乌鲁木齐市土壤磁学特征及其与粒度的关系
Magnetic properties and the relationship with particle size of topsoil in Urumqi

【目的】分析乌鲁木齐市市区、郊区表层土壤磁性和粒径分布特征的差异性，揭示土壤粒度与矿物磁性特征的关系，测试土壤磁性参数作为粒径代用指标的可行性，为未来运用磁学方法监测城市土壤污染提供参考。【方法】采集乌鲁木齐市市区建设用地及郊区农用地和未利用地表层（0～10 cm）土壤样品45个，采用磁测和激光衍射粒度仪测量土壤磁性参数和粒度，利用Pearson相关性分析和GIS技术计算磁性参数低频质量磁化率（χLF）、高频质量磁化率（χHF）、百分频率磁化率（χFD）、硬剩磁（HIRM）、软剩磁（SOFTIRM）和饱和等温剩磁（SIRM）与粒径含量的相关系数，并绘制空间分布图。【结果】除χFD外，市区建设用地土壤磁性参数均值均高于郊区农用地和未利用地，多畴粗颗粒亚铁磁性矿物主导了土壤样品的磁学性质；市区表土黏土含量低于郊区，粉砂、砂粒含量略高于郊区；研究区土壤粒度组成以粉砂为主，其次为黏土和砂；通过比较市区表土磁性参数与不同粒径含量间的相关系数绝对值发现，χLF与2～8 μm粒级，HIRM与8～16 μm、>63 μm粒级，χFD与16～32 μm、32～63 μm粒级含量的相关性最强。郊区农用地、未利用地土样的磁性参数与粒级含量无显著相关性；黏土和极细粉砂含量与χLF和SOFTIRM、SIRM、HIRM在西部、东北、中部和南部区域空间上存在正相关，与χFD的相关区域位于市区中部。细粉砂与SIRM和HIRM在西北部、东北部以及东南部存在正相关，与χFD在空间上分布一致性较少。中粉砂、粗粉砂和砂含量与χFD在西部、东北部和中部偏西南区域存在正相关。【结论】乌鲁木齐市市区、郊区表土磁性和粒径分布特征不同。市区建设用地表土的χLF、HIRM和χFD分别可作为2～8 μm粒级、细粉砂和砂粒级、中粉砂和粗粉砂含量的代用指标。在圈定的西部、东北、中部、南部、西北、东北、东南和西南区域，χLF、HIRM和χFD能更准确地反映粒级含量的高低。
【Objective】This study investigated the differences in magnetic properties and particle size distribution of urban and suburban topsoil in Urumqi.The relationships between the magnetic properties and particle size distribution and the feasibility of using particular magnetic properties as soil particle size proxy were also explored to provide reference for future monitoring of urban soil pollution using magnetic methods.【Method】In Urumqi,45 topsoil samples at depth of 0-10 cm were collected from urban and suburban areas with different land use types and spatial uniformity.Soil magnetic parameters including low field magnetic susceptibility (χLF),high frequency magnetic susceptibility (χHF),the percentage frequency magnetic susceptibility (χFD),hard isothermal remanent magnetization (HIRM),soft isothermal remanent magnetization (SOFTIRM) and saturation isothermal remanent magnetization (SIRM) and particle size were measured using magnetic measurement instrument and laser diffraction particle size analyzer.The Pearson correlation analysis method and GIS technology were used to determine the correlation between magnetic parameters and particle size.【Result】The average values of magnetic parameters except χFD of urban construction land were higher than those of agricultural land and unused suburban land.Multi-domain ferromagnetic minerals dominated magnetic properties soil samples.Clay content in urban topsoil was less than that in suburban topsoil,while silt and sand contents were slightly higher than those in suburban topsoil.The silt content was the highest,followed by clay and sand in Urumqi.Comparison of absolute values of Pearson correlation coefficients between magnetic parameters and different particle size fractions in urban topsoil