1. The Iron Cycle Fe+2 Fe+3 Plants Common ferrous minerals
Magnetite Fe3O4
Pyrite FeS2
Hydrolysis products
FeOH+, Fe(OH)20
Common ferric minerals
Iron hydroxide Fe(OH)3
Goethite FeOOH
Hematite Fe2O3
Jarosite KFe3(SO4)2(OH)6
The Iron Cycle
Fe+2
Thiobacillus ferrooxidans
(strict acidophile)
Gallionella ferroginea
Leptrothrix ochracea
Shewenella putrefaciens
Fe+3 in Solution
pH m/l
pH m/l
Fe+2 in Solution
pH m/l
Soil Solution
Fe+3
Weathering
Exists in solution as
Fe+2 pH<6.75
FeOH+ pH>6.75
Fe+2 chelates
Fe(OH)2+(predominant)
Fe+3 chelates
Oxidation
Reduction
Precipitation
Plant exudates
Plant residue
Plant uptake
as Fe+2 form
Plants
Iron exists in plants as components of
proteins
enzymes
cells