RESUMO
This study was designed to understand the dissipation of fipronil, cypermethrin, and tebuconazole in green onions and mustard greens grown in Central Vietnam. A field trial on ca. 400 m2 was implemented for two months with three different cropping regimes (natural plot-fully exposed to natural conditions; bed plot-fenced in by plastic sheets with an open roof; and protected plot-fully covered by plastic sheets) for each vegetable. A first-order kinetic model was successfully employed to interpret the dissipation data of each studied pesticide. A comparing the dissipation rate constants obtained under the same crop and growing regime between chemicals suggested that, among the chemicals examined, fipronil dissipated most readily. The pesticides were also proven to be more persistent in crops grown in protected plots than those grown in natural plots. The half-lives for fipronil, cypermethrin, and tebuconazole fluctuated, occurring at 0.4-2.2 days, 2.0-6.0 days, and 0.9-3.3 days, respectively.
RESUMO
Biopolymer template synthesis has attracted extensive interest for fabricating highly porous metal oxide nanostructures. In this report, a green template-based approach for the synthesis of three-dimensional (3D) NiO nanostructures assembled from porous NiO nanoplates is introduced using a konjac glucomannan (KGM) template. The Ni-KGM composites, which were formed by the immersion of KGM nanofibrils in nickel nitrate solution, were annealed in air at 600 °C to obtain the highly porous NiO nanoplates. The KGM nanofibrils were used as a sacrificial template, which was combusted at a high temperature for the formation of the porous nanostructures. The gas sensor properties of the porous NiO architecture were systematically investigated with four reduced gases including hydrogen sulfide, ammonia, carbon monoxide and hydrogen. The results indicate that the porous NiO nanoplates show a good detection of hydrogen sulfide with a rapid response and recovery speed at low concentrations.
