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Determinação sequencial de Cd, Cu, Mn e Pb utilizando análise de suspensão por FS-F AAS e avaliação da concentração de Hg em amostras de poeira urbana coletadas em Santo Amaro, Bahia, Brasil.

2026-04-27T18:38:57Z

Título: Determinação sequencial de Cd, Cu, Mn e Pb utilizando análise de suspensão por FS-F AAS e avaliação da concentração de Hg em amostras de poeira urbana coletadas em Santo Amaro, Bahia, Brasil. Autor(es): Francisco, Rafael Ribeiro Primeiro Orientador: Araujo, Rennan Geovanny Oliveira Abstract: This master’s dissertation addresses the development, analytical performance characteristics, and application of analytical methods for the determination of trace metals in urban dust samples, with a focus on the environmental assessment of the urban area of Santo Amaro, Bahia, Brazil. The work was divided into two complementary parts, involving distinct analytical approaches and environmental and human health risk applications. In the first part, an analytical method was developed and optimized for the sequential determination of Cd, Cu, Mn, and Pb in urban dust using sample preparation in the form of slurry and detection by flame atomic absorption spectrometry (F AAS) in fast sequential mode (FS). The study of sample mass indicated that the range between 10 and 75 mg provided the most suitable condition for the suspension preparation procedure, thus, a mass of 50 mg was selected, ensuring a good signal-to-noise ratio while maintaining analytical linearity. Fractional factorial design and Doehlert design were employed to optimize the experimental conditions, including the evaluation of the acidic medium, sonication time, and the use of a surfactant (Triton X-100). Experimental optimization indicated that the use of 1.25 mol L-1 HNO3, without surfactant addition, and a sonication time of 30 min resulted in the best analytical performance. The analytical method presented limits of quantification (LoQ) ranging from 3.03 to 81.6 mg kg-1. Accuracy was confirmed by the chemical analysis of certified reference materials (CRM) of fly ash (BCR 176R) and road dust (BCR 723), with agreement values ranging from 88.0 (± 0.6) to 91.8 (± 0.1)%. Precision was expressed as relative standard deviation (%RSD), with values below 5% (n = 3). The methodology enabled the analysis of urban dust with reduced reagent consumption and simplified sample preparation, supporting its applicability in environmental studies. In the second part, the direct determination of Hg was applied to 21 urban dust samples collected in the municipality of Santo Amaro, Bahia, using thermal decomposition and detection by atomic absorption spectrometry (AAS). The limits of detection (LoD) and quantification (LoQ) obtained were 0.08 ng g-1 and 0.25 ng g-1, respectively. Method accuracy was confirmed by the chemical analysis of a CRM for trace elements in multi-nutrient fertilizer (NIST 695), with an agreement of 106.3 (± 5.2)%. The %RSD value was below 5%. The analytical method allowed the quantification of Hg over a wide concentration range, revealing a heterogeneous spatial distribution, as well as good accuracy and precision. Hg concentrations ranged from 15.8 (± 0.3) ng g-1 to 1198 (± 29) ng g-1, with a mean of 54.9 (± 32.6) ng g-1 and a median of 46.1 ng g-1, after application of the Shapiro–Wilk (SW–W) normality test. The highest concentrations were observed in areas with greater urbanization, intense vehicular traffic, and proximity to industrial sites. Environmental interpretation was performed using the enrichment factor (EF), geoaccumulation index (Igeo), and ecological risk indices (Er), calculated based on a regional geochemical background specific to the state of Bahia. The results indicated significant enrichment and elevated ecological risk at localized points, with a very high potential ecological risk for the study area, considering the specific sampling period and the prevailing climatic conditions at that time. The sustainability of the analytical methods for the sequential determination of Cd, Cu, Mn, and Pb using suspension preparation and for the direct determination of Hg was evaluated using the AGREE (Analytical Greenness Metric) index, yielding scores of 0.78 and 0.86, respectively, indicating high adherence to the principles of Green Analytical Chemistry. Overall, the results demonstrate that the applied analytical methods are feasible, reliable, and suitable for the environmental monitoring of trace metals in urban dust. Editora / Evento / Instituição: Universidade Federal da Bahia Tipo: Dissertação

