Driving forces and management strategies for estuaries in northern China     

Anning Suo  Dongzhi Zhao  Fengshou Zhang  Huaru Wang  Fengqiao Liu 《Frontiers of Earth Science》2010,4(1):51-58

Estuaries, which lie at the end of rivers, belong to the interlocking area between marine ecosystems and terrestrial ecosystems. In the estuary region, there are plenty of biological resources that carry many important ecosystem services. However, severe degradation of the estuary ecosystem in northern China has been caused by anthropogenic disturbances, including water pollution from upstream area, change of marine environmental dynamics, animal habitat loss, and unreasonable exploitation in the estuary region. In order to provide scientific evidence for restoration and conservation of the estuary ecosystem, we collected data from published literature to analyze the ecological problems in several main estuary regions in northern China, such as the Yellow River estuary, Liaohe River estuary, Haihe River estuary, Yalu River estuary, and some others. The main ecological problems in the estuary region of northern China include the input decrease of fresh water from rivers, the change of the sediment input from rivers, the destruction of the estuary wetland ecosystem, the environmental pollution in the estuary region, the erosion in the estuary region, seawater encroachment, the biodiversity decline of the estuary region, and the depletion of the fish resources in the estuary region. Meanwhile, the driving forces for these ecological problems in the estuary region were also assessed. Based on the analysis of these driving forces, we propose several pieces of advice for integrated estuary management in northern China, including the creation of a management system for estuary conservation, improvement of the means and strength of the environmental law execution, increased investment on scientific research in the estuary ecosystem, improvement of public participation on the conservation for the estuary environment and biodiversity, and construction of a monitoring system for the estuary environment.  相似文献   

秦岭造山带根部地壳结构及流变学演化   总被引：9，自引：0，他引：9       下载免费PDF全文

索书田  游振东 《地球科学》1994,19(5):633-646

在地质和地球物理资料基础上，运用物理学观点，研究和分析了秦岭造山带根部－大别前寒武纪变质地体的三维结构及流变学演化历史，通过现代及中－新元古代时期地壳流变学剖面的构筑，强调地壳流变学分层性及变质变形分解作用对中下地壳结构及地球动力学演化的控制作用，线状强应变带与透镜状弱应变域的规律组合，是秦岭造山带及其根部地壳结构的基本样式，并具尺度不变性，将古老中下地壳近３Ｇａ的流变学演化历史划分为７个阶段。它  相似文献   

微板块与大板块：基本原理与范式转换     

李三忠  索艳慧  周洁  钟世华  孙国正  刘洁  王光增  朱俊江  姜素华  李玺瑶  郭晓玉  刘丽军  刘永江  曹现志  郭玲莉  赵淑娟  王鹏程  关庆彬  陈龙  刘勃然  周建平  姜兆霞  刘琳  曹花花  戴黎明  于胜尧  刘博  王秀娟  王程程  王玺  刘泽  管红香  李晓辉  胡军  段威  于雷  刘晓光  王誉桦  钟源  刘鹏  张文超  李洛阳  赵彦彦  许淑梅 《地质学报》2022,96(10):3541-3558

传统板块构造理论50多年来一直是占统治地位的地学理论，是理解固体地球运行的基本范式，但遇到三大难题：板块起源、板内变形和板块驱动力。针对这三大难题，微板块构造理论试图开拓一个全球构造研究的新范式。本文通过与传统板块构造理论中基本原理的逐条对比，阐明了微板块构造理论的基本原理和优势及其对传统板块构造理论的拓展。微板块构造范式既不同于传统板块构造范式，又不同于地幔柱范式，是两者的重要补充与拓展。文中着重从几何学、运动学、动力学、适用范围、理论出发点、理论假设与预测的角度，阐明了大板块与微板块的异同，并探讨了两者的转换关系及其转换机制的多样性，介绍了微板块生长成为大板块的4种途径、大〖JP2〗板块破碎为微板块的3种转换模式，探索了前板块构造体制下微地块在非线性地球系统中通过自组织、自生长等方式，进化为板块体制下微板块的自然选择过程。本文还提出陆壳型微地块是密度选择的结果，其密度决定了其保存机制，这是陆壳起源的根本；〖JP〗微地块向微板块的转变是刚性选择的结果，其刚性是初始板块构造体制起始的必要条件；微板块不对称俯冲或对流型式的转变是热选择的结果，其热不对称性是现代板块构造体制起始的必要条件。  相似文献   

