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\begin{document}

\title{Radiocarbon Measurements Reveal Underestimated Fossil CH4 and CO2
Emissions in London}



\author[1]{Giulia Zazzeri}%
\author[2]{Heather Graven}%
\author[3]{Xiaomei Xu}%
\author[4]{Eric Saboya}%
\author[2]{Liam Peter Blyth}%
\author[5]{Alistair J. Manning}%
\author[4]{Hannah Chawner}%
\author[6]{Dien Wu}%
\author[7]{Samuel Alexander Hammer}%
\affil[1]{Department of Physics, ETH Zürich, Zürich,}%
\affil[2]{Imperial College London}%
\affil[3]{University of California, Irvine}%
\affil[4]{University of Bristol}%
\affil[5]{UKMet Office}%
\affil[6]{Cal Tech}%
\affil[7]{Institut für Umweltphysik}%


\vspace{-1em}



  
  \date{May 29, 2024}


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\begin{abstract}
Radiocarbon (14C) is a powerful tracer of fossil emissions because
fossil fuels are entirely depleted in 14C, but observations of 14CO2 and
especially 14CH4 in urban regions are sparse. We present the first
observations of 14C in both methane (CH4) and carbon dioxide (CO2) in an
urban area (London) using a recently developed sampling system. We find
that the fossil fraction of CH4 and the atmospheric concentration of
fossil CO2 are consistently higher than simulated values using the
atmospheric dispersion model NAME coupled with emission inventories.
Observed net biospheric uptake in June-July is not well correlated with
simulations using the SMURF model with NAME. The results show the
partitioning of fossil and biospheric CO2 and CH4 in cities can be
evaluated and improved with 14C observations when the nuclear power
plants influence is negligible.%
\end{abstract}%



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