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601.
Guangzhi Yin Qiangui Zhang Wensong Wang Yulong Chen Weile Geng Hairu Liu 《Safety Science》2012,50(4):792-796
The deformation of microstructure of tailings caused by seepage is the main factor that leads the tailings dam to be damaged and lose stability. The effect of seepage on microstructure of tailings has been studied by a self-made observation testing apparatus of micro-mechanics and deformation of tailings, and its mechanism also has been explained in mechanics of particulate matter. The results show that the deformation response to microstructure of tailings is fast under load. The settlement of sample increases stepwise. Firstly, the fine particles crumble, then skeleton particles move, so as to noticeable settlement. Because the loose particles migrate taken by seepage water, the upper pores become bigger and lower pores become smaller. The relation of seepage water and settlement changing with time could be divided into two stages. In each stage, the rates of seepage and settlement reduce with time, and between the two stages, the rate of settlement increases significantly and the rate of seepage reduces with time. The seepage has significant effect on the particle size distribution of tailings in different depths, which has a little effect on the coarse tailings; the proportion of fine tailings increases significantly with the depth increasing; the minimum particle size decreases gradually and median diameter reduces stepwise with the depth increasing. 相似文献
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黄河三角洲滨海湿地的维管束植物区系特征 总被引:1,自引:0,他引:1
在2007-2008年多次实地调查并参照相关资料基础上,对黄河三角洲滨海湿地进行了植被类型划分和湿地维管束植物生态类群、生活型划分,利用统计方法分析了研究区湿地维管束植物区系的科、属构成,地理分布区成分构成.研究表明,黄河三角洲滨海湿地有71科、199属、298种维管束植物,蓼科、藜科、苋科、豆科、菊科、禾本科、莎草科等7个大科为区系主体,上述7科共76属128种,占总属数的39.38%和总种数的43.99%;区系中单种属多,属的分化程度较高.区系中有59种盐生植物、46种水生植物、44种湿生植物、144种中生植物、7种旱生植物,水生植物、湿生植物的生活型以地面芽植物、地下芽植物为主,陆地中生植物、盐生植物的生活型以一年生植物为主.从分布区类型构成来看,区系中蕨类植物区域分布成分较多,种子植物中温带分布属最多,这反映出湿地植被具有一定的地带性特征,种子植物中热带分布属、世界分布属较多分别表明海洋性气候对湿地植被特征的影响及湿地植被的隐域性特征. 相似文献
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近年来的研究表明,在BC(黑碳)和OC(有机碳)之间,还存在着一种有弱吸光能力的OC,因大多显棕黄色而被称为BrC(brown carbon,棕色碳). 广泛存在的秸杆焚烧和冬季大量民用燃煤的使用,使国内BrC排放严重,但鲜见对其排放量的测算. 采用七波段黑碳仪(aethalometer)方法,对夏季小麦秸杆焚烧过程及冬季民用炉燃煤过程产生的烟气进行现场监测,根据BrC与BC的光谱关联性差别,分化出RBrC/BC(总光学衰减中BrC和BC的相对贡献). 结果表明:麦秆焚烧和民用燃煤烟气的RBrC/BC分别为1.754±0.278和0.183±0.142. 借助RBrC/BC值,结合现有的BC排放清单(2000年),初步推算出中国民用燃煤和秸杆田间焚烧BrC的排放总量(以BC当量计,下同)为(270.6±101.6)Gg,接近同期BC排放量的一半;其中秸杆焚烧的BrC排放量为(175.4±27.8)Gg,约占二者总量的65%;民用燃煤的BrC排放量为(95.2±73.7)Gg,约占35%. 该研究结果可为更全面的BrC排放测算奠定基础,并为研究BrC的大气化学及辐射强迫提供依据. 相似文献
607.
