C02_P01

Carbon Isotope Changes Through the Recent Past: F¹⁴C and δ¹³C values in single barley grain from 1852 to 2020

Dunbar E¹,  Scott M², Tripney B¹, Addis H³

¹SUERC, University of Glasgow, Glasgow, UK, ²University of Glasgow, Glasgow, UK, ³Rothamsted Research, Hertfordshire, UK

Annual records are gaining increasing prominence, whether in the form of tree rings (with their growing importance in IntCal) and other reservoirs, or from the more recent past, such as grain with a single known year of growth.  Such annual F¹⁴C and δ¹³C data from the past 60 years has proven a useful tool in the study of both environmental processes and in forensic science, generating “bomb F¹⁴C curves”.

Presented here are F¹⁴C and ancillary δ¹³C values on barley grain (Hordeum vulgare L. spring barley) covering the period 1852 to 2021, collected from the sample archive of the Long-Term Experiments (LTEs) Hoosfield Spring Barley at Rothamsted Research (Hertfordshire, UK) – the oldest agricultural research station in the world, founded in 1843.

The barley grain data is presented alongside data from barley mash samples which have formed a part of several intercomparison studies undertaken in the past 30 years.  Together, these data add value to the post bomb F¹⁴C curves. Furthermore, it is now evident that recent F¹⁴C values for grain are approaching the nominal activity of an 1890 wood (F¹⁴C value of 1), raising the questions: When will the F¹⁴C value decrease below 1? Will this cause difficulties in establishing whether a sample derives from the pre- or post-nuclear era?