Author(s)

R. Parra, E. Franco

Abstract

The Weekend Effect (WE) is a phenomenon that occurs in some urban areas, characterized by increased concentrations of O₃ and decreased emissions of its precursors (NO_x and VOC) during weekend days, in comparison to weekdays. The study of the WE is relevant for understanding the behavior of pollutants; and hence, for air quality control. We analyzed the hourly records of the period 2005–2012, from 8 stations of the air quality network from the Distrito Metropolitano de Quito (northern Andean region of Ecuador). Both for each station and year, 3 mean-daily profiles were obtained for CO, NO₂, PM_2.5 and O₃, corresponding to weekdays, Saturdays and Sundays. The CO, NO₂ and PM_2.5 profiles from Centro (historic center of Quito) and Belisario (center-north) stations, declined on Sundays. However the O₃ profiles were higher on Saturdays and Sundays. The O₃ 8-h mean concentrations of Sundays were higher in Belisario (19.7–31.1%) and Centro (11.7–18.4%), in comparison to weekdays. These results indicate the presence of the WE around these 2 stations, which probably are located in a VOC-limited region for photochemical O₃ production.

Keywords

Distrito Metropolitano de Quito, VOC-Limited Regime, NO_x-Limited Regime