Extractability of 2,4-D, dicamba and MCPP from soil

The adsorption of herbicides on soil colloids is a major factor determining their mobility, persistence, and activity in soils. Solvent extraction cou ld be a viable option for removing sorbed contaminants in soils. This study evaluated the extractability of three herbicides: 2,4 dichlorophenoxy-acet ic acid (2,4-D), 4-chloro-2-methylphenoxypropanoic acid (mecoprop acid or M CPP), and 3,6-dichloro-2-methoxybenzoic acid (dicamba). Three solvents (wat er, methanol, and iso-propanol) and three methods of extraction (column, ba tch, and soxhlet) were compared for their efficiencies in removing the herb icides from three soils (loamy sand, silt loam, and silty clay). Both linea r and non-linear Freundlich isotherms were used to predict sorption intensi ty of herbicides on soils subjected to various extraction methods and condi tions. High K-d and K(f)r, and low N values were obtained for all herbicide s in silty clay soil by batch extraction. Methanol was the best solvent rem oving approximately 97% of all added herbicides from the loamy sand either by column or soxhlet extraction method. Isopropanol ranked second by removi ng over 90% of all herbicides by soxhelet extraction from all three soils. However, water was ineffective in removing herbicides from any of the soils using any of the three extracting procedures used in this study. In genera l, the extent of herbicide removal depended on soil type, herbicide concent ration, extraction procedure, solvent type and amount, and extraction time.