Sorption and leaching of diuron on natural and peat-amended calcareous soil from Spain
ABSTRACT The sorption and leaching processes of diuron from a 0.02 M CaCl2 aqueous solution at 25°C, by a calcareous soil from the Southeastern of Spain after organic carbon (OC) amendment with a commercial peat (from 0.18% to 4.61%) have been studied by using batch and soil column experiments. The experimental sorption isotherms may be classified as L type of the Giles classification which suggests, in general, a moderate affinity of the diuron molecules by the active sites of the adsorbents. Nevertheless, according to the slope of the initial portion of these isotherms, the affinity increases as the organic matter content increases. In order to calculate the adsorption capacity (Kf) of the samples for the herbicide diuron, the experimental data point were fitted to the Freundlich equation. The Kf values ranged between 2.17 mg kg−1 for the original soil (containing 0.18% OC) and 34.28 mg kg−1 for the peat-amended sample containing 4.61% OC. The breakthrough curves and distribution of diuron along the soil profile, obtained from the step-function type and pulse type experiments by using the soil column studies, indicate that the amount of diuron retained range from 359.3 mg kg−1 for the column filled with the original soil to 439 mg kg−1 for that filled with the peat-amended soil containing 4.61% OC. The amount of diuron desorbed (373.0 mg kg−1) from the soil containing the higher percentage of organic carbon (4.61%) was greater than that desorbed (300.8 mg kg−1) from the original soil, which might be due to the joining of diuron to the soluble fraction of the organic matter moving through the column.
- Soil Science - SOIL SCI. 01/1948; 66(6):429-446.
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ABSTRACT: Adsorption of cholesterol and 2,2',5,5'-tetrachlorohiphenyl by particles from river water and treated sewage was studied in distilled water, sewage and river water and was compared to adsorption in solutions of organic matter concentrated from sewage and river water by ultrafiltration. Partition coefficients and standard free energies of adsorption are reported. Results indicate that sewage particulate matter is a more effective adsorbent than river particulates. Adsorption from samples of concentrated dissolved organic matter was less efficient than from unconcentrated samples and from distilled water. Chemical equilibrium considerations indicate that this is due either to formation of associations between the study compounds and other dissolved organic matter, thus stabilizing them in the dissolved phase, or to competitive adsorption.Water Research. 01/1982;
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ABSTRACT: Freundlich isotherms were obtained for the adsorption equilibrium of the herbicides metamitron and chloridazon with the components of a representative soil in a pesticide concentration range of 10-1000 γg ml−1 for metamitron and 10-500 μg ml−1 for chloridazon.The mobility of these herbicides through soil columns was also studied using the displacement technique described by Davidson (Soil Sci. Soc. Amer. Proc., 32 (1968) 629). The experiment was carried out simultaneously in three columns, two of which were fed with solutions of the herbicides while the third was used as a control. The herbicide solutions flowed down by gravity and were collected at the outlet at different times. The herbicide content of these outlet solutions was determined by Differential Pulse Polarography.Pesticide Science 04/2006; 32(2):259 - 264.