1. Molybdenum Cycle Soil Solution Availability
Increases with increasing pH and soil moisture
Soil Solution
Dominant Species : MoO42-, HMoO4-, H2MoO40
pH > 4 : MoO42-, HMoO4-
pH < 4 : H2MoO4, MoO22+
Plant uptake:
Nitrate Reductase (NO3- to NO2-),
Fixation of N2 by Nitrogenase
Mass flow or diffusion
MoO42-
Crop removal
Coal combustion
Sewage sludge
Man
Animals
(Toxicity in forage at levels > 5 ppm)
Mining
Steel industry
Plant residue
Organic matter
Mo Fertilizers:
Na2MoO4 (39%)
(NH4)2Mo2O7 (54%)
MoO3 (66%)
MoS2 (60%)
Parent Material
Igneous rocks-
Feldspar and ferromagnesian
minerals-
Sedimentary rocks
Precipitated forms:
Fe2(MoO4)3
PbMoO4
CaMoO4
Adsorption:
Fe and Al oxides at low pH
weathering
dissolution
precip.
mineralization
immobilization
Molybdenum Cycle