Avaliação da composição mineral de material particulado atmosférico coletado na região geográfica intermediária de Salvador e de Amélia Rodrigues, Bahia, Brasil

2026-03-19T18:19:16Z

Título: Avaliação da composição mineral de material particulado atmosférico coletado na região geográfica intermediária de Salvador e de Amélia Rodrigues, Bahia, Brasil Autor(es): Sacramento, Carlos Leandro Cruz Primeiro Orientador: Araujo, Rennan Geovanny Oliveira Abstract: Air pollution has been a major focus of study in the scientific community, aiming to understand its implications for human health, ecosystems, and material heritage, identifying itself as a key element in the pursuit of sustainable development. The accelerated growth of urban areas, driven by industrialization and population increase, has significantly contributed to the current scenario. In this context, the present work aims to investigate, evaluate, and quantify samples of atmospheric particulate matter in the form of total suspended particles (TSP) and respirable particles (PM₂,₅), according to the limits established by Resolution No. 491/2018 of the National Environment Council (CONAMA), in addition to chemically characterizing the mineral composition. Sampling was conducted in the Intermediate Geographic Region of Salvador, encompassing the municipalities of Lauro de Freitas, Madre de Deus, São Sebastião do Passé, São Francisco do Conde, and Amélia Rodrigues, in the Metropolitan Region of Feira de Santana, in August, September, and December 2021, covering both the dry and rainy seasons in the region. Collections occurred during nominal 24-hour periods, using three portable samplers (HANDI-VOL) for PTS and one portable prototype for PM₂,₅, operating simultaneously. The geometric mean concentrations of PTS and PM₂,₅ were below the limits established by Resolution No. 491/2018 of the CONAMA. After the sampling procedures, the particulate matter deposited on the filters was subjected to acid extraction, followed by chemical analysis by inductively coupled plasma optical emission spectrometry (ICP OES) to determine Al, Ba, Cr, Cu, Fe, Ni, Mn, Mo, Pb, Sb, V, and Zn. Based on the results obtained, the trace metals were grouped in ascending order of concentration (Mo < V < Sb < Pb < Ni < Mn < Zn < Ba < Cr < Al < Cu < Fe) for PTS. The concentrations of the chemical elements in the PM2.5 samples were below the quantification limit of the analytical method. With the predominance of Fe concentration in the chemical composition of the atmospheric particulate matter (PTS), the results obtained clearly showed that in the study region, the chemical composition of atmospheric particulate matter is strongly associated with natural sources, but is directly influenced by anthropogenic sources such as the use of fossil fuels, vehicular traffic associated with brake system wear, maritime traffic, industrial, petrochemical and port activities through the presence of Cu, Mn, Pb, Sb and Zn. An investigation of pollution indices was carried out using the enrichment factor (EF) and the geoaccumulation index (Igeo), as geochemical indices, highlighting the need for extra attention to the concentrations of Cu, Cr and Sb. Multivariate data analysis was crucial in determining a possible anthropogenic contribution in the region. Principal component analysis (PCA) showed that Fe was the chemical element with the greatest contribution to the chemical composition of the PTS, mainly associated with natural sources, such as soil resuspension. Meanwhile, the concentration of Cu, Fe, Mn, and Pb indicated anthropogenic influence from traffic and industrial activities. During the dry and rainy seasons, PCA showed variation in the relative weight of the metals, but maintained the distinction between natural and anthropogenic sources. Hierarchical cluster analysis (HCA) consistently grouped the samples, separating sets influenced by industrial/port activities from those of natural origin. This analysis confirmed the correlation between Cu, Mn, and Sb as markers of anthropogenic impact. Together, PCA and HCA reinforced the identification of the main emission sources in the studied region. Finally, this work may assist the corresponding agencies in more effective air quality monitoring in the region. Editora / Evento / Instituição: Universidade Federal da Bahia Tipo: Dissertação

Estudo teórico-computacional dos mecanismos eletrocatalíticos da oxidação da água por complexos de cobre(II) com ligantes macrocíclicos.

