The movement of some herbicides in soils. Linear diffusion and convection of chemicals in soils.

H The movement of some chemicals in soils has been treated theoretically by considering for saturated conditions, the chemical diffusion coefficient, the percolation velocity of the water, the sorbtive properties of the soil, the average particle size of the soil, and the fractional number of sorbing sites. A model has been developed for the movement of chemical in saturated soil, based on Fick’s law, conservation of energy, and a sorption isotherm. ‘Theoretical curves for two different boundary conditions are given for realistic values of the water velocity in the pores and the measured diffusion coefficient.