Complexation capacity of dissolved organic matter from pig slurry: a gel filtration and dialysis study

The purpose of this research was to evaluate the apparent molecular weight distribution of dissolved organic matter (DOM) from pig slurry and the binding ability of its fractions towardcopper (Cu2C) ions. In addition, the binding ability (maximum complexing capacity - MCC) of the DOM was compared with that of humic (HA) and fulvic (FA) acids from a clay-loam soil. The study was performed using Cu2C ions since this metal is widely used as a supplement in pig diets and, consequently, is present in pig slurry. The techniques adopted were gel filtration chromatography(GFC) and dialysis. GFC showed that the DOM from pig slurry is mainly composed of a fraction with an apparent molecular weight higher than 5000 Da and the copper naturally present in the slurry is completely complexed by this fraction. The dialysis procedure enabled MCC to be determined. The MCC of pig slurry DOM and soil HA, which contained a similar concentration of carboxylic groups,were analogous, while MCC of soil FA, which contained double the concentration of carboxylic groups, was higher.