Efraim Lázaro Reis

Avaliação de contaminação por mercúrio em Descoberto, MG

Mercury is a chemical element considered unessential to any metabolic process; however, it is easily accumulated in most organisms. It is naturally found in both organic and inorganic forms in solid, liquid and vapor states. Its biogeochemical cycle involves processes occurring in the soil, water and the atmosphere. In 2002, elementary mercury was found in the city of Descoberto, Minas Gerais, Brazil, where 70 families live, and its origin may be related to gold exploration that happened in this region in the 19th century. In this work, three areas were chosen to identify a possible mercury contamination of water, soil, sediment and fish samples and to establish local reference values and counter-evidence of the data previously obtained. Based on the results, high mercury concentrations in soil (0.26 to 0.55 mg.kg-1), sediments (0.13 to 0.61 mg.kg-1) and water (< 0.2 to 2,10 µg.L-1) were verified.

Lixiviação do glyphosate e do imazapyr em solos com diferentes texturas e composição química: II. método analítico

Em razao das poucas de informacoes existente na literatura, sobre a mobilidade do glyphosate e do imazapyr, em solos de baixa atividade, comum em paises tropicais, foi conduzido, em laboratorio, um estudo sobre a mobilidade vertical desses herbicida s em dois solos com diferente s composicoes quimicas e fisicas. Para estudar essa mobilidade, foram utilizadas colunas de solo com diferentes alturas, as quais, apos aplicacao dos produtos na dose comerc ial de 4 L ha-1, foram submetida s a um regime hidrico de 40 mm h-1, por um periodo de 4 h. As analises dos residuos nas diferentes profundidades foram feitas utilizando-se os metodos voltametrico (polarografia) e HPLC, para o glyphosate e imazapyr, respectivame nte. Com base nos resultados, foi possivel concluir que: a) os metodos voltametrico, para o glyphosate, e HPLC, para o imazapyr, sao adequados para os estudos de identificacao e quantificacao de residuos em agua e solo; b) os limites de quantificacao dos residuos foram de 0,4 μg mL-1 e 5 μg L-1 para o glyphosate e o imazapyr, respectivamente; c) a taxa de recuperacao do glyphosate, nas amostr as de solo (76 e 78% para os solos de Vicosa e Sabara, respectivamente) foi menor que na amostra de agua (83%); d) a taxa de recuperacao do imazapyr, em agua e solo, foi proxima de 100%; e) a lixiviacao do glyphosate nos solos foi muito baixa; e f) o imazapyr apresentou alta lix iviacao, porem dif ere nciada entre os solos estudados, sendo essa maior no solo de tex tura franco -are nosa de Vicosa que no de argila de Sabara.

Volatilization of Ammonia Originating from Urea Treated with Oxidized Charcoal

Loss of N through volatilization of ammonia is the main limitation for agricultural use of urea. The aim of this study was to evaluate the volatilization of NH3 from urea granulated (Ug) or urea coated (Ur) with two oxidized charcoals produced by the oxidation of eucalyptus charcoal with 4.0 mol L-1 HNO3, followed by the post-treatment with NaOH (CHox) or without post-treatment with NaOH (CHox-OH). Ug and Ur were produced with 5, 10, 15 and 20% (m/m) of CHox or CHox-OH. The volatilization of NH3 was evaluated as 100 mg of N in the form of Ug or Ur applied to samples of a Hapludalf placed in a system with continuous and controlled air flow. The Ug with CHox-OH or with CHox was more effective in reducing the volatilization of NH3 than the Ur. It was estimated that the Ug with 16% of CHox or CHox-OH, with 39% N, reduced the volatilization by 40% in relation to urea without the additives. Results show that charcoal oxidized is an effective additive for reducing ammonia volatilization of urea.

