Components and Particle Size Fractions Involved in Atrazine Adsorption by Soils1

We used two Saskatchewan soils to investigate the relative importance of sesquioxides, organic matter, and a series of particle size fractions in adsorbing atrazine. The DCB (sodium dithionite-citrate-bicarbonate)-extractable Al and Fe are associated with a series of soil particle size fractions ranging from <0.2 to >50 ±m. Besides clay particles, the nonclay fractions of the soils have a significant capacity to retain atrazine. After the organic matter has been destroyed, the removal of sesquioxides by the DCB treatment causes further substantial reduction in the degree of adsorptivity and the rate of adsorption of atrazine by the soils. The data indicate that, besides organic matter, the noncrystalline to poorly crystalline Al and Fe components and other inorganic constituents present in a series of particle size fractions of the soils, especially <20 ±m fractions, provide adsorption sites for atrazine.