 |
| Titel |
Weekly patterns of México City's surface concentrations of CO, NOx, PM10 and O3 during 1986–2007 |
| VerfasserIn |
S. Stephens, S. Madronich, F. Wu, J. B. Olson, R. Ramos, A. Retama, R. Muñoz |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 8, no. 17 ; Nr. 8, no. 17 (2008-09-05), S.5313-5325 |
| Datensatznummer |
250006366
|
| Publikation (Nr.) |
 copernicus.org/acp-8-5313-2008.pdf |
|
|
|
|
|
| Zusammenfassung |
| Surface pollutant concentrations in México City show a distinct pattern
of weekly variations similar to that observed in many other cities of the
world. Measurements of the concentrations of carbon monoxide (CO), nitrogen
oxides (NOx=NO+NO2), particulate matter smaller than 10 μm
(PM10), and ozone (O3) collected hourly over 22 years (1986–2007)
at 39 urban monitoring locations were analyzed. Morning concentrations of
CO, NOx, and PM10 are lower on Saturdays and even more so on Sundays,
compared to workdays (Monday–Friday), while afternoon O3 concentrations
change minimally and are occasionally even higher. This weekend effect is
empirical evidence that photochemical O3 production is NOx-inhibited,
and to the extent that emissions of CO are proportional to those of reactive
volatile organic compounds (VOCs), it is VOC-limited, at least in the urban
areas for which the monitoring stations are representative. The
VOC-limitation has increased in the past decade, due to decreases in the
concentrations of CO (and presumably VOCs) and consequent decreases in the
CO/NOx and VOC/NOx ratios. Enhancements of photolysis frequencies resulting
from smaller weekend aerosol burdens are not negligible, but fall short of
being an alternate explanation for the observed weekend effect. The strength
of the weekend effect indicates that local radical termination occurs
primarily via formation of nitric acid and other NOx-related compounds, some
of which (e.g. peroxy acyl nitrates) can contribute to the regional NOx
budget. While VOC emission reductions would be most effective in reducing
local O3 production, NOx emission reduction may be more important for
controlling regional oxidants. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|