Co-contamination of atrazine(AT) and cadmium(Cd) on the surficial sediments(SSs) and natural suface coating samples(NSCSs) was investigated via thermodynamic adsorption experiments. The results show that surface coatings have a stronger ability to adsorb AT owing to their higher active components compared with surficial sediments. Synergetic and antagonistic effects of Cd on the adsorption of AT were observed. Cd at a lower concentra- tion(≤4.0 mg/L) in the solid/liquid phase enhanced AT adsorption onto the surficial sediments(surface coatings), while the adsorption of AT would be inhibited at a Cd concentration of more than 8.0 mg/L: AT coordinates strongly to Cd, and AT-Cd complexes seem to be more strongly adsorbed on sediments than AT alone, and at the adsorption of AT can take place on the sites where Cd has been previously adsorbed and Cd acts as a bridge for the interaction between sediments and AT. With the increase of Cd concentration, the superfluous Cd may hold much more adsorption sites and thus inhibits the adsorption of AT. Meanwhile, the effects of co-existed AT on Cd adsorption on SSs(NSCSs) were insignificant since Cd has a stronger competitive ability to be absorbed on SSs(NSCSs). The present study could be useful in predicting interactions of the metal ions with herbicides and potentially aid the design of remediation strategies for contaminated sediments and groundwater.
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