The Electrical Conductivity of Gabbro at High Temperature and High Pressure     

王多君  李和平  易丽  张卫刚  刘丛强  苏根利  丁东业 《中国地球化学学报》2002,21(3):252-257

The electric conductivity of gabbro has been measured at 1.0 - 2.0 GPa and 320-700℃, and the conduction mechanism has been analyzed in terms of the impedance spectra.Experimental results indicated that the electric conductivity depends on the frequency of alternative current. Impedance arcs representing the conduction mechanism of grain interiors are displayed in the complex impedance plane, and the mechanism is dominated at high pressure.These arcs occur over the range of 102 - k× 105 Hz (k is the positive integer from 1 to 9). On the basis of our results and previous work, it is concluded that gabbro cannot form any high conductivity layer (HCL) in the middle-lower crust.  相似文献   

北京市经济增长与环境污染水平计量模型研究   总被引：171，自引：10，他引：171  

吴玉萍  董锁成  宋键峰 《地理研究》2002,21(2):239-246

选取北京市 1985～ 1999年经济与环境数据 ,通过分析经济因子与环境因子相互关系 ,探究北京市经济增长与环境质量演替轨迹 ,以建立北京市经济增长与环境污染水平计量模型 ,为评价北京市环境政策提供依据。实证研究表明 :北京市自 1985年以来随着经济增长其环境恶化程度在下降 ,且已进入经济与环境协调发展后期阶段。北京市各环境指标与人均GDP演替轨迹呈现显著的环境库兹涅茨曲线特征 ,但比发达国家较早实现了其环境库兹涅茨曲线转折点 ,且到达转折点的时间跨度小于发达国家。这主要归功于中国及北京市政府近 10年来 ,尤其 1995年以来有效环境政策和巨额环境投资以及科技后发优势。  相似文献   

大别—苏鲁区UHP变质岩构造学及流变学演化   总被引：1，自引：0，他引：1  

索书田  钟增球  周汉文  游振东 《地学前缘》2008,15(3):150-167

在大别—苏鲁区的30个关键位置,对UHP/HP变质岩进行详细构造解析、大比例尺(1∶10000)制图并在区域尺度上进行观察和对比,以便揭示它们的构造几何学、变形条件和流变学演化。初步的研究结果指出,广泛出露的UHP/HP榴辉岩相岩石形成一个巨大的UHP/HP变质带,提供了一个观察中朝与扬子克拉通之间三叠纪大陆深俯冲-碰撞带过程的窗口。观察的显微构造及组构指出,UHP/HP变质带内岩石变形机制,无论是在榴辉岩相阶段还是在榴辉岩相后阶段,都是以塑性流变为主,其力学行为和组构特征都受组成矿物的强度、强度差等流变学特征,以及变形物理环境如压力、温度、应变速率、差异应力和流体含量等的制约。在俯冲/碰撞带内的变形分解作用于岩石圈不同层次及不同的构造阶段都曾发生,而且,在不同尺度上,应变局部化形成具高应变的剪切带网络,且一般显示典型的布丁-基质或碎斑-基质构造及流变学型式。根据构造、岩石、变质作用及地质年代学资料,借助于岩石圈流变学基本原理,提出一个大别—苏鲁区UHP/HP变质岩石流变学演化的工作模式,它涉及早期扬子与中朝克拉通间三叠纪(~250~230Ma)大陆深俯冲/碰撞、UHP/HP变质岩形成,相继深埋岩石的多期折返。特别强调UHP/HP岩石向地壳表层的折返,主要是构造过程,地面侵蚀作用是次要的。  相似文献   

Monthly Changes in the Influence of the Arctic Oscillation on Surface Air Temperature over China     

黄嘉佑  谭本馗  所玲玲  胡永云 《大气科学进展》2007,24(5):799-807

Partial Least Squares Regression （PLSR） is used to study monthly changes in the influence of the Arctic Oscillation （AO） on spring, summer and autumn air temperature over China with the January 500 hPa geopotential height data from 1951 to 2004 and monthly temperature data from January to November at 160 stations in China. Several AO indices have been defined with the 500-hPa geopotential data and the index defined as the first principal component of the normalized geopotential data is best to be used to study the influence of the AO on SAT （surface air temperature） in China. There are three modes through which the AO in winter influences SAT in China. The influence of the AO on SAT in China changes monthly and is stronger in spring and summer than in autumn. The main influenced regions are Northeast China and the Changjiang River drainage area.  相似文献   

