STUDY ABOUT THE PATHS OF LEAD TRANSFER FROM THE ENVIRONMENT TO CULTIVATED VEGETABLES - APPLICATION TO THE AGRICULTURAL UTILIZATION OF SEWAGE SLUDGES

The physicochemical forms of Pb and its circulation through water or air, condition its biological accumulation. In order to appraise the relative importance of each vector, this element was used in experimental systems under various forms to study its association with soil, mineral fertilizers or sewage sludges. These sludges contained important quantities of organic matter and carbonate and, for some, Fe and Al oxides and hydroxides. The cultural systems were submitted to natural atmospheric conditions. Selective extraction procedures showed only a small availability of Pb in the sewage sludges and soils. That was in accordance with the insignificant exports via vegetables and leached waters. Whatever the treatment was, the Pb fell out particularly on the green parts of vegetables and, to a lesser extent, on the nontuberous roots, showing the predominance of atmospheric pollutions. No appreciable migration to the reproductive and reserve organs was observed.