RESUMO No presente trabalho foi realizada a estimativa das emissões dos gases de efeito estufa (CO2eq), monóxido de carbono (CO), óxido de nitrogênio (NOx), material particulado (MP), aldeído (RCHO) e hidrocarboneto não metano (NMHC) dos veículos licenciados nos cinco primeiro meses do ano de 2020 no Brasil. Os resultados foram comparados com as emissões veiculares da frota licenciada no mesmo período do ano de 2019 a fim de verificar o impacto da pandemia de COVID-19 nos referidos licenciamentos, nas emissões e, consequentemente, na qualidade do ar do país. Os resultados apontaram redução de 14% nas emissões dos gases de efeito estufa, com diminuição observada para todos os veículos, exceto para os caminhões semipesados, que tiveram incremento nas emissões de gases de efeito estufa de 12,8%. Os demais poluentes também reduziram, em 12,5% para o CO, em 29,6% para o NOx, em 24,1% para o MP, em 21,5% para o RCHO e em 16,3% para o NMHC. Por fim, quanto ao total de poluentes acumulados, entre todos os veículos analisados, os únicos que tiveram aumento nas emissões em relação a 2019, de 2,1%, foram as motocicletas com tecnologia flexfuel, que são abastecidas preferencialmente com etanol hidratado. Com isso, pôde-se concluir que a pandemia da COVID-19, por meio das medidas de restrição e isolamento social adotadas no país para frear a transmissão da doença, impactou positivamente a qualidade do ar no Brasil no período analisado.

ABSTRACT The estimated emissions of greenhouse gases (CO2eq), carbon monoxide (CO), nitrogen oxide (NOx), particulate matter (PM), aldehyde (RCHO) and non-methane hydrocarbon (NMHC) from vehicles licensed in the first five months of 2020 in Brazil were calculated in the present study, and the results compared with vehicular emissions from the licensed fleet in the same period of the year 2019, in order to verify the impact of the COVID-19 pandemic on these permits, emissions and, consequently, air quality in the country. The results showed a 14% reduction in greenhouse gas emissions, with a decrease observed for all vehicles, except for semi heavy trucks, which had a 12.8% increase in GHG emissions. The other pollutants also decreased, being 12.5% for CO, 29.6% for NOx, 24.1% for PM, 21.5% for RCHO, and 16.3% for NMHC. Finally, in relation to the total accumulated pollutants, among all vehicles analyzed, the only ones that had a 2.1% increase in emissions in relation to 2019 were the motorcycles with flexfuel technology, which are preferably fueled with hydrated ethanol. Thus, it was concluded that the COVID-19 pandemic, through the measures of restriction and social isolation adopted in the country to curb the transmission of the disease, had a positive impact on air quality in Brazil during the analyzed period.

BaCeO3-based ceramics are ionic and electronic conductors that can be applied to oxygen sensors, solid oxide fuel cells and oxygen permeable membranes. However, the low chemical stability at high temperatures of these materials motivates studies involving doping of A and/or B sites of the perovskite structure. In this context, the present work aimed to synthesize a new BaCe0.8Pr0.05Cu0.15O3-δ material using the chemical route of complexation which combines EDTA-Citrate with pH variation. The powders obtained at pH 3 or 11 and calcined up to 900 ºC are thermally unstable. The cubic perovskite BaCe0.8Pr0.05Cu0.15O3-δ with crystallite size between 99.4 nm and 131.6 nm was obtained along with barium carbonate traces. In the powders calcined at 1000 ºC the pH increase decreases the amount of barium carbonate (17.3% to pH 3, 3.4% to pH 7 and 1.8% to pH 11), but increases the size of grains with irregular shapes.