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Fabris, José Domingos; Filho, M. F. de Jesus; Coey, J. M. D.; Mussel, Wagner da Nova; Goulart, A. T.

doi:10.1023/a:1012619331408

Cited by 28 publications

(8 citation statements)

References 23 publications

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“…However, their role in sequestering the major plant nutrient cations-K, Ca, and Mg-has received less attention from an ecological perspective. These cations can be occluded with Fe phases as a consequence of several mechanisms, including: isomorphous substitution in minerals (McBride 1989;Giovanoli and Cornell 1992;Fabris et al 1997), selective adsorption or co-precipitation (Taylor and Graley 1967;McBride 1978), adsorption following charge screening by anions (Rietra et al 2001). Organic matter occluded within Fe and/or Al phases (Grybos et al 2007;Kleber et al 2015) could also harbor cations on ion exchange sites.…”

Section: Introductionmentioning

confidence: 99%

Iron reduction: a mechanism for dynamic cycling of occluded cations in tropical forest soils?

Hall

Huang

2017

Biogeochemistry

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Nutrient cations can limit plant productivity in highly weathered soils, but have received much less attention than phosphorus and nitrogen. The reduction of iron (Fe) in anaerobic microsites of surface soils can solubilize organic matter and P sorbed or occluded with short-range-ordered (SRO) Fe phases. This mechanism might also release occluded cations. In the Luquillo Experimental Forest, Puerto Rico, we measured cation release during anaerobic laboratory incubations, and assessed patterns of cation availability in surface soils spanning ridge-slope-valley catenas. During anaerobic incubations, potassium (K), calcium (Ca) and magnesium (Mg) significantly increased with reduced Fe (Fe(II)) in both water and 0.5M HCl extractions, but did not change during aerobic incubations. In the field, 0.5M HCl-extractable Fe(II) and Fe(III) were the strongest predictors of K, Mg, and Ca on ridges (R2: 0.57 -0.75). Here, both Ca and Mg decreased with Fe(III), while K, Ca, and Mg increased with Fe(II), consistent with release of Fe-occluded cations following Fe reduction. Manganese in ridge soils was extremely low, consistent with leaching following reductive dissolution of Mn(IV). On slopes, soil C was the strongest cation predictor, consistent with the importance of organic matter for cation exchange in these highly weathered Oxisols. In riparian valleys, cation concentrations were up to 16-fold greater than in other topographic positions but were weakly or unrelated to measured predictors, potentially reflecting cation-rich groundwater. Predictors of cation availability varied with topography, but were consistent with the potential importance of microsite Fe reduction in liberating occluded cations, particularly in the highly productive ridges. This mechanism may explain discrepancies among indices of "available" soil cations and plant cation uptake observed in other tropical forests. CommentsThis is a post-peer-review, pre-copyedit version of an article published in Biogeochemistry. The final authenticated version is available online at: http://dx. AbstractNutrient cations can limit plant productivity in highly weathered soils, but have received much less attention than phosphorus and nitrogen. The reduction of iron (Fe) in anaerobic microsites of surface soils can solubilize organic matter and P sorbed or occluded with short-range-ordered (SRO) Fe phases. This mechanism might also release occluded cations. In the Luquillo Experimental Forest, Puerto Rico, we measured cation release during anaerobic laboratory incubations, and assessed patterns of cation availability in surface soils spanning ridge-slopevalley catenas. During anaerobic incubations, potassium (K), calcium (Ca) and magnesium (Mg) significantly increased with reduced Fe (Fe(II)) in both water and 0.5M HCl extractions, but did not change during aerobic incubations. In the field, 0.5M HCl-extractable Fe(II) and Fe(III) were the strongest predictors of K, Mg, and Ca on ridges (R 2 : 0.57 -0.75). Here, both Ca and Mg decreased with Fe(III), while K, Ca, and Mg i...

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Section: Introductionmentioning

confidence: 99%

Iron reduction: a mechanism for dynamic cycling of occluded cations in tropical forest soils?

Hall

Huang

2017

Biogeochemistry

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“…where 0 represents the tetrahedral site (the A-site), [] stands for the octahedral site (the B-site) and o denotes the cation vacancies [33]. The ferric ions occupy the tetrahedral and octahedral sites in the ratio of 1:1.67.…”

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confidence: 99%

Zero-field and in-field Mössbauer spectroscopy as a tool for structural and magnetic characterization of maghemite (γ-Fe2O3) nanoparticles

Zbořil

2005

Czech J Phys

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“…Element content (mass%) (7) 50.6 (6) Rietveld structural refinement, Table 2) for this ferrite suggests that the isomorphical replacement of Fe 3+ (ionic radium r = 65 pm [29]) by Sn 4+ (r = 69 pm) does occur; any replacement of Fe 2+ (r = 78 pm) by Sn 4+ would tend to a decrease of the cubic lattice, according to Vegard's law [30]. The ionic charge balance can be obtained by replacing 3Sn 4+ for 4Fe 3+ , creating a cation vacancy (⊕).…”

Section: Samplementioning

confidence: 99%

“…The chemical and crystallographic mechanisms by which the oxidation of Fe 2+ to Fe 3+ in magnetite (Fe 3 O 4 ; cubic) leads to hematite (␣-Fe 2 O 3 ; rhombohedral hexagonal) or maghemite (␥-Fe 2 O 3 ; cubic or tetragonal) are not enough clear so far. In natural conditions, purer and well-crystallized bulk magnetite is directly transformed to hematite [1,2], whereas the oxidation of Fe 2+ in the crystalline structure of highly substituted, small-sized grains and less wellcrystallized iron-rich spinels leads first to maghemite prior the final conversion to hematite [3][4][5][6]. The conversion rate of magnetite to hematite seems to be somehow influenced by the climate, which prevailed during the rock weathering on the soil formation process [7].…”

Section: Introductionmentioning

confidence: 99%