Reduction of transport-related air pollution. A case study based on the impact of the COVID-19 pandemic on the level of NOx emissions in the city of Krakow

This article describes the impact of limiting human mobility related to the COVID-19 pandemic on the level of air pollution related to transport. The city of Krakow and the emission level of nitrogen oxides (NOx) were used as a case study. This article describes the air quality monitoring system in Krakow and the measurement results from the measurement station at Krasinskiego Avenue. The average values of the pollution level in April 2018–2020 were compared. For the selected range of data, a significance test was performed, which resulted in no grounds for rejecting the hypothesis of the equality of the mean levels of nitrogen oxides concentrations in the spring. The analysis takes into account the average monthly temperatures in the discussed years.