Monitoring ffCO2 emission hotspots using atmospheric 14CO2 measurements
Authors: Hammer Samuel , Rieß Christoph , Maier Fabian , Kneuer Tobias , Della Coletta Julian , Preunkert Susanne , Karstens Ute , Levin Ingeborg 
Published: March 2020

&lt;p&gt;Reliable estimates of fossil fuel CO&lt;sub&gt;2&lt;/sub&gt; (ffCO&lt;sub&gt;2&lt;/sub&gt;) 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 ffCO&lt;sub&gt;2&lt;/sub&gt; 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]. &lt;sup&gt;14&lt;/sup&gt;CO&lt;sub&gt;2&lt;/sub&gt; has become the gold standard when it comes to the experimental splitting of atmospheric CO&lt;sub&gt;2&lt;/sub&gt; concentration into its biogenic and fossil components [e.g. Levin et al. 2003; 2011 or Turnbull et al. 2009].&lt;/p&gt;&lt;p&gt;Here we report on the identification of ffCO&lt;sub&gt;2&lt;/sub&gt; emitted from the Mannheim/Ludwigshafen metropolitan region in the upper Rhine valley, Germany. Quantification of the regional ffCO&lt;sub&gt;2&lt;/sub&gt; 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 CO&lt;sub&gt;2&lt;/sub&gt; and &lt;sup&gt;14&lt;/sup&gt;CO&lt;sub&gt;2&lt;/sub&gt; observations have been performed as part of the European RINGO project. Furthermore, we investigate the suitability of using the total-CO&lt;sub&gt;2&lt;/sub&gt; difference between the two stations as a proxy for fossil fuel CO&lt;sub&gt;2&lt;/sub&gt; and the seasonal applicability of such a surrogate tracer. Finally, the observations of the total-CO&lt;sub&gt;2&lt;/sub&gt; surrogate tracer will be compared with the predictions from STILT forward model runs.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Ref.:&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;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&amp;#8322; Emissions Monitoring &amp; Verification Support Capacity &amp;#8211; Needs and high level requirements for in situ measurements, doi: 10.2760/182790, European Commission Joint Research Centre, EUR 29817 EN&lt;/p&gt;&lt;p&gt;Turnbull, J., Rayner, P., Miller, J., Naegler, T., Ciais, P., &amp; 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).&lt;/p&gt;