"Aging and preservation of natural organic carbon"
Speaker: Jordon Hemingway
Abstract: Organic carbon (OC) preservation in soils and sediments removes carbon dioxide from the atmosphere and promotes atmospheric oxygen accumulation. This process likely involves both chemical recalcitrance and physical protection, but the relative importance of these mechanisms remains unknown. To directly assess the controls on preservation, we measured radiocarbon age as a function of activation energy (E) using serial oxidation for a global soil, sediment, and dissolved OC sample set. Resulting E distributions in mineral-free OC differ drastically from all mineral-containing environments. Furthermore, we observe ingrowth and persistence of high-E OC in soils and sediments. A comparison with theoretical predictions reveals that selective preservation of chemically recalcitrant compounds cannot explain observed E and radiocarbon age trends. Rather, physical protection controls OC preservation wherever minerals are present.
Lunch will be provided. As always, please plan to bring reusable plates and cutlery to reduce waste.