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Aluminum Speciation in Aluminum‐Silica Solutions and Potassium Chloride Extracts of Acidic Soils
Author(s) -
Hiradate Syuntaro,
Taniguchi Satoru,
Sakurai Katsutoshi
Publication year - 1998
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1998.03615995006200030012x
Subject(s) - chemistry , soil water , nmr spectra database , octahedron , monomer , dimer , nuclear chemistry , aluminium , chloride , potassium , ion , adsorption , precipitation , inorganic chemistry , spectral line , polymer , organic chemistry , geology , physics , astronomy , meteorology , soil science
To differentiate chemical species of Al in soil solutions, a method using nuclear magnetic resonance (NMR) was applied to laboratory preparations of hydroxyaluminum (HyA) and hydroxyaluminosilicate (HAS) ions ([OH]/[Al] = 2.0), and 1 M KCl extracts from acidic soils. The Al in a Al‐OH‐Si(OH) 4 mixture was separated into three fractions: Al 13 ([AlO 4 Al 12 (OH) 24 (H 2 O) 12 ] 7+ ), Al SYM , and Al NON . The Al 13 and Al SYM were quantitatively determined by 27 Al‐NMR at 63 and 0 ppm, respectively. The Al NON was defined as the Al that cannot be determined by 27 Al‐NMR. The Al SYM was attributed to electrically symmetric octahedral Al including monomer (and dimer) HyA ions, and the Al NON was attributed to electrically asymmetric Al including HAS and polymer HyA ions. The concentrations of Al 13 decreased with increasing Si/Al molar ratio of the mixed solutions, and Al 13 was not detected at Si/Al ≥ 0.28. With increasing Si/Al molar ratio, the concentration of Al SYM increased slightly, while Al NON increased significantly. In the KCl extracts from soils, the Al 13 was not detected at all. This result suggests that Al 13 is not formed in these soils, or that the persistence of Al 13 in the soil solution is strongly inhibited by adsorption or precipitation reactions. The presence of organically complexed Al (Al ORG ) was also directly detected in KCl extracts from upper horizons by 27 Al‐NMR spectra. The chemical shift of resonance peak of Al ORG was close to that of the 1:1 complex of Al oxalate. On average, 92 and 96% of the KCl‐exchangeable Al existed as Al SYM and Al SYM plus Al ORG , respectively.