Exploring the interaction between O3 and NOx pollution patterns in the atmosphere of Barcelona, Spain using the MCR–ALS method

• The behaviour & patterns of O3 and NOx over the three years are explored.
• The MCR–ALS method is used to analyse NO, NO2 and O3 simultaneously.
• Interactions among the pollutants are described with MCR–ALS profiles.
• The vehicular pollution is found to be the major source for O3 and NOx.

This work focuses on understanding the behaviour and patterns of three atmospheric pollutants namely, nitric oxide (NO), nitrogen dioxide (NO2), and ozone (O3) along with their mutual interactions in the atmosphere of Barcelona, North Spain. Hourly samples were collected for NO, NO2 and O3 from the same city location for three consecutive years (2010–2012). The study explores the seasonal, annual and weekday–weekend variations in their diurnal profiles along with the possible identification of their source and mutual interactions in the region. Multivariate Curve Resolution–Alternating Least Squares (MCR–ALS) was applied to the individual datasets of these pollutants, as well as to all of them simultaneously (augmented mode) to resolve the profiles related to their source and variation patterns in the atmosphere. The analysis of the individual datasets confirmed the source pattern variations in the concerned pollutant's profiles; and the resolved profiles for augmented datasets suggested for the mutual interaction of the pollutants along with their patterns variations, simultaneously. The study suggests vehicular pollution as the major source of atmospheric nitrogen oxides and presence of weekend ozone effect in the region.