Oscar Jack Kennedy-Blundell ^1* Emma L Shuttleworth ² James J Rothwell ² Gareth D Clay ²

• ¹ University of Exeter, Exeter, United Kingdom
• ² The University of Manchester, Manchester, England, United Kingdom

Vegetation fires lead to the formation of charred materials, often referred to as pyrogenic carbon (PyC), which are recalcitrant and have a high carbon density meaning they have the potential to act as a long-term carbon store. In the UK, peatlands are periodically subject to fire, both management burns and wildfires, which generate PyC. However, in the UK context, the characterisation of physical and chemical properties of PyC is limited. In this study, samples of peatland vegetation (Calluna vulgaris, Polytrichum juniperinum, Vaccinium myrtillus and Eriophorum vaginatum) were burnt in laboratory conditions across typical ranges of characteristics from UK peatland vegetation fires (250 – 800 °C and 2 – 10 minutes burn duration). Four broad severity groupings were established (low, moderate, high, very high) corresponding to 60, 70, 80 and 90 % mass loss respectively. The PyC samples were then analysed using Brunauer-Emmett-Teller (BET) surface area analysis, CHNO elemental analysis, and Fourier-transform infrared spectroscopy (FTIR) to gain a greater understanding of their physiochemical characteristics. While there was a good degree of similarity between samples within each severity group, there were significant differences between severity groups. Low to high severity samples had relatively low surface areas compared to the very high severity samples, which exhibited the greatest surface areas and a high degree of variability. O/C and H/C ratios decreased with increasing severity. FTIR showed that distinct spectra were produced between severity groups, reflecting increased sample aromaticity with burn severity. The findings of this study suggest that burn severity is a good predictor of PyC physiochemical characteristics.