2种土壤磁性特征及其对磁性示踪实验的影响

Magnetic Properties of Two Soil Types and Their Effects on Soil Magnetic Tracer Experiment

通过磁性示踪耕作实验、土壤磁性背景值测定、土壤物理性质分析等方法研究了云南东川区蒋家沟流域2种土壤类型的磁性特征,并探讨了土壤磁性对耕作侵蚀磁性示踪实验的影响。结果表明:(1)砾石土磁性随粘粒和粉粒含量增加而明显增强(r=0.58,p<0.05;r=0.67,p<0.05),随砂粒增加而明显减弱(r=-0.71,p<0.05);黄棕壤粘土因受磁性矿物影响大,随土壤中砂粒含量增加而增强,砾石土磁性随土壤含水量增加而明显减小(r=-0.68,p<0.05)。(2)因受土壤侵蚀的影响,砾石土的磁性与坡度呈显著负相关关系(r=-0.701,p<0.05),即随坡度增大而明显减小。(3)土壤成土背景差异导致2种土壤磁性存在明显差异,即黄棕壤粘土的磁性(1 451×10-5SI)是砾石土磁性(53×10-5SI)的27倍。在耕作侵蚀的磁性示踪实验中,磁性背景值低的砾石土比磁性强的黄棕壤粘土有更好的磁性敏感性,更能准确反映耕作侵蚀位移。当混入磁性示踪剂的土壤磁性是土壤磁性背景值的30倍时,耕作侵蚀磁性示踪实验较为准确和可靠,以此作参考,不同磁性的土壤可以确定一个科学的磁性示踪剂用量。

The magnetic properties of 2soil types and their effects on magnetic tracer experiment of tillage erosion were analyzed in the Jiangjiagou watershed,Dongchuan district,Yunnan province,based on soil magnetic tracer experiment of tillage erosion,measurement of background value of soil magnetism and analysis of soil physical properties.The main results of this study were as follow：（1）Magnetism of gravelly soil was positively correlated with soil clay content（r=0.58,p〈0.05）and silt particle content（r=0.67,p〈0.05）,but was negatively correlated with soil sand content（r=-0.71,p〈0.05）and soil water content（r=-0.68,p〈0.05）.For yellow brown soil,soil magnetism increased with the increase of soil sand content.（2）Magnetism of yellow brown soil decreased with the increase of slope gradient due to soil erosion（r=-0.701,p〈0.05）.（3）Mean magnetism of gravelly soil（53×10^（-5）SI）was significantly（p〈0.05）lower than that of yellow brown soil（1 451×10^（-5）SI）.In the magnetic tracer experiment of tillage erosion,lower background values of gravelly soil magnetism led to better magnetic sensitivity and more accuracy in reflecting tillage translocation of gravelly soil,compared to that of yellow brown soil,which had strong magnetism.When the magnetism of soil mixed with magnetic tracer was 30 times higher than background values of soil magnetism,the results of magnetic tracer experiment of tillage erosion were accurate.Therefore,scientific magnetic tracer dosage can be determined according to the magnetism of different soils.