Some thoughts on long-term trends in NO 2 , NO X and NO 2 :NO X ratios

1. Some thoughts on long-term trends in NO2, NOX and NO2:NOX ratios David Muir IAQM 1 July 2010

2. Outline. Long term trends - 199? to December 2009 Urban Background sites - London Bloomsbury, - Leeds Centre. Roadside sites - Camden Kerbside, - Bury Roadside, - Haringey Roadside, - Marylebone Road, - Bath Roadside, - Glasgow Kerbside.

3. London Bloomsbury NO2:NOX Ratio 1 0.8 0.6 0.4 0.2 0 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Missing data

4. London Bloomsbury NO2:NOX 400 300 200 100 0 -100 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Missing data

5. London Bloomsbury NO2 10 0 -10 -20 -30 -40 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Missing data

6. London Bloomsbury NOX 50 0 Missing data -50 -100 -150 -200 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

7. London Bloomsbury NO 10 0 -10 -20 -30 -40 -50 -60 -70 -80 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Missing data

8. Leeds Centre NO2:NOX 500 400 300 200 100 0 -100 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

9. Leeds Centre NO2 10 0 -10 -20 -30 -40 -50 -60 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

10. Missing data Camden Kerbside NO2:NOX 600 500 400 300 200 100 0 -100 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

11. Camden Kerbside NO2 15 10 5 Missing data 0 -5 -10 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

12. Missing data Camden Kerbside NOX 100 0 -100 -200 -300 -400 -500 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

13. Bury Roadside NO2:NOX 700 600 500 400 300 200 100 0 -100 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

14. Bury Roadside NO2 5 0 -5 -10 -15 -20 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

15. Haringey Roadside NO2 10 0 -10 -20 -30 -40 -50 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

16. London Marylebone Road NO2 30 20 10 0 -10 -20 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

17. Bath Roadside NO2 5 0 -5 -10 -15 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

18. Glasgow Kerbside NO2 8 7 6 5 4 3 2 1 0 -1 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

19. Conclusions/Questions. 1. The NO2:NOX ratio increased at a number of (maybe all) urban sites between 1998 & 1999. 2. At Urban Background sites [NO2] has remained steady following earlier decreases. 3. At some Roadside sites [NO2] has also remained steady following earlier decreases, but…. 4. At other Roadside sites [NO2] has increased since about 2003. WHY???

20. Conclusions/Questions. 5. One possibility is that the sites where no significant increase has found are further away from the road or are upwind of road. 6. Another, and more realistic possibility, is that the sites where there have been increases in [NO2] are located on roads with congested, slow-moving traffic. 7. Finally, and perhaps most important, do Euro standards and emissions factors even BEGIN to address this issue?