Copper and zinc sorption on some B horizons of Quebec soils

The sorption of Cu and Zn on soils, as a function of pH, is important to an understanding of their mobility in the soil solution and their availability for plant nutrition. Copper and Zn sorption as a function of the pH were measured for six B horizons of two Orthic Humic Gleysols, two Orthic Humo‐Ferric Podzols, one Orthic Dystric Brunisol and one Orthic Sombric Brunisol. The results show that: 1) for the same amount of metal in solution and the same pH, more Cu is sorbed than Zn and 2) there is a maximum of sorption at or just above pH 5.00 and a large decrease as pH decreases. During the pH‐dependent sorption of Cu and Zn on six B horizons of Quebec soils, it was found that ions were released into solution thus altering the charge generated by the soil at low pH and the sorption behavior of Cu and Zn. The solid phase most likely to control the level of ions in solution is believed to be the amorphous and oxide forms of Al and Fe. The dissolution of these metal oxide or hydrous oxide materials also releases cations adsorbed on, or occluded in, the amorphous material.