To quantify the effect of the interaction of non-residual fractions[Fe oxides(Fe), Mn oxide(Mn), organic materials(OMs)] in the surficial sediments and the natural surface coating samples on the adsorption of atrazine(AT), an AT multiple regression adsorption model(AT-MRAM) was developed. The AT-MRAM improves upon the previous AT additional adsorption model(AT-AAM) with superior goodness-of-fit test(adjusted R2=ca.1.000), F-test and t-test(P<0.01), and reveals the effect of the interaction among the components in the surficial sediments(SSs) and na- tural surface coatings samples(NSCSs) on the adsorption of AT, which was neglected by the AT-AAM. Meanwhile, the AT-MRAM was also verified through adsorption experiments of AT and the relative deviation between predicted maximum adsorption of AT and the experimental one is less than 15%. The resulted information shows that Mn is prone to interact with other non-residual components, the total maximum adsorption of AT is inversly proportional to the level of Mn, and Fe and OMs facilitate the adsorption of AT. The results also indicate that the adsorption of AT is not only dominated by Fe, OMs, Fe/OMs, but also restrained by Fe/Mn, Fe/Mn/OMs, with lesser roles attributed to Mn, and the estimated AT distributions among the components do not agree with that previously predicted by the AT-AAM, especially with the relative contribution of Mn to the adsorption of AT, revealing significant contribution of the interactions among non-residual components in controlling the behavior of AT in aquatic environments.
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.
