sorption behaviour of atrazine onto natural sediments under various solution conditions

Potentiometric titrations, XRD analysis and batch adsorption experiments were conducted under various solution chemistry conditions to study the uptake of atrazine (AT) from sediment/water suspensions. A constant capacitance surface complexation model was then applied to interpret the reaction mechanism at the aqueous sediment surfaces. The results obtained showed that the sediment sample was negatively charged over a large range of pH values, with the model calculations matching well with the experimental results. Increasing pH value and low ionic strength, as well as high solid concentrations, led to a decrease in the adsorption of AT. The existence of dissolved organic matter (DOM) in the sediment/water system also influenced the uptake of AT by the sediment. A large increase in AT adsorption occurred for sediment pre-incubated with DOM, with a decrease in AT uptake occurring when herbicide was pre-incubated with DOM. In addition, the results suggested that long aliphatic chains must play an important role in the pesticide interaction with DOM fractions.