Radiocarbon Measurements Reveal Underestimated Fossil CH <sub>4</sub> and CO <sub>2</sub> Emissions in London
Giulia Zazzeri, Heather Graven, Xiaomei Xu, Eric Saboya, Liam Blyth, Alistair J. Manning, Hannah Chawner, Dien Wu, Samuel Hammer
Abstract
Abstract Radiocarbon ( 14 C) is a powerful tracer of fossil emissions because fossil fuels are entirely depleted in 14 C, but observations of 14 CO 2 and especially 14 CH 4 in urban regions are sparse. We present the first observations of 14 C in both methane (CH 4 ) and carbon dioxide (CO 2 ) in an urban area (London) using a recently developed sampling system. We find that the fossil fraction of CH 4 and the atmospheric concentration of fossil CO 2 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 CO 2 and CH 4 in cities can be evaluated and improved with 14 C observations when the nuclear power plants influence is negligible.