Evaluation of porous ceramic cups for monitoring soil-water aluminium in acid soils: comment on a paper by Raulund-Rasmussen (1989)

Following recent observations by Raulund-Rasmussen (1989) implicating A1 contamination of soil solutions isolated by suction-cup samplers, A1 release from porous ceramic cups in acid solutions was investigated. In our studies a flush of Al, followed by a gradual decrease in leaching over successive extractions was observed. The amount of Al released was retarded by the presence of 37 μmol dm^?3 of A1 in solution. Gibbsite solubility controls were not observed; all solutions isolated by the cups were undersaturated with respect to amorphous gibbsite. The cups evaluated in this study are appropriate for sampling acidic soil solution, provided they are suitably pretreated and then equilibrated in the field before use.