An infection of the fungus Moniliophthora perniciosa in cocoa trees reduces productivity of the plant. In this study, the concentrations of mineral nutrients in healthy leaves and in leaves of vegetative broom of the cocoa plant were determined, and the relationship between the disease and the nutritional composition of the leaves was assessed. The samples were analyzed using the wet digestion method and the concentrations were determined by inductively coupled plasma optical emission spectrometry and the Kjeldahl method. Results indicate that leaves of vegetative broom have lower concentrations of Ca, Mg, S, Fe, Mn, and Ni than healthy leaves. Concentrations of P and Cu were lower in healthy leaves and higher in leaves of vegetative broom. In contrast, concentrations of K, N, and Zn were the same for both types of leaves. In short, plant-fungal interaction was reflected in the nutritional composition of the leaves, demonstrated by the differences in nutrient concentrations between healthy and infected leaf tissue.

Plant litter has several functions in a forest ecosystem. Studies about plant litter are of great importance to better understand and conserve ecological environments. The objective of this study was to investigate the concentration of metals (Fe, Co, Ca, Cu, Ni, Mg, Mn and Zn) in Caatinga plant litter in the southwest region of Bahia. Plant litter was collected in summer (January/2017) and winter (August/2017). Concentrations were determined by flame atomic absorption spectrometry (FAAS). The results were submitted to multivariate analysis, principal component analysis (PCA), and hierarchical cluster analysis (HCA). The average amount of plant litter found in January and August was 1190 and 1329 kg ha-1, respectively. The twigs fraction provided the largest amount of biomass to the plant litter since this deposition occurred in greater quantity in August, a period of drought. Metal concentrations (g kg-1) in the analyzed samples ranged from 1.39-257 (Fe), < limit of quantification (LOQ)-0.269 (Co), 0.0036-0.61 (Cu), 1.39-8.76 (Ca), 0.0022-0.56 (Ni), 0.137-1.52 (Mg), 0.033-1.91 (Mn) and 0.0022-0.8 (Zn). The multivariate analysis showed that the composition of plant litter is altered seasonally.

Este trabalho propõe o uso de degradação por foto-oxidação com radiação ultravioleta e H2O2 como técnica de tratamento de amostras para a determinação de Fe, Zn, Mn, Ni e Co a partir de chorume de aterro sanitário municipal usando espectrometria de absorção atômica com chama (FAAS). Três variáveis (pH, tempo de irradiação e concentração de tampão) foram otimizadas usando planejamento Doehlert e as proporções dos componentes da mistura submetida à irradiação ultravioleta (chorume, solução tampão e H2O2 30% v/v) foram otimizadas usando-se um planejamento de misturas com restrições. Usando as condições experimentais estabelecidas, este procedimento forneceu limites de detecção de 0,075; 0,025; 0,010; 0,075 e 0,041 µg mL-1, e os níveis de precisão, expressos como desvio padrão relativo (%RSD, 0,5 µg mL-1) foram 3,6; 1,8; 1,3; 3,3 e 1,7% pra Fe, Mn, Zn, Ni e Co respectivamente. Testes de recuperação foram realizados para avaliação da exatidão do procedimento e as recuperações encontradas estavam entre 92 e 106% para os metais estudados. Este procedimento foi aplicado nas amostras de chorume coletadas no município de Jequié, região sudoeste da Bahia, Brasil. Os resultados foram comparados com aqueles obtidos pelo procedimento de digestão em meio ácido. Não houve diferenças significativas entre os resultados obtidos nos dois métodos com base no teste t-pareado a um nível de confiança de 95%.

This work proposes the use of photo-oxidation degradation with UV radiation/H2O2 as sample treatment for the determination of Fe, Zn, Mn, Ni and Co in municipal solid waste landfill leachate by flame atomic absorption spectrometry (FAAS). Three variables (pH, irradiation time and buffer concentration) were optimized using Doehlert design and the proportions of mixture components submitted to UV radiation (leachate sample, buffer solution and H2O2 30%, v/v) were optimized using a constrained mixture design. Using the experimental conditions established, this procedure allows limits of detection of 0.075, 0.025, 0.010, 0.075 and 0.041 µg mL-1, and the precision levels expressed as relative standard (%RSD, 0.5 µg mL-1) were 3.6, 1.8, 1.3, 3.3 and 1.7%, for Fe, Mn, Zn, Ni and Co respectively. Recovery tests were carried out for evaluation of the procedure accuracy and recoveries were between 92 and 106% for the studied metals. This procedure has been applied for the analysis of the landfill leachate collected in Jequié, a city of the southwestern region of the State of Bahia, Brazil. The results were compared with those obtained by acid digestion. There was no significant difference between the results obtained by the two methods based on paired t-test at 95% confidence level.

Este trabalho propõe a otimização multivariada de um procedimento para determinação de cádmio em amostras de chorume usando-se espectrometria de absorção atômica com chama após a extração em fase sólida usando-se uma minicoluna empacotada com Amberlite XAD-4 modificada com ácido 3,4-diidróxibenzoico. As variáveis relacionadas à pré-concentração (pH, razão de amostragem e concentração do tampão) foram otimizadas usando-se planejamento Doehlert. Duas ferramentas para modelagem estatística (regressão por mínimos quadrados e redes neurais artificiais) foram aplicadas aos dados e seus desempenhos foram comparados. Procedimentos de digestão do chorume por aquecimento em meio ácido e por radiação ultravioleta foram avaliados sendo este último mais adequado para evitar a perda de Cd por volatilização. O procedimento desenvolvido apresentou um fator de enriquecimento de 9 vezes com limites de detecção e de quantificação (3sb) de 0,72 e 2,4 µg L-1, respectivamente, e precisão - expressa como porcentagem do desvio padrão relativo - de 4,0 e 6,4% (RSD%, n = 4 para 5,0 e 20,0 µg L-1, respectivamente). Testes de adição/recuperação de Cd foram realizados obtendo-se valores entre 97 e 112%. O procedimento foi aplicado na determinação de cádmio em amostras de chorume coletadas no aterro sanitário do município de Jaguaquara-BA, Brasil.

This work proposes the use of multivariate optimization as a procedure for cadmium determination in leachate samples via flame atomic absorption spectrometry after solid phase extraction using a minicolumn packed with Amberlite XAD-4 modified with 3,4-dihydroxybenzoic acid. The variables related with the preconcentration (pH, sampling flow rate and buffer concentration) were optimized using Doehlert design. Two statistical modeling tools (least squares regression and artificial neural networks) have been applied to the data and their performances were compared. Digestion procedures of the leachate by heating in acid medium and ultraviolet radiation were evaluated being the latter more appropriate to prevent loss of Cd by volatilization. The developed procedure has promoted an enrichment factor of 9, with detection and quantification limits (3sb) of 0.72 and 2.4 µg L-1, respectively, and precision - expressed as relative standard deviation percentage - of 4.0 and 6.4% (RSD%, n = 4 for 5.0 and 20.0 µg L-1, respectively). Addition/recovery tests for Cd were carried out and values between 97 and 112% were obtained. The procedure was applied for cadmium determination in leachate samples collected at the sanitary landfill of Jaguaquara-BA, Brazil.