Sorption – desorption of imidacloprid insecticide on Indian soils of five different locations

摘要

Sorption - desorption processes govern the movement of all chemicals including pesticides in soils. The present investigation was undertaken to study the sorp tion - desorption of imidacloprid, using a batch method, on soils of five different location of India. Sorption data were fitted to Freundlich isotherm. The log K value was the highest for loam typ e soil (1.830) and the lowest for clay type soil (1.661). The value of 1 was the maximum for silt loam soil (0.909 ) but minimum for loam soil (0.723). Simple correlation analysis indicated that among soil properties on ly electrical conductivity showed a higher but marginally non - significant negative correlation with log K (r = - 0.826) indicating that higher concentrat ion of solutes solutes are conducive to low sorption capacity of soil. The desorption data conformed to two surfaces Freundlich desorption isotherm. The values of 1 1 ' corresponding to easily desorbed fraction of imidacloprid showed significant negative c orrelation with soil pH (r = - 0.886, significant at p ≤0.05) but significant positive correlation with clay content (r = 0.980, significant at p ≤0.01). The desorption index for easily desorbed fraction of imidacloprid (n 1 ') also had significant negative correlation with soil pH (r = 0.953, significant at p ≤0.05). From cumulative desorption data, it appeared that bioavailability of imidacloprid would be lower in neutral soil than acidic or alkaline soils.