Holocene development and anthropogenic disturbance of a shallow lake system in Central Ireland recorded by diatoms     

K. A. Selby  A. G. Brown 《Journal of Paleolimnology》2007,38(3):419-440

Three cores from two connected lakes in Central Ireland (Lough Kinale and Derragh Lough) were investigated using diatom analysis to establish the Holocene development of the lacustrine system, any local variations within the lakes and any anthropogenic influences. The study area was situated in a lowland location and the lakes were shallow, unstratified and interconnected. Litho-and bio-stratigraphical analyses of the lake cores and deposits beneath a mire separating the two lakes showed the changing spatial configuration of the lake system in the early Holocene and the separation of the initial lake into three basins (cf. lacustrine cells) and finally into two interlinked lakes. The evolution of the lake system is conceptualised as the development of distinct lacustrine cells, and its sediments have recorded changes in the physical (geography, depth and sedimentation) and chemical (water chemistry) properties of the lakes inferred through diatom analyses. The longest sequence, from the early Holocene, records fluctuating lake levels and these are correlated with geomorphological mapping and surveying of palaeoshorelines. The diatom assemblages of the upper 2 m of the three cores, covering approximately the last 2000–3000 radiocarbon years show considerable difference in trophic status and life-form categories. This is related to the location of the cores in the lake and also the distance from human settlement with particular reference to proximity to crannog (artificial island) construction and use. The most central core from the deepest part of Lough Kinale has the least representation of the human settlement and agricultural activity in the catchment and on the fringes of the lake, whereas the core taken from the edge of a crannog is able to identify when construction and use of the crannog occurred. The local nature of the palaeoecological response to human activity due to incomplete water mixing has the advantage of allowing the lake sediment cores to be used to determine spatially discrete settlement patterns.  相似文献   

国内氢氧化镁阻燃剂的研究现状   总被引：6，自引：0，他引：6       下载免费PDF全文

姬连敏  李丽娟  聂锋  曾忠民 《盐湖研究》2007,15(2):62-72

综述了国内氢氧化镁阻燃剂的合成、表面改性及其应用,主要论述了近20年来国内在氢氧化镁阻燃剂研发方面取得的成果及发展方向,简单概述氢氧化镁阻燃剂的发展前景。  相似文献   

垃圾填埋场动力稳定机理及稳定分析研究现状与进展     

邓学晶  孔宪京 《世界地震工程》2007,23(4):59-65

简述国内外在垃圾填埋场动力稳定机理及稳定分析方面的研究现状与最新进展，包括：1．垃圾土（MSW）与接触面的属性参数；2．垃圾土的本构模型；3．填埋场动力分析方法。  相似文献   

“华北型”煤田岩溶水害及防治现状   总被引：5，自引：1，他引：5       下载免费PDF全文

卜昌森  张希诚等 《地质论评》2001,47(4):405-410

“华北型”煤田的开采普遍受到煤层底板岩溶承压水的威胁，近年来，煤田岩溶水害的机理研究取得突破性进展，认为岩溶裂隙水网络是发生突水的物质基础，隔水层的岩石水学性质及厚度是突水的制约因素，断裂构造是突水的关键因素，采矿活动是突水的诱发因素；在水害防治方面，采用疏水降压、注浆改造、帷幕截流等技术方法，取得了明显的技术效果，本文旨在介绍水害现状，分析探讨治理对策，为治理煤田水害提供参考。  相似文献   

藏北高原土地沙漠化现状及其驱动机制   总被引：21，自引：0，他引：21  

董玉祥 《山地学报》2001,19(5):385-391

作为青藏高原主体的藏北高原是我国土地沙漠化三大分布区之－－青藏高原分布区的代表性地域，是研究现代土地沙漠化过程及其形成机制的重要地区。本文从沙漠化土地的类型、面积与分布等方面详细分析了藏北高原土地沙漠化的现状，定性与定量分析相结合探讨了该区现代沙漠化过程的主要影响因子及其驱动机制。研究结果表明，藏北高原是我国重要的沙漠化土地分布区、沙漠化土地面积大、类型多、程度重、分布广、危害重，其形成与发展是自然因素与人为因素、自然过程与人为过程共同作用的结果，其中气候变化是其主要驱动力。  相似文献   

