Effect of Soil Physicochemical Properties on Adsorption of Tricyclazole

Many processes affect the behavior of pesticides in the environment, namely adsorption, transfer, breakdown and degradation. Adsorptiondesorption are a dynamic process in which molecules are continually transferred between the bulk liquid and solid surface. Adsorptiondesorption of pesticides in soils depend upon various factors like soil pH, CEC, clay content, organic matter and metal oxides. Tricyclazole (5-methyl-1,2,4-triazolo[3,4-b]benzothiazole), a systemic fungicide, used to control the rice blast in paddy cultivated in India. Adsorption studies were conducted in three soils having varied physicochemical properties. The pH of the soils varied from 5.3, 8.1 and 8.5 in alfisol of Raipur, inceptisol of Delhi and inceptisol of Karnal, respectively. The adsorption studies were carried out in triplicate at initial concentrations of 5,10,15,20 and 25 μg/mL of tricyclazole. All the concentrations were below the solubility of pesticide in water. The adsorption studies were carried out at 1:5 ratios of soil and water. The samples were analyzed by HPLC fitted with Rp-18 column and PDA detector at  max 230 nm. The lowest adsorption of tricyclazole occured in Karnal soil (46.78-33.98 %), and highest adsorption occurred in Raipur soil (61.92-50.26%). Kfads (Freundich ) values of tricyclazole were 9.68, 7.92 and 6.18 mL/g in Raipur, Delhi and Karnal soil, respectively. Tricyclazole is strongly adsorbed in Raipur soil as compared to soils of other regions as indicated by the highest Kfads value. The corresponding Kd values for the adsorption process were 6.61, 5.08 and 3.67mL/g, for Raipur, Delhi and Karnal, respectively. The results revealed that adsorption is influenced by soil physicochemical properties, and showed that the maximum adsorption of pesticide was observed in soils with higher organic carbon, clay content and low soil pH. Naveen Kumar et al 392