Document Detail

Evolution of the magnitude and spatial extent of the weekend ozone effect in California's South Coast Air Basin, 1981-2000.
MedLine Citation:
PMID:  12880069     Owner:  NLM     Status:  MEDLINE    
Since the mid-1970s, ozone (O3) levels in portions of California's South Coast Air Basin (SoCAB) on weekends have been as high as or higher than levels on weekdays, even though emissions of O3 precursors are lower on weekends. Analysis of the ambient data indicates that the intensity and spatial extent of the weekend O3 effect are correlated with-day-of-week variations in the extent of O3 inhibition caused by titration with nitric oxide (NO), reaction of hydroxyl radical (OH) with nitrogen dioxide (NO2), and rates of O3 accumulation. Lower NO mixing ratios and higher NO2/oxides of nitrogen (NOx) ratios on weekend mornings allow O3 to begin accumulating approximately an hour earlier on weekends. The weekday/weekend differences in the duration of O3 accumulation remained relatively constant from 1981 to 2000. In contrast, the rate of O3 accumulation decreased by one-third to one-half over the same period; the largest reductions occurred in the central basin on weekdays. Trends in mixing ratios of O3 precursors show a transition to lower volatile organic compound (VOC)/NOx ratios caused by greater reductions in VOC emissions. Reductions in VOC/NOx ratios were greater on weekdays, resulting in higher VOC/NOx ratios on weekends relative to weekdays. Trends in VOC/NOx ratios parallel the downward trend in peak O3 levels, a shift in the location of peak O3 from the central to the eastern portion of the basin, and an increase in the magnitude and spatial extent of the weekend O3 effect.
Eric M Fujita; William R Stockwell; David E Campbell; Robert E Keislar; Douglas R Lawson
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Journal of the Air & Waste Management Association (1995)     Volume:  53     ISSN:  1096-2247     ISO Abbreviation:  J Air Waste Manag Assoc     Publication Date:  2003 Jul 
Date Detail:
Created Date:  2003-07-25     Completed Date:  2003-08-08     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9503111     Medline TA:  J Air Waste Manag Assoc     Country:  United States    
Other Details:
Languages:  eng     Pagination:  802-15     Citation Subset:  IM    
Division of Atmospheric Sciences, Desert Research Institute, University and Community College System of Nevada, Reno, Nevada 89512, USA.
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MeSH Terms
Air Pollutants / analysis*
Nitrogen Oxides / analysis*
Organic Chemicals
Oxidants, Photochemical / analysis*
Ozone / analysis*
Reg. No./Substance:
0/Air Pollutants; 0/Nitrogen Oxides; 0/Organic Chemicals; 0/Oxidants, Photochemical; 10028-15-6/Ozone

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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