Chemical structural units of macromolecular coal components     

Angela Jenisch  Hans Hermann Richnow  Walter Michaelis 《Organic Geochemistry》1990,16(4-6)

Chemical degradations of coal resins, coal asphaltenes and coal residues have been performed with selective, non-oxidative reagents. The coal comprise samples a rank interval 0.30–1.21 %R_m. Degraded low-molecular-weight compounds were analyzed by GC-MS. The distributions of pentacyclic terpanes, isoprenoids, n-alkanes, acids and alcohols obtained as degradation products illustrate a considerable variability between the macromolecular coal fractions. A structural study on the molecular level of the degraded compounds from coal resins and coal asphaltenes show their potential to generate hydrocarbons during coalification process.  相似文献   

澜沧江上游德钦县亚高山、高山草地群落类型及其特点   总被引：1，自引：0，他引：1  

包维楷  吴宁  和绍春  阿追  革玛江初  杨沛芳  忠永次里 《山地学报》2001,19(3):226-230

摘要：采用样方调查方法获得94个草地群落样方,对澜沧江上游德钦县亚高山、高山草地群落类型及其特点进行了初步分析。结果表明,该县亚高山、高山草地群落类型存在20个类型。在放牧干扰下,大多数群落类型处于退化状态,相互之间存在明显的群落替代关系;调查发现群落中每平方米内平均含8种草本植物,平均盖度62．4％,地上平均生物量是4859kg／hm^2,平均可食率为61．5％;鸢尾群落、牛旁群落和小狼毒群落是草地严重退化后形成的典型有毒害群落类型;长期的高强度放牧虽然增加了群落类型多样性,但减少了群落内物种多样性。总体而言,长期的放牧干扰降低了德钦草地的生物多样性的质量及其生态服务功能,导致草地生态系统的非持续发展。  相似文献   

Pastoralists’ perceptions and realities of vegetation change and browse consumption in the northern Kalahari, Namibia     

M. Katjiua  D. Ward   《Journal of Arid Environments》2007,69(4):716-730

Pastoral production around artificial watering points in semi-arid environments affects the density and composition of plant communities. In the Kalahari desert of southwestern Africa, bush encroachment is often regarded as the major form of land degradation resulting from pastoral production around watering points. We investigated the OvaHerero pastoralists’ perceptions of the extent of vegetation change since the establishment of artificial watering points in the northern Kalahari desert of Namibia, and related this to ecological data on vegetation change. We determined the utility of woody vegetation to pastoralists’ livelihoods in terms of provision of construction material, fuel wood and browse. We quantified local knowledge of cattle browse consumption and correlated this with field data. We also assessed the purposes for which major livestock types were used. Our results showed that: (1) pastoral knowledge of bush encroachment and browse consumption was consistent with concurrently collected field data, (2) the current level of bush encroachment was perceived to be beneficial for pastoral production, and (3) cattle played an important role in the production of milk and milk by-products for domestic use, and served as a source of cash income, while sheep and goats were primarily kept for meat consumption. This result contrasts with historical studies that mainly portray cattle as a symbol of social status among OvaHerero pastoralists.  相似文献   

干酪根化学降解产物的碳同位素组成研究     

王涌泉  熊永强  王彦美 《沉积学报》2007,25(5):778-781

采用一系列温和的化学降解法对松辽盆地南部嫩江组烃源岩的干酪根进行连续的选择性化学降解，并对不同降解产物进行色谱—同位素比值质谱分析。研究表明碱性水解和脱硫产物以一元脂肪酸和正构烷烃为主，其中正构烷烃碳同位素分布曲线呈现一定的“负倾”（即随碳数增加呈现逐渐贫13C）趋势；一元脂肪酸以C16和C18为主，具有明显的偶碳优势，与同碳数的正构烷烃具有相似的碳同位素组成。氧化产物则以一元脂肪酸和α,ω 二元脂肪酸为主，一元脂肪酸低碳数部分呈现“负倾”趋势，高碳数部分则呈现“正倾”的趋势；α,ω 二元脂肪酸与低碳数的一元脂肪酸具有相似的分布，表明它们可能具有相同的母源。对比研究表明JL 30抽提物中正构烷烃可能存在混源的影响，其碳同位素组成是多源混合的结果。  相似文献   

Spatial pattern of Karst rock desertification in the Middle of Guizhou Province,Southwestern China   总被引：13，自引：0，他引：13  

