Síntese, caracterização e avaliação da nanotoxicidade de nanoestruturas de óxido de zinco e hidroxiapatita visando aplicações em fertilizantes

Abstract

The increasing advance of nanotechnology has enabled the development of materials with optimized properties, including the production of nanostructured fertilizers aiming at increasing food and agricultural supplies production. Nanostructured fertilizers can provide the required nutrients to crops more efficiently than fertilizers at the micro- and macro-scale and at the same time, with inferior mobility than their liquid counterparts, avoing eutrofication in bodies of water. However, the increasing interest in using nanofertilizers also raises concerns about side effects caused by the release of nanomaterials in the environment, which can impact aquatic biota and consequently the human health. Changes in the size, shape and superficial charge of the nanoparticles modify the way they interact with the environment, and the inappropriate disposal and indiscriminate use of nanofertilizers can increase the level of toxicity, especially in water bodies. In this context, the present study aims to synthesize and characterize, by several physic-chemical techniques, nanofertilizers based on zinc oxide (ZnO) and hydroxyapatite Ca10(PO4)6(OH)2(HAP), and evaluate the potential nanotoxicity of these materials for the microalgae Pseudokirchneriella subcapitata, since it forms the base of the aquatic trophic chain. The synthesis of ZnO nanoparticles and HAP were carried out by coprecipitation and hidrothermalization methods, and after characterized regarding structure and morphology, they were used in the nanotoxicity bioassays. The results showed that the hydrothermal HAP nanoparticles with APMA presented high potential as a nanofertilizer, once no significant growth inhibition to algae was observed in the range of concentrations employed (50 mgL-1, 100mgL-1, 250mg L-1, 500mgL-1e 750mgL-1) and neither evidence of eutrophication process. However, ZnO nanoparticles, especially those which were not synthesized with APMA, showed high toxicity to microalgae in the range of concentrations employed (10mgL-1, 25mgL-1, 50mgL-1, 100mgL-1 and 200 mgL-1), which can be deleterious for sustainable application in agricultural crops. In addition, the shading effect and several deformations in the cellular morphology were observed, contributing to the increase the nanotoxicological effects.