性,运用稀释平板法和基于ITS-rDNA基因序列的系统发育分析,将得到的基因序列与NCBI数据库GenBank中的序列进行相似性比较并构建系统发育树。结果显示,从古尔班通古特沙漠南缘苔藓结皮中共分离得到24株菌落形态各异的真菌,分属于11属21种,绝大多数属于子囊菌亚门和半知菌亚门。其中,青霉属（Penicillium）和链格孢属（Alternaria）为优势菌群,茎点霉属（Phoma）、曲霉菌属（Aspergillus）、镰刀孢菌属（Fusarium）为常见属;有些种类的真菌具有耐热及特殊产酶活性。     

中国亚热带北界及其过渡带

本文根据亚热带热量指标构造了热量综合指数表达式,确定亚热带北界的具体位置、宽度和特征,分析过渡带内气候变量在时间上和空间上的内在联系。     

苏门答腊地震百年排名第四

美国地质勘探局测定2004年12月26日在印度尼西亚苏门答腊岛北端海岸几公里处发生的大地震为9．0级，这个震级在1900年以来世界发生的大型地震中排名并列第四。     

河北平原地下水开发中的问题及可持续利用

河北平原是我国严重缺水地区，但在地下水开发过程中，引起了多种环境问题，如地下水位持续下降；地下水位降落漏斗不断扩大，地下含水层疏干；地面发生沉降及出现地裂缝；海、咸水入侵等等。作者从水资源、环境和社会经济的特点出发，提出实现水资源和社会经济可持续发展的对策：全面实施节水战略，努力实现工业、农业、居民生活、生态环境的高效用水，逐步建立起节水型社会；提高城市污水资源化利用率；利用海水、咸水、减少淡水用量；实施跨流域调水；保护水资源和改善水环境是缓解河北平原缺水和环境问题的重要措施。     

不同性质降水发生前退偏振比的激光雷达探测

利用微脉冲偏振激光雷达对三次不同降水性质的云在降水发生前的退偏系数进行探测,对照分析同步观测的多普勒天气雷达垂直剖面图,结果表明激光雷达对云的退偏振比探测具有较高的可靠性,三次降水过程的退偏振比峰值随降水时间的逼近从高层逐步下降,退偏振比大于0.2的峰值一般出现在5 km以上的高层,2～6 km的退偏振比多维持在0.1～0.15之间,2 km以下退偏振比都小于0.1,且始终没有明显变化.     

在VB6.0环境下实现自动成柱状图

介绍了利用ADO技术访问数据库，同时对VB调用Windows API方面进行阐述。通过两者结合来实现钻孔自动成图，从而大大地提高野外工作效率。     

Shock responses of a surface ship subjected to noncontact underwater explosions

In combat operations, a warship can be subjected to air blast and underwater shock loading, which if detonated close to the ship can damage the vessel form a dished for hull plating or more serious holing of the hull. This investigation develops a procedure which couples the nonlinear finite element method with doubly asymptotic approximation method, and which considers the effects of transient dynamic, geometrical nonlinear, elastoplastic material behavior and fluid–structure interaction. This work addresses the problem of transient responses of a 2000-ton patrol-boat subjected to an underwater explosion. The KSF=0.8 is adopted to describe the shock severity. Additionally, the shock loading history along keel, the acceleration, velocity and displacement time histories are presented. Furthermore, the study elucidates the plastic zone spread phenomena and deformed diagram of the ship. Information on transient responses of the ship to underwater shock is useful in designing ship hulls so as to enhance their resistance to underwater shock damage.     

塔里木盆地西缘土壤碳氮垂直分布规律研究

棕漠土和灌淤土在塔里木盆地西缘洪积平原上广泛分布,文章选取这两种类型的土壤作为研究对象,测试分析了在不同的土壤层位有机碳和全氮的含量,探讨了有机碳和全氮含量、以及它们与粒级组之间的相关关系。研究结果表明:洪积平原两种土壤剖面在0～100cm层位上有机碳和全氮含量随着土壤层位深度的增加而降低,而在40～60cm层位上两种土壤的有机碳和全氮含量差值达到最大值,并且整个剖面上有机碳和全氮含量变化呈正相关的关系。