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REPARTEE: Pollutant FluxesEiko Nemitz, Gavin Phillips, Chiara Di Marco, Daniela Famulari, Carole Helfter, Rick Thomas, David Fowler: Centre for Ecology and Hydrology (CEH) EdinburghClaire Martin, James Dorsey, Martin Gallagher: SEAES, University of ManchesterBen Langford, Brian Davison, Nick Hewitt: University of LancasterJanet Barlow, Curtis Wood: University of ReadingSue Grimmond:Kings College London A collaboration between NERC CityFlux and REPARTEE
Urban Flux Measurement Campaigns within CityFlux June 2003 Boulder, CO(92,000) CityFluxDecember 2005 Edinburgh(435,000) GOTE2005Feb. 2005 Gothenburg(480,000) CityFluxMay 2006 Manchester (2,200,000) MIRAGEMarch 2006 Mexico City (19,200,000) CityFluxOctober 2006 London(7,500,000)
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) Why Measure Urban Pollutant Fluxes?
Application of eddy covariance approach to the urban environment (like CO2 forest flux towers in international networks) Derives vertical flux through the horizontal plane at measurement height Flux footprint averages over several km2 Micrometeorological Flux Measurement
Eddy Covariance Need a rapid (5 -10 Hz) measurement of concentration and wind components up-draughts down-draughts
Eddy-covariance fluxes: CO2 (18 months) CO Volatile organic compounds (VOCs) – benzene, toluene, methanol, acetone, isoprene, … Particle Number (total, size-segregated) Aerosol Chemical Components (NO3-, SO42-, Org) Ozone (REPARTEE-I only) Gradients (BT Tower vs. Regents Park): Further aerosol components O3, NO, NO2, SO2 Flux Measurements During REPARTEE
Gradients above London (REPARTEE-I) How representative is the Park of the average concentration at ground level?
Fluxes of CO2 and H2O(average diurnal cycles) • 1. Lower CO2 net emissions in summer: • No heating related emissions • Net CO2 uptake by biosphere (parks, gardens) • 2. Largest night-time emissions in winter, followed by spring • Highest heating related emissions
PMF Factor Analysisof Organic Aerosol (BT Tower) LV-OOA-91? HOA LV-OOA “Cooking” OA Consistent with Regents Park measurements during REPARTEE: Allan et al., ACP, 2010.
Q-AMS Fluxes (REPARTEE-I 2006) Traffic HOA CO Nitrate Sulfate LV-OOA Concentrations Fluxes
Correlation between HOA and CO Fluxes (REPARTEE-I, Q-AMS) Look out for: Phillips et al. in ACPD REPARTEE Special Issue
Exchange velocities (Campaign Average)Ve = Flux / Concentration C4H7++ C3H3O+ C5H7++ C4H3O+ NO2+ SO+ SO2+ C4H9+ CO2+
First independent assessment of emission inventories through direct flux measurements for London Close agreement between measurements and NAEI for CO2, 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). Take-Home Messages
Full publication in Atmos. Chem. Phys. REPARTEE Special Issue (online) ClearfLo long-term flux measurements 2010-2013: CO CO2 CH4 (first time) O3 NO/NO2 (first time) Particle number Outlook