Amorphous Material and Aluminum Interlayers in Quebec Spodosols

Clay fraction from spodic B horizons of Appalachian and Laurentian soils was recovered after organic matter and sesquioxides removal. Sodium citrate and sodium hydroxide further extracted various amounts of Al, Si, and Fe. Samples from the Appalachian sites released < 5% Al 2 O 3 + SiO 2 and < 1% Fe 2 O 3 . There were only small differences between the amounts of material extracted by both reagents. After citrate treatment, a moderate increase of CEC was observed and related to Al interlayer removal, while after NaOH + citrate treatment the CEC decreased slightly because of amorphous material removal. Samples from the Laurentian sites released from 9.3 to 30.0% Al 2 O 3 + SiO 2 in NaOH and subsequently 1.6 to 6.0% Fe 2 O 3 in Na‐citrate. The presence of large amounts of amorphous material prevented the identification of clay minerals by X‐ray diffraction analysis, and its removal caused a strong decrease of the CEC. Citrate alone extracted this poorly crystalline material at a slower rate and for these samples, this was followed by a decrease of the cation exchange capacity.