黄土高原南缘S 5-1古土壤中胶膜的特征及其环境意义  

Characteristics and environmental significance of cutan in S 5-1 paleosol on southern Chinese Loess Plateau

作　　者：彭瑾 连霞 李惠平 黄传琴[1] PENG Jin;LIAN Xia;LI Huiping;HUANG Chuanqin(Ministry of Agriculture and Rural Affairs Key Laboratory of Arable Land Conservation(Middle and Lower Reaches of Yangtze River)/College of Resources and Environment,Huazhong Agricultural University,Wuhan 430070,China)

机构地区：[1]华中农业大学资源与环境学院/农业农村部长江中下游耕地保育重点实验室,武汉430070

出　　处：《华中农业大学学报》2021年第1期195-201,共7页Journal of Huazhong Agricultural University

基　　金：国家自然科学基金项目(41671234)。

摘　　要：以中国黄土高原南缘武功地区S 5-1古土壤为研究对象,对比分析其胶膜与基质土壤的矿物学与地球化学特征,明确古土壤结构体表面深色胶膜的类型及其环境意义。结果显示,拉曼光谱中400~800 cm-1的宽峰可能是多种铁和锰(氢)氧化物的混合光谱。锰和游离铁(Fe d)的相对富集证实结构体表面的深色胶膜为铁锰胶膜,这说明在S 5-1古土壤发育期间经历了周期性的氧化还原。S 5-1古土壤中的淀积粘化过程导致其容重大、总孔隙度低,降低土层透水性,易发生季节性淹水,为铁锰胶膜的形成提供有利环境条件。然而,因S 5-1古土壤中铁和锰的分离与积累时间短,其Mn/Fe比值较低,未达到亚热带地区典型铁锰胶膜中的水平。Fe d/Fe t比值反映的胶膜与基质土壤之间化学风化的差异未体现在矿物组成上,二者的原生矿物与粘土矿物组成基本一致。上述结果表明,S 5-1古土壤中铁锰胶膜的存在进一步证实了发育期间中国黄土高原南缘盛行亚热带气候。The mineralogy and geochemical composition of the cutan and matrix soil in the S 5-1 pedon at the Wugong section on the southern Chinese Loess Plateau(CLP)was investigated to provide more insight in the characteristics and environmental significance of the cutan in the S 5.The broad band between 400-800 cm-1 in the Raman spectrum of the dark cutan was attributed to the groups of Fe and Mn hydroxide/oxide.Enrichment of Mn and free iron(Fe d)in the cutan confirmed the presence of Fe-Mn cutan in the S 5-1 pedon which signified a periodic reduction under waterlogged conditions during the pedogenesis of S 5-1 pedon on the southern CLP.The low permeability of S 5-1 pedon as a result of lessivage of clay fraction characterized by high bulk density and low total porosity made the development of a seasonal perched water table possible.It provided favorable environmental conditions for the formation of Fe-Mn cutan.However,the low Mn/Fe ratio in the cutan indicated that the separation and accumulation of iron and manganese in the S 5-1 pedon was not up to the level of typical Fe-Mn cutan from subtropical regions.Silicate minerals in the Fe-Mn cutan was almost identical to the matrix soil.The difference of chemical weathering between the cutan and the matrix soil reflected by the Fe d/Fe t ratio was not epitomized by the mineralogical composition.The subtropical climate prevailed on the southern CLP during the pedogenesis of S 5-1 pedon was further confirmed by the occurrence of Fe-Mn cutan.

关 键 词：中国黄土高原 古土壤 胶膜 基质土壤 成土作用 成土环境 矿物学 地球化学 古气候 

分 类 号：S151[农业科学—土壤学]