ISSN:
1573-0662
Keywords:
Tropospheric ozone
;
photochemistry
;
nitrogen oxides
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Geosciences
Notes:
Abstract The mixing ratios for ozone and NOx (NO+NO2) have been measured at a rural site in the United States. From the seasonal and diurnal trends in the ozone mixing ratio over a wide range of NOx levels, we have drawn certain conclusions concerning the ozone level expected at this site in the absence of local photochemical production of ozone associated with NOx from anthropogenic sources. In the summer (June 1 to September 1), the daily photochemical production of ozone is found to increase in a linear fashion with increasing NOx mixing ratio. For NOx mixing ratios less than 1 part per billion by volume (ppbv), the daily increase is found to be (17±3) [NOx]. In contrast, the winter data (December 1 to March 1) indicate no significant increase in the afternoon ozone level, suggesting that the photochemical production of ozone during the day in winter approximately balances the chemical titration of ozone by NO and other pollutants in the air. The extrapolated intercept corresponding to [NOx]=0 taken from the summer afternoon data is 13% less than that observed from the summer morning data, suggesting a daytime removal mechanism for O3 in summer that is attributed to the effects of both chemistry and surface deposition. No significant difference is observed in the intercepts inferred from the morning and afternoon data taken during the winter. The results contained herein are used to deduce the background ozone level at the measurement site as a function of season. This background is equated with the natural ozone background during winter. However, the summer data suggest that the background ozone level at our site is elevated relative to expected natural ozone levels during the summer even at low NOx levels. Finally, the monthly daytime ozone mixing ratios are reported for 0≤[NOx]≤0.2 ppbv, 0.3 ppbv≤[NOx]≤0.7 ppbv and 1 ppbv≤[NOx]. These monthly ozone averages reflect the seasonal ozone dependence on the NOx level.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00053773
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