Atmospher Sci & Global Chg
Research Highlights
February 2011
New Carbon Model Improves Understanding of Emission Sources
Novel simulation shows airborne carbon caused by regional impacts
Measurements of carbon-14 have confirmed that airborne organic matter surrounding Mexico City is composed of surprisingly large amounts of modern carbon. Researchers demonstrated first-ever model simulations showing modern carbon seemingly caused by regional impacts from sources such as biomass burning, forest fires, and even cooking food. Enlarge Image
Results: Recent measurements of carbon-14 confirmed that airborne organic matter surrounding Mexico City is made up of surprisingly large amounts of modern carbon. Researchers, including Jerome Fast from Pacific Northwest National Laboratory (PNNL), demonstrated first-ever model simulations showing modern carbon seemingly caused by regional impacts from sources such as biomass burning, forest fires, and even cooking food. By using the new model, researchers now are able to fingerprint the factors contributing to emissions.
Why it matters: The study demonstrates radiocarbon data, traditionally used for archeological studies, have the potential to improve how emissions and formation of organic aerosols are treated in regional atmospheric models. Most current models significantly under predict organic matter, which is a large fraction the total emissions released. With the new model, researchers can better ascertain the role of man-made and natural sources on climate change.
Methods: Together with organic components derived from aerosol mass spectrometry tools, the radioactive carbon measurements have been used to observe the performance of a regional atmospheric model when simulating the relative contributions of fossil fuels, such as car emissions, and modern carbon.
A regional model with a state-of-the-science treatment of secondary organic aerosols was used in conjunction with various measurements, including filter samples analyzed to quantify carbon-14 (a carbon isotope) and aerosol mass spectrometers.
Since carbon-14 measurements are expensive undertakings, a relatively long sampling interval of 6 or 12 hours is employed in the field. In the future, higher temporal resolution requiring less than 3 hours is needed to better quantify modern carbon sources and their diurnal cycles.
What's Next: PNNL scientists are improving algorithms associated with secondary organic aerosol formation and testing them using a wide range of field data, including the radiocarbon measurements used in this study.
Acknowledgements: This research was funded by the Department of Energy's Office of Science, Biological and Environmental Research, Atmospheric System Research program.
Research Team: The research was conducted by Alma Hodzic of the National Center of Atmospheric Research, Jerome Fast of PNNL, Jose Jimenez of the University of Colorado, Andre Prévôt of the Paul Scherrer Institute, Sönke Szidat of Oeschger Centre for Climate Change Research, University of Bern, Switzerland, and Sasha Madronich of the National Center for Atmospheric Research.
Reference: Hodzic A, JL Jimenez, ASH Prévôt, S Szidat, JD Fast, and S Madronich. 2010. "Can 3-D models explain the observed fractions of fossil and non-fossil carbon in and near Mexico City?" Atmospheric Chemistry and Physics 10(22):10997-11016. DOI: 10.5194/acp-10-10997-2010.
