Modeling the Weekend Effect in the Northeastern Iberian Peninsula
The chemistry of ozone (O3) and its two main precursors, nitrogen oxides (NOx) and volatile organic compounds (VOCs) represents one of the major fields of uncertainty in atmospheric chemistry. The ozone weekend effect refers to a tendency in some areas for ozone concentrations to be higher on weekends compared to weekdays, despite emissions of VOCs and NOx that are typically lower on weekends due to different anthropogenic activity. This phenomenon was first reported in the United States in the 1970s (Cleveland et al., 1974; Lebron, 1975) and has been since reported mainly in the U.S. and Europe. Higher weekend ozone tends to be found in urban centers, while lower weekend ozone is found in downwind areas. Altshuler et al. (1995) have suggested that the weekend effect is related to whether ozone formation is VOC- or NOx-sensitive, with higher weekend ozone occurring is VOC-sensitive areas. Despite this, there is a high uncertainty in the causes of the weekend effect, and six hypothesis have been set (CARB, 2003): (1) NOx reduction; (2) NOx timing; (3) carryover near the ground; (4) carryover aloft; (5) increased weekend emissions; (6) increased sunlight caused by decreased soot emissions.
KeywordsWeekend Effect Waste Management Association Precursor Emission Traffic Profile Downwind Area
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