| dc.description.abstract | The study examined weekdayeweekend differences in ozone, NOx (NO and NO2) and VOC concentrations
in Santiago, Chile, from 1999 to 2007. The results provide evidence for the occurrence of an
atmospheric phenomenon that produces higher ozone concentrations during weekends despite lower
concentrations of ozone precursors. This phenomenon is known as the weekend effect (WE).
The overall ozone decrease since the spring of 2004 was a consequence of the implementation of
several urban pollution control measures. Although these measures caused a decline in the number of
days that exceed the national standard from two-thirds to one-third of summer days, the WE, which
became statistically significant beginning in September 2004, could not be eliminated. Furthermore,
VOC/NOx ratios decreased during the same period (2004), especially in the most industrialized area of
Santiago. Similarly, under these regimes, the VOC/NOx ratios were higher on Sundays than on weekdays
and caused higher ozone concentrations on Sundays. | |
