Effect of Organic matter and Cosolvents (acetone and methanol) on the Movement of Synthetic Pyrethroids in Soils

The effect of organic matter and organic cosolvents (acetone and methanol) on the movement of 3 synthetic pyrethroids (cypermethrin, deltamethrin and fenvalerate) in 3 different types of Indian (sandy loam, loam and silt loam) soils has been studied by using soil thin - layer chromatographic technique. The movement of pyrethroids was expressed in terms of frontal R_f, R_f,·R_B and R_M values. In pure water systems the pyrethroids were strongly hydrophobically adsorbed and gave little movement. Movement of pyrethroids was higher in sandy loam soil followed by loam and silt loam soils. Removal of organic matter from the soils increased the movement of pyrethroids. Similarly, with the increase of volume fractions of both the organic cosolvents (acetone and methanol); the movement increased. The variation in movemet of pyrethroids in soils has been discussed on the basis of their solubilities in water and cosolvents, polarity, adsorption and solute - solvent interactions.