Sorption and leaching of atrazine and MCPA in natural and peat-amended calcareous soils from Spain

The sorption and leaching of atrazine and MCPA (0.02 M CaCl2 aqueous solution at 25 degrees C) by a calcareous soil from Southeastern Spain, after organic carbon (OC) amendment with a commercial peat (from 0.18% to 4.61% OC), were studied in batch and soil column experiments. Adsorption capacity (K-f) values, obtained by fitting the experimental data to the Freundlich equation, ranged from 0.24 mg kg(-1) for MCPA sorption on the original soil to 5.37 mg kg(-1) for atrazine sorption on the peat-amended soil containing 4.61% OC. The breakthrough curves obtained from the step-function soil column experiments indicated thatl the amount of herbicide adsorbed ranged from 17.5 mg kg(-1)for MCPA in the original soil to 331 mg kg(-1) for atrazine in the peat-amended soil containing 1.67% OC. The results obtained from the pulse experiments indicate that the mobility of MCPA is much greater than that corresponding to atrazine.