2026-02-26T10:54:41Z

Título: Estudo teórico-computacional dos mecanismos eletrocatalíticos da oxidação da água por complexos de cobre(II) com ligantes macrocíclicos. Autor(es): Neves, João Pedro Costa Sarno Primeiro Orientador: Alves, Tiago Vinícius Abstract: In a contemporary world marked by environmental imbalance, the Energy Transition arises as a solution to mitigate the emission of pollutants from fossil fuels burning. Following this scenario, a promising alternative is, for example, the H2, whose production via water electrolysis faces challenges related to its anodic half reaction, thus evoking the use of catalysts -- e.g. copper(II) complexes bearing macrocyclic ligands -- that remain in constant improvement. For this, it's necessary to elucidate this mechanism, which means to identify the key intermediates and steps for reaction kinetics. Therefore, by means of computational tools, the present work focused on the theoretical study of the water oxidation's electrocatalysis by the coordination complex [Cu(14-TMC)]+2, based on experimental evidence to which the results yielded good correspondence. In this case, the O-O bond formation proceeds through a water nucleophilic attack coupled with a single electron transfer to the metal center or, alternatively, through a crossing point between quartet and doublet potential energy surfaces. Going further, the results of macrocyclic shrinkage were also investigated through [Cu(12-TMC)]2+'s catalysis. Despite of the similar values in terms of energy barrier, this ligand enables the coordination of two water molecules, which impacts the course of reaction. The results, based on electronic and structural fundaments, shed a light on the rational design of ligands aiming better catalytic performance for H2 production. Editora / Evento / Instituição: Universidade Federal da Bahia Tipo: Dissertação

Determinação multielementar em amostras de açúcar empregando a espectrometria de fluorescência de raios-X por dispersão de energia após procedimento de diluição

2026-02-20T11:19:36Z

Título: Determinação multielementar em amostras de açúcar empregando a espectrometria de fluorescência de raios-X por dispersão de energia após procedimento de diluição Autor(es): Matos, Eloá Veiga Alves Primeiro Orientador: Teixeira, Leonardo Sena Gomes Abstract: Sugar is widely consumed and can represent a route of exposure to potentially toxic metals, making it essential to monitor its contamination to ensure food safety and public health. This study evaluated samples of white, demerara, and refined sugars for the presence of Co, Cr, Cu, Ni, and Zn using energy-dispersive X-ray fluorescence spectrometry (EDXRF). The samples were diluted in nitric acid solution and applied directly to the instrument’s sample holders for measurement of analytical signals. Calibration was performed using analyte standards prepared in sucrose, ensuring matrix matching and external calibration. The calibration curves showed good linearity, with limits of detection of 0.30, 0.40, 0.40, 0.30, and 0.60 mg kg⁻¹ for Co, Cr, Cu, Ni, and Zn, respectively. The addition and recovery tests yielded results between 82% and 108%, and the relative standard deviation (RSD) was below 7% in both intraday and interday evaluations. Concentrations obtained by EDXRF were compared with those determined by inductively coupled plasma optical emission spectrometry (ICP OES) after microwave-assisted acid digestion, with no statistically significant differences observed between the methods. The average concentrations for Co, Cr, Cu, Ni, and Zn ranged from 0.89 to 1.63 mg kg⁻¹, 2.10 to 3.66 mg kg⁻¹, 1.02 to 1.93 mg kg⁻¹, 1.23 to 1.85 mg kg⁻¹, and 2.66 to 4.04 mg kg⁻¹, respectively. The risk assessment indicated that the detected levels do not pose toxicological, carcinogenic, or non-carcinogenic hazards, suggesting that sugar consumption does not pose long-term health risks associated with the evaluated elements. Editora / Evento / Instituição: Universidade Federal da Bahia Tipo: Dissertação