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Detrimental Sulfate Effects on Formation of Al‐13 Tridecameric Polycation in Synthetic Soil Solutions
Author(s) -
Kerven G. L.,
Larsen P. L.,
Blamey F. P. C.
Publication year - 1995
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/sssaj1995.03615995005900030019x
Subject(s) - neutralization , chemistry , soil water , sulfate , soil acidification , composition (language) , inorganic chemistry , soil ph , geology , organic chemistry , soil science , linguistics , philosophy , antibody , immunology , biology
The chemistry of Al in soil solutions and in surface waters is complex and has included evidence of the tridecameric polycation, known as Al 13 , in an acid forest soil. The Al 13 polycation is the dominant species formed when Al solutions are partially neutralized under controlled laboratory conditions, and solution culture studies have shown Al 13 to be highly toxic to root growth. Doubt has been raised, however, as to the occurrence of the Al 13 polycation in natural systems. The objective of this study was to examine the effects of solution composition, comparable with soil solutions extracted from acid soils, on the formation of the Al 13 polycation using both 27 Al nuclear magnetic resonance (NMR) and spectrophotometric methods. The presence of Ca, Mg, K, Cl, and NO 3 during partial neutralization had no effect on the formation of the Al 13 polycation. However, SO 4 at ≥50 µ M during partial neutralization to a OH/Al ratio of R = 2.0 precipitated the major proportion of Al and interfered with the formation of the Al 13 polycation. The addition of similar concentrations of SO 4 after neutralization had no effect on the measured Al 13 concentration. The presence of ≥250 µ M SO 4 resulted in no detectable Al 13 polycation present after the solution had been neutralized to R = 2.5. We suggest that in view of the ubiquitous nature of the SO 4 anion in soil solutions and surface waters, the Al 13 polycation is unlikely to be formed in measurable quantities.