Pedosphere 9(4): 323--330, 1999
ISSN 1002-0160/CN 32-1315/P
©1999 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Characteristics of soluble and exchangeable acidity in an extremely acidified acid sulfate soil |
| C. LIN1,2, M. D. MELVILLE2 and N. VALENTINE3 |
1 School of Resource Science and Management, Southern Cross University, Lismore, NSW 2480 (Australia);
2 School of Geography, The University of New South Wales, Sydney, NSW 2052 (Australia);
3 SMEC Australia Pty Ltd, North Sydney, NSW 2060 (Awtrnlia) |
| ABSTRACT |
| An extremely acidified acid sulfate soil (ASS) was investigated to characterise its soluble and exchangeable acidity. The results showed that soluble acidity of a sample determined by titration with a KOH solution was much significantly greater than that indicated by pH measured using a pH meter, particularly for the extremely acidic soil samples. This is because the total soluble acidity of the extremely acidic soil samples was mainly composed of various soluble Al and Fe species, possibly in forms of Al sulfate complexes (e.g., AlSO4+) and ferrous Fe (Fe2+). It is therefore suggested not to use pH alone as an indicator of soluble acidity in ASS, particularly for extremely acidic ASS. It is also likely that AlSO4+ actively participated in cation exchange reactions. It appears that the possible involvement of this Al sulfate cation in the cation adsorption has significant effect on increasing the amount of acidity being adsorbed by the soils. |
| Key Words: acid sulfate soils, aluminium sulfate complex, exchangeable acidity, hydrolysis, soluble acidity |
| Citation: Lin, C., Melville, M. D. and Valentine, N. 1999. Characteristics of soluble and exchangeable acidity in an extremely acidified acid sulfate soil. Pedosphere. 9(4): 323-330. |
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