Determination of cadmium, copper, chromium, nickel, lead and zinc in rock phosphates

Abstract

The possibility of food chain transfer is a matter of concern on studies related to heavy metals in mineral fertilizers. The objective of this paper was to determine the content of heavy methods and to compare three extraction procedures (Embrapa, 1999; USEPA 3051A and USEPA 3050B) for Cd, Cr, Cu, Ni, Pb, and Zn in national and imported rock phosphates. The quantification of the trace elements content was performed by air-acetylene flame atomic absorption spectroscopy. Among the studied phosphates, the thermophosphate presented significantly greater concentrations of Cd, Cr, Cu, Ni, and Zn whereas Cu, Ni, Pb, and Zn were found in greater contents in the natural phosphate 2. The reactive phosphate 3 presented the greatest quantity of Cd (145±13 mg kg^-1) and the natural phosphate 2, the highest quantity of Pb (234±9 mg kg^-1). The tested methods can be applied in studies concerning heavy metals in phosphate fertilizers.