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HERO ID
87725
Reference Type
Journal Article
Title
Evidence of an increasing NO2/NOx emissions ratio from road traffic emissions
Author(s)
Carslaw, DC
Year
2005
Is Peer Reviewed?
1
Journal
Atmospheric Environment
ISSN:
1352-2310
EISSN:
1873-2844
Volume
39
Issue
26
Page Numbers
4793-4802
DOI
10.1016/j.atmosenv.2005.06.023
Web of Science Id
WOS:000231848900017
Abstract
A statistical analysis of roadside concentrations of nitrogen oxides (NOX) and nitrogen dioxide (NO2) in London shows that from 1997 to 2003 there has been a statistically significant downward trend (at the p=0.004 level) in NOX averaged across a network of 36 sites. Conversely, there has been no statistically significant trend in the concentrations of NO2 over the same period. Hourly modelling using a simple constrained chemical model shows that the NO2/NOX emissions ratio from road traffic has increased markedly from a mean of about 5û6 vol% in 1997 to about 17 vol% in 2003. Calculations show that if the NO2/NOX emissions ratio had remained the same as that towards the beginning of each time series, 14 out of the 36 sites would have shown a statistically significant downward trend in NO2 at the p=0.10 level compared with only five that did. The increase in the NO2/NOX emissions ratio from road traffic in recent years has therefore had a significant effect on recent trends in roadside NO2 concentrations. It is shown that the increased use of certain types of diesel particulate filters fitted to buses is likely to have made an important contribution to the increasing trends in the NO2/NOX emissions ratio. However, it is unlikely that these filters account for all of the observed increase and other effects could be important, such as the increased penetration of diesel cars in the passenger car fleet and new light- and heavy-duty engine technologies and management approaches.
Keywords
primary NO2; nitrogen dioxide; diesel particulate filter; trend analysis; Mann-Kendall; London; urban air quality
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LitSearch-NOx (2024)
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