Podridão peduncular e qualidade de mangas 'Tommy atkins' procedentes do mercado atacadista de Campina Grande-PB

O Brasil destaca-se no cenário mundial como um dos maiores produtores de manga (Mangifera indica L.). No entanto, perdas significativas são observadas em todas as etapas da cadeia produtiva, sobretudo na comercialização varejista, sendo estas correlacionadas em quase sua totalidade à incidência de doenças fúngicas. Neste sentido, objetivou-se com este trabalho determinar a incidência natural de Lasiodiplodia theobromae, agente causal da podridão peduncular, e aspectos da qualidade pós-colheita de mangas 'Tommy Atkins', comercializadas no mercado atacadista da Empresa Paraibana de Abastecimento e Serviços Agrícolas (EMPASA) de Campina Grande-PB. Para a determinação da incidência natural da doença, coletaram-se 40 frutos no estádio de maturação 'de vez', de quatro diferentes estabelecimentos de comercialização, que foram encaminhados ao Laboratório de Fitopatologia (CCA/UFPB). Após sanificação, os frutos foram mantidos sob condições ambientes (28 ± 2 ºC e UR 75 ± 6%) por oito dias, determinando-se o aparecimento dos primeiros sintomas e sinais do patógeno. As características de qualidade foram determinadas através da coleta de 10 frutos de cada estabelecimento de comercialização da EMPASA. Os frutos foram transportados ao Laboratório de Biologia e Tecnologia Pós-Colheita (CCA/UFPB), onde foram avaliados quanto aos teores de Sólidos Solúveis (SS), Acidez Titulável (AT), Relação SS/AT e pH. Os dados foram submetidos à análise de variância, e as médias, comparadas pelo teste de Tukey, a 5% de probabilidade. A manga comercializada no mercado atacadista da EMPASA de Campina Grande apresentou baixo conteúdo de SS e elevada AT, caracterizando fruto no início da maturação. Os frutos apresentaram 88,9% de incidência natural de podridão peduncular no oitavo dia de armazenamento, o que compromete a qualidade do produto no varejo, constituindo-se em uma causa das elevadas perdas pós-colheita.

Potencialidades do dióxido de chumbo eletrodepositado como sensor potenciométrico

This paper proposes an experiment to be performed in both instrumental analysis and experimental physical-chemistry curricular disciplines in order to open options to develop challenging basic research activities. Thus the experimental procedures and the results obtained in the preparation of electrodeposited lead dioxide onto graphite and its evaluation as potentiometric sensor for H3O+ and Pb2+ ions, are presented. The data obtained in acid-base titrations were compared with those of the traditional combination glass electrode at the same conditions. Although a linear sub-Nernstian response to free hydrogen ions was observed for the electrodeposited PbO2 electrode, a good agreement was obtained between them. Working as lead(II) sensing electrode, the PbO2 showed a linear sub-Nernstian behavior at total Pb2+ concentrations ranging from 3,5 x 10-4 to 3,0 x 10-2 mol/L in nitrate media. For the redox couple PbO2/Pb(II) the operational slope converges to the theoretical one, as the acidity of the working solution increases.

Eletrodissolução de ligas de latão empregando sistemas de análise em fluxo para a determinação de cobre, zinco e chumbo por ICP-AES

An on-line electrodissolution procedure implemented in a flow injection system for determination of copper, zinc and lead in brasses alloys by ICP-AES is described. Sample dissolution procedure was carried out by using a PTFE chamber and a DC power supply with constant current. Solid sample was attached to chamber as anode and a gold tubing coupled in the chamber was used as cathode. An electrolytic solution flowing through the gold tubing closed the electric circuit with sample, in order to provide condition for electric dissolution when the DC power supply was switched on. The best results were achieved by using a 1.5 mol l-1 nitric acid solution as electrolyte and a 2.5 A current intensity. The procedure presented a good performance characterized by a relative standard deviation better than < 5% (n=5) and a sample throughput of 180 determinations per hour for Cu, Zn and Pb. Results were in agreement with those obtained by conventional acid dissolution (99% confidence level).

Avaliação da fitodisponibilidade de cádmio, chumbo e crômio, em soja cultivada em latossolo vermelho escuro tratado com fertilizantes comerciais

The aim of this work was to evaluate the availability of the toxic heavy metals: cadmium, lead and chromium, in soybean, from some fertilizers. Five fertilizers and soluble salts contend Cd, Pb and Cr were used. All the treatments were accomplished in vases of 2,5 L with application of two doses, 50 and 100 kg.ha-1 for the fertilizers and 25 and 50 kg.ha-1 for the salts.

