排序方式： 共有9条查询结果，搜索用时 15 毫秒
1
1.
2.
YUAN Xuyin DENG Xu SHEN Zhiyong GAO Yun 《中国地球化学学报》2007,26(4):384-393
The species of Cu, Pb, Zn, Cd and Cr in sediments of the Taihu Lake, China, have been analyzed using the sequential chemical extraction method. Variations in the chemical fractions of these metals and their geographic distributions have also been studied. For all five metals, the residual fraction is highest but the exchangeable fraction is lowest among all the fractions. Compared to other metals, Cd has the highest percentage in the exchangeable fraction, and Cr is associated mainly with the residual fraction. Cu in the organic fraction and Pb in the Fe-Mn fraction are the important species, whereas the lowest percentages are found for Cd in the organic fraction, Cu in the Fe-Mn oxide fraction and Pb in the carbonate fraction. With respect to spatial differences, the total contents in the non-residual fractions of the metals in bay sediments are found to be higher than those in other sediments. The fractions of Cd, Cu and Cr showed significant variations in different regions. The fractions of Pb and Zn, however, did not show significant variations in spatial distribution, suggesting different amounts and different paths of anthropogenic input for the metals. Comparisons of the metal speciation indicated that Cd might be the most bioavailable metal, followed by Pb. 相似文献
3.
生物迁移思想的起源与发展 总被引：3，自引：0，他引：3
生物迁移命题是由达尔文(1859)提出来的。他在《物种起源)一书中认为,一个物种只能有一个起源中心;在条件允许的前提下,它会从这个中心迁移到力所能及的地区。然而,当布克曼(1922)的"迁移炮弹"理论问世之后,迁移研究几乎陷于停顿状态差不多50年。李四光是在"迁移炮弹"阴影下,依然坚持迁移观点的少数科学家之一。越来越多的事实证明了达尔文迁移思想的强大生命力。屡见不鲜的化石"穿时"现象和时代差异,大量的生物地理新资料,使人们从不可知论的桎梏中逐渐解脱出来。特别是80年代以来,由于地壳运动理论研究的新需求,以及大陆漂移和海水进退规程研究的新进展,掀起了重新认识迁移的高潮。作者依据自己的积累和前人的研究成果认为,迁移的研究方法可概括为:最低层位的地理追索方法、演化程序的地理追索方法和相应环境的追索方法。迁移如同演化,在达尔文力的全弥漫作用(All pervadins action)下时刻在进行着。迁移与其说是生物自身的一种能力,倒不如说是环境给予的一种机会。迁移造就并维系着丰富多彩的自然生态系统。迁移研究必将发展而形成一门新的学科--古生物迁移学(Palaeobiomigratology)。生物迁移思想是与地质力学的诞生和发展共存的。李四光(1927,1928)在研究海水进退规程时,曾列举了伴随海水南北方向的运动,生物作相应迁移的许多事实。生物迁移和海水运动,是性质完全不同的两种运动,其间必然存在着一个联系两者的中间环节;这个环节被李四光(1962)暗示为气候的变化,或两者共同导源于地球自转的不均衡。 相似文献
4.
300℃,50 MPa时金在NaCl-SiO_2-H_2O体系中的溶解度研究 总被引：1，自引：0，他引：1
利用可变形金袋热液设备,在300℃,50 MPa和NNO氧缓冲剂存在的条件下,测定了金和石英在不同pH的0.01,0.10和1.00 mol/kg NaCl溶液中的溶解度.推断了An-SiO_2-NaCl-H_2O体系中金的存在形式,求得下列溶解反应的平衡常数:Au H_2O=AuOH~0 1/2H_2,logK(AuOH_0)=-7.92±0.25;Au Cl~- H_2O=AuO-HCl~- 1/2H_2,logK(AuOHCl~-)=-7.56±0.65.研究表明,在地质上合理的pH、氯化物浓度和f(O_2)条件下,成矿溶液中金主要成AuOH~0和AuOHCl~-迁移.讨论了热液金矿床中常见的Au和SiO_2共生的原因. 相似文献
5.
