Influence of Soil Solution Salinity on Molybdenum Adsorption by Soils

Molybdenum (Mo) adsorption on five arid-zone soils from California was investigated as a function of equilibrium Solution Mo concentration (0 30 mg L-1), solution pH (4-8), and electrical conductivity (EC = 0.3 or 8 dS m (1)). Molybdenum adsorption decreased with increasing pH. An adsorption maximum was found near pit 4. Molybdenum adsorption as a function Of solution pH was independent of solution salinity from pH 4 to 8. Molybdenum adsorption for five soils as a function Of Solution Mo concentration conformed to the Langmuir adsorption isotherm equation. The Mo adsorption maxima obtained with the Langmuir equation for both ECs were not statistically significantly different it the 95% level of confidence, with the exception of one soil. The constant capacitance model, a surface complexation model, was able to describe Mo adsorption as a function of solution Mo concentration and solution pit. Molybdenum adsorption was predicted using the soil chemical properties: cation exchange capacity, organic carbon content, inorganic carbon content, and iron oxide content, These results are advantageous, its they indicate that, under agricultural conditions (pit 4-8), Mo adsorption call usually be described without consideration of changes ill Soil solution salinity.