Abstract: Behaviors of soil heavy metals are often affected by coexisting
herbicides due to their physical and chemical interaction. Effect of
glyphosate, an herbicide containing -PO_3^{2-} and
-COOH groups, on cadmium adsorption in montmorillonite was studied in detail.
The results showed that cadmium adsorption quantity in montmorillonite
increased with increasing soil solution pH and cadmium concentration as usual,
but decreased with glyphosate, which is due to the formation of a low affinity
complex of Cd and glyphosate and decreasing solution pH induced by glyphosate
addition. When the equilibrium solution pH was below 6.7, glyphosate has little
effect on cadmium adsorption, but when the equilibrium solution pH was above
6.7, glyphosate significantly decreased cadmium adsorption quantity in
montmorillonite. In addition, the adding order of Cd and glyphosate also
influenced Cd adsorption quantity in montmorillonite.
