| Abstract: | In order to identify the distribution of aluminium (Al) within an acid hillslope and its release to a stream, the spatial distribution of acid ammonium oxalate extractable Al (Alo) and exchangeable Al3+ have been investigated on a podzolized hillslope in Bicknoller Combe, Somerset, UK. The eluviated Al from topsoils is mainly deposited in the lower soil horizons forming podzolic B horizons, but some Al flows downslope carried by lateral throughflow. Al oxides may provide the main source of exchangeable Al3+ on the study slope due to high soil acidity. Examination of the spatial distribution of exchangeable Al3+ suggests that the slope hollow, where active convergent throughflow occurs, and the saturation wedge at the base of the slope are the main delivery routes of dissolved Al3+ to the stream. Divalent base cations (Ca2+ and Mg2+), supplied from atmospheric input and organic decomposition and carried by throughflow, exchange Al3+ via cation exchange reactions under high water content. Laterally illuviated Al oxides in the lower hollow adjacent to the saturation wedge probably provide a pool for continuous delivery of Al either as soluble or complexed forms to the stream via the saturated wedge. Copyright © 1999 John Wiley & Sons, Ltd. |
