Analytical Capabilities of the Community Bureau of Reference Protocol to Estimate the Mobility of Nutrients and Toxic Elements from Mineral Fertilizer

The sequential extraction procedure of the Community Bureau of Reference (BCR) was applied to investigate the mobility of potentially toxic elements (As, Cd, Cr, and Pb) and nutrients (P, Ca, Mg, Cu, Fe, Mn, and Zn) in a multinutrient mineral fertilizer based on phosphate rocks supplemented with 10% (w w–1) micronutrient mixture (raw material used as a micronutrient source). For both samples, As and Cd were more mobile, whereas Cr remained in the solid residue. A higher mobility of Pb was observed in the micronutrient mixture; however, the high concentration of P (8.3% w w–1) in the fertilizer could have decreased Pb mobility as a result of Pb3(PO4)2 formation. The nutrients had great mobility, except Fe, which remained almost totally in the residual fraction in both samples. X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy analyses of solid residues showed that the ways in which elements were distributed in the sample particles could affect their mobility.