Avaliação quimiométrica da distribuição de metais pesados em composto de lixo urbano domiciliar

The main obstacle to the use of compost from urban waste in agriculture is the presence of heavy metals. Once in the soil, their effect is accumulative and they may contaminate crops and water. The present study reports the evaluation of the chemical distributions of Cu, Pb, Mn and Zn in three different sized fractions (unsieved, 1,18mm) of compost, by means of a sequencial extraction procedure and a chemometric analysis of the total content of all metals in each fraction. The pattern recognition methods showed significant differences in total heavy metal contents for the different fractions. The finest one was the most contaminated. Meanwhile, this fraction presented lower amounts of metals in avaliable forms. This behavior can be attributed to the presence of metal particles in their elemental states in this fraction.

Fractal Dimension of Humic Acids as Influenced by Complex Formation

Abstract Among the tools available to explain the conformation of humic acids (HA), the fractal dimension (D) seems to be one of the most adequate. The aim of this study was to determine the conformational modifications of the HA particles in the absence and presence of Zn2+ and Cd2+, with the determination of the D value. The adsorption experiments were carried out with a commercial HA (Fukla AG) and HA extracted from SPODOSOL soils. The HA were characterized for their total C, H, and N content, E4/E6 ratios, IR-FTIR, and ash content. The metal concentration of Zn2+ and Cd2+ in the suspension was determined through atomic absorption spectrophotometer. The HA particles in diluted aqueous suspension were analyzed using turbidimetry, under varied experimental conditions, to calculate D. The addition of metals to the HA suspensions induced a decrease in the standard-deviation between replications and an increase of D values, revealing stabilization of the suspensions and a collapse of the HA structure during the formation of metal-organic complex. The results showed that the D values were able to represent the conformational changes of the HA-metal complexes.Abstract Among the tools available to explain the conformation of humic acids (HA), the fractal dimension (D) seems to be one of the most adequate. The aim of this study was to determine the conformational modifications of the HA particles in the absence and presence of Zn2+ and Cd2+, with the determination of the D value. The adsorption experiments were carried out with a commercial HA (Fukla AG) and HA extracted from SPODOSOL soils. The HA were characterized for their total C, H, and N content, E4/E6 ratios, IR-FTIR, and ash content. The metal concentration of Zn2+ and Cd2+ in the suspension was determined through atomic absorption spectrophotometer. The HA particles in diluted aqueous suspension were analyzed using turbidimetry, under varied experimental conditions, to calculate D. The addition of metals to the HA suspensions induced a decrease in the standard-deviation between replications and an increase of D values, revealing stabilization of the suspensions and a collapse of the HA structure during...

Características físico-químicas de ácidos húmicos em diferentes etapas da vermicompostagem

Samples of materials, collected at different stages of vermicompostaging, were submitted to extraction procedures of humic acids. Titration, termogravimetry (DTG), X-ray diffraction, spectrophotometry in the uv/visible and infrared techniques, were used in the study of these materials. The data from the potentiometry titration analysis were submitted to adjustment by non-linear regression, determining thus five values of pKas characteristic of five classes of titrable groups. In the DTG curves two stages can be observed, being the first one characteristic of the separation of aliphatic and/or alycyclic structures and the second of decomposition of aromatic structures. The X-ray diffraction technique exhibed marked differences in the results, mainly in the first three peaks, were a structural reorganization and a polymerization along the vermicompostaging process. The infrared spectra practically no differentiation between the samples. The values for the ratio E4/E6 found are in accordance with the characteristic values for humic acids, but do not supply information that can contribute to the elucidation of the structure and formation of these acids.

MCR-ALS aplicado no monitoramento quantitativo do processo de eletrodegradação da atrazina usando espectros UV : resultados comparativos com HPLC-DAD como um método de referência.

