Factors Affecting Soil Magnetic Susceptibility-Temperature(κ-T) Curve Measurement

Temperature dependence of soil magnetic susceptibility(κ-T curve) can be used to identify the types of magnetic mineral in soil.The κ-T curve of paddy soil,yellow soil,red soil and latosol were determined using Bartington MS2 magnetic susceptibility-temperature system to identify the type of magnetic minerals in soils.The results indicated that the κ-T curve of paddy soil and yellow soil display the presence of a magnetite-like mineral phase with Tc of about 580 ℃.The κ-T curves of red soil and latosol had a peak occurring around 350 ℃,followed by a rapid decrease of susceptibility between 350 ℃ and 600 ℃.The heating curves of red soil and latosol indicated the presence of Curie point temperature of about 680 ℃,suggesting the presence of hematite in soils.The paddy soil and red soil were passed through 2,1,0.30,and 0.15 mm sieve,respectively,to study the effect of different particle size on the κ-T curves.Different sample weight(0.5,1,1.5 and 2 g) with the same soil particle size was used to determine the κ-T curves to study the effect of different soil weight on the κ-T curves.The results showed that the different soil particle size and weight affected results of the κ-T curve measurement on a certain condition,while these two factors did not change the Curie point temperature of mineral phase in κ-T curve.The effect of soil particle size and weight on κ-T curve was also affected by soil type.The soil particle size and weight had larger effects in paddy soils and yellow soil than those in red soil and latosol.The experiment showed that,the application of soil samples with less than 0.30 mm in size and more than 1g in weight could obtain more obvious κ-T curve,which won't affect the identification of mineral phases in soils.