Effects of methamidophos and glyphosate on copper sorption-desorption behavior in soils

A batch-equilibration technique was employed to study the impact of two organophosphorus pesticides methamidophos (MDP) and glyphosate (GPS) on copper (Cu(2+)) sorption-desorption for phaeozem and burozem collected from Northeastern China. The addition of the two pesticides decreased Cu(2+) sorption, increased Cu(2+) desorption and prolonged the equilibrium time of Cu(2+) sorption-desorption. But GPS appeared to exert a stronger influence on Cu(2+) sorption-desorption due to its stronger complexion with Cu(2+). When MDP was added, Cu(2+) sorption-desorption was linearly correlated with MDP treatment concentrations. But in the presence of GPS, Cu(2+), sorption first underwent a rapid decrease period, and then slowly tended towards a steady period. The reverse pattern could be found for Cu(2+) desorption in the presence of GPS. Without pesticides and with the existence of MDP, Cu(2+) sorption-desorption kinetics was well conformed to two-constant equation and Elovich equation. But that was not the case for Cu(2+) desorption kinetics in the presence of GPS although its sorption could be also described by these two equations.