Sorption and desorption of selected phenyl urea herbicides in laboratory water-sediment systems

Abstract

Diuron, isoproturon and linuron were phenyl urea herbicides (PUHs) widely used in the world to control annual weeds. The adsorption-desorption behaviors of these PUHs were investigated in lab-scale water-sediment systems set up with water and sediment samples collected from Taihu Lake, China. 12 h was selected as the equilibrium time for the six sediments. Sorption isotherms of these PUHs were well described by the Freundlich model. The sorption of three PUHs in six sediments were all linear or close to it (0.92≤n≤ 1.06). The logarithms of the normalized distribution coefficient by organic carbon (logK oc) were 2.32 for isoproturon, 2.85 for diuron and 3.02 for linuron. The sorption and desorption potentials of the three PUHs can be arranged in the following order: linuron>diuron>isoproturon. The three PUHs possess moderate to strong sorption affinities to the natural sediments in the drinking water sources in Taihu Lake. Compared to linuron and diuron, the desorption hysteresis of isoproturon is conspicuous with hysteresis indices from 0.657 to 0.872, and the sorption seems to be irreversible.