Exchangeable aluminum

Soil-pH may influence both the concentrations of ions in the soil solution and the charge characteristics of the clay. Dispersion of clays is thus, to some extent, a pH-dependent process. At soil-pH(H2o,i i) values below 5, the aluminum concentration of the soil solution is normally sufficiently high to keep clay flocculated (Al3+ is preferentially adsorbed over divalent and monovalent ions in the soil solution). Between pH 5.5 and 7.0, the content of exchangeable aluminum is low . If concentrations of divalent ions are low, clay can disperse. At still higher pH values, divalent bases will normally keep the clay flocculated unless there is a strong dominance ofNa+-ions in the soil solution. 

Solketal Acrylate. 17 has been reported previously (3) and was synthesized In this case via standard (4) ester exchange (aluminum Isopropoxide catalyzed) from methyl acrylate and the commercially available acetone ketal of glycerine (solketal, Aldrich Chemical Co.). 

Hargrove, W. L. and G. W. Thomas. 1981. Effect of organic matter on exchangeable aluminum and plant growth in acid soils. In Chemistry in the Soil Environment. Stelly, R. H. Dowdy,... 

Each Oakley column was pre-leached, removing about half the adsorbed aluminum. As subsequent leaching continued during repetitive experiments, exchangeable aluminum was removed and the effluent pH increased. In all of the individual experiments described here, the concentration of aluminum in the effluent... 

Material/shape glass tubes (16 or 24 mm diam.) or mips held in exchangeable (aluminum) blocks glass tubes held in aluminum block round-bottomed flasks ... 

Aluminum was transported in the crystalline phase (> 80% ) at Sites 1 and 2, followed in importance by solution- (7-22%), oxide-(2-7%), and organic- (2-3%) phase transport. Surface-adsorbed or ion-exchangeable aluminum was unimportant. This distribution illus-... 

SCHOFIELD I can t answer that specifically. It would certainly appear, from the kinds of seasonal patterns we re seeing in aluminum release and in the specification of aluminum, that the reaction has to be rather fast. So we re not dealing with dissolution of silicate minerals for these very rapid changes in concentration, but rather a reaction with amorphous forms of aluminum or exchangeable aluminum in the soil. 

Table 3. Exchangeable aluminum, calcium, and magnesium in soils from high elevation spruce-fir sites.

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