Rising NO2-Levels At Traffic Exposed Sites CAFE steering group, 23.11.2005

Urban Background Düsseldorf Lörick NO (NOx): pronounced decrease NO2:stagnant or slight decrease NOx NO2 *01.01. – 31.10.2005

Results from model calculations (Klemp 2005; box model; MCM-3; O3 background 65 µg/m³, t = 300 ms) Stagnant (or slightly decreasing) NO2 levels in contrast to distinct decrease of NO can be explained by O3 chemistry. Distinct NO2 decrease not before NO levels have reached O3 background (65 µg/m³)

Street canyon Düsseldorf Corneliusstrasse NO (NOx): decrease (about -9% NOx since year 2000) NO2:increase (about 23 % NO2since year 2000) NO2 increase can not explained by ozone chemistry alone NOx NO2 *01.01. – 31.10.2005

NO and NO2 trends adjacent to a motorway (IFEU, BAST, 2005) NO: decrease (about -60% NOx since year 1987) NO2: stagnant until year 2000 NO2: distinct increase since year 2000

Conclusions (1) Rising NO2 levels at traffic exposed sites (since ~ 2000) cannot be explained by O3 chemistry alone Probable cause: rising NO2/NO ratio in vehicle emissions from ~ 5 % (1990) to ~ 10-12 % (fleet averages) due to - increasing share of diesel cars with ox. catalysts - CRT filter technology

Conclusions (2) Rising NO2 trend will it make extremely difficult to meet NO2 LV (2010) Model predictions of falling NO2 levels too optimistic Vehicle emission standards (EURO V, EURO VI) - should take into account rising NO2/NO ratio (NO2 limitation? Monitoring of NO2 emissions?) - should reduce NOX emissions distinctively