Comparison between BCR sequential extraction and geo-accumulation method to evaluate metal mobility in sediments of Dongting Lake,Central China 总被引：1，自引：0，他引：1
姚志刚 《中国海洋湖沼学报》2008,26(1):14-22
The form in which a metal exists strongly influences its mobility and thus, the effects on the environment. Operational methods of speciation analysis, such as the use of sequential extraction procedures, are commonly applied. The Dongting Lake, the second largest fresh-water lake in China, contains three China wetlands of international importance, the East Dongting Lake, South Dongting Lake, and West Dongting Lake. In this work, an optimized BCR sequential extraction procedure was used to assess the environmental risk of Cd, Cr, Cu, Ni, Pb and Zn in contaminated sediment of the Dongting Lake. The procedure was evaluated by using a certified reference material, BCR701. The results of the partitioning study indicated that in the lake sediments, more easily mobilized forms （acid exchangeable） were predominant for Cd, particularly in the samples from the East Dongting Lake. In contrast, the largest amount of Pb was associated with the iron and manganese oxide fractions and Cu, Zn, Cr, and Ni analyzed were mainly distributed in residual phase at an average percentage greater than 60% of the total metals. The potential risk to the lake＇s water contamination was highest in the East Dongting Lake based on the calculated contamination factors. On the other hand, the total metal content was determined as well by inductively coupled plasma and mass spectrometry （ICP-MS） and assessed by using geo-accumulation index. The assessment results using geo-accumulation index were compared with the information on metal speciation. Both were correspondent with each other. 相似文献
6.
热水溶液地球化学 总被引：8，自引：0，他引：8
概述了热水溶液地球化学的主要研究内容和近年来在实验和理论研究方面的进展，包括高温高压下水的热力学性质、状态方程式、介电常数、电导率和电离平衡；ＮａＣｌ－ＣＯ２－Ｈ２Ｏ体系及其边界体系（ＮａＣｌ－Ｈ２Ｏ和ＣＯ２－Ｈ２Ｏ）的相关系、热力学性质和状态方程式，特别是利用人工流体包裹体技术和分子动力学模拟取得的新成果；高温高压电解质稀水溶液的电导测定；以ＨＫＦ模型为基础，热水溶液中不同物种的标准偏摩尔热力学性质和高温高压有关物理化学参数的估算；热水溶液中的物种形成（热液流体中的矿物溶解度测定、电势测量和谱学研究）；水和热水溶液结构的红外和拉曼谱学研究；水和热水溶液的传输性质（粘度和导热系数）。 相似文献
7.
印太交汇区珊瑚礁大三角是全球海洋生物多样性最高的区域,孕育了印度-西太平洋海域接近60%的软体动物种类,同时也有很高比例的特有物种。该海域是全球软体动物生物多样性研究的热点区域。已有不同国家的学者相继对印太交汇区软体动物的多样性、分类与系统演化等方面开展了研究,并取得了一系列重要的成果。基于此,本文从软体动物的生物多样性格局、成因、以及其影响因素等角度出发,对印太交汇区软体动物研究的主要方面进展进行了综述。先后有物种起源中心、积累中心、重叠中心、幸存中心等多种假说被提出以解释其多样性的成因。印太交汇区软体动物生物多样性分布格局与板块构造作用、海平面的变化、海洋环流以及暖池等密切相关。本文也指出了目前研究中存在的主要问题,分析了未来的发展趋势及面临的挑战,以期为今后的相关研究提供参考和思路。 相似文献
8.
Distribution and sequential extraction of some heavy metals in urban soils of Guiyang City,China 总被引：1，自引：1，他引：0
Sixty-two soil samples collected from different functional zones of Guiyang were analyzed for total concentrations and sequential extraction of Cr, Cu, Pb, Zn and Cd by ICP spectrometry. The average total concentrations ofCr, Cu, Pb, Zn and Cd in the soils of Guiyang were 92.9, 51.6, 44.1,139.3 and 0.28 mg/kg, respectively. The soils have been polluted by Cr, Cu, Pb, Zn and Cd to some extent in comparison with the background values of Guiyang. Significant differences were recognized in the concentrations of Cr, Cu, Pb, Zn and Cd in different functional zones. As for the sequential extraction, Cr, Cu and Zn were present mainly in the residual fraction, and Pb was present mainly in the oxidizable fraction. The reducible fraction of Cd accounts for 47.5%, and the residual fraction is lowest. The mobility and bioavailability of heavy metals follow the order of Cd〉Pb〉Cu〉Cr〉Zn. 相似文献
9.
利用筛选的12条10 bp的随机引物对采自武汉市东湖(3个样点)、南湖(3个样点)、月湖(1个样点)和关桥(1个样点)四个水体的天蓝喇叭虫(Stentor coeruleus)种群进行了随机扩增多态DNA(RAPD)研究,所得清晰条带显示不同样点样本之间存在着一定的变异,其遗传距离在0.076-0.416之间.用Rapdistance 1.04构建聚类图并探讨不同样点之间的遗传距离远近.结果显示南湖的3样点的遗传距离较近,在聚类图上聚成一枝,应该为同一个种群;而东湖的3个样点可能是由于地理隔离原因,在聚类图上有2个样点聚成一枝,而另1个样点被其他样点所分隔,不属于同一个种群.这种现象的发现从实例上支持了生物地理学关于物种形成的离散假说.更有意义的是本研究可启动水体微生物种群分化和物种形成及过渡的研究,并期望促进种群生态学方面的研究和谱系生物地理学及离散分化生物地理学的发展. 相似文献
1