Leachability of Pb-210 in columns of tropical soils amended with phosphogypsum

Abstract

The phosphogypsum is a byproduct of the phosphate fertilizers industry, and it is generated on a large scale in Brazil. It is estimated the amount stockpiled is approximately 69 million tonnes. Although the composition of phosphogypsum is basically calcium sulfate dihydrate, the material may contain high levels of impurities that come from phosphate rock used as raw material. Among these impurities may increase the natural radioactivity, due to the presence of uranium and thorium series, which could prevent its reuse. The phosphogypsum can be used as a soil amendment, and it was called agriculture-gypsum. It can improve the soil structure for tillage, reduce soil erosion, increase sulfur and phosphorus availability and improve the composition of the fertilizers. Presently, part of the phosphogypsum produced has been stored in stacks, and part is used in agriculture. Therefore, it becomes important, to study the bioavailability of radionuclides relevant from a radiological point of view (238U, 232Th, 226Ra, 228Ra, and 210Pb) and the elements (As and metals Cd, Cr, Hg, and Pb), present in the Brazilian agricultural gypsum, taking into account its application on agriculture soil. To do this was submitted and approved a project research support to FAPESP titled "Leachability of metals and natural radionuclides in columns of tropical soils amended with phosphogypsum" (FAPESP 2010-10587-0). For this study will be used columns containing sandy soil and clay soil tiled with phosphogypsum percolated with EDTA solution. This is an integral part of this project and aims to determine the concentration of radionuclide 210Pb in samples of leachate solution of the columns contents soil with agricultural gypsum using a Liquid Scintillation Counting technique.(AU)