引用本文:陈梓炫,吕 镔,郑兴芬,马兴悦,何梅菊,赵国永.川西地区表土磁学性质及其环境意义[J].土壤学报,2019,56(3):661-671.
CHEN Zixuan,LÜ Bin,ZHENG Xingfen,MA Xingyue,HE Meiju,ZHAO Guoyong.Topsoil Magnetic Properties and Its Environmental Significance in West Sichuan[J].Acta Pedologica Sinica,2019,56(3):661-671
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川西地区表土磁学性质及其环境意义
陈梓炫1, 吕 镔2, 郑兴芬1, 马兴悦1, 何梅菊1, 赵国永3
1.福建师范大学地理科学学院;2.福建师范大学地理科学学院,福建师范大学地理研究所,湿润亚热带山地生态重点实验室--省部共建国家重点实验室培育基地;3.信阳师范学院城市与环境科学学院
摘要:
通过对川西地区表土样品进行系统的岩石磁学分析,并且结合气候要素探讨表土磁学性质与环境要素之间的关系。结果表明:(1)川西表土在成土过程中生成的细粒超顺磁(SP)和单畴(SD)的亚铁磁性矿物是磁化率增强的主导因素。该地区表土磁性增强机制与黄土高原类似。(2)在空间上,川西高原西部和南部地区的磁性矿物含量要高于东部和北部地区,而成都平原西部地区成土作用最强,磁颗粒细且含有较多高矫顽力磁性矿物。(3)川西表土的磁学参数和气候要素的研究发现年平均降水量(MAP)在600~1 000 mm之间磁化率、频率磁化率与MAP呈正相关关系,而磁学参数组合χ fd %/HIRM、ARM/HIRM、χARM /SIRM与MAP在这一降雨区间也呈正相关关系,然而这些磁学参数与MAP的相关系数不如黄土高原,可能与研究区复杂的地形、相对湿润的成土条件有关。
关键词:  川西地区  表土  磁学性质  环境因素
DOI:10.11766/trxb201806040188
分类号:
基金项目:国家自然科学基金项目(41402149、41602187和U1405231)和福建师范大学创新团队项目(IRTL1705)
Topsoil Magnetic Properties and Its Environmental Significance in West Sichuan
CHEN Zixuan1, LÜ Bin2, ZHENG Xingfen1, MA Xingyue1, HE Meiju1, ZHAO Guoyong3
1.College of Geographical Sciences, Fujian Normal University;2.College of Geographical Sciences, Fujian Normal University,Institute of Geography , Fujian Normal University,Key Laboratory for Subtropical Mountain Ecology (Ministry of Science and Technology and Fujian Province Funded);3.College of Urban and Environmental Science, Xinyang Normal University
Abstract:
[Objective] To clarify the relationship between magnetic susceptibility and climatic factors is the key to applying magnetic susceptibility to inversion of paleoenvironmental evolution. Therefore the study on magnetic properties of the modern topsoil is one of the effective means to establish the relationship between climate and magnetic susceptibility. As far little has been reported in the literature on magnetic properties of surface rock in West Sichuan, and the research in this field will sure help provide a theoretical basis for inversion of paleoclimate and establishment of climate models for the region. [Method] This study was oriented to analyze variation of the topsoil magnetic properties of the region and its influencing factors and mechanism and to explore relationships between the topsoil magnetic properties and environmental factors by taking into account the environmental information, so as to provide scientific data for the study on paleosol and paleoclimate of the West Sichuan leoss region, through analysis of topsoil samples for room temperature magnetism and high temperature magnetism. [Result] The magnetic hysteresis loop shows that the ferrimagnetic mineral low in coercivity was the dominaral magnetic mineral in the soil sample, while M-T curve analysis shows that ferrimagnetic mineral was, in addition to a small amount of magnetite hematite and weakly magnetic hematite, and some lepidocrocite in quite a number of the samples. [Conclusion](1) The fine-grained superparamagnetic (SP) and single domain (SD) ferromagnetic minerals formed during in-situ pedogenic processes in the topsoil of West Sichuan is the dominant factor leading to higher magnetic susceptibility. The mechanism for magnetic enhancement of the topsoil in this area is similar to that in the Loess Plateau. (2) In terms of spatial distribution, the western and southern parts of the West Sichuan Plateau are higher than the eastern and northern parts in magnetic mineral content and in SP and SD particle content, too. Pedogenesis is the strongest in the western part of the Chengdu Plain, where the SP content is higher and the magnetic particles in the topsoil lower in average particle size than those all the other parts of the region. In addition, the topsoil in the area contains relatively more magnetic minerals high in coercivity, which demonstrates that the process of strongly magnetic minerals converting to weakly magnetic minerals did once occur. (3) The influence of climatic factors (especially precipitation) soil magnetic properties is the highest. Through the exploration of topsoil magnetic parameters and climatic factors in West Sichuan, it is found that in the region where the mean annual precipitation (MAP) varies in the range of 600~1000 mm, ?lf andχ fdis positively related with MAP in a whole and so are the magnetic parameters, i.e. χ fd%/HIRM, ARM/HIRM, χARM /SIRM in rainfall interval, but the correlation coefficients of these magnetic parameters with MAP are lower than those in the Loess Plateau, which may be attributed to the complex topography and relatively humid soil forming conditions in the study area.
Key words:  West Sichuan  Topsoil  Magnetic properties  Environmental factor