Meteorological conditions of the winter-time distribution of nitrogen oxides in Poznan: A proposal for a catalog of the pollutants variation

This study used a 13-year series of hourly and daily data collected over the winter period to determine the temporal distribution and variability of nitrogen oxides in the ground atmosphere of a city. The study objective was to distinguish the types of diurnal variation of the analyzed air pollutants and assess them depending on the changes in meteorological conditions in 2005-2018. The highest daily levels of nitrogen oxides were recorded by sensors in the morning, between 7 am and 9 am, and in the evening, between 5 pm and 8 pm. Standardized hourly concentrations of NO2 > 200 mu g m(-3) in 2005-2018 were recorded on several occasions between 6 pm and 12 am. Six types of diurnal variation of the analyzed nitrogen oxides were distinguished, in which the highest levels were recorded at different times of the day. The highest levels of nitrogen oxides were in types C1 and C2, and the lowest were in types B1 and B2, with the most significant difference being in the NO concentration. There was a significant relationship between the nitrogen oxides concentration in the types of diurnal variation and meteorological indicators, with wind speed having the greatest impact on the nitrogen oxides concentration.