Adsorption and movement of carbaryl in soils: A verification of cosolvent theory and comparison of batch equilibrium and soil thin layer chromatography results

摘要

Batch equilibrium and soil thin layer chromatography (TLC) techniques were used to investigate the influence of different volume fractions of organic cosolvents (acetone and methanol) on the adsorption and movement of carbaryl in four different types of Indian soils. L-shaped isotherms were obtained for both the cosolvent-water mixtures at all f_s values and were in close agreement with the Freundlich equation. Higher adsorption was observed on F.R.I, soil (FSL) followed by Alampur soil (ASL), Kalai soil (KL), and Bhoran soil (BSL) at all f_s values for both the cosolvent systems as was anticipated from the K and K_D values. The K and K_D values also confirmed that carbaryl adsorption was higher in methanol-water mixture than acetone-water mixture and decreased with increasing f_s values. The frontal R_f values obtained from soil TLC studies were inversely proportional to the K and K_D values for both the cosolvent systems. The higher K and K_D values and lower R_f values in methanol-water mixtures relative to acetone-water mixtures for all the soils indicated that acetone had a greater potential for ground water contamination compared to methanol. The adsorption data were used to evaluate the cosolvent theory for describing adsorption of carbaryl in acetone-water and methanol-water mixtures. The aqueous phase partition coefficients, K_(DW) (mol g~(-1)), normalized with respect f_(oc) for carbaryl was evaluated by extrapolating f_s → 0.