Speciation of copper in soil solutions from podzols and cambisols of S. Sweden

Abstract

Factors affecting the mobilization of Cu in spruce, beech, and birch forest soil profiles (podzols and cambisols) at two background sites in S. Sweden were evaluated. Inorganic forms and organically bound forms of Cu in soil solutions form 15 and 50 cm depths were estimated using a column cation exchange procedure. At 15 cm depth (approximately corresponding to lower E horizon in the podzols or to lower Ah horizon in the cambisols), almost all Cu in the soil solution was organically bound (non-exchangeable Cu=90 to 98% of total Cu) in both podzols and cambisols. Organically complexed Cu also constituted the predominant Cu form (non-exchangeable Cu=62 to 83% of total Cu) in soil solutions from the 50 cm depth, despite a relatively low [DOC] (3 to 14 mg L−1) and highly Al saturated organic compounds. Copper followed the same mobilization pattern as DOC, being highest at 15 cm depth in the podzol spruce and beech stands, and decreased with depth in all six stands. Results indicated that solution pH affected Cu mobilization in cases where the soluble DOC concentration was relatively low, as an increased pH seemed to increase the amount of Cu bound per g DOC.