Exchange and solution phase chemistry of acid, highly weathered soils .I. Investigation of mechanisms controlling Al release into solution

Abstract

Soil solid phase and soil solution characteristics were evaluated on surface and subsoil horizons of 60 acid, highly weathered soils in the unamended state, and on a subset of 39 surface horizons following the addition of CaSO4.2H2O. The activity of Al3+ Was found to be strongly correlated with the soil solution pH, with Al3+ activity increasing as pH decreased. For surface soils in the unamended state, and for the majority of subsoils, the Al3+ activity calculated was comparable to the theoretical activity supported by the dissolution of gibbsite (Al2O3.3H2O). The Al3+ activity in CaSO4.2H2O-amended samples tended to fall below that maintained by gibbsite dissolution and was more closely correlated with the Al3+ activity supported by the dissolution of jurbanite (AlSO4 (OH).5H2O).