Real-Time Monitoring of Nitrogen Oxides Emission Factors Using Sensors in the Exhaust Pipes of Heavy Vehicles in the Metropolitan Region of Rio de Janeiro

The Metropolitan Region of Rio de Janeiro is one of the most populous in Brazil, besides being one of the most important routes for marketing goods through heavy vehicles. This type of vehicle is the main source of nitrogen oxides (NOx) emission into the atmosphere. To assess NOx emission factors, this pilot study used sensors to monitor in real-time the exhaust of 9 trucks from July to September 2022. To the best of our knowledge, this is the first study carried out in the city using low-cost sensors. Although there is legislation to reduce the emission of pollutants from the vehicle fleet, the results showed that 7 out of 9 trucks, exceeded the stipulated limits, reaching 6 g kWh-1. Furthermore, carrying out the maintenance of the engine of one of the vehicles decreased 60% of the NOx emission, even being an old vehicle. Thus, with this data, it was verified that the sensor performed excellently in monitoring NOx, demonstrating robust performance. This pilot study is part of a project that aims to make a long-term study of NOx emissions factors from heavy-duty diesel vehicles using sensors and other parameters.