Isoelectric point of soils determined by the diffusion potential method
1998; Elsevier BV; Volume: 85; Issue: 4 Linguagem: Inglês
10.1016/s0016-7061(98)00025-1
ISSN1872-6259
AutoresM.C Lamas, Rosa M. Torres Sánchez,
Tópico(s)Soil and Unsaturated Flow
ResumoAbstract The diffusion potential method was used to determine the Isoelectric Point (IEP) of the surface horizons of five soils (Typic Hapludoll, Typic Argiudoll, Vertic Argiudoll, Rhodic Kandiudalf and Lithic Kandihumult) in the following conditions: without treatment (natural), homoionized with K + (K + -soil) or Ca 2+ (Ca 2+ -soil) and after organic matter (OM) removal. Soil samples were characterized through their mineralogy, total organic carbon (TOC), clay percentage, cation exchange capacity (CEC), basic cations in the exchange complex, pH in water, Fe 2 O 3 content and zero point of charge (ZPC). The IEP pH of soils gave the following order: Ca 2+ -soil>natural-soil>K + -soil. These results were explained in terms of the higher affinity of bivalent over monovalent cations for negative surfaces. IEP pH of K-soils was dissimilar to ZPC pH , indicating that K + did not behave as an indifferent cation. Data of IEP pH after OM removal of Anguil (TH), Cepeda (VA) and Cerro Azul (LK) soils were lower than those IEP pH of the same natural samples and higher for Castelar (TA) and Virasoro (RK) soils. Results could not be explained in a simple way. The IEP pH of natural soils correlated with ZPC pH , pH in water and Fe 2 O 3 and clay contents. The diffusion potential method showed to be rapid, simple and adequate to measure IEP pH of natural or treated soils.
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