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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。
The two loess sections, Xifeng and Duanjiapo, were selected. For the L6-S5-L5 interval with significant changes in magnetic susceptibility, a preliminary quantitative simulation was performed by using the same medium for enrichment and growth of the magnetotactic bacteria (MB) The contribution of MB and magnetosomes (MSs) to the susceptibility of loess-paleosol sequences. After enriched culture MB, the magnetic susceptibility of Duanjiapo profile increased to some extent, up to 116.6% (DS5-1). The culture of MB was carried out on the paleosol samples XS5-1 and DS5-1, and the increase of the magnetic susceptibility of DS5-1 showed an approximately linear relationship with the inoculum size. In addition, the frequency of magnetic susceptibility and the ratio of FeO / Fe 2 O 3 in paleosol samples after growth and cultivation showed a similar trend, confirming the formation of magnetosomes. The results show that: 1) MB and MSs are one of the factors influencing the magnetic susceptibility of loess profile. Due to the influence of climate and geological environment, the MB growth and MSs formation in loess section are different, so the contribution to magnetic susceptibility Also vary; 2) MSs are part of loess-paleosol sequences in paleosol sequences. When the climatic environment is more suitable for the formation and preservation of MSs, the MSs will have a higher proportion of ultrafine particles (≤50 nm) in the loess section, and will have a more pronounced effect on the susceptibility and frequency susceptibility.