Environmental impacts of dredging on seagrasses: a review

Main potential impacts on seagrasses from dredging and sand mining include physical removal and/or burial of vegetation and effects of increased turbidity and sedimentation. For seagrasses, the critical threshold for turbidity and sedimentation, as well as the duration that seagrasses can survive periods of high turbidity or excessive sedimentation vary greatly among species. Larger, slow-growing climax species with substantial carbohydrate reserves show greater resilience to such events than smaller opportunistic species, but the latter display much faster post-dredging recovery when water quality conditions return to their original state. A review of 45 case studies worldwide, accounting for a total loss of 21,023 ha of seagrass vegetation due to dredging, is indicative of the scale of the impact of dredging on seagrasses. In recent years, tighter control in the form of strict regulations, proper enforcement and monitoring, and mitigating measures together with proper impact assessment and development of new environmental dredging techniques help to prevent or minimize adverse impacts on seagrasses. Costs of such measures are difficult to estimate, but seem negligible in comparison with costs of seagrass restoration programmes, which are typically small-scale in approach and often have limited success. Copying of dredging criteria used in one geographic area to a dredging operation in another may in some cases lead to exaggerated limitations resulting in unnecessary costs and delays in dredging operations, or in other cases could prove damaging to seagrass ecosystems. Meaningful criteria to limit the extent and turbidity of dredging plumes and their effects will always require site-specific evaluations and should take into account the natural variability of local background turbidity.     

Raman microspectrometry of fluid inclusions

For many kinds of fluid inclusions, the coupling of microthermometry and Raman microspectrometry is still the only viable option to obtain compositions of single fluid inclusions. A review is given on the basis of 16 years of experience and helped with about 120 references of the instrumentation, analytical conditions and methodology of the application of Raman microspectrometry to gaseous, aqueous and hydrocarbon inclusions, and their daughter minerals.     

早期大陆与板块构造启动——前沿热点介绍与展望

板块构造的启动时间和机制,一直是国内外地球科学界关注的焦点,有不少热点文章对此进行了讨论。它涉及的不仅是早期地球的构造机制问题,更关系到整个地球的演化历史、变化过程和演化规律,以及地球的未来。本文对国内外的研究状况、研究重点进行了简单述评,强调地球的"热状态和热演化"是构造机制演化的关键控制因素,提出大陆形成和岩石圈的演化与板块构造起源关联密切,是理解早期板块构造启动的重要研究内容。华北克拉通是代表性的古老大陆,本文对它的研究状况给出了介绍和评述。文章最后展望了"早期大陆与板块构造启动"这一重要科学问题的研究方向,并对相应的研究方法提出了评论和建议性意见。     

我国地震地下流体科学40年探索历程回顾

通过回顾40年来中国大陆地震地下流体科学研究与实践的发展历程,总结了早期在该领域具启迪性的研究工作和主要成果。纵观历史,无论是观测技术和理论方法的创新,还是对各种参量的观测分析以及预测方法的研究,地震地下流体科学都与地震监测预报这一关键需求紧密相关。地下流体观测网建设的历史沿革表明,对强地震的监测与预测需求推进了观测网的建设和发展;观测技术的发展过程体现出基于多手段、综合性和数字化的趋势;地下流体理论与前兆机理的研究成果表明,前兆模型(或模式)、数值模拟、室内和野外实验研究等是推进学科创新工作的主要技术途径;地震预测方法的研究成果体现出探索基于具有物理基础的预报技术,以及重视实用性与科学性相统一的思想;预测实践证明,地下流体学科在我国大陆地震预测实践中发挥着重要作用。文章最后介绍了本学科主要的论著及技术规范,简要回顾了不同的历史发展阶段、有关学术团体和专家对地下流体学科主要科学问题的认识以及该学科的重点发展方向。     

根据砾石风化圈厚度估算地貌年龄*

对砾石风化与时间关系的定量研究表明,二者关系是非线性的。实事上,由于风化残余物对风化过程的抑制作用,大部分砾石的风化速率随时间减小,有的与时间呈指数关系,这样,便可以根据砾石风化圈厚度估算地貌年龄。该方法自六十年代开始兴起,经过几十年的实践,已日趋成熟。近来我们在我国西部河西走廊中段进行了这方面研究。本文系统介绍了该方法的研究状况。     

卫星测高的发展与应用：兼评《卫星测高原理》专著出版

卫星测高是近三十年度发展起来的又一空间大地测量技术，它具有观测精度，周期短以及覆盖面广等一系列地面技术无法比拟的优点，引起各国科学院的高度重视。     

Using Grey System Theory for Earthquake Forecast

By combining conventional grey correlation analysis,grey clustering method and grey forecasting methods with our multi-goal forecast thoughts and the techniques of grey time series processing,we develop six different grey earthquake forecast models in this paper,Using the record of major earthquakes in Japan from 1872 to 1995,we forecast future earthquakes in Japan.We develop an earthquake forecast model.By using the major earthquakes in Japan from 1872 to 1984,we forecast earthquakes from 1985 to 1995 and check the precision of the grey earthquake models.We find that the grey system theory can be applied to earthquake forecast.We introduce the above analysis methods and give a real example to evaluate and forecast.We also further discuss the problems of how to improve the precision of earthquake forecast and how to strengthen the forecast models in future research.     

中国地震标准体系进展综述

中国地震标准体系由国家标准、行业标准、地方标准、团体标准和企业标准构成.目前,我国正在实施的地震标准共计756项,其中,国家标准129项,行业标准299项,地方标准160项,团体标准23项,企业标准145项.从技术角度分类,这些地震标准可以划分为地震基本概念与规定类、地震监(观)测类、建设工程抗震设防类、地震应急救援与...     

我国花岗岩研究的回顾与展望

本文中回顾了８０年代以来国内花岗岩研究的概况。阐述了造山带花岗岩的形成和演化,次火山花岗岩的特征,Ａ－型花岗岩的成因,花岗岩形成过程中的岩浆混合作用、玄武岩浆底侵作用与花岗岩形成的联系以及花岗岩的实验岩石学研究方面的问题。展望了下一世纪花岗岩研究的某些趋向。