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土壤磁化率-温度曲线(κ-T)可用于鉴定土壤中磁性矿物类型。以水稻土、红壤、黄壤和砖红壤为对象,采用BaringtonMS2κ-T磁化率/温度系统,测定了不同土壤类型中磁性矿物种类。结果表明:水稻土κ-T曲线在300℃出现矿物相变点,黄壤、红壤和砖红壤在350℃出现相变点;水稻土和黄壤κ-T曲线呈现出磁铁矿的居里点(580℃),表明土壤磁性载体以磁铁矿为主;红壤和砖红壤的κ-T曲线呈现赤铁矿的居里点(680℃)。将水稻土和红壤分别制成2 mm、1 mm、0.30mm和0.15 mm的颗粒大小,称取相同质量土样(1 g)研究不同颗粒大小对土壤κ-T曲线测定的影响;称取过2 mm筛土样0.5 g、1 g、1.5 g和2 g,研究不同称样量对κ-T曲线测定的影响。结果表明:不同土壤类型,颗粒大小和称样量对κ-T曲线的测定有一定影响,但不会改变土壤中磁性矿物的相变点。它们对红壤和砖红壤的κ-T曲线测定影响甚少,对水稻土和黄壤的影响较大。实验证明在颗粒大小上选择过0.30 mm筛的土样,称样量上选择大于1 g的土样可以得到较明显的κ-T曲线,不会掩盖矿物的相变点。
Soil magnetic susceptibility - temperature curve (κ-T) can be used to identify the type of magnetic minerals in the soil. Taking the paddy soil, red soil, yellow soil and brick red soil as object, the magnetic species in different soil types were determined by Barington MS2κ-T magnetic susceptibility / temperature system. The results showed that there was a phase transition point at 300 ℃ for the κ-T curve of paddy soil, and the phase transition point appeared in yellow soil, red soil and red brick soil at 350 ℃. The κ-T curve of paddy soil and yellow soil showed the Curie point 580 ℃), indicating that the magnetic carrier is mainly magnetite. The κ-T curve of red soils and red soils presents the Curie point (680 ℃) of hematite. The paddy soil and red soil were made into 2 mm, 1 mm, 0.30 mm and 0.15 mm particle size respectively, and the same mass of soil sample (1 g) was weighed to study the influence of different particle size on the determination of soil κ-T curve; 2 mm sieve soil samples of 0.5 g, 1 g, 1.5 g and 2 g were used to study the effect of different samples on the determination of κ-T curve. The results showed that different soil types, particle size and sample weight had certain influence on the determination of κ-T curve, but did not change the phase transition point of magnetic minerals in soil. They have little effect on the determination of κ-T curve in red soil and latosol, but have a greater impact on paddy soil and yellow soil. Experiments show that in the size of the particles selected 0.30 mm sieve soil samples, the sample size greater than 1 g on the choice of soil samples can be more obvious κ-T curve, will not cover the mineral phase transition point.