THE COMPLEXATION OF CU(II) BY ANTHROPOGENIC FULVIC-ACIDS EXTRACTED FROM COMPOSTED URBAN AND LIVESTOCK WASTES

The fulvic acid (fua) fractions of two samples of composted solid wast es [urban (urfua) and livestock (lsfua) wastes], commercialized to be used in agriculture as organic correctives or fertilizers, were analyz ed for their affinity towards Cu(II) at pH=6. Molecular fluorescence s pectroscopy (synchronous mode) was used to monitor the quenching cause d by the complexation upon addition of Cu(II) to fua. Spectral data we re preprocessed by a chemometric self-modeling mixture analysis method (SIMPLISMA) to detect the number of different types of fluorescent bi nding sites that exist in each fua, their spectra and the correspondin g quenching profiles [fluorescence intensity as function of the total Cu(II) concentration]. From the analysis of the quenching profiles, th e amount of binding sites (C-L) and the corresponding conditional stab ility constants (K') were calculated. Both fua samples have approximat ely C-L = 0.21 mmol/g and the logarithms of K' are 4.21(3) and 4.51(8) , respectively for urfua and lsfua. The differences detected between t hese fua samples and those extracted from natural soils can be attribu ted mainly to the relatively small humification extent of the present anthropogenic fua samples.