Micronutrientes e metais pesados em fosfogesso – acúmulo, mobilidade e fator de transferência em latossolos de cerrado

• Autor(a) principal: Silva, David Faria da
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5441
• topic: Mapeamento; Substituição isomórfica; Mineralogia; Mapping; Isomorphous substitution; Mineralogy; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

The calcium sulphate dihydrate (CaSO4.2H2O), phosphogypsum, also known as agricultural gypsum, is one of the major residues generated in the production of phosphate fertilizers by means of solubilization process of phosphate rock with sulfuric acid. The generation rate is approximately 4.8 t for each ton of phosphoric acid produced, and its main disposal form is the stacking in nearby the factories. However, this type of final disposal can lead to environmental impacts, such as leaching and superficial outflow of toxic elements, such as F- and heavy metals, resulting in contamination of water resources and releasing of aerosols caused by wind erosion in the stacks. One way to minimize such impacts is by recycling this residue would be its use in agriculture. The use of phosphogypsum as a soil conditioner in subsurface has been a viable alternative for the utilization of this residue in agriculture. However, it is necessary to consider the content o some heavy metals as well other toxic elements in this material, which may limit its use. It is important to highlight that the gypsum is classified as Class IIA, that is, it is neither hazardous nor inert, since it presents levels of arsenic, fluoride, aluminum, iron, manganese and sulfates above the maximum limit allowed in solubilization tests according to the ‘Associação Brasileira de Normas Técnicas’ - ABNT. The objective of this work was to evaluate the use of phosphogypsum, from a company which produces phosphoric acid, as well as to evaluate the contamination of plants, soils and drained water. Phosphogypsum samples were collected from an active stack regularly used for direct application in soil. Samples of the 30 collection points were dried in oven at 60 ºC. Afterwards the samples were sieved in 0,250 mm (sieve 60 mesh), and then analyzed. Cultivation of corn and soybeans was performed in pots of 25 dm3 containing soil treated with increasing doses of the conditioner applied to the superficial layer (0-18 cm depth). The samples of soils utilized were of Red-Yellow oxysoil and Yellow Oxisoil, originated from the towns of Sete Lagoas and Três Marias, both in the ‘Cerrado’ region of Minas Gerais. The leaching solutions of the pots of corn and soybeans were periodically collected and analyzed for the determination of heavy metals. With these results it can be concluded that there was no significant contamination of soils, plants and water drainage after the short term use of phosphogypsum. Nevertheless, it is recommended that further reapplication must be carefully evaluated, from an environmental standpoint, particularly in sandy soil with groundwater near the surface.