Pedosphere 15(4): 484--490, 2005
ISSN 1002-0160/CN 32-1315/P
©2005 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Dissolution of aluminum in variably charged soils as affected by low-molecular-weight organic acids
LI Jiu-Yu1,2, XU Ren-Kou1 and JI Guo-Liang1
1 Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China). Email: jyli@issas.ac.cn
2 Graduate School of the Chinese Academy of Sciences, Beijing 100039 (China)
ABSTRACT
      Low-molecular-weight (LMW) organic acids exist widely in soils and play an important role in soil processes such as mineral weathering, nutrient mobilization and Al detoxification. In this research, a batch experiment was conducted to examine the effects of LMW organic acids on dissolution of aluminum in two variably charged soils, an Ultisol and an Oxisol. The results showed that the LMW organic acids enhanced the dissolution of Al in the two investigated soils in the following order: citric>oxalic>malonic>malic>tartaric>salicylic>lactic>malefic. This was generally in agreement with the magnitude of the stability constants for the Al-organic complexes. The effects of LMW organic acids on Al dissolution were greater in the Ultisol than in the Oxisol as compared to their controls. Also, the accelerating effects of citric and oxalic acids on dissolution of Al increased with an increase in pH, while the effects of lactic and salicylic acids decreased. Additionally, when the organic acid concentration was less than 0.2 mmol L-1, the dissolution of Al changed little with increase in acid concentration. However, when the organic acid concentration was greater than 0.2 mmol L-1, the dissolution of Al increased with increase in acid concentration. In addition to the acid first dissociation constant and stability constant of Al-organic complexes, the promoting effects of LMW organic acids on dissolution of Al were also related to their sorption-desorption equilibrium in the soils.
Key Words:  aluminum dissolution, low-molecular-weight organic acid, variably charged soil
Citation: Li, J. Y., Xu, R. K. and Ji, G. L. 2005. Dissolution of aluminum in variably charged soils as affected by low-molecular-weight organic acids. Pedosphere. 15(4): 484-490.
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