HEAVY-METALS INCIDENCE IN THE APPLICATION OF INORGANIC FERTILIZERS AND PESTICIDES TO RICE FARMING SOILS

The concentrations of Cd, Co, Cu, Ni, Pb, Zn, Fe and Mn in different i norganic fertilizers (urea, calcium superphosphate, iron sulphate and copper sulphate) and in pesticides (two herbicides and one fungicide) are evaluated together with the contribution of these metals in soils from their use. The study was mane in rice farming areas to the north of Albufera Natural Park (Valencia, Spain). The results obtained show that superphosphate is the fertilizer that contains the highest concen trations of Cd, Co, Cu and Zn as impurities. Copper sulphate and iron sulphate have the most significant concentrations of Pb, and are the o nly fertilizers in which Ni was detected. The three pesticides analyse d show similar Cd contents and the highest levels of Fe, Mn, Zn, Pb an d Ni are found in the herbicides. The most significant additions of he avy metals as impurities that soil receives from agricultural practice s, are Mn, Zn, Co and Pb. Three contamination indexes have been applie d to provide a basis for comparison of potential heavy metal toxicity. These results denote the potential toxicity of heavy metals in the st udied soils.