Electrodegradation of atrazine in water was performed using homemade (PA and PB) and purchased (PC) boron-doped diamond anodes. The degradation was monitored off-line by analyzing total organic carbon and high performance liquid chromatography with diode array detector (HPLC-DAD) and at-line by UV spectroscopy. The spectra were recorded every 2 min. The rank deficiency problem was resolved by assembling an augmented column-wise matrix. HPLC was employed to separate the original and byproducts degradation components. Aiming the same goal, multivariate curve resolution - alternating least squares (MCR-ALS) was applied to resolve the UV spectroscopic data. Comparison between HPLC and MCR-ALS separations is presented. By using MCR-ALS the spectra of atrazine and two byproducts were successfully resolved and the resulted concentration profiles properly represented the system studied. The ALS explained variance (R2) for PA, PB and PC was equal to 99.99% for all of them and the lack of fit for PA, PB and PC were 0.39, 0.34 and 0.54 respectively. The correlation (R) between the recovered and pure spectra were calculate for each electrodegradation, validating the MCR-ALS results. The average R was equal to 0.997. The spectral and concentration profiles described with this new approach are in agreement with HPLC-DAD results. The proposed method is an alternative to classical analyses for monitoring of the degradation process, mainly due to the simplicity, fast results and economy.

Multiparametric adjustment program of potentiometric titration curves of humic acids

Tendo em vista a dificuldade de determinacao dos pontos de inflexao na curva de titulacao potenciometrica de acidos humicos, por metodologias tradicionais, foi desenvolvido foi desenvolvido um programa na linguagem Delphi para ajuste multiparametrico de dados de titulacao potenciometrica. Para isso um processo iterativo para estimar as raizes de um polinomio, com base no metodo de Newton-Raphson, foi utilizado. Os dados das titulacoes potenciometricas de acidos humicos usados nas regressoes foram obtidos em um sistema automatizado de titulacao potenciometrica. O programa desenvolvido na linguagem Delphi permite maior versatilidade e facilidade de operacao, com uma interacao mais amigavel com o usuario. As curvas de titulacao potenciometricas ajustadas sobrepuseram-se quase que totalmente as curvas experimentais. Os valores de pKa e as percentagens de grupos titulaveis dos acidos humicos, parâmetros ajustaveis na regressao multiparametrica, apresentaram valores comparaveis com dados da literatura.

Pulp Mill Effluent Treatment Using Plasma Obtained by High Voltage Electrolysis

Effluents from pulp mills have a high organic load and can still contain high organic biorecalcitrant material that is harmful to the aquatic environment, even after undergoing biological treatment in effluent treatment plants. This study presents a novel treatment method tested on effluents (prior to and after biotreatment) from a Brazilian kraft pulp mill, based on hydroxyl radical production and hydrogen peroxide obtained by plasma generated by high-voltage electrolysis. These species present significant oxidation potential that could enable the complete breakdown of the organic matter. From the application of plasma to treat pulp mill effluent for a 7-hour period, it was obtained a chemical oxygen demand (COD) removal between 88.2 and 99.7%, total organic carbon (TOC) removal of 90.3 to 95.6%, and a color removal of 95.0 to 98.0%. The final pH of the treated effluent was 11.6 to 11.9. The results obtained in this study showed that the high-tension plasma treatment, applied on effluent from kraft pulp mills before and after biological treatment, can be an attractive alternative.

Modelling of Lead Migration from Electronic Waste to Mixtures of Kaolinite, Iron Oxides and Organic Matter

Improper disposal of electronic waste in the environment facilitates migration of heavy metals, especially lead, into the soil and can contribute to the bioavailability of this species. Based on a simplex-centroid mixture experimental design, small-scale tests were performed for incubation of printed circuit boards (PCBs) in mixtures containing organic matter (OM), kaolinite (KA) and iron oxides (IO) to verify lead migration. Regression equations were acquired and were adjusted to the obtained responses. Results showed high total content of Pb, ranging from 400 to 4000 mg kg-1, depending on the mixture and incubation time. Mobility and/or bioavailability of lead in the mixtures were evaluated by a three-step sequential extraction. The bioavailability factor (BF) was obtained from the ratio of the sum of exchangeable fraction (F1) and the organically bound fraction (F2) by F1, F2 and the residual fraction (F3) and the values of bioavailability factor for Pb, the heavy metal considered of greatest environmental concern in this study, ranged between 0.16 and 0.52.