Especiação de cobre e chumbo em sedimento do Rio Tubarão (SC) pelo método Tessier

The sequential extraction procedure proposed by Tessier and total digestion were applied for the analysis of sediment samples from Tubarão River. The recoveries were between 93.5 and 102.5% for Cu and 99.2 and 111% for Pb. The precision was tipically better than 6% for Cu and 3% for Pb. Comparison of the values obtained for the total digest with the sum of the extracted fractions showed that there were no significant losses in the extraction steps so that the method can be used for the monitoring availability and mobility of these analytes. According to ten points of sampling, was possible to determined the average of labiles phases (fractions 1 and 4) for Pb and Cu: 33.70% and 18.18%, respectively; and the inert phases (fraction 5- residual): 66.30% for Pb and 81.82% for Cu.

Emprego de planejamento fatorial para a otimização das temperaturas de pirólise e atomização de Al, Cd, Mo e Pb por ETAAS

This work describes a factorial design for the optimization of pyrolysis and atomization temperatures in ETAAS. As examples, Cd and Pb were determined using lower pyrolysis and atomization temperatures and Al and Mo with higher pyrolysis and atomization temperatures. Good results were obtained for Cd employing Rh (m o = 1.4 pg) as a permanent modifier with pyrolysis and atomization temperatures of 640 and 1500 °C, respectively. For Zr, W or Zr+W, the Cd pyrolysis and atomization temperatures were 500 and 1500 °C, respectively, with m o = 1.4 pg using Zr or W and 1.5 pg using Zr+W. The best results for Pb were those using Rh, Zr, W and Zr+Rh, obtaining characteristic masses of 42, 37, 34 and 36 pg, respectively. Pyrolysis and atomization temperatures of 910 and 1850 °C, respectively, were achieved for this metal. For Al, the best results were obtained when Zr or Zr+W were used. Mo was also tested as a possible permanent modifier for Al, but the results were not satisfactory. The results obtained for Mo without modifier were similar to those with conventional modifiers (Mg or Pd+Mg) and the results obtained using permanent chemical modifiers were not satisfactory. In all situations, the experiments were performed faster than those using the univariate procedure.

Adsorção de As, Cu, Pb e Cr na avaliação da capacidade de fixação de metais por resíduo de mineradoras de ferro

Two samples of residues from iron mining plants have been investigated for their retention capacity of As, Cu, Cr, and Pb. The sample with the higher content of iron oxides showed the highest capacity to retain metals. The adsorption affinity series changes from Pb>Cu>Cr~As to As>Pb>Cu>Cr or As>Cu>Cr>Pb, depending on the material and the concentration of the initial solution. In the competitive environment, the Pb adsorption decreases and the As, Cu and Cr adsorption increases. Sequential extraction procedures, carried out after adsorption batch experiments, showed that the most important adsorption process occurs in the oxide fraction and that the major part of the absorbed metal is remobilized from exchangeable and oxide fractions.

Avaliação do teor de metais em sedimento do rio Betari no Parque Estadual Turístico do Alto Ribeira: PETAR, São Paulo, Brasil

The subsoil of the Vale do Ribeira was the focus of mining industries for the exploration of lead, mainly inside the park - PETAR. Despite the fact that the exploration has ended, the environmental effects of those activities are still present, due to great amounts of heavy metals that are leached. Concentrations of pseudo-total and bioavailable metals were determined in sediment samples of the Betari River, using atomic absorption spectrometry. The results demonstrated that the sediments are contaminated by Pb, Zn and Cu. The findings can contribute to an efficient and environmentally and economically adequate management of the park, for the conservation and the protection of the area.

Solid phase extraction of iron and lead in environmental matrices on amberlite xad-1180/pv

A solid phase extraction procedure using Amberlite XAD-1180/Pyrocatechol violet (PV) chelating resin for the determination of iron and lead ions in various environmental samples was established. The procedure is based on the sorption of lead(II) and iron(III) ions onto the resin at pH 9, followed by elution with 1 mol/L HNO3 and determination by flame atomic absorption spectrometry. The influence of alkaline, earth alkaline and some transition metals, as interferents, are discussed. The recoveries for the spiked analytes were greater than 95%. The detection limits for lead and iron by FAAS were 0.37 µg/L and 0.20 µg/L, respectively. Validation of the method described here was performed by using three certified reference materials (SRM 1515 Apple Leaves, SRM 2711 Montana Soil and NRCC-SLRS-4 Riverine Water). The procedure was successfully applied to natural waters and human hair.

