ABSTRACT Nitrate (NO3 –-N) leaching in tropical soils, which are more weathered, is influenced by their mineralogical, physical, and chemical characteristics. Thus, the present study aimed to evaluate the effect of the variation of net electrical charge on the mobility of nitrate, applied as potassium nitrate (KNO3) or calcium nitrate (Ca(NO3)2), in samples from A and B horizons of three Red-Yellow Latosols (Oxisols), with different mineralogical and textural characteristics. Hydrochloric acid (HCl) or sodium hydroxide (NaOH) volumes were added to previously sterilized soil samples in order to condition five hydrogen potential (pH) values, obtaining different net electrical charges. The experiment was carried out with leaching columns under laboratory conditions. The soil columns were percolated with solutions of KNO3 or Ca(NO3)2 or water (control). An increase in positive net charges was significant and varied according to the soil and percolating solution; in general, it resulted in an increase of up to 50% in nitrate adsorption in some soils. Larger amounts of adsorbed nitrate were observed in the columns filled with the B horizon of the clayey gibbsitic Red-Yellow Latosol, showing adsorption of 85% for a positive net charge of 2 cmolc kg−1. Regarding kaolinitic soils, lower adsorption was observed in the medium-textured kaolinitic Red-Yellow Latosol, which had lower clay content and positive net charge. Application of Ca(NO3)2, as a percolating solution, increased nitrate adsorption compared to the application of KNO3. This effect may be attributed to the increase in positive net charge promoted by calcium (Ca2+), being more evident for the highest negative net charges.

中文翻译：

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可变电荷热带土壤中硝酸盐的迁移率

摘要 硝酸盐 (NO3 –-N) 在风化程度更高的热带土壤中的浸出受其矿物学、物理和化学特性的影响。因此，本研究旨在评估净电荷变化对硝酸钾 (KNO3) 或硝酸钙 (Ca(NO3)2) 硝酸盐迁移率的影响，在来自三个 A 和 B 层的样品中。红黄色 Latosols (Oxisols)，具有不同的矿物学和质地特征。将盐酸 (HCl) 或氢氧化钠 (NaOH) 体积添加到先前消毒的土壤样品中，以调节五个氢势 (pH) 值，从而获得不同的净电荷。实验在实验室条件下用浸出柱进行。土柱用 KNO3 或 Ca(NO3)2 或水（对照）溶液渗透。正净电荷的增加是显着的，并且根据土壤和渗透溶液而变化；一般来说，它导致某些土壤中硝酸盐吸附量增加了 50%。在充满粘土三水铝石红黄色 Latosol 的 B 层的柱子中观察到大量吸附的硝酸盐，对于 2 cmolc kg-1 的正净电荷显示 85% 的吸附。对于高岭土，在中等质地的高岭土红黄色 Latosol 中观察到较低的吸附，其具有较低的粘土含量和正净电荷。与 KNO3 相比，Ca(NO3)2 作为渗透溶液的应用增加了硝酸盐的吸附。