Effect of biosolid application on the biogeochemical behavior of ²¹⁰Pb, ²²⁶Ra and ²²⁸Ra in the soil-plant system

Biosolids are byproducts of the treatment and processing of sludges, generated from urban and industrial sewage. Their disposal is presently of great concern worldwide since it can impacts the environment when used as fertilizer to improve soil productivity in a sustainable way or it can receives other destinies like incineration or burial in landfills, whenever considered unsafe for agricultural purposes. Traditionally, the enrichment of the soil with radionuclides is connected with industrial and mining activities. However, the European Commission and the United States, detected that adding biosolids to soils as fertilizers may establish an important scenario for radiological contamination, due to presence of the ²¹⁰Pb, ²²⁶Ra and ²²⁸Ra. In this work the impact of the application of biosolids in the concentration of ²¹⁰Pb, ²²⁶Ra, ²²⁸Ra in corn, growing in the Ferralsol was evaluated for two kinds of biosolids: one derived from Barueri, a metropolitan region in São Paulo (industrial waste); and other derived from the city of Franca, São Paulo countryside (household waste). According to the results there is no difference in the geochemical partitioning and concentrations of ²¹⁰Pb, ²²⁶Ra and ²²⁸Ra in crop due to use of biosolids. However it was possible to observe larger potential bioavailability of these radionuclides in the soil samples that received biosolid. The soil to plant transfer factor (TF) for ²²⁶Ra and ²²⁸Ra was not influenced by origin of biosolid or interaction between origin and dose according to variance analysis. The more elevated FT was observed to the ²¹⁰Pb indicating larger bioavailability of this element. The medium values of FT for the corn, found in this study, they varied from 1,45E-04 to 4,56E-04 to the ²²⁶Ra and from 3,78E-04 to 9,33E-04 to the ²²⁸Ra and these values were similar to the existent values in the literature. The FT values of ²¹⁰Pb (1,09E-03 to 2,52E-03) found to the corn were a little larger than the values cited in the literature. (author)