Analysis of radiocarbon in atmospheric methane: technological advances and interpretation of measurements

Radiocarbon (¹⁴C) is an optimal tracer of methane emissions, as ¹⁴C measurements enable distinguishing fossil from biogenic methane. However, we are not yet applying these measurements in monitoring programs for quantification of sources contribution, because of the technical challenges associated with the ¹⁴C analysis and the bias introduced by ¹⁴C emissions from nuclear power plants.

Studies in London and in Switzerland demonstrate how the nuclear influence should be accurately modelled for a quantitative interpretation of ¹⁴C measurements and that a robust uncertainty estimate of the fossil and biogenic proportion of CH₄ emissions is highly needed.

Here we present the technological advances in the ¹⁴CH₄ analysis, including the achievement of high precision ¹⁴CH₄ measurements (5 ‰) using a new portable sampler developed at the laboratory of Ion Beam Physics, and the potential of expanding these measurements for an improved understanding of sources. We will present the first quantification of fossil methane emissions in London using ¹⁴C, demonstrating that, by increasing the measurement capability, we can use ¹⁴C to constrain the methane budget at regional scale.