title: Stabilization of Natural Organic Matter by Short-Range-Order Iron Hydroxides.
abstract: Dissolved organic matter (DOM) is capable of modifying the surfaces of soil minerals (e.g., Fe hydroxides) or even forming stable co-precipitates with Fe(III) in a neutral environment. The DOM/Fe co-precipitation may alter biogeochemical carbon cycling in soils if the relatively mobile DOM is sorbed by soil minerals against leaching, runoff, and biodegradation. In this study, we aimed to determine the structural development of DOM/Fe co-precipitates in relation to changes in pH and C/(C + Fe) ratios using XRD, XPS, Fe K-edge XAS, FTIR, and C-NEXAFS techniques. The results showed that in the system with bulk C/(C + Fe) molar ratios ≤0.65, the ferrihydrite-like Fe domains were precipitated as the core and covered by the C shells. When the C/(C + Fe) molar ratio ranged between 0.71 and 0.89, the emerging Fe-C bonding suggested a more substantial association between Fe domains including edge- and corner-sharing FeO6octahedra and DOM. With C/(C + Fe) bulk molar ratios ≥0.92, only corner-sharing FeO6octahedra along with Fe-C bonding were found. The homogeneously distributed C and Fe domains caused the enhancement of Fe and C solubilization from co-precipitates. The C/(C + Fe) ratios dominated structural compositions and stabilities of C/Fe co-precipitates and may directly affect the Fe and C cycles in soils.
authors: Department of Soil and Environmental Sciences, National Chung Hsing University , Taichung 40227, Taiwan, R.O.C.
authors: Kai-Yue
authors: KY
authors: Chen
authors: Department of Engineering and System Sciences, National Tsing Hua University , Hsinchu 30043, Taiwan, R.O.C.
authors: Tsan-Yao
authors: TY
authors: Chen
authors: Department of Soil and Environmental Sciences, National Chung Hsing University , Taichung 40227, Taiwan, R.O.C.
authors: Ya-Ting
authors: YT
authors: Chan
authors: Department of Soil and Environmental Sciences, National Chung Hsing University , Taichung 40227, Taiwan, R.O.C.
authors: Ching-Yun
authors: CY
authors: Cheng
authors: Department of Soil and Environmental Sciences, National Chung Hsing University , Taichung 40227, Taiwan, R.O.C.
authors: Yu-Min
authors: YM
authors: Tzou
authors: Department of Soil and Environmental Sciences, National Chung Hsing University , Taichung 40227, Taiwan, R.O.C.
authors: Yu-Ting
authors: YT
authors: Liu
authors: Division of Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo , 332 Building of Environmental Studies, 5-1-5 Kashiwanoha, Kashiwa City, Chiba 277-8563, Japan.
authors: Heng-Yi
authors: HY
authors: Teah
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D006878:Hydroxides / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry; D012987:Soil / Q000737:chemistry
chemical_list: D005290:Ferric Compounds; D006878:Hydroxides; D008903:Minerals; D012987:Soil; D007501:Iron