Preparação de amostra de fígado bovino e estudo de micro homogeneidade para a determinação de Cd E Pb por espectrometria de absorção atômica com atomização eletrotérmica e amostragem direta de sólido

This work describes a systematic study for bovine liver sample preparation for Cd and Pb determination by solid sampling electrothermal atomic absorption spectrometry. Samples were prepared using different procedures: (1) drying in a household microwave oven followed by drying in a stove at 60 ºC until constant mass, and (2) freeze-drying. Ball and cryogenic mills were used for grinding. Particle size, sample size and micro sample homogeneity were investigated. All prepared samples showed good homogeneity (He < 10) even for low sample mass, but samples dried in a microwave oven/stove and ground in a ball mill presented the best homogeneity.

Remoção de chumbo(II) em sistemas descontínuos por carvões ativados com ácido fosfórico e com vapor

Adsorption of heavy metal cations by activated carbon is dependent on the capacity of the material in promoting adsorption and the time needed to reach equilibrium. Carbon samples were previously activated either by phosphoric acid treatment at 400 ºC or by steam at 800 ºC. The results of Pb(II) adsorption by these activated carbons have shown that equilibrium was typically reached within the first 5 min of contact between carbon and metal solution, with a maximum adsorption capacity higher than 69 mg g-1 for the vapor-activated sample. Temperature influences the sorption capacity, which corresponds to an endothermic process. Lead(II) retention is more pronounced at high temperature and low pH.

Ensaios para determinar a (Bio)disponibilidade de chumbo em solos contaminados: revisão

Incidental ingestion of contaminated soils is a major route of Pb uptake by humans, especially by children. Lead speciation in soils controls its bioavailability. Bioavailability assessment requires the determination of the amount of absorbed lead if a contaminated soil is ingested. In vivo tests, which employ animals, are considered the best model to infer absorption of Pb. But they have some logistic limitations and several authors proposed in vitro methods, which simulate conditions of human digestion. Many of them present results which correlate with in vivo essays. Several authors consider in vitro tests a good and reliable alternative to infer lead bioavailability.

Estudo do comportamento do chumbo em latossolos brasileiros tratados com fosfatos: contribuições para a remediação de sítios contaminados

Phosphates have been used for lead immobilization in soils but the influence of soil type is not fully understood. In this work, lead chemical behaviour in two Brazilian latosoils (LA and LV) was studied via treatment with phosphates. The Pb concentration in Toxicity Characteristic Leaching Procedure (TCLP) solutions was decreased in all treatments. After treatment with H3PO4 the Pb concentration in the LA remained within the regulatory limit established by EPA. The ecotoxicological results with Daphnia pulex showed that this treatment reduced the lead bioavailability. Sequential extraction analyses showed that the lead was transferred from the most available to the residual fraction. Relevant decrease of soluble lead was observed in all phosphate treatments.

Determinação simultânea de As, Cd e Pb em amostras de água purificada para hemodiálise por espectrometria de absorção atômica com forno de grafite, após otimização multivariada baseada no uso de planejamento experimental

This paper reports the development of a methodology for simultaneously determining As, Cd and Pb, employing GF AAS with polarized Zeeman-effect background correction. In order to make the procedure applicable, the influence of pyrolysis and atomization temperatures and the amount of chemical modifiers were studied. Factorial and central composite designs were used to optimize these variables. Precision and accuracy of the method were investigated using Natural Water Reference material, Nist SRM 1640. Results are in agreement with certified values at the 95% confidence limit when the Student t-test is used. This methodology was used for quality control of purified water for hemodialysis.

Determination of Cd and Pb in fuel ethanol by filter furnace electrothermal atomic absorption spectrometry

A method was developed for quantification of Cd and Pb in ethanol fuel by filter furnace atomic absorption spectrometry. Filter furnace was used to eliminate the need for chemical modification, to stabilize volatile analytes and to allow the application of short pyrolysis step. The determinations in samples were carried out against calibration solutions prepared in ethanol. Recovery tests were made in seven commercial ethanol fuel samples with values between 90 and 120%. Limits of detection were 0.1 µg L-1 for Cd and 0.3 µg L-1 for Pb. Certified water samples (APS 1071, APS 1033, NIST 1643d, NIST 1640) were also used to evaluate accuracy and recoveries from 86.8% to115% were obtained.