In terrestrial ecosystems, plant root exudates clearly play a crucial role in the belowground ecosystem. However, there have been few reports on root exudates from field-grown plants or mature trees in situ, especially when exposed to experimental warming. In this study, we adopted and modified a culture-based cuvette system developed especially for root exudation collection in the field to collect soluble root exudates of a subalpine coniferous species, Abies faxoniana, under experimental warming and nitrogen fertilisation treatments. We then analysed the chemical composition and relative abundance of root exudates using gas chromatography-mass spectrometry (GC-MS). The major chemical constituents of root exudates were phenols and their derivatives of all the different treatments, such as 2,6-di-tert-butyl-4-methylphenol. Experimental warming had significant effects on the relative contents of major compounds and an increase effect on the total phenolic acid compounds. By contrast, there were small significant effects of N fertilisation on root exudation and no significant effects of the warming×N fertilisation interaction. Meanwhile, warming also markedly increased soil polyphenol oxidase activity and it may be soil ecological adjustment response to changes of root exudation under global climate warming. 相似文献
608.
Yin Qi Daniel W. A. Noble Yayong Wu Martin J. Whiting 《Behavioral ecology and sociobiology》2014,68(12):2035-2042
In lizards, males are predicted to sprint faster and run for longer than females by virtue of higher testosterone levels and differences in morphology. Consequently, escape behaviour is also predicted to be associated with sex and locomotor performance, yet these links have rarely been explored. Here, we tested whether escape behaviour is associated with locomotor performance in the toad-headed agama, Phrynocephalus vlangalii, and whether it is sex-dependent. This species is also characterized by elaborate tail displays, which we examined as a potential pursuit-deterrent signal. Tail waves were performed by a very small proportion (2/58, 3 %) of individuals during predatory trials, suggesting that tail signalling functions exclusively in a social context. To understand the relationships between sex, escape behaviour and performance, we first measured escape behaviour (flight initiation distance, flight distance—measured differently compared to previous studies of lizard escape behaviour, and refuge use) in the field before measuring maximal sprint speed and endurance on the same individuals in the laboratory. Flight initiation distance did not differ between the sexes and was unrelated to performance capacity (maximal endurance and sprint speed) but was positively related to body size with larger individuals fleeing earlier. Males fled farther than females, but flight distance was also unrelated to either endurance or sprint speed. Interestingly, faster females were less likely to enter a refuge than slower females, whereas sprint speed and the probability of taking refuge were unrelated for males. Our results suggest that when males and females are not obviously sexually dimorphic, they are more likely to overlap in escape tactics. 相似文献
609.
草地为陆地生态系统的主体,是陆地上最主要的碳储库和碳吸收汇之一。近年来,随着“草原承包责任制”、“退耕还林还草”和“封育禁牧”等重大生态工程项目的实施及草地生态系统的恢复和草地生产力的提升,草地生态系统碳储量、固持潜力、土壤碳循环机制及稳定性机制越来越受到学术界的关切。文章全面综述了近年来我国草地生态系统碳储量及其碳过程的研究工作,总结了不同研究中,我国不同草地类型碳库的特征及其储量、分析了草地生态系统碳过程等,评述了土壤碳过程相关科学问题的研究进展,指出了当前草地生态系统土壤碳储量及碳过程的研究进展、存在的问题,分析了未来草地生态系统土壤碳研究的重点研究方向和发展趋势。研究表明:草地生态系统在调节碳循环和减缓全球气候变化中起着重要作用。但是,由于草地类型的多样性、结构的复杂性以及草地对干扰和变化环境响应的时空动态变化,至今对草地生态系统碳储量和变率的科学估算,以及草地生态系统土壤关键碳过程及其稳定性维持机制的认识还十分有限,随着高分辨率的MODIS、TM数据、数学模型及不同草地类型实测点的建立,以及通过枯落物碳库将植物碳库与土壤碳库的有机连接,草地生态系统的土壤碳储量及固持潜力取得了重要进展;土壤有机碳来源、组成,有机碳化学结构以及环境因子是影响土壤有机碳稳定性的重要因素,而固体赫兹共振、碳同位素示踪等对破解有机碳稳定性提供了重要手段。未来,还将进一步厘清草地生态系统土壤固碳的驱动机制,构建草地生态系统土壤固碳量化方法体系等。 相似文献
610.
Jing Peng Ke Wang Xiangbo Yin Xiaoqing Yin Mengfei Du Yingzhi Gao Philip Antwi Nanqi Ren Aijie Wang 《Frontiers of Environmental Science & Engineering》2019,13(6):93