Monitoring ffCO2 emission hotspots using atmospheric 14CO2 measurements

<p>Reliable estimates of fossil fuel CO₂ (ffCO₂) emissions from high-emission regions or urban areas are currently in demand from a wide range of players. On the one hand, cities and municipalities themselves are interested in an independent validation of their ffCO₂ emissions. On the other hand, there is an increased interest in atmospheric science to merge independent emission estimate methods over different scales [Pinty et al. 2019]. ¹⁴CO₂ has become the gold standard when it comes to the experimental splitting of atmospheric CO₂ concentration into its biogenic and fossil components [e.g. Levin et al. 2003; 2011 or Turnbull et al. 2009].</p><p>Here we report on the identification of ffCO₂ emitted from the Mannheim/Ludwigshafen metropolitan region in the upper Rhine valley, Germany. Quantification of the regional ffCO₂ component requires knowledge of the composition of the background air. Thus, the emission area has been sampled by an upwind and a downwind station. We will discuss the advantages and disadvantages of using local background measurements conducted at a dedicated upwind station of the emission area and compare this realisation of background estimate to regional background estimates derived from measurements at classical remote background sites. All CO₂ and ¹⁴CO₂ observations have been performed as part of the European RINGO project. Furthermore, we investigate the suitability of using the total-CO₂ difference between the two stations as a proxy for fossil fuel CO₂ and the seasonal applicability of such a surrogate tracer. Finally, the observations of the total-CO₂ surrogate tracer will be compared with the predictions from STILT forward model runs.</p><p>&#160;</p><p>Ref.:</p><p>Levin, I., B. Kromer, M. Schmidt and H. Sartorius, 2003. A novel approach for independent budgeting of fossil fuels CO2 over Europe by 14CO2 observations. Geophys. Res. Lett. 30(23), 2194, doi. 10.1029/2003GL018477.</p><p>Levin, I., S. Hammer, E. Eichelmann, F. Vogel, 2011. Verification of greenhouse gas emission reductions: The prospect of atmospheric monitoring in polluted areas. Philosophical Transactions A 369, 1906-1924, doi:10.1098/rsta.2010.0249.</p><p>Pinty B., P. Ciais, D. Dee, H. Dolman, M. Dowell, R. Engelen, K. Holmlund, G. Janssens-Maenhout, Y. Meijer, P. Palmer, M. Scholze, H. Denier van der Gon, M. Heimann, O. Juvyns, A. Kentarchos and H. Zunker (2019) An Operational Anthropogenic CO&#8322; Emissions Monitoring & Verification Support Capacity &#8211; Needs and high level requirements for in situ measurements, doi: 10.2760/182790, European Commission Joint Research Centre, EUR 29817 EN</p><p>Turnbull, J., Rayner, P., Miller, J., Naegler, T., Ciais, P., & Cozic, A. (2009). On the use of 14CO2 as a tracer for fossil fuel CO2: Quantifying uncertainties using an atmospheric transport model. Journal of Geophysical Research: Atmospheres, 114(D22).</p>