Soils originating from the Caiuá sandstone formation have low soil organic matter (SOM), clay content, and cation exchange capacity (CEC). The predominance of one component over the other might decisively influence the CEC of these soils. Particle size distribution and selective dissolution procedures associated to a suit of methods to determine the exchangeable capacity properties might clarify the relative importance of each soil component. The objective of this work was to evaluate the contribution of the different components of the solid fraction and their intrinsic attributes to the CEC of sandy-loam soils and their relation to the total organic carbon (TOC), C:N ratio, and soil mineralogy. For this purpose, 34 soil samples were selected from the Caiuá sandstone formation with significant variation in the carbon content. Clay size fraction was characterized by X-ray diffraction, routine chemical analysis, and total specific surface area-SSA T using EGME, before and after the removal of SOM with sodium hypochlorite solution. Different values of CEC and effective cation exchange capacity (ECEC) were determined following standard procedures. The soils presented high sand content (82.9 ± 5.9 %) and the mineralogy of the clay fraction is dominated by kaolinite (80 %) with the presence of illite, 2:1 clay minerals, and small amounts of iron and aluminum oxides. The CEC and ECEC values at pH 7.0 and ~5.6, respectively due to the SOM are 408.6 and 148.7 cmol c kg -1 of carbon, respectively. The SOM was responsible for 32 to 84 % (average 52 %) and 24 to 67 % (average of 46 %) of the CEC and ECEC of the soils, respectively. The CEC and ECEC of the inorganic fraction are 2.32 and 0.78 cmol c kg -1 of minerals, respectively. The CEC of the clay fraction increased with the TOC but decreased exponentially with the clay content. The total carbon content increased linearly with the C/N ratio. The SSA T showed a significant (p0.05) and positive correlation with the TOC and with the CEC of the soils.
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机译：来自Caiuá砂岩形成的土壤具有低土有机物（SOM），粘土含量和阳离子交换能力（CEC）。一个组分对另一个组分的优势可能果断地影响这些土壤的CEC。与用于确定可交换能力特性的套装的粒度分布和选择性溶出程序可以阐明每个土壤成分的相对重要性。这项工作的目的是评估固体分数和其内在属性的不同组分对沙壤土土壤CEC的贡献及其与总有机碳（TOC），C：N比和土壤矿物学的关系。为此目的，从Caiuá砂岩形成中选择了34种土壤样品，其碳含量显着变化。 X射线衍射，常规化学分析和总比表面积-SSA T使用EGME，在去除次氯酸钠溶液之前和之后的粘土尺寸馏分的特征在于。在标准程序后确定了CEC和有效阳离子交换能力（ECEC）的不同价值。土壤呈现高砂含量（82.9±5.9％），粘土馏分的矿物学由高岭石（> 80％）用伊尔硫酸岩，2：1粘土矿物和少量铁和氧化铝支配。 PH 7.0和〜5.6的CEC和ECEC值分别由于SOM分别为408.6和148.7 CMOL C kg -1碳。 SOM分别负责32％至84％（平均52％）和24至67％（平均46％）的土壤和eCEC。无机级分的CEC和ECEC分别为2.32和0.78 CMOL C kg -1的矿物质。粘土馏分的CEC随着TOC的增加而增加，但随着粘土含量指数逐渐降低。总碳含量随C / N比线性增加。 SSA T显示出显着的（P <0.05）和与TOC和土壤中的阳性相关性。
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