RESUMO
One of the quality control parameters of ethanol fuel is pH, established by the Brazilian standard ABNT NBR 10891, whose scope is specific for hydrated ethanol fuel, and by the American standard ASTM D 6423, which focuses on anhydrous ethanol fuel. This study presented a modified and optimized structure using a single solvent, both for the glass electrode and the external reference electrode, to minimize the presence of the liquid junction potential for measuring the pH of hydrated ethanol fuel. The Box-Behnken design enabled us to determine the optimal condition expected for the new measurement system, which was compared with the systems proposed by the standard references and the turning range of acid-base indicators using parametric and nonparametric tests. The results revealed that the pH values obtained by the different systems are statistically different, and that only the values obtained by this proposal are suitable for the pH range found by the indicators. The optimized electrode presented an adequate response sensitivity to the Nernst equation, having an operational behavior adequate for the modified and optimized glass electrode for pH measurements in hydrated ethanol fuel.
Assuntos
Etanol , Etanol/química , Eletrodos , Concentração de Íons de Hidrogênio , BrasilRESUMO
To access the sources of air pollutants is crucial to control atmospheric pollution in urban areas, minimizing human exposure. Particulate matter is a pollutant of great concern making its chemical and morpho-structural characterization of enormous importance. The present work aims at the characterization of atmospheric PM10 and PM2.5. Data of the aerosol mass concentration was correlated by multivariate analysis with water-soluble ion fraction composition accessed by ion chromatography (IC), as well as with meteorological information and air mass backward trajectories. The gravimetric analysis presented average values 3 to 4 times higher than the guide values recommended by the World Health Organization (WHO). A morpho-structural analysis by SEM/FEG coupled to EDS was also carried out identifying the coarse fraction elements from minerals and from soil resuspension organic spherical particles that originated from combustion processes as well as Ti, associated with long-distance transportation. In the fine fraction, Zn with origin probably in tires and vehicle brakes was found. These origins were confirmed by the air masses' backward trajectories obtained by the HYSPLIT model (NOAA). This study contributes to a better understanding of the complex composition of the particulate material in the atmosphere of Araraquara City, resulting from the combination of local and long-distance sources, and serves as a basis for the comparison with future studies related to the air quality at this and other regions in Brazil and in the world.
Assuntos
Poluentes Atmosféricos , Poluição do Ar , Aerossóis/análise , Poluentes Atmosféricos/análise , Poluição do Ar/análise , Brasil , Monitoramento Ambiental , Humanos , Tamanho da Partícula , Material Particulado/análise , Estações do AnoRESUMO
The importance of studying the atmospheric pollution due to its effects on human health and other ecosystems, the inexistence of national production of equipment for air sample collection, and the high cost of the imported equipment (especially in developing countries) led the authors of the present work to construct a low-cost Gent type sampler. The construction of the sampler was carried out by combining low-cost materials with good mechanical strength (such as nylon 6.0), hydraulic piping PVC, and the use of a 3D printer. The innovation of the present work is the employment of a 3D printer using ABS polymer to create the grids that cannot be machined. In addition to the sampler, the system is composed of a vacuum pump, a gas meter, and a rotameter. The total cost of the sampling system amounted at about 1200 USD, and the cost of the manufactured Gent type sampler did not reach 100 USD. The results obtained while using this set for sampling atmospheric aerosol for a period of 11 months were compared with the mass concentration of PM10 obtained from the official environmental company, CETESB of São Paulo State, Brazil, showing good correlation with those from CETESB - which confirmed its effectiveness and suitability for use. The low cost, easy operation, and versatility of the built Gent type sampler enable its use for scientific and academic purposes. The equipment can be useful in environmental monitoring networks, in low-income regions, and as an instrument for environmental education used in universities.