Abstract
Manganese (Mn)-oxides regulate carbon (C) cycling in soils by sorbing and oxidizing organic compounds. The composition of soil organic matter varies widely, and little is known about the reactivity of individual organic compounds with structurally diverse Mn-oxides under various environmentally relevant pH conditions. Here, we examined the affinity of six organic compounds for three Mn-oxides, comprised of layer (birnessite and hydrous Mn oxide HMO) or tunnel (cryptomelane) structures, at acidic (pH 4), slightly acidic (pH 6), and slightly alkaline (pH 8) conditions. Cryptomelane, with a higher specific surface area and point of zero charge, showed higher reactivity than that of HMO and birnessite. Interestingly, these Mn-oxides, although different in structures, decomposed each organic compound to form the same products. Citrate, pyruvate, ascorbate, and catechol induced reduction and dissolution of Mn-oxides. After the reaction, the average oxidation state of Mn in the solids was much lower at pH 4 than at pH 6 and 8, suggesting more reduction under more acidic conditions. Even when reacting with phthalate and propanol, which only sorbed to Mn-oxides but did not degrade, there was proton-promoted Mn dissolution under acidic conditions. These results suggest the significance of environmental pH and mineral structures in affecting the Mn-organic interactions and provide fundamental insights into a better understanding of the roles of Mn-oxides in regulating soil C cycling.
| Original language | English |
|---|---|
| Pages (from-to) | 2067-2077 |
| Number of pages | 11 |
| Journal | ACS Earth and Space Chemistry |
| Volume | 8 |
| Issue number | 10 |
| DOIs | |
| State | Published - Oct 17 2024 |
Funding
This work was sponsored by the US Department of Agriculture\u2013National Institute of Food and Agriculture (USDA\u2013NIFA) project phase 02898, and the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory (ORNL), managed by UT-Battelle, LCC for the US Department of Energy (DOE) under contract DE-AC05-00OR22725. The authors would like to acknowledge Xiangping Yin and Geoff Schwaner (ORNL) for assistance with dissolved OC and total solid C analysis. This research used resources at Beamline 12-BM of the Advanced Photon Source, a user facility operated for the US DOE Office of Science by Argonne National Laboratory under contract DE-AC02-06CH11357. This work was performed in part by the Molecular Education, Technology, and Research Innovation Center (METRIC) at NC State University, which is supported by the State of North Carolina. This work was performed in part at the Analytical Instrumentation Facility (AIF) at NC State University, which is supported by the State of North Carolina and the National Science Foundation (award number ECCS-2025064).
| Funders | Funder number |
|---|---|
| Robert H. Lurie Comprehensive Cancer Center | |
| Laboratory Directed Research and Development Program | |
| Oak Ridge National Laboratory | |
| Molecular Education, Technology, and Research Innovation Center | |
| North Carolina State University | |
| Office of Science | |
| U.S. Department of Agriculture | |
| UT-Battelle | |
| METRIC | |
| National Institute of Food and Agriculture | 02898 |
| National Institute of Food and Agriculture | |
| U.S. Department of Energy | DE-AC05-00OR22725 |
| U.S. Department of Energy | |
| Argonne National Laboratory | DE-AC02-06CH11357 |
| Argonne National Laboratory | |
| National Science Foundation | ECCS-2025064 |
| National Science Foundation |
Keywords
- Mn−organic interaction
- mineral structure
- oxidative degradation
- pH effect
- sorption