西南地区山地不同土地退化类型特征及调控途径   总被引：4，自引：7，他引：4  

张建平 《地理科学》2001,21(3):236-241

土地退化不仅是目前全还需性的重大环境问题之一，而且也是重大的社会和经济问题之一，西南地区的土地退化是以水力侵蚀为主要动力形成的，文中简述了西南地区的土地退化状况，选择了4个（楚雄市、遂宁市，毕节地区及元谋县）山地不同土地退化类型进行分析，讨论了土 退化过程，提出了土地退化调控途径。  相似文献   

Model of rigid and elastic-plastic motion in intraplate blocks and strain status of principal blocks in Chinese mainland   总被引：5，自引：1，他引：5  

李延兴  黄珹  胡新康  帅平  胡小工  张中伏 《地震学报(英文版)》2001,14(6):603-610

Introduction The Chinese mainland is located in the southeastern part of Eurasia plate and encircled by India, Eurasia, Pacific and Philippine Sea plates. It is one of areas with the strongest tectonic de-formation, especially Qingzang (QinghaiXizang) plateau and NS tectonic zone where the tec-tonic activity is more intensive and intricate. The main part of tectonic activity of Chinese mainland includes a series of tectonic zones and active blocks divided by them. Therefore, the research…  相似文献   

川滇强震的回归—马尔可夫链联合预测     

张启明 《四川地震》1993,(1):40-43

本文应用回归—马尔可夫链联合预测地震的方法,结合川、滇强震的特点,对川、滇强震进行了计算,并作了预测验证。结果表明,该方法对川、滇强震的预测效果较好。  相似文献   

Environmental history of an urban lake: a palaeolimnological study of Lake Jyväsjärvi, Finland     

Jarmo J. Meriläinen  Juhani Hynynen  Arja Palomäki  Keijo Mäntykoski  Allan Witick 《Journal of Paleolimnology》2003,30(4):387-406

Sedimentary diatom frustules and chironomid remains, in addition to the chemical stratigraphy of 32 elements and organic pollutants such as resin acids, PCB, DDT and its metabolites, were studied from core samples taken from Lake Jyväsjärvi in Central Finland (64° 14 N, 25° 47 E). The sediment profile covered over 200 years, with the oldest samples representing a period of very low human interference. The town of Jyväskylä was established on the lake shore in 1837, and the lake received untreated municipal wastewater from the town up until, 1977. A paper mill started operations in 1872 and began discharging effluent into Lake Jyväsjärvi. In recent years this effluent loading has been reduced. Based on the biological and chemical properties of the sediment strata, five developmental phases were distinguished and named as follows: (1) a pre-industrial phase (approximately up until the 1860s); (2) a phase of early changes in the lake ecosystem (from the 1870s to ca. 1940s); (3) a phase of increasing eutrophication (from ca. 1950 to ca. 1965); (4) a phase of severe pollution (from ca. 1966 to the early-1990s); and (5) a phase of recovery, which proceeded more quickly during the late-1990s following long-term hypolimnetic aeration. It was estimated that the ecological status of the lake changed from good to moderate during the second phase. Due to the poor chemical status of the lake (including increased concentrations of harmful substances) and the pronounced changes in diatom and chironomid communities, the ecological status from 1950 to the early-1990s was classified as bad. The present ecological status, after a slow recovery of about 20 years, can be classified as moderate/poor. Chemical analysis of the sediment revealed that some elements (C, N, P, S, Ba, Cd, Cu, Fe, Pb, Ni and Zn) followed the known history of municipal waste water discharge into the lake, but Hg, Cr and persistent organic pollutants had different stratigraphies, and therefore mainly originated from other sources. Pronounced changes in profundal benthic communities (chironomids) started about 80 years later than those in diatoms, but later changes in chironomid assemblages were greater than those in diatoms.  相似文献   

枇杷的不同器官中元素地球化学特征     

王徽  范辉  张勤 《物探与化探》2006,30(4):354-356,360

枇杷是药用价值很高的一种经济水果。研究不同母岩类型产区的枇杷中元素的地球化学特征,发现同一品种枇杷中元素的富集部位各不相同;而不同品种的枇杷所富集的元素种类大致相同,只是富集程度有差异。有益、营养元素在叶片中的含量大多高于其他部位;有害元素不超标。与枇杷果关系较为密切的营养元素主要为N、P、K、Ca、Mg;微量营养元素为B、Zn、Cu。  相似文献