INVENTORY AND RISK ASSESSMENT OF METAL CONTENT IN ORGANIC WASTE FOR A SAFE VALORIZATION IN AGRICULTURE

摘要

In this work, an environmental risk assessment of the reuse of organic waste of different origins and raw materials as fertilizer in agriculture was carried out. With that aim, an inventory of 206 cases corresponding to different studies developed on several locations worldwide, referring the content of heavy metals in different type of organic waste such as compost, sludge, or manure, was elaborated. The risk analysis was developed taking into account the heavy metal concentrations (mainly Cd, Cu, Ni, Pb, and Zn) in the different organic residues, in order to assess the possible accumulation of these metals in the environment and its biotransfer to the food chain and finally, to humans. A multicompartmental model was used to estimate the fate and distribution of metals in different environmental compartments, while a multipathway model was used to predict human exposure. The obtained Hazard Index (HI) for each waste was in many cases of concern, especially in the sludge samples, which presented an average value of 0.84. Among metals, Zn was the main contributor to total risk in all the organic wastes due to both the high concentration in the residues and its high biotransfer potential, while other more toxic metals, like Cd or Pb, represented a negligible contribution. This result might suggest that Zn content in organic waste should be reduced or more severely limited by legislation, for guaranteeing a safe management and reuse of these residues, according to the current policies promoted by the European Union.