Qiu-Hao Huang  Yun-Long Cai 《Environmental Geology》2007,52(7):1325-1330

Karst rocky desertification is a typical type of land degradation in the Southwestern China. It has great ecological and economical implications for the local people. Landsat images from the middle of Guizhou Province collected in 1974, 1993 and 2001 were used for change detection of the pattern of Karst rocky desertification. The results show the following findings: (1) Desertification area expanded drastically in 27 years, at an increasing rate about 116.2 km²/year. (2) High areas (900–1,500 m) are the most affected. (3) Areas with the slope <5° or >25° are also easily tend to be Karst rocky deserted. (4) The process of Karst rocky desertification is nearly irreversible. Few areas of Karst rocky desertification could be meliorated to non-desertification land. (5) Most of the degraded lands are located in the south and the central of the study region, and the meliorated land areas are sparsely located in the east and the west part of the region. All these findings would provide bases for the decision-making of the local government to improve the Karst rocky desertification  相似文献   

枯草芽孢杆菌(Bacillus subtilis)降解萘的动力学研究     

方世纯  郝瑞霞  鲁志强 《高校地质学报》2007,13(4):682-687

枯草芽孢杆菌(Bacillus subtilis)HBS-4是从油田中分离出来的一株能高效降解有机物萘的菌株。当萘的初始浓度为100mg时,该菌株在pH为8.0,温度为40℃下具有较好的降解效果,作用69h能降解50%以上的萘。通过HBS-4菌株降解萘的动力学研究,在Williams结构模型的基础上建立了HBS-4作用萘的四组分动力学模型,并用此模型解释菌株HBS-4在降解萘的过程中,葡萄糖含量、菌液浓度、pH、Eh随时间的变化特征。  相似文献   

乌鲁木齐市建设生态城市现状的比较分析及发展对策研究   总被引：10，自引：0，他引：10  

钱翌  朱建雯 《干旱区地理》2007,30(2):274-282

乌鲁木齐是绿洲城市,自然环境比较脆弱,由于城市建设缺乏生态环境规划,能源消费结构不合理以及特殊的自然地理等原因,致使城市的生态环境问题十分突出,建设生态城市是乌鲁木齐市未来发展的必然选择。从城市生态系统的结构、功能和协调度三个方面构建了生态城市的评价指标体系,采用层次分析法对乌鲁木齐市生态城市建设现状进行了定量分析,同时选择北京、上海、成都、西安、兰州等5个城市的生态化程度进行对比,结果表明:乌鲁木齐市的结构指数为0.241,低于对比的5个城市;功能指数乌鲁木齐为0.271,远低于上海(0.615)、北京(0.466)和兰州(0.343),与西安(0.272)接近,略高于成都(0.222);从城市协调度来看,乌鲁木齐市的指数值为0.306,为6个城市的最小值,生态综合指数由高到低分别为北京(0.580)>上海(0.579)>成都(0.382)>西安(0.380)>兰州(0.360)>乌鲁木齐(0.270),乌鲁木齐市生态化程度为第Ⅳ级,即生态化程度较低,为6个城市中的最低值。总体上为较发达地区城市的生态化程度较高,中西部地区城市的生态化程度较低。乌鲁木齐市建设生态城市应采取的关键对策包括以下几个方面:1、编制城市综合生态区划,做好城市生态规划;2、优化能源结构,大力发展清洁能源;3、建立排污权交易制度,控制大气污染;4、采用边际成本定价方法、制定科学的水价、优化配置水资源;5、合理布局城市景观生态,搞好城市绿化及荒山绿化。  相似文献   

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   

气候影响下的荒漠下的荒漠化监测     

A.N.左洛托克瑞林 《干旱区地理》2007,30(6):797-804

根据揭示沙漠化扩张内在规律的相关气候驱动因子的假说,气候作用影响之下的沙漠化是在具反射率-降水正、负反馈特点的气候系统之中的区域干旱化过程与干旱土壤退化过程相互作用的结果。在辐射调节下的地表下垫面温度占主导的条件下,气候成因的沙漠化是由区域气候系统反馈所形成。正反馈的外部调节因子是降水量的变化和极端降水事件(特别是旱灾)的出现频率,降水量减少以及降水频率的降低直接影响沙漠化的程度。20世纪下半叶,人类因素导致的干旱土地退化作为另外的正反馈调节因子,其重要性正在增加。通常正反馈的扩大趋势会被通过蒸腾而进行的地表温度调节的负反馈所抑制。由正反馈到负反馈的转换是通过地球表面与大气层之间的热量交换的调节所确定的,其中非潜热因子处于增加状态。上述情况在反射率和地表温度同时增加的条件下发生。在超出绿色植物生物量及其NDVI指数阈值的条件下,负反馈向正反馈的转换就会发生。人为作用导致的植被退化加快了向绿色植物生物量阈值逼近的进程,从而引起气候因素驱动的沙漠化扩大。一个主要由气候因素影响的荒漠化区域,在大多数情况下,其绿色生物量均在季节变化和年际变化中达到了阈值。在中度的人为影响的植被退化条件下,这些地域一般都包括部分干旱与半干旱土地。然而有时,人类活动也会导致干旱的半湿润土地退化。本文运用Turan和Sahel地区1982-2001年NDVI指数的监测结果,分析了全球变暖和人为作用导致的土地退化。  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