The Movement of Chloride and Nitrate through Certain Iowa Soils

Miscible displacement experiments were conducted to determine the influence of soil type on the movement of chloride and nitrate. The movement of NO - is important in plant nutrition; Cl-, in soil salinity. In these experiments, 100 ml of an aqueous solution containing 0.55 g of CaC12 and 0.35 g of Ca(NO3)24H2O was displaced through 30-cm long soil columns with 0.01N CaSO4. Breakthrough curves, plots of the chloride or nitrate concentrations found in the effluent against the volume of effluent collected, were made. Breakthrough curves from columns of Webster, Ida, and Edina surface soils and a muck soil indicated that the velocity of chloride was greater than that of nitrate during displacement through these soils. On the other hand, breakthrough curves obtained from columns of Webster, Ida, Edina, and Clarion subsoils showed no separation of chloride and nitrate. The breakthrough curves for all soils studied differed in shape. The dispersion coefficient for chloride, calculated from the breakthrough curves, varied from 1.533 cm2/hr for the muck soil to 0.094 cm2/hr for the Ida, C horizon, soil. The experimentally determined dispersion coefficients were used to calculate theoretical chloride distributions for the muck, Ida, and Webster soils