基于GIS的孔隙含水层系统三维空间离散方法研究     

贾锦生  陈锁忠 《江苏地质》2005,29(1):5-9

分析了目前孔隙地下水流三维有限差分数值模拟中对含水层系统三维空间离散存在的问题，针对自然界孔隙含水层与隔水层空间分布的不连续性与厚度的不均匀性，研究了基于GIS的孔隙含水层系统三维空间离散实现的技术路线，提出了基于GIS与不规则六面体元的孔隙含水层系统的三维空间离散方法，最大限度地保证了离散体元中含水层类型的单一性，提高了孔隙地下水流模拟模型三维空间离散的精度。  相似文献   

黄土高原生态脆弱贫困区生态经济发展模式研究——以甘肃省定西地区为例   总被引：20，自引：4，他引：16  

董锁成  吴玉萍  王海英 《地理研究》2003,22(5):590-600

本文对黄土高原丘陵沟壑区定西地区生态脆弱与贫困的双重矛盾进行了定性与定量相结合的分析,研究表明定西地区“脆弱-贫困”恶性循环是自然与人文要素长期作用的结果,近几十年又以人为因素的作用为主。在总结定西地区解放以来一手抓生态环境建设,一手抓扶贫攻坚,整体解决温饱的成功经验基础上,提出了黄土高原生态脆弱的贫困地区生态经济发展模式;实践证明,生态经济发展模式是黄土高原生态脆弱的贫困地区打破“脆弱-贫困”恶性循环,实现可持续发展的必由之路  相似文献   

Late Cretaceous basalts and rhyolites from Shimaoshan Group in eastern Fujian Province,SE China: age,petrogenesis, and tectonic implications     

Xi-Yao Li  Yan-Hui Suo  Li-Ming Dai  Ling-Li Guo  Feng-Jian Ge 《International Geology Review》2018,60(11-14):1721-1743

ABSTRACT

Southeastern China is characterized by an extensive Late Mesozoic (Yanshanian) tectono-magmatic-metallogenic event. Although Late Cretaceous volcanism gradually weakened during the epilogue of the Yanshanian event, its petrogenesis and geodynamic processes remain unclear. In this study, we present new zircon U–Pb–Hf isotopic, whole-rock elemental, and Sr–Nd isotopic compositions data, for volcanic rocks from the Zhaixia Formation of the Shimaoshan Group in Fujian Province. The lower member of the Zhaixia Formation consists of basalts and rhyolites, and the upper member is only rhyolites. These volcanic rocks erupted in the early stage of Late Cretaceous, with basalts erupting earlier (ca. 99–98 Ma) than rhyolites (ca. 98–94 Ma). These basalts record high-K calc-alkaline to shoshonitic, light rare earth element (LREE)- and LILE-enrichment, high field strength element (HFSE)depletion with negligible Eu anomalies, and uniform whole-rock ε_Nd(t) (–3 to –6) and zircon ε_Hf(t) (–3.3 to –14.1) values. The overlying rhyolites record peraluminous and high-K calc-alkaline characteristics, LREE- and LILE-enrichment with negative Eu anomalies, and Nb–Ta depletion. The whole-rock ε_Nd(t) and zircon ε_Hf(t) values of these rhyolites both increase from the lower member (ε_Nd(t), –1.5 to –4.7; ε_Hf(t), –5.1 to –16.1) to the upper member (ε_Nd(t), –0.5 to 0.1; ε_Hf(t), –0.3 to –4.3). The features imply that these basalts were derived from the partial melting of the enriched lithospheric mantle and the overlying rhyolites from the melting of the crustal components, respectively. Data from the rhyolites in the upper member indicate that more juvenile, Nd–Hf isotopically depleted materials were injected into their source. During the Late Cretaceous, the new, fast rollback of the subducting slab triggered lithospheric extension and asthenospheric upwelling beneath the coastal regions, which induced the melting of lithospheric mantle and crustal components. As continued, the new round of basaltic underplating provided necessary heat to cause partial melting of the deep crust, including the younger, juvenile, and isotopically depleted crustal components.  相似文献