辽东山地冰缘地貌土壤磁化率与粒度间的关系

Correlation between the magnetic susceptibility and grain size of the soil on periglacial landforms in eastern Liaoning

对辽东山地冰缘地貌上覆土壤沉积物进行磁化率及粒度的测试分析,结果表明:土壤沉积中亚铁磁性矿物含量较大,质量磁化率较高。细粒沉积中超顺磁(SP)、单畴(SD)和多畴(MD)晶粒混合存在,少数样品几乎不含超顺磁(SP)晶粒。土壤质地以粘土质粉砂为主,粉砂其次,偶见砂质粉砂。土壤粒级整体偏细,分选不好,正偏居多,峰态多为很窄峰。磁化率高低与粒径大小存在显著的相关关系,粒度越粗、原生矿物含量越大,质量磁化率表现越高;粒度越细、单畴、多畴、超顺磁颗粒组分越多,频率磁化率表现越强。受化学风化作用微弱的土壤对应磁学特征更明显,磁化率与粒度的组合特征对研究土壤质地、成壤水平具有积极意义。

Magnetic susceptibility and grain size of sediments have been widely used in climate change, environment monitoring, paleoenvironment modeling and palaeoclimatic reconstruction research; meanwhile the relationship between them has been a hot spot nowadays, which records the details of the sedimentary environment information. In order to explore the magnetic properties and grain size characteristics of the overlying soil and simulate the environmental changes, we analyzed the magnetic susceptibility and grain size of the soil. It was found that the content of ferrimagnetic minerals was rich in the soil deposition. Consequentially the mass susceptibility was increased simultaneously. The result of frequency magnetic susceptibility showed the crystal grain of SP, SD and MD existed extensively within the fine particle sediment, and there was hardly any SP in few samples. The soil texture was mainly dominated by clayey silt. In addition, the soil texture also had other presentation by consisting of silt or sandy silt which was rarely discovered. Most of the soil particles were fine; the soil of the study area was mainly positive skew distribution, and the grain-size sorting was ＂Not good＂. As for leptokurtosis, most of the soil samples were ＂Very narrow＂. The results revealed that the value of mass susceptibility was significantly correlated with the grain size. The larger the grain size and primary mineral content was, the bigger the mass magnetic susceptibility was. The finer particles, the more components such as SD, MD, and SP would accompany a stronger frequency magnetic susceptibility. There was a notable positive interrelation between the volume content of sand and the value of mass susceptibility, and an observably negative relationship between the volume content of silt and the value of mass susceptibility. For frequency magnetic susceptibility, the reverse was true. The magnetism characteristics of soil here were more obvious, which have been weathered （chemical weathering） slightly. Taking the features of magnetic susceptibility and grain size into consideration, the comprehensive characteristics will provide theory guidance for the study of soil texture and pedogenesis process, and also has some practical significance.