Carbon sources and sequestration: 14C Ramped Pyroxidation in aquatic sediments.

Sequestration of organic carbon in aquatic sediments can depend on its source and potential lability. Studies have shown that bulk lake and marine sediment comprises carbon of different origin but its source has been difficult to attribute. A new Ramped Pyroxidation/Combustion (RPO) system in the ¹⁴CHRONO Centre has been established. RPO is a technique that incrementally heats a sample, and allows for collection of the CO₂ produced for radiocarbon analyses. The results show its utility in partitioning carbon sources in lake sediment (Rostherne Mere, UK, Santa María del Orolake, Mexico), and arctic marine sediment (Chukchi Sea and Beaufort Shelf). RPO and 2-stepped combustion¹. ¹⁴C indicated multiple carbon sources in Rostherne Mere sediment, some of which could be attributed to the construction of a sewage treatment works (STW) on the lake shore, and subsequently inputs from this STW. RPO identified 3 carbon fractions in Mexican Lake sediment, which provided a more accurate chronology, partitioning the contemporaneous sediment date from offsets induced from volcanic activity in the area. Results from Arctic marine sediment demonstrated inputs of carbon from ancient permafrost, providing a means to refine the chronologies and a basis for future research linked with carbon loss from thawing permafrost.

¹Keaveney et al. 2020. Journal of Palaeolimnology 64 347-363