Abstract
Abstract. A quantum cascade laser based absorption spectrometer (QCLAS) is applied for the first time to perform in situ, continuous and high precision isotope ratio measurements of CO2 in the free troposphere. Time series of the three main CO2 isotopologue mixing ratios (12C16CO2, 13C16CO2 and 12C18O16O) have simultaneously been measured at one second time resolution over two years (from August 2008 to present) at the High Altitude Research Station Jungfraujoch (3580 m a.s.l., Switzerland). This work focuses on periods in February 2009 only, when sudden and pronounced enhancements in the tropospheric CO2 were observed. These short-term changes were closely correlated with variations in CO mixing ratios measured at the same site, indicating combustion related emissions as potential source. The analytical precision of 0.046‰ (at 50 s integration time) for both δ13C and δ18O and the high temporal resolution allowed the application of the Keeling plot method for source signature identification. The spatial origin of these CO2 emission sources was then determined by backward Lagrangian particle dispersion simulations.
Highlights
The accentuated mixing ratio increase of carbon dioxide (CO2) and other trace gases in the Earth’s atmosphere related to human activities is of major concern for climate change, because these anthropogenic emissions are gaining a significant role as an additional external forcing factor (Andres et al, 1999)
This paper is the first demonstration of long-term, in situ and high precision isotope measurements of CO2 under free tropospheric conditions at a high altitude site by laser absorption spectroscopy
The instrument has been operating unattended in the field and providing continuous, high temporal resolution measurements of 12CO2, 13CO2 and 16O12C18O
Summary
The accentuated mixing ratio increase of carbon dioxide (CO2) and other trace gases in the Earth’s atmosphere related to human activities is of major concern for climate change, because these anthropogenic emissions are gaining a significant role as an additional external forcing factor We demonstrate the feasibility of improving anthropogenic CO2 source identification and characterization at large regional scales by using laser spectroscopy as on-line and in situ measurement technique For this purpose, an instrument was designed and developed to perform high precision isotope ratio measurement of both δ13C and δ18O of atmospheric CO2 at ambient mixing ratio. An instrument was designed and developed to perform high precision isotope ratio measurement of both δ13C and δ18O of atmospheric CO2 at ambient mixing ratio This spectrometer has been continuously measuring atmospheric CO2 and its isotopic composition in real-time at the high Alpine observatory on Jungfraujoch that allows intermittent sampling of free tropospheric background air and polluted boundary layer influenced air. This CO2 time-series together with the isotopic composition at high temporal resolution provide essential information for identification and characterization of pollution events, as presented
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