Juliana L. Paes

Aplicação de ozônio contra Sitophilus zeamais e Tribolium castaneum em milho armazenado

The main goal of this work was to assess the susceptibility of adults of Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae) and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and the physiological quality of maize grains subjected to ozone treatment in different grain layers. PVC cages 3.0 cm high and 15.0 cm diameter were built with their bottom and cover closed with organza-like cloth; the cages were placed in cylindrical containers of PVC with 20 cm diameters and 100 cm heights and connections for injection and exhaustion of the ozone gas. Insects and maize grains were subjected to a modified atmosphere with 50 mg kg-1 ozone injected at a flow of 8.0 L min-1 through a connection at the bottom of the container (plenum) for different exposure times. Sitophilus zeamais was the most susceptible species regardless of its distribution in the grain mass. The exposure periods required to achieve 95% control of adults of S. zeamais and T. castaneum were 23.76 and 64.19 h respectively, when distributed near the ozone injection; overall the treatments with atmosphere modified by ozone injection at 50 mg kg-1 did not affect the physiological quality of maize grain.

Influência da temperatura da massa de grãos sobre a toxicidade do ozônio a Tribolium castaneum

Considering that the grain temperature may influence the exposure time of the fumigants, the present study was carried out to investigate the influence of increasing temperatures of the grain mass (20, 30, 35 and 40 oC) on the exposure time to ozone required to kill 50 and 95% of adult insects of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). Maize grains were distributed in cylindrical polyvinyl chloride recipients having connections for gas injection and exhaustion. The insects held in cages were placed at the median height of the grain mass in each recipient, which was then fumigated with ozone at the concentration of 50 ppm. The lethal times (LT50 and LT95) for adult insects of T. castaneum were reduced by increasing grain temperature, from 20 to 30 oC; however, at 35 oC the lethal times were not reduced compared with lower temperatures; but at 40 oC the exposure time decreased again, resulting in lower LT95.

Diffusion and sorption of allyl isothiocyanate in the process of fumigation of maize

The purpose of this work was to evaluate the transport of allyl isothiocyanate (AITC) by means of the sorption mechanism and the diffusion of AITC through maize grains. The experimental procedure to study the sorption mechanism was conducted by injection of AITC in glass flasks containing the grains. Kinetic models of zero, first and second order were fitted to AITC concentration data, with the purpose of determining the sorption rate (k). For the study of diffusion, a prototype was utilized in which the components are a gas chamber and a cylindrical column in which the grains were stored. At the interval of 110 min, samples in the chamber and in the column were collected, which were immediately injected into the gas chromatograph. In order to determine the effective diffusion coefficient (Def) of AITC through maize grains, the term referring to the sorption rate was added to the diffusion equation. The kinetic model of the first order was the one that best fitted the experimental data for the sorption mechanism, and k was 6.26 x 10-4 s-1. The Def of AITC through grains was 7.2 x 10-3 cm2 s-1. It was concluded that the transport of AITC through maize grains is slow, due to the low value of Def and high sorption rate of this component by the grains.

Soybean storage in bag type silos

Avaliaram-se as principais alteracoes qualitativas de soja armazenada em silos tipo bolsa e do oleo bruto extraido de soja com teores de agua de 17,4% e 13,3%, armazenada em dois silos tipo bolsa, por 180 dias. Realizaram-se amostragens no dia do enchimento das bolsas, aos 30; 90 e 180 dias de armazenamento. Analisaram-se o teor de agua, a condutividade eletrica, o percentual de germinacao, a massa especifica aparente da soja, alem do teor de acidos graxos livres e o indice de peroxido do oleo bruto extraido dela. Os teores de agua da soja armazenada umida e seca mantiveram-se proximos dos valores obtidos no inicio do periodo de armazenamento. Observou-se tendencia de elevacao da condutividade eletrica e decrescimo do percentual de germinacao somente na soja umida, principalmente apos 90 dias de armazenamento. Nao foi verificado decrescimo da massa especifica aparente do material armazenado umido e seco. Com relacao aos parâmetros qualitativos do oleo bruto, observou-se que os valores obtidos se mantiveram abaixo do limite maximo exigido pela legislacao para a comercializacao de oleo bruto de soja. Pode-se concluir que os silos tipo bolsa representam alternativa viavel do ponto de vista qualitativo para armazenagem de soja, e esse tipo de estrutura nao ocasiona alteracoes qualitativas significativas no oleo bruto obtido desse material, em condicoes similares aquelas deste estudo.

Computational Study of Anaerobiosis Acceleration in Hermetic Storage of Maize using Oxygen Depletion

Hermetic storage of grains has been used to control the infestation of pests and to preserve grain quality. The anaerobiosis process occurs when the oxygen concentration tends to zero due to grain respiration. The silobag is a flexible hermetic storage system of strategic importance in Brazil. Besides its flexibility, holes and similar accidental damages may occur and compromising the modified atmosphere. Low oxygen concentration may be achieved and maintained using oxygen depletor devices. These devices can be disposed at the bottom of the silobag in several positions along its axial direction. A computational study is presented to verify the viability of an oxygen depletor to accelerate the anaerobiosis of the grain mass of maize. The mathematical model considers both oxygen diffusion flux and its consumption rate due to respiration in unsteady state. The numerical model was implemented using the finite volume method in body fitted coordinates. Oxygen concentration as a function of time and position was obtained by simulation and the anaerobiosis time was verified to be faster when oxygen depletor was used. The computation model can be as a tool to design the optimal distribution of oxygen depletor devices into the silobag and to calculate the anaerobiosis time.

Avaliação do potencial de uso de biofertilizante de esterco bovino resultante do sistema de manejo orgânico e convencional da produção de leite.

Objetivou-se avaliar o potencial de utilizacao como adubo orgânico do biofertilizante, resultante da biodigestao anaerobica de dejetos de bovinos de leite, sob sistema orgânico (DBSO) e convencional (DBSC) de producao. Utilizaram-se oito prototipos de biodigestores abastecidos com os dejetos de bovinos. O delineamento experimental foi o inteiramente casualizado, com 4 repeticoes para cada tratamento. Apos o processo de biodigestao anaerobica foram realizadas analises quimicas, fisico-quimicas e biologicas, de acordo com a Resolucao CONAMA 375/06. Os biofertilizantes oriundos de DBSO e DBSC apresentaram um teor de carbono minimo para serem considerados fertilizantes orgânicos, com valores de 392,4 e 411,9 g kg-1, respectivamente. A biodigestao anaerobica elevou o pH e reduziu a condutividade eletrica (CE) no material efluente, apresentando diferenca estatistica entre os dois tratamentos. Os teores de Mg, K e Fe foram superiores nos biofertilizantes de DBSO e os de Mn, Cu, Zn e Ba foram maiores nos biofertilizantes de DBSC. No biofertilizante oriundo de DBSC o teor de Cd ficou acima do permitido por lei para fertilizantes orgânicos. Portanto, os sistemas de producao de leite influenciam nas caracteristicas quimicas e fisico-quimicas do biofertilizante produzido. O esterco produzido por bovinos sob sistema orgânico de producao de leite demonstrou maior potencial de uso como adubo orgânico quando comparado ao esterco oriundo do manejo convencional.