70 / 2025-03-31 09:00:34

Sequestration of sedimentary organic carbon in arctic fjords mediated by organo-mineral interactions

organic carbon preservation,organo-mineral interactions,fjords,ramped pyrolysis/oxidation,climate change

Theme 5: Life-Mineral Interaction and Evolutions > Session 5d: Microbe-mineral Interaction and Its Environmental Impact

Microbial-mediated organo-mineral interactions serve as an effective pathway of long-term organic carbon (OC) sequestration and can considerably offset greenhouse gas emissions through the stabilization of OC. However, the complex nature and different protection mechanisms largely inhibit our understanding of carbon-climate feedback. In the Arctic, soil and sedimentary OC composes a broad range of age spectrum, indicative of diverse turnover likely associated with various mineral binding forces. Under warming circumstances, terrigenous OC (e.g., soil OC) is eroded, transported to and reburied in adjacent estuaries (e.g., fjords) and shelf margins, representing a transition of OC preservation to the long term. Through these processes, the shifts of OC properties and its association with minerals are informative to disentangle the accurate processes modulated by organo-mineral interactions. Here, we characterized the OC properties of surface sediments in five Svalbard fjords with ramped pyrolysis/oxidation (RPO) technique and coupled isotopic (δ¹³C, △¹⁴C) measurement of RPO fractions. Our result indicates highly spatial heterogeneity in OC properties, which can be related to distinct provenances and various degrees of OC stabilization through organo-mineral interactions. Overall, this study implies that different processes (e.g., microbial degradation, organo-mineral interactions, metamorphism) may operate synergistically to regulate OC degradation and therefore long-term climate fluctuations.