Biogeoquímica de lipídios em sedimentos da Foz do Rio Doce após a chegada dos rejeitos da barragem de Fundão

• Ano de defesa: 2023
• Autor(a) principal: Resende, Jéssica Sonaly da Silva
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal do Espírito Santo; BR; Doutorado em Oceanografia Ambiental; Centro de Ciências Humanas e Naturais; UFES; Programa de Pós-Graduação em Oceanografia Ambiental
• Palavras-chave em Português: Foz do Rio Doce; Rejeitos da Barragem de Fundão; Testemunhos; Sedimento superficial; Matéria orgânica; Marcadores moleculares; Doce River Mouth; Fundão dam tailings; Core sediment; Surface sediment; Organic matter; Organic markers; Ciências Ambientais
• Link de acesso: http://repositorio.ufes.br/handle/10/19024

Environmental studies focused on understanding the origin of organic matter (OM) have been widely addressed in coastal ecosystems, especially with constant anthropic interference, making them more vulnerable. Tools known as molecular markers have become effective as they indicate the occurrence of a specific source or processes. In this study, the organic compounds Aliphatic Hydrocarbons (AHs), Polycyclic Aromatic Hydrocarbons (PAHs) and Sterols, which are widely used to help understand the origin of sedimentary organic matter (SOM), were analyzed. Doce River Mouth (DRM) was directly impacted by the biggest environmental accident involving iron ore tailings, which released about 60 million m3 of tailings into the Doce River channel with the rupture of the Fundão dam, causing major environmental and social impacts. In order to understand how the arrival of the mud has been influenced the sediments of the DRM two short cores were collected in August 2017 (dry winter period), and samples of surface sediments from 15 stations distributed by the DRM were collected in 4 campaigns (August 2017 and 2018; and February 2018 and 2019) to understand the influence of seasonality on biogeochemical processes involving these organic compounds. Results of environmental parameters such as: %TOC, %TN, C/N and molecular markers widely used to evaluate possible sources of organic matter, such as Aliphatic Hydrocarbons (HAs) as well as the δ13C from specific chains of n-alkanes, PAHs and sterols are discussed. The results found for the cores showed that fine grains predominated, n-alkanes indicated an increase in the contribution of terrestrial OM with depth, PAHs showed moderate pyrolytic contamination, with a predominance of compounds with high molecular weight (HMW). The fecal sterol concentrations showed that the surface sedimentary of the cores had a lower sewage signal than before the mud, that is, a dilution of the sewage by the tailings probably occurred. For surface sediments, the sand fraction predominated, as well as the C/N with indices suggesting autochthonous sources, in the 4 campaigns. The HAs have indices that indicate petrogenic sources, with emphasis on the n-C24 chain with the highest concentration, however there are also other index indicating the contribution of terrestrial vegetation, which may indicate a mixture of sources. PAHs from HMW predominated showing a greater pyrolytic contribution, while sterols show a greater contribution from higher plant sources