Natural background values, geochemical mobility and bioaccessibility of rare earth elements in soils of Brazilian Amazon

• Autor(a) principal: Ferreira, Matheus da Silva
• Data de Publicação: 2021
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: https://locus.ufv.br//handle/123456789/29493
• topic: Solos - Amazônia; Solos - Teor de elementos traços; Avaliação de riscos de saúde; Química do Solo

Rare earth elements (REEs) have been the subject of several researches in recent years, due to their use in high-tech industries or to potential toxicity. Normally, the levels of REEs in the soil are low and do not cause effects to human health, however the anthropic action can increase the levels of these elements and consequently increase the risks associated with the REEs exposure. Thus, studies about the levels of REEs in pristine and urban soils and REEs availability for living organisms are necessary. The main of this thesis were to determine the quality reference values of soil (QRV) based on natural levels, performed the geochemical fractionation and bioavailability of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy , Ho, Er, Tm, Yb, Lu, Y and Sc in soils of the Brazilian Amazon. The soil samples used were obtained both in pristine environments (without anthropic action) and in urban environments, the samples were collected in the 0-20 cm and 60-80 cm layers. The soils of the Brazilian Amazon present variations of REE concentrations because of the dynamic interaction between geological characteristics, sediment deposits and anthropic inputs. However, the ecological risk associated with the contamination of REEs was considered low in urban soils. The QRVs recommendations for soils of the Brazilian Amazon should be based on the 90th percentile of the contents obtained from the soils sample population. The geochemical fractionation exhibited that the most bioavailable fractions of the soil (exchangeable phase, organic matter phase and Fe / Mn oxides phase) presented low levels and represented less than 20% of the total levels of REEs in all sampled soils. Oral bioaccessibility contents obtained by two in vitro methods (gastric protocol and gastric-intestinal protocol) and by single extractions represented less than 20% of the total content of the REEs. Non-carcinogenic risks and carcinogenic risks associated with oral exposure to REE were considerably low both for children and for adults in all soil samples from the Amazon. Keywords: Natural contents. Enrichment. Toxic Elements. Health Risk.