Click to edit Master subtitle style 2/6/12 Quantification of anthropogenic emissions from an urban region: First results of time-integrated flask samples from the Indianapolis Flux Project (INFLUX) Jocelyn Turnbull, Colm Sweeney, Doug Guenther, Anna Karion, Tim Newberger, Pieter Tans, NOAA/ESRL and CIRES, University of Colorado Natasha Miles, Scott Richardson, Thomas Lauvaux, Kenneth Davis, Pennsylvania State University Paul Shepson, Obie Cambaliza, Purdue University Kevin Gurney, Arizona State University Scott Lehman, INSTAAR, University of Colorado NOAA/ESRL Carbon Cycle Group, INSTAAR Isotope and 14C Lab Staff

2/6/12 Why use time-integrated flask samples? In urban regions, can have substantial variability in mixing ratios – integrated samples reduce some of this noise Match atmospheric sampling with the ~1 hour time step of regional models and meteorological data Keep integrating time short enough that meteorology is consistent INFLUX tower 1, :00-21:00 UTC

Click to edit Master subtitle style 2/6/12 integrating volume (15L) filter valve wate r trap Dryer/integrater packageIntegrating compressor packagePortable flask package filter fast flush valve vent valve 0-1L flow controller pump pressure relief valve pressure sensor pump Sample collected over 1 hour Mix 1 hour of air by flowing through a large mixing volume Vary flow rate during filling to obtain close to linear mixture Collect air into 2 PFP flasks for measurement Integrated flask sampling

2/6/12 Integrated flask sampling validation in situ – flask difference 0.01±0.09 ppm Hourly averaged continuous – integrated flask CO2 For comparison: LEF 396 m in situ vs grab flask samples ( ) in situ – flask difference 0.03±0.38 ppm

2/6/12 INFLUX: Tower flask results Flask samples collected only when Tower 2 is downwind Tower 1 is always upwind, background station (Criteria met 25% of days) Towers are m tall cell phone towers Prevailing wind

2/6/12 CO2 enhancements across Indianapolis Tower 2 (downwind) - Tower 1 (upwind)

2/6/12 Enhancements across Indianapolis Strong enhancements in most anthropogenic species

2/6/12 Methane not always enhanced!

2/6/12  14CO2 and fossil fuel CO2  14CO2 is lower at Tower 2 – 14C-free CO2ff decreases  14CO2  14CO2 CO2ff CO2ff = CO2obs (Δobs -Δbg) Δff -Δbg CO2r (Δr -Δbg) Δff -Δbg CO2ff enhanced at Tower 2

2/6/12 Contributions to CO2 enhancement Flask samples from Dec 2010 – May 2011 Slope = 1.1 ± 0.2 ppm/ppm 1:1 line (if  CO2 all due to CO2ff)

2/6/12 Source apportionment from CO2 isotopes:  14CO2  14Csource = slope = -900 ± 150‰  obsCobs=  bgCbg +  sCs Cobs=Cbg + Cs  obsCobs -  bgCbg=  s(Cobs - Cbg)

2/6/12  14C  CO2 fraction Background atmosphere40 ‰ Urban source-900 ± 150 ‰ Fossil fuels-1000 ‰ (zero 14C content) 0.9 ± 0.15 Other sources (biofuel/respiration/photos ynthesis) 40 ‰ 0.1 ± 0.15  sCs=  ffCff +  otherCother Cff/Cs=(  s –  other)/(  ff –  other) Source apportionment from CO2 isotopes:  14CO2 Indiana mandates 10% bio-ethanol in gasoline In winter, Indianapolis urban CO2 emissions are 90% CO2ff, 10% biofuel No significant respiration/photosynthesis contribution, even in summer!

2/6/12 Source apportionment from CO2 isotopes:  13CO2  13Csource = slope = ± 1.1‰

2/6/12  13C  14C  CO2 fraction Background atmosphere-8.0 ‰40 ‰ Winter urban source-29.1 ± 1.1 ‰-900 ± 150 ‰ Fossil fuels-1000 ‰ 0.9 ± 0.15 Natural gas-40 ‰ 0.33 Petroleum-28 ‰ 0.30 Coal-24 ‰ 0.27 Other sources40 ‰ 0.1 ± 0.15 Bioethanol (from corn)-10.4 ‰ 0.1 Respiration/photosynthesis-26.0 ‰ 0.0  sCs=  ngCng +  petCpet +  coalCcoal +  bfCbf +  bioCbio Source apportionment from CO2 isotopes:  14CO2 and  13CO2 Split CO2ff into different fuel types using  13CO2 Compare with inventory estimates of fuel types

2/6/12 Correlation with CO and benzene Emission ratios for CO and benzene are ~20% lower than observed in other US cities Large power plant contributes 30% of Indy CO2ff = lower emission ratios? CO:CO2ff 12±3 ppb/ppm Benzene:CO2ff 14±3 ppt/ppm

2/6/12 Summary  INFLUX towers use a new time-integrated flask sampling system to collect samples averaged over a 1 hour period  Tower sampling is designed to capture both upwind (background) and downwind signals  Strong enhancements in anthropogenic species across the urban region  In winter and in spring in Indianapolis, the CO2 enhancement appears to be entirely due to CO2ff and bio- ethanol (there is no apparent photosynthesis/respiration signal)  Reasonable correlations of CO2ff with combustion tracers such as CO and benzene, with emission ratios slightly lower than Western US cities, likely due to influence of power plant