Author:
Adams M. L.,Hawke D. J.,Nilsson N. H. S.,Powell K. J.
Abstract
Concentrations of Al3+ were calculated in soil
solutions from concentrations of the monomeric ‘reactive Al’
species ([Al3+] +
[Al(OH)2+] +
[Al(OH)2+] +
[AlF2+]) obtained using a recently
reported flow injection analysis (FIA) chelating resin technique. Soil
solution samples came from 7 sites encompassing a range of New Zealand soils
(Brown, Gley, Pallic, Podzol, and Recent Soils) and vegetation types (pasture,
shrub lands, and indigenous and exotic forest). Previously published data from
a further 7 sites, obtained using a rapid (7 s) FIA technique, were
transformed to give compatible results. The resultant data
(n = 85) covered the pH range 2.7–7.6, and
showed a single curvilinear relationship for log
[Al3+] v. soil
solution pH, regardless of vegetation or soil type. At pH >5.6, the data
had a slope of –2.98 and fell between the amorphous
Al(OH)3 and gibbsite solubility lines. At pH <5.0,
the data had a slope of –0.46; further, the soil solutions were
under-saturated with respect to both minerals. These results are interpreted
as indicating control of Al solubility by Al(OH)3 (s)
(at pH >5.6) and soil organic matter (at pH <5.0), respectively. This
interpretation is supported by data from a pH-dependent Al–fulvic acid
binding curve, for which calculated values of
[Al3+] follow the same curvilinear
relationship determined from the soil solution samples.
Subject
Earth-Surface Processes,Soil Science,Environmental Science (miscellaneous)
Cited by
31 articles.
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