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Bragantia

Print version ISSN 0006-8705On-line version ISSN 1678-4499

Bragantia vol.32 no.unico Campinas  1973

https://doi.org/10.1590/S0006-87051973000100007 

Determinação de cargas elétricas em solos

 

Determination of electric charges in soils

 

 

Bernardo van Raij*

Seção de Pedologia, Instituto Agronômico

 

 


SINOPSE

As cargas elétricas dos solos estudados variaram em função da concentração da solução, do pH e da valência dos íons trocáveis. Optou-se pela determinação das cargas em condições de equilíbrio relativamente a pH e concentração da solução, omitindo-se uma lavagem total do excesso de solução salina. Cargas positivas e negativas variaram com o sal empregado, para amostras do horizonte B2 de um Latossolo Roxo e de uma Terra Roxa Estruturada, aumentando na ordem NaCl<CaCl2<MgS04, para determinados valores de concentração e pH.


SUMMARY

Electric charges of soils were shown to vary with concentration and pH of the equilibrium solution and with the valence of the counter-ions. Accordingly, in determining the electric charges of soils, total removal of excess electrolyte should be avoided and charges should be determined by measuring ion uptake under equilibrium conditions with respect to concentration and pH. For given values of pH and electrolyte concentration, positive and negative charges determined with different salts for an Oxisol (Latossolo Roxo) and an Alfisol (Terra Roxa Estruturada), increased in the order NaCl<CaCl2< MgSO4 .


 

 

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LITERATURA CITADA

1. BARDSLEY, C. E. & LANCASTER, J. D. Sulfur. In: BLACK, C. A., cd. Methods of soil analysis. Madison, Amer. Soc. Agron 1965. p. 1102-1116. (Monogr. 9)        [ Links ]

2. BIRRILL, K. S. & GRADWELL, M. Ion-exchange phenomena in some soils containing amorphous mineral contituents. J. Soil Sci. 7:130-147, 1956.         [ Links ]

3. BROWN, A. S. A type of AgCl electrode for use in dilute solutions. J. Am. chem. Soc. 56:646-647, 1934.         [ Links ]

4. FIELDS, M. & SCHOFIELD, R. K. Mechanisms of ion adsorption by inorganic soil colloids. New Zealand J. Sci. 3:563-579, 1960.         [ Links ]

5. FRINK, C. R. The effect of wash solvents on cation exchange capacity measurements. Proc. Soil Sci. Soc. Am. 28:506-511, 1964.         [ Links ]

6. KOLTHOFF, J. M. & KURODA, P. K. Determination of traces of chloride. Anal. Chem. 23:1304-1306, 1951.         [ Links ]

7. MATTSON, S. Anionic and cationic adsorption by soil colloidal materials of varying SiO2/Al2O3 + Fe2O3 ratio. In: Intern. Congress Soil Sci. 1st, Washington, 1927. Transactions, v.2, p.199-211.         [ Links ]

8. OKAZAKI, R.; SMITH, H. W. & MOODIE, C. D. Hydrolysis and salt-retention errors in conventional cation-exchange capacity procedures. Soil Sci. 96:205-209, 1963.         [ Links ]

9. RAIJ, B. van. Determinação de cálcio e magnésio pelo EDTA em extratos ácidos de solos. Bragantia 25:317-326, 1966.         [ Links ]

10. ________. Electrochemical properties of some Brazilian soils. Cornell University, 1971. 144 fls. (Ph. D. thesis)        [ Links ]

11. ________ & PEECH, M. Electrochemical properties of some Oxisols and Alfisol of the Tropics. Proc. Soil Sci. Soc. Am. 36:587-593, 1972.         [ Links ]

12. RICH, C. I. Removal of excess salt in cation-exchange capacity determinations. Soil Sci. 93:87-94, 1962.         [ Links ]

13. SCHOFIELD, R. K. Effect of pH on electric charges carried by clay particles. J. Soil Sci. 1:1-8, 1949.         [ Links ]

14. SMITH, H. W.; MOODIE, C. D.; OKAZAKI, R. & ELLSWORTH, N. Hydrolysis and salt-retention errors in conventional catiou-exchange-capacity procedures: II. Soil Sci. 102:94-106, 1966.         [ Links ]

15. SUMNER, M. E. & DAVIDTZ, J. C. Positive and negative charges in some Natal soils. South Afr. .J. agric. Sci. 8:1045-1050. 1965.         [ Links ]

 

 

Recebido para publicação em 20 de maio de 1972.

 

 

* Com bolsa de suplementação do CNPq.

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