Pedosphere 15(5): 545--553, 2005
ISSN 1002-0160/CN 32-1315/P
©2005 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Point of zero salt effect: Relationships with clay mineralogy of representative soils of the São Paulo State, Brazil |
M. E. ALVES1 and A. LAVORENTI2 |
1 Departamento de Física e Informática, Institute de Física de São Carlos-IFSC/USP, São Carlos (SP) 13560-970 (Brazil). E-mail: mealves@ifsc.usp.br
2 Departamento de Ciências Exatas, Escola Superior de Agricultura 'Luiz de Queiroz'-ESALQ/USP, Piracicaba (SP)13419-980 (Brazil) |
| ABSTRACT |
| The point of zero salt effect (PZSE) is the soil pH value at which the magnitude of the variable surface charges is not changed due to variations in the ionic concentration of the soil solution. This property influences not only electrochemical phenomena occurring at the solid-solution interface but also the flocculation degree of the soil particles. In this study we investigated the relationships between the clay mineralogy and the PZSE values of representative soils of the São Paulo State, Brazil. The results confirmed the usefulness of the difference between the soil pH values measured in 1 mol L-1 KCl (pHKCl) and in water (pHH2O) (2 pHKCl-pHH2O) for estimating the PZSE of tropical soils, except for the ones rich in exchangeable Al; furthermore, the ΔPH index (pHKCl-pHH2O) was highly correlated with the difference between the PZSE and pHH2O values, reiterating the ΔPH utility for estimating both the signal and the magnitude of the net surface charge of tropical soils. Finally, correlation and multiple regression analyses showed that the PZSE value of weathered non-allophanic tropical soils tends to increase and to equal the soil pH due to the weathering-induced kaolinite destabilization and concomitant Fe- and Al-oxide accumulation. |
| Key Words: electrochemical properties, iron oxides, kaolinite, tropical soils, weathered soils |
| Citation: Alves, M. E. and Lavorenti, A. 2005. Point of zero salt effect: Relationships with clay mineralogy of representative soils of the São Paulo State, Brazil. Pedosphere. 15(5): 545-553. |
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