
TY  - JOUR
A1  - Adams, M. L. 
A1  - Hawke, D. J. 
A1  - Nilsson, N. H. S. 
A1  - Powell, K. J. 
T1  - The relationship between soil solution pH and Al<emph type="7">3+</emph>concentrations in a range of South Island (New Zealand) soils
JF  - Soil Research
JO  - Soil Res.
Y1  - 2000
VL  - 38
IS  - 1
SP  - 141
EP  - 154
KW  - flow injection analysis, solubility, speciation.
UR  - https://doi.org/10.1071/SR98095 
N2  - Concentrations of Al3+ were calculated in soil solutions from concentrations of the monomeric &#8216;reactive Al&#8217; species (&#91;Al3+&#93; + &#91;Al(OH)2+&#93; + &#91;Al(OH)2+&#93; + &#91;AlF2+&#93;) 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&#8211;7.6, and showed a single curvilinear relationship for log &#91;Al3+&#93; v. soil solution pH, regardless of vegetation or soil type. At pH &#62;5.6, the data had a slope of &#8211;2.98 and fell between the amorphous Al(OH)3 and gibbsite solubility lines. At pH &#60;5.0, the data had a slope of &#8211;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 &#62;5.6) and soil organic matter (at pH &#60;5.0), respectively. This interpretation is supported by data from a pH-dependent Al&#8211;fulvic acid binding curve, for which calculated values of &#91;Al3+&#93; follow the same curvilinear relationship determined from the soil solution samples. 
ER  -

