214
Trace Elements in Abiotic and Biotic Environments
TABLE 28.1

Molybdenum Contents in Soils, Water, and Air (mg/kg)

Environmental Compartment
Range/Maximum
Soil (mg/kg)
Light sandy
0.1–3.7
Medium loamy
0.4–6.4
Heavy loamy
0.7–7.2
Calcerous (calcisols)
0.3–7.4
Organic (histosols)
0.3–7.4
Water (μg/L)
Rain
0.01–2.6
River
0.04–1.3
Sea
1.6–6.3
Air (ng/m 3 )
Industrial regions
1.0–10.0
Remote regions
<0.2
Sources: Data are given for uncontaminated environments, from various
sources, mainly: Kabata-Pendias, A. and Mukherjee, A.B., Trace
Elements from Soil to Human, Springer, Berlin, Germany, 2007;
Reimann, C. and de Caritat, P., Chemical Elements in the Environment, Springer, Berlin, Germany, 1998.
hydroxides of Al, Fe, and Mn. Especially Mn concretions have a great capacity to fix
Mo, up to above 400 mg/kg (Kabata-Pendias and Sadurski 2004). Behavior of Mo
in soils is highly dependent on pH and Eh conditions, and thus is very variable. The
mobility and availability of Mo to plants is highly governed by soil pH and drainage
conditions. In acidic soils (pH < 5.5), and especially in those with a high Fe oxide
levels, Mo is hardly available to plants, whereas from wet alkaline soils, it is most
easily taken up by plants. The low phytoavailability of Mo, which sometimes occurs
in peat soils, is affected by the strong fixation of Mo by humic acid, and possibly by
other OM. The highest proportion of Mo, up to about 50% of its content, is fixed by
various OM compounds. Water soluble fraction of Mo is about 4%, and residual fraction, about 15% of its total contents.
Liming of acid soils is a common practice to increase Mo availability to plants.
However, at higher rate of liming, Mo mobility may decrease due to its adsorption by
CaCO 3 . Increased Mo phytoavailability should be controlled, as its elevated contents
in fodder are not good for animals. Soils with high amounts of Mo, mainly ferrasols, and other soils in arid and semiarid regions, should be ameliorated to decrease
Mo contents in plants. The application of S compounds is most effective, whereas
increased P level in soils may stimulate Mo uptake by plants. Some Mo compounds
(e.g., Na 2 MoO 4 ) may be used as addition in fertilizers.