Copper(II) humate mobility in kaolinite soil

An investigation of the influence of humate on the mobility of copper(II) i ons in a kaolinite soil using leaching tests and electrokinetic experiments is reported. The data are interpreted in terms of humate-copper-clay inter actions and humate electrical charge. Humate is mostly immobile below pH8 b ut is more mobile in alkaline conditions (sorption to kaolinite reduces its mobility in neutral conditions). Copper humate complexes are mobile in bot h acidic and alkaline conditions, but not in neutral conditions where they are sorbed. The dissolved copper humate complexes that form in acidic condi tions are positively charged. The net effect of humate is to increase cupri c ion mobility in kaolinite soil, especially in alkaline conditions. (C) 20 01 Elsevier Science B.V. All rights reserved.