Observations of 14CO2 at the Boulder Atmospheric Observatory (BAO)
B. LaFranchi1, G. Petron2, J. Miller2, S. Lehman3, A. Andrews4, E. Dlugonkencky4, B. Miller2, S. Montzka4, J. Turnbull2, P. Tans4 and T. Guilderson1
1Lawrence Livermore National Laboratory, Livermore, CA 94550; 925-423-4555, E-mail: email@example.com
2Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309
3Institute of Arctic and Alpine Research (INSTAAR), University of Colorado, Boulder, CO 80309
4NOAA Earth System Research Laboratory, Boulder, CO 80305
Atmospheric radiocarbon (14C) represents an important observational constraint on emissions of fossil-fuel derived carbon into the atmosphere due to the near absence of 14C in fossil fuel reservoirs. The high sensitivity and precision that accelerator mass spectrometry (AMS) affords in atmospheric 14C analysis has greatly increased the potential for using such measurements to facilitate carbon cycle studies and the validation of greenhouse gas emissions inventories. Here we report on the first-ever 14CO2 observations from the BAO, located in Erie, CO. The BAO tower is one of the tall towers in the NOAA ESRL greenhouse gas flask sampling network that has recently begun sampling for atmospheric 14C, as well as other trace gases.
We will present observations of Delta 14C in whole air samples collected between June 2009 and September 2010 at BAO. Values ranged from -20‰ (± 1.8 ‰) to +46 ‰ (± 1.8 ‰) corresponding to estimated fossil fuel CO2 (CO2ff) concentrations as high as 25 ppm (± 1 ppm) above the background. An analysis of the relationship between CO2ff and other combustion tracers provides information on the type of combustion contributing to the total fossil fuel signal and on co-located activities, such as oil and gas drilling operations to the northeast. We will focus, in particular, on the correlations of CO2ff with CO and CH4. The observed CO to CO2ff ratio is lower than has been seen in other regions, suggesting a relatively small contribution from mobile sources to total emissions in the region and a greater source from electrical utilities. Differences in the CH4 to CO2ff ratio with wind direction indicates a larger source of CH4 when winds arrive from the northeast, where significant oil and gas drilling operations are located, as opposed to the Denver metro area to the south and southeast.