Ferromagnetic compounds of seven southwestern soils from Pampean region comprise iron oxides and oxyhydroxides that have an important role, because of their high surface reactivity, controlling soil adsorption and formation/conservation of soil structure among other properties. We detected minutes of iron oxides quantities by selective dissolution techniques: acid oxalate extraction (<12% of the total Fe) and dithionite-citrate-bicarbonate (<44% of the total Fe), moreover, we identified/quantified mixtures of magnetite, maghemite, goethite and hematite minerals by environmental magnetism approach. The magnetic particle size dependent parameters evidence a relationship with extractable Fe oxides, indicating that magnetic particle size distribution on these soils is a relevant property associated to poorly crystalline and free amorphous Fe oxides. In addition, the particle size and SP concentration of ferromagnetic iron oxides are associated with increments of cation exchange capacity and the specific surface area of soil samples. The estimated amounts of hematite are below 2.20 wt%, and lower contents of about 0.25 wt% correspond to magnetite components. Both magnetic iron oxides concentration, as well as the remanent coercivity, increase towards the western region, on the contrary, anhysteretic ratios decrease and hence relatively coarser magnetic particles are dominant in this western region. The present study provides valuable data to characterize Aridisols, Entisols and Mollisols in a region of high fertility that comprises ones of the world’s most productive agricultural soil region.

潘邦地区西南七种土壤的铁磁化合物包含氧化铁和羟基氧化铁，这些铁氧化物具有重要的作用，因为它们的高表面反应性，控制土壤的吸附以及土壤结构的形成/保持等特性。我们通过选择性溶解技术检测了几分钟的氧化铁量：草酸酸萃取（占总铁的12％）和连二亚硫酸柠檬酸氢盐-碳酸氢盐（占总铁的44％），此外，我们鉴定/量化了磁铁矿的混合物，磁赤铁矿，针铁矿和赤铁矿矿物的环境磁性方法。取决于磁性颗粒尺寸的参数证明与可提取的铁氧化物有关系，这表明这些土壤上的磁性粒度分布是与弱结晶和游离的非晶态Fe氧化物有关的相关属性。另外，铁磁性氧化铁的粒径和SP浓度与阳离子交换容量和土壤样品比表面积的增加有关。赤铁矿的估计量低于2.20重量％，并且较低的含量约0.25重量％对应于磁铁矿组分。磁性氧化铁的浓度以及剩余矫顽力都向西部地区增加，相反，无磁比率降低，因此在该西部地区相对较粗的磁性颗粒占主导地位。本研究提供了有价值的数据来表征Aridisols，