Fluorescence analysis of copper(II) and zinc(II) binding behaviour of fulvic acids from pig slurry and amended soils

Abstract

SummaryThe evaluation of the mechanisms and extent of interaction of Cu(II) and Zn(II) with fulvic acids (FAs) is of importance for understanding the mobility and bioavailability of these metals in pig slurry (PS)‐amended soils. In this work, a fluorescence titration method and a single site model were used to characterize the interaction of Cu(II) and Zn(II) with FAs isolated from PS, from soils amended with 90 and 150 m3 ha−1 year−1 of PS for 7 years and from the corresponding unamended soil. The binding capacities of FAs and the strengths of metal ion‐FA complexes were larger for Cu(II) than for Zn(II). With respect to the unamended control soil FA, PS‐FA was characterized by smaller binding capacities and stability constants. The binding capacities and affinities of PS‐amended soil FA were intermediate between those of unamended soil FA and PS‐FA, and tended to decrease with increasing amounts of PS applied to soil, thus suggesting a partial incorporation of FA fractions of PS into native soil FA.