【摘要】 选择西峰和段家坡两个黄土剖面 ,对磁化率变化显著的L6-S5-L5层段 ,通过对样品中的趋磁细菌 (MB)用相同的培养基富集及生长培养 ,初步定量模拟了MB和磁小体 (MSs)对黄土 -古土壤序列磁化率的贡献。富集培养MB后 ,段家坡剖面样品磁化率表现出不同程度的增高 ,最大达 1 1 6 .4% (DS5- 1 )。以古土壤样品XS5- 1 、DS5- 1 为介质生长培养MB ,DS5- 1 磁化率的增长与接种的菌液量呈近似线性关系。此外 ,生长培养后古土壤样品频率磁化率与FeO/Fe2 O3比值呈现出相似的变化趋势 ,证实了磁小体的形成。由此表明 :1 )MB和MSs是影响黄土剖面磁化率的因素之一 ,受气候和地质环境等因素的影响 ,不同地区黄土剖面MB的生长和MSs的形成存在差异 ,因此对磁化率的贡献也不尽相同 ;2 )MSs是黄土 -古土壤序列中超细粒磁性物质的组成部分。当气候环境比较适宜MSs形成及保存时 ,MSs在黄土剖面中超细粒 (≤ 5 0nm)磁性组分中比重会相应增高 ,对磁化率和频率磁化率的影响也更为突出。更多还原

【Abstract】 samples were collected from the L 6 S 5 L 5 layers at Xifeng and Duanjiapo sections on the Chinese Loess Plateau. Based on the enrichment and growth culture of the magnetotactic bacteria (MB), contribution of MB and magnetosomes (MSs) to the susceptibility of the Chinese loess-paleosol sequences was simulated. Susceptibility of most samples became enhanced after MB enrichment by the same culture, with the maximum of 116.4% (DS 5-1 ). Linear relationship is shown between the susceptibility of DS 5-1 and the volume of inoculating MB after 10 days of MB culture. In addition, the frequency dependent susceptibility of samples changes resembles the variations of FeO/Fe 2O 3 after MB culture. The above results suggest that: 1) MB and MSs are among the factors affecting the susceptibility of Chinese loess. However, due to the spatial difference in climate and other conditions, MB growth and MSs formation in Chinese loess in different sites are not the same, and therefore the contribution of MB and MSs to susceptibility is also somewhat different; 2) MSs is one of components of superfine magnetic material in loess-paleosol sequences. If the climate is suitable for MSs formation and preservation, the contribution of MSs to the frequency dependent susceptibility is more important.更多还原