Challenges faced when using radiocarbon measurements to estimate fossil fuel emissions in the UK.

Tuesday, 15 December 2015
Poster Hall (Moscone South)
Angelina Wenger1, Simon O'Doherty2, Matthew L Rigby2, Anita Ganesan2, Alistair Manning3 and Grant Allen4, (1)University of Bristol, School of Chemistry, Bristol, United Kingdom, (2)University of Bristol, Bristol, United Kingdom, (3)UK Meteorological Office, Exeter, United Kingdom, (4)University of Manchester, Manchester, United Kingdom
Estimating the anthropogenic component of carbon dioxide emissions from direct atmospheric measurements is difficult, due to the large natural carbon dioxide fluxes. One way of determining the fossil fuel component of atmospheric carbon dioxide is the use of radiocarbon measurements. Whilst carbon reservoirs with a reasonably fast carbon exchange rate all have a similar radiocarbon content, fossil fuels are completely devoid of radiocarbon due to their age. Previous studies have 14CO2 (UK) this approach is compromised by the high density of 14CO2 emitting nuclear power plants. Of the 16 nuclear reactors in the UK, 14 are advanced gas cooled reactors, which have one of the highest 14CO2 emission rates of all reactor types. These radiocarbon emissions not only lead to a serious underestimation of the recently added fossil fuel CO2, by masking the depletion of 14C in CO2, but can in fact overshadow the depletion by a factor of 2 or more. While a correction for this enhancement can be applied, the emissions from the nuclear power plants are highly variable, and an accurate correction is therefore not straightforward. We present the first attempt to quantify UK fossil fuel CO2 emissions through the use of 14CO2. We employ a sampling strategy that makes use of a Lagrangian particle dispersion model, in combination with nuclear industry emission estimates, to forecast “good” sampling times, in an attempt to minimize the correction due to emissions from the nuclear industry. As part of the Greenhouse gAs Uk and Global Emissions (GAUGE) project, 14CO2measurements are performed at two measurement sites in the UK and Ireland, as well as during science flights around the UK. The measurement locations have been chosen with a focus on high emitting regions such as London and the Midlands.

We discuss the unique challenges that face the determination of fossil fuel emissions through radiocarbon measurements in the UK and our sampling strategy to deal with them. In addition we present the first results of our ground based measurements, and their implications for how radiocarbon measurements might be used, even in seemingly impractical locations.