Soil organic matter (SOM) represents one of the largest pools of carbon on the Earth’s surface, and thus it has the potential to contribute large amounts of carbon to the atmosphere. The residence time and decomposition rate of carbon in soil are regulated by the stability of SOM. SOM can be stabilized by various mineral phases, and iron (Fe) oxides have a large capacity to sorb and stabilize SOM. However, under anaerobic conditions ferric iron can be abiotically or biotically reduced, potentially destabilizing iron-sorbed SOM. Unfortunately, the controls on these processes are not thoroughly understood. To begin to elucidate the details of these processes, we investigated how certain biogeochemical variables (e.g. electron donors, community structure) control the stability of iron-bound SOM in temperate forest soils with varied Fe:OC ratios. Our results indicate that the addition of an electron donor, in the form of organic carbon molecules (e.g. glucose), to the native soil community stimulates the reduction of Fe in both the aqueous and sorbed phases, and promotes the release of Fe(II,III) into the aqueous phase. The addition of <i>Shewanella oneidensis</i> MR-1, a dissimilatory iron-reducing bacterium, further enhanced these effects. Further, the amount of Fe released to the solution phase continued to increase throughout the 13-day incubation, while the sorbed Fe reached a maximum after 7 days, potentially due to changes in mineralogy during the incubations. In the solution phase, the reductive dissolution of Fe correlated with an increase of dissolved organic carbon, indicating that soil OC and Fe mobility are coupled.

Biogeochemical controls on the stability of iron-bound soil organic carbon

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.