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 bind ing ability of its fractions toward copper (Cu2+) ions. In addition, the bi nding ability (maximum complexing capacity - MCC) of the DOM was compared w ith that of humic (HA) and fulvic (FA) acids from a clay-loam soil. The stu dy was performed using Cu-2+ ions since this metal is widely used as a supp lement in pig diets and, consequently, is present in pig slurry. The techni ques adopted were gel filtration chromatography (GFC) and dialysis. GFC sho wed that the DOM from pig slurry is mainly composed of a fraction with an a pparent molecular weight higher than 5000 Da and the copper naturally prese nt in the slurry is completely complexed by this fraction. The dialysis pro cedure enabled MCC to be determined. The MCC of pig slurry DOM and soil HA, which contained a similar concentration of carboxylic groups, were analogo us, while MCC of soil FA, which contained double the concentration of carbo xylic groups, was higher.