Isotopically exchangeable Al in coastal lowland acid sulfate soils

• Isotopically exchangeable Al was compared to 1 M KCl or 0.2 M CuCl2 extractable Al.
• 1 M KCl always underestimated isotopically exchangeable Al concentrations.
• 0.2 M CuCl2 mobilised non-isotopically exchangeable Al
• 1 M KCl values require correction of ~ 1.7 to reflect exchangeable Al concentrations.