Effects of Ionic Strength and Temperature on Adsorption of Atrazine, Deethylatrazine and Deisopropyatrazine in an Alkaline Sandy Loam

Atrazine is an agricultural herbicide used in large quantities and consequently companied with its two degradation products, deethylatrazine (DEA), and deisopropylatrazine (DIA), are commonly detected in groundwater and surface water. The retention of these compounds in vadose zone is highly related to their adsorption to soils. Laboratory studies were conducted to determine the sorption behaviour of atrazine, DEA, and DIA on a sandy loamy soil using the batch equilibration technique. The effects ionic strength (adjusted by CaCl2 concentration) and temperature (25±1°C and 40±1°C) of absorption were also investigated. The adsorption isotherms of all three chemicals conformed to the Freundlich equation. Adsorption coefficients decreased in the order atrazine > DIA > DEA, and our calculated organic carbon normalized partition coefficients were 46.76, 46.00, 30.78 L/kg respectively. For atrazine and DEA, there existed a salting-out effect, their adsorption increased as ionic strength increased from 0 to 0.1 mol/L CaCl2, but for DIA, its maximum adsorption occurred in 0.01 mo/ L CaCl2 solution. The adsorption experiment also showed that more effective adsorption of atrazine, DEA and DIA at a lower temperature.