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为了对长江源头高寒草地退化的时空过程规律取得全面客观的科学认识,本文利用20世纪70年代末、90年代初和2004年的陆地卫星遥感影像为信息源,结合气象数据、DEM、草地分布图及社会统计数据等辅助资料,以青海省治多县为例分析了近30年来长江源头的高寒草地生态系统退化的时空格局与过程及其驱动因素,从新的视角阐释高寒草地退化的过程与机理,为退化高寒草地的恢复、治理与区域可持续发展提供了科学依据。结果表明,研究区高寒草地生态系统的退化呈现自东南向西北,退化面积减少、退化程度降低、退化类型由复合型向单一型过渡的总体趋势。研究区东部是草地退化最严重的区域,主要表现为沿着原退化草地斑块的扩张,而西部即唐古拉山以北的广大地区由于下垫面起伏较低则以草地覆盖度的轻度下降退化为主。草地退化时间过程特征的总体趋势是持续退化、后期加剧,前后两个时段对比可以看出草地退化比重和程度皆呈逐渐加剧的趋势,退化面积比重净增9.86%。地形因素的影响分析亦发现,研究区高寒草地退化主要发生在海拔4500～4900m、坡度5～15°范围内的阴坡。研究区草地退化格局在20世纪70年代以前就已经形成,气候变化对高寒草地退化的影响是长期、缓慢的,而研究区人口和家畜数量变化的分析可以得出人类活动特别是过度放牧是草地退化发生的最重要诱因。 相似文献
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双隐性黑甜玉米营养成分的研究 总被引：5，自引：0，他引：5
经系统分析和测定黑玉米和其它谷物主要营养物质的含量,结果表明：黑玉米营养成分种类齐全,含量丰富．含有１８种氨基酸,包括人体必需的８种氨基酸;还原糖的含量是普通黄玉米的２１５倍;含有大量的无机微量元素;还含有其它谷物不具备的Ｖｃ和较丰富的超氧化物歧化酶 相似文献
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杂多酸的制备，大多采用水热合成的方法，随着科技的进步和环境友好型社会类型的要求，杂多酸制备越发的趋近于环保，致使微型实验的产生。又因杂多酸在催化上卓越的表现，所以杂多酸化学与多学科都有交集，比如生物质水解，精细化工合成上，有机合成等方面。 相似文献
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Historic parchment is a complex biological material, and due to various methods of production or inks used, unknown environmental histories of objects and heterogeneous nature of animal skin, it represents a particular analytical challenge. Due to the number of variables it is likely that patterns in degradation of these historic objects can only be revealed by surveying the material properties of a significant number of real objects. In this work, a sacrificial collection of ca. 100 historic parchments (fifteenth to twentieth century) was characterized using a range of techniques available to conservation practitioners that can usefully be used to reliably and rapidly characterize parchment. We focused on micro-destructive methods, such as shrinkage temperature (Ts), as the most widely used indicator of parchment degradation. Lipid content, roughness, and ink pH were additionally measured, while a limited number of samples containing iron gall ink were also examined using scanning electron microscopy (SEM) and SEM-EDX, to explore the distribution of ink components. Even in the absence of detailed environmental histories, it is possible to acknowledge the significance of the effect of iron gall ink and its acidity, and of lipids on parchment degradation, as measured using Ts. This research reports valuable reference data, while the collection remains accessible for further research. 相似文献
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Martin Nordvig Mortensen Gilles Chaumat Francesca Gambineri Hartmut Kutzke Jeannette Jacqueline Łucejko Caitlin M. A. McQueen 《文物保护研究》2013,58(2):115-123
ABSTRACTSamples of conserved archaeological wood of different ages, origins, and conservation histories were aged in a climate chamber for seven months, while the humidity alternated between 30% RH for 12 hours and 80% RH for 12 hours at a constant temperature of 30°C. Photographs were taken once every hour, which enabled the creation of a time-lapse movie. Some samples degraded visibly, whereas others were unaffected. Most of the samples were robust and would be able to survive well even in a very poor museum climate. Among the sensitive samples, three types of degradation were identified, namely disintegration, pyrite oxidation, and efflorescence of white crystals. Disintegration was ascribed to dimensional changes caused by the RH alternations in very fragile wood. The white efflorescence was interpreted as the recrystallization of an alum-associated substance, possibly mercallite (KHSO4). The pyrite oxidation was observed as the efflorescence of a thick yellow, grey, and green powder. Characterization of selected samples was performed using X-ray fluorescence spectrometry, X-ray diffraction spectrometry, scanning electron microscopy with energy dispersive X-ray spectroscopy, inductively coupled plasma – optical emission spectroscopy, Fourier transform infrared spectroscopy, ionic conductivity – liquid chromatography, and pyrolysis-gas chromatography-mass spectrometry with in situ silylation using hexamethyldisilazane. 相似文献
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Benjamin Bartl Ludmila Mašková Hana Paulusová Jiří Smolík Lenka Bartlová Petr Vodička 《文物保护研究》2016,61(4):203-208
This study focuses on the changes in properties of cellulose-based paper, which can take place as a consequence of its contamination by dust particles. The PM1 (fine) and PM10 (coarse) fractions of the dust particles from archival repositories were collected on cellulose filters Whatman 41, polytetrafluorethylene, and quartz filters. The latter two types of samples were subsequently analyzed gravimetrically, with ion chromatography, PIXE, and the thermal–optical transmission method, giving mass, ionic, elemental carbon, and organic carbon concentrations. After artificial aging, the viscosity-average degree of polymerization of cellulose (DPv) was measured. It was confirmed that cellulose-based paper can undergo substantial changes when contaminated by dust particles and artificially aged. The decrease of the DPv of cellulose showed a negative correlation with the deposited mass of sulfate ions in the dust particles. Considering the particle size fraction, the results suggest the decisive importance of the fine (PM1) particles. The results provide better understanding of how particulate matter contributes to the chemical degradation of cellulose-based paper. Such knowledge is of importance when considering appropriate conservation measures in archives, libraries, and galleries. 相似文献
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降解塑料目前存在的主要问题及今后发展方向 总被引：1，自引：0，他引：1
综述了光降解塑料、生物降解塑料、光一生物降解塑料的生产方法；提出降解塑料目前存在的降解速度事控性差、降而不解、生产成本高等问题；并对市场状况及今后发展方向进行了分析。 相似文献
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Probes for measuring oxygen concentration were installed inside large samples of conserved wood from archaeological shipwrecks to record oxygen profiles as a function of depth under the wood surface. The concentration of oxygen was lower inside the wood than outside indicating that the supply of oxygen is limited and that oxygen is consumed within the material. This was confirmed by oxygen consumption rates averaging 1.3 ± 0.42?µg O2/g wood/day. The diffusion properties were estimated by placing the wood samples in a nitrogen atmosphere and measuring nitrogen breakthrough time to the oxygen probes at different depths. A high level of variation was observed between the breakthrough times measured at different depths of the samples. This indicated that the access of oxygen is irregular, possibly due to wood heterogeneity and uneven distribution of conservation agent. By recording oxygen concentrations inside archaeological wood under stable environmental conditions, it was shown that oxygen concentration profiles are almost constant over a time span of seven years. This indicates that oxygen consumption, and thus oxidative degradation, is constant for an extended period of time. It also shows that the oxygen concentration inside conserved archaeological wood is a steady state value controlled by the local balance between oxygen supply and oxygen consumption. 相似文献