1. REPARTEE: Pollutant Fluxes Eiko Nemitz, Gavin Phillips, Chiara Di Marco, Daniela Famulari, Carole Helfter, Rick Thomas, David Fowler: Centre for Ecology and Hydrology (CEH) Edinburgh Claire Martin, James Dorsey, Martin Gallagher: SEAES, University of Manchester Ben Langford, Brian Davison, Nick Hewitt: University of Lancaster Janet Barlow, Curtis Wood: University of Reading Sue Grimmond: Kings College London A collaboration between NERC CityFlux and REPARTEE

2. Urban Flux Measurement Campaigns within CityFlux MIRAGE March 2006 Mexico City (19,200,000) June 2003 Boulder, CO (92,000) GOTE2005 Feb. 2005 Gothenburg (480,000) CityFlux December 2005 Edinburgh (435,000) CityFlux October 2006 London (7,500,000) CityFlux May 2006 Manchester (2,200,000)

3. Why Measure Urban Pollutant Fluxes? Direct measurement of emissions (unlike emissions derived from concentrations) Independent top-down verification of emission inventories (non reactive compounds) Source attribution (spatial & temporal) Identification of unknown sources Information on chemical processing (reactive compounds)

4. Micrometeorological Flux Measurement Application of eddy covariance approach to the urban environment (like CO 2 forest flux towers in international networks) Derives vertical flux through the horizontal plane at measurement height Flux footprint averages over several km 2

5. up-draughts down-draughts Need a rapid (5 -10 Hz) measurement of concentration and wind components Eddy Covariance

6. Flux Measurements During REPARTEE Eddy-covariance fluxes: CO 2 (18 months) CO Volatile organic compounds (VOCs) – benzene, toluene, methanol, acetone, isoprene, … Particle Number (total, size-segregated) Aerosol Chemical Components (NO 3 -, SO 4 2-, Org) Ozone (REPARTEE-I only) Gradients (BT Tower vs. Regents Park): Further aerosol components O 3, NO, NO 2, SO 2

7. Gradients above London (REPARTEE-I) How representative is the Park of the average concentration at ground level?

8. Fluxes of CO 2 and H 2 O (average diurnal cycles) 1. Lower CO 2 net emissions in summer: - No heating related emissions - Net CO 2 uptake by biosphere (parks, gardens) 2. Largest night-time emissions in winter, followed by spring - Highest heating related emissions

9. Weekday vs. Weekend

10. Source Attribution of Net CO 2 Flux

12. Comparison of VOC Fluxes with NAEI

13. Diurnal Cycles during REPARTEE-II

14. Particle Number Fluxes by CPC (10 – 2000 nm)

15. Variability in Particle Number Flux

16. PMF Factor Analysis of Organic Aerosol (BT Tower) “Cooking” OA HOA LV-OOA LV-OOA-91? Consistent with Regents Park measurements during REPARTEE: Allan et al., ACP, 2010.

17. Q-AMS Fluxes (REPARTEE-I 2006) ConcentrationsFluxes Traffic HOA CO Nitrate Sulfate LV-OOA

18. Correlation between HOA and CO Fluxes (REPARTEE-I, Q-AMS) Look out for: Phillips et al. in ACPD REPARTEE Special Issue

19. Comparison with Other Cities Diurnal Cycles NO 3 - & HOA

20. m/z Comparison of Concentration vs. Flux Spectrum

21. NO 2 + SO + SO 2 + CO 2 + C4H9+C4H9+ C 4 H 7 + + C 3 H 3 O + C 5 H 7 + + C 4 H 3 O + Exchange velocities (Campaign Average) V e = Flux / Concentration

22. Take-Home Messages First independent assessment of emission inventories through direct flux measurements for London Close agreement between measurements and NAEI for CO 2, CO and some VOCs (benzene / toluene) Poor agreement for other oxygenated VOCs Aerosol composition and diurnal pattern in organic aerosol fluxes consistent with significant contribution from cooking (deep frying?) Urban area acts as a significant source for aerosol nitrate during certain conditions (cool, calm, high humdity) Flux measurements provide a further angle to probe chemical signature of local (primary) organic aerosol (ongoing).

23. Outlook Full publication in Atmos. Chem. Phys. REPARTEE Special Issue (online) ClearfLo long-term flux measurements 2010- 2013: –CO –CO 2 –CH 4 (first time) –O 3 –NO/NO 2 (first time) –Particle number